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Sample records for dusk

  1. Composition measurements in the dusk flank magnetosphere

    Science.gov (United States)

    Fuselier, S. A.; Elphic, R. C.; Gosling, J. T.

    1999-03-01

    The dusk flank magnetosphere exhibits significant structure. Several regions have been identified, including the plasma sheet, mantle, and low latitude boundary layer. Transitions from one region to the next, for example from the mantle to the plasma sheet, can be abrupt or indistinct. In addition, the density within the flank mantle can range over several orders of magnitude. Although there is significant structure in this region of the magnetosphere, individual regions often can be distinguished by their energy spectra and ion composition. ISEE Fast Plasma Experiment and Plasma Composition Experiment data are used to examine the composition of the mantle and to study a set of transitions from the mantle to the plasma sheet where plasmas with mantle-like and plasma sheet-like energies mix. This study indicates that the variability of the mantle density is largely due to variability in the solar wind component (H+ and He2+); the ionospheric plasma (O+) density is roughly constant. Similarly, the plasma with mantle-like energy found in the mixed region is largely of solar wind origin.

  2. The dawn and dusk electrojet response to substorm onset

    Directory of Open Access Journals (Sweden)

    E. Borälv

    Full Text Available We have investigated the time delay between substorm onset and related reactions in the dawn and dusk ionospheric electrojets, clearly separated from the nightside located substorm current wedge by several hours in MLT. We looked for substorm onsets occurring over Greenland, where the onset was identified by a LANL satellite and DMI magnetometers located on Greenland. With this setup the MARIA magnetometer network was located at dusk, monitoring the eastward electrojet, and the IMAGE chain at dawn, for the westward jet. In the first few minutes following substorm onset, sudden enhancements of the electrojets were identified by looking for rapid changes in magnetograms. These results show that the speed of information transfer between the region of onset and the dawn and dusk ionosphere is very high. A number of events where the reaction seemed to preceed the onset were explained by either unfavorable instrument locations, preventing proper onset timing, or by the inner magnetosphere's reaction to the Earthward fast flows from the near-Earth neutral line model. Case studies with ionospheric coherent (SuperDARN and incoherent (EISCAT radars have been performed to see whether a convection-induced electric field or enhanced conductivity is the main agent for the reactions in the electrojets. The results indicate an imposed electric field enhancement.

    Key words: Ionosphere (auroral ionosphere; electric fields and currents - Magnetospheric physics (storms and substorms

  3. Simulation of the dawn-dusk magnetosheath asymmetry under quasi-steady states

    Institute of Scientific and Technical Information of China (English)

    GUO Jiuling; LIU Zhenxing

    2005-01-01

    The dawn-dusk asymmetry of the magnetosheath under quasi-steady states has been studied by using a newly developed 3D MHD magnetosphere simulation model. The results show that the dawn-dusk asymmetry is substantial because of the Parker spiral IMF. It is found that the dawn-dusk magnetosheath thickness asymmetry is the effect of different shock conditions. The plasma density and flux asymmetry are mainly caused by the different thickness of the dawn-dusk magnetosheath, and the magnetic reconnection on the magnetopause has no significant effects. It is also showed that the Plasma Depletion Layer in front of the dayside magnetopause can cause duskward plasma flow, and the total plasma flux on the dusk side will be higher.

  4. Dawn-dusk asymmetry in the Kelvin-Helmholtz instability at Mercury.

    Science.gov (United States)

    Paral, Jan; Rankin, Robert

    2013-01-01

    The NASA MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft entered orbital phase around Mercury on 18 March 2011. A surprising consistent feature in the data returned is large-scale vortices that form exclusively on the dusk side of the magnetosphere. Here we present global kinetic hybrid simulations that explain these observations. It is shown that vortices are excited by a Kelvin-Helmholtz instability near the subsolar point, which grows convectively along the dusk-side magnetopause. Virtual time series along a track approximating a flyby of the MESSENGER show correspondence with the satellite data; the data contain sawtooth oscillations in plasma density, flow and magnetic field, and exhibit the observed dawn-dusk asymmetry. It is shown that asymmetry between dawn and dusk at Mercury is controlled by the finite gyroradius of ions and by convection electric fields. Mercury's magnetosphere offers a natural laboratory for studying plasma regimes not present in other planetary magnetospheres or the laboratory.

  5. Natural entrainment without dawn and dusk : The case of the European ground squirrel (Spermophilus citellus)

    NARCIS (Netherlands)

    Hut, RA; van Oort, BEH; Daan, S; Oort, Bob E.H. van

    Observational data collected in the field and in enclosures show that diurnal, burrow-dwelling European ground squirrels (Spermophilus citellus) never were above ground during twilight at dawn or at dusk. The animals emerged on average 4.02 h (SD = 0.45) after civil twilight at dawn and retreated in

  6. Dawn-dusk asymmetries in rotating magnetospheres: Lessons from modeling Saturn

    Science.gov (United States)

    Jia, Xianzhe; Kivelson, Margaret G.

    2016-02-01

    Spacecraft measurements reveal perplexing dawn-dusk asymmetries of field and plasma properties in the magnetospheres of Saturn and Jupiter. Here we describe a previously unrecognized source of dawn-dusk asymmetry in a rapidly rotating magnetosphere. We analyze two magnetohydrodynamic simulations, focusing on how flows along and across the field vary with local time in Saturn's dayside magnetosphere. As plasma rotates from dawn to noon on a dipolarizing flux tube, it flows away from the equator along the flux tube at roughly half of the sound speed (Cs), the maximum speed at which a bulk plasma can flow along a flux tube into a lower pressure region. As plasma rotates from noon to dusk on a stretching flux tube, the field-aligned component of its centripetal acceleration decreases and it flows back toward the equator at speeds typically smaller than 1/2 Cs. Correspondingly, the plasma sheet remains far thicker and the field less stretched in the afternoon than in the morning. Different radial force balance in the morning and afternoon sectors produce asymmetry in the plasma sheet thickness and a net dusk-to-dawn flow inside of L = 15 or equivalently, a large-scale electric field (E) oriented from postnoon to premidnight, as reported from observations. Morning-afternoon asymmetry analogous to that found at Saturn has been observed at Jupiter, and a noon-midnight component of E cannot be ruled out.

  7. Natural entrainment without dawn and dusk : The case of the European ground squirrel (Spermophilus citellus)

    NARCIS (Netherlands)

    Hut, RA; van Oort, BEH; Daan, S; Oort, Bob E.H. van

    1999-01-01

    Observational data collected in the field and in enclosures show that diurnal, burrow-dwelling European ground squirrels (Spermophilus citellus) never were above ground during twilight at dawn or at dusk. The animals emerged on average 4.02 h (SD = 0.45) after civil twilight at dawn and retreated in

  8. Ionospheric characteristics of the dusk-side branch of the two-cell aurora

    Directory of Open Access Journals (Sweden)

    J.-H. Shue

    2006-03-01

    Full Text Available The two-cell aurora is characterized by azimuthally elongated regions of enhanced auroral brightness over extended local times in the dawn and dusk sectors. Its association with the convection, particle precipitation, and field-aligned currents under various phases of substorms has not been fully understood. With Polar Ultraviolet Imager auroral images in conjunction with Defense Meteorological Satellite Program (DMSP F12 spacecraft on the dusk-side branch of the two-cell aurora, we are able to investigate an association of the auroral emissions with the electric fields, field-aligned currents, and energy flux of electrons. Results show that the substorm expansion onset does not significantly change the orientation of the dusk-side branch of the two-cell aurora. Also, the orientation of the magnetic deflection vector produced by the region 1 field-aligned current changed from 73±1° to the DMSP trajectory during the substorm growth phase, to 44±6° to the DMSP trajectory during the substorm expansion phase. With a comparison between the orientation of the dusk-side branch of the two-cell aurora and the orientation of the magnetic deflection vector, it is found that the angular difference between the two orientations is 28±5° during the substorm growth phase, and 13±6° during the substorm expansion phase.

  9. Dawn-dusk asymmetry in ionospheric return flows: relationship between flows and Birkeland currents

    Science.gov (United States)

    Larson, R.; Anderson, B. J.; Korth, H.; Bodurtha, K. E.; Wilson, G.

    2008-12-01

    Intense duskside ionospheric flows occurring equatorward of the discrete auroral precipitation zone have been attributed to large electric fields resulting from partial ring current injections. In this picture the driver is the ion injection that feeds the Region 2 currents which in turn cause the electric field. Alternatively, one may take the view that the return flow at dusk is favored energetically by the coupled magnetosphere-ionosphere system. In this energetics view, the upward Region 2 at dawn corresponds to discrete aurora and enhanced conductance on closed field lines on the dawn side, whereas the downward Region 2 at dusk does not contribute as substantially to enhancing the duskside conductance. The energy dissipation associated with a given flow is proportional to the conductance. Thus, it is energetically more favorable for the coupled system to send more return flow to the dayside at dusk than at dawn. In this paper we assess whether there is a persistent dawn dusk asymmetry in the return flow relative to the Birkeland current location and intensity. Birkeland currents derived from the Iridium Satellite constellation, augmented with DMSP F13 magnetic field data are used to place DMSP F13 drift meter data in the context of both the global and local Birkeland currents. Using events from the Iridium stable currents database of Anderson et al. (2008), we identified 59 events with high quality drift observations during southward IMF. The events are divided into two ranges of IMF intensity and five IMF clock angle bins. We order the data in latitude relative to the peak Region 1 current density. There is a persistent suppression of the dawn return flows relative to those at dusk regardless of IMF By or IMF intensity. This result indicates that the return flow predominantly occurs through the evening closed field line region, consistent with the above energetics picture of return flow in the coupled system.

  10. The far-ultraviolet main auroral emission at Jupiter. Pt. 1. Dawn-dusk brightness asymmetries

    Energy Technology Data Exchange (ETDEWEB)

    Bonfond, B.; Gustin, J.; Gerard, J.C.; Grodent, D.; Radioti, A. [Liege Univ. (Belgium). Lab. de Physique Atmospherique et Planetaire; Palmaerts, B. [Liege Univ. (Belgium). Lab. de Physique Atmospherique et Planetaire; Max-Planck-Institut fuer Sonnensystemforschung, Goettingen (Germany); Badman, S.V. [Lancaster Univ. (United Kingdom). Dept. of Physics; Khurana, K.K. [California Univ., Los Angeles, CA (United States); Tao, C. [Institut de Recherche en Astrophysique et Planetologie, Toulouse (France)

    2015-07-01

    The main auroral emission at Jupiter generally appears as a quasi-closed curtain centered around the magnetic pole. This auroral feature, which accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range, is related to corotation enforcement currents in the middle magnetosphere. Early models for these currents assumed axisymmetry, but significant local time variability is obvious on any image of the Jovian aurorae. Here we use far-UV images from the Hubble Space Telescope to further characterize these variations on a statistical basis. We show that the dusk side sector is ∝ 3 times brighter than the dawn side in the southern hemisphere and ∝ 1:1 brighter in the northern hemisphere, where the magnetic anomaly complicates the interpretation of the measurements.We suggest that such an asymmetry between the dawn and the dusk sectors could be the result of a partial ring current in the nightside magnetosphere.

  11. Geotail observations of temperature anisotropy of the two-component protons in the dusk plasma sheet

    Directory of Open Access Journals (Sweden)

    M. N. Nishino

    2007-03-01

    Full Text Available In search for clues towards the understanding of the cold plasma sheet formation under northward IMF, we study the temperature anisotropy of the two-component protons in the plasma sheet near the dusk low-latitude boundary observed by the Geotail spacecraft. The two-component protons result from mixing of the cold component from the solar wind and the hot component of the magnetospheric origin, and may be the most eloquent evidence for the transport process across the magnetopause. The cold component occasionally has a strong anisotropy in the dusk flank, and the sense of the anisotropy depends on the observed locations: the parallel temperature is enhanced in the tail flank while the perpendicular temperature is enhanced on the dayside. The hot component is nearly isotropic in the tail while the perpendicular temperature is enhanced on the dayside. We discuss possible mechanism that can lead to the observed temperature anisotropies.

  12. Light pollution alters the phenology of dawn and dusk singing in common European songbirds

    Science.gov (United States)

    Da Silva, Arnaud; Valcu, Mihai; Kempenaers, Bart

    2015-01-01

    Artificial night lighting is expanding globally, but its ecological consequences remain little understood. Animals often use changes in day length as a cue to time seasonal behaviour. Artificial night lighting may influence the perception of day length, and may thus affect both circadian and circannual rhythms. Over a 3.5 month period, from winter to breeding, we recorded daily singing activity of six common songbird species in 12 woodland sites, half of which were affected by street lighting. We previously reported on analyses suggesting that artificial night lighting affects the daily timing of singing in five species. The main aim of this study was to investigate whether the presence of artificial night lighting is also associated with the seasonal occurrence of dawn and dusk singing. We found that in four species dawn and dusk singing developed earlier in the year at sites exposed to light pollution. We also examined the effects of weather conditions and found that rain and low temperatures negatively affected the occurrence of dawn and dusk singing. Our results support the hypothesis that artificial night lighting alters natural seasonal rhythms, independently of other effects of urbanization. The fitness consequences of the observed changes in seasonal timing of behaviour remain unknown. PMID:25780238

  13. First detection of global dawn-dusk ionospheric current intensities using Ampere's integral law on Orsted orbits

    DEFF Research Database (Denmark)

    Stauning, P.; Primdahl, Fritz

    2000-01-01

    The magnetic measurements by the Orsted satellite in noon-midnight orbits have enabled the derivation of the global dawn-dusk oriented ionospheric currents from an Ampere's law closed loop line integral of the geomagnetic vector field along the satellite track. The globally integrated dawn......-to-dusk ionospheric current is found to be proportional to the gee-effective solar wind electric field and is around 1 million ampere for a typical solar wind electric field of 2 mV/m. Dividing the Ampere integral into semi-orbit parts has enabled us to show that the hemispherical total current intensities depend...

  14. Dawn-dusk asymmetry in particles of solar wind origin within the magnetosphere

    Directory of Open Access Journals (Sweden)

    T. J. Stubbs

    Full Text Available Solar wind/magnetosheath plasma in the magnetosphere can be identified using a component that has a higher charge state, lower density and, at least soon after their entry into the magnetosphere, lower energy than plasma from a terrestrial source. We survey here observations taken over 3 years of He2+ ions made by the Magnetospheric Ion Composition Sensor (MICS of the Charge and Mass Magnetospheric Ion Composition Experiment (CAMMICE instrument aboard POLAR. The occurrence probability of these solar wind ions is then plotted as a function of Magnetic Local Time (MLT and invariant latitude (7 for various energy ranges. For all energies observed by MICS (1.8–21.4 keV and all solar wind conditions, the occurrence probabilities peaked around the cusp region and along the dawn flank. The solar wind conditions were filtered to see if this dawnward asymmetry is controlled by the Svalgaard-Mansurov effect (and so depends on the BY component of the interplanetary magnetic field, IMF or by Fermi acceleration of He2+ at the bow shock (and so depends on the IMF ratio BX /BY . It is shown that the asymmetry remained persistently on the dawn flank, suggesting it was not due to effects associated with direct entry into the magnetosphere. This asymmetry, with enhanced fluxes on the dawn flank, persisted for lower energy ions (below a "cross-over" energy of about 23 keV but reversed sense to give higher fluxes on the dusk flank at higher energies. This can be explained by the competing effects of gradient/curvature drifts and the convection electric field on ions that are convecting sunward on re-closed field lines. The lower-energy He2+ ions E × B drift dawnwards as they move earthward, whereas the higher energy ions curvature/ gradient drift towards dusk. The convection electric field in the tail is weaker for

  15. Reconciling the Dawn-Dusk Asymmetry in Mercury’s Exosphere with the Micrometeoroid Impact Directionality

    Science.gov (United States)

    Pokorný, Petr; Sarantos, Menelaos; Janches, Diego

    2017-06-01

    Combining dynamical models of dust from Jupiter-family comets and Halley-type comets, we demonstrate that the seasonal variation of the dust/meteoroid environment at Mercury is responsible for producing the dawn-dusk asymmetry in Mercury’s exosphere observed by the MESSENGER spacecraft. Our latest models, calibrated recently from ground-based and space-borne measurements, provide unprecedented statistics that enable us to study the longitudinal and latitudinal distribution of meteoroids impacting Mercury’s surface. We predict that the micrometeoroid impact vaporization source is expected to undergo significant motion on Mercury’s surface toward the nightside during Mercury’s approach to aphelion and toward the dayside when the planet is approaching the Sun.

  16. Dawn and Dusk Set States of the Circadian Oscillator in Sprouting Barley (Hordeum vulgare Seedlings.

    Directory of Open Access Journals (Sweden)

    Weiwei Deng

    Full Text Available The plant circadian clock is an internal timekeeper that coordinates biological processes with daily changes in the external environment. The transcript levels of clock genes, which oscillate to control circadian outputs, were examined during early seedling development in barley (Hordeum vulgare, a model for temperate cereal crops. Oscillations of clock gene transcript levels do not occur in barley seedlings grown in darkness or constant light but were observed with day-night cycles. A dark-to-light transition influenced transcript levels of some clock genes but triggered only weak oscillations of gene expression, whereas a light-to-dark transition triggered robust oscillations. Single light pulses of 6, 12 or 18 hours induced robust oscillations. The light-to-dark transition was the primary determinant of the timing of subsequent peaks of clock gene expression. After the light-to-dark transition the timing of peak transcript levels of clock gene also varied depending on the length of the preceding light pulse. Thus, a single photoperiod can trigger initiation of photoperiod-dependent circadian rhythms in barley seedlings. Photoperiod-specific rhythms of clock gene expression were observed in two week old barley plants. Changing the timing of dusk altered clock gene expression patterns within a single day, showing that alteration of circadian oscillator behaviour is amongst the most rapid molecular responses to changing photoperiod in barley. A barley EARLY FLOWERING3 mutant, which exhibits rapid photoperiod-insensitive flowering behaviour, does not establish clock rhythms in response to a single photoperiod. The data presented show that dawn and dusk cues are important signals for setting the state of the circadian oscillator during early development of barley and that the circadian oscillator of barley exhibits photoperiod-dependent oscillation states.

  17. Dusk to dawn activity patterns of anopheline mosquitoes in West Timor and Java, Indonesia.

    Science.gov (United States)

    Ndoen, Ermi; Wild, Clyde; Dale, Pat; Sipe, Neil; Dale, Mike

    2011-05-01

    Malaria is a serious health issue in Indonesia. We investigated the dusk to dawn anopheline mosquito activity patterns, host-seeking and resting locations in coastal plain, hilly and highland areas in West Timor and Java. Adult mosquitoes were captured landing on humans or resting in houses or animal barns. Data analyzed were: mosquito night-time activities; period of peak activity; night-time activity in specific periods of time and for mosquito resting locations. Eleven species were recorded; data were sparse for some species therefore detailed analyses were performed for four species only. In Java Anopheles vagus was common, with a bimodal pattern of high activity. In West Timor, its activity peaked around midnight. Other species with peak activity around the middle of the night were An. barbirostris and An. subpictus. Most species showed no biting and resting preference for indoors or outdoors, although An. barbirostris preferred indoors in West Timor, but outdoors in Java. An. aconitus and An. annularis preferred resting in human dwellings; An. subpictus and An. vagus preferred resting in animal barns. An. barbirostris preferred resting in human dwellings in West Timor and in animal barns in Java. The information is useful for planning the mosquito control aspect of malaria management. For example, where mosquito species have peak activity at night indoors, bednets and indoor residual spraying should reduce malaria risk, but where mosquitoes are most active outdoors, other options may be more effective.

  18. A DE-1/whistler study of the thermal plasma structure and dynamics in the dusk bulge sector of the magnetosphere

    Science.gov (United States)

    Carpenter, D. L.

    1992-01-01

    The objective of this research was to obtain new understanding of the thermal plasma structure and dynamics of the plasmasphere bulge region of the magnetosphere, with special emphasis on the erosion process that results in a reduction in plasmasphere size and on the manner in which erosion leads to the presence of patches of dense plasma in the middle and outer afternoon-dusk magnetosphere. Case studies involving data from the DE 1, GEOS 2, and ISEE 1 satellites and from ground whistler stations Siple, Halley, and Kerguelen were used. A copy of the published paper entitled 'A case study of plasma structure in the dusk sector associated with enhanced magnetospheric convection,' is included.

  19. Hall effect control of magnetotail dawn-dusk asymmetry: A three-dimensional global hybrid simulation

    Science.gov (United States)

    Lu, San; Lin, Y.; Angelopoulos, V.; Artemyev, A. V.; Pritchett, P. L.; Lu, Quanming; Wang, X. Y.

    2016-12-01

    Magnetotail reconnection and related phenomena (e.g., flux ropes, dipolarizing flux bundles, flow bursts, and particle injections) occur more frequently on the duskside than on the dawnside. Because this asymmetry can directly result in dawn-dusk asymmetric space weather effects, uncovering its physical origin is important for better understanding, modeling, and prediction of the space weather phenomena. However, the cause of this pervasive asymmetry is unclear. Using three-dimensional global hybrid simulations, we demonstrate that the Hall physics in the magnetotail current sheet is responsible for the asymmetry. The current sheet thins progressively under enhanced global convection; when its thickness reaches ion kinetic scales, some ions are decoupled from the magnetized electrons (the Hall effect). The resultant Hall electric field Ez is directed toward the neutral plane. The Hall effect is stronger (grows faster) on the duskside; i.e., more ions become unmagnetized there and do not comove with the magnetized dawnward Ez × Bx drifting electrons, thus creating a larger additional cross-tail current intensity jy (in addition to the diamagnetic current) on the duskside, compared to the dawnside. The stronger Hall effect strength on the duskside is controlled by the higher ion temperature, thinner current sheet, and smaller normal magnetic field Bz there. These asymmetric current sheet properties are in turn controlled by two competing processes that correspond to the Hall effect: (1) the dawnward E × B drift of the magnetic flux and magnetized ions and electrons and (2) the transient motion of the unmagnetized ions which do not execute E × B drift.

  20. A statistical study into the spatial distribution and dawn‐dusk asymmetry of dayside magnetosheath ion temperatures as a function of upstream solar wind conditions

    National Research Council Canada - National Science Library

    Dimmock, A. P; Nykyri, K; Karimabadi, H; Osmane, A; Pulkkinen, T. I

    2015-01-01

    ... and nonisotropic and differs between the dawn and dusk flanks. The present study attempts to study the spatial distribution of magnetosheath ion temperature as a function of upstream solar wind conditions...

  1. Dawn-dusk asymmetries and sub-Alfvénic flow in the high and low latitude magnetosheath

    Directory of Open Access Journals (Sweden)

    M. Longmore

    2005-11-01

    Full Text Available We present the results of a statistical survey of the magnetosheath using four years of Cluster orbital coverage. Moments of the plasma distribution obtained from the electron and ion instruments together with magnetic field data are used to characterise the flow and density in the magnetosheath. We note two important differences between our survey and the gasdynamic model predictions: a deceleration of the flow at higher latitudes close to the magnetopause, resulting in sub-Alfvénic flow near the cusp, and a dawn-dusk asymmetry with higher velocity magnitudes and lower densities measured on the dusk side of the magnetosheath in the Northern Hemisphere. The latter observation is in agreement with studies carried out by Paularena et al. (2001, Němeček et al. (2000, and Šafránková et al. (2004. In equations of hydrodynamics for a single-component additon to this we observe a reverse of this asymmetry for the Southern Hemisphere. High-latitude sub-Alfvénic flow is thought to be a necessary condition for steady state reconnection pole-ward of the cusp.

  2. Observations of Kelvin-Helmholtz Waves Along the Dusk-Side Boundary of Mercury's Magnetosphere During MESSENGER's Third Flyby

    Science.gov (United States)

    Boardsen, Scott A.; Sundberg, Torgjoern; Slavin, James A.; Anderson, Brian J.; Korth, Haje; Solomon, Sean C.; Blomberg, Lars G.

    2010-01-01

    During the third MESSENGER flyby of Mercury on 29 September 2009, 15 crossings of the dusk-side magnetopause were observed in the magnetic field data over a 2-min period, during which the spacecraft traveled a distance of 0.2 R(sub M) (where R(sub M) is Mercury's radius). The quasi-periodic nature of the magnetic field variations during the crossings, the characteristic time separations of approx.16 s between pairs of crossings, and the variations of the magnetopause normal directions indicate that the signals are likely the signature of surface waves highly steepened at their leading edge that arose from the Kelvin-Helmholtz instability. At Earth, the Kelvin- Helmholtz instability is believed to lead to the turbulent transport of solar wind plasma into Earth's plasma sheet. This solar wind entry mechanism could also be important at Mercury. Citation: Boardsen, S. A., T. Sundberg, J. A.Slavin, B. J. Anderson, H. Korth, S. C. Solomon, and L. G. Blomberg (2010), Observations of Kelvin-Helmholtz waves along the dusk-side boundary of Mercury s magnetosphere during MESSENGER's third flyby,

  3. The global distribution of the dusk-to-nighttime enhancement of summer NmF2 at solar minimum

    Science.gov (United States)

    Chen, Yiding; Liu, Libo; Le, Huijun; Wan, Weixing; Zhang, Hui

    2016-08-01

    In this paper, the dusk-to-nighttime enhancement (DNE) of summer NmF2 was investigated based on Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation observations at solar minimum. The global distributions of the magnitude and the peak time of the DNE as well as the role of the DNE in NmF2 diurnal cycle were presented. The DNE mainly exists in three regions (one in the Southern Hemisphere and two in the Northern Hemisphere), and its distribution is related to geomagnetic configuration, especially in the Southern Hemisphere. For most DNEs, their peaks correspond to the maxima of NmF2 diurnal cycle. The DNEs are much more prominent in the southern than in the northern summer hemisphere; they last to later nighttime hours, have larger magnitudes, and play more important roles in NmF2 diurnal cycle in the southern than in the northern summer hemisphere. The distribution of the DNE was analyzed in terms of photoionization and the vertical plasma drift induced by neutral winds. The positive geomagnetic declinations and the smaller geomagnetic inclinations at higher geographic latitudes over the South Pacific are crucial for the prominent DNEs in the southern summer hemisphere; they result in larger upward plasma drift at higher latitudes where photoionization is still significant at sunset and evening hours.

  4. 防霾口罩呼吸阻力的研究%Study on Anti -dusk Masks Respiratory Resistance

    Institute of Scientific and Technical Information of China (English)

    刘秋新; 童亮; 陈芬; 蔡美元; 向金童; 吴炯

    2016-01-01

    通过对8种常用类型防霾口罩的实验测试,采用回归曲线分析方法得出了防霾口罩呼吸阻力随使用时间的变化函数形式,同时也通过实验数据统计给出了各种类型口罩的建议使用时长,建议N90和N95无纺布防霾口罩在空气轻度污染下使用时长不超过11~12 h ,中度污染下不超过8~10 h;而棉布为面料的N95口罩在轻度污染下使用时长不超过7 h ,中度污染下不超过6 h。%Based on the experimental tests for 8 types of commonly used anti-dusk masks ,the anti-dust mask respiratory resistance function form with the change of time is obtained through the regression curve analysis method ,and at the same time the experiment data statistics shows the recommended duration of use of the various types of masks .It suggests that non-woven masks N90 and N95 is used not more than 11~12 hours under mild air pollution and 8~10 hours under moderate pollution ;respirator use time of cotton fabrics N95 doesn’t exeed 7 hours under light pollution and 6 hours under moderate pollution .

  5. Organic Light-Emitting Diode with Color Tunable between Bluish-White Daylight and Orange-White Dusk Hue

    Directory of Open Access Journals (Sweden)

    Shih-Yun Liao

    2014-01-01

    Full Text Available The varying color of sunlight diurnally exhibits an important effect on circadian rhythm of living organisms. The bluish-white daylight that is suitable for work shows a color temperature as high as 9,000 K, while the homey orange-white dusk hue is as low as 2,000 K. We demonstrate in this report the feasibility of using organic light-emitting diode (OLED technology to fabricate sunlight-style illumination with a very wide color temperature range. The color temperature can be tuned from 2,300 K to 9,300 K, for example, by changing the applied voltage from 3 to 11 V for the device composing red and yellow emitters in the first emissive layer and blue emitter in the second. Unlike the prior arts, the color-temperature span can be made much wider without any additional carrier modulation layer, which should enable a more cost effective fabrication. For example, the color-temperature span is 7,000 K for the above case, while it is 1,700 K upon the incorporation of a nanoscale hole modulation layer in between the two emissive layers. The reason why the present device can effectively regulate the shifting of recombination zone is because the first emissive layer itself possesses an effective hole modulation barrier of 0.2 eV. This also explains why the incorporation of an extra hole modulation layer with a 0.7 eV barrier did not help extend the desirable color-temperature span since excessive holes may be blocked.

  6. M-I coupling across the auroral oval at dusk and midnight: repetitive substorm activity driven by interplanetary coronal mass ejections (CMEs)

    Science.gov (United States)

    Sandholt, P. E.; Farrugia, C. J.; Denig, W. F.

    2014-04-01

    We study substorms from two perspectives, i.e., magnetosphere-ionosphere coupling across the auroral oval at dusk and at midnight magnetic local times. By this approach we monitor the activations/expansions of basic elements of the substorm current system (Bostrøm type I centered at midnight and Bostrøm type II maximizing at dawn and dusk) during the evolution of the substorm activity. Emphasis is placed on the R1 and R2 types of field-aligned current (FAC) coupling across the Harang reversal at dusk. We distinguish between two distinct activity levels in the substorm expansion phase, i.e., an initial transient phase and a persistent phase. These activities/phases are discussed in relation to polar cap convection which is continuously monitored by the polar cap north (PCN) index. The substorm activity we selected occurred during a long interval of continuously strong solar wind forcing at the interplanetary coronal mass ejection passage on 18 August 2003. The advantage of our scientific approach lies in the combination of (i) continuous ground observations of the ionospheric signatures within wide latitude ranges across the auroral oval at dusk and midnight by meridian chain magnetometer data, (ii) "snapshot" satellite (DMSP F13) observations of FAC/precipitation/ion drift profiles, and (iii) observations of current disruption/near-Earth magnetic field dipolarizations at geostationary altitude. Under the prevailing fortunate circumstances we are able to discriminate between the roles of the dayside and nightside sources of polar cap convection. For the nightside source we distinguish between the roles of inductive and potential electric fields in the two substages of the substorm expansion phase. According to our estimates the observed dipolarization rate (δ Bz/δt) and the inferred large spatial scales (in radial and azimuthal dimensions) of the dipolarization process in these strong substorm expansions may lead to 50-100 kV enhancements of the cross

  7. M-I coupling across the auroral oval at dusk and midnight. Repetitive substorm activity driven by interplanetary coronal mass ejections (CMEs)

    Energy Technology Data Exchange (ETDEWEB)

    Sandholt, P.E. [Oslo Univ. (Norway). Dept. of Physics; Farrugia, C.J. [New Hampshire Univ., Durham (United Kingdom). Space Science Center; Denig, W.F. [NOAA, Boulder, CO (United States)

    2014-07-01

    We study substorms from two perspectives, i.e., magnetosphere-ionosphere coupling across the auroral oval at dusk and at midnight magnetic local times. By this approach we monitor the activations/expansions of basic elements of the substorm current system (Bostroem type I centered at midnight and Bostroem type II maximizing at dawn and dusk) during the evolution of the substorm activity. Emphasis is placed on the R1 and R2 types of field-aligned current (FAC) coupling across the Harang reversal at dusk. We distinguish between two distinct activity levels in the substorm expansion phase, i.e., an initial transient phase and a persistent phase. These activities/phases are discussed in relation to polar cap convection which is continuously monitored by the polar cap north (PCN) index. The substorm activity we selected occurred during a long interval of continuously strong solar wind forcing at the interplanetary coronal mass ejection passage on 18 August 2003. The advantage of our scientific approach lies in the combination of (i) continuous ground observations of the ionospheric signatures within wide latitude ranges across the auroral oval at dusk and midnight by meridian chain magnetometer data, (ii) 'snapshot' satellite (DMSP F13) observations of FAC/precipitation/ion drift profiles, and (iii) observations of current disruption/near-Earth magnetic field dipolarizations at geostationary altitude. Under the prevailing fortunate circumstances we are able to discriminate between the roles of the dayside and nightside sources of polar cap convection. For the nightside source we distinguish between the roles of inductive and potential electric fields in the two substages of the substorm expansion phase. According to our estimates the observed dipolarization rate (δB{sub z}/δt) and the inferred large spatial scales (in radial and azimuthal dimensions) of the dipolarization process in these strong substorm expansions may lead to 50-100 kV enhancements of the

  8. Effect of exogenous melatonin and extending the dark period at dusk before the summer solstice on the onset of oestrus in Romney Marsh ewes.

    Science.gov (United States)

    Guerin, M V; Napier, A J; Matthews, C D

    1994-05-01

    Groups of Romney Marsh ewes (n = 24) were injected with exogenous melatonin or subjected to extended darkness or a combination of both at dusk from the winter to the summer solstice before being re-exposed to the natural photoperiod at 35 degrees S. The animals were at all times exposed to natural dawn. The onset of subsequent oestrus was delayed when compared with controls subjected to the natural photoperiod. Either melatonin or darkness or a combination were equally effective at delaying oestrus. The results are consistent with a hypothesis based on an external coincidence model of seasonal breeding involving the coincidence of a light-sensitive phase set close to dusk that, when exposed to light in spring and summer, prepares the reproductive axis to respond correctly to the direct effects of the inductive photoperoid in autumn. The offset of the time of oestrus was not affected by the experimental treatments nor was the timing of the subsequent reproductive season. Since melatonin was as effective as darkness at influencing the assumed photosensitive signal, even in the presence of natural light, melatonin may act through the light reception system.

  9. Low-Frequency Wave Activity Detected by MMS during Dusk Magnetopause Crossings and its Relation to Heating and Acceleration of Particles

    Science.gov (United States)

    Le Contel, O.; Roux, A.; Retino, A.; Mirioni, L.; Sahraoui, F.; Chust, T.; Berthomier, M.; Chasapis, A.; Aunai, N.; Leroy, P.; Alison, D.; Lavraud, B.; Lindqvist, P. A.; Khotyaintsev, Y. V.; Vaivads, A.; Marklund, G. T.; Burch, J. L.; Torbert, R. B.; Moore, T.; Ergun, R. E.; Needell, J.; Chutter, M.; Rau, D.; Dors, I.; Macri, J.; Russell, C. T.; Magnes, W.; Strangeway, R. J.; Bromund, K. R.; Plaschke, F.; Fischer, D.; Leinweber, H. K.; Anderson, B. J.; Nakamura, R.; Argall, M. R.; Le, G.; Slavin, J. A.; Kepko, L.; Baumjohann, W.; Pollock, C. J.; Mauk, B.; Fuselier, S. A.; Goodrich, K.; Wilder, F. D.

    2015-12-01

    Since the 9th of July, the MMS fleet of four satellites have evolved into a tetrahedral configuration with an average inter-satellite distance of 160 km and an apogee of 12 earth radii on the dusk side. In this study we report on ultra-low (1 mHz to ~10 Hz) and very-low (10 Hz to ~ 4 kHz) frequency wave activity measured by the four satellites during several crossings of the dusk equatorial magnetopause. Since the Larmor radius of magnetosheath protons is of the order of 50 km, this inter-satellite distance allows us to investigate in detail the physics of the magnetopause at proton scales including current structures related to Kelvin-Helmholtz instability as well as other energy transfer processes. From wave polarization analysis, we characterize the different types of emissions and discuss different mechanisms of heating and acceleration of particles. In particular, we focus on the electron heating by kinetic Alfvén waves and lower hybrid waves and the electron acceleration by oblique whistler mode waves, which have been suggested as possible mechanisms from previous Cluster and THEMIS measurements.

  10. Geotail Observations of the Spatial Dependence of Kelvin-Helmholtz Waves on an Inbound Passage through the Dusk Flank Boundary Layer

    Science.gov (United States)

    Fairfield, D. H.; Farrugia, C. J.; Gratton, F. T.; Mukai, T.; Nagai, T.

    2005-01-01

    On August 1, 1998, the Geotail spacecraft made an inbound passage perpendicular to the dusk magnetopause at the dusk terminator when the interplanetary magnetic field had been very northward for more than 10 hours. Typical 3-minute-period Kelvin-Helmholtz waves were observed and the density in the boundary layer and magnetopause was observed to have an unusually high value near 5 /cc. Compressible MHD calculations using the measured values at Geotail yield substantial growth rates that support the idea that the magnetopause was Kelvin-Helmholtz unstable. In contrast to many previous events where a spacecraft remained in the boundary layer, this passage allowed study of how the waves varied with distance inward from the magnetopause. In a layer adjacent to the magnetosheath, rapid magnetic field fluctuations were seen with variations of at least 50 nT/s. Initially the boundary waves led to transitions between the magnetosheath and the fluctuating region with magnetosheath-like densities and tailward velocities, but as the spacecraft moved inward, the transitions were more likely to be between the fluctuating region and a hotter region with magnetosphere-like densities of 5kc. Gradually the velocity perturbations began to exhibit 360 degree rotations. Such rotations are similar to the vortices seen earlier by the ISEE spacecraft throughout the magnetotail which were suspected of being caused by Kelvin-Helmholtz instability of the boundary.

  11. Solar eclipse. The rise and 'dusk' of the Dutch PV innovation system

    Energy Technology Data Exchange (ETDEWEB)

    Negro, S.O.; Hekkert, M.P. [Department of Innovation Studies, Copernicus Institute for Sustainable Development and Innovation, Utrecht University, Heidelberglaan 2, 3584 CS Utrecht (Netherlands); Vasseur, V. [International Centre for Integrated Assessment and Sustainable Development, University Maastricht, P.O. Box 616, 6200 MD Maastricht (Netherlands); Van Sark, W.G.J.H.M. [Department of Science, Technology and Society, Copernicus Institute for Sustainable Development and Innovation, Utrecht University, Heidelberglaan 2, 3584 CS Utrecht (Netherlands)

    2012-07-01

    In this paper, we take the theoretical perspective of innovation system dynamics and apply this to Photovoltaic (PV) solar energy technology in the Netherlands. The history of the development of the PV innovation system is analysed in terms of seven key processes that are essential for the build-up of innovation systems. We show that large fluctuations are present in the processes related to guidance of the search and market formation. Surprisingly, entrepreneurial activities are not too much affected by fluctuating market formation activities. We relate this to market formation in neighbouring countries and discuss the implications for policy making.

  12. Solar Eclipse: The rise and "dusk" of the Dutch PV Innovation System

    NARCIS (Netherlands)

    Negro, S.O.; Vasseur, V.; Sark, W.G.J.H.M. van; Hekkert, M.P.

    2012-01-01

    In this paper, we take the theoretical perspective of innovation system dynamics and apply this to Photovoltaic (PV) solar energy technology in the Netherlands. The history of the development of the PV innovation system is analysed in terms of seven key processes that are essential for the build-up

  13. Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues?

    NARCIS (Netherlands)

    A.M. Dokter; S. Akesson; H. Beekhuis; W. Bouten; L.S. Buurma; H. van Gasteren; I. Holleman

    2013-01-01

    Common swifts are specialist flyers spending most of their life aloft, including night-time periods when this species roosts on the wing. Nocturnal roosting is preceded by a vertical ascent in twilight conditions towards altitudes of up to 2.5 km, behaviour previously explained as flight altitude se

  14. From dusk till dawn: nocturnal and diurnal pollination in the epiphyte Tillandsia heterophylla (Bromeliaceae).

    Science.gov (United States)

    Aguilar-Rodríguez, P A; Krömer, T; García-Franco, J G; MacSwiney G, M C

    2016-01-01

    In order to compare the effectiveness of diurnal and nocturnal pollinators, we studied the reproductive biology and pollinators of Tillandsia heterophylla E. Morren, an epiphytic tank bromeliad endemic to southeastern Mexico. Since anthesis in T. heterophylla is predominantly nocturnal but lasts until the following day, we hypothesised that this bromeliad would receive visits from both diurnal and nocturnal visitors, but that nocturnal visitors would be the most effective pollinators, since they arrive first to the receptive flower, and that bats would be the most frequent nocturnal visitors, given the characteristics of the nectar. Flowering of T. heterophylla began in May and lasted until July. The species is fully self-compatible, with an anthesis that lasts for ca. 15-16 h. Mean volume of nectar produced per flower was 82.21 μl, with a mean sugar concentration of 6.33%. The highest volume and concentration of nectar were found at 20:00 h, with a subsequent decline in both to almost zero over the following 12-h period. T. heterophylla has a generalist pollination system, since at least four different morphospecies of visitors pollinate its flowers: bats, moths, hummingbirds and bees. Most of the pollinating visits corresponded to bats and took place in the early evening, when stigma receptivity had already begun; making bats the probable pollinator on most occasions. However, diurnal pollinators may be important as a 'fail-safe' system by which to guarantee the pollination of T. heterophylla.

  15. Circadian entrainment by different daylengths : The roles of dawn and dusk

    NARCIS (Netherlands)

    Daan, S.; Comas, M.; Spoelstra, K.; Hut, R.; Beersma, D.

    2009-01-01

    In the early days of circadian rhythms research there were two competing views on entrainment by light: through parametric action on the velocity of the endogenous cycle (Aschoff) versus non-parametric discrete phase shifts elicited by the lights-on and –off transitions (Pittendrigh). Although the

  16. Polarisation and propagation of lion roars in the dusk side magnetosheath

    Directory of Open Access Journals (Sweden)

    M. Maksimovic

    Full Text Available We present observations of "lion roars" obtained in the magnetosheath by the Spectrum Analyser (SA of the Spatio-Temporal Analysis of Field Fluctuations (STAFF experiment aboard Cluster. STAFF-SA calculates, in near real time, the complete auto- and cross-spectral matrix derived from three magnetic and two electric components of the electromagnetic field at 27 frequencies in the range of 8 Hz to 4 kHz. This allows the study of the properties of whistler mode waves and more particularly, the properties of "lion roars", which are intense, short-duration, narrow-banded packets of whistler waves. Their presence is favoured by the magnetic field troughs associated with mirror mode structures. During two short periods of well-defined mirror modes, we study the depth δB/B of the magnetic troughs, and the direction of propagation of the lion roars. During the first period, close to the magnetopause, deep magnetic troughs pass the satellites. Lion roars are then observed to propagate simultaneously in two directions, roughly parallel and anti-parallel to the magnetic field: this probably indicates that during this period, the satellites were within the successive source regions of lion roars. For the second period, far from the magnetopause, the magnetic troughs are less deep. Lion roars are propagating in only one direction, roughly anti-parallel to the magnetic field, suggesting that the source regions are more distant and predominantly on one side of the satellites.

    Key words. Magnetospheric physics (magnetosheath; plasma waves and instabilities Radio science (radiowave propagation

  17. The owl of Minerva from dusk till dawn, or, two shades of gray

    Directory of Open Access Journals (Sweden)

    Dolar Mladen

    2015-01-01

    Full Text Available The paper takes as its starting point the figure of the owl as the emblem of philosophy, it looks at its history and takes up its most significant philosophical use, the notorious passage where Hegel uses the owl as the indication of philosophy’s necessary belatedness. This is the passage which is usually taken as the point of indictment of Hegel’s position and the role he ascribed to philosophy. Hegel’s adage ‘What is rational is actual, and what is actual is rational’ is scrutinized in its various aspects, particularly in view of its other version, ‘what is rational must happen’. The tension between the ‘is’ and the ‘ought’ is perhaps the clue to understanding this adage, where Hegel doesn’t opt for the one or the other, but aims at the paradoxical intersection of the two. Hegel’s adage is put in contrast with Marx’s Thesis Eleven. The paper considers the concepts of the rational, the actual, the belatedness/retroaction, the grayness and finally the owl (and the part that bestiary plays in philosophy, thus trying to circumscribe the task that should be assigned to philosophy.

  18. Application of satellite remote sensing for mapping wind erosion risk and dusk emission-deposition in Inner Mongolia grassland, China

    NARCIS (Netherlands)

    Reiche, M.; Funk, R.; Zhang, Z.; Hoffmann, C.; Reiche, J.; Wehrhan, M.; Li, Y.; Sommer, M.

    2012-01-01

    Intensive grazing leads to land degradation and desertification of grassland ecosystems followed by serious environmental and social problems. The Xilingol steppe grassland in Inner Mongolia, China, which has been a sink area for dust for centuries, is strongly affected by the negative effects of ov

  19. Du crépuscule à l’aube From dusk to dawn: Finding compromises in nurses’ night shifts

    Directory of Open Access Journals (Sweden)

    Cathy Toupin

    2009-07-01

    Full Text Available Parmi les caractéristiques du travail susceptibles d’influencer les processus de régulation en lien avec l’âge et l’expérience, les questions d’horaires sont peu abordées. Nous pensons cependant qu’une composante importante, dans la construction et la mobilisation de l’expérience, s’élabore en relation avec le type d’horaire. L’objectif de cette recherche est de caractériser, au travers d’une étude menée auprès d’infirmières d’un service de pneumologie français, les stratégies mises en œuvre par les personnels de nuit ; et de proposer une approche dynamique de l’articulation entre horaires et activité de travail, en repérant comment cette articulation s’est forgée au cours du parcours professionnel avec l’expérience, comment ce processus est « lisible » dans l’activité d’aujourd’hui. Les infirmières se « prescrivent » des buts d’actions, élaborent une acception nocturne de leur tâche compte tenu de l’état des patients (par exemple, but visant à respecter le sommeil des patients, à apaiser leurs angoisses, de l’environnement désert des services (par exemple, but visant à consolider sa connaissance de l’état des patients, et de leur état psychophysiologique (par exemple, but visant à maintenir la vigilance. L’expérience du travail de nuit va leur permettre, d’une part de reconnaître ces buts, et d’identifier les contradictions pouvant en émerger ; d’autre part de compenser les difficultés et perturbations provoquées par ces tensions, via l’élaboration de compromis.Among the work characteristics that are likely to influence age and experience related adjustment processes, the issue of work schedules remains largely unexplored. We believe however that work schedules or shifts play an important part in building and mobilizing experience. This paper aims at characterizing the specific strategies implemented by night shift personnel based on a study conducted with nurses in a hospital department of pulmonary diseases. It also suggests a dynamic approach regarding the links between work shifts and the work activity, pointing out how such links evolve over the course of a career as a result of experience, and how such a process is “visible” in their activity at present. Nurses in the pulmonary disease department “assign” themselves goals; they devise a “night interpretation” of their task, taking into account the condition of their patients (goals aimed at protecting their sleep and calming their anxiety, the absence of health care staff resulting in a deserted environment (goals aimed at ensuring they are always well informed on the state of each patient, and their own psycho-physiological state (goal aimed at remaining alert. Their experience of night work allows them, on the one hand to recognize the aims of such actions, and identify the contradictions that may arise from them; and on the other hand to compensate for the difficulties and disturbances caused by such “tensions” by finding ways to compromise.

  20. Intensity asymmetries in the dusk sector of the poleward auroral oval due to IMF $\\mathit{B}_{x}$

    CERN Document Server

    Reistad, J P; Laundal, K M; Haaland, S; Tenfjord, P; Snekvik, K; Oksavik, K; Milan, S E

    2016-01-01

    In the exploration of global-scale features of the Earth's aurora, little attention has been given to the radial component of the Interplanetary Magnetic Field (IMF). This study investigates the global auroral response in both hemispheres when the IMF is southward and lies in the $\\textit{xz}$ plane. We present a statistical study of the average auroral response in the 12-24 magnetic local time (MLT) sector to an $\\textit{x}$ component in the IMF. Maps of auroral intensity in both hemispheres for two IMF $\\mathit{B}_{x}$ dominated conditions($ \\pm $ IMF $\\mathit{B}_{x}$) are shown during periods of negative IMF $\\mathit{B}_{z}$, small IMF $\\mathit{B}_{y}$, and local winter. This is obtained by using global imaging from the Wideband Imaging Camera on the IMAGE satellite. The analysis indicates a significant asymmetry between the two IMF $\\mathit{B}_{x}$ dominated conditions in both hemispheres. In the Northern Hemisphere the aurora is brighter in the 15-19 MLT region during negative IMF $\\mathit{B}_{x}$. In th...

  1. Vertical migration and dispersion of sprat ( Sprattus sprattus ) and herring ( Clupea harengus ) schools at dusk in the Baltic Sea

    DEFF Research Database (Denmark)

    Nilsson, Lars Anders Fredrik; Thygesen, Uffe Høgsbro; Lundgren, Bo;

    2003-01-01

    , and that the dissolution of schools can be modelled by diffusion, i.e. active repulsion is not required. The field measurements were obtained during 3 days in March at one location in the Baltic Sea and included continuous hydroacoustical monitoring, trawl samples, and hydrographical CTD data. Echogram patterns were...... threshold, that schools initiate their dissolution when ambient light intensity drops below this critical threshold, and that fish subsequently swim in an uncorrelated random walk pattern....

  2. Like the Clouds at Dusk. The Swedish Chaplain and the Search for the Atlantises of the Mediterranean: Sardinia

    Directory of Open Access Journals (Sweden)

    Alfonso Stiglitz

    2017-09-01

    Full Text Available Con la scoperta dell’America il racconto platonico di Atlantide diventa oggetto di innumerevoli studi. A partire dal XVIII secolo alcuni studiosi collocano Atlantide nel Mediterraneo. All’interno di questo filone occupa uno spazio non secondario l’isola di Sardegna. Questo lavoro sintetizza il processo di identificazione di Atlantide con l’isola sarda.

  3. Policies of inclusion: immigrants, disease, dependency, and American immigration policy at the dawn and dusk of the 20th century.

    Science.gov (United States)

    Fairchild, Amy L

    2004-04-01

    The racial politics of immigration have punctuated national discussions about immigration at different periods in US history, particularly when concerns about losing an American way of life or American population have coincided with concerns about infectious diseases. Nevertheless, the main theme running through American immigration policy is one of inclusion. The United States has historically been a nation reliant on immigrant labor and, accordingly, the most consequential public policies regarding immigration have responded to disease and its economic burdens by seeking to control the behavior of immigrants within our borders rather than excluding immigrants at our borders.

  4. Artificial night lighting rather than traffic noise affects the daily timing of dawn and dusk singing in common European songbirds

    NARCIS (Netherlands)

    Da Silva, Arnaud; Samplonius, Jelmer Menno; Schlicht, Emmi; Valcu, Mihai; Kempenaers, Bart

    2014-01-01

    It is well established that artificial night lighting can influence animal orientation, but there is less information about its effects on other behaviors. Previous work suggested that light pollution can affect both seasonal and daily patterns of behavior. The aim of our study was to investigate

  5. Melatonin Signal Transduction Pathways Require E-Box-Mediated Transcription of Per1 and Per2 to Reset the SCN Clock at Dusk

    Science.gov (United States)

    Kandalepas, Patty C.; Mitchell, Jennifer W.; Gillette, Martha U.

    2016-01-01

    Melatonin is released from the pineal gland into the circulatory system at night in the absence of light, acting as “hormone of darkness” to the brain and body. Melatonin also can regulate circadian phasing of the suprachiasmatic nucleus (SCN). During the day-to-night transition, melatonin exposure advances intrinsic SCN neural activity rhythms via the melatonin type-2 (MT2) receptor and downstream activation of protein kinase C (PKC). The effects of melatonin on SCN phasing have not been linked to daily changes in the expression of core genes that constitute the molecular framework of the circadian clock. Using real-time RT-PCR, we found that melatonin induces an increase in the expression of two clock genes, Period 1 (Per1) and Period 2 (Per2). This effect occurs at CT 10, when melatonin advances SCN phase, but not at CT 6, when it does not. Using anti-sense oligodeoxynucleotides (α ODNs) to Per 1 and Per 2, as well as to E-box enhancer sequences in the promoters of these genes, we show that their specific induction is necessary for the phase-altering effects of melatonin on SCN neural activity rhythms in the rat. These effects of melatonin on Per1 and Per2 were mediated by PKC. This is unlike day-active non-photic signals that reset the SCN clock by non-PCK signal transduction mechanisms and by decreasing Per1 expression. Rather, this finding extends roles for Per1 and Per2, which are critical to photic phase-resetting, to a nonphotic zeitgeber, melatonin, and suggest that the regulation of these clock gene transcripts is required for clock resetting by diverse regulatory cues. PMID:27362940

  6. Melatonin Signal Transduction Pathways Require E-Box-Mediated Transcription of Per1 and Per2 to Reset the SCN Clock at Dusk.

    Directory of Open Access Journals (Sweden)

    Patty C Kandalepas

    Full Text Available Melatonin is released from the pineal gland into the circulatory system at night in the absence of light, acting as "hormone of darkness" to the brain and body. Melatonin also can regulate circadian phasing of the suprachiasmatic nucleus (SCN. During the day-to-night transition, melatonin exposure advances intrinsic SCN neural activity rhythms via the melatonin type-2 (MT2 receptor and downstream activation of protein kinase C (PKC. The effects of melatonin on SCN phasing have not been linked to daily changes in the expression of core genes that constitute the molecular framework of the circadian clock. Using real-time RT-PCR, we found that melatonin induces an increase in the expression of two clock genes, Period 1 (Per1 and Period 2 (Per2. This effect occurs at CT 10, when melatonin advances SCN phase, but not at CT 6, when it does not. Using anti-sense oligodeoxynucleotides (α ODNs to Per 1 and Per 2, as well as to E-box enhancer sequences in the promoters of these genes, we show that their specific induction is necessary for the phase-altering effects of melatonin on SCN neural activity rhythms in the rat. These effects of melatonin on Per1 and Per2 were mediated by PKC. This is unlike day-active non-photic signals that reset the SCN clock by non-PCK signal transduction mechanisms and by decreasing Per1 expression. Rather, this finding extends roles for Per1 and Per2, which are critical to photic phase-resetting, to a nonphotic zeitgeber, melatonin, and suggest that the regulation of these clock gene transcripts is required for clock resetting by diverse regulatory cues.

  7. Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

    Directory of Open Access Journals (Sweden)

    R. Sridharan

    Full Text Available The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N, India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii significant increase in h' F immediately following the eclipse and (iii distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.

    Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities

  8. Quantitative analysis of regulatory flexibility under changing environmental conditions

    Science.gov (United States)

    Edwards, Kieron D; Akman, Ozgur E; Knox, Kirsten; Lumsden, Peter J; Thomson, Adrian W; Brown, Paul E; Pokhilko, Alexandra; Kozma-Bognar, Laszlo; Nagy, Ferenc; Rand, David A; Millar, Andrew J

    2010-01-01

    The circadian clock controls 24-h rhythms in many biological processes, allowing appropriate timing of biological rhythms relative to dawn and dusk. Known clock circuits include multiple, interlocked feedback loops. Theory suggested that multiple loops contribute the flexibility for molecular rhythms to track multiple phases of the external cycle. Clear dawn- and dusk-tracking rhythms illustrate the flexibility of timing in Ipomoea nil. Molecular clock components in Arabidopsis thaliana showed complex, photoperiod-dependent regulation, which was analysed by comparison with three contrasting models. A simple, quantitative measure, Dusk Sensitivity, was introduced to compare the behaviour of clock models with varying loop complexity. Evening-expressed clock genes showed photoperiod-dependent dusk sensitivity, as predicted by the three-loop model, whereas the one- and two-loop models tracked dawn and dusk, respectively. Output genes for starch degradation achieved dusk-tracking expression through light regulation, rather than a dusk-tracking rhythm. Model analysis predicted which biochemical processes could be manipulated to extend dusk tracking. Our results reveal how an operating principle of biological regulators applies specifically to the plant circadian clock. PMID:21045818

  9. Characteristics of the flankmagnetopause: Cluster observations

    CERN Document Server

    Haaland, S; Tenfjord, P; Gjerloev, J; Maes, L; DeKeyser, J; Maggiolo, R; Anekallu, C; Dorville, N

    2016-01-01

    The magnetopause is a current sheet forming the boundary between the geomagnetic field on one side and the shocked solar wind on the other side. This paper discusses properties of the low-latitude dawn and dusk flanks of the magnetopause. The reported results are based on a large number of measurements obtained by the Cluster satellites during magnetopause traversals. Using a combination of single-spacecraft and multispacecraft techniques, we calculated macroscopic features such as thickness, location, and motion of the magnetopause. The results show that the typical flank magnetopause is significantly thicker than the dayside magnetopause and also possesses a pronounced and persistent dawn-dusk asymmetry. Thicknesses vary from 150 to 5000 km, with an median thickness of around 1400 km at dawn and around 1150 km at dusk. Current densities are on average higher on dusk, suggesting that the total current at dawn and dusk are similar. Solar wind conditions and the interplanetary magnetic field cannot fully expla...

  10. Application of line-transect sampling to estimate wintering wood ducks and mallards and availability of natural cavities and nesting success of wood ducks in stands of bald cypress and tupelo gum

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Line-transect sampling, flying-duck counts at dusk, and aerial surveys from fixed-winged aircraft and a helicopter were evaluated for estimating densities of...

  11. Ion motion in the current sheet with sheared magnetic field – Part 1: Quasi-adiabatic theory

    Directory of Open Access Journals (Sweden)

    A. V. Artemyev

    2013-02-01

    Full Text Available We present a theory of trapped ion motion in the magnetotail current sheet with a constant dawn–dusk component of the magnetic field. Particle trajectories are described analytically using the quasi-adiabatic invariant corresponding to averaging of fast oscillations around the tangential component of the magnetic field. We consider particle dynamics in the quasi-adiabatic approximation and demonstrate that the principal role is played by large (so called geometrical jumps of the quasi-adiabatic invariant. These jumps appear due to the current sheet asymmetry related to the presence of the dawn–dusk magnetic field. The analytical description is compared with results of numerical integration. We show that there are four possible regimes of particle motion. Each regime is characterized by certain ranges of values of the dawn–dusk magnetic field and particle energy. We find the critical value of the dawn–dusk magnetic field, where jumps of the quasi-adiabatic invariant vanish.

  12. happiness is devotion

    Institute of Scientific and Technical Information of China (English)

    龚丽君

    2011-01-01

    Under the scorching sun, an old man sat by the bankstaring at the buoy on the river. From dawn to dusk he stillgot nothing in his hands. However, the old man was happyat ease. I felt so puzzled about it.

  13. Characteristics of > 290 keV magnetosheath ions

    Directory of Open Access Journals (Sweden)

    A. Rigas

    Full Text Available We performed a statistical analysis of 290-500 keV ion data obtained by IMP-8 during the years 1982-1988 within the earth's magnetosheath and analysed in detail some time periods withdistinct ion bursts. These studies reveal the following characteristics for magnetosheath 290-500 keV energetic ions: (a the occurrence frequency and the flux of ions increase with increasing geomagnetic activity as indicated by the Kp index; the occurrence frequency was found to be as high as P > 42% for Kp > 2, (b the occurrence frequency in the dusk magnetosheath was found to be slightly dependent on the local time and ranged between ~30% and ~46% for all Kp values; the highest occurrence frequency was detected near the dusk magnetopause (21 LT, (c the high energy ion bursts display a dawn-dusk asymmetry in their maximum fluxes, with higher fluxes appearing in the dusk magnetosheath, and (d the observations in the dusk magnetosheath suggest that there exist intensity gradients of energetic ions from the bow shock toward the magnetopause. The statistical results are consistent with the concept that leakage of magnetospheric ions from the dusk magnetopause is a semi-permanent physical process often providing the magnetosheath with high energy (290-500 keV ions.Key words. Magnetospheric physics (magnetosheath; planetary magnetospheres. Space plasma physics (shock waves.

  14. Application of ground-truth for classification and quantification of bird movements on migratory bird habitat initiative sites in southwest Louisiana: final report

    Science.gov (United States)

    Barrow, Wylie C.; Baldwin, Michael J.; Randall, Lori A.; Pitre, John; Dudley, Kyle J.

    2013-01-01

    This project was initiated to assess migrating and wintering bird use of lands enrolled in the Natural Resources Conservation Service’s (NRCS) Migratory Bird Habitat Initiative (MBHI). The MBHI program was developed in response to the Deepwater Horizon oil spill in 2010, with the goal of improving/creating habitat for waterbirds affected by the spill. In collaboration with the University of Delaware (UDEL), we used weather surveillance radar data (Sieges 2014), portable marine radar data, thermal infrared images, and visual observations to assess bird use of MBHI easements. Migrating and wintering birds routinely make synchronous flights near dusk (e.g., departure during migration, feeding flights during winter). Weather radars readily detect birds at the onset of these flights and have proven to be useful remote sensing tools for assessing bird-habitat relations during migration and determining the response of wintering waterfowl to wetland restoration (e.g., Wetlands Reserve Program lands). However, ground-truthing is required to identify radar echoes to species or species group. We designed a field study to ground-truth a larger-scale, weather radar assessment of bird use of MBHI sites in southwest Louisiana. We examined seasonal bird use of MBHI fields in fall, winter, and spring of 2011-2012. To assess diurnal use, we conducted total area surveys of MBHI sites in the afternoon, collecting data on bird species composition, abundance, behavior, and habitat use. In the evenings, we quantified bird activity at the MBHI easements and described flight behavior (i.e., birds landing in, departing from, circling, or flying over the MBHI tract). Our field sampling captured the onset of evening flights and spanned the period of collection of the weather radar data analyzed. Pre- and post-dusk surveys were conducted using a portable radar system and a thermal infrared camera. Landbirds, shorebirds, and wading birds were commonly found on MBHI fields during diurnal

  15. Diurnal activity of soil surface arthropods in agroecosystems: design for an inexpensive time-sorting pitfall trap

    Energy Technology Data Exchange (ETDEWEB)

    Blumberg, A.Y.; Crossley, D.A. Jr.

    1986-01-01

    The design for an inexpensive time-sorting pitfall trap is presented. The basis of the mechanism is a rotary stepping solenoid powered by lantern batteries. Traps were utilized to sample soil surface arthropods at two hour intervals for five 24 hr periods in 1983. One trap each was placed in conventional tillage (CT) and no-tillage (NT) agroecosystems. Soil arthropod surface activity was greatest in CT on 9 July during the dawn and dusk periods but the data did not indicate other dominant trends. Activity in NT was greatest during dusk on 27 June, but again no other dominant trends were evident. When CT and NT are combined over the sample dates, surface soil arthropod activity peaked during dusk, with a smaller activity peak at dawn. 10 refs., 6 figs.

  16. Investigation of EMIC Waves During Balloon Detected Relativistic Electron Precipitation Events

    Science.gov (United States)

    Woodger, L. A.; Millan, R. M.

    2009-12-01

    Multiple relativistic electron precipitation (REP) events were detected by balloon-borne instrumentation during the MAXIS 2000 and MINIS 2005 campaigns. It has been suggested that resonance with EMIC waves caused these precipitation events (Lorentzen et al, 2000 and Millan et al, 2002) due to their location in the dusk sector. We present observations of dusk-side relativistic electron precipitation events, and use supporting satellite and theoretical data to investigate the relationship between EMIC waves and the detected REP. Satellite data can provide direct measurements of not only the waves themselves but also important resonance condition parameters. The data will be presented collectively with each event to showcase similarities and differences between events and the challenges that arise in trying to understand the relationship between dusk-side relativistic electron precipitation and EMIC waves.

  17. Food for Thought

    Institute of Scientific and Technical Information of China (English)

    朱萍; MichaelFreeman

    2000-01-01

    As dusk falls in Manila the balut night salesmen appear carrying wicker baskets containing a mixture of egg and duck embryos which are a national delicacy and credited with enhancing male strength. Filipinos, who swear by the invigorating effects of balut,

  18. Spatial distribution of upstream magnetospheric ≥50 keV ions

    Directory of Open Access Journals (Sweden)

    G. Kaliabetsos

    Full Text Available We present for the first time a statistical study of geq50 keV ion events of a magnetospheric origin upstream from Earth's bow shock. The statistical analysis of the 50-220 keV ion events observed by the IMP-8 spacecraft shows: (1 a dawn-dusk asymmetry in ion distributions, with most events and lower intensities upstream from the quasi-parallel pre-dawn side (4 LT-6 LT of the bow shock, (2 highest ion fluxes upstream from the nose/dusk side of the bow shock under an almost radial interplanetary magnetic field (IMF configuration, and (3 a positive correlation of the ion intensities with the solar wind speed and the index of geomagnetic index Kp, with an average solar wind speed as high as 620 km s-1 and values of the index Kp > 2. The statistical results are consistent with (1 preferential leakage of ~50 keV magnetospheric ions from the dusk magnetopause, (2 nearly scatter free motion of ~50 keV ions within the magnetosheath, and (3 final escape of magnetospheric ions from the quasi-parallel dawn side of the bow shock. An additional statistical analysis of higher energy (290-500 keV upstream ion events also shows a dawn-dusk asymmetry in the occurrence frequency of these events, with the occurrence frequency ranging between ~16%-~34% in the upstream region.Key words. Interplanetary physics (energetic particles; planetary bow shocks

  19. Northern Saw-whet Owls (Aegolius acadicus) captured at Cape May Point, NJ, 1980-1994: comparison of two capture techniques

    Science.gov (United States)

    Katharine E. Duffy; Patrick E. Matheny

    1997-01-01

    During autumn migration 1980-1994, 1,270 Northern Saw-whet Owls (Aegolius acadicus) (NSWO) were captured and banded at Cape May Point, NJ. From 1980-1988, captures were effected by passive mist-netting. From 1989-1994, an audiolure (NSWO territorial song broadcast loudly from dusk to dawn in the trapping area) was used to enhance capture rate. 638...

  20. Territorial behaviour and food composition of two pairs of the little owl Athene noctua Scopoli, 1769, nesting at a distance of only 40 m apart

    NARCIS (Netherlands)

    Bacia, Daria

    1998-01-01

    The little owl Athene noctua (Scopoli, 1769) is a small, nocturnal predator, most active from dusk to dawn, with a two-hour break after midnight. There is little or no hunting during daytime, not even when the birds are raising young (Cramp, 1985). Contrary to these observations, the histology of

  1. Modeling of plasma density in the earth's dayside inner magnetosphere

    NARCIS (Netherlands)

    Domrachev, VV; Chugunin, DV

    2002-01-01

    The results of comparison of the model profiles of density, obtained by means of the CDPDM model, with the experimental data of the ISEE-1 satellite for the years 1977-1983 are presented. The hypothesis on the validity of the mirror mapping of the convection boundary relative to the dawn-dusk

  2. The near-earth magnetic field at 1980 determined from Magsat data

    Science.gov (United States)

    Langel, R. A.; Estes, R. H.

    1985-01-01

    Data from the Magsat spacecraft for November 1979 through April 1980 and from 91 magnetic observatories for 1978 through 1982 are used to derive a spherical harmonic model of the earth's main magnetic field and its secular variation. Constant coefficients are determined through degree and order 13 and secular variation coefficients through degree and order 10. The first degree external terms and corresponding induced internal terms are given as a function of Dst. Preliminary modeling using separate data sets at dawn and dusk local time showed that the dusk data contains a substantial field contribution from the equatorial electrojet current. The final data set is selected first from dawn data and then augmented by dusk data to achieve a good geographic data distribution for each of three time periods: (1) November/December, 1979; (2) January/February, 1980; (3) March/April, 1980. A correction for the effects of the equatorial electrojet is applied to the dusk data utilized. The solution included calculation of fixed biases, or anomalies, for the observation data.

  3. Origin and Evolution of Europa's Oxygen Exosphere

    Science.gov (United States)

    Oza, Apurva V.; Leblanc, Francois; Schmidt, Carl; Johnson, Robert E.

    2016-10-01

    Europa's icy surface is constantly bombarded by sulfur and oxygen ions originating from the Io plasma torus. The momentum transferred to molecules in Europa's surface results in the sputtering of water ice, populating a water product exosphere. We simulate Europa's neutral exosphere using a ballistic 3D Monte Carlo routine and find that the O2 exosphere, while global, is not uniformly symmetric in Europa local time. The O2 exosphere, sourced at a rate of ~ 5 kg/s with a disk-averaged column density of NO2 ~ 2.5 x 1014 O2/cm2, preferentially accumulates towards Europa's dusk. These dawn-dusk atmospheric inhomogeneities escalate as the surface-bounded O2 dissociates into an atomic O corona via electron impact. The inhomogeneities persist and evolve throughout the satellite's orbit, implying a diurnal cycle of the exosphere, recently evidenced by a detailed HST oxygen aurorae campaign (Roth et al. 2016). We conclude that the consistently observed 50% increase in FUV auroral emission from dusk to dawn is principally driven by the day-to-night thermal diffusion of O2 coupled with the Coriolis acceleration. This leads to a dawn-to-dusk gradient, peaking at Europa's leading hemisphere. This exospheric oxygen cycle, dependent on both orbital longitude and magnetic latitude, is fundamentally due to the bulk-sputtering vector changing with respect to the subsolar and subjovian points throughout the orbit. In principle, a similar mechanism should be present at other tidally-locked, rapidly orbiting satellite exospheres.

  4. Circadian response reduction in light and response restoration in darkness : A "Skeleton" light pulse PRC study in mice (Mus musculus)

    NARCIS (Netherlands)

    Comas, M.; Beersma, D. G. M.; Spoelstra, K.; Daan, S.

    2007-01-01

    Entrainment may involve responses to dawn, to dusk, and to the light in between these transitions. Previous studies showed that the circadian system responds to only 2 light pulses, one at the beginning and one at the end of the day, in a similar way as to a full photoperiod, as long as the photoper

  5. Preliminary Keys to the Mosquitoes of Vietnam. Revision 1

    Science.gov (United States)

    1966-05-01

    low numbers in built-up areas. Aedes poicilius is the principal vector of bancroftian filariasis in the abaca growing areas of the Philippines...Adults bite severely at dusk and also during the daytime. They breed in water-filled axils of abaca , banana, aroid, taro, pandanus and pineapple

  6. Circadian response reduction in light and response restoration in darkness : A "Skeleton" light pulse PRC study in mice (Mus musculus)

    NARCIS (Netherlands)

    Comas, M.; Beersma, D. G. M.; Spoelstra, K.; Daan, S.

    2007-01-01

    Entrainment may involve responses to dawn, to dusk, and to the light in between these transitions. Previous studies showed that the circadian system responds to only 2 light pulses, one at the beginning and one at the end of the day, in a similar way as to a full photoperiod, as long as the

  7. Visibility conditions and diel period affect small-scale spatio-temporal behaviour of pike Esox lucius in the absence of prey and conspecifics

    DEFF Research Database (Denmark)

    Nilsson, P A; Baktoft, Henrik; Boel, Mikkel;

    2012-01-01

    Pike Esox lucius in the absence of prey and conspecifics were shown to have the highest habitat-change activity during dusk and to decrease preference for complex habitats in turbid water. As the behaviours indicate routine responses in the absence of behavioural interactions, E. lucius spatio...

  8. What goes down must come up: symmetry in light-induced migration behaviour of Daphnia

    NARCIS (Netherlands)

    Van Gool, E.; Ringelberg, J.

    2003-01-01

    During a short period of the year, Daphnia may perform a phenotypically induced diel vertical migration. For this to happen, light-induced swimming reactions must be enhanced both at dawn and at dusk. Enhanced swimming in response to light intensity increase can be elicited by fish-associated kairom

  9. 论门

    Institute of Scientific and Technical Information of China (English)

    克·达·莫利; 李兰蓉

    2007-01-01

    <正>The opening and closing of doors are the most significant actions of man’s life.What a mystery lies in doors! No man knows what awaits him when he opens a door.Even the most familiar room,where the clock ticks and the hearth glows red at dusk,may harbor surprises.The plumber may

  10. Environmental elements involved in communal roosting in Heliconius butterflies (Lepidoptera: Nymphalidae).

    Science.gov (United States)

    Salcedo, Christian

    2010-06-01

    Several Heliconius L. butterflies species form nocturnal aggregations in sites with a particular architecture. Roosts are usually formed under relatively dense vegetation mats where dry vines or branches provide a perch for the night. These sites may last for months. To understand the importance of factors related to the expression of Heliconius roosting, data on light, temperature, relative humidity, wind, and use of wing color cues were recorded at H. erato and H. sara roost sites in Costa Rica and Panama in 2008 and 2009. The results show that roost sites offer reduced light conditions at dusk, provide a drier environment compared with its vicinity, and offer protection from wind and rain. Moreover, individuals use wing color recognition under reduced light conditions at dusk to successfully assemble aggregations. These findings provide key information for future experiments to study the use of landmarks, hygrosensitivity, and dim-light eye adaptations in Heliconius navigation to find roost sites.

  11. The Boat Girl in the Photo

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The Little Boat Girl THIS picture was taken at dusk, onestormy day, half a century ago. On April 21, 1949, one million soldiersof the Chinese People’s Liberation Army, alongmore than 500-kilometers of riverbank, quicklybroke through the "thousand-Li line of defence,"which had been painstakingly built up by theKuomintang, and forced the Changjiang River. At dusk on April 22, boatmen from Yangzhong,an island in the Changjiang River, hurried to thebank to row the follow-up units across. Despitearduous weather, the boatmen’s skill in fightingagainst wind and waves was considerable and, inthe soft lights of sunset, the rows of old woodenboats appeared to be flying on the ChangjiangRiver. A most impressive scene. Among the officers waiting on the riverbank tobe ferried across was one tall soldier, deeplyabsorbed in the sight of a young girl, not far away,

  12. Effects of fasting on Blood pressure in normotensive males

    OpenAIRE

    Fatima Samad

    2016-01-01

    Muslims all over the world fast in the holy month of Ramadan. Fasting means abstinence from drinking any liquids, eating, smoking and taking anything parenterally.  It is intermittent in nature from the start of dawn to end at dusk. Fasting has various physiological effects on different biological parameters of the human body. Previous studies that look at effect of Ramadan fasting on blood pressure have focused mainly on hypertensive patients and patients with already established heart disea...

  13. Detailed Analysis Case Studies of Trapped Plasmas at the Earth’s Magnetic Equator

    Science.gov (United States)

    1993-06-01

    5 Figure 2. Plasma Density L Dependance ...... ......... 7 Figure 3. Plasmapause Magnetic Activity Dependance . . 8 Figure 4. Plasma Density L... Dependance - Normalized . . 10 Figure 5. The Dusk Bulge . . . .............. 13 Figure 6. Magnetosphere’s Electric and Magnetic Fields 14 Figure 7...1970). 6 -. ~ .ZJ.:AUGUST 12,1968 . -. ----- OUTBOUND PASS - 2 3 4 5 ___ ... 7....9 L Figure 2. Plasma Density L Dependance 7 0D3 #n /2 OUT JND tN

  14. Emotional Undercurrents Beneath the Calm S urface---Langston Hughes’s Writing?Skills Seen in?Early Autumn

    Institute of Scientific and Technical Information of China (English)

    牛玉琴

    2014-01-01

    Langston Hughes,a versatile American black writer,published a lot of poems and short stories,with humor as outstanding fea-ture.However,in his Early Autumn he used unique skills to express the main female character’s emotional undercurrents beneath the calm sur-face through simple language,superficial calmness,especially through the writing skills of comparisonand contrast,as well as setting off atmos-phere of early autumn,dusk.

  15. TREX13 Data Analysis/Modeling

    Science.gov (United States)

    2015-09-30

    TREX13 ( Target and REverberation eXperiment) was conducted during April-June, 2013 off the coast of Panama City, Florida where the water depth is...is especially notable after dusk and before sunrise. (4) Target detection under varying environmental condition. Among the category (1) data, a...transmission follows a 30-s cycle with the signal on for 15 s and then off for 15 s, it is natural to segment the continuous time series into pings with

  16. On chaotic conductivity in the magnetotail

    Science.gov (United States)

    Holland, Daniel L.; Chen, James

    1992-01-01

    The concept of chaotic conductivity and the acceleration of particles due to a constant dawn dusk electric field are studied in a magnetotail-like magnetic field. A test particle simulation is used including the full nonlinear dynamics. It is found that the acceleration process can be understood without invoking chaos and that the cross tail current is determined by the particle dynamics and distributions. It is concluded that in general there is no simple relationship between the electric field and the current.

  17. A Laboratory Study of the Effects of Diet and Bright Light Countermeasures to Jet Lag

    Science.gov (United States)

    1990-03-01

    within a food group using the nutrition handbook for diabetics as a reference (14]. At dinner on the day before the shift occurred (Day 7), a subject in...publication. 34 References [1] Lewy AJ, Wehr TA, Goodwin FK, Newsome DA and Markey SP. Light suppresses melatonin secretion in humans. Science 210:1267-1269... Melatonin Production: Shifting "Dawn" and "Dusk" Shifts the Dim Light Melatonin Onset (DLUMO). Annals New York Academy of Sciences 453:253-259, 1985

  18. Air-to-Ground Visual Simulation Demonstration. Volume 1

    Science.gov (United States)

    1976-10-01

    influences by such methods as returning to the first device evaluated for an additional sortie and providing each pilot with an equal amount of task...taken at longer intervals after exposure. 11-51 With the passage of time, factors which influence a rater become less distinct. In Phase II, ratings...efforts are required to develop a more compact, high resolution, high brightness color televison projector. 6. Day/Dusk/Night Capability The display must be

  19. Visibility conditions and diel period affect small-scale spatio-temporal behaviour of pike Esox lucius in the absence of prey and conspecifics.

    Science.gov (United States)

    Nilsson, P A; Baktoft, H; Boel, M; Meier, K; Jacobsen, L; Rokkjaer, E M; Clausen, T; Skov, C

    2012-05-01

    Pike Esox lucius in the absence of prey and conspecifics were shown to have the highest habitat-change activity during dusk and to decrease preference for complex habitats in turbid water. As the behaviours indicate routine responses in the absence of behavioural interactions, E. lucius spatio-temporal distributions should be directly affected and thereby more easily assessed and avoided by prey, with potential consequences for encounter rates.

  20. Final Environmental Assessment (EA) for Modification of Airspace Units R-3008A/B/C from Visual Flight Rules (VFR) to VFR-Instrument Flight Rules (IFR) at Moody Air Force Base, Georgia

    Science.gov (United States)

    2015-09-30

    significant. Neotropical migrants are a classification of songbirds that primarily migrate at night to and from the tropics of South America and North... America every spring and fall. Roughly 75 percent of the songbirds migrate at levels between 500 and 2,000 feet AGL from dusk until dawn, and peak...of the ROI provide habitat that supports a large number of wildlife species. A total of 24 amphibian, 38 reptile , 34 mammal, 169 bird, and 23 fish

  1. Normal vision can compensate for the loss of the circadian clock.

    Science.gov (United States)

    Schlichting, Matthias; Menegazzi, Pamela; Helfrich-Förster, Charlotte

    2015-09-22

    Circadian clocks are thought to be essential for timing the daily activity of animals, and consequently increase fitness. This view was recently challenged for clock-less fruit flies and mice that exhibited astonishingly normal activity rhythms under outdoor conditions. Compensatory mechanisms appear to enable even clock mutants to live a normal life in nature. Here, we show that gradual daily increases/decreases of light in the laboratory suffice to provoke normally timed sharp morning (M) and evening (E) activity peaks in clock-less flies. We also show that the compound eyes, but not Cryptochrome (CRY), mediate the precise timing of M and E peaks under natural-like conditions, as CRY-less flies do and eyeless flies do not show these sharp peaks independently of a functional clock. Nevertheless, the circadian clock appears critical for anticipating dusk, as well as for inhibiting sharp activity peaks during midnight. Clock-less flies only increase E activity after dusk and not before the beginning of dusk, and respond strongly to twilight exposure in the middle of the night. Furthermore, the circadian clock responds to natural-like light cycles, by slightly broadening Timeless (TIM) abundance in the clock neurons, and this effect is mediated by CRY.

  2. Comparison of the dynamics and structure of Saturn and Jupiter magnetospheres: camshaft, magnetic anomalies and corotating convection models compared.

    Science.gov (United States)

    Southwood, D. J.; Kivelson, M. G.

    Scenarios are presented for the overall flux and mass circulation in the jovian and saturnian magnetospheres It is argued that similar fundamanetal processes underly the dynamical processes at both planets However the differences in parameter regime for the two systems leads to substantial resulting differences in morphology Transport is accomplished from the inner magnetosphere by interchange motion which then feeds into the outer magnetosphere where ballooning driven by centrifugal stress leads to field reconnection and plasma loss It seems likely that Jupiter loses much more material per rotation cycle than Saturn and is possibly much more symmetrically loaded in respect of planetary longitude Material loss and flux return at Jupiter have fixed orientations in local time early evening and morning sector respectively and newly returned flux is probably responsible for the morningside cushion region in the outer magnetosphere At Jupiter the dawn-dusk asymmetry in the current sheet thin in morning thick in afternoon is also a dominant feature At Saturn there seems no evidence of a cushion region flux return is thought to take place sporadically over much of the nightside Although definitive statements about the dusk plasma sheet await the orbit evolution of Cassini a fundamental observational feature in the Saturnian context is a planetary rotation induced magnetic field asymmetry which argues against major dawn-dusk asymmetry We propose the rotational feature could originate from a localized ionospheric magnetic anomaly The

  3. Magnetic reconnection in Saturn's magnetotail: A comprehensive magnetic field survey

    Science.gov (United States)

    Smith, A. W.; Jackman, C. M.; Thomsen, M. F.

    2016-04-01

    Reconnection within planetary magnetotails is responsible for locally energizing particles and changing the magnetic topology. Its role in terms of global magnetospheric dynamics can involve changing the mass and flux content of the magnetosphere. We have identified reconnection related events in spacecraft magnetometer data recorded during Cassini's exploration of Saturn's magnetotail. The events are identified from deflections in the north-south component of the magnetic field, significant above a background level. Data were selected to provide full tail coverage, encompassing the dawn and dusk flanks as well as the deepest midnight orbits. Overall 2094 reconnection related events were identified, with an average rate of 5.0 events per day. The majority of events occur in clusters (within 3 h of other events). We examine changes in this rate in terms of local time and latitude coverage, taking seasonal effects into account. The observed reconnection rate peaks postmidnight with more infrequent but steady loss seen on the dusk flank. We estimate the mass loss from the event catalog and find it to be insufficient to balance the input from the moon Enceladus. Several reasons for this discrepancy are discussed. The reconnection X line location appears to be highly variable, though a statistical separation between events tailward and planetward of the X line is observed at a radial distance of between 20 and 30RS downtail. The small sample size at dawn prevents comprehensive statistical comparison with the dusk flank observations in terms of flux closure.

  4. IMF dependence of energetic oxygen and hydrogen ion distributions in the near-Earth magnetosphere

    Science.gov (United States)

    Luo, H.; Kronberg, E. A.; Nykyri, K.; Trattner, K. J.; Daly, P. W.; Chen, G. X.; Du, A. M.; Ge, Y. S.

    2017-05-01

    Energetic ion distributions in the near-Earth plasma sheet can provide important information for understanding the entry of ions into the magnetosphere and their transportation, acceleration, and losses in the near-Earth region. In this study, 11 years of energetic proton and oxygen observations (> 274 keV) from Cluster/Research with Adaptive Particle Imaging Detectors were used to statistically study the energetic ion distributions in the near-Earth region. The dawn-dusk asymmetries of the distributions in three different regions (dayside magnetosphere, near-Earth nightside plasma sheet, and tail plasma sheet) are examined in Northern and Southern Hemispheres. The results show that the energetic ion distributions are influenced by the dawn-dusk interplanetary magnetic field (IMF) direction. The enhancement of ion intensity largely correlates with the location of the magnetic reconnection at the magnetopause. The results imply that substorm-related acceleration processes in the magnetotail are not the only source of energetic ions in the dayside and the near-Earth magnetosphere. Energetic ions delivered through reconnection at the magnetopause significantly affect the energetic ion population in the magnetosphere. We also believe that the influence of the dawn-dusk IMF direction should not be neglected in models of the particle population in the magnetosphere.

  5. IMF dependence of energetic oxygen and hydrogen ion distributions in the near-Earth plasma sheet

    Science.gov (United States)

    Luo, Hao; Kronberg, Elena; Nykyri, Katariina; Daly, Patrick; Chen, Gengxiong; Du, Aimin; Ge, Yasong

    2017-04-01

    Energetic ion distributions in the near-Earth plasma sheet can provide important information for understanding the entry of ions into the magnetosphere, and their transportation, acceleration, and losses in the near-Earth region. In this study, 11 years of energetic proton and oxygen observations (> 100 keV) from Cluster/RAPID were used to statistically study the energetic ion distributions in the near-Earth region. The dawn-dusk asymmetries of the distributions in three different regions (dayside magnetosphere, near-Earth nightside plasma sheet, and tail plasma sheet) are examined in northern and southern hemispheres. The results show that the energetic ion distributions are influenced by the dawn-dusk IMF direction. The enhancement of intensity largely correlates with the location of the magnetic reconnection at the magnetopause and the consequent formation of a diamagnetic cavity in the same quadrant of the magnetosphere. The results imply that substorm-related processes in the magnetotail are not the only source of energetic ions in the dayside and the near-Earth plasma sheet. We propose that large-scale cusp diamagnetic cavities can be an additional source and can thus significantly affect the energetic ion population in the magnetosphere. We also believe that the influence of the dawn-dusk IMF direction should not be neglected in models of the particle population in the magnetosphere.

  6. High-latitude HF Doppler observations of ULF waves: 2. Waves with small spatial scale sizes

    Directory of Open Access Journals (Sweden)

    D. M. Wright

    Full Text Available The DOPE (Doppler Pulsation Experiment HF Doppler sounder located near Tromsø, Norway (geographic: 69.6°N 19.2°E; L = 6.3 is deployed to observe signatures, in the high-latitude ionosphere, of magnetospheric ULF waves. A type of wave has been identified which exhibits no simultaneous ground magnetic signature. They can be subdivided into two classes which occur in the dawn and dusk local time sectors respectively. They generally have frequencies greater than the resonance fundamentals of local field lines. It is suggested that these may be the signatures of high-m ULF waves where the ground magnetic signature has been strongly attenuated as a result of the scale size of the waves. The dawn population demonstrate similarities to a type of magnetospheric wave known as giant (Pg pulsations which tend to be resonant at higher harmonics on magnetic field lines. In contrast, the waves occurring in the dusk sector are believed to be related to the storm-time Pc5s previously reported in VHF radar data. Dst measurements support these observations by indicating that the dawn and dusk classes of waves occur respectively during geomagnetically quiet and more active intervals.

    Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions · Magnetospheric physics (MHD waves and instabilities

  7. Photoperiodic control of the floral transition through a distinct polycomb repressive complex.

    Science.gov (United States)

    Wang, Yizhong; Gu, Xiaofeng; Yuan, Wenya; Schmitz, Robert J; He, Yuehui

    2014-03-31

    Polycomb group (PcG) complexes such as PRC1 mediate transcriptional repression. Here, we show that the plant-specific EMBRYONIC FLOWER1 (EMF1), LIKE HETEROCHROMATIN PROTEIN1, and a histone H3 lysine-4 demethylase form a distinct PcG complex, termed EMF1c, that plays PRC1-like roles and is crucial for regulation of the florigen gene FLOWERING LOCUS T (FT) in Arabidopsis. Long-day photoperiods promote FT expression activation in leaf veins specifically at dusk through the photoperiod pathway to induce Arabidopsis flowering. We found that before dusk and at night, a vascular EMF1c directly represses FT expression to prevent photoperiod-independent flowering, whereas at dusk EMF1 binding to FT chromatin is disrupted by the photoperiod pathway, leading to proper FT activation. Furthermore, a MADS-domain transcription factor and potent floral repressor binds EMF1 to repress FT expression. Our study reveals that the vascular EMF1c integrates inputs from several flowering-regulatory pathways to synchronize flowering time to environmental cues.

  8. Response of the magnetic field and plasmas at the geosynchronous orbit to interplanetary shock

    Institute of Scientific and Technical Information of China (English)

    YUE Chao; ZONG QiuGang; WANG YongFu

    2009-01-01

    Interplanetary shock can greatly disturb the Earth's magnetosphere and ionosphere,causing the temporal and spatial changes of the magnetic field and plasmas at the geosynchronous orbit.In this paper,we use the magnetic field data of GOES satellites from 1997 to 2007 and the plasma data of MPA on the LANL satellites from 1997 to 2004 to study the properties of magnetic field and plasma (0.03-45 keV) at the geosynchronous orbit (6.6 R_E) within 3 hours before and after the arrival of shock front at the geosynchronous orbit through both case study and superposed epoch analysis.It is found that following the arrival of shock front at the geosynchronous orbit,the magnetic field magnitude,as well as GSM B_z component increases significantly on the dayside (8-16 LT),while the By component has almost no change before and after shock impacts.In response to the interplanetary shock,the proton becomes much denser with a peak number density of 1.2 cm~(-3),compared to the typical number density of 0.7 cm~(-3).The proton temperature increases sharply,predominantly on the dusk and night side.The electron,density increases dramatically on the night side with a peak number density of 2.0 cm~(-3).The inferred ionospheric O~+ density after the interplanetary shock impact reaches the maximum value of 1.2 cm~(-3) on the dusk side and exhibits the clear dawn-dusk asymmetry.The peak of the anisotropy of proton's temperature is located at the noon sector,and the anisotropy decreases towards the dawn and dusk side.The minimum of temperature anisotropy is on the night side.It is suggested that the electromagnetic ion cyclotron (EMIC) wave and whistler wave can be stimulated by the proton and electron temperature anisotropy respectively.The computed electromagnetic ion cyclotron wave (EMIC) intense on the day side (8-16 LT) with a frequency value of 0.8 Hz,and the wave intensity decreases towards the dawn and dusk side,the minimum value can be found on the night side.The computed electron

  9. Survey of energetic O+ ions near the dayside mid-latitude magnetopause with Cluster

    Directory of Open Access Journals (Sweden)

    H. Rème

    2005-06-01

    Full Text Available Since December 2000, the Cluster satellites have been conducting detailed measurements of the magnetospheric boundaries and have confirmed the unambiguous presence of ions of terrestrial origin (e.g. O+ in regions adjacent to the dayside, mid-latitude magnetopause. In the present paper, we focus on the statistical properties of the O+ ion component at energies ranging from 30eV up to 40keV, using three years of ion data at solar maximum from the Cluster Ion Spectrometry (CIS experiment aboard two Cluster spacecraft. The O+ density decreases on average by a factor of 6, from 0.041 to 7x10-3cm-3 when crossing the magnetopause from the magnetosphere to the magnetosheath, but depends on several parameters, such as the geomagnetic activity or the modified disturbed storm time index (Dst*, and on their location. The O+ density is significantly higher in the dusk-side than in the dawn side region, which is consistent with the view that they originate mainly from the plasma sheet. A remarkable finding is that inward of the magnetopause, O+ is the dominant contributor to the mass density 30% of the time on the dusk-side in comparison to 3% in the dawnside and 4% near noon. On an event basis in the dusk flank of the magnetopause, we point out that O+ ions, when dominating the mass composition, lower the threshold for generating the Kelvin-Helmholtz instability, which may allow plasma exchange between the magnetosheath and the plasma sheet. We also discuss the effect of a substantial O+ ion component when present in a reconnection region.

  10. Polar cap flow channel events: spontaneous and driven responses

    Directory of Open Access Journals (Sweden)

    P. E. Sandholt

    2010-11-01

    Full Text Available We present two case studies of specific flow channel events appearing at the dusk and/or dawn polar cap boundary during passage at Earth of interplanetary (IP coronal mass ejections (ICMEs on 10 January and 25 July 2004. The channels of enhanced (>1 km/s antisunward convection are documented by SuperDARN radars and dawn-dusk crossings of the polar cap by the DMSP F13 satellite. The relationship with Birkeland currents (C1–C2 located poleward of the traditional R1–R2 currents is demonstrated. The convection events are manifest in ground magnetic deflections obtained from the IMAGE (International Monitor for Auroral Geomagnetic Effects Svalbard chain of ground magnetometer stations located within 71–76° MLAT. By combining the ionospheric convection data and the ground magnetograms we are able to study the temporal behaviour of the convection events. In the two ICME case studies the convection events belong to two different categories, i.e., directly driven and spontaneous events. In the 10 January case two sharp southward turnings of the ICME magnetic field excited corresponding convection events as detected by IMAGE and SuperDARN. We use this case to determine the ground magnetic signature of enhanced flow channel events (the NH-dusk/By<0 variant. In the 25 July case a several-hour-long interval of steady southwest ICME field (Bz<0; By<0 gave rise to a long series of spontaneous convection events as detected by IMAGE when the ground stations swept through the 12:00–18:00 MLT sector. From the ground-satellite conjunction on 25 July we infer the pulsed nature of the polar cap ionospheric flow channel events in this case. The typical duration of these convection enhancements in the polar cap is 10 min.

  11. A study of Pc-5 ULF oscillations

    Directory of Open Access Journals (Sweden)

    M. K. Hudson

    2004-01-01

    Full Text Available A study of Pc-5 magnetic pulsations using data from the Combined Release and Radiation Effects Satellite (CRRES was carried out. Three-component dynamic magnetic field spectrograms have been used to survey ULF pulsation activity for the approximate fourteen month lifetime of CRRES. Two-hour panels of dynamic spectra were examined to find events which fall into two basic categories: 1 toroidal modes (fundamental and harmonic resonances and 2 poloidal modes, which include compressional oscillations. The occurence rates were determined as a function of L value and local time. The main result is a comparable probability of occurence of toroidal mode oscillations on the dawn and dusk sides of the magnetosphere inside geosynchronous orbit, while poloidal mode oscillations occur predominantly along the dusk side, consistent with high azimuthal mode number excitation by ring current ions.

    Pc-5 pulsations following Storm Sudden Commencements (SSCs were examined separately. The spatial distribution of modes for the SSC events was consistent with the statistical study for the lifetime of CRRES. The toroidal fundamental (and harmonic resonances are the dominant mode seen on the dawn-side of the magnetosphere following SSCs. Power is mixed in all three components. In the 21 dusk side SSC events there were only a few examples of purely compressional (two or radial (one power in the CRRES study, a few more examples of purely toroidal modes (six, with all three components predominant in about half (ten of the events.

    Key words. Magnetospheric physics (MHD waves and instabilities; magnetospheric configuration and dynamics – Space plasma physics (waves and instabilities

  12. Turbulence in a Global Magnetohydrodynamic Simulation of the Earth's Magnetosphere during Northward and Southward Interplanetary Magnetic Field

    Science.gov (United States)

    El-Alaoui, M.; Richard, R. L.; Ashour-Abdalla, M.; Walker, R. J.; Goldstein, M. L.

    2012-01-01

    We report the results of MHD simulations of Earth's magnetosphere for idealized steady solar wind plasma and interplanetary magnetic field (IMF) conditions. The simulations feature purely northward and southward magnetic fields and were designed to study turbulence in the magnetotail plasma sheet. We found that the power spectral densities (PSDs) for both northward and southward IMF had the characteristics of turbulent flow. In both cases, the PSDs showed the three scale ranges expected from theory: the energy-containing scale, the inertial range, and the dissipative range. The results were generally consistent with in-situ observations and theoretical predictions. While the two cases studied, northward and southward IMF, had some similar characteristics, there were significant differences as well. For southward IMF, localized reconnection was the main energy source for the turbulence. For northward IMF, remnant reconnection contributed to driving the turbulence. Boundary waves may also have contributed. In both cases, the PSD slopes had spatial distributions in the dissipative range that reflected the pattern of resistive dissipation. For southward IMF there was a trend toward steeper slopes in the dissipative range with distance down the tail. For northward IMF there was a marked dusk-dawn asymmetry with steeper slopes on the dusk side of the tail. The inertial scale PSDs had a dusk-dawn symmetry during the northward IMF interval with steeper slopes on the dawn side. This asymmetry was not found in the distribution of inertial range slopes for southward IMF. The inertial range PSD slopes were clustered around values close to the theoretical expectation for both northward and southward IMF. In the dissipative range, however, the slopes were broadly distributed and the median values were significantly different, consistent with a different distribution of resistivity.

  13. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2007-06-01

    Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  14. Observations of a Unique Type of ULF Wave by Low-Altitude Space Technology 5 Satellites

    Science.gov (United States)

    Le, G.; Chi, P. J.; Strangeway, R. J.; Slavin, J. A.

    2011-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three-microsatellite constellation deployed into a 300 x 4500 km dawn-dusk and Sun-synchronous polar orbit with 105.6deg inclination angle. Because of the Earth's rotation and the dipole tilt effect, the spacecraft's dawn-dusk orbit track can reach as low as subauroral latitudes during the course of a day. Whenever the spacecraft traverse the dayside closed field line region at subauroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc2-3 frequency range. These Pc2-3 waves appear as wave packets with durations in the order of 5-10 min. As the maximum separations of the ST-5 spacecraft are in the order of 10 min, the three ST-5 satellites often observe very similar wave packets, implying these wave oscillations occur in a localized region. The coordinated ground-based magnetic observations at the spacecraft footprints, however, do not see waves in the Pc2-3 band; instead, the waves appear to be the common Pc4-5 waves associated with field line resonances. We suggest that these unique Pc2-3 waves seen by ST-5 are in fact the Doppler-shifted Pc4-5 waves as a result of rapid traverse of the spacecraft across the resonant field lines azimuthally at low altitudes. The observations with the unique spacecraft dawn-dusk orbits at proper altitudes and magnetic latitudes reveal the azimuthal characteristics of field line resonances.

  15. Generation of large-amplitude electric field and subsequent enhancement of O+ ion flux in the inner magnetosphere during substorms

    Science.gov (United States)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.

    2015-06-01

    Energetic O+ ions are rapidly enhanced in the inner magnetosphere because of abrupt intensification of the dawn-to-dusk electric field and significantly contribute to the ring current during substorms. Here we examine the generation mechanism of the dawn-to-dusk electric field that accelerates the O+ ions and the spatial and temporal evolution of the differential flux of the O+ ions by using a test particle simulation in the electric and magnetic fields that are provided by a global magnetohydrodynamics (MHD) simulation. In the MHD simulation, strong dawn-to-dusk electric field appears in the near-Earth tail region by a joint action of the earthward tension force and pileup of magnetic flux near an onset of substorm expansion. The peak of the electric field is ~9-13 mV/m and is located ~1-2 RE earthward of the peak of the plasma bulk speed because of the pileup. O+ ions coming from the lobe are accelerated from ~eV to >100 keV in ~10 min. The reconstructed flux of the O+ ions shows that at ~7 RE near midnight, the flux has a peak near a few tens of keV and the flux below ~10 keV is small. This structure, called a "void" structure, is consistent with the Polar observation and can be regarded as a manifestation of the acceleration of unmagnetized ions perpendicular to the magnetic field. In the inner magnetosphere (at 6.0 RE), reconstructed energy-time spectrograms show the nose dispersion structure that is also consistent with satellite observations.

  16. Solar Cookers for Fish Village

    Institute of Scientific and Technical Information of China (English)

    JERMAY; JAMSU; KEVIN; STUART

    2002-01-01

    Collecting wood was areal pain in the fore-head. We used to goto the forest to collectwood thirty times or so eachwinter regardless of the snowor wind. We had to get up anhour or so after midnight andafter doing our chores wewould head off to the forest.We didn’t return until dusk,"said Ms.Zhongcujia,aged 52and a resident of Niamu orFish Village,located in JiancaCounty,Malho TibetanAutonomous Prefecture,Qinghai Province,China. FishVillage is nestled on a denud-ed west-facing mountainslope.

  17. How biological (fish) noise affects the performance of shallow water passive array system

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, W.A.; Chakraborty, B.; Haris, K.; Vijayakumar, K.; Sundar, D.; Luis, R.A.A.; Mahanty, M.M.; Latha, G.

    strengths during 18:00 hr (dusk) and 06:00 hr (dawn) respectively (indicated in the figure), in order to determine whether the variations in the data can be attributed to biological activities. The data were analyzed by the time/ frequency spectrograms... to enhance element numbers (i.e., total seven elements) by reducing the inter-element spacing to 0.25m. C. Ancillary Data (Current meter, Wind) The recording current meter (RCM) deployed is based on the Sea Guard data logger (www...

  18. Ramadan fasting and dental treatment considerations: a review.

    Science.gov (United States)

    Shaeesta, Khaleelahmed Bhavikatti; Prabhuji, M Lv; Shruthi, J R

    2015-01-01

    During the sacred month of Ramadan, Muslims abstain from the consumption of food from dawn until dusk. Extended fasting hours produce changes in the body's metabolism during this period. A majority of the population who fast also restrict themselves from undergoing dental treatments due to a fear of breaking the fast. Even among health professionals, a certain amount of uncertainty prevails about the implications of treating a patient who is fasting. To help clinicians carry out safe and effective treatment without hampering a patient's religious beliefs, the present article focuses on the effect of Ramadan fasting on the body's metabolism and the ramifications for treatment aspects, including medications and dental procedures.

  19. Climatologies of nighttime upper thermospheric winds measured by ground-based Fabry-Perot interferometers during geomagnetically quiet conditions: 2. High-latitude circulation and interplanetary magnetic field dependence

    DEFF Research Database (Denmark)

    Emmert, J.T.; Hernandez, G.; Jarvis, M.J.;

    2006-01-01

    Stromfjord (67 degrees N, 51 degrees W), and Thule (77 degrees N, 68 degrees W). We examine the wind patterns as a function of magnetic local time and latitude, solar cycle, day of year, and the dawn-dusk and north-south components of the interplanetary magnetic field (IMF B-y and B-z). In magnetic...... at latitudes as low as that of Millstone Hill ( magnetic latitude 53 degrees N). Quiet time Bz effects are negligible except over the magnetic polar cap station of Thule....

  20. EISCAT Observations of Main Ionization Troughs in the High-Latitude Ionosphere

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    F-region electron density depletions associated with main ionization troughs in the high-latitude ionosphere are studied using EISCAT CP3 data of meridian scanning experiments. The troughs in our observations are found to appear mainly in dusk sector, extending from late afternoon to pre-midnight, with higher occurrence rate during equinox and winter. Simultaneous ion drift velocity in F-region shows that the main trough minimm is mostly located at the equator ward edge of the plasma convection flow, rather than in the r~ion where the largest ion flow are observed.

  1. The Antiaircraft Journal. Volume 92, Number 4, July-August 1949

    Science.gov (United States)

    1949-08-01

    picket ships at a radius of about 70 miles. Day fighters were landed at dusk and night fighters were " scrambled " and "pancaked" at odd intervals all... recip - ient and on the deliverer, and have analyzed the major mili- tary and political considerations which govern its use. From this scrutiny we must...Schlesinger) ..••........... 5.00 Civilization an Trial (Toynbee) •..•.....•... 3.50 Company Commander (MacDonald) 3.00 The Egg and I (MacDonald) 2.75

  2. Managing diabetes during the Muslim fasting month of Ramadan.

    Science.gov (United States)

    Velayudhan, M

    2012-06-01

    Target blood sugar levels in diabetes are achieved through manipulation of diet, exercise and medication. A change in any one of these three things can skew blood sugar levels and create complications associated with hyperglycemia or hypoglycemia. Fasting during the month of Ramadan is a religious activity that devout Muslims practice whether they are diabetic or not. Since such fasting involves abstinence from food and water for twelve hours or more during the day from dawn to dusk, it is evident that advice regarding exercise and medication will have to be modified during this period.

  3. Considerations of variations in ionospheric field effects in mapping equatorial lithospheric Magsat magnetic anomalies

    Science.gov (United States)

    Ravat, D.; Hinze, W. J.

    1993-01-01

    The longitudinal, seasonal, and altitude-dependent variability of the magnetic field in equatorial latitudes is investigated to determine the effect of these variabilities on the isolation of lithospheric Magsat magnetic anomalies. It was found that the amplitudes of the dawn dip-latitude averages were small compared to the dusk averages, and that they were of the opposite sign. The longitudinal variation in the equatorial amplitudes of the dawn dip-latitude averages was not entirely consistent with the present knowledge of the electrojet field. Based on the results, a procedure is implemented for reducing the equatorial ionospheric effects from the Magsat data on the lithospheric component.

  4. Central Plasma Sheet Ion Properties as Inferred from Ionospheric Observations

    Science.gov (United States)

    Wing, Simon; Newell, Patrick T.

    1998-01-01

    A method of inferring central plasma sheet (CPS) temperature, density, and pressure from ionospheric observations is developed. The advantage of this method over in situ measurements is that the CPS can be studied in its entirely, rather than only in fragments. As a result, for the first time, comprehensive two-dimensional equatorial maps of CPS pressure, density, and temperature within the isotropic plasma sheet are produced. These particle properties are calculated from data taken by the Special Sensor for Precipitating Particles, version 4 (SSJ4) particle instruments onboard DMSP F8, F9, F10, and F11 satellites during the entire year of 1992. Ion spectra occurring in conjunction with electron acceleration events are specifically excluded. Because of the variability of magnetotail stretching, the mapping to the plasma sheet is done using a modified Tsyganenko [1989] magnetic field model (T89) adjusted to agree with the actual magnetotail stretch at observation time. The latter is inferred with a high degree of accuracy (correlation coefficient -0.9) from the latitude of the DMSP b2i boundary (equivalent to the ion isotropy boundary). The results show that temperature, pressure, and density all exhibit dawn-dusk asymmetries unresolved with previous measurements. The ion temperature peaks near the midnight meridian. This peak, which has been associated with bursty bulk flow events, widens in the Y direction with increased activity. The temperature is higher at dusk than at dawn, and this asymmetry increases with decreasing distance from the Earth. In contrast, the density is higher at dawn than at dusk, and there appears to be a density enhancement in the low-latitude boundary layer regions which increases with decreasing magnetic activity. In the near-Earth regions, the pressure is higher at dusk than at dawn, but this asymmetry weakens with increasing distance from the Earth and may even reverse so that at distances X less than approx. 10 to -12 R(sub E

  5. Visual systems - The state of the art

    Science.gov (United States)

    Shorrock, David

    State-of-the-art, computer-generated image simulator visual systems typically encompass a data base which generates the model of the operating environment, an image generator, and a display system suitable for the applications envisaged. Two basic approaches to such systems are discernible: those employing hybrid raster/calligraphy and those using raster/continuous tone. Attention is presently given to such capabilities and elements of visual displays as texture effects, transparencies, fade level-of-detail management, animation effects, and image generator functions for daylight and night/dusk conditions, as well as prospective developments in this field.

  6. Structure of the plasmapause from ISEE 1 low-energy ion and plasma wave observations

    Science.gov (United States)

    Nagai, T.; Horwitz, J. L.; Anderson, R. R.; Chappell, C. R.

    1985-01-01

    Low-energy ion pitch angle distributions are compared with plasma density profiles in the near-earth magnetosphere using ISEE 1 observations. The classical plasmapause determined by the sharp density gradient is not always observed in the dayside region, whereas there almost always exists the ion pitch angle distribution transition from cold, isotropic to warm, bidirectional, field-aligned distributions. In the nightside region the plasmapause density gradient is typically found, and it normally coincides with the ion pitch angle distribution transition. The sunward motion of the plasma is found in the outer part of the 'plasmaspheric' plasma in the dusk bulge region.

  7. Effects of square-wave and simulated natural light-dark cycles on hamster circadian rhythms

    Science.gov (United States)

    Tang, I. H.; Murakami, D. M.; Fuller, C. A.

    1999-01-01

    Circadian rhythms of activity (Act) and body temperature (Tb) were recorded from male Syrian hamsters under square-wave (LDSq) and simulated natural (LDSN, with dawn and dusk transitions) light-dark cycles. Light intensity and data sampling were under the synchronized control of a laboratory computer. Changes in reactive and predictive onsets and offsets for the circadian rhythms of Act and Tb were examined in both lighting conditions. The reactive Act onset occurred 1.1 h earlier (P circadian entrainment characteristics under LDSq and LDSN, suggesting that gradual and abrupt transitions between light and dark may provide different temporal cues.

  8. On the problem of electron loss in the outer radiation belt during a magnetic storm

    Science.gov (United States)

    Lazutin, L. L.

    2016-09-01

    An abrupt change in the latitudinal profile of energetic electrons in the Earth's outer radiation belt during magnetic storms is explained in many publications by a loss of electrons at L = 4-7 resulting from their departure to the atmosphere or to the magnetopause. In the present work, the loss of electrons is explained primarily by adiabatic transformation of the magnetic drift trajectories. For this purpose, the effect of dawnto- dusk asymmetry measured by low-orbit SERVIS-1 and KORONAS-F satellites is involved.

  9. Opening the cusp. [using magnetic field topology

    Science.gov (United States)

    Crooker, N. U.; Toffoletto, F. R.; Gussenhoven, M. S.

    1991-01-01

    This paper discusses the magnetic field topology (determined by the superposition of dipole, image, and uniform fields) for mapping the cusp to the ionosphere. The model results are compared to both new and published observations and are then used to map the footprint of a flux transfer event caused by a time variation in the merging rate. It is shown that the cusp geometry distorts the field lines mapped from the magnetopause to yield footprints with dawn and dusk protrusions into the region of closed magnetic flux.

  10. The diel vertical migration of sound scatterers observed by an acoustic Doppler current profiler in the Luzon Strait from July 2009 to April 2011

    Institute of Scientific and Technical Information of China (English)

    YANG Chenghao; LIAO Guanghong; YUAN Yaochu; CHEN Hong; ZHU Xiaohua

    2013-01-01

    Acoustic Doppler current profiler (ADCP) receives echoes from sound scatterers, then their speed is calcu-lated by the Doppler effect. In the open ocean, most of these backscatterers are from the plankton. The sound scatterers descend down to depth at around dawn, their mean speed is 2.9 cm/s, then they ascend up to the surface layer at around dusk with a mean speed of 2.1 cm/s, in the Luzon Strait. The descending speed is faster, which suggests that this zooplankton population may accelerate its downward migration under the action of the gravity. The vertical distribution of a mean volume backscattering strength (MVB-S) in the nighttime has two peaks, which locate near the upper and lower boundary layers of halocline, respectively. However, the backscatterers only aggregate near the surface layer in the daytime. The diel ver-tical migration (DVM) of sound scatterers has several characteristic patterns, it is stronger in summer, but weaker in winter, and the maximum peak occurs in September. The DVM occurrence is synchronous with the seawater temperature increasing at around dawn and dusk, it may affect the ocean mixing and water stratification.

  11. Effect of the Interplanetary Electric Field on the Magnetopause From Global MHD Simulations

    Institute of Scientific and Technical Information of China (English)

    HUANG Zhaohui; DING Kai; WANG Chi

    2012-01-01

    The north-south component B_z of the Interplanetary Magnetic Field(IMF) and solar wind dynamic pressure P_d are generally treated as the two main factors in the solar wind that determine the geometry of the magnetosphere.By using the 3D global MHD simulations,we investigate the effect of the Interplanetary Electric Field(IEF) on the size and shape of magnetopause quantitatively. Our numerical experiments confirm that the geometry of the magnetopause are mainly determined by P_d and B_z,as expected.However,the dawn-dusk IEFs have great impact on the magnetopause erosion because of the magnetic reconnection,thus affecting the size and shape of the magnetopause.Higher solar wind speed with the same B_z will lead to bigger dawn-dusk IEFs,which means the higher reconnection rate,and then results in more magnetic flux removal from the dayside. Consequently,the dayside magnetopause moves inward and flank magnetopause moves outward.

  12. The origin of life and the left-handed amino-acid excess: the furthest heavens and the deepest seas?

    Science.gov (United States)

    Goodman, Geoffrey; Gershwin, M Eric

    2006-11-01

    The origin of life is an extraordinary problem that leads back to the structure and dynamics of the cosmos and early development of organic molecules. Within that wider question lies an unsolved problem that has troubled biologists for 150 years. What is the origin of the dominant presence of left-handed stereoisomers of amino acids in nature even though their synthesis normally results in an equal mixture of the right- and left-handed molecular forms? We propose that asymmetric Earth rotation caused at dawn and dusk circularly polarized UV light (CPUVL) of opposite polarity and reversed temperature profiles in the oceans. Destruction of the d-isomer by CPUVL at dusk in a sea surface hotter than at dawn created a daily l-isomer excess protected from radiation by nightfall, preserved by down-flow (diffusive, mechanical) into cold, darker regions, eventually initiating an l-amino-acid excess embodied in early marine forms. Innumerable mechanisms have been proposed for the origin of l-chiral dominance in amino acids and none proven. Since the thalidomide tragedy, homochirality of amino acids has been a growing practical issue for medicine. Understanding its origin may bring further and unexpected benefits. It may also be a modest pointer to the possibility of positive answers to whether intelligent life will have the capacity to continue to protect itself from conditions inimical to survival.

  13. The Hall current system revealed as a statistical significant pattern during fast flows

    Directory of Open Access Journals (Sweden)

    K. Snekvik

    2008-11-01

    Full Text Available We have examined the dawn-dusk component of the magnetic field, BY, in the night side current sheet during fast flows in the neutral sheet. 237 h of Cluster data from the plasma sheet between 2 August 2002 and 2 October 2002 have been analysed. The spatial pattern of BY as a function of the distance from the centre of the current sheet has been estimated by using a Harris current sheet model. We have used the average slopes of these patterns to estimate earthward and tailward currents. For earthward fast flows there is a tailward current in the inner central plasma sheet and an earthward current in the outer central plasma sheet on average. For tailward fast flows the currents are oppositely directed. These observations are interpreted as signatures of Hall currents in the reconnection region or as field aligned currents which are connected with these currents. Although fast flows often are associated with a dawn-dusk current wedge, we believe that we have managed to filter out such currents from our statistical patterns.

  14. Distribution of H2 in the Lunar Exosphere from LAMP Observations

    Science.gov (United States)

    Hurley, Dana; Retherford, Kurt; Cook, Jason; Grava, Cesare; Greathouse, Thomas; Gladstone, Randy; Stern, Alan

    2014-11-01

    Hydrogen gas (H2) has been detected in the Moon’s exosphere. It was identified spectrally during the LCROSS impact plume (Gladstone et al., 2010). Then it was found in LAMP data from the nominal exosphere (Stern et al., 2013). We examine the distribution of H2 in the lunar exosphere using a Monte Carlo model and data from the Lyman Alpha Mapping Project (LAMP) FUV imaging spectrograph onboard the Lunar Reconnaissance Orbiter (LRO). LAMP observations made in twilight, i.e., through illuminated exosphere, but with a footprint on the nightside of the Moon, are routinely made with LRO. However, during times when the beta angle of the orbit is close to beta=90°, a great portion of the nightside orbit is in the twilight viewing geometry. Using data from just behind the terminator on the post-dusk and pre-dawn sides, we compile a cumulative spectrum throughout LAMP’s bandpass. A dawn/dusk asymmetry is detected in the H2 abundance. Modeling is used to decipher the release mechanism and source distribution of diatomic hydrogen that best fits the observations. We examine the source rate and the total mass of the H2 exosphere consistent with the observations.

  15. Comparison between ionospheric convection vortices and the associated equivalent currents

    Science.gov (United States)

    Liang, J.; Benkevitch, L.; Sofko, G. J.; Koustov, A. V.

    2004-12-01

    The equivalent current pattern derived from CANOPUS, NRCAN/GSC and MACCS magnetometers has been compared with the ionospheric convection pattern observed by SuperDARN HF radars. The discrepancies between the equivalent convection (EQC) and the SuperDARN-observed convection (SDC) patterns are explained in terms of the effect of day-night photoionization conductance gradient and the coupling between field-aligned currents (FACs) and ionospheric conductances. In particular, the agreement between the EQC and SDC patterns is usually worse for a counterclockwise convection vortex than for a clockwise cell, but a consistent pattern of discrepancy for counterclockwise convection vortices has been found. We suggest that the discrepancies are due to a downward FAC-conductance coupling process. Since the counterclockwise vortices and clockwise vortices occur predominantly in the dawn and dusk sectors, respectively, in accordance with the usual 2-cell global convection pattern, the asymmetry between the EQC and SDC patterns for counterclockwise vortices and clockwise vortices would naturally lead to a dawn-dusk asymmetry as well. This is revealed by a global statistical study of the deviation of direction between the magnetic equivalent convection and the SuperDARN convection in different time sectors and latitudes. In the dawn sector, the statistical results reveal that, at lower latitudes, the EQC direction deviation is slightly counterclockwise with respect to the SDC direction, whereas the deviation is significantly clockwise at high latitudes. These deviations are consistent with the discrepancy pattern for counterclockwise convection vortices, as found in the individual vortex event studies.

  16. Dynamics of Subauroral Polarization Stream (SAPS) Structures

    Science.gov (United States)

    Sazykin, S. Y.; Coster, A. J.; Huba, J.; Ridley, A. J.; Erickson, P. J.; Foster, J. C.; Baker, J. B. H.; Wolf, R.

    2015-12-01

    The Subauroral Polarization Stream (SAPS) flow structures are narrow ionospheric channels of fast (in excess of 100 m/s) westward drift just outside the equatorward edge of the diffuse aurora in the dusk-to-midnight local time sector. Other terms for this phenomenon include subauroral Ion Drift (SAID) events and Polarization Jets. SAPS structures represent a striking departure from the commonly-used two-cell convection pattern. They are thought to arise from the displacement of the downward region-2 Birkeland currents on the dusk side equatorward of the low-latitude boundary of the auroral oval during times of changing high-latitude convection. In this paper, we will use several event simulations with the SAMI3-RCM numerical model (a self-consistent ionosphere-inner magnetosphere model) and RCM-GITM (a self-consistent model of the ionosphere-thermosphere-inner magnetosphere) to analyze the relative roles of changes in the IMF Bz component, ionospheric electron density depletions, and thermospheric modifications in controlling the dynamics of SAPS. Simulation results will be compared to multi-instrument ionospheric observations.

  17. The causes of the hardest electron precipitation events seen with SAMPEX

    Science.gov (United States)

    Smith, David M.; Casavant, Eric P.; Comess, Max D.; Liang, Xinqing; Bowers, Gregory S.; Selesnick, Richard S.; Clausen, Lasse B. N.; Millan, Robyn M.; Sample, John G.

    2016-09-01

    We studied the geomagnetic, plasmaspheric, and solar wind context of relativistic electron precipitation (REP) events seen with the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), Proton Electron Telescope (PET) to derive an exponential folding energy E0 for each event. Events with E0750 keV near dusk (1400 500 keV ("hard REP"), we estimate that roughly 45% of the whole population has the distributions of geomagnetic and solar wind parameters associated with EMIC waves, while 55% does not. We hypothesize that the latter events may be caused by current sheet scattering (CSS), which can be mistaken for EMIC wave scattering in that both simultaneously precipitate MeV electrons and keV protons. Since a large number of MeV electrons are lost in the near-midnight hard REP events, and in the large number of E0< 400 keV events that show no dusk-like peak at all, we conclude that CSS should be studied further as a possibly important loss channel for MeV electrons.

  18. The magnetic field of the equatorial magnetotail from 10 to 40 earth radii

    Science.gov (United States)

    Fairfield, D. H.

    1986-01-01

    A statistical study of IMP 6, 7, and 8 magnetotail magnetic field measurements near the equatorial plane reveals new information about various aspects of magnetospheric structure. More magnetic flux crosses the equatorial plane on the dawn and dusk flanks of the tail than near midnight, but no evidence is found for a dependence on the interplanetary magnetic field sector polarity. Field magnitudes within 3 earth radii of the equatorial plane near dawn are more than twice as large as those near dusk for Xsm = -20 to -10 earth radii. The frequency of occurrence of southward fields is greatest near midnight, and such fields are seen almost twice as often for Xsm = -20 to -10 earth radii as for Xsm beyond -20 earth radii. This latter result supports the idea that the midnight region of the tail between 10 and 20 is a special location where neutral lines are particularly apt to form. Such a neutral line will approach nearest the earth in the midnight and premidnight region, where substorms are thought to have their onset.

  19. The interaction of a magnetic cloud with the Earth - Ionospheric convection in the Northern and Southern Hemispheres for a wide range of quasi-steady interplanetary magnetic field conditions

    Science.gov (United States)

    Freeman, M. P.; Farrugia, C. J.; Burlaga, L. F.; Hairston, M. R.; Greenspan, M. E.; Ruohoniemi, J. M.; Lepping, R. P.

    1993-01-01

    Observations are presented of the ionospheric convection in cross sections of the polar cap and auroral zone as part of the study of the interaction of the Earth's magnetosphere with the magnetic cloud of January 13-15, 1988. For strongly northward IMF, the convection in the Southern Hemisphere is characterized by a two-cell convection pattern comfined to high latitudes with sunward flow over the pole. The strength of the flows is comparable to that later seen under southward IMF. Superimposed on this convection pattern there are clear dawn-dusk asymmetries associated with a one-cell convection component whose sense depends on the polarity of the magnetic cloud's large east-west magnetic field component. When the cloud's magnetic field turns southward, the convection is characterized by a two-cell pattern extending to lower latitude with antisunward flow over the pole. There is no evident interhemispheric difference in the structure and strength of the convection. Superimposed dawn-dusk asymmetries in the flow patterns are observed which are only in part attributable to the east-west component of the magnetic field.

  20. Studies of medium scale travelling ionospheric disturbances using TIGER SuperDARN radar sea echo observations

    Directory of Open Access Journals (Sweden)

    L.-S. He

    2004-12-01

    Full Text Available

    Seasonal and diurnal variations in the direction of propagation of medium-scale travelling ionospheric disturbances (MSTIDs have been investigated by analyzing sea echo returns detected by the TIGER SuperDARN radar located in Tasmania (43.4° S, 147.2° E geographic; –54.6°Λ. A strong dependency on local time was found, as well as significant seasonal variations. Generally, the propagation direction has a northward (i.e. equatorward component. In the early morning hours the direction of propagation is quite variable throughout the year. It then becomes predominantly northwest and changes to northeast around 09:00 LT. In late fall and winter it changes back to north/northwest around 15:00 LT. During the other seasons, northward propagation is very obvious near dawn and dusk, but no significant northward propagation is observed at noon.

    It is suggested that the variable propagation direction in the morning is related to irregular magnetic disturbances that occur at this local time. The changes in the MSTID propagation directions near dawn and dusk are generally consistent with changes in ionospheric electric fields occurring at these times and is consistent with dayside MSTIDs being generated by the Lorentz force.

    Key words. Ionosphere (ionospheric disturbances; wave propagation; ionospheric irregularities; signal processing

  1. Radar observations of the seasonal migration of brown planthopper (Nilaparvata lugens Stål) in Southern China.

    Science.gov (United States)

    Qi, H; Jiang, C; Zhang, Y; Yang, X; Cheng, D

    2014-12-01

    The summer and autumn migrations of the brown planthopper (Nilaparvata lugens) were observed in Southern China with a millimetric scanning entomological radar and a searchlight trap supplemented with capture in field cages, field surveys, and dissections of females. Nilaparvata lugens took off at dusk and dawn in summer, but in autumn there was sometimes only a dusk take-off. The variation of the area density of the radar targets indicated that flight durations were about 9-10 h. In summer, planthopper-size targets generally flew below 1800 m above ground level (AGL), although some insects reached 2000 m AGL; in autumn, they flew lower, generally below 1100 m although some insects reached 1700 m AGL. Multiple layer concentrations were seen every night in both summer and autumn. The depths of these layers in autumn were less than in summer. Nilaparvata lugens flew in strong winds; wind shear may be the main factor causing them to accumulate and form dense layers at certain heights. Nilaparvata lugens emigrating in summer from the vicinity of the radar site in the Northeastern Guangxi Zhuang Autonomous Region, and carried by the prevailing southwesterly wind, would have travelled northeastwards and reached Northern Hunan Province. In autumn, with the prevailing northeasterly wind, emigrants would have reached overwintering areas (south of 21°N).

  2. 3D PIC Simulation of the Magnetosphere during IMF Rotation from North to South: Signatures of Substorm Triggering in the Magnetotail

    Science.gov (United States)

    Nishikawa, Ken-Ichi; Cao. D/ S/; Lembege, B.

    2008-01-01

    Three dimensional PIC simulations are performed in order to analyse the dynamics of the magnetotail as the interplanetary magnetic field (IMF) rotates from northward to southward direction. This dynamics reveals to be quite different within meridian/equatorial planes over two successive phases of this rotation. First, as IMF rotates from North to Dawn-Dusk direction, the X-Point (magnetic reconnection) evidenced in the magnetotail (meridian plane) is moving earthward (from x=-35 Re to x=-17.5 ) distance at which it stabilizes. This motion is coupled with the formation of "Crosstail-S" patterns (within the plane perpendicular to the Sun-Earth mine) through the neutral sheet in the nearby magnetotail. Second, as IMF rotates from dawn-dusk to South, the minimum B field region is expanding within the equatorial plane and forms a ring. This two-steps dynamics is analyzed in strong association with the cross field magnetotail current Jy, in order to recover the signatures of substorms triggering.

  3. Impact of the Interplanetary Magnetic Field rotation from North to South on the Alfven Transition Layer: 3D Global PIC Simulation

    Science.gov (United States)

    Cai, DongSheng; Lembege, Bertrand; Nishikawa, Ken-ichi

    2017-04-01

    Using a global 3D PIC simulation, the solar-terrestrial magnetosphere interaction has been analyzed focusing on the 3D magnetic cusp region. Our recent global simulation results (Cai et al., JGR 2015) have reproduced the main features of the magnetic cusp under a northward IMF configuration comparing with the three-year statistical observations of Cluster satellites (Lavraud et al., JGR, 2005). One of the most important features found in our simulation is the existence of the Alfven Transition Layer (ATL) where Alfven Mach number is nearly zero almost adjacent to the upper stagnant exterior cusp (SEC). Its width measured near the SEC within the meridian plane varies from 1 to 4 Re. From the magnetosheath to SEC, the plasma flows transit from super to sub-Alfvenic regime. Striking features observed in the simulation is the unique depleted funnel shape ATL starting from the high altitude dusk to low altitude dawn above the magnetic cusp in a northward IMF. Both the ion and electron flux enter and spiral into the cups region through this depleted ATL with possibly a curvature drift. Varying IMF from north to south through dusk-dawn direction, this ATL persists although it drastically shrinks. Especially, in the southward IMF, the ion flux enters into the cusp region through the complicated ATL and bounce back to the magnetosheath. ATL can help us to investigate the complex structures of the magnetic cusp.

  4. Observations of IMF and seasonal effects in high-latitude convection

    Science.gov (United States)

    Ruohoniemi, J. M.; Greenwald, R. A.

    1995-01-01

    Strong interplanetary magnetic field (IMF) and seasonal effects in the convection of nightside ionospheric plasma are described. The findings are based on a statistical analysis of observations made with the Johns Hopkins University/ Applied Physics Lab (JHU/APL) HF radar located at Goose Bay, Labrador. For positive sign of the IMF dusk-dawn component, By greater than 0 the dawn cell is more crescent shaped and the dusk cell more round while for BY less than 0 these pairings of size and shape are reversed. The more extreme crescent /round cell dichotomy is obtained for BY greater than 0. The return flows associated with the crescent-shaped cell dominate at midnight MLT (magnetic local time); the reversal in the zonal velocity in the 67 deg-69 deg lambda (magnetic latitude) interval occurs 2.5 hr earlier in summer than in winter. The maximum effects are obtained on the nightside for the pairings By greater than 0, summer and BY less than 0, winter; the first produces the more structured cell in the morning, the second in the evening, and this cell dominates the return flow at midnight. The difference in the zonal flow reversals for these pairings exceeds 4 hr in MLT.

  5. Epithermal Neutron Evidence for a Diurnal Surface Hydration Process in the Moon's High Latitudes

    Science.gov (United States)

    McClanahan, T. P.; Mitrofanov, I. G.; Boynton, W. V.; Chin, G.; Parsons, A.; Starr, R. D.; Evans, L. G.; Sanin, A.; Litvak, M.; Livengood, T.

    2015-01-01

    We report evidence from epithermal neutron flux observations that show that the Moon's high latitude surfaces are being actively hydrated, dehydrated and rehydrated in a diurnal cycle. The near-surface hydration is indicated by an enhanced suppression of the lunar epithermal neutron leakage flux on the dayside of the dawn terminator on poleward-facing slopes (PFS). At 0600 to 0800 local-time, hydrogen concentrations within the upper 1 meter of PFS are observed to be maximized relative to equivalent equator-facing slopes (EFS). During the lunar day surface hydrogen concentrations diminish towards dusk and then rebuild overnight. Surface hydration is determined by differential comparison of the averaged EFS to PFS epithermal neutron count rates above +/- 75 deg latitude. At dawn the contrast bias towards PFS is consistent with at least 15 to 25 parts-per-million (ppm) hydrogen that dissipates by dusk. We review several lines of evidence derived from temperature and epithermal neutron data by a correlated analysis of observations from the Lunar Reconnaissance Orbiter's (LRO) Lunar Exploration Neutron Detector (LEND) that were mapped as a function of lunar local-time, Lunar Observing Laser Altimeter (LOLA) topography and Diviner (DLRE) surface temperature.

  6. The response of pot plants to reduction of energy consumption peaks in greenhouses. [Heating]. Potteplanters reaktion paa udjaevning af energiforbrugs spidser i vaeksthuse

    Energy Technology Data Exchange (ETDEWEB)

    Jacobsen, L.H.; Adriansen, E.; Amsen, M.G.; Nielsen, O.F. (Danish Research Service for Plant and Soil Science, Research Centre for Horticulture, Dept. Hort. Engineering, Institute of Glasshouse Crops, Aarslev (DK))

    1989-01-01

    This experiment was started to avoid difficulties in energy supply, when big areas of greenhouses were connected to district heating. The aim of the experiment was to find ways to reduce energy consumption peaks at dawn and at dusk by means of simple techniques. This paper reports on the results of an experiment where five different pot plants were grown by a temperature control strategy based upon low day and high night room temperature set points (14 deg./22 deg. C) combined with reduced opening speed of the mixing valves. In general it may be concluded that it is possible to produce Chrysanthemum, Begonia, Kalanchoe, Hedera and Ficus with a temperature control strategy which reduces energy consumption peaks at dawn and at dusk without affecting the plant quality. However, it is necessary to apply growth retardants to Chrysanthemum and Kalanchoe to secure a good quality. The production time is reduced for Kalanchoe, increased for Chrysanthemum and Hedera and unchanged for Begonia and Ficus. (author).

  7. MESSENGER observations of the energization and heating of protons in the near-Mercury magnetotail

    Science.gov (United States)

    Sun, W. J.; Raines, J. M.; Fu, S. Y.; Slavin, J. A.; Wei, Y.; Poh, G. K.; Pu, Z. Y.; Yao, Z. H.; Zong, Q. G.; Wan, W. X.

    2017-08-01

    The energization and heating processes for protons in the near-Mercury tail are examined with MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) observations. In a case study, suprathermal proton particle flux (STPF) and proton temperature are observed to be clearly enhanced during near-Mercury substorm dipolarizations, indicating the proton energization and heating processes. STPF and proton temperature distributions in near-Mercury central plasma sheets display dawn-dusk asymmetries, with higher values in the dawnside plasma sheet, i.e., postmidnight, than in the duskside, i.e., premidnight. Further investigations reveal that these asymmetries are more prominent during active periods in Mercury's magnetosphere, as compared to quiet periods. Magnetic field variations in the ZMSM component display a similar feature, with variations being more prominent on the dawnside than the duskside during active periods. We propose that the dawn-dusk asymmetry in the distributions of protons could be due to the fact that more substorm dipolarizations were initiated on the dawnside of Mercury's magnetotail.

  8. MESSENGER Orbital Observations of Large-Amplitude Kelvin-Helmholtz Waves at Mercury's Magnetopause

    Science.gov (United States)

    Sundberg, Torbjorn; Boardsen, Scott A.; Slavin, James A.; Anderson, Brian J.; Korth, Haje; Zurbuchen, Thomas H.; Raines, Jim M.; Solomon, Sean C.

    2012-01-01

    We present a survey of Kelvi\\ n-Helmholtz (KH) waves at Mercury's magnetopause during MESSENGER's first Mercury year in orb it. The waves were identified on the basis of the well-established sawtooth wave signatures that are associated with non-linear KH vortices at the magnetopause. MESSENGER frequently observed such KH waves in the dayside region of the magnetosphere where the magnetosheath flow velocity is still sub -sonic, which implies that instability growth rates at Mercury's magnetopau are much larger than at Earth. We attribute these greater rates to the limited wave energy dissipation in Mercury's highly resistive regolith. The wave amplitude was often on the order of ' 00 nT or more, and the wave periods were - 10- 20 s. A clear dawn-dusk asymmetry is present in the data, in that all of the observed wave events occurred in the post-noon and dusk-side sectors of the magnetopause. This asymmetry is like ly related to finite Larmor-radius effects and is in agreement with results from particle-in-cell simulations of the instability. The waves were observed almost exclusively during periods when the north-south component of the magnetosheath magnetic field was northward, a pattern similar to that for most terrestrial KH wave events. Accompanying plasma measurements show that the waves were associated with the transport of magnetosheath plasma into the magnetosphere.

  9. Spatial Distribution of Rolled up Kelvin-Helmholtz Vortices at Earth's Dayside and Flank Magnetopause

    Science.gov (United States)

    Taylor, M. G. G. T.; Hasegawa, H.; Lavraud, B.; Phan, T.; Escoubet, C. P.; Dunlop, M. W.; Bogdanova, Y. V.; Borg, A. L.; Volwerk, M.; Berchem, J.; Constantinescu, O. D.; Eastwood, J. P.; Masson, A.; Laakso, H.; Soucek, J.; Fazakerley, A. N.; Frey, H. U.; Panov, E. V.; Shen, C.; Shi, J. K.; Sibeck, D. G.; Pu, Z. Y.; Wang, J.; Wild, J. A.

    2012-01-01

    The Kelvin-Helmholtz Instability (KHI) can drive waves at the magnetopause. These waves can grow to form rolled-up vortices and facilitate transfer of plasma into the magnetosphere. To investigate the persistence and frequency of such waves at the magnetopause we have carried out a survey of all Double Star 1 magnetopause crossings, using a combination of ion and magnetic field measurements. Using criteria originally used in a Geotail study made by Hasegawa et al. (2006) (forthwith referred to as H2006), 17 candidate events were identified from the entire TC-1 mission (covering 623 orbits where the magnetopause was sampled), a majority of which were on the dayside of the terminator. The relationship between density and shear velocity was then investigated, to identify the predicted signature of a rolled up vortex from H2006 and all 17 events exhibited some level of rolled up behavior. The location of the events had a clear dawn-dusk asymmetry, with 12 (71 %) on the post noon, dusk flank suggesting preferential growth in this region.

  10. Machine vision for airport runway identification

    Science.gov (United States)

    Schubert, Matthew; Moore, Andrew J.; Dolph, Chester; Woodell, Glenn

    2015-03-01

    For rigid objects and fixed scenes, current machine vision technology is capable of identifying imagery rapidly and with specificity over a modest range of camera viewpoints and scene illumination. We applied that capability to the problem of runway identification using video of sixteen runway approaches at nine locations, subject to two simplifying assumptions. First, by using approach video from just one of the several possible seasonal variations (no snow cover and full foliage), we artificially removed one source of scene variation in this study. Secondly, by not using approach video at dawn and dusk, we limited the study to two illumination variants (day and night). We did allow scene variation due to atmospheric turbidity by using approach video from rainy and foggy days in some daytime approaches. With suitable ensemble statistics to account for temporal continuity in video, we observed high location specificity (<90% Bayesian posterior probability). We also tested repeatability, i.e., identification of a given runway across multiple videos, and observed robust repeatability only if illumination (day vs. night) was the same and approach visibility was good. Both specificity and repeatability degraded in poor weather conditions. The results of this simplified study show that geolocation via real-time comparison of cockpit image sensor video to a database of runway approach imagery is feasible, as long as the database contains imagery from about the same time of day (complete daylight and nighttime, excluding dawn and dusk) and the weather is clear at the time of the flight.

  11. Investigation of S3-2 satellite data for local time variation of energetic electron precipitation

    Science.gov (United States)

    Robbe, S.; Sheldon, W. R.; Benbrook, J. R.; Bering, E. A.; Vampola, A. L.

    1994-01-01

    Data on precipitating electrons from the S3-2 satellite were investigated for local time variation at four L = 4 stations in the southern hemisphere. The equatorial pitch angles of electrons mirroring at 100 km, assumed to be the edge of the bounce loss cone, are calculated for L = 4 using the International Geomagnetic Reference Field for the epoch of the S3-2 data, along with the variation in mirror altitude per degree of equatorial pitch angle. The largest obstacle to the investigation was uneven sampling in terms of local time for all of the stations. However, this situation was improved upon by the use of S3-2 measurements at the conjugate locations of the four stations which provided additional data on electrons in the southern hemisphere bounce loss cone. Evidence for an effect of the dawn-to-dusk geoelectric field was found at two of the stations, Halley Bay and Siple, in the form of a minimum in electron precipitation at dusk. However, the present study does not completely resolve the question of local time modulation of electron precipitation at L = 4 in the southern hemisphere. Furthermore, while the average precipitation was lowest at the Kerguelen site, as would be expected on the basis of drift loss cone (DLC) theories, the intensity at that site exceeds the level that is expected on the basis of these DLC theories.

  12. Ramadan fasting and patients with renal diseases: A mini review of the literature.

    Science.gov (United States)

    Emami-Naini, Afsoon; Roomizadeh, Peyman; Baradaran, Azar; Abedini, Amin; Abtahi, Mohammad

    2013-08-01

    Fasting during the month of Ramadan is one of the five pillars of Islam. During this month, adult Muslims are obligated to refrain from eating and drinking from dawn to dusk. Although based on Islamic principles patients are exempted from fasting, each year, many Muslim patients express their willingness to observe the fast in Ramadan month to respect the cultural customs. There are concerns about the impact of fluid restriction and dehydration during Ramadan fasting for patients with renal diseases. In this study, we reviewed the PubMed, Google Scholar, EBSCO, SCIRUS, Embase, and DOAJ data sources to identify the published studies on the impact of Ramadan fasting on patients with renal diseases. Our review on published reports on renal transplant recipients revealed no injurious effect of Ramadan fasting for the renal graft function. Nearly all studies on this topic suggest that Ramadan fasting is safe when the function of the renal graft is acceptable and stable. Regarding the impact of Ramadan fasting on patients with chronic kidney disease, there is concern about the role of renal hypoperfusion in developing tubular cell injury. Finally, there is controversy between studies about the risk of dehydration in Ramadan in developing renal stones. There are uncertainties about the change in the incidence of renal colic in Ramadan month compared with the other periods of the year. Despite such discrepancies, nearly all studies are in agreement on consuming adequate amounts of water from dusk to dawn to reduce the risk of renal stone formation.

  13. Vasoactive intestinal polypeptide mediates circadian rhythms in mammalian olfactory bulb and olfaction.

    Science.gov (United States)

    Miller, Jae-Eun Kang; Granados-Fuentes, Daniel; Wang, Thomas; Marpegan, Luciano; Holy, Timothy E; Herzog, Erik D

    2014-04-23

    Accumulating evidence suggests that the olfactory bulbs (OBs) function as an independent circadian system regulating daily rhythms in olfactory performance. However, the cells and signals in the olfactory system that generate and coordinate these circadian rhythms are unknown. Using real-time imaging of gene expression, we found that the isolated olfactory epithelium and OB, but not the piriform cortex, express similar, sustained circadian rhythms in PERIOD2 (PER2). In vivo, PER2 expression in the OB of mice is circadian, approximately doubling with a peak around subjective dusk. Furthermore, mice exhibit circadian rhythms in odor detection performance with a peak at approximately subjective dusk. We also found that circadian rhythms in gene expression and odor detection performance require vasoactive intestinal polypeptide (VIP) or its receptor VPAC2R. VIP is expressed, in a circadian manner, in interneurons in the external plexiform and periglomerular layers, whereas VPAC2R is expressed in mitral and external tufted cells in the OB. Together, these results indicate that VIP signaling modulates the output from the OB to maintain circadian rhythms in the mammalian olfactory system.

  14. 3D PIC Simulation of the Magnetosphere during IMF Rotation from North to South: Signatures of Substorm Triggering in the Magnetotail

    Science.gov (United States)

    Nishikawa, Ken-Ichi; Cao. D/ S/; Lembege, B.

    2008-01-01

    Three dimensional PIC simulations are performed in order to analyse the dynamics of the magnetotail as the interplanetary magnetic field (IMF) rotates from northward to southward direction. This dynamics reveals to be quite different within meridian/equatorial planes over two successive phases of this rotation. First, as IMF rotates from North to Dawn-Dusk direction, the X-Point (magnetic reconnection) evidenced in the magnetotail (meridian plane) is moving earthward (from x=-35 Re to x=-17.5 ) distance at which it stabilizes. This motion is coupled with the formation of "Crosstail-S" patterns (within the plane perpendicular to the Sun-Earth mine) through the neutral sheet in the nearby magnetotail. Second, as IMF rotates from dawn-dusk to South, the minimum B field region is expanding within the equatorial plane and forms a ring. This two-steps dynamics is analyzed in strong association with the cross field magnetotail current Jy, in order to recover the signatures of substorms triggering.

  15. Enabling photoperiodic control of flowering by timely chromatin silencing of the florigen gene.

    Science.gov (United States)

    He, Yuehui

    2015-01-01

    Many plants synchronize their flowering times with changing seasons to maximize reproductive success. A key seasonal cue is the change in day length (photoperiod), that induces the production of a systemic flowering signaling molecule called florigen. A major florigen component is FLOWERING LOCUS T (FT) or its orthologs. In the long-day plant Arabidopsis thaliana, FT expression is well known to be activated by the photoperiod pathway output specifically near dusk in long days; however, underappreciated is the importance of FT silencing at other times of the day, in enabling Arabidopsis to respond only to long days in flowering. We have recently reported that a plant-specific chromatin-silencing complex called EMF1c represses FT expression at times other than around dusk in long days to prevent its temporal ectopic expression from "spoiling" the long-day floral induction in Arabidopsis. Here I further discuss in other day-length sensitive plants the potential involvement of a chromatin mechanism similar to the Arabidopsis EMF1c-mediated silencing, in repressing the expression of FT orthologs to enable diverse photoperiodic control of flowering.

  16. The search for Ar in the lunar atmosphere using the Lunar Reconnaissance Orbiter's LAMP instrument.

    Science.gov (United States)

    Cook, J. C.; Stern, S. A.; Feldman, P. D.; Gladstone, R.; Retherford, K. D.; Greathouse, T. K.; Grava, C.

    2014-12-01

    The Apollo 17 mass spectrometer, LACE, first measured mass 40 particles in the lunar atmosphere, and over a nine-month period, detected variations correlated with the lunar day (Hoffman et al., 1973, LPSC, 4, 2865). LACE detected a high particle density at dusk (0.6-1.0x104 cm-3), decreasing through the lunar night to a few hundred cm-3, then increasing rapidly before dawn to levels 2-4 times greater than at dusk. No daytime measurements were made due to instrument saturation. Given the LACE measurements' periodic nature, and the Ar abundance in lunar regolith samples (Kaiser, 1972, EPSL, 13, 387), it was concluded that mass 40 was likely due to Ar. Benna et al. (2014, LPSC, 45, 1535) recently reported that the Neutral Mass Spectrometer (NMS) aboard LADEE also detected Ar (mass 40) with similar diurnal profiles. We report on UV spectra of the lunar atmosphere as obtained by the Lunar Reconnaissance Orbiter (LRO). Aboard LRO is the UV-spectrograph, LAMP (Lyman Alpha Mapping Project), spanning the spectral range 575 to 1965 Å. LAMP is typically oriented toward the surface and has been mapping the Moon since September 2009. LAMP also observes the tenuous lunar atmosphere when the surface is in darkness, but the atmospheric column below LRO is illuminated. We have previously used nadir oriented twilight observations to examine the sparse lunar atmosphere (Feldman et al., 2012, Icarus, 221, 854; Cook et al., 2013, Icarus, 225, 681; Stern et al., 2013, Icarus, 226, 1210; Cook & Stern 2014, Icarus, 236, 48). In Cook et al., 2013, we reported an upper limit for Ar of 2.3x104 cm-3. Since then, we have collected additional data and refined our search method by focusing on the regions (near equator) and local times (dawn and dusk) where Ar has been reported previously. We have carefully considered effective area calibration and g-factor accuracies and find these to be unlikely explanations for the order of magnitude differences. We will report new results, which provide much

  17. An Investigation of Trajectories of Atoms in Mercury's Exosphere

    Science.gov (United States)

    Bradley, Eric Todd

    2016-10-01

    Mercury's neutral exosphere consists of atoms or molecules ejected from the surface that are on individual trajectories that may re-impact the surface if there is insufficient energy to escape the gravity of the planet. This is an investigation of how the radiation pressure, orbital acceleration of the planet, and planetary rotation combine together to produce complicated trajectories. Because of Mercury's non-zero eccentricity the planet is not in uniform circular motion, which leads to radial and tangential accelerations that vary throughout the Mercury year. Besides radiation pressure the trajectory of an exospheric atom is affected by the planet accelerating during the time of flight of the atom that 1) causes the atom's position with respect to the ejection point to vary in a manner that is different than if the planet were not accelerating and 2) causes the planet-atom distance to vary in a manner that is different than for a typical ballistic trajectory resulting in variation of the gravitational force that the planet exerts on the atom. These effects are small but persistent and affect where the atom re-impacts the surface, which may lead to asymmetrical distributions of atoms in the surface regolith and exosphere.Preliminary results from simulations of ejected atoms that include 1) radiation pressure that varies with the atom's velocity due to Doppler shifting, 2) radial and tangential accelerations of the planet, and 3) the variation of the planet's gravity on the atom with distance above the planet show that atoms ejected at low energies normal to the surface from the subsolar point re-impact on the dusk side hemisphere of the planet. However atoms ejected at high energies normal to the surface from the subsolar point re-impact on the dawn side hemisphere of the planet. A fraction of atoms ejected normal to the surface from the dawn terminator within an energy range that results in the atom re-impacting and sticking to the night side surface behind the

  18. Elements of M-I Coupling in Repetitive Substorm Activity Driven by Interplanetary CMEs

    Science.gov (United States)

    Farrugia, C. J.; Sandholt, P. E.

    2014-12-01

    By means of case studies we explore key elements of the magnetosphere-ionosphere current system associated with repetitive substorm activity during persistent strong forcing by ICMEs. Our approach consists of a combination of the magnetospheric and ionospheric perspectives on the substorm activity. The first aspect is the near-Earth plasma sheet with its repetitive excitations of the substorm current wedge, as monitored by spacecraft GOES-10 when it traversed the 2100-0300 MLT sector, and its coupling to the westward auroral electrojet (WEJ) centered near midnight during the stable interplanetary (IP) conditions. The second aspect is the excitation of Bostrom type II currents maximizing at dusk and dawn and their associated ionospheric Pedersen current closure giving rise to EEJ (WEJ) events at dusk (dawn). As documented in our study, this aspect is related to the braking phase of Earthward-moving dipolarization fronts-bursty bulk flows. We follow the magnetospheric flow/field events from spacecraft Geotail in the midtail (X = - 11 Re) lobe to geostationary altitude at pre-dawn MLTs (GOES 10). The associated M-I coupling is obtained from ground-satellite conjunctions across the double auroral oval configuration along the meridian at dusk. By this technique we distinguish between ionospheric manifestations in three latitude regimes: (i) auroral oval south, (ii) auroral oval north, and (iii) polar cap. Regime (iii) is characterized by events of enhanced antisunward convection near the polar cap boundary (flow channel events) and in the central polar cap (PCN-index events). The repetitive substorm activity is discussed in the context of the level of IP driving as given by the geoeffective IP electric field (E_KL), magnetotail reconnection (inferred from the PCN-index and spacecraft Wind at X = - 77 Re) and the storm SYM-H index. We distinguish between different variants of the repetitive substorm activity, giving rise to electrojet (AL)-plasma convection (PCN) events

  19. Polar cap convection/precipitation states during Earth passage of two ICMEs at solar minimum

    Directory of Open Access Journals (Sweden)

    P. E. Sandholt

    2010-04-01

    Full Text Available We report important new aspects of polar cap convection and precipitation (dawn-dusk and inter-hemisphere asymmetries associated with the different levels of forcing of the magnetosphere by two interplanetary (IP magnetic clouds on 20 November 2007 and 17 December 2008 during solar minimum. Focus is placed on two intervals of southward magnetic cloud field with large negative By components (Bx=−5 versus 0 nT and with high and low plasma densities, respectively, as detected by spacecraft Wind. The convection/precipitation states are documented by DMSP spacecraft (Southern Hemisphere and SuperDARN radars (Northern Hemisphere. The (negative By component of the cloud field is accompanied by a newly-discovered flow channel (called here FC 2 threaded by old open field lines (in polar rain precipitation at the dusk and dawn sides of the polar cap in the Northern and Southern Hemispheres, respectively, and a corresponding Svalgaard-Mansurov (S-M effect in ground magnetic deflections. On 20 November 2007 the latter S-M effect in the Northern winter Hemisphere appears in the form of a sequence of six 5–10 min long magnetic deflection events in the 71–74° MLAT/14:30–16:00 MLT sector. The X-deflections are consistent with the flow direction in FC 2 (i.e. caused by Hall currents in both IP cloud cases. The presence of a lobe cell and associated polar arcs in the Southern (summer Hemisphere in the low density (1–2 cm−3 and Bx=0 ICME case is accompanied by the dropout of polar rain precipitation in the dusk-side regime of sunward polar cap convection and inward-directed Birkeland current. The low-altitude observations are discussed in terms of momentum transfer via dynamo processes in the high- and low-latitude boundary layers and Birkeland currents located poleward of the traditional R1-R2 system.

  20. Ionospheric feedback effects on the quasi-stationary coupling between LLBL and postnoon/evening discrete auroral arcs

    Directory of Open Access Journals (Sweden)

    M. M. Echim

    2008-05-01

    Full Text Available We discuss a model for the quasi-stationary coupling between magnetospheric sheared flows in the dusk sector and discrete auroral arcs, previously analyzed for the case of a uniform height-integrated Pedersen conductivity (ΣP. Here we introduce an ionospheric feedback as the variation of ΣP with the energy flux of precipitating magnetospheric electrons (εem. One key-component of the model is the kinetic description of the interface between the duskward LLBL and the plasma sheet that gives the profile of Φm, the magnetospheric electrostatic potential. The velocity shear in the dusk LLBL plays the role of a generator for the auroral circuit closing through Pedersen currents in the auroral ionosphere. The field-aligned current density, j||, and the energy flux of precipitating electrons are given by analytic functions of the field-aligned potential drop, ΔΦ, derived from standard kinetic models of the adiabatic motion of particles. The ionospheric electrostatic potential, Φi (and implicitely ΔΦ is determined from the current continuity equation in the ionosphere. We obtain values of ΔΦ of the order of kilovolt and of j|| of the order of tens of μA/m2 in thin regions of the order of several kilometers at 200 km altitude. The spatial scale is significantly smaller and the peak values of ΔΦ, j|| and εem are higher than in the case of a uniform ΣP. Effects on the postnoon/evening auroral arc electrodynamics due to variations of dusk LLBL and solar wind dynamic and kinetic pressure are discussed. In thin regions (of the order of kilometer embedding the maximum of ΔΦ we evidence a non-linear regime of the current-voltage relationship. The model predicts also that visible arcs form when the velocity shear in LLBL is above a threshold value depending on the generator and

  1. A model of the plasma flow and current in Saturn's polar ionosphere under conditions of strong Dungey cycle driving

    Directory of Open Access Journals (Sweden)

    C. M. Jackman

    2006-05-01

    Full Text Available We propose a simple model of the flow and currents in Saturn's polar ionosphere. This model is motivated by theoretical reasoning, and guided quantitatively by in situ field and flow data from space missions, ground-based IR Doppler measurements, and Hubble Space Telescope images. The flow pattern consists of components which represent (1 plasma sub-corotation in the middle magnetosphere region resulting from plasma pick-up and radial transport from internal sources; (2 the Vasyliunas-cycle of internal plasma mass-loss down the magnetospheric tail at higher latitudes; and (3 the polar Dungey-cycle flow driven by the solar wind interaction. Upstream measurements of the interplanetary magnetic field (IMF indicate the occurrence of both extended low-field rarefaction intervals with essentially negligible Dungey-cycle flow, and few-day high-field compression regions in which the Dungey-cycle voltage peaks at a few hundred kV. Here we model the latter conditions when the Dungey-cycle is active, advancing on previous axi-symmetric models which may be more directly applicable to quiet conditions. For theoretical convenience the overall flow pattern is constructed by adding together two components - a purely rotational flow similar to previous axi-symmetric models, and a sun-aligned twin vortex representing the dawn-dusk asymmetry effects associated with the Vasyliunas-and Dungey-cycle flows. We calculate the horizontal ionospheric current associated with the flow and the field-aligned current from its divergence. These calculations show that a sheet of upward-directed field-aligned current flows at the boundary of open field lines which is strongly modulated in local-time by the Dungey-cycle flows. We then consider implications of the field-aligned current for magnetospheric electron acceleration and aurorae using two plasma source populations (hot outer magnetospheric electrons and cool dense magnetosheath electrons. Both sources display a

  2. Substorms and polar cap convection: the 10 January 2004 interplanetary CME case

    Directory of Open Access Journals (Sweden)

    Y. Andalsvik

    2012-01-01

    Full Text Available The expansion-contraction model of Dungey cell plasma convection has two different convection sources, i.e. reconnections at the magnetopause and in the magnetotail. The spatial-temporal structure of the nightside source is not yet well understood. In this study we shall identify temporal variations in the winter polar cap convection structure during substorm activity under steady interplanetary conditions. Substorm activity (electrojets and particle precipitations is monitored by excellent ground-satellite DMSP F15 conjunctions in the dusk-premidnight sector. We take advantage of the wide latitudinal coverage of the IMAGE chain of ground magnetometers in Svalbard – Scandinavia – Russia for the purpose of monitoring magnetic deflections associated with polar cap convection and substorm electrojets. These are augmented by direct observations of polar cap convection derived from SuperDARN radars and cross-track ion drift observations during traversals of polar cap along the dusk-dawn meridian by spacecraft DMSP F13. The interval we study is characterized by moderate, stable forcing of the magnetosphere-ionosphere system (EKL = 4.0–4.5 mV m−1; cross polar cap potential (CPCP, Φ (Boyle = 115 kV during Earth passage of an interplanetary CME (ICME, choosing an 4-h interval where the magnetic field pointed continuously south-west (Bz < 0; By < 0. The combination of continuous monitoring of ground magnetic deflections and the F13 cross-track ion drift observations in the polar cap allows us to infer the temporal CPCP structure on time scales less than the ~10 min duration of F13 polar cap transits. We arrived at the following estimates of the dayside and nightside contributions to the CPCP (CPCP = CPCP/day + CPCP/night under two intervals of substorm activity: CPCP/day ~110 kV; CPCP/night ~50 kV (45% CPCP increase during substorms. The temporal CPCP structure during one of the

  3. ABC 27-2 General bat activity measured with an ultrasound detector in a fragmented tropical landscape in Los Tuxtlas, Mexico

    Directory of Open Access Journals (Sweden)

    Estrada, A.

    2004-12-01

    Full Text Available Bat tolerance to neotropical forest fragmentation may be related to ability by bats to use available habitats in the modified environmental matrix. This paper presents data on general bat activity (for three hours starting at dusk measured with an ultrasound detector in a fragmented landscape in the region of Los Tuxtlas, Mexico. Bat activity was measured in continuous forests, forests fragments, forest-pasture edges, forest corridors, linear strips of vegetation, citrus groves, pastures and the vegetation present in local villages. The highest bat activity rates were recorded in the villages, in the forest fragments and in linear strips of vegetation. The lowest activity rates were detected in pasture habitats. Data suggest that native and man-made arboreal vegetation may be important for sustaining bat activity in fragmented landscapes.

  4. Charged particle acceleration by induction electric field in Neptune magnetotail

    Science.gov (United States)

    Vasko, I. Y.; Malova, H. V.; Artemyev, A. V.; Zelenyi, L. M.

    2012-12-01

    The precession of the Neptune magnetic dipole leads to strong dynamics of the magnetosphere and results in continuous transformation from the “Earth-like” configuration to the “pole-on” one and vice versa. In the present work we use simple model of the Neptune magnetotail to investigate the influence of magnetotail topology transformation on particle acceleration and transport through the tail. Energy spectra are obtained for protons penetrating from the solar wind and heavier ions N+ from the Neptune ionosphere. We have found that protons and heavier ions are accelerated up to ∼330 keV and ∼150 keV, respectively. More particles are accelerated and leave the tail during transformations from the “pole-on” configuration to the “Earth-like” one than during inverse transformations. We have shown that the dusk-dawn convection field is responsible for particle leaving through the dawn flank. We briefly compare our results with Voyager-2 observations.

  5. Markovian Building Blocks for Individual-Based Modelling

    DEFF Research Database (Denmark)

    Nilsson, Lars Anders Fredrik

    2007-01-01

    The present thesis consists of a summary report, four research articles, one technical report and one manuscript. The subject of the thesis is individual-based stochastic models. The summary report is composed of three parts and a brief history of some basic models in population biology....... This history is included in order to provide a reader that has no previous exposure to models in population biology with a sufficient background to understand some of the biological models that are mentioned in the thesis. The first part of the rest of the summary is a description of the dramatic changes...... in the degree of aggregation of sprat or herring in the Baltic during the day, with special focus on the dispersion of the fish from schools at dusk. The next part is a brief introduction to Markovian arrival processes, a type of stochastic processes with potential applications as sub-models in population...

  6. Solar Wind Driving of Magnetospheric ULF Waves: Pulsations Driven by Velocity Shear at the Magnetopause

    CERN Document Server

    Claudepierre, S G; Wiltberger, M; 10.1029/2007JA012890

    2010-01-01

    We present results from global, three-dimensional magnetohydrodynamic (MHD) simulations of the solar wind/magnetosphere interaction. These MHD simulations are used to study ultra low frequency (ULF) pulsations in the Earth's magnetosphere driven by shear instabilities at the flanks of the magnetopause. We drive the simulations with idealized, constant solar wind input parameters, ensuring that any discrete ULF pulsations generated in the simulation magnetosphere are not due to fluctuations in the solar wind. The simulations presented in this study are driven by purely southward interplanetary magnetic field (IMF) conditions, changing only the solar wind driving velocity while holding all of the other solar wind input parameters constant. We find surface waves near the dawn and dusk flank magnetopause and show that these waves are generated by the Kelvin-Helmholtz (KH) instability. We also find that two KH modes are generated near the magnetopause boundary. One mode, the magnetopause KH mode, propagates tailwa...

  7. Home range and activity of African goshawks Accipiter tachiro in relation to their predation on bats

    Directory of Open Access Journals (Sweden)

    I.L. Rautenbach

    1990-09-01

    Full Text Available Winter radio-tracking of three African goshawks Accipiter tachiro showed that they each occupied well-wooded home ranges of at least 28 hectares. They perched and roosted mainly within densely foliaged trees and an adult female changed perches on average 4,7 times per hour. No crepuscular predation of bats was recorded, in contrast to regular summer predation on colonies of little free-tailed bats, Tadarida pumila, but winter emergence rates of these bats at dusk had dropped to < 5 of the previous summer. We predict that many accipiters will be regular predators of bats and that skewed sex ratios and high fecundity may be two means by which bats counter this predation.

  8. Toward a political analysis of the consequences of a world climate change produced by increasing atmospheric carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Schware, R.

    1980-01-01

    It was Hegel's extraordinarily deep and perceptive insight that mankind is caught up in a drama that cannot be fully understood until it has been played out. The owl of Minewa spreads its wings only with the falling of the dusk. On the more hopeful side is the fact that, although we cannot know the consequences of future interactions between climate and society, we can begin to work toward political solutions and gird ourselves for ominous trends that are now coming into view. The purpose of this paper is to identify one such trend, namely the increase of atmospheric temperatures due to increased carbon dioxide (CO/sub 2/) and lay some initial groundwork for political research related to climate-societal interactions.

  9. PDF-modulated visual inputs and cryptochrome define diurnal behavior in Drosophila.

    Science.gov (United States)

    Cusumano, Paola; Klarsfeld, André; Chélot, Elisabeth; Picot, Marie; Richier, Benjamin; Rouyer, François

    2009-11-01

    Morning and evening circadian oscillators control the bimodal activity of Drosophila in light-dark cycles. The lateral neurons evening oscillator (LN-EO) is important for promoting diurnal activity at dusk. We found that the LN-EO autonomously synchronized to light-dark cycles through either the cryptochrome (CRY) that it expressed or the visual system. In conditions in which CRY was not activated, flies depleted for pigment-dispersing factor (PDF) or its receptor lost the evening activity and displayed reversed PER oscillations in the LN-EO. Rescue experiments indicated that normal PER cycling and the presence of evening activity relied on PDF secretion from the large ventral lateral neurons and PDF receptor function in the LN-EO. The LN-EO thus integrates light inputs and PDF signaling to control Drosophila diurnal behavior, revealing a new clock-independent function for PDF.

  10. Crassulacean acid metabolism enhances underwater photosynthesis and diminishes photorespiration in the aquatic plant Isoetes australis

    DEFF Research Database (Denmark)

    Pedersen, Ole; Rich, S.M.; Pulido Pérez, Cristina

    2011-01-01

    Underwater photosynthesis by aquatic plants is often limited by low availability of CO2, and photorespiration can be high. Some aquatic plants utilize crassulacean acid metabolism (CAM) photosynthesis. The benefits of CAM for increased underwater photosynthesis and suppression of photorespiration...... were evaluated for Isoetes australis, a submerged plant that inhabits shallow temporary rock pools. • Leaves high or low in malate were evaluated for underwater net photosynthesis and apparent photorespiration at a range of CO2 and O2 concentrations. • CAM activity was indicated by 9.7-fold higher leaf...... malate at dawn, compared with at dusk, and also by changes in the titratable acidity (lmol H+ equivalents) of leaves. Leaves high in malate showed not only higher underwater net photosynthesis at low external CO2 concentrations but also lower apparent photorespiration. Suppression by CAM of apparent...

  11. On the origin of pre-reversal enhancement of the zonal equatorial electric field

    Directory of Open Access Journals (Sweden)

    M. C. Kelley

    2009-05-01

    Full Text Available In November 2004, a large and variable interplanetary electric field (IEF was felt in the reference frame of the Earth. This electric field penetrated to the magnetic equator and, when the Jicamarca Radio Observatory (JRO was in the dusk sector, resulted in a reversal of the normal zonal component of the field. In turn, this caused a counter-electrojet (CEJ, a westward current rather than the usual eastward current. At the time of the normal pre-reversal enhancement (PRE of the eastward field, the Jicamarca incoherent scatter radar (ISR observed that the westward component became even more westward. Two of the three current explanations for the PRE depend on the neutral wind patterns. However, this unique event was such that the neutral wind-driven dynamos could not have changed. The implication is that the Haerendel-Eccles mechanism, which involves partial closure of the equatorial electrojet (EEJ after sunset, must be the dominant mechanism for the PRE.

  12. A comparison of the radio data and model calculations of Jupiter's synchrotron radiation. I - The high energy electron distribution in Jupiter's inner magnetosphere. II - East-west asymmetry in the radiation belts as a function of Jovian longitude

    Science.gov (United States)

    De Pater, I.

    1981-01-01

    A comparison has been made between detailed model calculations of Jupiter's synchrotron radiation and the radio data at wavelengths of 6, 21, and 50 cm. The calculations were performed for a Jovian longitude of 200 deg and were based on the multipole field configurations as derived from the Pioneer data. The electron distribution in the inner magnetosphere was derived as a function of energy, pitch angle, and spatial coordinates. In addition, the hot region or east-west asymmetry in the radiation belts is investigated. It is suggested that this asymmetry is due to the combined effect of an overabundance of electrons at jovicentric longitudes of 240-360 deg and the existence of a dusk-to-dawn directed electric field over the inner magnetosphere generated by the wind system in the upper atmosphere.

  13. Reading and My Life

    Institute of Scientific and Technical Information of China (English)

    徐娟

    2005-01-01

    @@ Reading has accompanied me for many years, from1 a pupil to an undergraduate. It enriches my life, and the most significant2 is that it teaches me how to live. Reading instructs me to treat life unperturbedly(泰然自若地). There is such a story.3 An angler(钓鱼者) went fishing in the early morning and came back at dusk without any fish, He spent the whole day but gained nothing. However, he was blissful(有福的). To the angler, it's none of his business for fish doesn't bite the baits4, but5 what he has angled is happiness. We live calmly and confidently, so we can get delightful experiences.

  14. Chromolaena odorata (L. King & H.E. Robins (Asteraceae, an important nectar source for adult butterflies

    Directory of Open Access Journals (Sweden)

    P.V. Lakshmi

    2011-02-01

    Full Text Available Chromolaena odorata is a seasonal weed and grows like a cultivated crop. It flowers during October-December. The floral characteristics such as white to purple colour of florets, short-tubed narrow corolla with deep seated nectar, the morning anthesis and the flat-topped head inflorescence providing a standing platform are important attractants for visitation by butterflies. The florets attract butterflies of five families and sphingid hawk moths. Among the butterflies, nymphalids are diverse and visit the florets consistently; their visits effect pollination. The diurnal hawk moths, Macroglossum gyrans and Cephonodes hylas also visit the florets during dawn and dusk hours for nectar, and effect pollination. Therefore, C. odorata, being an exotic is an important nectar source for adult butterflies.

  15. Circadian light input in plants, flies and mammals.

    Science.gov (United States)

    Panda, Satchidananda; Hogenesch, John B; Kay, Steve A

    2003-01-01

    The rotation of our planet results in daily changes in light and darkness, as well as seasons with characteristic photoperiods. Adaptation to these daily and seasonal changes in light properties (and associated changes in the environment) is important to the sustained survival of higher life forms on our planet. Many organisms use their intrinsic circadian oscillator or clock to orchestrate daily rhythms in behaviour and physiology to adapt to diurnal changes. Some higher organisms use the same oscillator to monitor day length in selecting the appropriate season for reproductive behaviour. Organisms have developed irradiance measurement mechanisms to ignore photic noise (lightning, moonlight), and use the light of dusk and dawn for circadian photoentrainment. They have also devised multiple photoreceptors and signalling cascades to buffer against changes in the spectral composition of natural light. The interaction of the clock with ambient light is, therefore, quite intricate.

  16. Ionospheric convection response to changes of interplanetary magnetic field B-z component during strong B-y component

    DEFF Research Database (Denmark)

    Huang, C.S.; Murr, D.; Sofko, G.J.

    2000-01-01

    enough, the B-z reorientation causes changes in the flow intensity but not in the shape of the convection pattern. The results show the characteristics of ionospheric convection response during strong B-y and suggest that the convection reconfiguration is not only determined by the changing B-z but also...... the dawn-dusk meridian plane, which is interpreted as propagation or expansion of newly generated convection cells in the cusp region. Other studies showed that the change in convection pattern in response to IMF reorientations is spatially fixed. In this paper, we investigate the ionospheric convection...... response to IMF Bz changes during strong IMF BZ. On March 23, 1995, B-x was small, B-y was strongly positive (7-11 nT), and the B-z polarity changed several times after 1300 UT. The dayside ionospheric convection is dominated by a large clockwise convection cell. The cell focus (the "eye" of the convection...

  17. Asymmetric auroral intensities in the Earth's Northern and Southern hemispheres

    Science.gov (United States)

    Laundal, K. M.; Østgaard, N.

    2009-07-01

    It is commonly assumed that the aurora borealis (Northern Hemisphere) and aurora australis (Southern Hemisphere) are mirror images of each other because the charged particles causing the aurora follow the magnetic field lines connecting the two hemispheres. The particles are believed to be evenly distributed between the two hemispheres, from the source region in the equatorial plane of the magnetosphere. Although it has been shown that similar auroral features in the opposite hemispheres can be displaced tens of degree in longitude and that seasonal effects can cause differences in global intensity, the overall auroral patterns were still similar. Here we report observations that clearly contradict the common assumption about symmetric aurora: intense spots are seen at dawn in the Northern summer Hemisphere, and at dusk in the Southern winter Hemisphere. The asymmetry is interpreted in terms of inter-hemispheric currents related to seasons, which have been predicted but hitherto had not been seen.

  18. Distribution of energetic oxygen and hydrogen in the near-Earth plasma sheet

    CERN Document Server

    Kronberg, E A; Haaland, S E; Daly, P W; Delcourt, D C; Luo, H; Kistler, L M; Dandouras, I

    2016-01-01

    The spatial distributions of different ion species are useful indicators for plasma sheet dynamics. In this statistical study based on 7 years of Cluster observations, we establish the spatial distributions of oxygen ions and protons at energies from 274 to 955 keV, depending on geomagnetic and solar wind (SW) conditions. Compared with protons, the distribution of energetic oxygen has stronger dawn-dusk asymmetry in response to changes in the geomagnetic activity. When the interplanetary magnetic field (IMF) is directed southward, the oxygen ions show significant acceleration in the tail plasma sheet. Changes in the SW dynamic pressure ($\\mathit{P}_{dyn}$) affect the oxygen and proton intensities in the same way. The energetic protons show significant intensity increases at the near-Earth duskside during disturbed geomagnetic conditions, enhanced SW $\\mathit{P}_{dyn}$, and southward IMF, implying there location of effective inductive acceleration mechanisms and a strong duskward drift due to the increase of t...

  19. High-Latitude Ionospheric Dynamics During Conditions of Northward IMF

    Science.gov (United States)

    Sharber, J. R.

    1996-01-01

    In order to better understand the physical processes operating during conditions of northward interplanetary magnetic field (IMF), in situ measurements from the Dynamics Explorer-2 (low altitude) polar satellite and simultaneous observations from the auroral imager on the Dynamics Explorer-1 (high altitude) satellite were used to investigate the relationships between optical emissions, particle precipitation, and convective flows in the high-latitude ionosphere. Field aligned current and convective flow patterns during IMF north include polar cap arcs, the theta aurora or transpolar arc, and the 'horse-collar' aurora. The initial part of the study concentrated on the electrodynamics of auroral features in the horse-collar aurora, a contracted but thickened emission region in which the dawn and dusk portions can spread to very high latitudes, while the latter part focused on the evolution of one type of IMF north auroral pattern to another, specifically the quiet-time horse-collar pattern to a theta aurora.

  20. Electron dropout echoes induced by interplanetary shock: Van Allen Probes observations

    Science.gov (United States)

    Hao, Y. X.; Zong, Q.-G.; Zhou, X.-Z.; Fu, S. Y.; Rankin, R.; Yuan, C.-J.; Lui, A. T. Y.; Spence, H. E.; Blake, J. B.; Baker, D. N.; Reeves, G. D.

    2016-06-01

    On 23 November 2012, a sudden dropout of the relativistic electron flux was observed after an interplanetary shock arrival. The dropout peaks at ˜1 MeV and more than 80% of the electrons disappeared from the drift shell. Van Allen twin Probes observed a sharp electron flux dropout with clear energy dispersion signals. The repeating flux dropout and recovery signatures, or "dropout echoes", constitute a new phenomenon referred to as a "drifting electron dropout" with a limited initial spatial range. The azimuthal range of the dropout is estimated to be on the duskside, from ˜1300 to 0100 LT. We conclude that the shock-induced electron dropout is not caused by the magnetopause shadowing. The dropout and consequent echoes suggest that the radial migration of relativistic electrons is induced by the strong dusk-dawn asymmetric interplanetary shock compression on the magnetosphere.

  1. ARISTOTELES: A European approach for an Earth gravity field recovery mission

    Science.gov (United States)

    Benz, R.; Faulks, H.; Langemann, M.

    1989-06-01

    Under contract of the European Space Agency a system study for a spaceborne gravity field recovery mission was performed, covering as a secondary mission objective geodetic point positioning in the cm range as well. It was demonstrated that under the given programmatic constraints including dual launch and a very tight development schedule, a six months gravity field mission in a 200 km near polar, dawn-dusk orbit is adequate to determine gravity anomalies to better than 5 mgal with a spatial resolution of 100 x 100 km half wavelength. This will enable scientists to determine improved spherical harmonic coefficients of the Earth gravity field equation to the order and degree of 180 or better.

  2. The GRADIO spaceborne gravity gradiometer: Development and accommodation

    Science.gov (United States)

    Bernard, A.

    1989-06-01

    The European ARISTOTELES mission aims at the determination of the Earth's gravity field at short wavelength with a global coverage. Gravity gradient measurements will be achieved during six months by the GRADIO instrument onboard a dedicated satellite in a near dawn-dusk sun-synchronous orbit at an altitude of 200 km. The objective is an accuracy of better than 5 mgals for gravity anomalies, at ground level for blocks of 1 x 1 deg. According to present knowledge of the potential, the recovery of higher spherical harmonics (degree and order greater than 30) is of main importance. This leads to focus on the variations of the measured components T(sub ij) of the gravity gradient tensor, at frequencies greater than 5 x 10(exp -3) Hz. The resolution, required for the gradiometer is 10(exp -2) Eotvos (i.e., 10(exp -11)/s squared) with an averaging time of 4 s.

  3. Promises

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    AT dusk, I switched on my radio. What I heard was a special call-in program entitled "New Air of the City," on a local music channel; the two silver-tongued hosts were discussing the topic of promises. A young woman with a soft voice managed to get through first. She said that she had been in love for many years. She and her fiance often went to the banks of the Yangtze River in their spare time, lifting stones to look for small crabs, as tiny as fingernails. They liked to raise the crabs in a glass bowl. But one day, there were few stones by the river; they searched for a long time, but found nothing. An old man who was catching fish told them that it was difficult to find those crabs on the bank. Then he took several crabs out of his

  4. In short photoperiods, human sleep is biphasic.

    Science.gov (United States)

    Wehr

    1992-06-01

    Results of a photoperiod experiment show that human sleep can be unconsolidated and polyphasic, like the sleep of other animals. When normal individuals were transferred from a conventional 16-h photoperiod to an experimental 10-h photo-period, their sleep episodes expanded and usually divided into two symmetrical bouts, several hours in duration, with a 1-3 h waking interval between them. The durations of nocturnal melatonin secretion and of the nocturnal phase of rising sleepiness (measured in a constant routine protocol) also expanded, indicating that the timing of internal processes that control sleep and melatonin, such as circadian rhythms, had been modified by the change in photoperiod. Previous work suggests that the experimental results could be simulated with dual-oscillators, entrained separately to dawn and dusk, or with a two-process model, having a lowered threshold for sleep-onset during the scotoperiod.

  5. Assessment of Plasma Transport and Convection at High Latitudes

    Science.gov (United States)

    1984-01-01

    The high-latitude ionosphere is strongly coupled to the thermosphere and magnetosphere. The magnetospheric coupling occurs via electric fields, field-aligned currents, and particle precipitation. Owing to the interaction of the shocked solar wind with the geomagnetic field, an electric potential difference is generated across the tail of the magnetosphere, with the resulting electric field pointing from dawn to dusk. Energetic particle precipitation from the magnetosphere in the auroral region leads to the creation of ionization and to electron, ion, and neutral gas heating. In order to assess the current understanding of plasma transport and convection at high latitudes, it is necessary to take account of the strong coupling between the ionosphere, thermosphere, and magnetosphere.

  6. Presence of the Eurasian lynx (Lynx lynx in three contiguous valleys of the Verbania Province (Piemonte, northern Italy

    Directory of Open Access Journals (Sweden)

    Marco Di Lorenzo

    2000-09-01

    Full Text Available Abstract The presence of the Eurasian lynx (Lynx lynx L. 1758 was revealed during an investigation performed from I991 to 1994 in three contiguous valleys (Antigorio valley, Formazza valley and Devero valley of the Verbania province in Piemonte. In this investigation two methods were employed: interviews with the people who saw a lynx and/or found evidence of its presence (prints, faeces, scratchings on trees and meal remains and field research by means of line transects, as reported by Ragni et al. (1993. The research area was of about 250 km². Lynx signs were obtained in 1991, 1992 and 1994 between 600 and 1800 m a.s.1. and during all seasons. The lynx was usually observed at night and at dusk. The research shows that the Eurasian lynx is present, although sporadically, in this area of the western Italian Alps.

  7. Influência do ciclo lunar na captura de Aedes scapularis (Diptera, Culicidae na Mata Atlântica do Paraná Influence of the lunar cycle on the traping of Aedes scapularis (Diptera, Culicidae in the Atlantic forest of Paraná

    Directory of Open Access Journals (Sweden)

    Adson Luís Sant'Ana

    Full Text Available From October 1995 to January 1996 Aedes (Ochlerotatus scapularis (Rondani, 1948 was studied in a small area of the Atlantic Forest, Serra do Marumbi, Morretes, Paraná, Brazil. Adults were captured with Shannon light traps for 48 nights, representing 12 nights for seven time intervals. Traps were operated from dusk to dawn. The influences on flight activity of the lunar phase, ambient temperature, relative humidity, and rainfall were analyzed. Ae. scapularis had a flight behaviour different in each of the four lunar phases. In relation to flight period, the species showed higher activity during the first three lunar intervals. Among the climatic variables, temperature and relative humidity positively influenced flight activity during the night.

  8. Solar Tracker With Optical Source

    Directory of Open Access Journals (Sweden)

    Vandana V. Thakare

    2012-06-01

    Full Text Available According to market economy, the increasing worldwide demand for energy forces a continuous rise in the price of fossil combustibles. Infact, it is expected that in near future demand for energy will grow faster than finding new available fossil resources.[1] Among all non conventional energy resources, Solar energy is the most powerful resource that can be used to generate power. In the past, solar cells have been hooked with fixed elevating angles. [2] They do not track the sun and therefore, the efficiency of power generation is low. In this paper, we present an Electronic System that performs the function similar to the Sunflower (a flower that always faces towards the sun which means it starts following the Sun right from dawn till dusk, and starts all over again from dawn next day. On cloudy weathers, it remains still and catches the Sun again as it slips out of clouds. This system works throughout the year.

  9. Letter to the Editor: Geomagnetic storm effects at low latitudes

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    Full Text Available The geomagnetic horizontal (H field from the chain of nine observatories in India are used to study the storm-time and disturbance daily variations. The peak decrease in storm-time variation in H showed significant enhancements at the equatorial electrojet stations over and above the normally expected decrease due to the ring current effects corrected for geomagnetic latitudes. The disturbance daily variation of H at equatorial stations showed a large decrease around midday hours over and above the usual dawn-maximum and dusk-minimum seen at any mid-latitude stations around the world. These slow and persistent additional decreases of H of disturbance daily variation at equatorial latitudes could be the effect of a westward electric field due to the Disturbance Ionospheric dynamo coupled with abnormally large electrical conductivities in the E region over the equator.Key words. Ionosphere (electric fields and currents · Magnetospheric physics (electric fields; storms and substorms

  10. Rax: Developmental and Daily Expression Patterns in the Rat Pineal Gland and Retina

    DEFF Research Database (Denmark)

    Rohde, Kristian; Klein, David C; Møller, Morten;

    2011-01-01

    Retina and anterior neural fold homeobox (Rax) gene encodes a transcription factor essential for vertebrate eye development. Recent microarray studies indicate that Rax is expressed in the adult rat pineal gland and retina. The present study reveals that Rax expression levels in the rat change...... significantly during retinal development with a peak occurring at embryonic day (E) 18, whereas Rax expression in the pineal is relatively delayed and not detectable until E20. In both tissues, Rax is expressed throughout postnatal development into adulthood. In the mature rat pineal gland, the abundance of Rax...... transcripts increases 2-fold during the light period with a peak occurring at dusk. These findings are consistent with the evidence that Rax is of functional importance in eye development and suggest a role of Rax in the developing pineal gland. In addition, it would appear possible that Rax contributes...

  11. Observations of the April 2002 Storm Period with TIMED-TIDI

    Science.gov (United States)

    Niciejewski, R.; Killeen, T.; Wu, Q.; Skinner, W.; Solomon, S.; Ortland, D.; Kafkalidis, J.; Gell, D.; Gablehouse, D.; Johnson, R.

    2002-12-01

    TIDI is meeting its basic requirement, which is to measure the global wind field in the mesosphere and lower thermosphere, the core study region. Since February 2002, TIDI has been in a routine science data-taking mode. During April 2002, TIMED was positioned at a high beta angle (angle between the plane of the satellite orbit and the Earth-Sun line) resulting in a series of TIDI measurements near the dusk/dawn terminator. The field of view of TIDI allows it to obtain measurements from pole to pole, while the repetition rate of the sky-scanner allows it to obtain several scans within the auroral oval region on each orbit. This paper will discuss TIDI measurements obtained during the April 2002 storm period, including OI (5577\\x8F) intensity data and neutral wind data sets.

  12. Dynamic effects of restoring footpoint symmetry on closed magnetic field lines

    CERN Document Server

    Reistad, J P; Tenfjord, P; Laundal, K M; Snekvik, K; Haaland, S; Milan, S E; Oksavik, K; Frey, H U; Grocott, A

    2016-01-01

    Here we present an event where simultaneous global imaging of the aurora from both hemispheres reveals a large longitudinal shift of the nightside aurora of about 3 h, being the largest relative shift reported on from conjugate auroral imaging. This is interpreted as evidence of closed field lines having very asymmetric footpoints associated with the persistent positive $\\textit{y}$ component of the interplanetary magnetic field before and during the event. At the same time, the Super Dual Auroral Radar Network observes the ionospheric nightside convection throat region in both hemispheres. The radar data indicate faster convection toward the dayside in the dusk cell in the Southern Hemisphere compared to its conjugate region. We interpret this as a signature of a process acting to restore symmetry of the displaced closed magnetic field lines resulting in flux tubes moving faster along the banana cell than the conjugate orange cell. The event is analyzed with emphasis on Birkeland currents (BC) associated wit...

  13. Flux transfer events on the magnetopause - Spatial distribution and controlling factors

    Science.gov (United States)

    Berchem, J.; Russell, C. T.

    1984-01-01

    The spatial distribution of flux transfer events (FTE) of magnetic flux tubes pulled from the earth's magnetopause is analyzed using ISEE 1 and 2 data from 1977-82. Attention is given to interplanetary conditions influencing different observed FTE polarities. FTEs were observed on nearly 25 percent of the passes near the dayside magnetopause. Direct FTEs were located mainly in the northern dawn sector and reverse FTEs appeared in the southern dusk sector. The distribution indicated an origin in the equatorial sector, and data correlate the appearance of FTEs only when the interplanetary magnetic field (IMF) had southward or nearly horizontal orientation. The presence of a southward component in the IMF was coincident with the appearance of an FTE 45 percent of the events. E-W components in the IMF exhibited no connections with the occurrence of an FTE.

  14. Post-equinox periodicities in Saturn's energetic electrons

    Science.gov (United States)

    Carbary, J. F.; Mitchell, D. G.; Krimigis, S. M.; Krupp, N.

    2011-12-01

    Since Saturn's vernal equinox in August 2009 (day 223), energetic electrons (110-365 keV) have exhibited a variety of periodic and aperiodic behavior within a spectral window of 5-15 hours. From late 2009 through the end of 2010, when the observed at dusk, a single period near 10.7 hours dominated the Lomb spectra of these particles. Near the end of 2010, however, the energetic electrons displayed multiple periods, with the strongest at 10.65 hours. The periodicity observed after equinox has a mean value of 10.69 ± 0.06 hours and agreed closely with that of Saturn kilometric radio (south) emissions. By early 2011, when the observer had moved to the dayside, the periodicities abruptly disappeared and the Lomb spectra show no periodicity. This behavior may suggest changes in Saturn's ionosphere as a result of seasonal change, or may alternately imply a local time dependence of periodicity caused by magnetodisk thickness asymmetry.

  15. Investigation of Relativistic Electron Resonance with EMIC Waves

    Science.gov (United States)

    Woodger, L. A.; Millan, R. M.; Denton, R. E.

    2008-12-01

    Wave-particle interaction of relativistic electrons with EMIC waves has been proposed as an important loss mechanism for radiation belt electrons (e.g. Thorne and Andreoli, 1980). Lorentzen et al (2000) and Millan et al (2002) suggested this mechanism to be responsible for dusk side relativistic electron precipitation (REP) detected by balloon borne instrumentation. This study will use the linear electromagnetic dispersion code WHAMP to investigate the effects of density, magnetic field, anisotropy, and heavy ions on the minimum resonance energy for relativistic electrons with EMIC waves. Results will be compared with observations of REP during the MAXIS balloon campaign on Jan. 19, 2000 and the MINIS balloon campaign on Jan. 21, 2005.

  16. Investigating Plasmasphere Location during Relativistic Electron Precipitation Events

    Science.gov (United States)

    Woodger, L. A.; Millan, R. M.; Goldstein, J.; McCarthy, M. P.; Smith, D. M.; Sample, J. G.

    2006-12-01

    The plasmasphere plays a crucial role in the generation of different wave modes and their resonance conditions with radiation belt relativistic electrons. Meredith's (et. al., 2003) statistical study of resonant conditions for >2MeV electrons with EMIC waves found that the majority of these events occur in the vicinity of the plasmpause. The MAXIS and MINIS balloon observations found a distinct class of relativistic electron precipitation occurring at dusk, suggesting EMIC waves as a possible precipitation mechanism. We investigate the location of these relativistic electron precipitation events with respect to the plasmapause using data from IMAGE EUV, POLAR EFI, and a plasmapause test particle simulation driven by an electric field model with terms representing solar-wind-driven convection and ring-current-ionospheric coupling.

  17. Foreshock ions observed behind the Martian bow shock

    Science.gov (United States)

    Frahm, R. A.; Yamauchi, M.; Winningham, J. D.; Lundin, R.; Sharber, J. R.; Nilsson, H.; Coates, A. J.

    2016-08-01

    The Mars Express Analyzer of Space Plasmas and Energetic Atoms experiment contains ion and electron instruments for conducting plasma measurements. On January 23, 2012, during in-bound travel of Mars Express in the southern hemisphere of Mars from its dawn side toward periapsis at dusk, the plasma instruments measured foreshock-like ion beams extending from outside the bow shock and into the magnetosphere, continuing to a distance of about a proton gyroradius from the bow shock. These ion beams were mostly protons, were observed to have energies greater than solar wind protons, and were not gyrating, in agreement with reflections of the solar wind proton beam. Furthermore, in the foreshock region the ion energy gradually decreased toward the magnetosheath, in agreement with an acceleration by outward-directed electric field in the bowshock. The observations also suggest that this electric field exists even inside the magnetosheath within the distance of a proton gyroradius from the bow shock.

  18. Correlation between convection electric fields in the nightside magnetosphere and several wave and particle phenomena during two isolated substorms.

    Science.gov (United States)

    Carpenter, D. L.; Fraser-Smith, A. C.; Unwin, R. S.; Hones, E. W., Jr.; Heacock, R. R.

    1971-01-01

    Correlation of several magnetoionospheric wave and particle phenomena previously linked observationally to magnetospheric substorms and inferred to involve convection electric fields with whistler measurements of convection activity during two relatively isolated substorms. The events occurred at about 0600 UT on July 15, 1965, and about 0500 UT on Oct. 13, 1965. The correlated phenomena include cross-L inward plasma drifts near midnight within the plasmaphere, diffuse auroral radar echoes observed near the dusk meridian, IPDP micropulsations (intervals of pulsations of diminishing period) in the premidnight sector, apparent contractions and expansions of the plasma sheet at about 20 earth radii in the magnetotail, and Pc 1/Pi 1 micropulsation events near or before midnight. Two new vlf phenomena occurred during the October 13 event - a noise band within the plasmasphere associated with a convecting whistler path, and ?hisslers,' falling-tone auroral-hiss forms repeated at intervals of about 2 sec.

  19. [Phlebotominae (Diptera: Psychodidae) in area of transmission of american tegumentar leishmaniasis in the north coast of the State of São Paulo, Brazil].

    Science.gov (United States)

    de Brito, Marylene; Casanova, Cláudio; Mascarini, Luciene Maura; Wanderley, Dalva Marli Valério; Corrêa, Fernando Motta de Azevedo

    2002-01-01

    Fourteen, 30 and 104 cases of American tegumentary leishmaniasis were recorded respectively, in 1993, 1994 and 1995, in the coast region of São Paulo State. Aiming to characterize the fauna and seasonal and hourly distributions of the phlebotominic species, adult specimens were captured fortnightly between November/95 and December/96. CDC light traps were used as of dusk intradomiciliarly, peridomiciliarly and in the forest for 12 hours. From the same moment on but only during 6 hours Shannon traps were set in the peridomicile 100 meters from the house. Quarterly this trap was used for 12 hours. The population density fluctuation as well as the occurrence of intra and extradomiciliarly predominant species were observed. In the different traps used and environments investigated Lutzomyia intermedia was the most abundant species.

  20. Solar elevation dependent radiosonde temperature bias adjustments back to the 1940s

    Science.gov (United States)

    Haimberger, Leopold

    2016-04-01

    The well established RAOBCORE/RICH bias adjustment system for radiosonde temperature records has been enhanced to cope with seasonal changes of solar elevation dependent biases. It is argued that the seasonal cycle of reanalyses is more reliable than that of certain radiosonde types, especially at places where the radiosondes are launched around dawn or dusk, i.e. at high latitudes or near 90E/90W. Furthermore the data set has been extended back to the late 1940s, using JRA-55 and ERA-preSAT background departures as reference. For verification the adjusted data are compared against independent data sets and reanalyses as far as they are available. Suitability of the adjusted data as input for future reanalyses is discussed.

  1. Dual E × B flow responses in the dayside ionosphere to a sudden IMF By rotation

    Science.gov (United States)

    Eriksson, S.; Maimaiti, M.; Baker, J. B. H.; Trattner, K. J.; Knipp, D. J.; Wilder, F. D.

    2017-07-01

    We report for the first time a dual transition state in the dayside ionosphere following a sudden rotation of the interplanetary magnetic field (IMF) in the upstream magnetosheath from IMF By By > 0 during Bz rotation of lower latitude E × B flow from dusk to dawn. We propose that this sequence of events is consistent with two separate X lines coexisting on the subsolar and lobe magnetopause. Time delays are proposed for merged flux of the draped preceding IMF to exit the subsolar region before the new IMF may be processed along a newly reconfigured component reconnection X line. Finally, a strong direct correlation is observed between magnetosheath plasma density and auroral zone E × B speeds.

  2. BRITE-Constellation: Nanosatellites for Precision Photometry of Bright Stars

    CERN Document Server

    Weiss, W W; Schwarzenberg-Czerny, A; Koudelka, O F; Grant, C C; Zee, R E; Kuschnig, R; Mochnacki, St; Rucinski, S M; Matthews, J M; Orleanski, P; Pamyatnykh, A; Pigulski, A; Alves, J; Guedel, M; Handler, G; Wade, G A; Scholtz, A L

    2013-01-01

    BRITE-Constellation (where BRITE stands for BRIght Target Explorer) is an international nanosatellite mission to monitor photometrically, in two colours, brightness and temperature variations of stars brighter than V = 4. The current mission design consists of three pairs of 7 kg nanosats from Austria, Canada and Poland carrying optical telescopes and CCDs. One instrument in each pair is equipped with a blue filter; the other, a red filter. The first two nanosats are UNIBRITE, designed and built by University of Toronto Institute for Aerospace Studies - Space Flight Laboratory and its twin, BRITE-Austria, built by the Technical University Graz with support of UTIAS-SFL. They were launched on 25 February 2013 by the Indian Space Agency under contract to the Canadian Space Agency into a low-Earth dusk-dawn polar orbit.

  3. PERILAKU DAN JENIS PAKAN ORANGUTAN KALIMANTAN (PONGO PYGMAEUS LINNAEUS, 1760 DL KALIMANTAN

    Directory of Open Access Journals (Sweden)

    PURWO KUNCORO

    2008-12-01

    Full Text Available Data collection was conducted using focal animal instantaneous. The daily activity data were group based on their ethogram and was adopting "The Standard of Orangutan's collection" from Morrogh-Bernard et al. (2002. The research collected 739 hours 29 minutes of dawn to dusk observations. The daily activity was determined by activity proportion. Rehabilitated Orangutans was found to have higher proportion of social activity (79,29% than the one of self-action activity (23,71%. The daily activity proportions consisted of 10,44% (females and 14,13% (males for movement, 29,01% (females and 30,66% (males for resting, 12,34% (females and 4,90% (males for social activities, 3,36% (females and 2,49% (males for self activities, and also 44,85% (females and 47,82% (males for foraging with 96 plants species and 1 termite species as food sources.

  4. Unfixed in a fixated world: identity, sexuality, race and culture.

    Science.gov (United States)

    Offord, B; Cantrell, L

    1999-01-01

    At the dusk of the twentieth century the confluence of sexuality and the multicultural subject offers a deep interrogation into identity. On the edge of the world, Australia is experiencing a poignant moment of identity crisis. For someone who is from a multicultural, multisexual background, identity is fragmented. Law and society demand unambiguous subjects, fixed by socio-political-cultural mores and expectations. To be unfixed presents difficulties in negotiating systems of knowledge and power which are fundamentally homeostatic. In the end it is all a matter of being unfixed but connected to "others," aware of the substance beyond identity and labels. This is being unfixed in a fixated world, challenging gravity, resisting definition and compromise.

  5. A study of population changes in adult Culex quinquefasciatus Say (Diptera: Culicidae) during a mosquito control programme in Dubai, United Arab Emirates.

    Science.gov (United States)

    Holmes, P R

    1986-02-01

    The effectiveness of insecticidal control measures on adult Culex quinquefasciatus Say in Dubai, United Arab Emirates, was examined. Direct treatment of the study site with cypermethrin applied as a fog caused a temporary reduction both in total numbers (males and females) and in the proportion of older females. When cypermethrin was applied as an ultra low volume formulation at dusk and dawn numbers of males were greatly reduced, but numbers of females were not affected. It appears that the adulticiding operations had little overall effect on the total numbers or survival rate of females, or breeding success. The oviposition cycle duration was estimated to be two days, with the survival rate per oviposition cycle calculated as 30%. With these values it is thought unlikely that filariasis would be transmitted in Dubai.

  6. Mercury's Magnetospheric Cusps and Cross-Tail Current Sheet: Structure and Dynamics

    Science.gov (United States)

    Poh, Gang Kai

    Mercury has proven to be a unique natural laboratory for space plasma processes. Mercury's magnetosphere is formed by the interaction between its intrinsic planetary magnetic field and the supersonic solar wind. The structure of Mercury's magnetosphere is very similar to Earth's; yet the results from the MESSENGER mission to Mercury have shown that the spatial and temporal scales of magnetospheric processes are very different at Mercury. In this thesis, we analyze in situ observations from the MESSENGER spacecraft to characterize and understand the dynamic physical plasma processes occurring in Mercury's magnetosphere. We identified and analyzed 345 plasma filaments in Mercury's northern magnetospheric cusp to determine their physical properties. Cusp plasma filaments are magnetic structures that are identified on the basis of their characteristic 2-3 seconds long decrease in magnetic field intensity. Our analysis indicates that these cusp filaments are cylindrical flux tubes filled with plasma, which causes a diamagnetic decrease in the magnetic field inside the flux tube. MESSENGER observations of flux transfer events (FTEs) and cusp filament suggests that cusp filaments properties are the low-altitude extension of FTEs formed at Mercury's dayside magnetopause. We examined 319 central plasma sheet crossings observed by MESSENGER. Using a Harris model, we determined the physical properties of Mercury's cross-tail current sheet. Analysis of BZ in the current sheet indicated that MESSENGER usually crossed the current sheet sunward of the Near Mercury Neutral Line. Magnetohydrodynamics-based analysis using the MESSENGER magnetic field and plasma measurements suggests that heavy planetary ions and/or ion temperature anisotropy may be important in maintaining radial stress balance within Mercury's central plasma sheet. We report the observation of significant dawn-dusk variation in Mercury's cross-tail current sheet with thicker, lower plasma beta dawn side current

  7. The substructure of a flux transfer event observed by the MMS spacecraft

    Science.gov (United States)

    Hwang, K.-J.; Sibeck, D. G.; Giles, B. L.; Pollock, C. J.; Gershman, D.; Avanov, L.; Paterson, W. R.; Dorelli, J. C.; Ergun, R. E.; Russell, C. T.; Strangeway, R. J.; Mauk, B.; Cohen, I. J.; Torbert, R. B.; Burch, J. L.

    2016-09-01

    On 15 August 2015, MMS (Magnetospheric Multiscale mission), skimming the dusk magnetopause, detected an isolated region of an increased magnetic strength and bipolar Bn, indicating a flux transfer event (FTE). The four spacecraft in a tetrahedron allowed for investigations of the shape and motion of the FTE. In particular, high-resolution particle data facilitated our exploration of FTE substructures and their magnetic connectivity inside and surrounding the FTE. Combined field and plasma observations suggest that the core fields are open, magnetically connected to the northern magnetosphere from which high-energy particles leak; ion "D" distributions characterize the axis of flux ropes that carry old-opened field lines; counterstreaming electrons superposed by parallel-heated components populate the periphery surrounding the FTE; and the interface between the core and draped regions contains a separatrix of newly opened magnetic field lines that emanate from the X line above the FTE.

  8. Statistical analysis of monochromatic whistler waves near the Moon detected by Kaguya

    Directory of Open Access Journals (Sweden)

    Y. Katoh

    2011-05-01

    Full Text Available Observations are presented of monochromatic whistler waves near the Moon detected by the Lunar Magnetometer (LMAG on board Kaguya. The waves were observed as narrowband magnetic fluctuations with frequencies close to 1 Hz, and were mostly left-hand polarized in the spacecraft frame. We performed a statistical analysis of the waves to identify the distributions of their intensity and occurrence. The results indicate that the waves were generated by the solar wind interaction with lunar crustal magnetic anomalies. The conditions for observation of the waves strongly depend on the solar zenith angle (SZA, and a high occurrence rate is recognized in the region of SZA between 40° to 90° with remarkable north-south and dawn-dusk asymmetries. We suggest that ion beams reflected by the lunar magnetic anomalies are a possible source of the waves.

  9. A new member of the LIR family from perennial ryegrass is cold-responsive, and promotes vegetative growth in ¤Arabidopsis¤

    DEFF Research Database (Denmark)

    Ciannamea, S.; Jensen, Christian Sig; Agerskov, Henrik

    2007-01-01

    A cold-regulated gene Lolium perenne LIR1 (LpLIR1) was isolated from perennial ryegrass using a subtractive approach. The gene has strong homology to the Light Induced Rice1 (LIR1) gene and is regulated at the transcriptional level by cold, and by a diurnal rhythm. Expression of LpLIR1 in perennial...... dusk and declined during the night. Heterologous expression of LpLIR1 in Arabidopsis led to a significant increase in leaf formation under short days (SD) conditions but only when plants had received a preceding vernalization treatment. Furthermore, dissection of plant development under SD revealed...... a minor but significant delay of flowering in the transgenic lines compared to wildtype plants. (c) 2006 Elsevier Ireland Ltd. All rights reserved....

  10. A mysterious dust clump in a disk around an evolved binary star system.

    Science.gov (United States)

    Jura, M; Turner, J

    1998-09-10

    The discovery of planets in orbit around the pulsar PSR1257+12 shows that planets may form around post-main-sequence stars. Other evolved stars, such as HD44179 (an evolved star which is part of the binary system that has expelled the gas and dust that make the Red Rectangle nebula), possess gravitationally bound orbiting dust disks. It is possible that planets might form from gravitational collapse in such disks. Here we report high-angular-resolution observations at millimetre and submillimetre wavelengths of the dusk disk associated with the Red Rectangle. We find a dust clump with an estimated mass near that of Jupiter in the outer region of the disk. The clump is larger than our Solar System, and far beyond where planet formation would normally be expected, so its nature is at present unclear.

  11. Active experiments and single ion motion in the magnetotail

    Science.gov (United States)

    Rothwell, P. L.; Yates, G. K.

    1983-07-01

    Analytic solutions to the Lorentz equation which indicate that the magnetic field in the plasma sheet focuses selected ions from the plasma sheet boundaries on the neutral sheet are obtained. The kinetic energy of these ions usually exceeds the threshold energy required for the ion tearing mode instability. Two active experiments based on this effect are proposed. Heavy ions injected towards dusk on the plasma sheet boundary would become focused on the neutral sheet and perhaps trigger the ion tearing mode. A boundary perturbation, such as a thermal chemical release, that locally enhances the boundary turbulence level could be introduced, causing sufficient ksq = 1 ions to be focused on the neutral sheet to trigger the ion tearing mode.

  12. Exospheric hydrogen density distributions for equinox and summer solstice observed with TWINS1/2 during solar minimum

    Directory of Open Access Journals (Sweden)

    J. H. Zoennchen

    2013-03-01

    Full Text Available The Lyman-α Detectors (LAD on board the two TWINS 1/2-satellites allow for the simultaneous stereo imaging of the resonant emission glow of the H-geocorona from very different orbital positions. Terrestrial exospheric atomic hydrogen (H resonantly scatters solar Lyman-α (121.567 nm radiation. During the past solar minimum, relevant solar parameters that influence these emissions were quite stable. Here, we use simultaneous LAD1/2-observations from TWINS1 and TWINS2 between June 2008 and June 2010 to study seasonal variations in the H-geocorona. Data are combined to produce two datasets containing (summer solstice and (combined spring and fall equinox emissions. In the range from 3 to 10 Earth radii (RE, a three-dimensional (3-D mathematical model is used that allows for density asymmetries in longitude and latitude. At lower geocentric distances (RE, a best fitting r-dependent (Chamberlain, 1963-like model is adapted to enable extrapolation of our information to lower heights. We find that dawn and dusk H-geocoronal densities differ by up to a factor of 1.3 with higher densities on the dawn side. Also, noon densities are greater by up to a factor of 2 compared to the dawn and dusk densities. The density profiles are aligned well with the Earth–Sun line and there are clear density depletions over both poles that show additional seasonal effects. These solstice and equinox empirical fits can be used to determine H-geocoronal densities for any day of the year for solar minimum conditions.

  13. Host-seeking activity and avian host preferences of mosquitoes associated with West Nile virus transmission in the northeastern U.S.A.

    Science.gov (United States)

    Suom, Channsotha; Ginsberg, Howard S.; Bernick, Andrew; Klein, Coby; Buckley, P.A.; Salvatore, Christa; LeBrun, Roger A.

    2010-01-01

    Mosquito host-seeking activity was studied using a custom-designed trap to explore: (1) at which time interval of the night adult mosquito abatement would be most effective, and (2) if there exists an avian-specific host-seeking preference. Overnight trials using traps baited with dry ice showed that Aedes taeniorhynchus (Wiedemann) was most active at dusk and was then captured throughout the night. In contrast, Culex spp. (Cx. pipiens (Linnaeus) and Cx. restuans (Theobald) delayed most activity until about two h after dusk and were then captured through the night. This pattern suggests that management activities directed at adult Culex spp. would be most effective if initiated well after sunset. Mosquito capture rates in traps baited with birds in net bags were significantly greater than those with empty net bags, indicating that mosquitoes were attracted to the birds and not incidentally being sucked in by the custom trap's strong fan motor (Wilcoxon matched-pairs signed-ranks test, n = 24, t = 30, p 2 = 0.21, p = 0.02). Trials with paired traps that contained different native bird species showed that Gray Catbirds, Dumatella carolinensis, attracted more mosquitoes than the heavier Northern Cardinals, Cardinalis cardinalis (paired samples t-test, t = 2.58, df = 7, p = 0.04). However, attractiveness did not differ substantially among bird species, and Gray Catbirds did not attract more mosquitoes than all other birds combined as a group. American Robins, Turdus migratorius (n = 4) were comparable in attractiveness to other bird species, but not enough American Robins were captured for a comprehensive study of mosquito avian preference.

  14. Dayside and nightside contributions to cross-polar cap potential variations: the 20 March 2001 ICME case

    Directory of Open Access Journals (Sweden)

    Y. L. Andalsvik

    2011-11-01

    Full Text Available We investigate the association between temporal-spatial structure of polar cap convection and auroral electrojet intensifications during a 5-h-long interval of strong forcing of the magnetosphere by an ICME/Magnetic cloud on 20 March 2001. We use data from coordinated ground-satellite observations in the 15:00–20:00 MLT sector. We take advantage of the good latitudinal coverage in the polar cap and in the auroral zone of the IMAGE chain of ground magnetometers in Svalbard – Scandinavia – Russia and the stable magnetic field conditions in ICMEs. The electrojet events are characterized by a sequence of 10 min-long AL excursions to −1000/−1500 nT followed by poleward expansions and auroral streamers. These events are superimposed on a high disturbance level when the AL index remains around −500 nT for several hours. These signatures are different from those appearing in classical substorms, most notably the absence of a complete recovery phase when AL usually reaches above −100 nT. We concentrate on polar cap convection in both hemispheres (DMSP F13 data in relation to the ICME By conditions, electrojet intensifications, and the global UV auroral configuration obtained from the IMAGE spacecraft. The temporal evolution of convection properties such as the cross-polar cap potential (CPCP drop and flow channels at the dawn/dusk polar cap (PC boundaries around the time of the electrojet events are investigated. This approach allows us to distinguish between dayside (magnetopause reconnection and nightside (magnetotail reconnection sources of the PC convection events within the context of the expanding-contracting model of high-latitude convection in the Dungey cycle. Inter-hemispheric symmetries/asymmetries in the presence of newly-discovered convection channels at the dawn or dusk side PC boundaries are determined.

  15. How does a carnivore guild utilise a substantial but unpredictable anthropogenic food source? Scavenging on hunter-shot ungulate carcasses by wild dogs/dingoes, red foxes and feral cats in south-eastern Australia revealed by camera traps.

    Directory of Open Access Journals (Sweden)

    David M Forsyth

    Full Text Available There is much interest in understanding how anthropogenic food resources subsidise carnivore populations. Carcasses of hunter-shot ungulates are a potentially substantial food source for mammalian carnivores. The sambar deer (Rusa unicolor is a large (≥ 150 kg exotic ungulate that can be hunted throughout the year in south-eastern Australia, and hunters are not required to remove or bury carcasses. We investigated how wild dogs/dingoes and their hybrids (Canis lupus familiaris/dingo, red foxes (Vulpes vulpes and feral cats (Felis catus utilised sambar deer carcasses during the peak hunting seasons (i.e. winter and spring. We placed carcasses at 1-km intervals along each of six transects that extended 4-km into forest from farm boundaries. Visits to carcasses were monitored using camera traps, and the rate of change in edible biomass estimated at ∼ 14-day intervals. Wild dogs and foxes fed on 70% and 60% of 30 carcasses, respectively, but feral cats seldom (10% fed on carcasses. Spatial and temporal patterns of visits to carcasses were consistent with the hypothesis that foxes avoid wild dogs. Wild dog activity peaked at carcasses 2 and 3 km from farms, a likely legacy of wild dog control, whereas fox activity peaked at carcasses 0 and 4 km from farms. Wild dog activity peaked at dawn and dusk, whereas nearly all fox activity occurred after dusk and before dawn. Neither wild dogs nor foxes remained at carcasses for long periods and the amount of feeding activity by either species was a less important predictor of the loss of edible biomass than season. Reasons for the low impacts of wild dogs and foxes on sambar deer carcass biomass include the spatially and temporally unpredictable distribution of carcasses in the landscape, the rapid rate of edible biomass decomposition in warm periods, low wild dog densities and the availability of alternative food resources.

  16. Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation.

    Science.gov (United States)

    Queiroz, Nuno; Humphries, Nicolas E; Noble, Leslie R; Santos, António M; Sims, David W

    2012-01-01

    Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic fisheries by-catch species, the blue shark Prionace glauca, in the North-east Atlantic using pop-off satellite-linked archival tags to determine the degree of space use linked to habitat and to examine vertical niche. Overall, blue sharks moved south-west of tagging sites (English Channel; southern Portugal), exhibiting pronounced site fidelity correlated with localized productive frontal areas, with estimated space-use patterns being significantly different from that of random walks. Tracked female sharks displayed behavioural variability in diel depth preferences, both within and between individuals. Diel depth use ranged from normal DVM (nDVM; dawn descent, dusk ascent), to reverse DVM (rDVM; dawn ascent, dusk descent), to behavioural patterns where no diel differences were apparent. Results showed that blue sharks occupy some of the most productive marine zones for extended periods and structure diel activity patterns across multiple spatio-temporal scales in response to particular habitat types. In so doing, sharks occupied an extraordinarily broad vertical depth range for their size (1.0-2.0 m fork length), from the surface into the bathypelagic realm (max. dive depth, 1160 m). The space-use patterns of blue sharks indicated they spend much of the time in areas where pelagic longlining activities are often highest, and in depth zones where these fisheries particularly target other species, which could account for the rapid declines recently reported for blue sharks in many parts of the world's oceans. Our results provide habitat targets for blue shark conservation that

  17. Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation.

    Directory of Open Access Journals (Sweden)

    Nuno Queiroz

    Full Text Available Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic fisheries by-catch species, the blue shark Prionace glauca, in the North-east Atlantic using pop-off satellite-linked archival tags to determine the degree of space use linked to habitat and to examine vertical niche. Overall, blue sharks moved south-west of tagging sites (English Channel; southern Portugal, exhibiting pronounced site fidelity correlated with localized productive frontal areas, with estimated space-use patterns being significantly different from that of random walks. Tracked female sharks displayed behavioural variability in diel depth preferences, both within and between individuals. Diel depth use ranged from normal DVM (nDVM; dawn descent, dusk ascent, to reverse DVM (rDVM; dawn ascent, dusk descent, to behavioural patterns where no diel differences were apparent. Results showed that blue sharks occupy some of the most productive marine zones for extended periods and structure diel activity patterns across multiple spatio-temporal scales in response to particular habitat types. In so doing, sharks occupied an extraordinarily broad vertical depth range for their size (1.0-2.0 m fork length, from the surface into the bathypelagic realm (max. dive depth, 1160 m. The space-use patterns of blue sharks indicated they spend much of the time in areas where pelagic longlining activities are often highest, and in depth zones where these fisheries particularly target other species, which could account for the rapid declines recently reported for blue sharks in many parts of the world's oceans. Our results provide habitat targets for blue shark

  18. Seasonal abundance & role of predominant Japanese encephalitis vectors Culex tritaeniorhynchus & Cx. gelidus Theobald in Cuddalore district, Tamil Nadu

    Science.gov (United States)

    Ramesh, D.; Muniaraj, M.; Samuel, P. Philip; Thenmozhi, V.; Venkatesh, A.; Nagaraj, J.; Tyagi, B.K.

    2015-01-01

    Background & objectives: Japanese encephalitis (JE) is the leading cause of viral encephalitis in Asia. The first major JE outbreak occurred in 1978 and since 1981 several outbreaks had been reported in the Cuddalore district (erstwhile South Arcot), Tamil Nadu, India. Entomological monitoring was carried out during January 2010 - March 2013, to determine the seasonal abundance and transmission dynamics of the vectors of JE virus, with emphasis on the role of Culex tritaeniorhynchus and Cx. gelidus. Methods: Mosquito collections were carried out fortnightly during dusk hours in three villages viz. Soundara Solapuram, Pennadam, Erappavur of Cuddalore district. Mosquitoes were collected during dusk for a period of one hour in and around the cattle sheds using oral aspirator and torch light. The collected mosquitoes were later identified and pooled to detect JE virus (JEV) infection by enzyme linked immunosorbent assay (ELISA). Results: A total of 46,343 mosquitoes comprising of 25 species and six genera were collected. Species composition included viz, Cx. tritaeniorhynchus (46.26%), Cx. gelidus (43.12%) and other species (10.62%). A total of 17,678 specimens (403 pools) of Cx. gelidus and 14,358 specimens (309 pools) of Cx. tritaeniorhynchus were tested, of which 12 pools of Cx. gelidus and 14 pools of Cx. tritaeniorhynchus were positive for JE virus antigen. The climatic factors were negatively correlated with minimum infection rate (MIR) for both the species, except mean temperature (P<0.05) for Cx. gelidus. Interpretation & conclusions: High abundance of Cx. tritaeniorhynchus and Cx. gelidus was observed compared to other mosquito species in the study area. Detection of JEV antigen in the two species confirmed the maintenance of virus. Appropriate vector control measures need to be taken to reduce the vector abundance. PMID:26905238

  19. Strong IMF By-Related Plasma Convection in the Ionosphere and Cusp Field-Aligned Currents Under Northward IMF Conditions

    Science.gov (United States)

    Le, G.; Lu, G.; Strangeway, R. J.; Pfaff, R. F., Jr.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    We present in this paper an investigation of IMF-By related plasma convection and cusp field-aligned currents using FAST data and AMIE model during a prolonged interval with large positive IMF By and northward Bz conditions (By/Bz much greater than 1). Using the FAST single trajectory observations to validate the global convection patterns at key times and key locations, we have demonstrated that the AMIE procedure provides a reasonably good description of plasma circulations in the ionosphere during this interval. Our results show that the plasma convection in the ionosphere is consistent with the anti-parallel merging model. When the IMF has a strongly positive By component under northward conditions, we find that the global plasma convection forms two cells oriented nearly along the Sun-earth line in the ionosphere. In the northern hemisphere, the dayside cell has clockwise convection mainly circulating within the polar cap on open field lines. A second cell with counterclockwise convection is located in the nightside circulating across the polar cap boundary, The observed two-cell convection pattern appears to be driven by the reconnection along the anti-parallel merging lines poleward of the cusp extending toward the dusk side when IMF By/Bz much greater than 1. The magnetic tension force on the newly reconnected field lines drives the plasma to move from dusk to dawn in the polar cusp region near the polar cap boundary. The field-aligned currents in the cusp region flow downward into the ionosphere. The return field-aligned currents extend into the polar cap in the center of the dayside convection cell. The field-aligned currents are closed through the Peterson currents in the ionosphere, which flow poleward from the polar cap boundary along the electric field direction.

  20. Polar ionospheric responses to solar wind IMF changes

    Directory of Open Access Journals (Sweden)

    Y. Zhang

    Full Text Available Auroral and airglow emissions over Eureka (89° CGM during the 1997-98 winter show striking variations in relation to solar wind IMF changes. The period January 19 to 22, 1998, was chosen for detailed study, as the IMF was particularly strong and variable. During most of the period, Bz was northward and polar arcs were observed. Several overpasses by DMSP satellites during the four day period provided a clear picture of the particle precipitation producing the polar arcs. The spectral character of these events indicated excitation by electrons of average energy 300 to 500 eV. Only occasionally were electrons of average energy up to ~1 keV observed and these appeared transitory from the ground optical data. It is noted that polar arcs appear after sudden changes in IMF By, suggesting IMF control over arc initiation. When By is positive there is arc motion from dawn to dusk, while By is negative the motion is consistently dusk to dawn. F-region (anti-sunward convections were monitored through the period from 630.0 nm emissions. The convection speed was low (100-150 m/s when Bz was northward but increased to 500 m/s after Bz turned southward on January 20.

    Key words: Atmospheric composition and structure (airglow and aurora - Ionosphere (particle precipitation - Magnetospheric Physics (polar cap phenomena

  1. Variation of surface electric field during geomagnetic disturbed period at Maitri, Antarctica

    Indian Academy of Sciences (India)

    N Jeni Victor; C Panneerselvam; C P Anil Kumar

    2015-12-01

    The paper discusses on the variations of the atmospheric vertical electric field measured at sub-auroral station Maitri (70°75′S, 11°75′E), and polar station Vostok (78.5°S, 107°E) during the geomagnetic disturbances on 25–26 January 2006. Diurnal variation of surface electric field measured at Maitri shows a similar variation with worldwide thunderstorm activity, whereas the departure of the field is observed during disturbed periods. This part of the field corresponds to the magnetospheric/ionospheric (an additional generator in the polar regions) voltage generators. Solar wind parameters and planetary indices represent the temporal variation of the disturbances, and digital fluxgate magnetometer variation continuously monitored to trace the auroral movement at Maitri. We have observed that the electrojet movement leaves its signature on vertical and horizontal components of the DFM in addition; the study infers the position of auroral current wedge with respect to Maitri. To exhibit the auroral oval, OVATION model is obtained with the aid of DMSP satellite and UV measurements. It is noted that the Maitri is almost within the auroral oval during the periods of disturbances. To examine the simultaneous changes in the vertical electric field associated with this magnetic disturbance, the dawn–dusk potential is studied for every UT hours; the potential was obtained from Weimer model and SuperDARN radar. The comparison reveals the plausible situation for the superposition of dawn–dusk potential on surface electric field over Maitri. This observation also shows that the superposition may not be consistent with the phase of the electrojet. Comparison of surface electric field at Maitri and Vostok shows that the parallel variation exhibits with each other, but during the period of geomagnetic disturbances, the influence is not much discerned at Vostok.

  2. GPS based daily activity patterns in European red deer and North American elk (Cervus elaphus): indication for a weak circadian clock in ungulates.

    Science.gov (United States)

    Ensing, Erik P; Ciuti, Simone; de Wijs, Freek A L M; Lentferink, Dennis H; Ten Hoedt, André; Boyce, Mark S; Hut, Roelof A

    2014-01-01

    Long-term tracking using global positioning systems (GPS) is widely used to study vertebrate movement ecology, including fine-scale habitat selection as well as large-scale migrations. These data have the potential to provide much more information about the behavior and ecology of wild vertebrates: here we explore the potential of using GPS datasets to assess timing of activity in a chronobiological context. We compared two different populations of deer (Cervus elaphus), one in the Netherlands (red deer), the other in Canada (elk). GPS tracking data were used to calculate the speed of the animals as a measure for activity to deduce unbiased daily activity rhythms over prolonged periods of time. Speed proved a valid measure for activity, this being validated by comparing GPS based activity data with head movements recorded by activity sensors, and the use of GPS locations was effective for generating long term chronobiological data. Deer showed crepuscular activity rhythms with activity peaks at sunrise (the Netherlands) or after sunrise (Canada) and at the end of civil twilight at dusk. The deer in Canada were mostly diurnal while the deer in the Netherlands were mostly nocturnal. On an annual scale, Canadian deer were more active during the summer months while deer in the Netherlands were more active during winter. We suggest that these differences were mainly driven by human disturbance (on a daily scale) and local weather (on an annual scale). In both populations, the crepuscular activity peaks in the morning and evening showed a stable timing relative to dawn and dusk twilight throughout the year, but marked periods of daily a-rhythmicity occurred in the individual records. We suggest that this might indicate that (changes in) light levels around twilight elicit a direct behavioral response while the contribution of an internal circadian timing mechanism might be weak or even absent.

  3. Seasonal abundance & role of predominant Japanese encephalitis vectors Culex tritaeniorhynchus & Cx. gelidus Theobald in Cuddalore district, Tamil Nadu.

    Science.gov (United States)

    Ramesh, D; Muniaraj, M; Samuel, P Philip; Thenmozhi, V; Venkatesh, A; Nagaraj, J; Tyagi, B K

    2015-12-01

    Japanese encephalitis (JE) is the leading cause of viral encephalitis in Asia. The first major JE outbreak occurred in 1978 and since 1981 several outbreaks had been reported in the Cuddalore district (erstwhile South Arcot), Tamil Nadu, India. Entomological monitoring was carried out during January 2010 - March 2013, to determine the seasonal abundance and transmission dynamics of the vectors of JE virus, with emphasis on the role of Culex tritaeniorhynchus and Cx. gelidus. Mosquito collections were carried out fortnightly during dusk hours in three villages viz. Soundara Solapuram, Pennadam, Erappavur of Cuddalore district. Mosquitoes were collected during dusk for a period of one hour in and around the cattle sheds using oral aspirator and torch light. The collected mosquitoes were later identified and pooled to detect JE virus (JEV) infection by enzyme linked immunosorbent assay (ELISA). A total of 46,343 mosquitoes comprising of 25 species and six genera were collected. Species composition included viz, Cx. tritaeniorhynchus (46.26%), Cx. gelidus (43.12%) and other species (10.62%). A total of 17,678 specimens (403 pools) of Cx. gelidus and 14,358 specimens (309 pools) of Cx. tritaeniorhynchus were tested, of which 12 pools of Cx. gelidus and 14 pools of Cx. tritaeniorhynchus were positive for JE virus antigen. The climatic factors were negatively correlated with minimum infection rate (MIR) for both the species, except mean temperature (P<0.05) for Cx. gelidus. High abundance of Cx. tritaeniorhynchus and Cx. gelidus was observed compared to other mosquito species in the study area. Detection of JEV antigen in the two species confirmed the maintenance of virus. Appropriate vector control measures need to be taken to reduce the vector abundance.

  4. Statistical research on the motion properties of the magnetotail current sheet:Cluster observations

    Institute of Scientific and Technical Information of China (English)

    H.REME; E.LUCEK

    2010-01-01

    The origin of the flapping motion of the earth’s magnetotail current sheet is one of the most important problems in the magnetotail dynamics.Using Cluster data,we make a statistical research on the motion properties of the magnetotail current sheet of 2001 and 2003.We calculate the velocities of the magnetotail current sheet using new methods and obtain the distribution of the magnetotail current sheet velocities in the X-Y plane in GSE coordinate system.Our results show that although most of the current sheets were propagating toward the tail flanks and those of the exceptions lay in dusk side,which is consistent with previous studies,the proportions of the current sheet which were propagating toward midnight (where |YGSE|=0) were higher than those in previous studies.Motions of the current sheet in the middle area (|YGSE|<8 Re) of the magnetotail are investigated.Relatively high value of the Z component of the velocity further confirms that the middle area of the magnetotail might be a source region for the motion of the current sheets which were propagating towards the tail flanks.According to our case studies,the way the current sheets propagated toward midnight area differs significantly from that toward dusk and dawn side,from which we infer that there might be two different kinds of current sheet motions originated from different sources.The statistical results of this paper may give some clues for further studies on the origin of the flapping motion of the magnetotail current sheet.

  5. Coordinated ground-based and Cluster observations of large amplitude global magnetospheric oscillations during a fast solar wind speed interval

    Directory of Open Access Journals (Sweden)

    I. R. Mann

    Full Text Available We present magnetospheric observations of very large amplitude global scale ULF waves, from 9 and 10 December 2000 when the upstream solar wind speed exceeded 600 km/s. We characterise these ULF waves using ground-based magnetometer, radar and optical instrumentation on both the dawn and dusk flanks; we find evidence to support the hypothesis that discrete frequency field line resonances (FLRs were being driven by magnetospheric waveguide modes. During the early part of this interval, Cluster was on an outbound pass from the northern dusk side magnetospheric lobe into the magnetosheath, local-time conjugate to the Canadian sector. In situ magnetic fluctuations, observed by Cluster FGM, show evidence of quasi-periodic motion of the magnetosheath boundary layer with the same period as the ULF waves seen on the ground. Our observations represent the first simultaneous magnetometer, radar and optical observations of the characteristics of FLRs, and confirm the potential importance of ULF waves for magnetosphere-ionosphere coupling, particularly via the generation and modulation of electron precipitation into the ionosphere. The in situ Cluster measurements support the hypothesis that, during intervals of fast solar wind speed, the Kelvin-Helmholtz instability (KHI can excite magnetospheric waveguide modes which bathe the flank magnetosphere with discrete frequency ULF wave power and drive large amplitude FLRs. 

    Paper submitted to the special issue devoted to "Cluster: First scientific results", Ann. Geophysicae, 19, 10/11/12, 2001.

    Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; MHD waves and instabilities; solar wind-magnetosphere interactions

  6. Observation of Neutral Sodium above Mercury During the Transit of November 8, 2006

    Science.gov (United States)

    Potter, Andrew E.; Killen, R. M.; Reardon, K. P.; Bida, T. A.

    2012-10-01

    We mapped the absorption of sunlight by sodium vapor in the exosphere of Mercury during the transit of Mercury on November 8, 2006, using the IBIS Interferometric BIdimensional Spectrometer at the Dunn solar telescope operated by the National Solar Observatory at Sunspot, New Mexico. The measurements were reduced to line-of-sight equivalent widths for absorption at the sodium D2 line, and mapped in thirty degree increments around the shadow of Mercury. We observed north and south polar enhancements of sodium absorption. The sodium absorptions fell off exponentially with altitude up to about 600 km, and we analyzed the altitude distributions to determine surface densities, zenith column densities, temperatures and scale heights for sodium. The average surface concentration of sodium atoms was about 900 atoms/cm3, and the average zenith column density was 0.8 x 1010 atoms/cm2. The average temperature was about 1100 K, with excursions to 1750 and 700 K. The 2003 transit was observed by Schleicher et al. [2004], using instrumentation similar to that employed for this research. They reported the appearance of a streamer-like feature extending a thousand kilometers above the north polar region, and a similar but smaller feature above the south polar region. Our observations did not detect similar features. They observed considerably more sodium absorption over the dawn terminator than over the dusk terminator. In contrast, we observed slightly larger sodium absorption on the dawn relative to the dusk side. The difference might be due to the slow advance of the dawn terminator at during the 2006 transit (0.13 degrees/day) relative to the 2003 transit (3.27 degrees/day). Reference Schleicher, H.; Wiedemann, G.; Wöhl, H.; Berkefeld, T.; Soltau, D. (2004), Detection of neutral sodium above Mercury during the transit on 2003 May 7. Astronomy and Astrophysics, 425, 1119-1124

  7. THEMIS measurements of quasi-static electric fields in the inner magnetosphere

    Science.gov (United States)

    Califf, S.; Li, X.; Blum, L.; Jaynes, A.; Schiller, Q.; Zhao, H.; Malaspina, D.; Hartinger, M.; Wolf, R. A.; Rowland, D. E.; Wygant, J. R.; Bonnell, J. W.

    2014-12-01

    We use 4 years of Time History of Events and Macroscale Interactions during Substorms (THEMIS) double-probe measurements to offer, for the first time, a complete picture of the dawn-dusk electric field covering all local times and radial distances in the inner magnetosphere based on in situ equatorial observations. This study is motivated by the results from the CRRES mission, which revealed a local maximum in the electric field developing near Earth during storm times, rather than the expected enhancement at higher L shells that is shielded near Earth as suggested by the Volland-Stern model. The CRRES observations were limited to the duskside, while THEMIS provides complete local time coverage. We show strong agreement with the CRRES results on the duskside, with a local maximum near L = 4 for moderate levels of geomagnetic activity and evidence of strong electric fields inside L = 3 during the most active times. The extensive data set from THEMIS also confirms the day/night asymmetry on the duskside, where the enhancement is closest to Earth in the dusk-midnight sector, and is farther away closer to noon. A similar, but smaller in magnitude, local maximum is observed on the dawnside near L = 4. The noon sector shows the smallest average electric fields, and for more active times, the enhancement develops near L = 7 rather than L = 4. We also investigate the impact of the uncertain boom-shorting factor on the results and show that while the absolute magnitude of the electric field may be underestimated, the trends with geomagnetic activity remain intact.

  8. Observations of a Unique Type of ULF Waves by Low-Latitude Space Technology 5 Satellites

    Science.gov (United States)

    Le, G.; Chi, P. J.; Strangeway, R. J.; Slavin, J. A.

    2011-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, and sun synchronous polar orbit with 105.6deg inclination angle. Due to the Earth s rotation and the dipole tilt effect, the spacecraft s dawn-dusk orbit track can reach as low as subauroral latitudes during the course of a day. Whenever the spacecraft traverse across the dayside closed field line region at subauroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc 2-3 frequency range. These Pc 2-3 waves appear as wave packets with durations in the order of 5-10 minutes. As the maximum separations of the ST-5 spacecraft are in the order of 10 minutes, the three ST-5 satellites often observe very similar wave packets, implying these wave oscillations occur in a localized region. The coordinated ground-based magnetic observations at the spacecraft footprints, however, do not see waves in the Pc 2-3 band; instead, the waves appear to be the common Pc 4-5 waves associated with field line resonances. We suggest that this unique Pc 2-3 waves seen by ST-5 are in fact the Doppler-shifted Pc 4-5 waves as a result of rapid traverse of the spacecraft across the resonant field lines azimuthally at low altitudes. The observations with the unique spacecraft dawn-disk orbits at proper altitudes and magnetic latitudes reveal the azimuthal characteristics of field-aligned resonances.

  9. Observations of a Unique Type of ULF Waves by Low-Latitude Space Technology Five Mission

    Science.gov (United States)

    Le, G.; Chi, P.; Strangeway, R. J.; Slavin, J. A.

    2011-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, and sun synchronous polar orbit with 105.6deg inclination angle. Due to the Earth s rotation and the dipole tilt effect, the spacecraft s dawn-dusk orbit track can reach as low as subauroral latitudes during the course of a day. Whenever the spacecraft traverse across the dayside closed field line region at subauroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc 2-3 frequency range. These Pc 2-3 waves appear as wave packets with durations in the order of 5-10 minutes. As the maximum separations of the ST-5 spacecraft are in the order of 10 minutes, the three ST-5 satellites often observe very similar wave packets, implying these wave oscillations occur in a localized region. The coordinated ground-based magnetic observations at the spacecraft footprints, however, do not see waves in the Pc 2-3 band; instead, the waves appear to be the common Pc 4-5 waves associated with field line resonances. We suggest that these unique Pc 2-3 waves seen by ST-5 are in fact the Doppler-shifted Pc 4-5 waves as a result of rapid traverse of the spacecraft across the resonant field lines azimuthally at low altitudes. The observations with the unique spacecraft dawn-disk orbits at proper altitudes and magnetic latitudes reveal the azimuthal characteristics of field-aligned resonances.

  10. Observations of a Unique Type of ULF Waves by Low-Latitude Space Technology 5 Mission

    Science.gov (United States)

    Le, Guan; Chi, P.; Strangeway, R. J.; Slavin, J. A.

    2011-01-01

    We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, and sun synchronous polar orbit with 105.6 inclination angle. Due to the Earth's rotation and the dipole tilt effect, the spacecraft's dawn-dusk orbit track can reach as low as sub auroral latitudes during the course of a day. Whenever the spacecraft traverse across the dayside closed field line region at sub auroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc 2-3 frequency range. These Pc 2-3 waves appear as wave packets with durations in the order of 5-10 minutes. As the maximum separations of the ST-5 spacecraft are in the order of 10 minutes, the three ST -5 satellites often observe very similar wave packets, implying these wave oscillations occur in a localized region. The coordinated ground-based magnetic observations at the spacecraft footprints, however, do not see waves in the Pc 2-3 band; instead, the waves appear to be the common Pc 4-5 waves associated with field line resonances. We suggest that these unique Pc 2-3 waves seen by ST-5 are in fact the Doppler-shifted Pc 4-5 waves as a result of rapid traverse of the spacecraft across the resonant field lines azimuthally at low altitudes. The observations with the unique spacecraft dawn-disk orbits at proper altitudes and magnetic latitudes reveal the azimuthal characteristics of field-aligned resonances.

  11. Space Technology 5 (ST-5) Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents

    Science.gov (United States)

    Le, Guan

    2010-01-01

    Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total RI currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of approx. 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

  12. Energetic electron bursts in the plasma sheet and their relation with BBFs

    Science.gov (United States)

    Duan, A. Y.; Cao, J. B.; Dunlop, M.; Wang, Z. Q.

    2014-11-01

    We studied energetic electron bursts (EEBs) (40-250 keV) in the plasma sheet (PS) and their relation to bursty bulk flows (BBFs) using the data recorded by Cluster from 2001 to 2009. The EEBs in the PS can be classified into four types. Three types of EEBs are dispersionless, including EEBs accompanied with BBFs (V > 250 km/s) but without dipolarization front (DF); EEBs accompanied with both dipolarization front (DF) and BBF; and EEBs accompanied with DF and fast flow with V EEB, i.e., EEBs not accompanied with BBFs and DFs, is dispersed. The energetic electrons (40-130 keV) can be easily transported earthward by BBFs due to the strong dawn-dusk electric field embedded in BBFs. The DFs in BBFs can produce energetic electrons (40 to 250 keV). For the EEBs with DF and BBFs, the superposed epoch analyses show that the increase of energetic electron flux has two phases: gradual increase phase before DF and rapid increase phase concurrent with DF. In the PS around x = -18 RE, 60%-70% of EEBs are accompanied with BBFs, indicating that although hitherto there have been various acceleration mechanisms of energetic electrons, most of the energetic electrons in the PS are related with magnetic reconnection, and they are produced either directly by magnetic reconnection or indirectly by the DFs within BBFs. In the BBF's braking region of -12 RE EEBs are accompanied with BBFs. The corresponding ratio between EEBs and BBFs shows a dawn-dusk asymmetry.

  13. GPS based daily activity patterns in European red deer and North American elk (Cervus elaphus: indication for a weak circadian clock in ungulates.

    Directory of Open Access Journals (Sweden)

    Erik P Ensing

    Full Text Available Long-term tracking using global positioning systems (GPS is widely used to study vertebrate movement ecology, including fine-scale habitat selection as well as large-scale migrations. These data have the potential to provide much more information about the behavior and ecology of wild vertebrates: here we explore the potential of using GPS datasets to assess timing of activity in a chronobiological context. We compared two different populations of deer (Cervus elaphus, one in the Netherlands (red deer, the other in Canada (elk. GPS tracking data were used to calculate the speed of the animals as a measure for activity to deduce unbiased daily activity rhythms over prolonged periods of time. Speed proved a valid measure for activity, this being validated by comparing GPS based activity data with head movements recorded by activity sensors, and the use of GPS locations was effective for generating long term chronobiological data. Deer showed crepuscular activity rhythms with activity peaks at sunrise (the Netherlands or after sunrise (Canada and at the end of civil twilight at dusk. The deer in Canada were mostly diurnal while the deer in the Netherlands were mostly nocturnal. On an annual scale, Canadian deer were more active during the summer months while deer in the Netherlands were more active during winter. We suggest that these differences were mainly driven by human disturbance (on a daily scale and local weather (on an annual scale. In both populations, the crepuscular activity peaks in the morning and evening showed a stable timing relative to dawn and dusk twilight throughout the year, but marked periods of daily a-rhythmicity occurred in the individual records. We suggest that this might indicate that (changes in light levels around twilight elicit a direct behavioral response while the contribution of an internal circadian timing mechanism might be weak or even absent.

  14. Asymmetry of the Venus nightside ionosphere: Magnus force effects

    Science.gov (United States)

    Pérez-de-Tejada, H.

    2008-11-01

    A study of the dawn-dusk asymmetry of the Venus nightside ionosphere is conducted by examining the configuration of the ionospheric trans-terminator flow around Venus and also the dawn-ward displacement of the region where most of the ionospheric holes and the electron density plateau profiles are observed (dawn meaning the west in the retrograde rotation of Venus and that corresponds to the trailing side in its orbital motion). The study describes the position of the holes and the density plateau profiles which occur at neighboring locations in a region that is scanned as the trajectory of the Pioneer Venus Orbiter (PVO) sweeps through the nightside hemisphere with increasing orbit number. The holes are interpreted as crossings through plasma channels that extend downstream from the magnetic polar regions of the Venus ionosphere and the plateau profiles represent cases in which the electron density maintains nearly constant values in the upper ionosphere along the PVO trajectory. From a collection of PVO passes in which these profiles were observed it is found that they appear at neighboring positions of the ionospheric holes in a local solar time (LST) map including cases where only a density plateau profile or an ionospheric hole was detected. It is argued that the ionospheric holes and the density plateau profiles have a common origin at the magnetic polar regions where plasma channels are formed and that the density plateau profiles represent crossings through a friction layer that is adjacent to the plasma channels. It is further suggested that the dawn-dusk asymmetry in the position of both features in the nightside ionosphere results from a fluid dynamic force (Magnus force) that is produced by the combined effects of the trans-terminator flow and the rotational motion of the ionosphere that have been inferred from the PVO measurements.

  15. Entomological investigations into an epidemic of Japanese encephalitis (JE in northern districts of West Bengal, India (2011-2012

    Directory of Open Access Journals (Sweden)

    T Mariappan

    2014-01-01

    Full Text Available Background & objectives: Japanese encephalitis (JE is one of the most important arboviral diseases of human beings with outbreaks in many parts of Southeast Asia including India. We present the entomological findings of an outbreak occurred in northern part of West Bengal during 2011-2012 with special emphasis on the role of JE vectors in different seasons. Methods: Adult mosquito collections were made with the help of mouth aspirators, aided by flash lights during day time resting inside human and animal habitations as indoor, and resting outside field grasses, bushes, underneath of culverts and bridges as outdoor, and in and around the pig enclosures and cattle sheds during dusk period in JE affected villages from Cooch Behar, Dakshin Dinajpur, Darjeeling and Jalpaiguri districts in North West Bengal. In all study villages, a long handled with enamel bowl dipper was used to obtain immature stages of mosquitoes from various breeding habitats. Results: A total of 19 different types of mosquito breeding habitats were examined for vectors of JE. From these habitats, 23.7 per cent were positive for breeding during the study period. Overall, nine different species were recorded through emergence, but none was positive for JE virus when subjected for detection of virus. Adult mosquitoes of more than 50 per cent of the potential JE vector species obtained through dusk and the rest through indoor and outdoor collections in all seasons. Altogether, 27 different species were recorded. Most of these were JE vectors. Interpretation & conclusions: Our results showed that in addition to Cx. vishnui subgroup, detection of JE virus antigen in Cx. quinquefasciatus indicated the possible maintenance of JE virus in nature through poor vector mosquitoes throughout the year. Since, all potential vector species reported elsewhere in India were also found in this region and fluctuated in density in different seasons, a proper integrated vector control programme needs

  16. Climatology of the inter-hemispheric field-aligned currents system over the Nigeria ionosphere

    Science.gov (United States)

    Bolaji, O. S.; Rabiu, A. B.; Oyeyemi, E. O.; Yumoto, K.

    2012-11-01

    Records of the declination (D) magnetic field data for the year 2009 from the Magnetic Data Acquisition System (MAGDAS) facilities at University of Ilorin were employed for this work. From the minutes value of the D-component, the deduced hourly values of the D-component (Sq(QD)) were used to estimate its diurnal (Sq(D)) values with the most five quietest days identified. The monthly mean (MSq(D)) of the most five quietest days and their seasonal (SSq(D)) variabilities were investigated. The inter-hemispheric field aligned currents (IHFACs) exhibit downward and upward inter-hemispheric field-aligned sheet current that appears as a pair at all local times of the Sq(D), MSq(D), and SSq(D) variations. From these variabilities, the IHFACs were observed to flow from the winter to summer hemisphere during noon and dusk sector and flowing in opposite direction during the dawn sector. The Sq(D) variability patterns that were observed in May, June, August September are gentle compared to the disturbed variabilities in January, February, March and November. The highest positive (˜1.7 arc-min) and negative (˜-2.7 arc min) MSq(D) maxima values were observed in August during the dawn and noon sectors respectively. These values indicated that the IHFACs flow in August is strongly southbound (positive) and northbound (negative) in the dawn and noon sectors respectively. Dusk-side IHFACs as can be observed by MAGDAS are weakly northbound in all the seasons. The direction of IHFACs does not flip at the equinoxes but in June and November and does not become largest at solstices but in August. The IHFACs was observed to exhibit longitudinal variability, which indicated that larger amplitude of winter-to-summer IHFACs is observed to be greater in June solstice (northbound/negative IHFACs) than in the December solstice (southbound/positive IHFACs) during the noon sector.

  17. Magnetic reconnection in Saturn's magnetotail: A comprehensive magnetic field survey.

    Science.gov (United States)

    Smith, A. W.; Jackman, C. M.; Thomsen, M. F.; Dougherty, M. K.

    2015-10-01

    Magnetic reconnection is a fundamental process throughout the solar system, significantly shaping and modulating the magnetospheres of the magnetized planets. Within planetary magnetotails reconnection can be responsible for energizing particles and potentially changing the total flux and mass contained within the magnetosphere. The Kronian magnetosphere is thought to be a middle ground between the rotationally dominated Jovian magnetosphere and the solar wind driven terrestrial magnetosphere. However, previous studies have not been able to find a statistical reconnection x-line, as has been possible at both Jupiter and Earth. Additionally the standard picture of magnetotail reconnection at Saturn, developed by Cowley et al. [2004], suggests a potential asymmetry between the dawn and dusk flanks, caused by different reconnection processes dominating. This work centers on the development of an algorithm designed to find reconnection related events in spacecraft magnetometer data, aiming to reduce the bias that manual searches could inherently introduce, thereby ensuring the validity of any statistical analysis. The algorithm primarily identifies the reconnection related events from deflections in the north-south component of the magnetic field, allowing an almost uninterrupted in-situ search (when the spacecraft is situated within the magnetotail). The new catalogue of candidate reconnection events, produced by the algorithm, enables a more complete statistical view of reconnection in the Kronian magnetotail. Well-studied data encompassing the deep magnetotail and dawn flank (particularly from orbits in 2006) were used to train the algorithm and develop reasonable criteria. The algorithm was then applied to data encompassing the dusk flank (including orbits from 2009, for which plasma data have been examined by Thomsen et al. [2014]). This combination enables a robust, and global, comparison of reconnection rates, signatures and properties in the Kronian magnetotail.

  18. Photoperiodic and thermosensory pathways interact through CONSTANS to promote flowering at high temperature under short days.

    Science.gov (United States)

    Fernández, Virginia; Takahashi, Yasuyuki; Le Gourrierec, José; Coupland, George

    2016-06-01

    Plants detect changes in day length to induce seasonal patterns of flowering. The photoperiodic pathway accelerates the flowering of Arabidopsis thaliana under long days (LDs) whereas it is inactive under short days (SDs), resulting in delayed flowering. This delay is overcome by exposure of plants to high temperature (27°C) under SDs (27°C-SD). Previously, the high-temperature flowering response was proposed to involve either the impaired activity of MADS-box transcription factor (TF) floral repressors or PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) TF-mediated activation of FLOWERING LOCUS T (FT), which encodes the output signal of the photoperiodic pathway. We integrate these observations by studying several PIFs, the MADS-box SHORT VEGETATIVE PHASE (SVP) and the photoperiodic pathway under 27°C-SD. We find that the mRNAs of FT and its paralogue TWIN SISTER OF FT (TSF) are increased at dusk under 27°C-SD compared with 21°C-SD, and that this requires PIF4 and PIF5 as well as CONSTANS (CO), a TF that promotes flowering under LDs. The CO and PIF4 proteins are present at dusk under 27°C-SD, and they physically interact. Although Col-0 plants flower at similar times under 27°C-SD and 21°C-LD the expression level of FT is approximately 10-fold higher under 21°C-LD, suggesting that responsiveness to FT is also increased under 27°C-SD, perhaps as a result of the reduced activity of SVP in the meristem. Accordingly, only svp-41 ft-10 tsf-1 plants flowered at the same time under 21°C-SD and 27°C-SD. Thus, we propose that under non-inductive SDs, elevated temperatures increase the activity and sensitize the response to the photoperiod pathway.

  19. Kelvin Helmholtz Instability at the Equatorial Magnetotail Boundary: MHD Simulation and Comparison with Geotail Observations

    Science.gov (United States)

    Fairfield, Donald H.; Otto, A.

    1999-01-01

    On March 24, 1995 the Geotail spacecraft observed large fluctuations of the magnetic field and plasma properties in the Low Latitude Boundary Layer (LLBL) about 15 R(sub E) tailward of the dusk meridian. Although the magnetospheric and the magnetosheath field were strongly northward, the B(sub z) component showed strong short duration fluctuations in which B(sub z) could even reach negative values. We have used two-dimensional magnetohydrodynamic simulations with magnetospheric and magnetosheath input parameters specifically chosen for this. Geotail event to identify the processes which cause the observed boundary properties. It is shown that these fluctuations can be explained by the Kelvin-Helmholtz instability if the k vector of the instability has a component along the magnetic field direction. The simulation results show many of the characteristic properties of the Geotail observations. In particular, the quasi-periodic strong fluctuations are well explained by satellite crossings through the Kelvin-Helmholtz vortices. It is illustrated how the interior structure of the Kelvin-Helmholtz vortices leads to the rapid fluctuations in the Geotail observations. Our results suggest an average Kelvin-Helmholtz wavelength of about 5 R(sub E) with a vortex size of close to 2 R(sub E) for an average repetition time of 2.5 minutes. The growth time for these waves implies a source region of about 10 to 16 R(sub E) upstream from the location of the Geotail spacecraft (i.e., near the dusk meridian). The results also indicate a considerable mass transport of magnetosheath material into the magnetosphere by magnetic reconnection in the Kelvin-Helmholtz vortices.

  20. Circadian clock component, LHY, tells a plant when to respond photosynthetically to light in nature.

    Science.gov (United States)

    Joo, Youngsung; Fragoso, Variluska; Yon, Felipe; Baldwin, Ian T; Kim, Sang-Gyu

    2017-08-01

    The circadian clock is known to increase plant growth and fitness, and is thought to prepare plants for photosynthesis at dawn and dusk; whether this happens in nature was unknown. We transformed the native tobacco, Nicotiana attenuata to silence two core clock components, NaLHY (irLHY) and NaTOC1 (irTOC1). We characterized growth and light- and dark-adapted photosynthetic rates (Ac ) throughout a 24 h day in empty vector-transformed (EV), irLHY, and irTOC1 plants in the field, and in NaPhyA- and NaPhyB1-silenced plants in the glasshouse. The growth rates of irLHY plants were lower than those of EV plants in the field. While irLHY plants reduced Ac earlier at dusk, no differences between irLHY and EV plants were observed at dawn in the field. irLHY, but not EV plants, responded to light in the night by rapidly increasing Ac . Under controlled conditions, EV plants rapidly increased Ac in the day compared to dark-adapted plants at night; irLHY plants lost these time-dependent responses. The role of NaLHY in gating photosynthesis is independent of the light-dependent reactions and red light perceived by NaPhyA, but not NaPhyB1. In summary, the circadian clock allows plants not to respond photosynthetically to light at night by anticipating and gating red light-mediated in native tobacco. © 2017 Institute of Botany, Chinese Academy of Sciences.

  1. Adjustments in CAM and enzymatic scavenging of H2O2 in juvenile plants of the epiphytic bromeliad Guzmania monostachia as affected by drought and rewatering.

    Science.gov (United States)

    Carvalho, Victória; Abreu, Maria E; Mercier, Helenice; Nievola, Catarina C

    2017-04-01

    Juvenile plants of epiphytes such as bromeliads are highly prone to dehydration under drought conditions. It is likely that young epiphytes evolved mostly metabolic strategies to resist drought, which may include the plastic modulation of the enzymatic antioxidant system and crassulacean acid metabolism (CAM). Few studies have investigated such strategies in juvenile epiphytes, although such research is important to understand how these plants might face drought intensification derived from potential climatic alterations. The epiphytic CAM bromeliad Guzmania monostachia (L.) Rusby ex Mez var. monostachia is known to have plastic responses to drought, but no reports have focused on the metabolism of juvenile plants to drought and recovery. Hence, we aimed to verify how juvenile G. monostachia plants adjust malate (indicative of CAM), H2O2 content and enzymatic scavenging in response to drought (eight days without irrigation) and rewatering (six days of irrigation post-drought). Interestingly, drought decreased H2O2 content and activities of superoxide dismutase, catalase (CAT) and ascorbate peroxidase (APX) in the pre-dusk period, although glutathione reductase (GR) and CAM activity increased. Rewatering restored H2O2, but activities of APX, CAT and GR exceeded pre-stress levels in the pre-dusk and/or pre-dawn periods. Results suggest that recovery from a first drought redefines the homeostatic balance of H2O2 scavenging, in which rewatered plants stimulate the enzymatic antioxidant system while drought-exposed plants intensify CAM activity to regulate H2O2 content, a photosynthetic pathway known to prevent oxidative stress. Such data show that young G. monostachia plants adjust CAM and H2O2 scavenging to adapt to water availability.

  2. How Does a Carnivore Guild Utilise a Substantial but Unpredictable Anthropogenic Food Source? Scavenging on Hunter-Shot Ungulate Carcasses by Wild Dogs/Dingoes, Red Foxes and Feral Cats in South-Eastern Australia Revealed by Camera Traps

    Science.gov (United States)

    Forsyth, David M.; Woodford, Luke; Moloney, Paul D.; Hampton, Jordan O.; Woolnough, Andrew P.; Tucker, Mark

    2014-01-01

    There is much interest in understanding how anthropogenic food resources subsidise carnivore populations. Carcasses of hunter-shot ungulates are a potentially substantial food source for mammalian carnivores. The sambar deer (Rusa unicolor) is a large (≥150 kg) exotic ungulate that can be hunted throughout the year in south-eastern Australia, and hunters are not required to remove or bury carcasses. We investigated how wild dogs/dingoes and their hybrids (Canis lupus familiaris/dingo), red foxes (Vulpes vulpes) and feral cats (Felis catus) utilised sambar deer carcasses during the peak hunting seasons (i.e. winter and spring). We placed carcasses at 1-km intervals along each of six transects that extended 4-km into forest from farm boundaries. Visits to carcasses were monitored using camera traps, and the rate of change in edible biomass estimated at ∼14-day intervals. Wild dogs and foxes fed on 70% and 60% of 30 carcasses, respectively, but feral cats seldom (10%) fed on carcasses. Spatial and temporal patterns of visits to carcasses were consistent with the hypothesis that foxes avoid wild dogs. Wild dog activity peaked at carcasses 2 and 3 km from farms, a likely legacy of wild dog control, whereas fox activity peaked at carcasses 0 and 4 km from farms. Wild dog activity peaked at dawn and dusk, whereas nearly all fox activity occurred after dusk and before dawn. Neither wild dogs nor foxes remained at carcasses for long periods and the amount of feeding activity by either species was a less important predictor of the loss of edible biomass than season. Reasons for the low impacts of wild dogs and foxes on sambar deer carcass biomass include the spatially and temporally unpredictable distribution of carcasses in the landscape, the rapid rate of edible biomass decomposition in warm periods, low wild dog densities and the availability of alternative food resources. PMID:24918425

  3. Photoperiodic regulation of flowering time through periodic histone deacetylation of the florigen gene FT.

    Directory of Open Access Journals (Sweden)

    Xiaofeng Gu

    2013-09-01

    Full Text Available The developmental transition from a vegetative to a reproductive phase (i.e., flowering is timed by the seasonal cue day length or photoperiod in many plant species. Through the photoperiod pathway, inductive day lengths trigger the production of a systemic flowering signal, florigen, to provoke the floral transition. FLOWERING LOCUS T (FT, widely conserved in angiosperms, is a major component of the mobile florigen. In the long-day plant Arabidopsis, FT expression is rhythmically activated by the output of the photoperiod pathway CONSTANS (CO, specifically at the end of long days. How FT expression is modulated at an adequate level in response to the long-day cue to set a proper flowering time remains unknown. Here, we report a periodic histone deacetylation mechanism for the photoperiodic modulation of FT expression. We have identified a plant-unique core structural component of an Arabidopsis histone deacetylase (HDAC complex. In long days, this component accumulates at dusk, and is recruited by a MADS-domain transcription factor to the FT locus specifically at the end of the day, leading to periodic histone deacetylation of FT chromatin at dusk. Furthermore, we found that at the end of long days CO activity not only activates FT expression but also enables HDAC-activity recruitment to FT chromatin to dampen the level of FT expression, and so prevent precocious flowering in response to the inductive long-day cue. These results collectively reveal a periodic histone deacetylation mechanism for the day-length control of flowering time in higher plants.

  4. Photoperiodic regulation of flowering time through periodic histone deacetylation of the florigen gene FT.

    Science.gov (United States)

    Gu, Xiaofeng; Wang, Yizhong; He, Yuehui

    2013-09-01

    The developmental transition from a vegetative to a reproductive phase (i.e., flowering) is timed by the seasonal cue day length or photoperiod in many plant species. Through the photoperiod pathway, inductive day lengths trigger the production of a systemic flowering signal, florigen, to provoke the floral transition. FLOWERING LOCUS T (FT), widely conserved in angiosperms, is a major component of the mobile florigen. In the long-day plant Arabidopsis, FT expression is rhythmically activated by the output of the photoperiod pathway CONSTANS (CO), specifically at the end of long days. How FT expression is modulated at an adequate level in response to the long-day cue to set a proper flowering time remains unknown. Here, we report a periodic histone deacetylation mechanism for the photoperiodic modulation of FT expression. We have identified a plant-unique core structural component of an Arabidopsis histone deacetylase (HDAC) complex. In long days, this component accumulates at dusk, and is recruited by a MADS-domain transcription factor to the FT locus specifically at the end of the day, leading to periodic histone deacetylation of FT chromatin at dusk. Furthermore, we found that at the end of long days CO activity not only activates FT expression but also enables HDAC-activity recruitment to FT chromatin to dampen the level of FT expression, and so prevent precocious flowering in response to the inductive long-day cue. These results collectively reveal a periodic histone deacetylation mechanism for the day-length control of flowering time in higher plants.

  5. How does a carnivore guild utilise a substantial but unpredictable anthropogenic food source? Scavenging on hunter-shot ungulate carcasses by wild dogs/dingoes, red foxes and feral cats in south-eastern Australia revealed by camera traps.

    Science.gov (United States)

    Forsyth, David M; Woodford, Luke; Moloney, Paul D; Hampton, Jordan O; Woolnough, Andrew P; Tucker, Mark

    2014-01-01

    There is much interest in understanding how anthropogenic food resources subsidise carnivore populations. Carcasses of hunter-shot ungulates are a potentially substantial food source for mammalian carnivores. The sambar deer (Rusa unicolor) is a large (≥ 150 kg) exotic ungulate that can be hunted throughout the year in south-eastern Australia, and hunters are not required to remove or bury carcasses. We investigated how wild dogs/dingoes and their hybrids (Canis lupus familiaris/dingo), red foxes (Vulpes vulpes) and feral cats (Felis catus) utilised sambar deer carcasses during the peak hunting seasons (i.e. winter and spring). We placed carcasses at 1-km intervals along each of six transects that extended 4-km into forest from farm boundaries. Visits to carcasses were monitored using camera traps, and the rate of change in edible biomass estimated at ∼ 14-day intervals. Wild dogs and foxes fed on 70% and 60% of 30 carcasses, respectively, but feral cats seldom (10%) fed on carcasses. Spatial and temporal patterns of visits to carcasses were consistent with the hypothesis that foxes avoid wild dogs. Wild dog activity peaked at carcasses 2 and 3 km from farms, a likely legacy of wild dog control, whereas fox activity peaked at carcasses 0 and 4 km from farms. Wild dog activity peaked at dawn and dusk, whereas nearly all fox activity occurred after dusk and before dawn. Neither wild dogs nor foxes remained at carcasses for long periods and the amount of feeding activity by either species was a less important predictor of the loss of edible biomass than season. Reasons for the low impacts of wild dogs and foxes on sambar deer carcass biomass include the spatially and temporally unpredictable distribution of carcasses in the landscape, the rapid rate of edible biomass decomposition in warm periods, low wild dog densities and the availability of alternative food resources.

  6. How Tiny Collisions Shape Mercury

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    If space rocks are unpleasant to encounter, space dust isnt much better. Mercurys cratered surface tells of billions of years of meteoroid impacts but its thin atmosphere is what reveals its collisional history with smaller impactors. Now new research is providing a better understanding of what were seeing.Micrometeoroids Ho!The inner solar system is bombarded by micrometeoroids, tiny particles of dust (on the scale of a tenth of a millimeter) emitted by asteroids and comets as they make their closest approach to the Sun. This dust doesnt penetrateEarths layers of atmosphere, but the innermost planet of our solar system, Mercury, doesnt have this convenient cushioning.Just as Mercury is affected by the impacts of large meteoroids, its also shaped by the many smaller-scale impacts it experiences. These tiny collisions are thought to vaporize atoms and molecules from the planets surface, which quickly dissociate. This process adds metals to Mercurys exosphere, the planets extremely tenuous atmosphere.Modeling PopulationsDistribution of the directions from which meteoroids originate before impacting Mercurys surface, as averaged over its entire orbit. Local time of 12 hr corresponds to the Sun-facing side. A significant asymmetry is seen between the dawn (6 hrs) and dusk (18 hrs) rates. [Pokorn et al. 2017]The metal distribution in the exosphere provides a way for us to measure the effect of micrometeoroid impacts on Mercury but this only works if we have accurate models of the process. A team of scientists led by Petr Pokorn (The Catholic University of America and NASA Goddard SFC) has now worked to improve our picture of micrometeoroid impact vaporization on Mercury.Pokorn and collaborators argue that two meteoroid populations Jupiter-family comets (short-period) and Halley-type comets (long-period) contribute the dust for the majority of micrometeoroid impacts on Mercury. The authors model the dynamics and evolution of these two populations, reproducing the

  7. Imaging and power generation strategies for Chandrayaan-1

    Indian Academy of Sciences (India)

    Ananth Krishna; N S Gopinath; N S Hegde; N K Malik

    2005-12-01

    The Chandrayaan-1 mission proposes to put a 550 kg lunarcraft into Geostationary Transfer Orbit (GTO)using the Polar Satellite Launch Vehicle (PSLV)which will subsequently be transferred into a 100 km circular lunar polar orbit for imaging purposes.In this paper,we describe certain aspects of mission strategies which will allow optimum power generation and imaging of the lunar surface. The lunar orbit considered is circular and polar and therefore nearly perpendicular to the ecliptic plane.Unlike an Earth orbiting remote sensing satellite,the orbit plane of lunar orbiter is inertially fixed as a consequence of the very small oblateness of the Moon.The Earth rotates around the Sun once a year,resulting in an apparent motion of Sun around this orbit in a year.Two extreme situations can be identified concerning the solar illumination of the lunar orbit,noon/midnight orbit,where the Sun vector is parallel to the spacecraft orbit plane and dawn/dusk orbit,where the Sun vector is perpendicular to the spacecraft orbit plane.This scenario directly affects the solar panel configuration.In case the solar panels are not canted,during the noon/midnight orbit, 100%power is generated,whereas during the dawn/dusk orbit,zero power is generated.Hence for optimum power generation,canting of the panels is essential.Detailed analysis was carriedout to fix optimum canting and also determine a strategy to maintain optimum power generation throughout the year.The analysis led to the strategy of 180° yaw rotation at noon/midnight orbits and flipping the solar panel by 180° at dawn/dusk orbits.This also resulted in the negative pitch face of the lunarcraft to be an anti-sun panel,which is very useful for thermal design,and further to meet cooling requirements of the spectrometers. In principle the Moon ’s surface can be imaged in 28 days,because the orbit chosen and the payload swath provide adequate overlap.However,in reality it is not possible to complete the imaging in 28 days

  8. Saturn's polar ionospheric flows and their relation to the main auroral oval

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2004-04-01

    Full Text Available We consider the flows and currents in Saturn's polar ionosphere which are implied by a three-component picture of large-scale magnetospheric flow driven both by planetary rotation and the solar wind interaction. With increasing radial distance in the equatorial plane, these components consist of a region dominated by planetary rotation where planetary plasma sub-corotates on closed field lines, a surrounding region where planetary plasma is lost down the dusk tail by the stretching out of closed field lines followed by plasmoid formation and pinch-off, as first described for Jupiter by Vasyliunas, and an outer region driven by the interaction with the solar wind, specifically by reconnection at the dayside magnetopause and in the dawn tail, first discussed for Earth by Dungey. The sub-corotating flow on closed field lines in the dayside magnetosphere is constrained by Voyager plasma observations, showing that the plasma angular velocity falls to around half of rigid corotation in the outer magnetosphere, possibly increasing somewhat near the dayside magnetopause, while here we provide theoretical arguments which indicate that the flow should drop to considerably smaller values on open field lines in the polar cap. The implied ionospheric current system requires a four-ring pattern of field-aligned currents, with distributed downward currents on open field lines in the polar cap, a narrow ring of upward current near the boundary of open and closed field lines, and regions of distributed downward and upward current on closed field lines at lower latitudes associated with the transfer of angular momentum from the planetary atmosphere to the sub-corotating planetary magnetospheric plasma. Recent work has shown that the upward current associated with sub-corotation is not sufficiently intense to produce significant auroral acceleration and emission. Here we suggest that the observed auroral oval at Saturn instead corresponds to the ring of

  9. Effect of the IMF By component on the ionospheric flow overhead at EISCAT: observations and theory

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    Full Text Available We have analysed a database of ∼300 h of tristatic ionospheric velocity measurements obtained overhead at Tromsø (66.3° magnetic latitude by the EISCAT UHF radar system, for the presence of flow effects associated with the y-component of the IMF. Since it is already known that the flow depends upon IMF Bz, a least-squares multivariate analysis has been used to determine the flow dependence on both IMF By and Bz simultaneously. It is found that significant flow variations with IMF By occur, predominantly in the midnight sector (∼2100–0300 MLT, but also pre-dusk (∼1600–1700 MLT, which are directed eastward for IMF By positive and westward for IMF By negative. The flows are of magnitude 20–30 m s–1 nT–1 in the midnight sector, and smaller, 10–20 m s–1 nT–1, pre-dusk, and are thus associated with significant changes of flow of order a few hundred m s–1 over the usual range of IMF By of about ±5 nT. At other local times the IMF By-related perturbation flows are much smaller, less than ∼5 m s–1 nT–1, and consistent with zero within the uncertainty estimates. We have investigated whether these IMF By-dependent flows can be accounted for quantitatively by a theoretical model in which the equatorial flow in the inner magnetosphere is independent of IMF By, but where distortions of the magnetospheric magnetic field associated with a "penetrating" component of the IMF By field changes the mapping of the field to the ionosphere, and hence the ionospheric flow. We find that the principal flow perturbation produced by this effect is an east-west flow whose sense is determined by the north-south component of the unperturbed flow. Perturbations in the north-south flow are typically smaller by more than an order of magnitude, and generally negligible in terms of observations. Using equatorial flows which are determined from EISCAT data for zero IMF By, to which the corotation flow has been added, the theory predicts the presence

  10. The diel vertical migration patterns and individual swimming behavior of overwintering sprat Sprattus sprattus

    Science.gov (United States)

    Solberg, Ingrid; Kaartvedt, Stein

    2017-02-01

    We addressed the behavioral patterns and DVM dynamics of sprat overwintering in a Norwegian fjord (150 m) with increasing hypoxia by depth. An upward-facing echosounder deployed at the bottom and cabled to shore provided 4 months of continuous acoustic data. This enabled detailed studies of individual behavior, specifically allowing assessment of individual vertical migrations at dusk and dawn in relation to light, analysis of so-called rise-and-sink swimming, and investigation of the sprat' swimming activity and behavior in severely hypoxic waters. Field campaigns supplemented the acoustic studies. The acoustic records showed that the main habitat for sprat was the upper ∼65 m where oxygen concentrations were ⩾0.7 mL O2 L-1. The sprat schooled at ∼50 m during daytime and initiated an upward migration about 1 h prior to sunset. While some sprat migrated to surface waters, other individuals interrupted the ascent when at ∼20-30 m, and returned to deeper waters ∼20-50 min after sunset. Sprat at depth was on average larger, yet individuals made excursions to- and from upper layers. Sprat were swimming in a "rise and sink" pattern at depth, likely related to negative buoyancy. Short-term dives into waters with less than 0.45 mL O2 L-1 were interpreted as feeding forays for abundant overwintering Calanus spp. The deep group of sprat initiated a dawn ascent less than 1 h before sunrise, ending at 20-30 m where they formed schools. They subsequently returned to deeper waters about ∼20 min prior to sunrise. Measurements of surface light intensities indicated that the sprat experienced lower light levels in upper waters at dawn than at dusk. The vertical swimming speed varied significantly between the behavioral tasks. The mixed DVM patterns and dynamic nocturnal behavior of sprat persisted throughout winter, likely shaped by individual strategies involving optimized feeding and predator avoidance, as well as relating to temperature, hypoxia and negative

  11. Morphology of the ring current derived from magnetic field observations

    Directory of Open Access Journals (Sweden)

    G. Le

    2004-04-01

    Full Text Available Our examination of the 20 years of magnetospheric magnetic field data from ISEE, AMPTE/CCE and Polar missions has allowed us to quantify how the ring current flows and closes in the magnetosphere at a variety of disturbance levels. Using intercalibrated magnetic field data from the three spacecraft, we are able to construct the statistical magnetic field maps and derive 3-dimensional current density by the simple device of taking the curl of the statistically determined magnetic field. The results show that there are two ring currents, an inner one that flows eastward at ~3 RE and a main westward ring current at ~4–7 RE for all levels of geomagnetic disturbances. In general, the in-situ observations show that the ring current varies as the Dst index decreases, as we would expect it to change. An unexpected result is how asymmetric it is in local time. Some current clearly circles the magnetosphere but much of the energetic plasma stays in the night hemisphere. These energetic particles appear not to be able to readily convect into the dayside magnetosphere. During quiet times, the symmetric and partial ring currents are similar in strength (~0.5MA and the peak of the westward ring current is close to local midnight. It is the partial ring current that exhibits most drastic intensification as the level of disturbances increases. Under the condition of moderate magnetic storms, the total partial ring current reaches ~3MA, whereas the total symmetric ring current is ~1MA. Thus, the partial ring current contributes dominantly to the decrease in the Dst index. As the ring current strengthens the peak of the partial ring current shifts duskward to the pre-midnight sector. The partial ring current is closed by a meridional current system through the ionosphere, mainly the field-aligned current, which maximizes at local times near the dawn and dusk. The closure currents flow in

  12. Quiet-time Pc 5 pulsations in the Earth's magnetotail: IMP-8, ISEE-1 and ISEE-3 simultaneous observations

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    D. V. Sarafopoulos

    Full Text Available Quasi-periodic Pc 5 pulsations have been reported inside and just outside the Earth's magnetotail during intervals of low geomagnetic activity. In order to further define their characteristics and spatial extent, we present three case studies of simultaneous magnetic field and plasma observations by IMP-8, ISEE-1 (and ISEE-2 in one case in the Earth's magnetotail and ISEE-3 far upstream of the bow shock, during intervals in which the spacecraft were widely separated. In the first case study, similar pulsations are observed by IMP-8 at the dawn flank of the plasma sheet and by ISEE-1 near the plasma sheet boundary layer (PSBL near midnight local time. In the second case study, simultaneous pulsations are observed by IMP-8 in the dusk magnetosheath and by ISEE-1 and 2 in the dawn plasma sheet. In the third case study, simultaneous pulsations are observed in the north plasma sheet boundary layer and the south plasma sheet. We conclude that the pulsations occur simultaneously throughout much of the nightside magnetosphere and the surrounding magnetosheath, i.e. that they have a global character. Some additional findings are the following: (a the observed pulsations are mixed mode compressional and transverse, where the compressional character is more apparent in the close vicinity of the plane ZGSM=0; (b the compressional pulsations of the magnetic field in the dusk magnetosheath show peaks that coincide (almost one-to-one with similar peaks observed inside the dawn plasma sheet; (c in the second case study the polarization sense of the magnetic field and the recurrent left-hand plasma vortices observed in the dawn plasma sheet are consistent with anti-sunward moving waves on the magneto-pause; (d pulsation amplitudes are weaker in the PSBL(or lobe as compared with those in the magneto-tail's flanks, suggesting a decay with distance from the magnetopause; (e the thickness of the plasma sheet (under extremely quiet

  13. Differential expression of melanopsin mRNA and protein in Brown Norwegian rats.

    Science.gov (United States)

    Hannibal, Jens; Georg, Birgitte; Fahrenkrug, Jan

    2013-01-01

    Melanopsin is expressed in a subpopulation of retinal ganglion cells rendering these cells intrinsically photosensitive (ipRGCs). The ipRGCs are the primary RGCs mediating light entrainment of the circadian clock and control of the pupillary light reflex, light regulated melatonin secretion and negative masking behaviour. Previous studies have demonstrated that melanopsin expression in albino rats is regulated by light and darkness. The present study was undertaken to study the influence of light and darkness during the circadian day and after extended periods of constant light and darkness on melanopsin expression in the pigmented retina of the Brown Norwegian rat (Rattus norvegicus). The diurnal and circadian expressions were examined in retinal extracts from rats euthanized every 4 h during a 24 h light/dark (LD) and a 24 h dark cycle (DD) using quantitative real-time PCR and Western blotting. To study whether light regulates melanopsin expression, rats were sacrificed after being placed in either constant light (LL) or darkness for 3 or 21 d. Flat mount retinas from animals kept during either LL or DD were also examined by immunohistochemistry. Melanopsin mRNA expression displayed a significant rhythmic change during the LD cycle with peak expression around dusk and nadir at dawn. Melanopsin protein also changed over the LD cycle with peak expression at the end of the night and nadir at dusk. Rhythmic expression of melanopsin mRNA but not melanopsin protein was found in constant darkness. After 3 or 21 d in either LL or DD melanopsin mRNA expression was unaltered. Melanopsin protein was at the same high level after 3 and 21 d in DD, whereas a significant decrease was found after prolonging the light period for 3 or 21 d. The change in melanopsin protein was primarily due to change in immunoreactivity in the dendritic processes. In conclusion we found that light and darkness are important for regulation of melanopsin protein expression whereas input from a

  14. A statistical study of the THEMIS satellite data for plasma sheet electrons carrying auroral upward field-aligned currents

    Science.gov (United States)

    Lee, S.; Shiokawa, K.; McFadden, J. P.

    2010-12-01

    -aligned potential difference, particularly during active time (AE > 100 nT). On the other hand, in the dusk side outer magnetosphere (source of the region 1), electron density and temperature are small, thus the thermal current is much smaller than the typical auroral current suggested by Iijima and Potemra (JGR, 1976). From this result, we suppose that electron acceleration is necessary on the dusk side region 1 upward field-aligned current. Our preliminary result, however, does not consider contamination of the radiation belt particles into the ESA data that is apparent inside 9 Re. In the presentation, we show the results with removal of the radiation belt particle contamination.

  15. Calcium in Mercury's Exosphere: Modeling MESSENGER Data

    Science.gov (United States)

    Burger, M. H.; Killen, R. M.; McClintock, W. E.; Merkel, A. W.; Vervack, R. J.; Sarantos, M.; Sprague, A. L.

    2011-12-01

    Mercury is surrounded by a surface-bounded exosphere known to contain hydrogen, sodium, potassium, calcium, and magnesium. Because the exosphere is collisionless, its composition represents a balance of active source and loss processes. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has made high-spatial-resolution observations of sodium, calcium, and magnesium near Mercury's surface and in the extended, anti-sunward direction. The most striking feature of these data is the substantial differences among species, which was detected during three close flybys of the planet and has been persistantly present during MESSENGER's orbital phase. Our modeling demonstrates that these differences are not because of post-ejection dynamics such as differences in photo-ionization rate and radiation pressure, but rather result from differences in the source mechanisms and regions on the surface from which each species is ejected. The observations of calcium have revealed a strong dawn/dusk asymmetry, with the abundance over the dawn hemisphere substantially greater than that on the dusk side. To understand this asymmetry, we use a Monte Carlo model of Mercury's exosphere that we developed to track the motions of exospheric neutrals under the influence of gravity and radiation pressure. In this model, Ca atoms can be ejected directly from the surface or produced by ejection of CaO followed by dissociation to produce Ca and O. Particles are removed from the system if they stick to the surface or escape from the model region of interest (within 15 Mercury radii). Photoionization reduces the final weighting given to each particle when simulating the Ca radiance. Data from the flybys are consistent with a high temperature (~1-2 x 104 K) source of atomic Ca concentrated over the dawn hemisphere. Such a high temperature resutls from dissociation of CaO in a near

  16. A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere

    Directory of Open Access Journals (Sweden)

    T. J. Stubbs

    2004-03-01

    Full Text Available We study here the injection and transport of ions in the convection-dominated region of the Earth's magnetosphere. The total ion counts from the CAMMICE MICS instrument aboard the POLAR spacecraft are used to generate occurrence probability distributions of magnetospheric ion populations. MICS ion spectra are characterised by both the peak in the differential energy flux, and the average energy of ions striking the detector. The former permits a comparison with the Stubbs et al. (2001 survey of He2+ ions of solar wind origin within the magnetosphere. The latter can address the occurrences of various classifications of precipitating particle fluxes observed in the topside ionosphere by DMSP satellites (Newell and Meng, 1992. The peak energy occurrences are consistent with our earlier work, including the dawn-dusk asymmetry with enhanced occurrences on the dawn flank at low energies, switching to the dusk flank at higher energies. The differences in the ion energies observed in these two studies can be explained by drift orbit effects and acceleration processes at the magnetopause, and in the tail current sheet. Near noon at average ion energies of ≈1keV, the cusp and open LLBL occur further poleward here than in the Newell and Meng survey, probably due to convection- related time-of-flight effects. An important new result is that the pre-noon bias previously observed in the LLBL is most likely due to the component of this population on closed field lines, formed largely by low energy ions drifting earthward from the tail. There is no evidence here of mass and momentum transfer from the solar wind to the LLBL by non-reconnection coupling. At higher energies ≈2–20keV, we observe ions mapping to the auroral oval and can distinguish between the boundary and central plasma sheets. We show that ions at these energies relate to a transition from dawnward to duskward dominated flow, this is evidence of how ion drift orbits in the

  17. An auroral westward flow channel (AWFC and its relationship to field-aligned current, ring current, and plasmapause location determined using multiple spacecraft observations

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    M. L. Parkinson

    2007-02-01

    Full Text Available An auroral westward flow channel (AWFC is a latitudinally narrow channel of unstable F-region plasma with intense westward drift in the dusk-to-midnight sector ionosphere. AWFCs tend to overlap the equatorward edge of the auroral oval, and their life cycle is often synchronised to that of substorms: they commence close to substorm expansion phase onset, intensify during the expansion phase, and then decay during the recovery phase. Here we define for the first time the relationship between an AWFC, large-scale field-aligned current (FAC, the ring current, and plasmapause location. The Tasman International Geospace Environment Radar (TIGER, a Southern Hemisphere HF SuperDARN radar, observed a jet-like AWFC during ~08:35 to 13:28 UT on 7 April 2001. The initiation of the AWFC was preceded by a band of equatorward expanding ionospheric scatter (BEES which conveyed an intense poleward electric field through the inner plasma sheet. Unlike previous AWFCs, this event was not associated with a distinct substorm surge; rather it occurred during an interval of persistent, moderate magnetic activity characterised by AL~−200 nT. The four Cluster spacecraft had perigees within the dusk sector plasmasphere, and their trajectories were magnetically conjugate to the radar observations. The Waves of High frequency and Sounder for Probing Electron density by Relaxation (WHISPER instruments on board Cluster were used to identify the plasmapause location. The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE EUV experiment also provided global-scale observations of the plasmapause. The Cluster fluxgate magnetometers (FGM provided successive measurements specifying the relative location of the ring current and filamentary plasma sheet current. An analysis of Iridium spacecraft magnetometer measurements provided estimates of large-scale ionospheric FAC in relation to the AWFC evolution. Peak flows in the AWFC were located close to the peak of a Region 2

  18. The diel vertical migration patterns and individual swimming behavior of overwintering sprat Sprattus sprattus

    KAUST Repository

    Solberg, Ingrid

    2016-11-27

    We addressed the behavioral patterns and DVM dynamics of sprat overwintering in a 150 m Norwegian fjord with increasing hypoxia by depth. An upward-facing echosounder deployed at the bottom and cabled to shore provided 4 months of continuous acoustic data. This enabled detailed studies of individual behavior, specifically allowing assessment of individual vertical migrations at dusk and dawn in relation to light, analysis of so-called rise-and-sink swimming, and investigation of the sprat’ swimming activity and behavior in severely hypoxic waters. Field campaigns supplemented the acoustic studies. The acoustic records showed that the main habitat for sprat was the upper ∼ 65 m where oxygen concentrations were ⩾ 0.7 mL O2 L-1. The sprat schooled at ∼ 50 m during daytime and initiated an upward migration about 1 hour prior to sunset. While some sprat migrated to surface waters, other individuals interrupted the ascent when at ∼20-30 m, and returned to deeper waters ∼ 20-50 min after sunset. Sprat at depth was on average larger, yet individuals made excursions to- and from upper layers. Sprat were swimming in a “rise and sink” pattern at depth, likely related to negative buoyancy. Short-term dives into waters with less than 0.45 mL O2 L-1 were interpreted as feeding forays for abundant overwintering Calanus spp. The deep group of sprat initiated a dawn ascent less than 1 hour before sunrise, ending at 20-30 m where they formed schools. They subsequently returned to deeper waters about ∼20 min prior to sunrise. Measurements of surface light intensities indicated that the sprat experienced lower light levels in upper waters at dawn than at dusk. The vertical swimming speed varied significantly between the behavioral tasks. The mixed DVM patterns and dynamic nocturnal behavior of sprat persisted throughout winter, likely shaped by individual strategies involving optimized feeding and predator avoidance, as well as relating to temperature, hypoxia and

  19. A statistical analysis of the location and width of Saturn's southern auroras

    Directory of Open Access Journals (Sweden)

    S. V. Badman

    2006-12-01

    Full Text Available A selection of twenty-two Hubble Space Telescope images of Saturn's ultraviolet auroras obtained during 1997–2004 has been analysed to determine the median location and width of the auroral oval, and their variability. Limitations of coverage restrict the analysis to the southern hemisphere, and to local times from the post-midnight sector to just past dusk, via dawn and noon. It is found that the overall median location of the poleward and equatorward boundaries of the oval with respect to the southern pole are at ~14° and ~16° co-latitude, respectively, with a median latitudinal width of ~2°. These median values vary only modestly with local time around the oval, though the poleward boundary moves closer to the pole near noon (~12.5° such that the oval is wider in that sector (median width ~3.5° than it is at both dawn and dusk (~1.5°. It is also shown that the position of the auroral boundaries at Saturn are extremely variable, the poleward boundary being located between 2° and 20° co-latitude, and the equatorward boundary between 6° and 23°, this variability contrasting sharply with the essentially fixed location of the main oval at Jupiter. Comparison with Voyager plasma angular velocity data mapped magnetically from the equatorial magnetosphere into the southern ionosphere indicates that the dayside aurora lie poleward of the main upward-directed field-aligned current region associated with corotation enforcement, which maps to ~20°–24° co-latitude, while agreeing reasonably with the position of the open-closed field line boundary based on estimates of the open flux in Saturn's tail, located between ~11° and ~15°. In this case, the variability in location can be understood in terms of changes in the open flux present in the system, the changes implied by the Saturn data then matching those observed at Earth as fractions of the total planetary flux. We infer that the broad (few degrees diffuse auroral emissions

  20. A Double-Disruption Substorm Model - The Growth Phase

    Science.gov (United States)

    Sofko, G. J.; McWilliams, K. A.; Hussey, G. C.

    2014-12-01

    When the IMF turns from Bz- to Bz+, dayside merging forms open lobe field lines at low latitudes. These lobe lines are populated with shocked solar wind and dayside magnetospheric plasma from the reconnection inflow. As those lobe flux tubes pass tailward over the polar caps, they are also populated with outflow from the north and south polar cap ionospheres. As the lobe lines move tailward, they acquire a convex curvature that blocks the westward-flowing cross-tail current (XTJ). This constitutes the first stage of XTJ disruption, and it begins less than 10 min after the frontside merging.The disrupted XTJ closes dawn-to-dusk in the transition plasmasheet (TPS), where it produces a downward FAC to the ionosphere. This causes the proton arc, which is seen for the period from about 10 - 80 min after frontside merging begins at time t=0. The lobe lines eventually reconnect well downtail at about t=30 minutes. The middle section that closes the lobe lines has concave curvature and is called the Neutral Sheet (NSh). The resulting stretched field lines thus have a central NSh which separates the two convex-curvature regions to the north and south, regions which are called the Disruption Zones (DZs); the overall combination of the NDZ, NSh and SDZ is called the Stretched Plasmasheet (SPS). As the SPS continues to grow and the stretched lines are pulled earthward to relieve the magnetic tension, the filling of the NSh occurs both from the DTNL with the higher energy magnetospheric particle population on the lobe lines, but eventually also at about 25 earth radii when the polar cap ionospheric outflow (PCO) component finally reaches the NSh. A NSh FAC system forms, from which electrons flow down to the auroral ionosphere to create the pre-onset arc, starting at about t=65 min. At the same time, the Lyons-Speiser mechanism is initiated in the inner NSh, causing the PCO ions to become trapped and accelerated in the inner NSh region. Eventually, when the SPS grows earthward

  1. The ion experiment onboard the Interball-Aurora satellite; initial results on velocity-dispersed structures in the cleft and inside the auroral oval

    Directory of Open Access Journals (Sweden)

    J. A. Sauvaud

    Full Text Available The Toulouse ION experiment flown on the Russian Interball-Aurora mission performs simultaneous ion and electron measurements. Two mass spectrometers looking in opposing directions perpendicular to the satellite spin axis, which points toward the sun, measure ions in the mass and energy ranges 1–32 amu and ~0–14 000 eV. Two electron spectrometers also looking in opposing directions perform measurements in the energy range ~10 eV–20 000 eV. The Interball-Aurora spacecraft was launched on 29 August 1996 into a 62.8° inclination orbit with an apogee of ~3 RE. The satellite orbital period is 6 h, so that every four orbits the satellite sweeps about the same region of the auroral zone; the orbit plane drifts around the pole in ~9 months. We present a description of the ION experiment and discuss initial measurements performed in the cusp near noon, in the polar cleft at dusk, and inside the proton aurora at dawn. Ion-dispersed energy structures resulting from time-of-flight effects are observed both in the polar cleft at ~16 hours MLT and in the dawnside proton aurora close to 06 hours MLT. Magnetosheath plasma injections in the polar cleft, which appear as overlapping energy bands in particle energy-time spectrograms, are traced backwards in time using a particle trajectory model using 3D electric and magnetic field models. We found that the cleft ion source is located at distances of the order of 18 RE from the earth at about 19 MLT, i.e., on the flank of the magnetopause. These observations are in agreement with flux transfer events (FTE occurring not only on the front part of the magnetopause but also in a region extending at least to dusk. We also show that, during quiet magnetic conditions, time-of-flight ion dispersions can also be measured inside the dawn proton aurora. A method similar to that used for the cleft is applied to these auroral energy dispersion signatures. Unexpectedly, the ion source is found to be

  2. ULF Waves and Diffusive Radial Transport of Charged Particles

    Science.gov (United States)

    Ali, Ashar Fawad

    field data from the Radiation Belt Storm Probes (RBSP) to compute the electric and the magnetic component of the radial diffusion coefficient using the Fei et al. [2006] formulation. We conclude that contrary to prior notions, the electric component is dominant in driving radial diffusion of charged particles in the Earth's inner magnetosphere instead of the magnetic component. The electric component can be up to two orders of magnitude larger than the magnetic component. In addition, we see that ULF wave power in both the electric and the magnetic fields has a clear dependence on Kp with wave power decreasing as radial distance decreases. For both fields, the noon sectors generally contain more ULF wave power than the dawn, dusk, and the midnight magnetic local time (MLT) sectors. There is no significant difference between ULF wave power in the dawn, dusk, and the midnight sectors.

  3. Lithospheric analysis of satellite geopotential anomalies of East Asia

    Science.gov (United States)

    Tan, Li

    Satellite gravity and magnetic anomalies are used to study the lithosphere of East Asia. Free-air gravity anomalies are decomposed into terrain-correlated, mantle/core and intracrustal components by spectral correlation analysis of the free-air gravity anomalies and terrain gravity effects. Compensated terrain gravity anomalies are obtained by removing the terrain-correlated free-air gravity anomalies. They are used to estimate the Moho undulation and crustal thickness by Gauss-Legendre quadrature (GLQ) inversion techniques assuming a Airy-Heiskanen model of crustal compensation. These results are used to develop enhanced reduction procedures to generate an improved Magsat magnetic anomaly map for East Asia. A degree 12 core field is removed from the data that are updated for the crustal components in the core field differences between degree 14 and 12. These components are estimated by using spectral correlation analysis to compare the Magsat anomalies to the magnetic effect of the crust that is available from the first vertical derivative of the terrain-correlated free-air gravity anomalies via Poisson's theorem. External field effects are separated using pass-by-pass correlation analysis of the dusk and dawn data sets and their spectral reconstruction. Coherent components in the dusk and dawn maps are combined to estimate the magnetic anomalies of the lithosphere. Long wavelength magnetic features related to lower crustal thickness variations are converted into effective magnetization contrasts by a new GLQ inversion technique. Effective magnetization contrasts of the lower crust range over ±4 A/m in accordance petrological studies. Finally, a new GLQ integration formula for triangular wedge sources is derived for modeling of satellite-altitude geopotential field anomalies from arbitrarily shaped sources. Detailed magnetization and density contrasts for central India, the Tibetan Plateau, and the Bengal Gulf region are modeled by this new formula. Positive

  4. Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

    Directory of Open Access Journals (Sweden)

    U. Villante

    2004-06-01

    Full Text Available We examined geomagnetic field observations at low and middle latitudes in the Northern Hemisphere during a 50-min interval (12 May 1999, characterized by a complex behaviour of the solar wind dynamic pressure. For the entire interval, the aspects of the geomagnetic response can be organized into four groups of events which show common characteristics for the H and D components, respectively. The correspondence between the magnetospheric field and the ground components reveals different aspects of the geomagnetic response in different magnetic local time (MLT sectors. For the H component, the correspondence is highly significant in the dusk and night sectors; in the dawn and prenoon sectors it shows a dramatic change across a separation line that extends approximately between (6 MLT, 35° and (13 MLT, 60°. For the D component, the correspondence has significant values in the dawn and prenoon regions. We propose a new approach to the experimental data analysis which reveals that, at each station, the magnetospheric field has a close correspondence with the geomagnetic field projection along an axis (M1 that progressively rotates from north/south (night events to east/west orientation (dawn events. When projected along M1, the geomagnetic signals can be interpreted in terms of a one-dimensional pattern that mostly reflects the field behaviour observed at geostationary orbit. Several features appear more evident in this perspective, and the global geomagnetic response to the SW pressure variations appears much clearer than in other representations. In particular, the MLT dependence of the geomagnetic response is much smaller than that one estimated by previous investigations. A clear latitudinal dependence emerges in the dusk sector. The occurrence of low frequency waves at ~2.8mHz can be interpreted in terms of global magnetospheric modes driven by the SW pulse. This event occurred in the recovery phase after the day

  5. Seasonal-longitudinal variability of equatorial plasma bubbles

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    W. J. Burke

    2004-09-01

    Full Text Available We compare seasonal and longitudinal distributions of more than 8300 equatorial plasma bubbles (EPBs observed during a full solar cycle from 1989-2000 with predictions of two simple models. Both models are based on considerations of parameters that influence the linear growth rate, γRT, of the generalized Rayleigh-Taylor instability in the context of finite windows of opportunity available during the prereversal enhancement near sunset. These parameters are the strength of the equatorial magnetic field, Beq, and the angle, α, it makes with the dusk terminator line. The independence of α and Beq from the solar cycle phase justifies our comparisons.

    We have sorted data acquired during more than 75000 equatorial evening-sector passes of polar-orbiting Defense Meteorological Satellite Program (DMSP satellites into 24 longitude and 12 one-month bins, each containing ~250 samples. We show that: (1 in 44 out of 48 month-longitude bins EPB rates are largest within 30 days of when α=0°; (2 unpredicted phase shifts and asymmetries appear in occurrence rates at the two times per year when α≈0°; (3 While EPB occurrence rates vary inversely with Beq, the relationships are very different in regions where Beq is increasing and decreasing with longitude. Results (2 and (3 indicate that systematic forces not considered by the two models can become important. Damping by interhemispheric winds appears to be responsible for phase shifts in maximum rates of EPB occurrence from days when α=0°. Low EPB occurrence rates found at eastern Pacific longitudes suggest that radiation belt electrons in the drift loss cone reduce γRT by enhancing E-layer Pedersen conductances. Finally, we analyze an EPB event observed during a magnetic storm at a time and place where α≈-27°, to illustrate how electric-field penetration from

  6. Daily Activity and Nest Occupation Patterns of Fox Squirrels (Sciurus niger throughout the Year.

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    Thomas Wassmer

    Full Text Available The authors investigated the general activity and nest occupation patterns of fox squirrels in a natural setting using temperature-sensitive data loggers that measure activity as changes in the microenvironment of the animal. Data were obtained from 25 distinct preparations, upon 14 unique squirrels, totaling 1385 recording days. The animals were clearly diurnal, with a predominantly unimodal activity pattern, although individual squirrels occasionally exhibited bimodal patterns, particularly in the spring and summer. Even during the short days of winter (9 hours of light, the squirrels typically left the nest after dawn and returned before dusk, spending only about 7 hours out of the nest each day. Although the duration of the daily active phase did not change with the seasons, the squirrels exited the nest earlier in the day when the days became longer in the summer and exited the nest later in the day when the days became shorter in the winter, thus tracking dawn along the seasons. During the few hours spent outside the nest each day, fox squirrels seemed to spend most of the time sitting or lying. These findings suggest that fox squirrels may have adopted a slow life history strategy that involves long periods of rest on trees and short periods of ground activity each day.

  7. The Effect of Seasonal Variation and Angle of Inclination on the Performances of Photovoltaic Panels in South Eastern Nigeria

    Directory of Open Access Journals (Sweden)

    N.V. Ogueke

    2013-01-01

    Full Text Available The effects of seasonal variation and angle of inclination on the performances of photovoltaic panels in south eastern Nigeria are presented. Three photovoltaic panels, each with a rated capacity of 60 W, were used for the study in each of the locations considered. Three installation positions considered are: horizontal, an angle equal to the local latitude of location and an angle 5º greater than the local latitude of location. Power output from these panels was measured at fixed time interval from dawn to dusk for 12 months. Results obtained show an average performance of 25-30 W representing about 42-50% of the panels rated capacity. Furthermore, the horizontally installed panels, on the average, presented better performance than the others angles. Thus utilization of photovoltaic panels for power generation in the region considered should be limited to lighting applications and applications within the same power requirement range. Also for overall best performance, they should be installed in a horizontal position.

  8. Stormtime dynamics of the global thermosphere and equatorial ionosphere

    Directory of Open Access Journals (Sweden)

    W. J. Burke

    2009-05-01

    Full Text Available During magnetic storms the development of equatorial plasma bubbles (EPBs and distributions of thermospheric densities are strongly influenced by the histories of imposed magnetospheric electric (εM fields. Periods of intense EPB activity driven by penetration εM fields in the main phase are followed by their worldwide absence during recovery. A new method is applied to estimate global thermospheric energy (Eth budgets from orbit-averaged densities measured by accelerometers on polar-orbiting satellites. During the main phase of storms Eth increases as long as the stormtime εM operates, then exponentially decays toward quiet-time values during early recovery. Some fraction of the energy deposited at high magnetic latitudes during the main phase propagates into the subauroral ionosphere-thermosphere where it affects chemical and azimuthal-wind dynamics well into recovery. We suggest a scenario wherein fossils of main phase activity inhibit full restoration of quiet-time dayside dynamos and pre-reversal enhancements of upward plasma drifts near dusk denying bottomside irregularities sufficient time to grow into EPBs.

  9. Post-fire phenological behavior and breeding biology of the Spiranthera odoratissima A. St.-Hil. (Rutaceae

    Directory of Open Access Journals (Sweden)

    Mirley Luciene dos Santos

    2008-03-01

    Full Text Available The phenological behavior of species in response to cerrado stricken by fire is little known. A phenological and reproductive biological study of Spiranthera odoratissima was carried out in an anthropized area of cerrado sensu stricto affected by fire in Goiânia County, Goiás, Brazil. Phenolocial observations indicated that the individuals bloomed in synchrony three months after the fire. The phenological rhythms were associated with the seasonal pluviometric effects, a characteristic pattern of shrublet species of the cerrado. Theflowers are white with a sweet odor and are grouped in panicle inflorescences. The blossoming occurs during dusk and begins at around 16h. It offers pollen and nectar to its visitors. The species produces 32.8μl (± 3.4 of nectar with an average concentration of 16.4% (± 0.43 in equivalents of sucrose. The pollination system (phalenophily was proposed based on an analysis of the fl ower’s characteristics. Observed visitors were bees (Apis mellifera Linnaeus, flies, wasps, ants and beetles, but due to the inflorescence behavior, they were considered to be merely resource thieves. It was observed that Trigona spinipes Fabr. can act as a secondary pollinator during the pilling of pollen. The results of manual pollination and the incompatibility index (ISI indicate that the species is xenogamous and self-compatible.

  10. A simulation study of the thermosphere mass density response to substorms using GITM

    Science.gov (United States)

    Liu, Xianjing; Ridley, Aaron

    2015-09-01

    The temporal and spatial variations of the thermospheric mass density during a series of idealized substorms were investigated using the Global Ionosphere Thermosphere Model (GITM). The maximum mass density perturbation of an idealized substorm with a peak variation of hemispheric power (HP) of 50 GW and interplanetary magnetic field (IMF) Bz of -2 nT was ~14% about 50 min after the substorm onset in the nightside sector of the auroral zone. The mass density response to different types of energy input has a strong local time dependence, with the mass density perturbation due to only an IMF Bz variation peaking in the dusk sector and the density perturbation due to only HP variation peaks in the nightside sector. Simulations with IMF Bz changes only and HP changes only showed that the system behaves slightly nonlinearly when both IMF and HP variations are included (a maximum of 6% of the nonlinearity) and that the nonlinearity grows with energy input. The neutral gas heating rate due to Joule heating was of same magnitude as the heating rate due to precipitation, but the majority of the temperature enhancement due to the heating due to precipitation occurs at lower altitude as compared to the auroral heating. About 110 min after onset, a negative mass density perturbation (~-5%) occurred in the night sector, which was consistent with the mass density measurement of the CHAMP satellite.

  11. Anthropophilic biting behaviour of Anopheles (Kerteszia neivai Howard, Dyar & Knab associated with Fishermen’s activities in a malaria-endemic area in the Colombian Pacific

    Directory of Open Access Journals (Sweden)

    Jesus Eduardo Escovar

    2013-12-01

    Full Text Available On the southwest Pacific Coast of Colombia, a field study was initiated to determine the human-vector association between Anopheles (Kerteszia neivai and fishermen, including their nearby houses. Mosquitoes were collected over 24-h periods from mangrove swamps, marshlands and fishing vessels in three locations, as well as in and around the houses of fishermen. A total of 6,382 mosquitoes were collected. An. neivai was most abundant in mangroves and fishing canoes (90.8%, while Anopheles albimanus was found indoors (82% and outdoors (73%. One An. neivai and one An. albimanus collected during fishing activities in canoes were positive for Plasmodium vivax , whereas one female An. neivai collected in a mangrove was positive for P. vivax . In the mangroves and fishing canoes, An. neivai demonstrated biting activity throughout the day, peaking between 06:00 pm-07:00 pm and there were two minor peaks at dusk and dawn. These peaks coincided with fishing activities in the marshlands and mangroves, a situation that places the fishermen at risk of contracting malaria when they are performing their daily activities. It is recommended that protective measures be implemented to reduce the risk that fishermen will contract malaria.

  12. Modeling of the quasi-steady magnetotail

    Energy Technology Data Exchange (ETDEWEB)

    Birn, J. (Los Alamos National Lab., NM (USA)); Schindler, K. (Ruhr-Univ., Bochum (Germany, F.R.))

    1989-01-01

    The three-dimensional theory of the quiet magnetotail is reviewed and updated. The most advanced formulation of the theory allows one to solve the magnetohydrodynamic (MHD) equations including field-aligned flow by reduction to a set of ordinary differential equations and an ordinary integral. These solutions represent lowest order solutions of an asymptotic expansion of the MHD equations for small electric field and weak time dependence. Applications to the magnetotail configuration are presented, which include the following properties in a self-consistent way: Flaring of the tail in y and z, associated with the presence of B{sub y} and B{sub z}; variation of plasma sheet and current sheet thickness with x and y, associated with variations of B{sub z}; field-aligned currents at the boundary between plasma sheet and lobes with the signature of region 1'' currents, i.e., toward the Earth on the dawn side and away on the dusk side, associated with the decrease of the tail flaring with distance from the Earth; net cross-tail magnetic field. Particular steady models with field-aligned flow demonstrate the important role of the flow in allowing or producing configurations with a transition from a thick closed plasma sheet to a much thinner distant open current sheet and for the possibility of thick plasmoids propagating in near equilibrium through the thin distant current sheet.

  13. Neutral sheet crossings in the distant magnetotail

    Energy Technology Data Exchange (ETDEWEB)

    Heikkila, W.J.; Slavin, J.A.; Smith, E.J.; Baker, D.N.; Zwickl, R.D.

    1985-01-01

    We have analyzed the magnetic field data from ISEE-3 in the distant magnetotail for 18 crossings of the cross-tail current sheet (or so-called natural sheet) to determine the direction of the normal component B/sub z/. The crossings occurred near the middle of the aberrated magnetotail (0 < y < 30 R/sub e, -10 < z < 5) in GSM coordinates, at a distance of about 220 R/sub e/, January 28 to February 12, 1983; in each case the plasma flow velocity was tailward. In 2 cases we found B/sub z/ negative (southward), as would be required with a magnetic neutral line (reconnection line) earthward of the spacecraft. In 12 cases B/sub z/ was clearly northward (B/sub z/ > 0.4 nT), consistent with closed field lines connected to the earth. In 3 cases B/sub z/ was very close to zero; in several instances there was structure in B/sub y/, suggesting localized currents with x or z directions. One may have been a magnetopause crossing. The strong preponderance of northward B/sub z/ favors a model of the magnetotail which is dominated by boundary layer plasma, flowing tailward on closed magnetic field lines, which requires the existence of an electric field in the sense from dusk to dawn. 37 refs., 15 figs., 1 tab.

  14. Quantification of overnight movement of birch (Betula pendula branches and foliage with short interval terrestrial laser scanning

    Directory of Open Access Journals (Sweden)

    Eetu ePuttonen

    2016-02-01

    Full Text Available The goal of the study was to determine circadian movements of silver birch (Petula Bendula branches and foliage detected with terrestrial laser scanning (TLS. The study consisted of two geographically separate experiments conducted in Finland and in Austria. Both experiments were carried out at the same time of the year and under similar outdoor conditions. Experiments consisted of 14 (Finland and 77 (Austria individual laser scans taken between sunset and sunrise. The resulting point clouds were used in creating a time series of branch movements. In the Finnish data, the vertical movement of the whole tree crown was monitored due to low volumetric point density. In the Austrian data, movements of manually selected representative points on branches were monitored. The movements were monitored from dusk until morning hours in order to avoid daytime wind effects. The results indicated that height deciles of the Finnish birch crown had vertical movements between -10.0 and 5.0 cm compared to the situation at sunset. In the Austrian data, the maximum detected representative point movement was 10.0 cm. The temporal development of the movements followed a highly similar pattern in both experiments, with the maximum movements occurring about an hour and a half before (Austria or around (Finland sunrise. The results demonstrate the potential of terrestrial laser scanning measurements in support of chronobiology.

  15. The mouse liver displays daily rhythms in the metabolism of phospholipids and in the activity of lipid synthesizing enzymes.

    Science.gov (United States)

    Gorné, Lucas D; Acosta-Rodríguez, Victoria A; Pasquaré, Susana J; Salvador, Gabriela A; Giusto, Norma M; Guido, Mario Eduardo

    2015-02-01

    The circadian system involves central and peripheral oscillators regulating temporally biochemical processes including lipid metabolism; their disruption leads to severe metabolic diseases (obesity, diabetes, etc). Here, we investigated the temporal regulation of glycerophospholipid (GPL) synthesis in mouse liver, a well-known peripheral oscillator. Mice were synchronized to a 12:12 h light-dark (LD) cycle and then released to constant darkness with food ad libitum. Livers collected at different times exhibited a daily rhythmicity in some individual GPL content with highest levels during the subjective day. The activity of GPL-synthesizing/remodeling enzymes: phosphatidate phosphohydrolase 1 (PAP-1/lipin) and lysophospholipid acyltransferases (LPLATs) also displayed significant variations, with higher levels during the subjective day and at dusk. We evaluated the temporal regulation of expression and activity of phosphatidylcholine (PC) synthesizing enzymes. PC is mainly synthesized through the Kennedy pathway with Choline Kinase (ChoK) as a key regulatory enzyme or through the phosphatidylethanolamine (PE) N-methyltransferase (PEMT) pathway. The PC/PE content ratio exhibited a daily variation with lowest levels at night, while ChoKα and PEMT mRNA expression displayed maximal levels at nocturnal phases. Our results demonstrate that mouse liver GPL metabolism oscillates rhythmically with a precise temporal control in the expression and/or activity of specific enzymes.

  16. Artificial ionospheric modification: The Metal Oxide Space Cloud experiment

    Science.gov (United States)

    Caton, Ronald G.; Pedersen, Todd R.; Groves, Keith M.; Hines, Jack; Cannon, Paul S.; Jackson-Booth, Natasha; Parris, Richard T.; Holmes, Jeffrey M.; Su, Yi-Jiun; Mishin, Evgeny V.; Roddy, Patrick A.; Viggiano, Albert A.; Shuman, Nicholas S.; Ard, Shaun G.; Bernhardt, Paul A.; Siefring, Carl L.; Retterer, John; Kudeki, Erhan; Reyes, Pablo M.

    2017-05-01

    Clouds of vaporized samarium (Sm) were released during sounding rocket flights from the Reagan Test Site, Kwajalein Atoll in May 2013 as part of the Metal Oxide Space Cloud (MOSC) experiment. A network of ground-based sensors observed the resulting clouds from five locations in the Republic of the Marshall Islands. Of primary interest was an examination of the extent to which a tailored radio frequency (RF) propagation environment could be generated through artificial ionospheric modification. The MOSC experiment consisted of launches near dusk on two separate evenings each releasing 6 kg of Sm vapor at altitudes near 170 km and 180 km. Localized plasma clouds were generated through a combination of photoionization and chemi-ionization (Sm + O → SmO+ + e-) processes producing signatures visible in optical sensors, incoherent scatter radar, and in high-frequency (HF) diagnostics. Here we present an overview of the experiment payloads, document the flight characteristics, and describe the experimental measurements conducted throughout the 2 week launch window. Multi-instrument analysis including incoherent scatter observations, HF soundings, RF beacon measurements, and optical data provided the opportunity for a comprehensive characterization of the physical, spectral, and plasma density composition of the artificial plasma clouds as a function of space and time. A series of companion papers submitted along with this experimental overview provide more detail on the individual elements for interested readers.

  17. AIS reception from a CubeSat in LEO

    DEFF Research Database (Denmark)

    Larsen, Jesper Abildgaard; Mortensen, Hans Peter; Nielsen, Jens Frederik Dalsgaard

    2013-01-01

    The primary payloads on board the AAUSAT3 satellite are two different AIS receivers, one is a traditional hardware-based receiver, the other one is a software-defined radio receiver. The hardware-based receiver has been developed around an ADF-7020 transceiver, with an appropriate LNA in front...... into a low-Earth orbit with a semi-major axis of 7156 km, i.e. 800 km altitude, near circular, dusk-dawn Sun-synchronous orbit. From this orbit the AIS antenna system, which consists of a dipole antenna, has a foot print diameter of approximately 6000 km. During the first pass over the primary ground station...... at Aalborg University, basic telemetry and the first few AIS messages were downloaded. During the first 14 days of the mission, the two receivers managed to detect more than 100,000 different AIS messages from ships all around the world, and more than 35,000 of these messages have been successfully...

  18. An Inquiry into the 28 Lodges (xiu) in Daybooks (Ri Shu) on Bamboo Slips of the Chu and Qin States%楚、秦简《日书》中的二十八宿问题探讨

    Institute of Scientific and Technical Information of China (English)

    钟守华

    2009-01-01

    楚、秦简中关于二十八宿的新史料,对考释二十八宿在战国至秦代的演变有着重要价值.重点探讨了其中的二十八宿古距度、旦昏中星、日在星宿、四象分度不均匀、二十八宿数与二十八宿星占等问题.%The new historical materials concerning the 28 lodges found in Daybooks (Ri Shu) written on bamboo slips of the Chu and Qin states play an important role in investigations into the e-volution of these lodges in China from the Warring States Period to the Qin dynasty. This paper lays stress on the material in these sources relating to the so-called 'old' angular widths of the 28 lodges, dusk and dawn culminating stars, the stellar lodges in which the sun was located, the inequality of the divisions of the sky linked to the four emblematic animals, the number of the 28 lodges and stellar divination based on the 28 lodges.

  19. Global reconnection topology as inferred from plasma observations inside Kelvin-Helmholtz vortices

    Directory of Open Access Journals (Sweden)

    M. B. Bavassano Cattaneo

    2010-04-01

    Full Text Available During a long lasting period of northward interplanetary magnetic field and high solar wind speed (above 700 km/s, the Cluster spacecraft go across a number of very large rolled-up Kelvin-Helmholtz (KH vortices at the dusk magnetopause, close to the terminator. The peculiarity of the present event is a particular sequence of ions and electrons distribution functions observed repeatedly inside each vortex. In particular, whenever Cluster crosses the current layer inside the vortices, multiple field-aligned ion populations appear, suggesting the occurrence of reconnection. In addition, the ion data display a clear velocity filter effect both at the leading and at the trailing edge of each vortex. This effect is not present in the simultaneous electron data. Unlike other KH studies reported in the literature in which reconnection occurs within the vortices, in the present event the observations are not compatible with local reconnection, but are accounted for by lobe reconnection occurring along an extended X-line at the terminator in the Southern Hemisphere. The reconnected field lines "sink" across the magnetopause and then convect tailward-duskward where they become embedded in the vortices. Another observational evidence is the detected presence of solar wind plasma on the magnetospheric side of the vortices, which confirms unambiguously the occurrence of mass transport across the magnetopause already reported in the literature. The proposed reconnection scenario accounts for all the observational aspects, regarding both the transport process and the kinetic signatures.

  20. A comparison of radio data and model calculations of Jupiter's synchrotron radition 2. East-west asymmetry in the radiation belts as a functon of Jovian longitude

    Science.gov (United States)

    de Pater, Imke

    1981-05-01

    On the basis of comparison of radio data and model calculations of Jupiter's synchrotron radiaton the 'hot region' or east-west asymmetry in the planet's radiation belts is proposed to be due to the combined effect of an overabundance of electrons at jovicentric longitudes λJ~240°-360° and the existence of a dusk dawn directed electric field over the inner magnetosphere, generated by the wind system in the upper atmosphere. The model calculations were based upon the magnetic field configurations derived from the Pioneer data by Acuna and Ness [1976] (the O4 model) and Davis, Jones and Smith (quoted in Smith and Gulkis [1979]) (the P11 (3,2)A model), with an electron distribution derived in the first paper of this series [de Pater, this issue]. We would infer from the calculations that the O4 model gives a slightly better fit to the data; the relatively large number density at λJ~240°-360°, however, might indicate the presence of even higher order moments in the field.

  1. Photic and pineal modulation of food anticipatory circadian activity rhythms in rodents.

    Directory of Open Access Journals (Sweden)

    Danica F Patton

    Full Text Available Restricted daily feeding schedules entrain circadian oscillators that generate food anticipatory activity (FAA rhythms in nocturnal rodents. The location of food-entrainable oscillators (FEOs necessary for FAA remains uncertain. The most common procedure for inducing circadian FAA is to limit food access to a few hours in the middle of the light period, when activity levels are normally low. Although light at night suppresses activity (negative masking in nocturnal rodents, it does not prevent the expression of daytime FAA. Nonetheless, light could reduce the duration or magnitude of FAA. If so, then neural or genetic ablations designed to identify components of the food-entrainable circadian system could alter the expression of FAA by affecting behavioral responses to light. To assess the plausibility of light as a potential mediating variable in studies of FAA mechanisms, we quantified FAA in rats and mice alternately maintained in a standard full photoperiod (12h of light/day and in a skeleton photoperiod (two 60 min light pulses simulating dawn and dusk. In both species, FAA was significantly and reversibly enhanced in the skeleton photoperiod compared to the full photoperiod. In a third experiment, FAA was found to be significantly attenuated in rats by pinealectomy, a procedure that has been reported to enhance some effects of light on behavioral circadian rhythms. These results indicate that procedures affecting behavioral responses to light can significantly alter the magnitude of food anticipatory rhythms in rodents.

  2. Diel changes in food and feeding activity of sciaenid fishes from the South-western Atlantic, Brazil.

    Science.gov (United States)

    Soares, L S; Vazzoler, A E

    2001-05-01

    Food habits and daily feeding activity of fish populations are important ecological variables for understanding their role in the ecosystem. Diel changes in feeding activity and dietary composition of juvenile whitemouth croaker Micropogonias furnieri, shortfin corvina Isopisthus parvipinnis, shorthead drum Larimus breviceps and of juvenile and adult banded croaker Paralonchurus brasiliensis were investigated from samples taken over a 24 hours period from 4 to 5 September 1987 on the continental shelf off South-eastern Brazil. Whitemouth croaker and banded croaker had a benthic diet based on polychaetes and some caridean shrimps and showed no diel feeding pattern. Shortfin corvina and shorthead drum fed on crustaceans and teleostean fish, the former species primarily on pelagic sergestid shrimps and benthic caridean shrimps, and the latter mainly on pelagic sergestid shrimps, mysidacean and benthic caridean shrimps. Shortfin corvina is primarily a diurnal feeder, but preyed on some items only at night. Shorthead drum is a night feeder, with minimum stomach fullness values between dawn and daytime, and maximum values between dusk and night time.

  3. Storm-Time Strong Field-Aligned Ion Upflow in Region of the SED Plume

    Institute of Scientific and Technical Information of China (English)

    YUAN Zhi-Gang; DENG Xiao-Hua; WANG Jing-Fang

    2008-01-01

    report the observations from the GPS TEC and DMSP F-13 satellites showing that very strong upward field-aligned (FA) ion velocity and flux in the outer region of the storm-enhanced density (SED) occurred in the event of the geomagnetic storm on 29-31 May 2003. By a method of coordinate transformation, upward FA ion velocities in excess of 250m/s are obtained from the observations of the DMSP F-13 satellite. Further, an FA ion flux is estimated to be about 4.5×1013ions/m2s in the dusk sector. The estimated FA ion velocity and flux provide a powerful direct proof to support the scenario that there is a strong coupling of particles between the ionosphere and plasmasphere in the region of the SED plume. In the process, FA ion flux transports from the ionosphere to the plasmasphere in the region of the SED plume. Therefore, the plume of SED in the ionosphere provides an important source to the enhanced density of O+ in the storm-time plasmasphere.

  4. Sunglint Detection for Unmanned and Automated Platforms

    Directory of Open Access Journals (Sweden)

    Oliver Zielinski

    2012-09-01

    Full Text Available We present an empirical quality control protocol for above-water radiometric sampling focussing on identifying sunglint situations. Using hyperspectral radiometers, measurements were taken on an automated and unmanned seaborne platform in northwest European shelf seas. In parallel, a camera system was used to capture sea surface and sky images of the investigated points. The quality control consists of meteorological flags, to mask dusk, dawn, precipitation and low light conditions, utilizing incoming solar irradiance (ES spectra. Using 629 from a total of 3,121 spectral measurements that passed the test conditions of the meteorological flagging, a new sunglint flag was developed. To predict sunglint conspicuous in the simultaneously available sea surface images a sunglint image detection algorithm was developed and implemented. Applying this algorithm, two sets of data, one with (having too much or detectable white pixels or sunglint and one without sunglint (having least visible/detectable white pixel or sunglint, were derived. To identify the most effective sunglint flagging criteria we evaluated the spectral characteristics of these two data sets using water leaving radiance (LW and remote sensing reflectance (RRS. Spectral conditions satisfying ‘mean LW (700–950 nm < 2 mW∙m−2∙nm−1∙Sr−1’ or alternatively ‘minimum RRS (700–950 nm < 0.010 Sr−1’, mask most measurements affected by sunglint, providing an efficient empirical flagging of sunglint in automated quality control.

  5. Year-round observations of carbon biomass and flux variability in the Southern Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, James K.B.; Wood, Todd

    2009-02-01

    Three Carbon Explorer (CE) floats profiling to kilometer depths in the Southern Ocean tracked dawn-dusk variations of mixing/stratification, particulate organic carbon (POC), and light scattering and sedimentation at 100, 250, and 800 m continuously from January 2002 to April 2003. Data were analyzed in conjunction with contemporaneous satellite winds and chlorophyll and derived subsurface light fields. The CE deployed at 66{sup o}S 172{sup o}W operated in the ice edge zone in absence of light. Two CEs deployed at 55{sup o}S 172{sup o}W recorded wintertime mixing to {approx}400 m, yet observed very different bloom dynamics and sedimentation the following spring. Four hypotheses are explored. The strongest is that shallow transient stratification of the deep winter mixed layer to shallower than photosynthetic critical depth occurred more frequently in the non-bloom/higher sedimentation case. The lower particle export to 800 m under the bloom was hypothesized to be due to higher interception of sinking carbon by a relatively starved over wintering zooplankton population. In the Southern Ocean surface phytoplankton biomass may counter indicate particle flux at kilometer depths.

  6. The far-ultraviolet main auroral emission at Jupiter. Pt. 2. Vertical emission profile

    Energy Technology Data Exchange (ETDEWEB)

    Bonfond, B.; Gustin, J.; Gerard, J.C.; Grodent, D.; Radioti, A. [Liege Univ. (Belgium). Lab. de Physique Atmospherique et Planetaire; Palmaerts, B. [Liege Univ. (Belgium). Lab. de Physique Atmospherique et Planetaire; Max-Planck-Institut fuer Sonnensystemforschung, Goettingen (Germany); Badman, S.V. [Lancaster Univ. (United Kingdom). Dept. of Physics; Khurana, K.K. [California Univ., Los Angeles, CA (United States); Tao, C. [Institut de Recherche en Astrophysique et Planetologie, Toulouse (France)

    2015-07-01

    The aurorae at Jupiter are made up of many different features associated with a variety of generation mechanisms. The main auroral emission, also known as the main oval, is the most prominent of them as it accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range. The energy of the precipitating electrons is a crucial parameter to characterize the processes at play which give rise to these auroral emissions, and the altitude of the emissions directly depends on this energy. Here we make use of far-UV (FUV) images acquired with the Advanced Camera for Surveys on board the Hubble Space Telescope and spectra acquired with the Space Telescope Imaging Spectrograph to measure the vertical profile of the main emissions. The altitude of the brightness peak as seen above the limb is ∝ 400 km, which is significantly higher than the 250 km measured in the post-dusk sector by Galileo in the visible domain. However, a detailed analysis of the effect of hydrocarbon absorption, including both simulations and FUV spectral observations, indicates that FUV apparent vertical profiles should be considered with caution, as these observations are not incompatible with an emission peak located at 250 km. The analysis also calls for spectral observations to be carried out with an optimized geometry in order to remove observational ambiguities.

  7. Design and testing of a novel, protective human-baited tent trap for the collection of anthropophilic disease vectors.

    Science.gov (United States)

    Krajacich, Benjamin J; Slade, Jeremiah R; Mulligan, Robert T; Labrecque, Brendan; Kobylinski, Kevin C; Gray, Meg; Kuklinski, Wojtek S; Burton, Timothy A; Seaman, Jonathan A; Sylla, Massamba; Foy, Brian D

    2014-01-01

    Currently, there exists a deficit of safe, active trapping methods for the collection of host-seeking Anopheles and other disease-causing arthropod vectors. The gold-standard approach for mosquito collection is that of human landing catch (HLC), in which an individual exposes bare skin to possibly infected vectors. Here, we present the development of a new method for mosquito collection, the Infoscitex tent, which uses modern tent materials coupled with a novel trap design. This provides an efficacious, a non-labor-intensive, and a safe method for vector collection. In these initial studies, we found it collected an average of 27.7 Anopheles gambiae s.l. per trap per night in rural villages in southeastern Senegal, and 43.8 Culex group Vper trap per night in the semiurban town of Kedougou, Senegal. In direct comparisons with HLC, the tent was not statistically different for collection of Culex quinquefasciatus in crepuscular sampling, but was significantly less efficacious at trapping the highly motile dusk-biter Aedes aegypti. These studies suggest that the Infoscitex tent is a viable and safe alternative to HLC for Anopheles and Culex sampling in areas of high vector-borne disease infection risk.

  8. 列维坦油画作品《晚钟》绘画语言浅析%Painting Language in Levitan's Evening Bell

    Institute of Scientific and Technical Information of China (English)

    陈智勇; 王惠宁

    2012-01-01

    Evening Bell is the creative painting works painted by Levitan, Russian landscape painter, in 1890s, which depicts the people waiting for crossing the river and the sweet, quiet and warm natural scenery of Russian outskirts near dusk with the style of realism. Evening Bell uses a unique artistic language skill to perform Levitan's love for the scenery and the people of his own country.%俄罗斯风景画家列维坦所创作的油画《晚钟》是19世纪90年代的作品,画中以现实主义的风格描绘了临近黄昏时静谧、温暖和恬美的俄罗斯大自然郊外的景色和要渡河的人们。《晚钟》运用独特的艺术语言技巧表现了列维坦对自己祖国风景和人民的热爱之情。

  9. Environmental influences on patterns of vertical movement and site fidelity of grey reef sharks (Carcharhinus amblyrhynchos) at aggregation sites.

    Science.gov (United States)

    Vianna, Gabriel M S; Meekan, Mark G; Meeuwig, Jessica J; Speed, Conrad W

    2013-01-01

    We used acoustic telemetry to describe the patterns of vertical movement, site fidelity and residency of grey reef sharks (Carcharhinus amblyrhynchos) on the outer slope of coral reefs in Palau, Micronesia, over a period of two years and nine months. We tagged 39 sharks (mostly adult females) of which 31 were detected regularly throughout the study. Sharks displayed strong inter-annual residency with greater attendance at monitored sites during summer than winter months. More individuals were detected during the day than at night. Mean depths of tagged sharks increased from 35 m in winter to 60 m in spring following an increase in water temperature at 60 m, with maximum mean depths attained when water temperatures at 60 m stabilised around 29°C. Sharks descended to greater depths and used a wider range of depths around the time of the full moon. There were also crepuscular cycles in mean depth, with sharks moving into shallower waters at dawn and dusk each day. We suggest that daily, lunar and seasonal cycles in vertical movement and residency are strategies for optimising both energetic budgets and foraging behaviour. Cyclical patterns of movement in response to environmental variables might affect the susceptibility of reef sharks to fishing, a consideration that should be taken into account in the implementation of conservation strategies.

  10. Dispersive flight and house invasion by Triatoma guasayana and Triatoma sordida in Argentina

    Directory of Open Access Journals (Sweden)

    Cristina Wisnivesky Colli

    1993-03-01

    Full Text Available Flight activity and invasion of houses by Triatoma sordida and T. guasayana were studied in the Province of Santiago del Estero, Argentina. Spontaneous findings of both species in houses were recorded from 1982 to 1989. Light trap collections were performed in 1982, 1983 and 1984, at the woods surrounding the settlements of Amamá (43 houses and Trinidad (19 houses. Most of the 101 triatomines collected, were unfed and negative for Trypanosoma cruzi. T. guasayana predominated over T. sordida, and both appeared on the lighted screens between 19-31 min (mean 24 after dusk and the catch time was 30-45 min. Although entomological evaluation of 41 houses at Amamá performed in September 1985, just before insecticidal spraying, showed that Triatoma infestans predominated, adults of T. guasayana were collected in sleeping places, in 7 houses (17%. Most triatomines invading houses from then up to 1990 were flying T. guasayana (20/27 and females outnumbered males. Three non infected T. guasayana females were fed on man and two T. guasayana males positive for "T. cruzi like" trypanosomes were unfed. Therefore, visiting hungry adults could transmit T. cruzi to people and introduce wild parasites to the domestic cycle. T. guasayana stands as the main potential substitute of T. infestans in the studied area, and it might play there the same role as T. sordida in Brazil.

  11. Fairweather atmospheric electricity at Antarctica during local summer as observed from Indian station, Maitri

    Indian Academy of Sciences (India)

    C Panneerselvam; C Selvaraj; K Jeeva; K U Nair; C P Anilkumar; S Gurubaran

    2007-06-01

    Surface measurements of the atmospheric electrical parameters like Maxwell current, electric field and conductivity studied at the Indian station, Maitri (70.75°S, 11.75°E, 117m above mean sea level), Antarctica, during austral summer have been analyzed for the years 2001 to 2004. A total of 69 days were selected which satisfied the ‘fairweather’ conditions, i.e., days with absence of high winds, drifting or falling snow, clouds, and fog effects. The diurnal variation curve of electric field and vertical current averaged for 69 fairweather days is a single periodic with a minimum at 03:00UT and a maximum near 19:00UT, which is very similar to the Carnegie curve. The correlation coefficient between these measured parameters has a high value (more than 0.9) for all the days. During fairweather days the measured current and field variations are similar and hence it is clear that the conductivity is more or less stable. During magnetically disturbed days, the dawn-dusk potential drop has clear influences on the diurnal variation and it modifies the conductivity. Apart from the day-to-day variation in low latitude thunderstorm activity, there are diurnal, seasonal, inter-annual variations in the electric potential and the currents, as well as solar influences on the measured parameters. This study will help us to examine the impact of solar and geophysical phenomena like solar flares, geomagnetic storms and substorms on the global electric circuit.

  12. The ELF4-ELF3-LUX complex links the circadian clock to diurnal control of hypocotyl growth.

    Science.gov (United States)

    Nusinow, Dmitri A; Helfer, Anne; Hamilton, Elizabeth E; King, Jasmine J; Imaizumi, Takato; Schultz, Thomas F; Farré, Eva M; Kay, Steve A

    2011-07-13

    The circadian clock is required for adaptive responses to daily and seasonal changes in environmental conditions. Light and the circadian clock interact to consolidate the phase of hypocotyl cell elongation to peak at dawn under diurnal cycles in Arabidopsis thaliana. Here we identify a protein complex (called the evening complex)--composed of the proteins encoded by EARLY FLOWERING 3 (ELF3), ELF4 and the transcription-factor-encoding gene LUX ARRHYTHMO (LUX; also known as PHYTOCLOCK 1)--that directly regulates plant growth. ELF3 is both necessary and sufficient to form a complex between ELF4 and LUX, and the complex is diurnally regulated, peaking at dusk. ELF3, ELF4 and LUX are required for the proper expression of the growth-promoting transcription factors encoded by PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF5 (also known as PHYTOCHROME INTERACTING FACTOR 3-LIKE 6) under diurnal conditions. LUX targets the complex to the promoters of PIF4 and PIF5 in vivo. Mutations in PIF4 and/or PIF5 are epistatic to the loss of the ELF4-ELF3-LUX complex, suggesting that regulation of PIF4 and PIF5 is a crucial function of the complex. Therefore, the evening complex underlies the molecular basis for circadian gating of hypocotyl growth in the early evening.

  13. Magnetic information calibrates celestial cues during migration.

    Science.gov (United States)

    Sandberg; Bäckman; Moore; Lõhmus

    2000-10-01

    Migratory birds use celestial and geomagnetic directional information to orient on their way between breeding and wintering areas. Cue-conflict experiments involving these two orientation cue systems have shown that directional information can be transferred from one system to the other by calibration. We designed experiments with four species of North American songbirds to: (1) examine whether these species calibrate orientation information from one system to the other; and (2) determine whether there are species-specific differences in calibration. Migratory orientation was recorded with two different techniques, cage tests and free-flight release tests, during autumn migration. Cage tests at dusk in the local geomagnetic field revealed species-specific differences: red-eyed vireo, Vireo olivaceus, and northern waterthrush, Seiurus noveboracensis, selected seasonally appropriate southerly directions whereas indigo bunting, Passerina cyanea, and grey catbird, Dumetella carolinensis, oriented towards the sunset direction. When tested in deflected magnetic fields, vireos and waterthrushes responded by shifting their orientation according to the deflection of the magnetic field, but buntings and catbirds failed to show any response to the treatment. In release tests, all four species showed that they had recalibrated their star compass on the basis of the magnetic field they had just experienced in the cage tests. Since release tests were done in the local geomagnetic field it seems clear that once the migratory direction is determined, most likely during the twilight period, the birds use their recalibrated star compass for orientation at departure. Copyright 2000 The Association for the Study of Animal Behaviour.

  14. Foraging activity and seasonal food preference of Linepithema micans (Hymenoptera: Formicidae), a species associated with the spread of Eurhizococcus brasiliensis (Hemiptera: Margarodidae).

    Science.gov (United States)

    Nondillo, Aline; Ferrari, Leonardo; Lerin, Sabrina; Bueno, Odair Correa; Bottona, Marcos

    2014-08-01

    Linepithema micans (Forel) (Hymenoptera: Formicidae) is the main ant species responsible for the spread of Eurhizococcus brasiliensis (Wille) (Hemiptera: Margarodidae), a soil scale that damages vine plants in southern Brazil. The daily foraging activity of L. micans and its seasonal preference for protein- and carbohydrate-based foods were evaluated. The study was carried out in a greenhouse using seedlings of the Paulsen 1103 rootstock (Vitis berlandieri x Vitis rupestris) planted individually in pots and infested with colonies of L. micans. To determine the daily foraging activity and seasonal preference, a cricket (Gryllus sp.) and a 70% solution of inverted sugar and water were offered once a month for 12 mo. The ants foraging on each food source were counted hourly for 24 h. L. micans foraged from dusk until the end of the next morning, with higher intensity in the spring and summer. Workers of L. micans showed changes in food preference during the year, with a predominance of protein-based food during winter and spring and carbohydrate-based food during autumn. The implications of this behavior for control of the species with the use of toxic baits are discussed.

  15. Comparison of time-restricted and ad libitum self-feeding on the growth, feeding behavior and daily digestive enzyme profiles of Atlantic salmon

    Science.gov (United States)

    Shi, Ce; Liu, Ying; Yi, Mengmeng; Zheng, Jimeng; Tian, Huiqin; Du, Yishuai; Li, Xian; Sun, Guoxiang

    2017-07-01

    Although it has been hypothesized that a predictable feeding regime in animals allows physiological variables to be adjusted to maximize nutrient utilization and, hence, better growth performance, the assumption has rarely been tested. This study compares the effects of time-restricted versus free access self-feeding on the growth, feeding behavior and daily digestive enzyme rhythms of Atlantic salmon ( Salmo salar). In an experiment that lasted 6 weeks, fish (109.9 g) were divided into two groups: group 1 had free access to a self-feeder (FA); group 2 received three meals per day (2 h per meal) at dawn, midday and dusk via a time-restricted self-feeder (TR). At the end of the experiment, the fish were sampled every 3 h over a 24-h period. The results showed that the TR fish quickly synchronized their feeding behavior to the feeding window and their blood glucose showed a significant postprandial increase, while FA fish displayed no statistically significant rhythms ( P>0.05). Pepsin activity of TR fish also showed a significant daily rhythm ( P0.05). In conclusion, the study failed to confirm a link between the entrainment of daily digestive enzyme profiles and growth performance, with the TR group showing comparatively poor blood glucose regulation.

  16. Effects of auroral potential drops on plasma sheet dynamics

    Science.gov (United States)

    Xi, Sheng; Lotko, William; Zhang, Binzheng; Wiltberger, Michael; Lyon, John

    2016-11-01

    The reaction of the magnetosphere-ionosphere system to dynamic auroral potential drops is investigated using the Lyon-Fedder-Mobarry global model including, for the first time in a global simulation, the dissipative load of field-aligned potential drops in the low-altitude boundary condition. This extra load reduces the field-aligned current (j||) supplied by nightside reconnection dynamos. The system adapts by forcing the nightside X line closer to Earth, with a corresponding reduction in current lensing (j||/B = constant) at the ionosphere and additional contraction of the plasma sheet during substorm recovery and steady magnetospheric convection. For steady and moderate solar wind driving and with constant ionospheric conductance, the cross polar cap potential and hemispheric field-aligned current are lower by approximately the ratio of the peak field-aligned potential drop to the cross polar cap potential (10-15%) when potential drops are included. Hemispheric ionospheric Joule dissipation is less by 8%, while the area-integrated, average work done on the fluid by the reconnecting magnetotail field increases by 50% within |y| < 8 RE. Effects on the nightside plasma sheet include (1) an average X line 4 RE closer to Earth; (2) a 12% higher mean reconnection rate; and (3) dawn-dusk asymmetry in reconnection with a 17% higher rate in the premidnight sector.

  17. Autoreceptor control of peptide/neurotransmitter corelease from PDF neurons determines allocation of circadian activity in drosophila.

    Science.gov (United States)

    Choi, Charles; Cao, Guan; Tanenhaus, Anne K; McCarthy, Ellena V; Jung, Misun; Schleyer, William; Shang, Yuhua; Rosbash, Michael; Yin, Jerry C P; Nitabach, Michael N

    2012-08-30

    Drosophila melanogaster flies concentrate behavioral activity around dawn and dusk. This organization of daily activity is controlled by central circadian clock neurons, including the lateral-ventral pacemaker neurons (LN(v)s) that secrete the neuropeptide PDF (pigment dispersing factor). Previous studies have demonstrated the requirement for PDF signaling to PDF receptor (PDFR)-expressing dorsal clock neurons in organizing circadian activity. Although LN(v)s also express functional PDFR, the role of these autoreceptors has remained enigmatic. Here, we show that (1) PDFR activation in LN(v)s shifts the balance of circadian activity from evening to morning, similar to behavioral responses to summer-like environmental conditions, and (2) this shift is mediated by stimulation of the Gα,s-cAMP pathway and a consequent change in PDF/neurotransmitter corelease from the LN(v)s. These results suggest another mechanism for environmental control of the allocation of circadian activity and provide new general insight into the role of neuropeptide autoreceptors in behavioral control circuits. Copyright © 2012 The Authors. Published by Elsevier Inc. All rights reserved.

  18. Autoreceptor Modulation of Peptide/Neurotransmitter Co-release from PDF Neurons Determines Allocation of Circadian Activity in Drosophila

    Science.gov (United States)

    Choi, Charles; Cao, Guan; Tanenhaus, Anne K.; McCarthy, Ellena v.; Jung, Misun; Schleyer, William; Shang, Yuhua; Rosbash, Michael; Yin, Jerry C.P.; Nitabach, Michael N.

    2012-01-01

    Drosophila melanogaster flies concentrate behavioral activity around dawn and dusk. This organization of daily activity is controlled by central circadian clock neurons, including the lateral ventral pacemaker neurons (LNvs) that secrete the neuropeptide PDF (Pigment Dispersing Factor). Previous studies have demonstrated the requirement for PDF signaling to PDF receptor (PDFR)-expressing dorsal clock neurons in organizing circadian activity. While LNvs also express functional PDFR, the role of these autoreceptors has remained enigmatic. Here we show that (1) PDFR activation in LNvs shifts the balance of circadian activity from evening to morning, similar to behavioral responses to summer-like environmental conditions and (2) this shift is mediated by stimulation of the Ga,s-cAMP pathway and a consequent change in PDF/neurotransmitter co-release from the LNvs. These results suggest a novel mechanism for environmental control of the allocation of circadian activity and provide new general insight into the role of neuropeptide autoreceptors in behavioral control circuits. PMID:22938867

  19. The chemistry of negotiation: rhythmic, glycan-driven acidification in a symbiotic conversation.

    Science.gov (United States)

    Schwartzman, Julia A; Koch, Eric; Heath-Heckman, Elizabeth A C; Zhou, Lawrence; Kremer, Natacha; McFall-Ngai, Margaret J; Ruby, Edward G

    2015-01-13

    Glycans have emerged as critical determinants of immune maturation, microbial nutrition, and host health in diverse symbioses. In this study, we asked how cyclic delivery of a single host-derived glycan contributes to the dynamic stability of the mutualism between the squid Euprymna scolopes and its specific, bioluminescent symbiont, Vibrio fischeri. V. fischeri colonizes the crypts of a host organ that is used for behavioral light production. E. scolopes synthesizes the polymeric glycan chitin in macrophage-like immune cells called hemocytes. We show here that, just before dusk, hemocytes migrate from the vasculature into the symbiotic crypts, where they lyse and release particulate chitin, a behavior that is established only in the mature symbiosis. Diel transcriptional rhythms in both partners further indicate that the chitin is provided and metabolized only at night. A V. fischeri mutant defective in chitin catabolism was able to maintain a normal symbiont population level, but only until the symbiotic organ reached maturity (∼ 4 wk after colonization); this result provided a direct link between chitin utilization and symbiont persistence. Finally, catabolism of chitin by the symbionts was also specifically required for a periodic acidification of the adult crypts each night. This acidification, which increases the level of oxygen available to the symbionts, enhances their capacity to produce bioluminescence at night. We propose that other animal hosts may similarly regulate the activities of epithelium-associated microbial communities through the strategic provision of specific nutrients, whose catabolism modulates conditions like pH or anoxia in their symbionts' habitat.

  20. Awareness of dengue and practice of dengue control among the semi-urban community: a cross sectional survey.

    Science.gov (United States)

    Naing, Cho; Ren, Wong Yih; Man, Chan Yuk; Fern, Koh Pei; Qiqi, Chua; Ning, Choo Ning; Ee, Clarice Wong Syun

    2011-12-01

    Primary prevention is the most effective measure in dengue prevention and control. The objectives were (i) to determine the level of knowledge and practice of dengue control amongst the study community, and (ii) to explore the factors affecting practice of dengue control in the study area. A cross-sectional study was conducted in a semi-urban Town of Malaysia, using a structured questionnaire covering sociodemography, knowledge related to dengue, knowledge related to Aedes mosquito and preventive measures against the disease. For comparison of survey responses, chi-square test was applied for categorical data. To explore the factors affecting the practice of dengue control, a linear regression model was introduced. Almost all of the respondents (95%) had heard about dengue. Overall, misconceptions of dengue transmission were identified and the practice of dengue control in the study population was insufficient. About half (50.5%) had misconceptions that Aedes can breed in dirty water and the preferred biting time is dusk or sunset (45.6%). Only 44.5% of the households surveyed had covered their water containers properly. Significant associations were found between knowledge scores of dengue and age (P = 0.001), education level (P = 0.001), marital status (P = 0.012), and occupation (P = 0.007). In regression analysis, only the knowledge of dengue was significantly and positively associated with practice on dengue control. A future study with larger samples and more variables to assess the knowledge, attitudes and practices of dengue control is recommended.

  1. CAST explores the dark side of the Universe

    CERN Multimedia

    Corinne Pralavorio

    2015-01-01

    Following the search for axions, candidates for dark matter, CAST is widening its scientific horizon by searching for chameleons, hypothetical particles postulated as an explanation for dark energy.     CAST, CERN's axion solar telescope, moves on its rail to follow the Sun (for an hour and a half at dawn and an hour and a half at dusk). As the summer comes to an end, surveyors have set to work in the experimental hall of CAST, CERN’s axion solar telescope. They will spend around 10 days perfecting the alignment of the detector with respect to the position of the Sun, to within a thousandth of a radian. The Sun's course is visible from the one window in the CAST experimental hall just twice a year, in March and September. This is why the physicists are making the most of these few days to align their magnet precisely. For 12 years, CAST has been tracking the movement of the Sun for an hour and a half at dawn ...

  2. Plasma flows in Saturn's nightside magnetosphere

    Science.gov (United States)

    Thomsen, M. F.; Jackman, C. M.; Tokar, R. L.; Wilson, R. J.

    2014-06-01

    The plasma properties, especially the flow parameters, obtained from numerical integration of Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer measurements during intervals when the CAPS field of view encompassed both inward and outward flow directions relative to corotation are examined for nightside data (18-06 local time) during 2006, 2009, and 2010. The results show good agreement with previously reported values derived using different selection criteria and a different analysis technique. Nightside flows are predominantly in or near the corotation direction, indicating continuing influence of connection to the ionosphere. There is no evidence for a quasi-steady reconnection x line within the surveyed region of the tail, although dynamic events attributable to transient reconnection have been observed. There is a net radial mass outflow, leading to an estimated net mass loss between 18 and 03 local time of ~34 kg/s. Part of this mass loss occurs as a "planetary wind" along the dusk flank. The remainder probably occurs ultimately much deeper in the tail and along the distant dawn magnetopause, when the mass disconnects from the weakened planetary magnetic field.

  3. Time budget and activity rhythm of wild Great Bustard in winter

    Institute of Scientific and Technical Information of China (English)

    SUN Yanfeng; LI Suping; LI Juyong; WU Yuefeng; LI Jianping

    2006-01-01

    Instantaneous scanning and focal animal sampiing methods were used to record the behaviors of nine wild Great Bustards (Otis tarda) and their time budget from November 2004 to January 2005.The results indicated that foraging and resting time accounted for as high as 46.40% and 39.12%,respectively,while the rest of the behaviors,such as walking,alerting,preening and flying,only shared 6.83%,2.03%,2.64% and 1.84%,respectively.There were significant differences in foraging time,alert time and walking time between males and females (P<0.05).The preening and flying were closely related to males (Pearson's correlation,r=0.932),and it was similar for resting and walking in females (Pearson's correlation,r=0.716).Resting occurred mainly at dawn and dusk,and foraging appeared mostly from 9:30 to 11:30 and from 14:30 to 16:30.Non-parameter testing demonstrates that time budget among resting,flying and others in two temperature intervals (>-5℃ and≤-5℃) was significantly different.

  4. The application of infrared camera in mammal research in Guanyinshan Nature Reserve Shaanxi%红外相机技术在陕西观音山自然保护区兽类监测研究中的应用

    Institute of Scientific and Technical Information of China (English)

    武鹏峰; 刘雪华; 蔡琼; 何祥博; Melissa Songer; 朱云; 邵小明

    2012-01-01

    Since July 2009, the total 18 cameras were installed in the Guanyinshan Nature Reserve ( GNR) , Shaanxi Province. During our 24 months' monitoring from August 2009 to July 2011, we have collected a total of 1 755 mammal photos. The results show (1) a total of 22 mammal species were photographed. The first 6 species selected for analysis based on a relative abundance index (RAI) were Budorcas taxicolor, Naemorkedus goral, Elaphodus cephalophus, Sus scrofa, Capricornis sumatraensis and Muntiacus reevesi; their total percentage reaches 86. 04% . (2) The monthly RAI (MRAI) for the whole year varies among months. The greatest value of MRAI is acquired in July and the lowest in February. (3) Three of the six selected species demonstrated similar daily activity patterns, which has two peaks, one at dawn and one at dusk. The daily pattern of Naemorhedus goral also has two peaks, but they differe from those of the previous three species. The daily activity pattern of Sus scrofa shows a peak at noon and Capricornis sumatraensis was less active at the period of 10:00 -16:00. (4) The NRAI gave a clear indication of variation in nocturnality among the 6 species. Capricornis sumatraensis was most active at night and Sus scrofa was opposite.

  5. Infectious Disease and Grouping Patterns in Mule Deer.

    Directory of Open Access Journals (Sweden)

    María Fernanda Mejía Salazar

    Full Text Available Infectious disease dynamics are determined, to a great extent, by the social structure of the host. We evaluated sociality, or the tendency to form groups, in Rocky Mountain mule deer (Odocoileus hemionus hemionus from a chronic wasting disease (CWD endemic area in Saskatchewan, Canada, to better understand factors that may affect disease transmission. Using group size data collected on 365 radio-collared mule deer (2008-2013, we built a generalized linear mixed model (GLMM to evaluate whether factors such as CWD status, season, habitat and time of day, predicted group occurrence. Then, we built another GLMM to determine factors associated with group size. Finally, we used 3 measures of group size (typical, mean and median group sizes to quantify levels of sociality. We found that mule deer showing clinical signs of CWD were less likely to be reported in groups than clinically healthy deer after accounting for time of day, habitat, and month of observation. Mule deer groups were much more likely to occur in February and March than in July. Mixed-sex groups in early gestation were larger than any other group type in any season. Groups were largest and most likely to occur at dawn and dusk, and in open habitats, such as cropland. We discuss the implication of these results with respect to sociobiology and CWD transmission dynamics.

  6. Positive and negative ionospheric responses to the March 2015 geomagnetic storm from BDS observations

    Science.gov (United States)

    Jin, Shuanggen; Jin, Rui; Kutoglu, H.

    2017-06-01

    The most intense geomagnetic storm in solar cycle 24 occurred on March 17, 2015, and the detailed ionospheric storm morphologies are difficultly obtained from traditional observations. In this paper, the Geostationary Earth Orbit (GEO) observations of BeiDou Navigation Satellite System (BDS) are for the first time used to investigate the ionospheric responses to the geomagnetic storm. Using BDS GEO and GIMs TEC series, negative and positive responses to the March 2015 storm are found at local and global scales. During the main phase, positive ionospheric storm is the main response to the geomagnetic storm, while in the recovery phase, negative phases are pronounced at all latitudes. Maximum amplitudes of negative and positive phases appear in the afternoon and post-dusk sectors during both main and recovery phases. Furthermore, dual-peak positive phases in main phase and repeated negative phase during the recovery are found from BDS GEO observations. The geomagnetic latitudes corresponding to the maximum disturbances during the main and recovery phases show large differences, but they are quasi-symmetrical between southern and northern hemispheres. No clear zonal propagation of traveling ionospheric disturbances is detected in the GNSS TEC disturbances at high and low latitudes. The thermospheric composition variations could be the dominant source of the observed ionospheric storm effect from GUVI [O]/[N2] ratio data as well as storm-time electric fields. Our study demonstrates that the BDS (especially the GEO) observations are an important data source to observe ionospheric responses to the geomagnetic storm.

  7. A statistical study of single crest phenomenon in the equatorial ionospheric anomaly region using Swarm A satellite

    Science.gov (United States)

    Fathy, Adel; Ghamry, Essam

    2017-03-01

    Though the Equatorial Ionospheric Anomaly (EIA) is represented by two crests within ±15° latitude, a single crest is also observed in the entire ionosphere. Few studies have addressed single crest phenomena. A statistical study of 2237 single crest phenomenon from the in situ electron density measurements of Swarm A satellite was investigated during December 2013-December 2015. Our analysis focused on local time, seasonal, and both geographic and geomagnetic latitudinal variations. Our results show the following observations: 1 - The maximum number of events peaks mainly in the dayside region around 0800-1200 LT and these occur mainly within the magnetic equator. 2 - The maximum amplitude of the single crests take place most prominently during equinoxes. 3 - The majority of single crests occur in the northern hemisphere. 4 - The seasonal distribution of the events shows that the summer events are located further from the magnetic equator in the northern hemisphere and shift their locations into the southern hemisphere in winter, while spring events are centered along the magnetic equator. 5 - Dayside single crest events appear close to the magnetic equator and more centered on the equator in winter season. 6 - Dawn, night and dusk side events reverse their location from northern hemisphere in summer to southern hemisphere in winter.

  8. Ionospheric control of the magnetosphere: conductance

    Directory of Open Access Journals (Sweden)

    A. J. Ridley

    2004-01-01

    Full Text Available It is well known that the ionosphere plays a role in determining the global state of the magnetosphere. The ionosphere allows magnetospheric currents to close, thereby allowing magnetospheric convection to occur. The amount of current which can be carried through the ionosphere is mainly determined by the ionospheric conductivity. This paper starts to quantify the nonlinear relationship between the ionospheric conductivity and the global state of the magnetosphere. It is found that the steady-state magnetosphere acts neither as a current nor as a voltage generator; a uniform Hall conductance can influence the potential pattern at low latitudes, but not at high latitude; the EUV generated conductance forces the currents to close in the sunlight, while the potential is large on the nightside; the solar generated Hall conductances cause a large asymmetry between the dawn and dusk potential, which effects the pressure distribution in the magnetosphere; a uniform polar cap potential removes some of this asymmetry; the potential difference between solar minimum and maximum is ∼11%; and the auroral precipitation can be related to the local field-aligned current through an exponential function.

    Key words. Ionosphere (ionosphere-magnetosphere interactions; modelling and forecasting; polar ionosphere

  9. Space Technology 5 Multi-point Measurements of Near-Earth Magnetic Fields: Initial Results

    Science.gov (United States)

    Slavin, James A.; Le, G.; Strangeway, R. L.; Wang, Y.; Boardsen, S.A.; Moldwin, M. B.; Spence, H. E.

    2007-01-01

    The Space Technology 5 (ST-5) mission successfully placed three micro-satellites in a 300 x 4500 km dawn-dusk orbit on 22 March 2006. Each spacecraft carried a boom-mounted vector fluxgate magnetometer that returned highly sensitive and accurate measurements of the geomagnetic field. These data allow, for the first time, the separation of temporal and spatial variations in field-aligned current (FAC) perturbations measured in low-Earth orbit on time scales of approximately 10 sec to 10 min. The constellation measurements are used to directly determine field-aligned current sheet motion, thickness and current density. In doing so, we demonstrate two multi-point methods for the inference of FAC current density that have not previously been possible in low-Earth orbit; 1) the "standard method," based upon s/c velocity, but corrected for FAC current sheet motion, and 2) the "gradiometer method" which uses simultaneous magnetic field measurements at two points with known separation. Future studies will apply these methods to the entire ST-5 data set and expand to include geomagnetic field gradient analyses as well as field-aligned and ionospheric currents.

  10. On the nature of the plasma sheet boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Hones, E.W. Jr. (Mission Research Corp., Los Alamos, NM (USA) Los Alamos National Lab., NM (USA))

    1990-01-01

    The regions of the plasma sheet adjacent to the north and south lobes of the magnetotail have been described by many experimenters as locations of beams of energetic ions and fast-moving plasma directed primarily earthward and tailward along magnetic field lines. Measurements taken as satellites passed through one or the other of these boundary layers have frequently revealed near-earth mirroring of ions and a vertical segregation of velocities of both earthward-moving and mirroring ions with the fastest ions being found nearest the lobe-plasma sheet interface. These are features expected for particles from a distant tail source {bar E} {times} {bar B} drifting in a dawn-to-dusk electric field and are consistent with the source being a magnetic reconnection region. The plasma sheet boundary layers are thus understood as separatrix layers, bounded at their lobeward surfaces by the separatrices from the distant neutral line. This paper will review the observations that support this interpretation. 10 refs., 7 figs.

  11. Foraging movements of Audouin’s gull (Larus audouinii) in the Ebro Delta, NW Mediterranean: A preliminary satellite-tracking study

    Science.gov (United States)

    Christel, Isadora; Navarro, Joan; del Castillo, Marcos; Cama, Albert; Ferrer, Xavier

    2012-01-01

    A knowledge of the foraging strategies of marine predators is essential to understand the intrinsic factors controlling their distribution, abundance and their ecological function within the marine ecosystem. Here, we investigated for the first time the foraging movements and activity patterns of Audouin's gull Larus audouinii by using satellite-tracking data from eight breeding adults in the main colony of the species worldwide (Ebro Delta, NW Mediterranean). Tagged gulls foraged in the marine area close to the breeding colony (62% of foraging locations) and in the terrestrial area of the Ebro Delta (mainly rice fields; 38% of foraging locations). The foraging activity patterns changed significantly throughout the day; lower from dusk through the first half of the night (19-1 h; 32% of active locations) and higher during the rest of the day (1-19 h; 75.5 ± 4.3% of active locations). These results confirm the foraging plasticity of this seabird and, based on previous information about the dietary habits of this species, we hypothesize how its time-dependent activity patterns and habitat use could be associated with variations in the availability of marine food resources (e.g. diel vertical migrations of pelagic fish) and the exploitation of terrestrial resources (e.g. American crayfish Procambarus clarkii).

  12. Do phosphine resistance genes influence movement and dispersal under starvation?

    Science.gov (United States)

    Kaur, Ramandeep; Ebert, Paul R; Walter, Gimme H; Swain, Anthony J; Schlipalius, David I

    2013-10-01

    Phosphine resistance alleles might be expected to negatively affect energy demanding activities such as walking and flying, because of the inverse relationship between phosphine resistance and respiration. We used an activity monitoring system to quantify walking of Rhyzopertha dominica (F.) and a flight chamber to estimate their propensity for flight initiation. No significant difference in the duration of walking was observed between the strongly resistant, weakly resistant, and susceptible strains of R. dominica we tested, and females walked significantly more than males regardless of genotype. The walking activity monitor revealed no pattern of movement across the day and no particular time of peak activity despite reports of peak activity of R. dominica and Tribolium castaneum (Herbst) under field conditions during dawn and dusk. Flight initiation was significantly higher for all strains at 28 degrees C and 55% relative humidity than at 25, 30, 32, and 35 degrees C in the first 24 h of placing beetles in the flight chamber. Food deprivation and genotype had no significant effect on flight initiation. Our results suggest that known resistance alleles in R. dominica do not affect insect mobility and should therefore not inhibit the dispersal of resistant insects in the field.

  13. Generation of different long-period geomagnetic pulsations during a sudden impulse

    Science.gov (United States)

    Moiseyev, A. V.; Popov, V. I.; Mullayarov, V. A.; Samsonov, S. N.; Du, A.; Yoshikawa, A.

    2015-07-01

    The space-time characteristics of geomagnetic pulsations during a sudden impulse on August 4, 2010 have been analyzed using ground-based and satellite observations. It has been indicated that two types of geomagnetic pulsations with different spatial extensions, oscillation frequencies, and generations were observed at that time. It has been found that geomagnetic pulsations with identical oscillation frequencies (˜4.5 mHz) at different latitudes were observed, with a maximal amplitude in the dusk sector. Oscillations with close frequencies were registered in the solar wind in the IMF B z component. Higher-frequency (7-10 mHz) pulsations dependent on latitude were registered on the dawn side. It is assumed that geomagnetic pulsations with frequencies of ˜4.5 mHz were caused by oscillations penetrating from the interplanetary medium, and higher-frequency pulsations were Alfvén resonance oscillations generated during the compression of the magnetosphere. An asymmetric oscillation amplitude distribution relative to noon was caused by the IMF orthospiral orientation in this event.

  14. CAST reaches milestone but keeps on searching

    CERN Multimedia

    CERN Courier (september 2011 issue)

    2011-01-01

    After eight years of searching for the emission of a dark matter candidate particle, the axion, from the Sun, the CERN Axion Solar Telescope (CAST) has fulfilled its original physics programme.   Members of the CAST collaboration in July, together with dipole-based helioscope. CAST, the world’s most sensitive axion helioscope, points a recycled prototype LHC dipole magnet at the Sun at dawn and dusk, looking for the conversion of axions to X-rays. It incorporates four state-of-the-art X-ray detectors: three Micromegas detectors and a pn-CCD imaging camera attached to a focusing X-ray telescope that was recovered from the German space programme (see CERN Courier April 2010).  Over the years, CAST has operated with the magnet bores - the location of the axion conversion - in different conditions: first in vacuum, covering axion masses up to 20 meV/c2, and then with a buffer gas (4He and later 3He) at various densities, finally reaching the goal of 1.17 eV/c2 on 22 ...

  15. Energetic Neutral Atom Imaging with the POLAR CEPPAD/ IPS Instrument : Initial Forward Modeling Results

    Science.gov (United States)

    Henderson, M. G.; Reeves, G. D.; Moore, K. R.; Spence, H. E.; Jorgensen, A. M.; Fennell, J. F.; Blake, J. B.; Roelof, E. C.

    1999-01-01

    Although the primary function of the CEPPAD/IPS instrument on Polar is the measurement of energetic ions in-situ, it has also proven to be a very capable Energetic Neutral Atom (ENA) imager. Raw ENA images are currently being constructed on a routine basis with a temporal resolution of minutes during both active and quiet times. However, while analyses of these images by themselves provide much information on the spatial distribution and dynamics of the energetic ion population in the ring current. detailed modeling is required to extract the actual ion distributions. In this paper. we present the initial results of forward modeling an IPS ENA image obtained during a small geo-magnetic storm on June 9, 1997. The equatorial ion distribution inferred with this technique reproduces the expected large noon/midnight and dawn/dusk asymmetries. The limitations of the model are discussed and a number of modifications to the basic forward modeling technique are proposed which should significantly improve its performance in future studies.

  16. Fear of darkness, the full moon and the nocturnal ecology of African lions.

    Science.gov (United States)

    Packer, Craig; Swanson, Alexandra; Ikanda, Dennis; Kushnir, Hadas

    2011-01-01

    Nocturnal carnivores are widely believed to have played an important role in human evolution, driving the need for night-time shelter, the control of fire and our innate fear of darkness. However, no empirical data are available on the effects of darkness on the risks of predation in humans. We performed an extensive analysis of predatory behavior across the lunar cycle on the largest dataset of lion attacks ever assembled and found that African lions are as sensitive to moonlight when hunting humans as when hunting herbivores and that lions are most dangerous to humans when the moon is faint or below the horizon. At night, people are most active between dusk and 10:00 pm, thus most lion attacks occur in the first weeks following the full moon (when the moon rises at least an hour after sunset). Consequently, the full moon is a reliable indicator of impending danger, perhaps helping to explain why the full moon has been the subject of so many myths and misconceptions.

  17. Spawning ascent durations of pelagic spawning reef fishes

    Institute of Scientific and Technical Information of China (English)

    Caroline A. HABRUN; Gorka SANCHO

    2012-01-01

    Predation risks have been hypothesized to influence spawning behaviors of coral reef fishes that broadcast gametes pelagically.The duration of spawning ascents of 13 species were measured from video footage at a single spawning site for multiple coral reef fishes to investigate if this behavior was influenced by varying risks of predation.Fishes that spawned in pairs had ascents of longer duration than group-spawning species.Duration of spawning ascents did not vary between fishes spawning at daytime and dusk,nor between group-spawning species with specific anti-predatory morphological adaptations.These results indicate that risk of predation may not significantly influence the duration of spawning ascents of pair spawning reef fishes at our study site,while group-spawning behaviors are influenced by predation.Avoidance of egg predation by benthic organisms and female mate choice are more likely to influence the pelagic spawning behaviors of all fishes observed [Current Zoology 58 ( 1 ):95-102,2012].

  18. Japanese Encephalitis vector abundance and infection frequency in Cuddalore District, Tamil Nadu, India: a five-year longitudinal study

    Directory of Open Access Journals (Sweden)

    P. Philip Samuel

    2016-12-01

    Full Text Available An entomological monitoring of Japanese encephalitis vectors from the Cuddalore district, Tamil Nadu was undertaken at biweekly intervals for 1 hr after dusk for five years to find out the abundance and JE virus activity longitudinally in three villages. A total of 95,644 vectors belonging to 31 species constituted predominantly by Culex vishnui subgroup and Culex gelidus 98.5%. JE virus was identified from Cx. tritaeniorhynchus (18, Cx. vishnui (1 and Cx. gelidus (6 giving infection rate of 0.482, 0.608 and 0.221 respectively. Abundance of Cx. tritaeniorhynchus and Cx. gelidus differed significantly by area, season and year (P<0.05 whereas Cx. vishuni differed significantly by season and year (P<0.05. Transmission was not observed throughout all the seasons and the infection rate was recorded maximum during Hot-Wet season 0.46 (confidence interval: 0.17-1.02. Culex tritaeniorhynchus dominated the catch and the Culex gelidus steadily increased in its abundance during this period compared to the earlier studies conducted from these areas which acts as a secondary vector along with the major vector, Cx. tritaeniorhynchus.

  19. Diel periodicity of Drosophila suzukii (Diptera: Drosophilidae) under field conditions

    Science.gov (United States)

    Evans, Richard K.; Toews, Michael D.

    2017-01-01

    Drosophila suzukii Matsumura (Diptera: Drosophilidae), an economically important pest of blueberry and other thin-skinned fruits, persists and prolifically reproduces under seemingly lethal climatic conditions in the field. However, behavioral and physiological mechanisms employed by D. suzukii to tolerate such extreme climatic conditions in the field are unknown. The primary objective of this project was to investigate diel periodicity of D. suzukii and their reproductive success under field conditions as related by climatic factors such as temperature and relative humidity. Results show that D. suzukii reproductive success was significantly higher during the night (including dawn and dusk periods) than the day in terms of oviposition, pupation, adult eclosion, and the number of progeny per female. Female D. suzukii reproductive success was not significantly different between specific regions of a blueberry bush in relation to the amount of shade provided by the canopy. Our studies indicate that D. suzukii flight activity is crepuscular and is sensitive to fluctuations in temperature and relative humidity. Results also suggest that the majority of fly activity during peak hours is concentrated in areas around the border and within the center of blueberry orchards with little activity in the surrounding wooded areas. These findings suggest that D. suzukii prefers microclimate with mild temperatures and high humidity, and does not function well when exposed to direct sunlight with extreme heat. The authors propose that D. suzukii management strategies should be implemented during the early morning and immediately before darkness to maximize efficacy. PMID:28187140

  20. Fear of darkness, the full moon and the nocturnal ecology of African lions.

    Directory of Open Access Journals (Sweden)

    Craig Packer

    Full Text Available Nocturnal carnivores are widely believed to have played an important role in human evolution, driving the need for night-time shelter, the control of fire and our innate fear of darkness. However, no empirical data are available on the effects of darkness on the risks of predation in humans. We performed an extensive analysis of predatory behavior across the lunar cycle on the largest dataset of lion attacks ever assembled and found that African lions are as sensitive to moonlight when hunting humans as when hunting herbivores and that lions are most dangerous to humans when the moon is faint or below the horizon. At night, people are most active between dusk and 10:00 pm, thus most lion attacks occur in the first weeks following the full moon (when the moon rises at least an hour after sunset. Consequently, the full moon is a reliable indicator of impending danger, perhaps helping to explain why the full moon has been the subject of so many myths and misconceptions.

  1. Doppler micro sense and avoid radar

    Science.gov (United States)

    Gorwara, Ashok; Molchanov, Pavlo; Asmolova, Olga

    2015-10-01

    There is a need for small Sense and Avoid (SAA) systems for small and micro Unmanned Aerial Systems (UAS) to avoid collisions with obstacles and other aircraft. The proposed SAA systems will give drones the ability to "see" close up and give them the agility to maneuver through tight areas. Doppler radar is proposed for use in this sense and avoid system because in contrast to optical or infrared (IR) systems Doppler can work in more harsh conditions such as at dusk, and in rain and snow. And in contrast to ultrasound based systems, Doppler can better sense small sized obstacles such as wires and it can provide a sensing range from a few inches to several miles. An SAA systems comprised of Doppler radar modules and an array of directional antennas that are distributed around the perimeter of the drone can cover the entire sky. These modules are designed so that they can provide the direction to the obstacle and simultaneously generate an alarm signal if the obstacle enters within the SAA system's adjustable "Protection Border". The alarm signal alerts the drone's autopilot to automatically initiate an avoidance maneuver. A series of Doppler radar modules with different ranges, angles of view and transmitting power have been designed for drones of different sizes and applications. The proposed Doppler radar micro SAA system has simple circuitry, works from a 5 volt source and has low power consumption. It is light weight, inexpensive and it can be used for a variety of small unmanned aircraft.

  2. Large Scale Earth's Bow Shock with Northern IMF as simulated by PIC code in parallel with MHD model

    CERN Document Server

    Baraka, Suleiman M

    2016-01-01

    In this paper, we propose a 3D kinetic model (Particle-in-Cell PIC ) for the description of the large scale Earth's bow shock. The proposed version is stable and does not require huge or extensive computer resources. Because PIC simulations work with scaled plasma and field parameters, we also propose to validate our code by comparing its results with the available MHD simulations under same scaled Solar wind ( SW ) and ( IMF ) conditions. We report new results from the two models. In both codes the Earth's bow shock position is found to be ~14.8 RE along the Sun-Earth line, and ~ 29 RE on the dusk side. Those findings are consistent with past in situ observations. Both simulations reproduce the theoretical jump conditions at the shock. However, the PIC code density and temperature distributions are inflated and slightly shifted sunward when compared to the MHD results. Kinetic electron motions and reflected ions upstream may cause this sunward shift. Species distributions in the foreshock region are depicted...

  3. A Predictive Model of Geosynchronous Magnetopause Crossings

    CERN Document Server

    Dmitriev, A; Chao, J -K

    2013-01-01

    We have developed a model predicting whether or not the magnetopause crosses geosynchronous orbit at given location for given solar wind pressure Psw, Bz component of interplanetary magnetic field (IMF) and geomagnetic conditions characterized by 1-min SYM-H index. The model is based on more than 300 geosynchronous magnetopause crossings (GMCs) and about 6000 minutes when geosynchronous satellites of GOES and LANL series are located in the magnetosheath (so-called MSh intervals) in 1994 to 2001. Minimizing of the Psw required for GMCs and MSh intervals at various locations, Bz and SYM-H allows describing both an effect of magnetopause dawn-dusk asymmetry and saturation of Bz influence for very large southward IMF. The asymmetry is strong for large negative Bz and almost disappears when Bz is positive. We found that the larger amplitude of negative SYM-H the lower solar wind pressure is required for GMCs. We attribute this effect to a depletion of the dayside magnetic field by a storm-time intensification of t...

  4. Plasma convection in the magnetotail lobes: statistical results from Cluster EDI measurements

    Directory of Open Access Journals (Sweden)

    S. Haaland

    2008-08-01

    Full Text Available A major part of the plasma in the Earth's magnetotail is populated through transport of plasma from the solar wind via the magnetotail lobes. In this paper, we present a statistical study of plasma convection in the lobes for different directions of the interplanetary magnetic field and for different geomagnetic disturbance levels. The data set used in this study consists of roughly 340 000 one-minute vector measurements of the plasma convection from the Cluster Electron Drift Instrument (EDI obtained during the period February 2001 to June 2007. The results show that both convection magnitude and direction are largely controlled by the interplanetary magnetic field (IMF. For a southward IMF, there is a strong convection towards the central plasma sheet with convection velocities around 10 km s−1. During periods of northward IMF, the lobe convection is almost stagnant. A By dominated IMF causes a rotation of the convection patterns in the tail with an oppositely directed dawn-dusk component of the convection for the northern and southern lobe. Our results also show that there is an overall persistent duskward component, which is most likely a result of conductivity gradients in the footpoints of the magnetic field lines in the ionosphere.

  5. Sea snakes (Lapemis curtus) are sensitive to low-amplitude water motions.

    Science.gov (United States)

    Westhoff, Guido; Fry, Bryan G; Bleckmann, Horst

    2005-01-01

    The sea snake Lapemis curtus is a piscivorous predator that hunts at dusk. Like land snakes, sea snakes have scale sensillae that may be mechanoreceptive, i.e. that may be useful for the detection of water motions produced by prey fish. In addition, inner ear hair cells of sea snakes may also be involved in the detection of hydrodynamic stimuli. We generated water motions and pressure fluctuations with a vibrating sphere. In the test range 50-200 Hz evoked potentials were recorded from the midbrain of L. curtus in response to vibrating sphere stimuli. In terms of water displacement the lowest threshold amplitudes were in the frequency range 100-150 Hz. In this range peak-to-peak water displacement amplitudes of 1.8 microm (at 100 Hz) and 2.0 microm (150 Hz) generated a neural response in the most sensitive animal. Although this low sensitivity may be sufficient for the detection of fish-generated water motions, it makes it unlikely that L. curtus has a special hydrodynamic sense.

  6. Environmental influences on patterns of vertical movement and site fidelity of grey reef sharks (Carcharhinus amblyrhynchos at aggregation sites.

    Directory of Open Access Journals (Sweden)

    Gabriel M S Vianna

    Full Text Available We used acoustic telemetry to describe the patterns of vertical movement, site fidelity and residency of grey reef sharks (Carcharhinus amblyrhynchos on the outer slope of coral reefs in Palau, Micronesia, over a period of two years and nine months. We tagged 39 sharks (mostly adult females of which 31 were detected regularly throughout the study. Sharks displayed strong inter-annual residency with greater attendance at monitored sites during summer than winter months. More individuals were detected during the day than at night. Mean depths of tagged sharks increased from 35 m in winter to 60 m in spring following an increase in water temperature at 60 m, with maximum mean depths attained when water temperatures at 60 m stabilised around 29°C. Sharks descended to greater depths and used a wider range of depths around the time of the full moon. There were also crepuscular cycles in mean depth, with sharks moving into shallower waters at dawn and dusk each day. We suggest that daily, lunar and seasonal cycles in vertical movement and residency are strategies for optimising both energetic budgets and foraging behaviour. Cyclical patterns of movement in response to environmental variables might affect the susceptibility of reef sharks to fishing, a consideration that should be taken into account in the implementation of conservation strategies.

  7. Candle light-style OLED: a plausibly human-friendly safe night light

    Science.gov (United States)

    Jou, Jwo-Huei; Chen, Po-Wei; Hsieh, Chun-Yu; Wang, Ching-Chiun; Chen, Chien-Chih; Tung, F.-C.; Chen, Szu-Hao; Wang, Yi-Shan

    2013-09-01

    Candles emit sensationally-warm light with a very-low color-temperature, comparatively most suitable for use at night. In response to the need for such a human-friendly night light, we demonstrate the employment of a high number of candle light complementary organic emitters to generate mimic candle light based on organic light emitting diode (OLED). One resultant candle light-style OLED shows a very-high color rendering index, with an efficacy at least 300 times that of candles or twice that of an incandescent bulb. The device can be fabricated, for example, by using four candle light complementary emitters, namely: red, yellow, green, and sky-blue phosphorescent dyes, vacuum-deposited into two emission layers, separated by a nano-layer of carrier modulation material to maximize both the desirable very-high color rendering index and energy efficiency, while keeping the blue emission very low and red emission high to obtain the desirable low color temperature. With different layer structures, the OLEDs can also show color tunable between that of candle light and dusk-hue. Importantly, a romantic sensation giving and supposedly physiologically-friendly candle light-style emission can hence be driven by electricity in lieu of the hydrocarbon-burning and greenhouse gas releasing candles that were invented 5,000 years ago.

  8. Kinetic effects on the Kelvin-Helmholtz instability in ion-to-magnetohydrodynamic scale transverse velocity shear layers: Particle simulations.

    Science.gov (United States)

    Nakamura, T K M; Hasegawa, H; Shinohara, I

    2010-04-01

    Ion-to-magnetohydrodynamic scale physics of the transverse velocity shear layer and associated Kelvin-Helmholtz instability (KHI) in a homogeneous, collisionless plasma are investigated by means of full particle simulations. The shear layer is broadened to reach a kinetic equilibrium when its initial thickness is close to the gyrodiameter of ions crossing the layer, namely, of ion-kinetic scale. The broadened thickness is larger in B⋅Ω0 case, where Ω is the vorticity at the layer. This is because the convective electric field, which points out of (into) the layer for B⋅Ω0), extends (reduces) the gyrodiameters. Since the kinetic equilibrium is established before the KHI onset, the KHI growth rate depends on the broadened thickness. In the saturation phase of the KHI, the ion vortex flow is strengthened (weakened) for B⋅Ω0), due to ion centrifugal drift along the rotational plasma flow. In ion inertial scale vortices, this drift effect is crucial in altering the ion vortex size. These results indicate that the KHI at Mercury-like ion-scale magnetospheric boundaries could show clear dawn-dusk asymmetries in both its linear and nonlinear growth.

  9. The Polar Cap (PC) index. A critical review of methods and a new approach.

    Science.gov (United States)

    Stauning, Peter

    2013-04-01

    The Polar Cap (PC) index introduced by Troshichev and Andrezen (1985) is derived from polar magnetic variations and is mainly a measure of the intensity of the transpolar ionospheric currents. These currents relate to the polar cap antisunward ionospheric plasma convection driven by the dawn-dusk electric field, which in turn is generated by the interaction of the solar wind with the Earth's magnetosphere. Coefficients to calculate PCN and PCS index values from polar magnetic variations recorded at Thule and Vostok, respectively, have been derived by several different procedures in the past. Approval of a final PC index procedure is pending at the International Association for Geomagnetism and Aeronomy (IAGA) for a decision possibly at the General Assembly in 2013. The presentation discusses the principal differences between the various PC index procedures and provides comparisons between coefficient and index values derived using the different procedures. It will be demonstrated that depending on the procedure, PC index values derived in the past, and used in many publications, may differ substantially although the same basic geomagnetic data were used. Finally, a new approach to define a unified PC index procedure, built from the best elements of the three different current versions, is outlined.

  10. Simulation Studies for a Space-Based CO2 Lidar Mission

    Science.gov (United States)

    Kawa, S. R.; Mao, J.; Abshire, J. B.; Collatz, G. J.; Sun, X.; Weaver, C. J.

    2010-01-01

    We report results of initial space mission simulation studies for a laser-based, atmospheric CO2 sounder, which are based on real-time carbon cycle process modelling and data analysis. The mission concept corresponds to the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) recommended by the US National Academy of Sciences' Decadal Survey. As a pre-requisite for meaningful quantitative evaluation, we employ a CO2 model that has representative spatial and temporal gradients across a wide range of scales. In addition, a relatively complete description of the atmospheric and surface state is obtained from meteorological data assimilation and satellite measurements. We use radiative transfer calculations, an instrument model with representative errors and a simple retrieval approach to quantify errors in 'measured' CO2 distributions, which are a function of mission and instrument design specifications along with the atmospheric/surface state. Uncertainty estimates based on the current instrument design point indicate that a CO2 laser sounder can provide data consistent with ASCENDS requirements and will significantly enhance our ability to address carbon cycle science questions. Test of a dawn/dusk orbit deployment, however, shows that diurnal differences in CO2 column abundance, indicative of plant photosynthesis and respiration fluxes, will be difficult to detect

  11. Ionospheric conductance distribution and MHD wave structure: observation and model

    Directory of Open Access Journals (Sweden)

    F. Budnik

    Full Text Available The ionosphere influences magnetohydrodynamic waves in the magnetosphere by damping because of Joule heating and by varying the wave structure itself. There are different eigenvalues and eigensolutions of the three dimensional toroidal wave equation if the height integrated Pedersen conductivity exceeds a critical value, namely the wave conductance of the magnetosphere. As a result a jump in frequency can be observed in ULF pulsation records. This effect mainly occurs in regions with gradients in the Pedersen conductances, as in the auroral oval or the dawn and dusk areas. A pulsation event recorded by the geostationary GOES-6 satellite is presented. We explain the observed change in frequency as a change in the wave structure while crossing the terminator. Furthermore, selected results of numerical simulations in a dipole magnetosphere with realistic ionospheric conditions are discussed. These are in good agreement with the observational data.

    Key words. Ionosphere · (Ionosphere · magnetosphere interactions · Magnetospheric physics · Magnetosphere · ionosphere interactions · MHD waves and instabilities.

  12. The Surf Zone Ichthyoplankton Adjacent to an Intermittently Open Estuary, with Evidence of Recruitment during Marine Overwash Events

    Science.gov (United States)

    Cowley, P. D.; Whitfield, A. K.; Bell, K. N. I.

    2001-03-01

    The composition, structure and seasonality of ichthyoplankton in the surf zone adjacent to the mouth of the intermittently open East Kleinemonde Estuary (33°32'S, 27°03'E) were investigated over a period of 2 years. Altogether 451 fishes, representing at least 21 taxa from 14 families, were collected. The assemblage was dominated by postflexion larvae of euryhaline marine species that are dependent on estuaries as nursery areas. The sparid Rhabdosargus holubi was the most abundant taxon and constituted more than 77% of the total catch. A distinct modal size class was identified for R. holubi , while the mean individual size of this and other abundant taxa was comparable to the observed recruitment size range reported from a wide variety of estuarine nursery habitats in southern Africa. Periodic regression analyses revealed significant peaks in abundance of larval R. holubi during late winter (August), at down and dusk, at new and full moon (spring tides), and on the flood stage of the tidal cycle. Evidence for estuarine immigration during marine overwash events (surging rough seas that enter the estuary) is provided by (1) the stranding of postflexion larvae in the region of the closed estuary mouth following these events, and (2) back extrapolation from length modes within the estuary to coincide with such an event. The advantages and disadvantages of such a recruitment strategy are discussed.

  13. Deciphering time measurement: the role of circadian 'clock' genes and formal experimentation in insect photoperiodism.

    Science.gov (United States)

    Saunders, D S; Bertossa, R C

    2011-05-01

    This review examines possible role(s) of circadian 'clock' genes in insect photoperiodism against a background of many decades of formal experimentation and model building. Since ovarian diapause in the genetic model organism Drosophila melanogaster has proved to be weak and variable, recent attention has been directed to species with more robust photoperiodic responses. However, no obvious consensus on the problem of time measurement in insect photoperiodism has yet to emerge and a variety of mechanisms are indicated. In some species, expression patterns of clock genes and formal experiments based on the canonical properties of the circadian system have suggested that a damped oscillator version of Pittendrigh's external coincidence model is appropriate to explain the measurement of seasonal changes in night length. In other species extreme dampening of constituent oscillators may give rise to apparently hourglass-like photoperiodic responses, and in still others there is evidence for dual oscillator (dawn and dusk) photoperiodic mechanisms of the internal coincidence type. Although the exact role of circadian rhythmicity and of clock genes in photoperiodism is yet to be settled, Bünning's general hypothesis (Bünning, 1936) remains the most persuasive unifying principle. Observed differences between photoperiodic clocks may be reflections of underlying differences in the clock genes in their circadian feedback loops. Copyright © 2011. Published by Elsevier Ltd.

  14. Observed Foreshock Ions which are Actually Behind the Martian Bow Shock

    Science.gov (United States)

    Frahm, Rudy A.; Yamauchi, Masatoshi; Winningham, J. David; Lundin, Rickard; Sharber, James R.; Nilsson, Hans; Coates, Andrew J.; Mukherjee, Joey

    2016-04-01

    The Mars Express (MEx) Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment contains ion and electron instruments for conducting plasma measurements. On January 23, 2012, during in-bound travel of MEx in the southern hemisphere of Mars traveling from its dawn side toward periapsis at dusk, the plasma instruments measured foreshock-like ion beams extending from outside the bow shock and into the magnetosphere, continuing to a distance of about a proton gyroradius from the bow shock. These ion beams were mostly protons, were observed to have energies greater than solar wind protons, and were not gyrating, in agreement with reflections of the solar wind proton beam. Furthermore, in the foreshock region, the ion energy gradually decreased toward the magnetosheath, in agreement with an acceleration by an outward-directed electric field in the bow shock. The observations also suggest that this electric field exists even inside the magnetosheath, within the distance of a proton gyroradius from the bow shock.

  15. Longitudinal studies of Japanese encephalitis virus infection in vector mosquitoes in Kurnool district, Andhra Pradesh, South India.

    Science.gov (United States)

    Arunachalam, N; Murty, U S N; Narahari, D; Balasubramanian, A; Samuel, P Philip; Thenmozhi, V; Paramasivan, R; Rajendran, R; Tyagi, B K

    2009-05-01

    A 4-yr (2002-2006) entomological study was carried out in Kurnool district, Andhra Pradesh state, south India, to identify the mosquito vectors of Japanese encephalitis virus (family Flaviviridae, genus Flavivirus, JEV). In total, 37,139 female mosquitoes belonging five genera and 18 species resting on vegetation were collected in villages and periurban areas at dusk. Mosquito species composition and pattern of JEV infection in mosquitoes varied in periurban and rural areas. In periurban area, Culex gelidus Theobald was abundant, making up 49.7% of total catch followed by Culex tritaeniorhynchus Giles (44.5%). In rural area, Cx. tritaeniorhynchus was predominant, making up 78.9% of total catch followed by Culex quinquefasciatus Say (10.8%), Anopheles subpictus Grassi (7.1%), and Cx. gelidus (1.1%). In light trap collections, Cx. gelidus and Cx. tritaeniorhynchus predominated in periurban and rural areas, respectively. Of 50,145 mosquitoes screened JEV isolations were made only from Cx. gelidus and Cx. tritaeniorhynchus. Based on high abundance and frequent JEV isolation, Cx. tritaeniorhynchus was found to be the principal vector in both areas, whereas Cx. gelidus plays a secondary vector role in periurban areas only.

  16. Evaluation of super intense geomagnetic storms and related structures of the interplanetary medium through the observation of cosmic rays of high energy surface; Analise de tempestades geomagneticas super intensas e de estruturas do meio interplanetario relacionadas, atraves da observacao de raios cosmicos de superficie de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Savian, Jairo Francisco; Schuch, Nelson J., E-mail: savian@lacesm.ufsm.br, E-mail: njschuch@lacesm.ufsm.br [Centro Regional Sul de Pesquisas Espaciais - CRSPE/INPE-MCT, Santa Maria, RS (Brazil); Silva, Marlos Rockenbach da; Lago, Alisson dal; Gonzalez, Walter Demetrio, E-mail: marlos@dge.inpe.br, E-mail: dallago@dge.inpe.br, E-mail: gonzalez@dge.inpe.br [Instituto Nacional de Pesquisas Espaciais - INPE-MCT, Sao Jose dos Campos, SP (Brazil); Munakata, Kazuoki [Physics Department, Shinshu University, Matsumoto (Japan)

    2005-04-15

    It is believed that the physical mechanism responsible for the transference of energy from the solar wind to the Earth magnetosphere is the reconnection between the interplanetary magnetic field and the terrestrial magnetic field (Tsurutani and Gonzalez, 1997). The necessary criterion for a intense geomagnetic storms to occur, Dst < -100nT, is the existence of a dawn-dusk interplanetary electric field larger than 5 mV/m, for a period larger than 3 hours. Cosmic rays have been studied as a natural phenomenon that can tell much about both Earth's environment in space and distant astrophysical processes (Jokipii, 2000). A solar disturbance propagating away from the Sun affects the pre-existing population of galactic cosmic rays in a number of ways. The most famous one is known as the 'Forbush decrease', which is a suppression of ground cosmic-ray counts observed during geomagnetic disturbances. The objective of this work is to study the response of the Southern Space Observatory ground Muon Telescope observations, installed in Sao Martinho da Serra, RS, Brazil, to 3 super intense geomagnetic storms, combining observation provided by L1 satellites and ground detectors. (author)

  17. Rax : developmental and daily expression patterns in the rat pineal gland and retina.

    Science.gov (United States)

    Rohde, Kristian; Klein, David C; Møller, Morten; Rath, Martin F

    2011-09-01

    Retina and anterior neural fold homeobox (Rax) gene encodes a transcription factor essential for vertebrate eye development. Recent microarray studies indicate that Rax is expressed in the adult rat pineal gland and retina. The present study reveals that Rax expression levels in the rat change significantly during retinal development with a peak occurring at embryonic day 18, whereas Rax expression in the pineal is relatively delayed and not detectable until embryonic day 20. In both tissues, Rax is expressed throughout postnatal development into adulthood. In the mature rat pineal gland, the abundance of Rax transcripts increases 2-fold during the light period with a peak occurring at dusk. These findings are consistent with the evidence that Rax is of functional importance in eye development and suggest a role of Rax in the developing pineal gland. In addition, it would appear possible that Rax contributes to phenotype maintenance in the mature retina and pineal gland and may facilitate 24-h changes in the pineal transcriptome.

  18. The large-scale magnetospheric electric field observed by Double Star TC-1

    Directory of Open Access Journals (Sweden)

    C. Carr

    2010-09-01

    Full Text Available The relationship between the average structure of the inner magnetospheric large-scale electric field and geomagnetic activity levels has been investigated by Double Star TC-1 data for radial distances ρ between 4.5 RE and 12.5 RE and MLT between 18:00 h and 06:00 h from July to October in 2004 and 2005. The sunward component of the electric field decreases monotonically as ρ increases and approaches zero as the distance off the Earth is greater than 10 RE. The dawn-dusk component is always duskward. It decreases at about 6 RE where the ring current is typically observed to be the strongest and shows strong asymmetry with respect to the magnetic local time. Surprisingly, the average electric field obtained from TC-1 for low activity is almost comparable to that observed during moderate activity, which is always duskward at the magnetotail (8 RE~12 RE.

  19. Properties of Jupiter's magnetospheric turbulence observed by the Galileo spacecraft

    Science.gov (United States)

    Tao, Chihiro; Sahraoui, Fouad; Fontaine, Dominique; Patoul, Judith; Chust, Thomas; Kasahara, Satoshi; Retinò, Alessandro

    2015-04-01

    In collisionless plasmas, turbulence is thought to play an important role in mass transport and energy dissipation. Magnetic fluctuations in the Jovian magnetosphere are essential in a turbulent state. Previous studies of that turbulence have focused on the large scales using low time resolution of magnetic field data. Here we extend those studies to cover a wider range of scales by combining both low and high-time-resolution data of Galileo magnetometer. We use particle data from the plasma instrument and include energetic particle contributions to estimate the local plasma parameters. We obtain 11 power spectra of magnetic field in the frequency range of 10-4-1 Hz, which covers both magnetohydrodynamics and ion kinetic scales. The frequencies of the evidenced spectral breaks are found to be relatively well correlated with the characteristic scales of heavy ion. The spectral indices below and above the spectral breaks are found to be broad and cover the ranges of 0.6-1.9 and 1.7-2.5, respectively. An analysis of higher-order statistics shows an intermittent feature of the turbulence, found to be more prominent in the plasma sheet than in the lobe. Furthermore, a statistical survey of the power of the fluctuations using low-time-resolution data suggests a radially varying dawn-dusk asymmetry: the total power is larger in the duskside (dawnside) at 80 RJ), which would reflect flow shear and global magnetospheric activity.

  20. Pollination biology and floral scent chemistry of the Neotropical chiropterophilous Parkia pendula.

    Science.gov (United States)

    Piechowski, D; Dötterl, S; Gottsberger, G

    2010-01-01

    During the past several decades, the pollination biology of Old World plant species pollinated by flying foxes and of New World plants pollinated by highly specialized nectar-feeding glossophagine bats has been studied in detail. However, little is known about Neotropical plants that are pollinated by less specialized phyllostomid bats. Therefore, we studied the pollination biology of Parkia pendula, a tree pollinated by Phyllostomus. Flowers of P. pendula are arranged in capitula, and a capitulum is composed of approximately 800 hermaphrodite flowers and 260 sterile flowers. The sterile flowers produced a total of 7.4 ml nectar per night, with a sugar concentration of 14.95%, and proline as the dominant amino acid. Nectar production is highest at dusk and ends at 03:00 h. The floral scent is dominated by monoterpenoids (97.9%), with (E)-beta-ocimene being the dominant (84.0%) compound. No sulfur compounds were detected. The capitula are heavily visited by four species of phyllostomid bats, of which Phyllostomus discolor is the most abundant (98.9%). Nectar production per capitulum is within the reported range of nectar produced by this pantropical genus (5.0-8.0 ml). This genus-wide range seems to be optimal for attracting non-specialized nectar-feeding bats and forces them to visit capitula of several trees to satisfy their dietary needs, thus increasing the probability of cross-pollination for this plant.

  1. Long-term acoustical observations of the mesopelagic fish Maurolicus muelleri reveal novel and varied vertical migration patterns

    KAUST Repository

    Staby, A

    2011-11-15

    We studied the temporal dynamics in the vertical distribution of Maurolicus muelleri scattering layers (SL) by examining continuous acoustic recordings over a 15 mo period in Masfjorden, Norway, complemented by intermittent sampling campaigns. The data revealed known patterns as normal diel vertical migration (DVM), midnight sinking between dusk and dawn, and periods without migrations, as well as novel behaviours consisting of early morning ascents, reverse diel vertical migrations, and interrupted ascents in the evening. During the first autumn of the study, adult fish modified their normal DVM behaviour by suspending their migration in the evening, yet ascending toward the surface in the later part of the night to reach upper layers during dawn. This behaviour was not observed during the second autumn of the study. By mid- to end of November (1st autumn), adult fish had suspended the nocturnal ascent entirely, and in the subsequent period until the end of January, a fraction of the population rather performed limited reverse migrations, slightly shifting their vertical distribution upwards during the first part of the day. From January to March 2008, fish interrupted their evening ascent at apparently random intervals and returned to deeper waters, instead of completing a full ascent to the surface. Our study underlines the value of long-term recordings, with the results suggesting that M. muelleri has the capability of changing its behaviour in response to ontogeny and internal state (satiation and hunger) as well as to external stimuli.

  2. Positive and negative ionospheric responses to the March 2015 geomagnetic storm from BDS observations

    Science.gov (United States)

    Jin, Shuanggen; Jin, Rui; Kutoglu, H.

    2017-01-01

    The most intense geomagnetic storm in solar cycle 24 occurred on March 17, 2015, and the detailed ionospheric storm morphologies are difficultly obtained from traditional observations. In this paper, the Geostationary Earth Orbit (GEO) observations of BeiDou Navigation Satellite System (BDS) are for the first time used to investigate the ionospheric responses to the geomagnetic storm. Using BDS GEO and GIMs TEC series, negative and positive responses to the March 2015 storm are found at local and global scales. During the main phase, positive ionospheric storm is the main response to the geomagnetic storm, while in the recovery phase, negative phases are pronounced at all latitudes. Maximum amplitudes of negative and positive phases appear in the afternoon and post-dusk sectors during both main and recovery phases. Furthermore, dual-peak positive phases in main phase and repeated negative phase during the recovery are found from BDS GEO observations. The geomagnetic latitudes corresponding to the maximum disturbances during the main and recovery phases show large differences, but they are quasi-symmetrical between southern and northern hemispheres. No clear zonal propagation of traveling ionospheric disturbances is detected in the GNSS TEC disturbances at high and low latitudes. The thermospheric composition variations could be the dominant source of the observed ionospheric storm effect from GUVI [O]/[N2] ratio data as well as storm-time electric fields. Our study demonstrates that the BDS (especially the GEO) observations are an important data source to observe ionospheric responses to the geomagnetic storm.

  3. Ring Current Dynamics in Moderate and Strong Storms: Comparative Analysis of TWINS and IMAGE/HENA Data with the Comprehensive Ring Current Model

    Science.gov (United States)

    Buzulukova, N.; Fok, M.-C.; Goldstein, J.; Valek, P.; McComas, D. J.; Brandt, P. C.

    2010-01-01

    We present a comparative study of ring current dynamics during strong and moderate storms. The ring current during the strong storm is studied with IMAGE/HENA data near the solar cycle maximum in 2000. The ring current during the moderate storm is studied using energetic neutral atom (ENA) data from the Two Wide-Angle Imaging Neutral- Atom Spectrometers (TWINS) mission during the solar minimum in 2008. For both storms, the local time distributions of ENA emissions show signatures of postmidnight enhancement (PME) during the main phases. To model the ring current and ENA emissions, we use the Comprehensive Ring Current Model (CRCM). CRCM results show that the main-phase ring current pressure peaks in the premidnight-dusk sector, while the most intense CRCM-simulated ENA emissions show PME signatures. We analyze two factors to explain this difference: the dependence of charge-exchange cross section on energy and pitch angle distributions of ring current. We find that the IMF By effect (twisting of the convection pattern due to By) is not needed to form the PME. Additionally, the PME is more pronounced for the strong storm, although relative shielding and hence electric field skewing is well developed for both events.

  4. IMF Bx effects on the ionospheric current system

    Science.gov (United States)

    Laundal, K.; Reistad, J.; Ostgaard, N.; Tenfjord, P.; Snekvik, K.; Finlay, C. C.

    2016-12-01

    A statistical analysis of UV images have shown a weak but significant difference in auroral intensity at the dusk side for different signs of the IMF Bx component (Reistad et al., 2014). This difference was interpreted as an effect of stronger upward Region 1 currents in the north (south) when Bx is negative (positive). The different Region 1 currents are due to the different field line curvature on newly opened field lines, which leads to more efficient conversion of solar wind kinetic energy to electromagnetic energy. However, the aurora is only an indirect measurement of the Region 1 current, and the relationship between the two quantities is not one-to-one. To our knowledge, the Bx effect has never been reported in direct studies of currents. In this study we use the high precision magnetic field instruments on the CHAMP and Swarm satellites to model global field-aligned and ionospheric currents. By binning the data with respect to sunlight conditions and IMF orientation, we test the explanation of the results by Reistad et al.

  5. Bird Activity Analysis Using Avian Radar Information in Naval Air Station airport, WA

    Science.gov (United States)

    Wang, J.; Herricks, E.

    2010-12-01

    The number of bird strikes on aircraft has increased sharply over recent years and airport bird hazard management has gained increasing attention in wildlife management and control. Evaluation of bird activity near airport is very critical to analyze the hazard of bird strikes. Traditional methods for bird activity analysis using visual counting provide a direct approach to bird hazard assessment. However this approach is limited to daylight and good visual conditions. Radar has been proven to be a useful and effective tool for bird detection and movement analysis. Radar eliminates observation bias and supports consistent data collection for bird activity analysis and hazard management. In this study bird activity data from the Naval Air Station Whidbey Island was collected by Accipiter Avian Radar System. Radar data was pre-processed by filtering out non-bird noises, including traffic vehicle, aircraft, insects, wind, rainfall, ocean waves and so on. Filtered data is then statistically analyzed using MATLAB programs. The results indicated bird movement dynamics in target areas near the airport, which includes (1) the daily activity varied at dawn and dusk; (2) bird activity varied by target area due to the habitat difference; and (3) both temporal and spatial movement patterns varied by bird species. This bird activity analysis supports bird hazard evaluation and related analysis and modeling to provide very useful information in airport bird hazard management planning.

  6. Accaleration of Electrons of the Outer Electron Radiation Belt and Auroral Oval Dynamics

    Science.gov (United States)

    Antonova, Elizaveta; Ovchinnikov, Ilya; Riazantseva, Maria; Znatkova, Svetlana; Pulinets, Maria; Vorobjev, Viachislav; Yagodkina, Oksana; Stepanova, Marina

    2016-07-01

    We summarize the results of experimental observations demonstrating the role of auroral processes in the formation of the outer electron radiation belt and magnetic field distortion during magnetic storms. We show that the auroral oval does not mapped to the plasma sheet proper (region with magnetic field lines stretched in the tailward direction). It is mapped to the surrounding the Earth plasma ring in which transverse currents are closed inside the magnetosphere. Such currents constitute the high latitude continuation of the ordinary ring current. Mapping of the auroral oval to the region of high latitude continuation of the ordinary ring current explains the ring like shape of the auroral oval with finite thickness near noon and auroral oval dynamics during magnetic storms. The auroral oval shift to low latitudes during storms. The development of the ring current produce great distortion of the Earth's magnetic field and corresponding adiabatic variations of relativistic electron fluxes. Development of the asymmetric ring current produce the dawn-dusk asymmetry of such fluxes. We analyze main features of the observed processes including formation of sharp plasma pressure profiles during storms. The nature of observed pressure peak is analyzed. It is shown that the observed sharp pressure peak is directly connected with the creation of the seed population of relativistic electrons. The possibility to predict the position of new radiation belt during recovery phase of the magnetic storm using data of low orbiting and ground based observations is demonstrated.

  7. Diel Patterns of Activity for Insect Pollinators of Two Oil Palm Species (Arecales : Arecaceae).

    Science.gov (United States)

    Auffray, Thomas; Frérot, Brigitte; Poveda, Roberto; Louise, Claude; Beaudoin-Ollivier, Laurence

    2017-01-01

    The pollination of two oil palm species, Elaeis guineensis Jacquin and Elaeis oleifera Cortés (Arecales: Arecaceae), depends on a mutualistic relation with insects, which use male inflorescences as a brood site, and visits female inflorescences lured by the emitted odor, which is similar to that of males. Although the activity of visiting the inflorescences by these insects is critical for the adequate natural pollination of the host plant, their activity is poorly documented. In the present study, we determine the diel activity of two specialized pollinator weevils (Coleoptera: Curculionidae) on inflorescences of their respective host-palm: Elaeidobius kamerunicus Faust specialized on E. guineensis, and Grasidius hybridus O'Brien and Beserra specialized on E. oleifera. The average timing of activity was studied by using passive interception traps. Then the pattern and the duration were refined by using aspiration trapping within the active period for each insect species at the male and female inflorescences. All the experiments were conducted in an Ecuadorian oil palm plantation, located close to Amazonian forest. El. kamerunicus and G. hybridus were found to be the pollinators of E. guineensis and E. oleifera, respectively. The two species differed in their diel pattern of activity: E. kamerunicus was active in the morning and G. hybridus during a short period at dusk. For both palm species, insect visits were synchronous on both male and female inflorescences. The synchronicity is discussed as a strategy to maintain the relation mutualistic between partners. These findings increase our understanding of the oil palm pollination system.

  8. Comparison of time-restricted and ad libitum self-feeding on the growth, feeding behavior and daily digestive enzyme profiles of Atlantic salmon

    Science.gov (United States)

    Shi, Ce; Liu, Ying; Yi, Mengmeng; Zheng, Jimeng; Tian, Huiqin; Du, Yishuai; Li, Xian; Sun, Guoxiang

    2016-07-01

    Although it has been hypothesized that a predictable feeding regime in animals allows physiological variables to be adjusted to maximize nutrient utilization and, hence, better growth performance, the assumption has rarely been tested. This study compares the Effects of time-restricted versus free access self-feeding on the growth, feeding behavior and daily digestive enzyme rhythms of Atlantic salmon (Salmo salar). In an experiment that lasted 6 weeks, fish (109.9 g) were divided into two groups: group 1 had free access to a self-feeder (FA); group 2 received three meals per day (2 h per meal) at dawn, midday and dusk via a time-restricted self-feeder (TR). At the end of the experiment, the fish were sampled every 3 h over a 24-h period. The results showed that the TR fish quickly synchronized their feeding behavior to the feeding window and their blood glucose showed a significant postprandial increase, while FA fish displayed no statistically significant rhythms (P0.05). In conclusion, the study failed to confirm a link between the entrainment of daily digestive enzyme profiles and growth performance, with the TR group showing comparatively poor blood glucose regulation.

  9. Properties of current sheet thinning at x ˜- 10 to -12 RE

    Science.gov (United States)

    Artemyev, A. V.; Angelopoulos, V.; Runov, A.; Petrokovich, A. A.

    2016-07-01

    We report on Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations of current sheet thinning in Earth's magnetotail at around x =- 10 to -12 Earth radii. The THEMIS spacecraft configuration in October-December 2015 allows us to construct both gradients that contribute to the cross-tail current density jy=μ0-1(∂Bx/∂z-∂Bz/∂x) (GSM coordinates). For 17 events when the spacecraft observed a gradual Bz decrease and jy increase, we find the following average scaling relations: for the current density jy˜Bz-7/4, for the lobe magnetic field BL˜Bz-1/4, and for the plasma density ni˜Bz-3/4. We show that the temperature of ions and electrons decreases and the plasma pressure gradient ∂p/∂x rapidly increases during current sheet thinning. The scale Lx=(∂lnp/∂x)-1 decreases a few thousand kilometers. We also consider current carriers in thinning current sheets: both ion and electron current-dominated current sheets, preferentially located near dusk and midnight, respectively, are found.

  10. Space Technology 5 (ST-5) Multipoint Observations of Temporal and Spatial Variability of Field-Aligned Currents

    Science.gov (United States)

    Le, Guan

    2010-01-01

    Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from ST5. The data demonstrate that mesoscale current structures are commonly embedded within large-scale field-aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of about 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are about 1 min for meso-scale currents and about 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.

  11. Space Technology 5 (ST-5) Observations of Field-Aligned Currents: Temporal Variability

    Science.gov (United States)

    Le, Guan

    2010-01-01

    Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from STS. The data demonstrate that masoscale current structures are commonly embedded within large-scale field-aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of about 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are about I min for meso-scale currents and about 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.

  12. Space Technology 5 Multi-Point Observations of Temporal Variability of Field-Aligned Currents

    Science.gov (United States)

    Le, Guan; Wang, Yongli; Slavin, James A.; Strangeway, Robert J.

    2008-01-01

    Space Technology 5 (ST5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this paper, we present a study of the temporal variability of field-aligned currents using multi-point magnetic field measurements from ST5. The data demonstrate that meso-scale current structures are commonly embedded within large-scale field-aligned current sheets. The meso-scale current structures are very dynamic with highly variable current density and/or polarity in time scales of approximately 10 min. They exhibit large temporal variations during both quiet and disturbed times in such time scales. On the other hand, the data also shown that the time scales for the currents to be relatively stable are approximately 1 min for meso-scale currents and approximately 10 min for large scale current sheets. These temporal features are obviously associated with dynamic variations of their particle carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of meso-scale field-aligned currents are found to be consistent with those of auroral parallel electric field.

  13. Functional trophic composition of the ichthyofauna of forest streams in eastern Brazilian Amazon

    Directory of Open Access Journals (Sweden)

    Gabriel Lourenco Brejao

    2013-06-01

    Full Text Available This study aimed to describe the functional organization of the ichthyofauna of forest streams from northeastern Pará State, Brazil, based on behavioral observation of species' feeding tactics. Seven streams were sampled between June and November, 2010, during snorkeling sessions, totaling 91h 51min of visual censuses at day, dusk, and night periods. Seventy three species distributed in six orders, 26 families and 63 genera were observed, with dominance of Characiformes, followed by Siluriformes. From information gathered by ad libitum observations, each species was included in one of 18 functional trophic groups (FTGs, according to two main characteristics: (1 its most frequently observed feeding tactic; and (2 its spatial distribution in the stream environment, considering their horizontal (margins or main channel and vertical (water column dimensions. The most frequent FTGs observed were Nocturnal invertebrate pickers (9 species, Diurnal channel drift feeders (8 spp., Diurnal surface pickers (7 spp., and Ambush and stalking predators (6 spp.. The FTGs herein defined enable a comparative analysis of the structure and composition of ichthyofauna in different basins and environmental conditions, which presents an alternative approach to the use of taxonomic structure in ecological studies. The ichthyofauna classification based in FTGs proposed in this study is compared to three other classifications, proposed by Sazima (1986, Sabino & Zuanon (1998 and Casatti et al. (2001.

  14. Dancing in the dark: darkness as a signal in plants.

    Science.gov (United States)

    Seluzicki, Adam; Burko, Yogev; Chory, Joanne

    2017-01-03

    Daily cycles of light and dark provide an organizing principle and temporal constraints under which life on Earth evolved. While light is often the focus of plant studies, it is only half the story. Plants continuously adjust to their surroundings, taking both dawn and dusk as cues to organize their growth, development and metabolism to appropriate times of day. In this review, we examine the effects of darkness on plant physiology and growth. We describe the similarities and differences between seedlings grown in the dark versus those grown in light-dark cycles, and the evolution of etiolated growth. We discuss the integration of the circadian clock into other processes, looking carefully at the points of contact between clock genes and growth-promoting gene-regulatory networks in temporal gating of growth. We also examine daily starch accumulation and degradation, and the possible contribution of dark-specific metabolic controls in regulating energy and growth. Examining these studies together reveals a complex and continuous balancing act, with many signals, dark included, contributing information and guiding the plant through its life cycle. The extraordinary interconnection between light and dark is manifest during cycles of day and night and during seedling emergence above versus below the soil surface.

  15. A Research on the Narrative Time in Shanxi Opera%《秦腔》叙事时间研究

    Institute of Scientific and Technical Information of China (English)

    苗变丽

    2011-01-01

    Shanxi Opera adopts narrative tactics of "folk".From the characteristics of text time,the detailed narration and slow development form feature of routing time of repetition,dispersion and liberalness.The actual influence on the characters is the time of dusk,rotation of solar terms and four seasons,which is "the time of bits and pieces".At the same time,the author also adopts two methods to break the limitation of routing time: the time formed over generations and the method of narration by the mad.%《秦腔》采取了一种"乡俗"的叙事策略。从文本时间特性方面看,细说慢写的风格形成了重复、弥散和绵延的日常性时间特征。对人物产生实际影响的,是日暮晨昏、节气变化、寒暑交替,这是"一堆鸡零狗碎的泼烦日子"。但同时作者又采取了两种方法来超越日常时间庸常性的拘囿。这体现在两个方面,一是世代生成性时间,二是疯癫叙事的手法。

  16. Bird on a (live) wire

    Energy Technology Data Exchange (ETDEWEB)

    Farr, M.

    2003-09-30

    Bird mortality as a result of contact with power lines is discussed. U. S. statistics are cited, according to which 174 million birds annually die as a result of contact with power lines, specifically when birds touch two phases of current at the same time. Raptors are particularly vulnerable to power-line electrocution due to their habit of perching on the highest vantage point available as they survey the ground for prey. Hydro lines located in agricultural areas, with bodies of water on one side and fields on the other, also obstruct flight of waterfowl as dusk and dawn when visibility is low. Various solutions designed to minimize the danger to birds are discussed. Among these are: changing the configuration of wires and cross arms to make them more visible to birds in flight and less tempting as perches, and adding simple wire markers such as flags, balloons, and coloured luminescent clips that flap and twirl in the wind. There is no evidence of any coordinated effort to deal with this problem in Ontario. However, a report is being prepared for submission to Environment Canada outlining risks to birds associated with the growing number of wind turbine power generators (negligible compared with power lines and communications towers), and offering suggestions on remedial measures. The Fatal Light Awareness Program (FLAP) also plans to lobby the Canadian Wildlife Service to discuss the possibility of coordinating efforts to monitor, educate about and ultimately reduce this form of bird mortality.

  17. The role of oxygen ions in the formation of a bifurcated current sheet in the magnetotail

    CERN Document Server

    Dalena, S; Zimbardo, G; Veltri, P

    2010-01-01

    Cluster observations in the near-Earth magnetotail have shown that sometimes the current sheet is bifurcated, i.e. it is divided in two layers. The influence of magnetic turbulence on ion motion in this region is investigated by numerical simulation, taking into account the presence of both protons and oxygen ions. The magnetotail current sheet is modeled as a magnetic field reversal with a normal magnetic field component $B_n$, plus a three-dimensional spectrum of magnetic fluctuations $\\delta {\\bf B}$, which represents the observed magnetic turbulence. The dawn-dusk electric field E$_y$ is also included. A test particle simulation is performed using different values of $\\delta {\\bf B}$, E$_y$ and injecting two different species of particles, O$^+$ ions and protons. O$^+$ ions can support the formation of a double current layer both in the absence and for large values of magnetic fluctuations ($\\delta B/B_0 = 0.0$ and $\\delta B/B_0 \\geq 0.4$, where B$_0$ is the constant magnetic field in the magnetospheric l...

  18. Magnetic turbulence and particle dynamics in the Earth’s magnetotail

    Directory of Open Access Journals (Sweden)

    G. Zimbardo

    Full Text Available The influence of magnetic turbulence in the near-Earth magnetotail on ion motion is investigated by numerical simulation. The magnetotail current sheet is modelled as a magnetic field reversal with a normal magnetic field com-ponent Bn , plus a three-dimensional spectrum of magnetic fluctuations dB which represents the observed magnetic turbulence. The dawn-dusk electric field Ey is also considered. A test particle simulation is performed using different values of Bn and of the fluctuation level dB/B0. We show that when the magnetic fluctuations are taken into account, the particle dynamics is deeply affected, giving rise to an increase in the cross tail transport, ion heating, and current sheet thickness. For strong enough turbulence, the current splits in two layers, in agreement with recent Cluster observations.

    Key words. Magnetospheric physics (magnetospheric configuration and dynamics – Interplanetary physics (MHD waves and turbulence – Electromagnetics (numerical methods

  19. Temporal and Spatial Foraging Behavior of the Larvae of the Fall Webworm Hyphantria cunea

    Directory of Open Access Journals (Sweden)

    Terrence D. Fitzgerald

    2015-01-01

    Full Text Available During their first three larval stadia, caterpillars of Hyphantria cunea (Lepidoptera: Arctiidae are patch-restricted foragers, confining their activity to a web-nest they construct in the branches of the host tree. Activity recordings of eight field colonies made over 46 colony-days showed that the later instars become central place foragers, leaving their nests at dusk to feed at distant sites and then returning to their nests in the morning. Colonies maintained in the laboratory showed that same pattern of foraging. In Y-choice laboratory experiments, caterpillars were slow to abandon old, exhausted feeding sites in favor of new food finds. An average of approximately 40% of the caterpillars in five colonies still selected pathways leading to exhausted sites at the onset of foraging bouts over those leading to new sites after feeding exclusively at the new sites on each of the previous four days. On returning to their nests in the morning, approximately 23% of the caterpillars erred by selecting pathways that led them away from the nest rather than toward it and showed no improvement over the course of the study. The results of these Y-choice studies indicate that, compared to other previously studied species of social caterpillars, the webworm employs a relatively simple system of collective foraging.

  20. Community metabolism in shallow coral reef and seagrass ecosystems, lower Florida Keys

    Science.gov (United States)

    Turk, Daniela; Yates, Kimberly K.; Vega-Rodriguez, Maria; Toro-Farmer, Gerardo; L'Esperance, Chris; Melo, Nelson; Ramsewak, Deanesch; Estrada, S. Cerdeira; Muller-Karger, Frank E.; Herwitz, Stan R.; McGillis, Wade

    2016-01-01

    Diurnal variation of net community production (NEP) and net community calcification (NEC) were measured in coral reef and seagrass biomes during October 2012 in the lower Florida Keys using a mesocosm enclosure and the oxygen gradient flux technique. Seagrass and coral reef sites showed diurnal variations of NEP and NEC, with positive values at near-seafloor light levels >100–300 µEinstein m-2 s-1. During daylight hours, we detected an average NEP of 12.3 and 8.6 mmol O2 m-2 h-1 at the seagrass and coral reef site, respectively. At night, NEP at the seagrass site was relatively constant, while on the coral reef, net respiration was highest immediately after dusk and decreased during the rest of the night. At the seagrass site, NEC values ranged from 0.20 g CaCO3 m-2 h-1 during daylight to -0.15 g CaCO3 m-2 h-1 at night, and from 0.17 to -0.10 g CaCO3 m-2 h-1 at the coral reef site. There were no significant differences in pH and aragonite saturation states (Ωar) between the seagrass and coral reef sites. Decrease in light levels during thunderstorms significantly decreased NEP, transforming the system from net autotrophic to net heterotrophic.

  1. Measured comparison of the inversion periods for polarimetric and conventional thermal long-wave IR (LWIR) imagery

    Science.gov (United States)

    Felton, M.; Gurton, K. P.; Roth, L. E.; Pezzaniti, J. L.; Chenault, D. B.

    2009-08-01

    We report the results of a multi-day diurnal study in which radiometrically calibrated polarimetric and conventional thermal imagery is recorded in the LWIR to identify/compare the respective time periods in which minimum target contrast is achieved, e.g., thermal inversion periods are typically experienced during dusk and dawn. Imagery is recorded with a polarimetric IR sensor employing a 324x256 microbolometer array using a spinning achromatic retarder to perform the polarimetric filtering. The images used in this study include the S0, normalized S1, and normalized S2 Stokes images and the degree of linear polarization (DOLP) images of a scene containing military vehicles and the natural background. In addition, relevant meteorological parameters measured during the test period include air temperature, ambient loading in the LWIR, relative humidity, and cloud cover, height and density. The data shows that the chief factors affecting polarimetric contrast are the amount of thermal emission from the objects in the scene and the abundance of LWIR sources in the optical background. In addition, we found that contrast between targets and background within polarimetric images often remains relatively high during periods of low thermal contrast.

  2. Assimilative Modeling of Ionospheric Disturbances with FORMOSAT-3/COSMIC and Ground-Based GPS Measurements

    Directory of Open Access Journals (Sweden)

    Xiaoqing Pi

    2009-01-01

    Full Text Available The four-dimensional Global Assimilative Ionospheric Model (GAIM is applied to a study of ionospheric disturbances. The investigation is focused on disturbance features, particularly in the altitude and latitude dimensions, at low latitudes during a geomagnetic storm on 7 August 2006, under solar minimum conditions. The modeling of storm-time ionospheric state (electron density is conducted by assimilating an unprecedented volume of line-of-sight TEC data collected by the Global Positioning System (GPS occultation receivers on board six FORMOSAT-3/COSMIC satellites and geodetic-quality GPS receivers at two hundred globally-distributed ground tracking stations.With a band-limited Kalman filter technique to update the ionospheric state, the assimilative modeling reveals a pronounced enhancement in the equatorial anomaly in the East Asia sector during dusk and evening hours. The disturbance characteristics, obtained by comparing with the quiet conditions prior to the storm also modeled in this study through data assimilation, include lifted F layer and reduced electron density in the equatorial region, enhanced density at the magnetically conjugate anomaly latitudes, and tilted feature of density increase towards higher altitudes at lower latitudes. The characteristics are attributed to the enhanced plasma fountain effect driven by an enhanced eastward zonal electric field. These results enable us to distinguish the storm-time electric field perturbations clearly from other sources during the storm. The possible origins of electric field perturbations are also discussed, including penetration of the magnetospheric electric field and wind dynamo disturbances.

  3. Cross-tail current evolution during substorm dipolarization

    Directory of Open Access Journals (Sweden)

    A. T. Y. Lui

    2013-06-01

    Full Text Available We examine evolution of the cross-tail current during substorm current disruption/dipolarization using observations from two satellites in the near-Earth magnetotail at the downtail distances of 8–9 RE. By choosing times when these two satellites are separated, mainly in the north–south distance in the tail current sheet, precise determination of current density in the layer embedded between these satellites can be obtained with Ampère's law. Two such events are examined and several common features are found. The current densities in the layer embedded by the two satellites were reduced by ~ 40–70% during substorm dipolarization. The changes in current densities have the fast kinetic timescale, i.e., in seconds, implying a kinetic process for current disruption/dipolarization. The estimated power within the current layer was mainly dissipative in the dawn–dusk direction and mainly dynamo in the Sun–tail direction that is needed to drive the north–south substorm current system in the ionosphere. Remote sensing of the energization site with the ion sounding technique shows that the energization site was initially earthward of the satellite and moved down the tail at later times. Breakdown of the frozen-in condition occurred intermittently during the disturbance interval. These features provide important clues to the substorm onset process.

  4. Magnetotail electric fields observed from lunar orbit

    Science.gov (United States)

    Mccoy, J. E.; Lin, R. P.; Mcguire, R. E.; Chase, L. M.; Anderson, K. A.

    1975-01-01

    Direct observations of convection electric fields in the earth's magnetotail are reported. The electric fields have been measured from lunar orbit by detection of the E x B/B-squared drift displacement of low-energy electrons at the limb of the moon. It is found that electric fields range in magnitude from a value less than or equal to 0.02 mV/m, the limit of sensitivity of the method, to 2 mV/M. The typical value is 0.15 mV/M, and the corresponding convection velocity is 15 km/s. The sense of the electric field is almost always dawn to dusk. The electric field is often variable on a time scale of hours and sometimes minutes. The observations indicate that the electric field is not uniform across the magnetotail. If it is assumed that the typical measured electric-field value represents an average over the inhomogeneities, the potential drop across the entire tail is of the order of 40 kV.

  5. On the orbital variability of Ganymede's atmosphere

    Science.gov (United States)

    Leblanc, F.; Oza, A. V.; Leclercq, L.; Schmidt, C.; Cassidy, T.; Modolo, R.; Chaufray, J. Y.; Johnson, R. E.

    2017-09-01

    Ganymede's atmosphere is produced by radiative interactions with its surface, sourced by the Sun and the Jovian plasma. The sputtered and thermally desorbed molecules are tracked in our Exospheric Global Model (EGM), a 3-D parallelized collisional model. This program was developed to reconstruct the formation of the upper atmosphere/exosphere of planetary bodies interacting with solar photon flux and magnetospheric and/or the solar wind plasmas. Here, we describe the spatial distribution of the H2O and O2 components of Ganymede's atmosphere, and their temporal variability along Ganymede's rotation around Jupiter. In particular, we show that Ganymede's O2 atmosphere is characterized by time scales of the order of Ganymede's rotational period with Jupiter's gravity being a significant driver of the spatial distribution of the heaviest exospheric components. Both the sourcing and the Jovian gravity are needed to explain some of the characteristics of the observed aurora emissions. As an example, the O2 exosphere should peak at the equator with systematic maximum at the dusk equator terminator. The sputtering rate of the H2O exosphere should be maximum on the leading hemisphere because of the shape of the open/close field lines boundary and displays some significant variability with longitude.

  6. Competitive interactions between walleye (Sander vitreus) and smallmouth bass (Micropterus dolomieu) under various controlled conditions

    Science.gov (United States)

    Wuellner, M.R.; Graeb, B.D.S.; Willis, D.W.; Galster, B.J.; Selch, T.M.; Chipps, S.R.

    2011-01-01

    The range of smallmouth bass (Micropterus dolomieu) is expanding northward, creating new interactions with native predators, including walleye (Sander vitreus). We used a series of experiments to investigate competition between walleye (WAE) and smallmouth bass (SMB) at different life stages and light conditions, identified behaviors that allowed one fish to outcompete another, and evaluated whether prey switching mitigated competitive interactions. Juvenile and adult SMB appeared to outcompete WAE when fed during the daytime; neither species dominated when fed near dusk. Attack rates and capture efficiencies of both species were similar with an intra- or interspecific competitor, but SMB often exploited prey before the competitor had a chance to feed (exploitative competition) or displayed agonistic behaviors toward a potential competitor (interference competition). Prey selectivity of WAE or SMB did not differ when by themselves or with a potential competitor. These results indicate that SMB could outcompete WAE under limiting prey conditions due to the aggressive nature of SMB, but resources may be partitioned at least along a temporal scale. ?? 2011 Taylor & Francis.

  7. Solar wind - magnetosphere coupling efficiency during ejecta and sheath region driven geomagnetic storms

    Science.gov (United States)

    Myllys, Minna; Kilpua, Emilia; Lavraud, Benoit

    2016-04-01

    We have investigated the effect of key solar wind driving parameters on solar wind- magnetosphere coupling efficiency during sheath and magnetic cloud driven storms. The particular focus of the study was on the coupling efficiency dependence with Alfven Mach number (MA). The efficiency has been estimated using the dawn-dusk component of the interplanetary electric field (EY), Newell and Borovsky functions as a proxy for the energy inflow and the polar cap potential (PCN), auroral electrojet (AE) and SYM-H indices as the measure of the energy output. We have also performed a time delay analysis between the input parameters and the geomagnetic indices. We demonstrate that the PCN index distinctively shows both a MA dependent saturation and a MA-independent saturation, pointing to the existence of at least two underlying physical mechanisms for the saturation of the index. By contrast, we show that the AE index saturates, but that the saturation of this index is independent of the solar wind MA. Finally we find that the SYM-H index does not seem to saturate and that the absence of saturation is independent of the MA regime.

  8. The Polar Cap index: A critical review of methods and a new approach

    Science.gov (United States)

    Stauning, Peter

    2013-08-01

    The Polar Cap (PC) index introduced by Troshichev and Andrezen (1985) is derived from polar magnetic variations and is mainly a measure of the intensity of the transpolar ionospheric currents. These currents relate to the polar cap antisunward ionospheric plasma convection driven by the dawn-dusk electric fields, which in turn are generated by the interaction of the solar wind with the Earth's magnetosphere. Coefficients to calculate PCN and PCS index values from polar magnetic variations recorded at Thule and Vostok, respectively, have been derived by several different procedures in the past. The PCN index is found in seven different versions while the PCS index is found in five different versions in past publications. Recent publications (in 2011 and 2012) still convey three different PCN and two different PCS indices. The presentation here discusses the principal differences between the various PC index procedures and provides comparisons between coefficient and index values derived using the different procedures. Finally, a new approach to define a simplified PC index procedure is outlined.

  9. Comparison of Polar Cap (PC) index calculations.

    Science.gov (United States)

    Stauning, P.

    2012-04-01

    The Polar Cap (PC) index introduced by Troshichev and Andrezen (1985) is derived from polar magnetic variations and is mainly a measure of the intensity of the transpolar ionospheric currents. These currents relate to the polar cap antisunward ionospheric plasma convection driven by the dawn-dusk electric field, which in turn is generated by the interaction of the solar wind with the Earth's magnetosphere. Coefficients to calculate PCN and PCS index values from polar magnetic variations recorded at Thule and Vostok, respectively, have been derived by several different procedures in the past. The first published set of coefficients for Thule was derived by Vennerstrøm, 1991 and is still in use for calculations of PCN index values by DTU Space. Errors in the program used to calculate index values were corrected in 1999 and again in 2001. In 2005 DMI adopted a unified procedure proposed by Troshichev for calculations of the PCN index. Thus there exists 4 different series of PCN index values. Similarly, at AARI three different sets of coefficients have been used to calculate PCS indices in the past. The presentation discusses the principal differences between the various PC index procedures and provides comparisons between index values derived from the same magnetic data sets using the different procedures. Examples from published papers are examined to illustrate the differences.

  10. Rapid mass movement of chloroplasts during segment formation of the calcifying siphonalean green alga, Halimeda macroloba.

    Directory of Open Access Journals (Sweden)

    Anthony W D Larkum

    Full Text Available BACKGROUND: The calcifying siphonalean green alga, Halimeda macroloba is abundant on coral reefs and is important in the production of calcium carbonate sediments. The process by which new green segments are formed over-night is revealed here for the first time. METHODOLOGY/PRINCIPAL FINDINGS: Growth of new segments was visualised by epifluorescence and confocal microscopy and by pulse amplitude modulation (PAM fluorimetry. Apical colourless proto-segments were initiated on day 1, and formed a loose network of non-calcified, non-septate filaments, containing no chloroplasts. Rapid greening was initiated at dusk by i the mass movement of chloroplasts into these filaments from the parent segment and ii the growth of new filaments containing chloroplasts. Greening was usually complete in 3-5 h and certainly before dawn on day 2 when the first signs of calcification were apparent. Mass chloroplast movement took place at a rate of ∼0.65 µm/s. Photosynthetic yield and rate remained low for a period of 1 to several hours, indicating that the chloroplasts were made de novo. Use of the inhibitors colchicine and cytochalasin d indicated that the movement process is dependent on both microtubules and microfilaments. SIGNIFICANCE: This unusual process involves the mass movement of chloroplasts at a high rate into new segments during the night and rapid calcification on the following day and may be an adaptation to minimise the impact of herbivorous activity.

  11. The dependence of the LLBL thickness on IMF Bz and By components

    Science.gov (United States)

    Znatkova, S. S.; Antonova, E. E.; Pulinets, M. S.; Kirpichev, I. P.; Riazantseva, M. O.

    2016-07-01

    The thickness of the low latitude boundary layer (LLBL) is studied as a function of interplanetary magnetic field (IMF) using the data of THEMIS mission. The data from intersections of LLBL by Themis-A and -C satellites are analyzed. Solar wind parameters are provided by Themis-B satellite located before the bow shock. We use earlier developed method of LLBL thickness determination based on the analysis of the variation of plasma velocity in the layer perpendicular to the magnetopause. The database for the present analysis consists of 109 single satellite LLBL crossings where the values of LLBL thickness are obtained. The time shift of solar wind propagation from the spacecraft performing measurements outside the bow shock to the LLBL is taken into account. We analyze the dependence of LLBL thickness on IMF Bz and By using data of IMF measurements with 3 s resolution and produce the 180 s averaging of these data. Large scattering of the values of LLBL thickness and the weak dependence on IMF is demonstrated. Dawn-dusk asymmetry of LLBL thickness is not observed. The dependence of LLBL thickness on IMF clock angle is discussed.

  12. Effects of fasting in the holy month of Ramadan on the uric acid, urea, and creatinine levels: A narrative review

    Directory of Open Access Journals (Sweden)

    Sayed Alireza Mirsane

    2016-12-01

    Full Text Available Fasting during the month of Ramadan is one of the Five Pillars of Islam. During this holy month, healthy Muslims abstain from eating, drinking, and smoking from dawn to dusk. Although fasting is obligatory for every adult Muslim, if it has hazardous effects on the body, it is prohibited. Due to some Islamic principles, patients are exempted from fasting; however, due to the willingness of some individuals to fast, there are concerns about its effects on urea, uric acid, and creatine levels. Atypical levels of these compounds can cause serious disorders or indicate abnormal renal function. The present narrative review is aimed to investigate the effect of abnormally high levels of urea, uric acid, and creatinine on one’s health and effects of fasting during Ramadan on these indicators. Articles were searched from PubMed, Elsevier and Google Scholar and then they were evaluated. It can be concluded that fasting does not have any adverse effects on the urea, uric acid, and creatinine levels according to the above-mentioned studies.

  13. Propagation and source of Pc5 frequency range pulsation at cusp latitude

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Two induction magnetometers have been installed at Chinese Zhongshan Station and Australia Davis Station, Antarctica respectively. We adopt the cross-spectral analysis technique to analyze the data of the two induction magnetometers, in June, September, December 1996 and March 1997, and to investigate Pc5 frequency range pulsation (150 600 s) occurrence and propagation in cusp latitude. The results are summarized as follows: At Zhongshan-Davis Station, the magnetic pulsations in Pc5 frequency band can occurs over a wide time, but more frequently at pre local magnetic noon and pre local magnetic midnight. The Pc5 pulsations have no significant seasonal variation in the amplitude, occurrence and propagation. The amplitude has a small peak at pre local magnetic noon and large value sometimes at pre local magnetic midnight. In daytime, the Pc5 pulsations propagate westward in morning and eastward in afternoon, and reversal at local magnetic noon. In nighttime, the Pc5 pulsations propagate westward before 20:00 MLT and eastward after 20:00 MLT. Near dusk time, the Pc5 pulsations propagate irregularly. These characteristics indicate that the Pc5 pulsations have different source at different local magnetic time.

  14. Insect abundance over Chinese rice fields in relation to environmental parameters, studied with a polarization-sensitive CW near-IR lidar system

    Science.gov (United States)

    Zhu, Shiming; Malmqvist, Elin; Li, Wansha; Jansson, Samuel; Li, Yiyun; Duan, Zheng; Svanberg, Katarina; Feng, Hongqiang; Song, Ziwei; Zhao, Guangyu; Brydegaard, Mikkel; Svanberg, Sune

    2017-07-01

    Effective monitoring of flying insects is of major societal importance in view of the role of insects as indispensable pollinators, destructive disease vectors and economically devastating agricultural pests. The present paper reports on monitoring of flying agricultural pests using a continuous-wave lidar system in a rice-field location in Southern China. Using a Scheimpflug arrangement, range resolution over several 100 m long observational paths was achieved. The system operates with two perpendicularly polarized near-infrared lasers, which are activated intermittently, and back-scattered radiation from insects was recorded by a linear array detector placed after a linear polarizer. Our polarization sensitive system was used to monitor the flying insect diurnal activity and also the influence of changes in weather conditions, e.g., the occurrence of rain. Activity strongly peaked at dusk and rose again, although to a lower extent, just before dawn. At the onset of rainfall, a strong increase in insect counts occurred which was interpreted as the rain-induced bringing down of high-altitude migrant insects.

  15. Reflected solar wind ions and downward accelerated ionospheric ions during the January 1997 magnetic cloud event

    Science.gov (United States)

    Dempsey, D. L.; Burch, J. L.; Huddleston, M. M.; Pollock, C. J.; Waite, J. H., Jr.; Wüest, M.; Moore, T. E.; Shelley, E. G.

    On January 11, 1997, at 03:40:00 UT, while Polar was traveling up the dusk flank toward apogee, two ion instruments, TIDE and TIMAS, detected upflowing H+ with an energy/pitch-angle dispersion resembling an ionospheric reflection of freshly injected solar wind ions. In the same region of space, TIDE and TIMAS observed cold beams of O+ and H+ traveling down the field line with equal bulk velocities. We interpret these ion signatures as concurrent observations of mirrored solar wind ions and downward accelerated ionospheric ions. By 03:42:00, an energy/pitch-angle dispersion of downward moving ions at very low energies was clearly evident in the TIDE data. This additional signature is interpreted as an indication of reconnection on the same field line in the southern hemisphere. We explain this unique combination of plasma distributions in terms of high-latitude reconnection and magnetic field line convection during northward-IMF conditions associated with the January 1997 magnetic cloud event.

  16. Puma predation on radiocollared and uncollared bighorn sheep

    Directory of Open Access Journals (Sweden)

    Johnson Christine K

    2009-11-01

    Full Text Available Abstract Background We used Global Positioning System (GPS data from radiocollared pumas (Puma concolor to identify kill sites of pumas preying upon an endangered population of bighorn sheep (Ovis canadensis in southern California. Our aims were to test whether or not pumas selected radiocollared versus uncollared bighorn sheep, and to identify patterns of movement before, during, and after kills. Findings Three pumas killed 23 bighorn sheep over the course of the study, but they did not preferentially prey on marked (radiocollared versus unmarked bighorn sheep. Predation occurred primarily during crepuscular and nighttime hours, and 22 kill sites were identified by the occurrence of 2 or more consecutive puma GPS locations (a cluster within 200 m of each other at 1900, 0000, and 0600 h. Conclusion We tested the "conspicuous individual hypothesis" and found that there was no difference in puma predation upon radiocollared and uncollared bighorn sheep. Pumas tended to move long distances before and after kills, but their movement patterns immediately post-kill were much more restricted. Researchers can exploit this behaviour to identify puma kill sites and investigate prey selection by designing studies that detect puma locations that are spatially clustered between dusk and dawn.

  17. Photic and pineal modulation of food anticipatory circadian activity rhythms in rodents.

    Science.gov (United States)

    Patton, Danica F; Parfyonov, Maksim; Gourmelen, Sylviane; Opiol, Hanna; Pavlovski, Ilya; Marchant, Elliott G; Challet, Etienne; Mistlberger, Ralph E

    2013-01-01

    Restricted daily feeding schedules entrain circadian oscillators that generate food anticipatory activity (FAA) rhythms in nocturnal rodents. The location of food-entrainable oscillators (FEOs) necessary for FAA remains uncertain. The most common procedure for inducing circadian FAA is to limit food access to a few hours in the middle of the light period, when activity levels are normally low. Although light at night suppresses activity (negative masking) in nocturnal rodents, it does not prevent the expression of daytime FAA. Nonetheless, light could reduce the duration or magnitude of FAA. If so, then neural or genetic ablations designed to identify components of the food-entrainable circadian system could alter the expression of FAA by affecting behavioral responses to light. To assess the plausibility of light as a potential mediating variable in studies of FAA mechanisms, we quantified FAA in rats and mice alternately maintained in a standard full photoperiod (12h of light/day) and in a skeleton photoperiod (two 60 min light pulses simulating dawn and dusk). In both species, FAA was significantly and reversibly enhanced in the skeleton photoperiod compared to the full photoperiod. In a third experiment, FAA was found to be significantly attenuated in rats by pinealectomy, a procedure that has been reported to enhance some effects of light on behavioral circadian rhythms. These results indicate that procedures affecting behavioral responses to light can significantly alter the magnitude of food anticipatory rhythms in rodents.

  18. Fields of rice: health hazards for women and unborn children.

    Science.gov (United States)

    Batliwala, S

    1988-01-01

    A death information study, to determine why the infant mortality rate failed to fall below 75/1000, was begun in January 1982, after 9 years of accomplishments by the rural health research project in Raigad district of coastal Maharashtra. All data were collected by 27 female rural health workers, some of whom were illiterate but received help from villagers. Death records included name, sex, age, date and time of death, and cause of death or symptoms before death. In the 0-6 age group, 64% of the deaths were girls. 80% of the dead children were infant deaths, and of these, 75% were neonatal, suggesting the influence of prenatal, obstetric and postnatal factors and maternal nutrition. The majority were related to premature and low birth weight babies. Another striking observation was that 40% of all infant deaths occurred in July-October, and 50% of these were stillbirths and premature births. July and August are the months when all women (and no men) work transplanting rice seedlings. This work is done by bending or squatting from dawn to dusk. Thus, rice culture must be considered an occupational hazard for women in late pregnancy.

  19. Ionosphere of venus: first observations of day-night variations of the ion composition.

    Science.gov (United States)

    Taylor, H A; Brinton, H C; Bauer, S J; Hartle, R E; Cloutier, P A; Daniell, R E; Donahue, T M

    1979-07-06

    The Bennett radio-frequency ion mass spectrometer on the Pioneer Venus orbiter is returning the first direct composition evidence of the processes responsible for the formation and maintenance of the nightside ionosphere. Early results from predusk through the nightside in the solar zenith angle range 63 degrees (dusk) to 120 degrees (dawn) reveal that, as on the dayside, the lower nightside ionosphere consists of F(1)and F(2) layers dominated by O(2)(+) and O(+), respectively. Also like the dayside, the nightside composition includes distributions of NO(+), C(+), N(+), H(+), He(+), CO(2)(+), and 28(+) (a combination of CO(+) and N(2)(+)). The surprising abundance of the nightside ionosphere appears to be maintained by the transport of O(+) from the dayside, leading also to the formation of O(2)(+) through charge exchange with CO(2). Above the exobase, the upper nightside ionosphere exhibits dramatic variability in apparent response to variations in the solar wind and interplanetary magnetic field, with the ionopause extending to several thousand kilometers on one orbit, followed by the complete rertnoval of thermal ions to altitudes below 200 kilometers on the succeeding orbit, 24 hours later. In the upper ionosphere, considerable structure is evident in many of the nightside ion profiles. Also evident are horizontal ion drifts with velocities up to the order of 1 kilometer per second. Whereas the duskside ionopause is dominated by O(+) H(+) dominates the topside on the dawnside of the antisolar point, indicating two separate regions for ion depletion in the magnetic tail regions.

  20. Carbon-Isotope Composition of Biochemical Fractions and the Regulation of Carbon Balance in Leaves of the C3-Crassulacean Acid Metabolism Intermediate Clusia minor L. Growing in Trinidad.

    Science.gov (United States)

    Borland, A. M.; Griffiths, H.; Broadmeadow, MSJ.; Fordham, M. C.; Maxwell, C.

    1994-10-01

    Carbon-isotope ratios ([delta]13Cs) were measured for various bio-chemical fractions quantitatively extracted from naturally exposed and shaded leaves of the C3-Crassulacean acid metabolism (CAM) intermediate Clusia minor, sampled at dawn and dusk on days during the wet and dry seasons in Trinidad. As the activity of CAM increased in response to decreased availability of water and higher photon flux density, organic acids and soluble sugars were enriched in 13C by approximately 3.5 to 4%[per mille (thousand) sign] compared to plants sampled during the wet season. The induction of CAM was accompanied by a doubling in size of the reserve carbohydrate pools. Moreover, stoichiometric measurements indicated that degradation of both chloroplastic reserves and soluble sugars were necessary to supply phosphoenolpyruvate for the synthesis of organic acids at night. Results also suggest that two pools of soluble sugars exist in leaves of C. minor that perform CAM, one a vacuolar pool enriched in 13C and the second a transport pool depleted in 13C. Estimates of carbon-isotope discrimination expressed during CAM, derived from the trafficking among inorganic carbon, organic acids, and carbohydrate pools overnight, ranged from 0.9 to 3.1%[per mille (thousand) sign]. The [delta]13C of structural material did not change significantly between wet and dry seasons, indicating that most of the carbon used in growth was derived from C3 carboxylation.

  1. EISCAT observations of plasma patches at sub-auroral cusp latitudes

    Directory of Open Access Journals (Sweden)

    J. Moen

    2006-09-01

    Full Text Available A sequence of 3 patches of high-density (1012 m−3 cold plasma on a horizontal scale-size of 300–700 km was observed near magnetic noon by the EISCAT VHF radar above Svalbard on 17 December 2001. The patches followed a trajectory towards the cusp inflow region. The combination of radar and all-sky observations demonstrates that the patches must have been segmented equatorward of the cusp/cleft auroral display, and hence their properties had not yet been influenced by cusp particle showers and electrodynamics on open flux tubes. The last patch in the sequence was intersected by radio tomography observations, and was found to be located adjacent to a broader region of the same high electron density further south. The patches occurred under moderately active conditions (Kp=3 and the total electron content (TEC of the high-density plasma was 45 TEC units. The train of patches appeared as a segmentation of the tongue of ionization. The sequence of patches occurred in association with a sequence of flow bursts in the dusk cell return flow. It is proposed that reconnection driven pulsed convection is able to create sub-auroral patches in the region where high density mid-latitude plasma is diverted poleward toward the cusp. It is the downward Birkeland current sheet located at the equatorward boundary of the flow disturbance that represents the actual cutting mechanism.

  2. 经纬型智能路灯控制系统%Street Lamp Intelligent Control System Base on Longitude and Latitude

    Institute of Scientific and Technical Information of China (English)

    李社蕾; 王玲玲

    2011-01-01

    An intelligent street lamp control arcuit was designed by taking clock chip DS12887 and microcontroller as a core to make street lamp more energy-efficient. The time of dusk and daybreak is calculated according to the date and the longitude/latitude at which the street lamps are mounted. The time obtained by calculation is set as the alarm of clock chip DS12887. The clock alarm triggers the microcontroller interruption to control the on-off switchs of street lamps. The street lamp intelligent control system can improve the automated management level of street lamps, and make the control of street lamps more timely and reasonable.%为了使路灯照明更加节能、高效,以时钟芯片DS12887和单片机为核心设计智能路灯控制电路,根据日期和路灯所在地的经、纬度,计算出该地当天天黑时间和天亮时间,设定为时钟芯片DS12887的闱铃,以闱铃触发单片机中断,控制路灯天黑而开、天亮而关.该智能路灯控制系统能提高路灯的自动化管理水平,使路灯开关控制更加及时、合理.

  3. Believable Characters

    Science.gov (United States)

    El-Nasr, Magy Seif; Bishko, Leslie; Zammitto, Veronica; Nixon, Michael; Vasiliakos, Athanasios V.; Wei, Huaxin

    The interactive entertainment industry is one of the fastest growing industries in the world. In 1996, the U.S. entertainment software industry reported 2.6 billion in sales revenue, this figure has more than tripled in 2007 yielding 9.5 billion in revenues [1]. In addition, gamers, the target market for interactive entertainment products, are now reaching beyond the traditional 8-34 year old male to include women, Hispanics, and African Americans [2]. This trend has been observed in several markets, including Japan, China, Korea, and India, who has just published their first international AAA title (defined as high quality games with high budget), a 3D third person action game: Ghajini - The Game [3]. The topic of believable characters is becoming a central issue when designing and developing games for today's game industry. While narrative and character were considered secondary to game mechanics, games are currently evolving to integrate characters, narrative, and drama as part of their design. One can see this pattern through the emergence of games like Assassin's Creed (published by Ubisoft 2008), Hotel Dusk (published by Nintendo 2007), and Prince of Persia series (published by Ubisoft), which emphasized character and narrative as part of their design.

  4. Satellite-Based Technologies in Use for Extreme Nocturnal Mountain Rescue Operations: a Synergetic Approach Applying Geophysical Principles

    Science.gov (United States)

    Buchroithner, Manfred F.; Ehlert, Guido; Hetze, Bernd; Kohlschmidt, Horst; Prechtel, Nikolas

    2014-06-01

    Mountain-rescue operations require rapid response whilst also ensuring the security of the rescue teams. Rescuing people in a big rock-face is even more difficult if night or fog prevent sight. The paper presents a technical solution to optimally support, under these aggravated conditions, the location of the casualties and the navigation of the rescue team(s) in a rock-face from a coordination station. In doing so, standard components like a smartphones with GPS functionality, a data communication on a client-server basis and VR visualisation software have been adapted to the specific requirements. Remote support of the navigation in steep rocky terrain requires a highly accurate wall model which permits the local experts of the coordination station to dependably estimate geometry and structure of the rock along the rescue route and to convey necessary directives to the retrieval team. Based on terrestrial laser-scans from different locations, such a model has been generated for the mighty Dachstein South Face (Austria) and texturised with digital photographs. Over a twelve-month period, a transdisciplinary team of the Dresden University of Technology (Informatics, Electrical Engineering, Cartography) developed and integrated the various technical modules of the mountain-rescue support-system (digital rock-face model, optimised GPS data transmission between mobile device, server and client, data filtering, and dynamic visualisation component). In summer 2011 the proper functioning of the prototype was demonstrated in a rescue exercise under foggy dusk conditions.

  5. Day-night variations in malate concentration, osmotic pressure, and hydrostatic pressure in Cereus validus

    Energy Technology Data Exchange (ETDEWEB)

    Luettge, U.; Nobel, P.S.

    1984-07-01

    Malate concentration and stem osmotic pressure concomitantly increase during nighttime CO/sub 2/ fixation and then decrease during the daytime in the obligate Crassulacean acid metabolism (CAM) plant, Cereus validus (Cactaceae). Changes in malate osmotic pressure calculated using the Van't Hoff relation match the changes in stem osmotic pressure, indicating that changes in malate level affected the water relations of the succulent stems. In contrast to stem osmotic pressure, stem water potential showed little day-night changes, suggesting that changes in cellular hydrostatic pressure occurred. This was corroborated by direct measurements of hydrostatic pressure using the Juelich pressure probe where a small oil-filled micropipette is inserted directly into chlorenchyma cells, which indicated a 4-fold increase in hydrostatic pressure from dusk to dawn. A transient increase of hydrostatic pressure at the beginning of the dark period was correlated with a short period of stomatal closing between afternoon and nighttime CO/sub 2/ fixation, suggesting that the rather complex hydrostatic pressure patterns could be explained by an interplay between the effects of transpiration and malate levels. A second CAM plant, Agave deserti, showed similar day-night changes in hydrostatic pressure in its succulent leaves. It is concluded that, in addition to the inverted stomatal rhythm, the oscillations of malate markedly affect osmotic pressures and hence water relations of CAM plants. 13 references, 4 figures.

  6. The sky brightness measurement during the 2016 solar eclipse in Ternate

    Science.gov (United States)

    Pramudya, Yudhiakto; Arkanuddin, Muchlas

    2016-11-01

    Obscuration of the Sun by the Moon during total solar eclipse generates the changing of the sky brightness. Sky Quality Meter (SQM) was employed to measure the sky brightness during the 2016 total solar eclipse. The sky was still bright at the first contact time. It is shown by the SQM value of zero. Approaching the second contact time, the SQM value is rising up started at the value of 5.92 mpsas. The curvature profile of the SQM measurementvalue is similar to the curvature profile of the SQM measurement at the dawn and dusk. However, the flatness part of the curvature is much shorter than night time value of SQM. The maximum of SQM measurement value is lower than the SQM measurement value during the night in Ternate. It is 12.47 mpsas and happened at the maximum phase of the eclipse. It was confirmed by the fact that at the time of totality, the sky close to the horizon was still bright. There is a discrepancy between the predicted and actual second and third contact and maximum eclipse time. By assigning the maximum of SQM measurement value as the reference value of maximum eclipse time, the actual second and third time can be calculated. The shape of curvature between the actual second and third contact time is symmetry.

  7. It's like night and day: Diel net-effects on Cercopagidae densities in the Laurentian Great Lakes

    Science.gov (United States)

    Armenio, Patricia M.; Bunnell, David; Adams, Jean V.; Watson, Nicole M.; Woelmer, Whitney

    2017-01-01

    In the Laurentian Great Lakes, zooplankters are often sampled using standard ≤ 153 μm mesh nets without regard to the time of day they are collected. We sampled Cercopagidae during 2013–2014 in northern Lake Huron during day, dusk, and night using two different nets (a 0.5 m wide 153 μm mesh “standard” net and a 0.75 m wide 285 μm mesh “Bythotrephes” net) to determine if there were any differences in their sampled densities. Bythotrephes densities with the standard net were approximately 2.07-fold greater when captured at night than during the day. No time of day bias occurred with the Bythotrephes net. Nighttime Bythotrephes densities did not differ between the two net types. Cercopagis densities did not vary with net type or the time of day in this study, but future work should revisit this result given our low sample size and the low occurrence of Cercopagis in Lake Huron. To reduce bias and calculate accurate density estimates, Cercopagidae should be sampled at night if using a standard net or any time of day with the Bythotrephes net. Given the large impact of invasive predatory cladocerans Bythotrephes longimanus and Cercopagis pengoi on food webs since their invasion in the Laurentian Great Lakes in the 1980s, proper estimation of their densities is essential.

  8. Scintillation and irregularities from the nightside part of a Sun-aligned polar cap arc

    Science.gov (United States)

    Meeren, Christer; Oksavik, Kjellmar; Lorentzen, Dag A.; Paxton, Larry J.; Clausen, Lasse B. N.

    2016-06-01

    In this paper we study the presence of irregularities and scintillation in relation to the nightside part of a long-lived, Sun-aligned transpolar arc on 15 January 2015. The arc was observed in DMSP UV and particle data and lasted at least 3 h between 1700 and 2000 UT. The arc was more intense than the main oval during this time. From all-sky imagers on Svalbard we were able to study the evolution of the arc, which drifted slowly westward toward the dusk cell. The intensity of the arc as observed from ground was 10-17 kR in 557.7 nm and 2-3.5 kR in 630.0 nm, i.e., significant emissions in both green and red emission lines. We have used high-resolution raw data from global navigation satellite systems (GNSS) receivers and backscatter from Super Dual Auroral Radar Network (SuperDARN) radars to study irregularities and scintillation in relation to the polar cap arc. Even though the literature has suggested that polar cap arcs are potential sources for irregularities, our results indicate only very weak irregularities. This may be due to the background density in the northward IMF polar cap being too low for significant irregularities to be created.

  9. A functional link between rhythmic changes in chromatin structure and the Arabidopsis biological clock.

    Science.gov (United States)

    Perales, Mariano; Más, Paloma

    2007-07-01

    Circadian clocks rhythmically coordinate biological processes in resonance with the environmental cycle. The clock function relies on negative feedback loops that generate 24-h rhythms in multiple outputs. In Arabidopsis thaliana, the clock component TIMING OF CAB EXPRESSION1 (TOC1) integrates the environmental information to coordinate circadian responses. Here, we use chromatin immunoprecipitation as well as physiological and luminescence assays to demonstrate that proper photoperiodic phase of TOC1 expression is important for clock synchronization of plant development with the environment. Our studies show that TOC1 circadian induction is accompanied by clock-controlled cycles of histone acetylation that favor transcriptionally permissive chromatin structures at the TOC1 locus. At dawn, TOC1 repression relies on the in vivo circadian binding of the clock component CIRCADIAN CLOCK ASSOCIATED1 (CCA1), while histone deacetylase activities facilitate the switch to repressive chromatin structures and contribute to the declining phase of TOC1 waveform around dusk. The use of cca1 late elongated hypocotyl double mutant and CCA1-overexpressing plants suggests a highly repressing function of CCA1, antagonizing H3 acetylation to regulate TOC1 mRNA abundance. The chromatin remodeling activities relevant at the TOC1 locus are distinctively modulated by photoperiod, suggesting a mechanism by which the clock sets the phase of physiological and developmental outputs.

  10. STRONG SOLAR WIND DYNAMIC PRESSURE PULSES: INTERPLANETARY SOURCES AND THEIR IMPACTS ON GEOSYNCHRONOUS MAGNETIC FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Zuo, Pingbing; Feng, Xueshang; Wang, Yi [SIGMA Weather Group, State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing (China); Xie, Yanqiong [College of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing (China); Xu, Xiaojun, E-mail: pbzuo@spaceweather.ac.cn, E-mail: fengx@spaceweather.ac.cn [Space Science Institute, Macau University of Science and Technology, Macao (China)

    2015-10-20

    In this investigation, we first present a statistical result of the interplanetary sources of very strong solar wind dynamic pressure pulses (DPPs) detected by WIND during solar cycle 23. It is found that the vast majority of strong DPPs reside within solar wind disturbances. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears to be no systematic investigations on the response of GMFs to negative DPPs. Here, we study both the decompression effects of very strong negative DPPs and the compression from strong positive DPPs on GMFs at different magnetic local time sectors. In response to the decompression of strong negative DPPs, GMFs on the dayside near dawn and near dusk on the nightside, are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of the events when GOES is located at the midnight sector, the GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that under certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here, we find that a stronger pressure enhancement may have a higher probability of producing the exceptional depression of GMF at the midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, which are stronger at the noon sector.

  11. Raman lidar water vapor profiling over Warsaw, Poland

    Science.gov (United States)

    Stachlewska, Iwona S.; Costa-Surós, Montserrat; Althausen, Dietrich

    2017-09-01

    Water vapor mixing ratio and relative humidity profiles were derived from the multi-wavelength Raman PollyXT lidar at the EARLINET site in Warsaw, using the Rayleigh molecular extinction calculation based on atmospheric temperature and pressure from three different sources: i) the standard atmosphere US 62, ii) the Global Data Assimilation System (GDAS) model output, and iii) the WMO 12374 radiosoundings launched at Legionowo. With each method, 136 midnight relative humidity profiles were obtained for lidar observations from July 2013 to August 2015. Comparisons of these profiles showed in favor of the latter method (iii), but it also indicated that the other two data sources could replace it, if necessary. Such use was demonstrated for an automated retrieval of water vapor mixing ratio from dusk until dawn on 19/20 March 2015; a case study related to an advection of biomass burning aerosol from forest fires over Ukraine. Additionally, an algorithm that applies thresholds to the radiosounding relative humidity profiles to estimate macro-physical cloud vertical structure was used for the first time on the Raman lidar relative humidity profiles. The results, based on a subset of 66 profiles, indicate that below 6 km cloud bases/tops can be successfully obtained in 53% and 76% cases from lidar and radiosounding profiles, respectively. Finally, a contribution of the lidar derived mean relative humidity to cloudy conditions within the range of 0.8 to 6.2 km, in comparison to clear-sky conditions, was estimated.

  12. PICARD SODISM, a space telescope to study the Sun from the middle ultraviolet to the near infrared

    CERN Document Server

    Meftah, M; Irbah, A; Hauchecorne, A; Boumier, P; Corbard, T; Turck-Chièze, S; Assus, P; Bertran, E; Bourget, P; Buisson, F; Chaigneau, M; Damé, L; Djafer, D; Dufour, C; Etcheto, P; Ferrero, P; Hersé, M; Marcovici, J -P; Meissonnier, M; Morand, F; Poiet, G; Prado, J -Y; Renaud, C; Rouanet, N; Rouzé, M; Salabert, D; Vieau, A -J

    2013-01-01

    The Solar Diameter Imager and Surface Mapper (SODISM) on board the PICARD space mission provides wide-field images of the photosphere and chromosphere of the Sun in five narrow pass bands (centered at 215.0, 393.37, 535.7, 607.1, and 782.2 nm). PICARD is a space mission, which was successfully launched on 15 June 2010 into a Sun synchronous dawn-dusk orbit. It represents a European asset aiming at collecting solar observations that can serve to estimate some of the inputs to Earth climate models. The scientific payload consists of the SODISM imager and of two radiometers, SOVAP (SOlar VAriability PICARD) and PREMOS (PREcision MOnitor Sensor), which carry out measurements that allow estimating the Total Solar Irradiance (TSI) and the Solar Spectral Irradiance (SSI) from the middle ultraviolet to the red. The SODISM telescope monitors solar activity continuously. It thus produces images that can also feed SSI reconstruction models. Further, the objectives of SODISM encompass the probing of the interior of the S...

  13. Chromatic clocks: Color opponency in non-image-forming visual function.

    Science.gov (United States)

    Spitschan, Manuel; Lucas, Robert J; Brown, Timothy M

    2017-07-01

    During dusk and dawn, the ambient illumination undergoes drastic changes in irradiance (or intensity) and spectrum (or color). While the former is a well-studied factor in synchronizing behavior and physiology to the earth's 24-h rotation, color sensitivity in the regulation of circadian rhythms has not been systematically studied. Drawing on the concept of color opponency, a well-known property of image-forming vision in many vertebrates (including humans), we consider how the spectral shifts during twilight are encoded by a color-opponent sensory system for non-image-forming (NIF) visual functions, including phase shifting and melatonin suppression. We review electrophysiological evidence for color sensitivity in the pineal/parietal organs of fish, amphibians and reptiles, color coding in neurons in the circadian pacemaker in mice as well as sporadic evidence for color sensitivity in NIF visual functions in birds and mammals. Together, these studies suggest that color opponency may be an important modulator of light-driven physiological and behavioral responses. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Quasi-stagnant plasmoid in the middle tail - A new preexpansion phase phenomenon

    Science.gov (United States)

    Nishida, A.; Terasawa, T.; Scholer, M.; Bame, S. J.; Zwickl, R. D.; Gloeckler, G.; Smith, E. J.

    1986-04-01

    From the analysis of ISEE 3 data it is found that a plasmoid is sometimes formed in the middle tail outside the intervals of the substorm expansion phase. This plasmoid is produced by reconnection at the X-type neutral line, which is located earthward of the distant neutral line but beyond the substorm-associated near-tail neutral line, and it is almost stagnant in that the associated flow speed is less than 300 km/s. The blocking effect of the distant neutral line is the most probable reason for the slow movement. The quasi-stagnant plasmoid is observed at x = -60 to - 100 earth radii for a duration of a few tens of minutes, and in about one half of the cases it is followed by the fast tailward streaming. The onset of this streaming tends to coincide with the onset of the substorm expansion phase, and this probably occurs when the reconnection at the middle-tail neutral line comes close to processing the last closed field line. Intensification of the dawn-to-dusk electric field that causes the mantle plasma to reach the plasma sheet boundary closer to the earth is suggested as the reason for the formation of the middle-tail neutral line earthward of the distant neutral line. The effects on the energetic particle flux and relation to the near-tail reconnection are also discussed.

  15. Unusually long lasting multiple penetration of interplanetary electric field to equatorial ionosphere under oscillating IMF Bz

    Science.gov (United States)

    Wei, Yong; Hong, Minghua; Wan, Weixing; Du, Aimin; Lei, Jiuhou; Zhao, Biqiang; Wang, Wenbin; Ren, Zhipeng; Yue, Xinan

    2008-01-01

    During November 11-16, 2003, the interplanetary magnetic field (IMF) B z oscillated between northward and southward directions, which suggests discontinuous magnetic reconnection associated with the multiple pulses-like reconnection electric field. The Jicamarca incoherent scatter radar (ISR) measurements of ionospheric zonal electric field showed similar fluctuations during this period. The high correlation coefficient of 0.71 between the reconnection electric field and equatorial zonal electric field during 125 hours suggests that the interplanetary electric field (IEF) pulsively penetrated into the equatorial ionosphere due to the discontinuous magnetic reconnection. It is implied that the short lifetime (<3 hours) dawn-dusk IEF pulses can penetrate into ionosphere without shielding, in other words, they may exhibit the ``shielding immunity''. The averaged penetration efficiency is about 0.136 and highly local time-dependent. Furthermore, the intense AU and AL indices imply that the multiple electric field penetration is associated with a ``High-Intensity Long-Duration Continuous AE Activity (HILDCAA).''

  16. A circadian gene expression atlas in mammals: implications for biology and medicine.

    Science.gov (United States)

    Zhang, Ray; Lahens, Nicholas F; Ballance, Heather I; Hughes, Michael E; Hogenesch, John B

    2014-11-11

    To characterize the role of the circadian clock in mouse physiology and behavior, we used RNA-seq and DNA arrays to quantify the transcriptomes of 12 mouse organs over time. We found 43% of all protein coding genes showed circadian rhythms in transcription somewhere in the body, largely in an organ-specific manner. In most organs, we noticed the expression of many oscillating genes peaked during transcriptional "rush hours" preceding dawn and dusk. Looking at the genomic landscape of rhythmic genes, we saw that they clustered together, were longer, and had more spliceforms than nonoscillating genes. Systems-level analysis revealed intricate rhythmic orchestration of gene pathways throughout the body. We also found oscillations in the expression of more than 1,000 known and novel noncoding RNAs (ncRNAs). Supporting their potential role in mediating clock function, ncRNAs conserved between mouse and human showed rhythmic expression in similar proportions as protein coding genes. Importantly, we also found that the majority of best-selling drugs and World Health Organization essential medicines directly target the products of rhythmic genes. Many of these drugs have short half-lives and may benefit from timed dosage. In sum, this study highlights critical, systemic, and surprising roles of the mammalian circadian clock and provides a blueprint for advancement in chronotherapy.

  17. Temporal Structure of MeV Electron Precipitation

    Science.gov (United States)

    Millan, R. M.; Lorentzen, K. R.; Lin, R. P.; Smith, D. M.

    2001-12-01

    On January 12, 2000, the MAXIS (MeV Auroral X-ray Imaging and Spectroscopy) long duration balloon experiment was launched from McMurdo, Antarctica carrying x-ray instrumentation designed to search for MeV electron precipitation similar to the event observed in 1996 over Kiruna, Sweden (L=5.8). MAXIS detected seven x-ray bursts with significant flux extending above 0.8 MeV during the 18 day flight in addition to extended periods of softer X-ray activity. These seven events are characterized by an extremely flat spectrum ( ~E-1.7) indicating that the bulk of precipitating electrons producing the x-rays is at relativistic energies. The bursts were detected between magnetic latitudes 58o-67o (corresponding to L-values between 3.8-6.7) with durations varying from several minutes to several hours. The MeV bursts were found to occur preferentially in the late afternoon/dusk sectors (14:30-00:00 MLT) while softer precipitation was detected at all magnetic local times. Two of the strongest MeV events detected by MAXIS show strong modulation of the x-ray count rate at ULF timescales ( ~150 s) similar to modulations observed during the Kiruna event at 100-200 s. We present results from temporal analysis of the MAXIS germanium spectrometer data and examine ground-based and spacecraft observations for evidence of coincident ULF wave activity.

  18. X-ray observations of MeV electron precipitation with a balloon-borne germanium spectrometer

    Science.gov (United States)

    Millan, R. M.; Lin, R. P.; Smith, D. M.; Lorentzen, K. R.; McCarthy, M. P.

    2002-12-01

    The high-resolution germanium detector aboard the MAXIS (MeV Auroral X-ray Imaging and Spectroscopy) balloon payload detected nine X-ray bursts with significant flux extending above 0.5 MeV during an 18 day flight over Antarctica. These minutes-to-hours-long events are characterized by an extremely flat spectrum (~E-2) similar to the first MeV event discovered in 1996, indicating that the bulk of parent precipitating electrons is at relativistic energies. The MeV bursts were detected between magnetic latitudes 58°-68° (L-values of 3.8-6.7) but only in the late afternoon/dusk sectors (14:30-00:00 MLT), suggesting scattering by EMIC (electromagnetic ion cyclotron) waves as a precipitation mechanism. We estimate the average flux of precipitating E >= 0.5 MeV electrons to be ~360 cm-2s-1, corresponding to about 5 × 1025 such electrons precipitated during the eight days at L = 3.8-6.7, compared to ~2 × 1025 trapped 0.5-3.6 MeV electrons estimated from dosimeter measurements on a GPS spacecraft. These observations show that MeV electron precipitation events are a primary loss mechanism for outer zone relativistic electrons.

  19. Behavioral modifications in northern bearded saki monkeys (Chiropotes satanas chiropotes) in forest fragments of central Amazonia.

    Science.gov (United States)

    Boyle, Sarah Ann; Smith, Andrew T

    2010-01-01

    We investigated behavioral differences among seven groups of northern bearded saki monkeys (Chiropotes satanas chiropotes) living in five forest fragments and two areas of continuous forest at the Biological Dynamics of Forest Fragments Project study area, located approximately 80 km north of Manaus, Brazil. We collected data in six research cycles from July-August 2003 to January 2005-April 2006. When bearded saki monkeys were present in a study area, we followed the group from dawn until dusk for three consecutive days. Every 5 min, we conducted behavioral scans of all visible individuals. There was a positive relationship between forest size and group size, but animals in the small forest fragments lived at greater densities. Bearded saki monkeys in the smaller fragments spent more time resting, less time traveling, and less time vocalizing, but there was no relationship between forest size and the amount of time spent feeding. Our results indicate that the main behavioral differences among the groups are related to the amount of forest resources (e.g., fruit trees, space) available to the monkeys in the smaller fragments, as well as the resulting smaller group sizes. We stress the need to preserve large tracts of forest and provide connectivity between forest patches.

  20. Comment on 'Observations of reconnection of interplanetary and lobe magnetic field lines at the high-latitude magnetopause' by J.T. Gosling, M.F. Thomsen, S.J. Bame, R.C. Elphic, and C.T. Russell

    Science.gov (United States)

    Belen'kaia, Elena

    1993-01-01

    Comment is presented on the results of measurements, reported by Gosling et al. (1991), that were made on ISEE in the vicinity of the high-latitude dusk magnetopause near the terminator plane, at a time when the local magnetosheath and tail lobe magnetic fields were nearly oppositely directed. The character of the observed plasma flowing both tailward and sunward within the high-latitude magnetopause current layer presented real evidence for the local reconnection process. Gosling et al. argued that this process may be a manifestation of different global magnetospheric topology structures. In the comment, a global magnetospheric convection pattern is constructed for the northward IMF and for the case of a large azimuthal component of the IMF with small Bz, irrespective of its sign. The suggested scheme provides a simple explanation for the observed sunward convection in the polar caps both for the northward and for strong By with small Bz. According to the present model, for the magnetosheath field at 2300 UT on June 11, 1978, the reconnection between the open field lines appears at the northern neutral point.

  1. Losses of Energetic Electrons in Earth's Outer Radiation Belt During Unusual Coronal Mass Ejections

    Science.gov (United States)

    Lugaz, Noé; Huang, Chia-Lin; Schwadron, Nathan; Spence, Harlan; Farrugia, Charles; Winslow, Reka

    2016-07-01

    The most extreme changes in solar wind parameters important for the coupling between the solar wind and the magnetosphere (dynamic pressure, dawn-to-dusk electric field, Alfven Mach number, plasma beta, …) occur during the passage at Earth of coronal mass ejections (CMEs). While the response of Earth's radiation belts to CMEs and CME-driven shocks has been investigated in great details, few studies have focused on what makes some CMEs and their shocks especially effective in driving losses of energetic electrons in the outer radiation belt. Here, we present specific examples of losses during the passage at Earth of a coronal mass ejection. In particular, we discuss the conditions which may result in the magnetopause to retreat earthward up to geosynchronous orbit, resulting in significant losses of energetic electrons due to magnetopause shadowing. We also present the result of a low-density magnetic ejecta which impacted Earth in January 2013. Combining interplanetary, magnetosheath, outer magnetosphere and radiation belt measurements by more than ten satellites, including the Van Allen Probes, THEMIS and Cluster, we show how a period of extremely low Mach number and dynamic pressure during the passage of the magnetic cloud resulted in dramatic losses in the outer radiation belt and a large-scale reorganization of the entire day-side magnetosphere.

  2. Estimating magnetic field power spectrum using CRRES magnetometer data

    Science.gov (United States)

    Ali, A.; Elkington, S. R.

    2013-05-01

    Radial diffusion is one of the acceleration mechanisms responsible for populating and depleting the Van Allen radiation belts with high energy charged particles. We use the magnetometer data from the Combined Release and Radiation Effects Satellite (CRRES) to estimate the power spectral density in the compressional component of the geomagnetic field in the frequency range of 0.8mHz-16.3mHz. We see a clear dependence of power spectral density on radial distance L, measure of geomagnetic disturbance Kp, and magnetic local time. Comparing total integrated power, the noon sector contains more power with no significant difference between other sectors during periods of low activity. During high activity the dusk sector has significantly more power than dawn sector with the difference sometimes being an order of magnitude higher with power increasing slightly as we move radially outward to higher L-shells. We then recompute the power spectral density without local time dependence and compute the electromagnetic part of the radial diffusion coefficient. The electromagnetic diffusion coefficients are then compared with the electrostatic coefficients computed by Brautigam et al. (2005). The dependence of the diffusion coefficients is then studied on parameters of L, Kp, and the first invariant. For a fixed first invariant the diffusion coefficient can be up to two orders of magnitude higher as we move from the inner magnetosphere (L=3.5) to the outer magnetosphere (L=6.5). During high activity, radial diffusion is also significantly faster than at quiet times.

  3. Mosquito Frequency and Feeding Habits in an Enzootic Canine Dirofilariasis Area in Niterói, State of Rio de Janeiro, Brazil

    Directory of Open Access Journals (Sweden)

    Labarthe Norma

    1998-01-01

    Full Text Available Heartworm, a chronic fatal mosquito-borne canine disease, is frequently diagnosed in dogs from the State of Rio de Janeiro, where its prevalence is 29.7% in the city of Niterói. Nevertheless it is rarely detected in cats (0.8% from the same state. Dogs are the primary source of infection to mosquitoes, because cats either do not demonstrate microfilaremia or it is too low and transient for transmission. A mosquito survey was conducted in Itacoatiara, Niterói, from March 1995 to February 1996, using canine, feline and human baits. A total of 21 mosquito species (3,888 females was collected and biting frequency was highest at dusk. The four species collected most frequently (88.9% were: Aedes taeniorhynchus (30% of the total catch; with the peak in May/June; Culex quinquefasciatus (22.5%; August/October; Aedes scapularis (19.4%; August, October/November and January and Culex declarator (17%; November/January. Human baits were attractive to these species and dogs were significantly more attractive to them than cats. Ae. taeniorhynchus, Cx. quinquefasciatus, Ae. scapularis, Cx. declarator and Cx. nigripalpus are the most likely mosquito species to transmit Dirofilaria immitis parasites to dogs and may transmit the parasite to humans. It is also suggested that the vector to cats belongs to the genus Culex

  4. Crassulacean acid metabolism enhances underwater photosynthesis and diminishes photorespiration in the aquatic plant Isoetes australis.

    Science.gov (United States)

    Pedersen, Ole; Rich, Sarah Meghan; Pulido, Cristina; Cawthray, Gregory Robert; Colmer, Timothy David

    2011-04-01

    • Underwater photosynthesis by aquatic plants is often limited by low availability of CO(2), and photorespiration can be high. Some aquatic plants utilize crassulacean acid metabolism (CAM) photosynthesis. The benefits of CAM for increased underwater photosynthesis and suppression of photorespiration were evaluated for Isoetes australis, a submerged plant that inhabits shallow temporary rock pools. • Leaves high or low in malate were evaluated for underwater net photosynthesis and apparent photorespiration at a range of CO(2) and O(2) concentrations. • CAM activity was indicated by 9.7-fold higher leaf malate at dawn, compared with at dusk, and also by changes in the titratable acidity (μmol H(+) equivalents) of leaves. Leaves high in malate showed not only higher underwater net photosynthesis at low external CO(2) concentrations but also lower apparent photorespiration. Suppression by CAM of apparent photorespiration was evident at a range of O(2) concentrations, including values below air equilibrium. At a high O(2) concentration of 2.2-fold the atmospheric equilibrium concentration, net photosynthesis was reduced substantially and, although it remained positive in leaves containing high malate concentrations, it became negative in those low in malate. • CAM in aquatic plants enables higher rates of underwater net photosynthesis over large O(2) and CO(2) concentration ranges in floodwaters, via increased CO(2) fixation and suppression of photorespiration.

  5. MESSENGER observations of energetic electron acceleration in Mercury's magnetotail

    Science.gov (United States)

    Dewey, Ryan; Slavin, James A.; Baker, Daniel; Raines, Jim; Lawrence, David

    2016-10-01

    Energetic particle bursts within Mercury's magnetosphere have been a source of curiosity and controversy since Mariner 10's flybys. Unfortunately, instrumental effects prevent an unambiguous determination of species, flux, and energy spectrum for the Mariner 10 events. MESSENGER data taken by the Energetic Particle Spectrometer (EPS) have now shown that these energetic particle bursts are composed entirely of electrons. EPS made directional measurements of these electrons from ~30 to 300 keV at 3 s resolution, and while the energy of these electrons sometimes exceeded 200 keV, the energy distributions usually exhibited a cutoff near 100 keV. The Gamma Ray Spectrometer (GRS) has also provided measurements of these electron events, at higher time resolution (10 ms) and energetic threshold (> 50 keV) compared to EPS. We focus on GRS electron events near the plasma sheet in Mercury's magnetotail to identify reconnection-associated acceleration mechanisms. We present observations of acceleration associated with dipolarization events (betratron acceleration), flux ropes (Fermi acceleration), and tail loading/unloading (X-line acceleration). We find that the most common source of energetic electron events in Mercury's magnetosphere are dipolarization events similar to those first observed by Mariner 10. Further, a significant dawn-dusk asymmetry is found with dipolarization-associated energetic particle bursts being more common on the dawn side of the magnetotail.

  6. TIME FOR COFFEE controls root meristem size by changes in auxin accumulation in Arabidopsis.

    Science.gov (United States)

    Hong, Li-Wei; Yan, Da-Wei; Liu, Wen-Cheng; Chen, Hong-Guo; Lu, Ying-Tang

    2014-01-01

    Roots play important roles in plant survival and productivity as they not only anchor the plants in the soil but are also the primary organ for the uptake of nutrients from the outside. The growth and development of roots depend on the specification and maintenance of the root meristem. Here, we report a previously unknown role of TIME FOR COFFEE (TIC) in controlling root meristem size in Arabidopsis. The results showed that loss of function of TIC reduced root meristem length and cell number by decreasing the competence of meristematic cells to divide. This was due to the repressed expression of PIN genes for decreased acropetal auxin transport in tic-2, leading to low auxin accumulation in the roots responsible for reduced root meristem, which was verified by exogenous application of indole-3-acetic acid. Downregulated expression of PLETHORA1 (PLT1) and PLT2, key transcription factors in mediating the patterning of the root stem cell niche, was also assayed in tic-2. Similar results were obtained with tic-2 and wild-type plants at either dawn or dusk. We also suggested that the MYC2-mediated jasmonic acid signalling pathway may not be involved in the regulation of TIC in controlling the root meristem. Taken together, these results suggest that TIC functions in an auxin-PLTs loop for maintenance of post-embryonic root meristem.

  7. The effect of Ramadan fasting on thyroid hormones in 9‐13 years old pre‐menarche girls

    Directory of Open Access Journals (Sweden)

    Shohereh Bahrayni

    2013-12-01

    Full Text Available Introduction: Muslims fast from dawn to dusk during Ramadan. The effects of prolonged food deprivation on endocrine hormones have been studied in healthy adults but no previous study has investigated this effect on children. This study aimed to evaluate the feasible changes in serum level of thyroxin (T3, tetraiodothyronin (T4, thyroid stimulating hormone (TSH and body composition in pre-menarche girls. Methods: This cohort study was performed through Ramadan 2012. We enrolled fifty-eight 9-13years old girls (weight 34.20±7.96 kg, height 142.01±7.76 cm in two groups from (31  and 27 in fasted and non-fasted groups, respectively prior to Ramadan until afterwards. Weight and height of the subjects were measured using standard methods, and then Body Mass Index (BMI was calculated.  Body composition was measured using Bio Impedance Analyzer (BIA method.  Serum concentrations of T3, T4 and TSH hormones were measured by Radio Immunoassay (RIA. Paired t-test was used to compare result of each group before and after Ramadan. Independent t-test was used to compare two groups together. Tanner intervention variable was controlled by generalized linear models intervening test. SPSS.11 software was used for data analysis. Results: Ramadan fasting induces a significant decrease in BMI and weight on fasted group (p=0.005, p=0.044, respectively while a significant increase was observed in non-fasted group (p

  8. Circadian entrainment and its role in depression: a mechanistic review.

    Science.gov (United States)

    Lall, G S; Atkinson, L A; Corlett, S A; Broadbridge, P J; Bonsall, D R

    2012-10-01

    The natural rotation of the earth generates an environmental day-night cycle that repeats every 24 h. This daily transition from dawn to dusk provides one of the most important time cues to which the majority of organisms synchronise their activity. Under these conditions, natural light, a photic stimulus, provides the principal entraining cue. In mammals, an endogenous circadian pacemaker located within the suprachiasmatic nucleus (SCN) of the hypothalamus acts as a coordinating centre to align physiological activity with the environmental light-dark cycle. However, the SCN also receives regulatory input from a number of behavioural, non-photic, cues such as physical activity, social interactions and feeding routines. The unique ability of the SCN to integrate both photic and non-photic cues allows it to generate a rhythm that is tailored to the individual and entrained to the environment. Here, we review the key neurotransmitter systems involved in both photic and non-photic transmission to the SCN and their interactions that assist in generating an entrained output rhythm. We also consider the impact on health of a desynchronised circadian system with a focus on depressive affective disorders and current therapies aimed at manipulating the relationship between photic and non-photic SCN regulators.

  9. Observations of the Early Evening Boundary-Layer Transition Using a Small Unmanned Aerial System

    Science.gov (United States)

    Bonin, Timothy; Chilson, Phillip; Zielke, Brett; Fedorovich, Evgeni

    2013-01-01

    The evolution of the lower portion of the planetary boundary layer is investigated using the Small Multifunction Research and Teaching Sonde (SMARTSonde), an unmanned aerial vehicle developed at the University of Oklahoma. The study focuses on the lowest 200 m of the atmosphere, where the most noticeable thermodynamic changes occur during the day. Between October 2010 and February 2011, a series of flights was conducted during the evening hours on several days to examine the vertical structure of the lower boundary layer. Data from a nearby Oklahoma Mesonet tower was used to supplement the vertical profiles of temperature, humidity, and pressure, which were collected approximately every 30 min, starting 2 h before sunset and continuing until dusk. From the profiles, sensible and latent heat fluxes were estimated. These fluxes were used to diagnose the portion of the boundary layer that was most affected by the early evening transition. During the transition period, a shallow cool and moist layer near the ground was formed, and as the evening progressed the cooling affected an increasingly shallower layer just above the surface.

  10. Cusp currents from ionospheric vorticity generated by gasdynamic and merging flow fields at the magnetopause

    Energy Technology Data Exchange (ETDEWEB)

    Mie, Y. [Univ. of California, Los Angeles, CA (United States); Crooker, N.U.; Siscoe, G.L. [Boston Univ., MA (United States)

    1995-05-01

    Cusp currents that arise from ionospheric vorticity generated by the combined merging outflow and gasdynamic flow fields at the magnetopause are quantified and compared with those calculated from vorticity generated by mapping the solar wind electric field into a limited cusp region of the polar cap, as proposed in the synthesis view of Banks. The results are essentially identical for strong interplanetary magnetic field (IMF) B{sub Y}, thus demonstrating equivalence between mechanical and electrical descriptions of reconnection-driven convection. For southward IMF, however, the mechanical description yields weak cusp currents with dawn-dusk bipolarity, as deduced from early observations by Iijima and Potemra, whereas the electrical description yields none. The bipolar currents arise from the diverging pattern of gasdynamic flow. The currents become unipolar as B{sub Y} increases and the asymmetry of the merging outflow dominates. Additional cusp currents in both models arise at kinks in the flow contours (additional ionospheric vorticity) around the border of the cusp region, owing to limiting the area of mapping from the magnetopause. The border currents form a bipolar pair that rotates around the circumference of the cusp as the IMF rotates in clock angle. They dominate the currents arising from vorticity within the cusp. 17 refs., 3 figs.

  11. System Science Tool for the Statistical Mapping of the Solar Wind - Magnetosheath - Magnetospheric System

    Science.gov (United States)

    Dimmock, A. P.; Nykyri, K.; Pulkkinen, T. I.; Osmane, A.

    2014-12-01

    The magnetosheath (MS) acts as a natural interface between the solar wind (SW) and magnetospheric (MSP) plasma and is therefore a key element in studying the driving of plasma properties in the inner MSP. However, understanding the behaviour of MS plasma properties due to the rapidly changing upstream conditions is no trivial matter and to date is not completely understood. Since the MS is situated between two very dynamic boundaries which respond directly to SW variations, their motion is significant to the order of several Earth radii. The combination of the spatial boundary variations and the non uniform nature of the SW not only make the compilation of statistical data problematic, but their interpretation is by no means straightforward. As a result, it is very difficult to build a complete picture of the global SW - MS - MSP system which accounts for upstream variations outside of the simulated environment. In the present study, we describe a statistical mapping methodology aimed at overcoming such difficulties. Our tool compiles statistical datasets for the MS and MSP in a normalised frame accounting for boundary motion, upstream SW variations and planetary aberration. We use THEMIS measurements for MS and MSP data whereas upstream estimates are provided by the OMNI database. Multiple datasets are compiled to produce statistical maps of the MS and MSP system and also to perform numerical analysis of the properties in each region. We use this methodology to study the presence of dawn/dusk asymmetries and their dependence on upstream conditions.

  12. Bio-Inspired Vision-Based Leader-Follower Formation Flying in the Presence of Delays

    Directory of Open Access Journals (Sweden)

    John Oyekan

    2016-08-01

    Full Text Available Flocking starlings at dusk are known for the mesmerizing and intricate shapes they generate, as well as how fluid these shapes change. They seem to do this effortlessly. Real-life vision-based flocking has not been achieved in micro-UAVs (micro Unmanned Aerial Vehicles to date. Towards this goal, we make three contributions in this paper: (i we used a computational approach to develop a bio-inspired architecture for vision-based Leader-Follower formation flying on two micro-UAVs. We believe that the minimal computational cost of the resulting algorithm makes it suitable for object detection and tracking during high-speed flocking; (ii we show that provided delays in the control loop of a micro-UAV are below a critical value, Kalman filter-based estimation algorithms are not required to achieve Leader-Follower formation flying; (iii unlike previous approaches, we do not use external observers, such as GPS signals or synchronized communication with flock members. These three contributions could be useful in achieving vision-based flocking in GPS-denied environments on computationally-limited agents.

  13. Scintillation and irregularities from the nightside part of a Sun-aligned polar cap arc

    CERN Document Server

    van der Meeren, Christer; Lorentzen, Dag A; Paxton, Larry J; Clausen, Lasse B N

    2016-01-01

    In this paper we study the presence of irregularities and scintillation in relation to the nightside part of a long-lived, Sun-aligned transpolar arc on 15 January 2015. The arc was observed in DMSP UV and particle data and lasted at least 3 h between 1700 and 2000 UT. The arc was more intense than the main oval during this time. From all-sky imagers on Svalbard we were able to study the evolution of the arc, which drifted slowly westward toward the dusk cell. The intensity of the arc as observed from ground was 10-17 kR in 557.7 nm and 2-3.5 kR in 630.0 nm, i.e., significant emissions in both green and red emission lines. We have used high-resolution raw data from global navigation satellite systems (GNSS) receivers and backscatter from Super Dual Auroral Radar Network (SuperDARN) radars to study irregularities and scintillation in relation to the polar cap arc. Even though the literature has suggested that polar cap arcs are potential sources for irregularities, our results indicate only very weak irregular...

  14. GIGANTEA and EARLY FLOWERING 4 in Arabidopsis Exhibit Differential Phase-Specific Genetic Influences over a Diurnal Cycle

    Institute of Scientific and Technical Information of China (English)

    Yumi Kim; Miji Yeom; Hyunmin Kim; Junhyun Lim; HeeJung Koo; Daehee Hwang; David Somers; Hong Gil Nam

    2012-01-01

    The endogenous circadian clock regulates many physiological processes related to plant survival and adaptability.GIGANTEA (GI),a clock-associated protein,contributes to the maintenance of circadian period length and amplitude,and also regulates flowering time and hypocotyl growth in response to day length.Similarly,EARLY FLOWERING 4 (ELF4),another clock regulator,also contributes to these processes.However,little is known about either the genetic or molecular interactions between GI and ELF4 in Arabidopsis.In this study,we investigated the genetic interactions between GI and ELF4 in the regulation of circadian clock-controlled outputs.Our mutant analysis shows that GI is epistatic to ELF4 in flowering time determination,while ELF4 is epistatic to GI in hypocotyl growth regulation.Moreover,GI and ELF4 have a synergistic or additive effect on endogenous clock regulation.Gene expression profiling of gi,elf4,and gi elf4 mutants further established that Gland ELF4 have differentially dominant influences on circadian physiological outputs at dusk and dawn,respectively.This phasing of GI and ELF4 influences provides a potential means to achieve diversity in the regulation of circadian physiological outputs,including flowering time and hypocotyl growth.

  15. The circadian clock has transient plasticity of period and is required for timing of nocturnal processes in Arabidopsis.

    Science.gov (United States)

    Dodd, Antony N; Dalchau, Neil; Gardner, Michael J; Baek, Seong-Jin; Webb, Alex A R

    2014-01-01

    A circadian rhythm matched to the phase and period of the day-night cycle has measurable benefits for land plants. We assessed the contribution of circadian period to the phasing of cellular events with the light : dark cycle. We also investigated the plasticity of circadian period within the Arabidopsis circadian oscillator. We monitored the circadian oscillator in wild-type and circadian period mutants under light : dark cycles of varying total duration. We also investigated changes in oscillator dynamics during and after the transition from light : dark cycles to free running conditions. Under light : dark cycles, dawn and dusk were anticipated differently when the circadian period was not resonant with the environmental period ('T cycle'). Entrainment to T cycles differing from the free-running period caused a short-term alteration in oscillator period. The transient plasticity of period was described by existing mathematical models of the Arabidopsis circadian network. We conclude that a circadian period resonant with the period of the environment is particularly important for anticipation of dawn and the timing of nocturnal events; and there is short-term and transient plasticity of period of the Arabidopsis circadian network.

  16. Behavior of dusky dolphins foraging on the deep-scattering layer in Kaikoura Canyon, New Zealand

    Science.gov (United States)

    Benoit-Bird, Kelly; Wursig, Bernd; McFadden, Cynthia

    2003-04-01

    Little is known of foraging habits of sound-scattering layer consumers. A 200-kHz echosounder was used to survey dusky dolphins and the sound-scattering layer in winter 2002, in Kaikoura Canyon, New Zealand. Visual observations of dolphin surfacings occurred 84% of the time that dolphins were acoustically detected, confirming identifications from the acoustic data. Dusky dolphins were within the layer at 2000 h (about 1.5 h after dusk), within 125 m of the surface. As the layer rose to within 30 m of the surface at 0100 h, the observed depth of dolphins decreased presumably as the dolphins followed the vertical migration of their prey. The mean depth of dolphins was within the scattering layer except when the top of the layer was deeper than 125 m. Dusky dolphins often forage within large groups. Acoustically identified subgroups of coordinated animals ranged from 1 to 5 dolphins. Subgroup size varied with time of night, minimum depth of the scattering layer, and the variance of the food resource. The largest subgroups occurred when the scattering layer was closest to the surface, and when the layer was most heterogeneous. Time, depth of layer, and layer variance contributed significantly to predicting foraging dusky dolphin subgroup size.

  17. Some Ecological and Behavioral Aspects of the Tomato Leaf Miner Tuta absoluta (Meyrick (Lepidoptera: Gelechiidae

    Directory of Open Access Journals (Sweden)

    Hussein Samir Abd El-Rahman Salama

    2015-12-01

    Full Text Available Preliminary investigations were carried out to determine the insect behavior of Tuta absoluta towards different factors. Observations showed that the moth is nocturnal in habits. It is most active at dusk and dawn and rest among leaves of the host plant during the day, showing greater morning-crepuscular activity. It prefers to infest leaves of its host plants followed by sepals, leaf neck and stem. Also, the apical part of the tested plants showed to be more attractive to the females‘ oviposition compared to the median and basal parts. The best time for mating started in the morning. The insect can discriminate between different host plants. It showed more preference to tomato followed by black nightshade, eggplant, potato and pepper. The larvae are sensitive to light and it prefers the dark zones. The larvae with its taste receptors are able to discriminate between host plants and other chemicals. For instance, it showed great sensitivity to various sugars in varying degrees. The flight range of the moth was determined and it showed the ability to fly for a distance of 0.4 km overnight.

  18. Beyond the average: Diverse individual migration patterns in a population of mesopelagic jellyfish

    KAUST Repository

    Kaartvedt, Stein

    2011-11-01

    We examined the diel behavior among the jellyfish Periphylla periphylla in Lurefjorden, Norway in a sampling campaign and by a > 3-month continuous acoustic study. Jellyfish distribution and behavior were recorded by an upward-facing, bottom-mounted echo sounder at 280-m depth. The population was typically divided into four groups, each with different behavior. Individuals of behavioral Mode 1 undertook synchronous diel vertical migrations (DVM) within the upper 100 m. Individuals of behavioral Mode 2, stayed at ~ 160-200-m depth during the day, and also exhibited synchronized DVM, ascending at dusk and descending at dawn. The smaller individuals of behavioral Mode 3 swam continuously up and down throughout both day and night, yet occurred below Mode 2 individuals in daytime (~ 200 m-bottom), while their vertical range encompassed the entire water column during night. Mode 4 behavior was displayed by large jellyfish located between ~ 130 m and the bottom. These animals shifted between remaining motionless and relocating in rapid steps during both day and night. These four main behavioral patterns persisted throughout the registration period, although the synchronously migrating Mode 2 behavior became weaker in spring. This acoustic study has unveiled more diverse migration behaviors than previously derived from net sampling and remote-operated vehicles methods and emphasizes the importance of studying individuals. DVM is complex because individuals in a plankton population may simultaneously engage in a range of various contrasting behaviors.

  19. Vocalisation Repertoire of Female Bluefin Gurnard (Chelidonichthys kumu in Captivity: Sound Structure, Context and Vocal Activity.

    Directory of Open Access Journals (Sweden)

    Craig A Radford

    Full Text Available Fish vocalisation is often a major component of underwater soundscapes. Therefore, interpretation of these soundscapes requires an understanding of the vocalisation characteristics of common soniferous fish species. This study of captive female bluefin gurnard, Chelidonichthys kumu, aims to formally characterise their vocalisation sounds and daily pattern of sound production. Four types of sound were produced and characterised, twice as many as previously reported in this species. These sounds fit two aural categories; grunt and growl, the mean peak frequencies for which ranged between 129 to 215 Hz. This species vocalized throughout the 24 hour period at an average rate of (18.5 ± 2.0 sounds fish-1 h-1 with an increase in vocalization rate at dawn and dusk. Competitive feeding did not elevate vocalisation as has been found in other gurnard species. Bluefin gurnard are common in coastal waters of New Zealand, Australia and Japan and, given their vocalization rate, are likely to be significant contributors to ambient underwater soundscape in these areas.

  20. Vocalisation Repertoire of Female Bluefin Gurnard (Chelidonichthys kumu) in Captivity: Sound Structure, Context and Vocal Activity.

    Science.gov (United States)

    Radford, Craig A; Ghazali, Shahriman M; Montgomery, John C; Jeffs, Andrew G

    2016-01-01

    Fish vocalisation is often a major component of underwater soundscapes. Therefore, interpretation of these soundscapes requires an understanding of the vocalisation characteristics of common soniferous fish species. This study of captive female bluefin gurnard, Chelidonichthys kumu, aims to formally characterise their vocalisation sounds and daily pattern of sound production. Four types of sound were produced and characterised, twice as many as previously reported in this species. These sounds fit two aural categories; grunt and growl, the mean peak frequencies for which ranged between 129 to 215 Hz. This species vocalized throughout the 24 hour period at an average rate of (18.5 ± 2.0 sounds fish-1 h-1) with an increase in vocalization rate at dawn and dusk. Competitive feeding did not elevate vocalisation as has been found in other gurnard species. Bluefin gurnard are common in coastal waters of New Zealand, Australia and Japan and, given their vocalization rate, are likely to be significant contributors to ambient underwater soundscape in these areas.

  1. It’s not black or white - on the range of vision and echolocation in echolocating bats

    Directory of Open Access Journals (Sweden)

    Arjan eBoonman

    2013-09-01

    Full Text Available Around 1000 species of bats in the world use echolocation to navigate, orient and detect insect prey. Many of these bats emerge from their roost at dusk and start foraging when there is still light available. It is however unclear in what way and to which extent navigation, or even prey detection in these bats is aided by vision. Here we compare the echolocation and visual detection ranges of two such species of bats which rely on different foraging strategies (Rhinopoma microphyllum and Pipistrellus kuhlii. We find that echolocation is better than vision for detecting small insects even in intermediate light levels (1-10lux, while vision is advantageous for monitoring far-away landscape elements in both species. We thus hypothesize that, bats constantly integrate information acquired by the two sensory modalities. We suggest that during evolution, echolocation was refined to detect increasingly small targets in conjunction with using vision. To do so, the ability to hear ultrasonic sound is a prerequisite which was readily available in small mammals, but absent in many other animal groups. The ability to exploit ultrasound to detect very small targets, such as insects, has opened up a large nocturnal niche to bats and may have spurred diversification in both echolocation and foraging tactics.

  2. The evolution of irradiance detection: melanopsin and the non-visual opsins.

    Science.gov (United States)

    Peirson, Stuart N; Halford, Stephanie; Foster, Russell G

    2009-10-12

    Circadian rhythms are endogenous 24 h cycles that persist in the absence of external time cues. These rhythms provide an internal representation of day length and optimize physiology and behaviour to the varying demands of the solar cycle. These clocks require daily adjustment to local time and the primary time cue (zeitgeber) used by most vertebrates is the daily change in the amount of environmental light (irradiance) at dawn and dusk, a process termed photoentrainment. Attempts to understand the photoreceptor mechanisms mediating non-image-forming responses to light, such as photoentrainment, have resulted in the discovery of a remarkable array of different photoreceptors and photopigment families, all of which appear to use a basic opsin/vitamin A-based photopigment biochemistry. In non-mammalian vertebrates, specialized photoreceptors are located within the pineal complex, deep brain and dermal melanophores. There is also strong evidence in fish and amphibians for the direct photic regulation of circadian clocks in multiple tissues. By contrast, mammals possess only ocular photoreceptors. However, in addition to the image-forming rods and cones of the retina, there exists a third photoreceptor system based on a subset of melanopsin-expressing photosensitive retinal ganglion cells (pRGCs). In this review, we discuss the range of vertebrate photoreceptors and their opsin photopigments, describe the melanopsin/pRGC system in some detail and then finally consider the molecular evolution and sensory ecology of these non-image-forming photoreceptor systems.

  3. Development of a tiny tandem balloon system for atmospheric observation

    Science.gov (United States)

    Saito, Yoshitaka; Yamada, Kazuhiko; Fujiwara, Masatomo

    2016-07-01

    A tandem balloon system with a combination of a zero-pressure balloon on top and a super-pressure balloon on the bottom has a unique trajectory characteristic, with different flight altitudes between day and night and thus with ascending and descending motions at dawn and dusk, respectively. This characteristic provides a unique opportunity to explore the atmosphere, e.g., the upper tropospheric and lower stratospheric region with cross-tropopause measurements twice a day. We started development of a tiny tandem balloon system using a 10 m^{3} super-pressure balloon and a 100 m^{3} zero-pressure balloon, with a capability of carrying 3 kg of payload. One of the scientific targets is to measure water vapor, cloud particles, and temperature around the tropical tropopause which is the entry point of the stratospheric and mesospheric meridional circulation. For the data transfer, the iridium satellite communication module, SBD9603 is used. In this paper, the current status of the development will be reported.

  4. Effects of The Encounter of A Solar Energetic Particle Event With Mercury

    Science.gov (United States)

    Leblanc, F.; Luhmann, J. G.; Johnson, R. E.; Chassefiere, E.

    In this work, we use a typical Solar Energetic Particles event observed at the Earth orbit and scaled to Mercury's orbit. We follow these energetic particles inside the Hermean magnetosphere. The model for the magnetosphere is deduced from Tsyga- nenko's Earth model (Tsyganenko, JGR 1996) extrapolated to Mercury following the measurements of the Hermean magnetosphere made by Mariner 10 (Luhmann et al., JGR 1998). For each of the four main species of ions which usually composed a SEP event, that is H+, He2+, O7+ and C6+, and for the electrons we follow inside the Her- mean magnetosphere thousands of particles launched from the magnetopause as far as either they leave the Hermean magnetosphere or reach the Hermean surface. From this calculation, we deduce the lifetime of these particles inside the magnetosphere and therefore confirm the existence of transfer radial ion and electron pockets (Luh- mann DPS 2001). We also estimate the flux of energetic particles reaching the surface in particular with respect to the Interplanetary Magnetic Field. We then calculate the importance of such encounter among the processes which contribute to generate the Hermean sodium neutral exosphere (Potter et al. 1986). We show in particular that most of the unexplained casual characteristics of this exosphere - peaks of emission on North and South daylight hemispheres (Killen et al. JGR 2001) and dawn/dusk asymmetries (Sprague et al. JGR 1998) - can be explained by such a type of encounter.

  5. He Bulge Detection by MAVEN Neutral Gas and Ion Mass Spectrometer (NGIMS) in the Upper Atmosphere of Mars

    Science.gov (United States)

    Elrod, Meredith; Bougher, Stephen; Benna, Mehdi; Yelle, Roger; Jakosky, Bruce; Bell, Jared; Mahaffy, Paul; Stone, Shane

    2016-07-01

    Studies of the Venusian atmospheres have demonstrated enhanced He densities at high latitudes and on the night-side detections. To determine if Mars has a similar enhanced He 'bulge' in the same region, we compared several periapsis passes from night to dayside. The first six weeks of the MAVEN prime mission had periapsis at high latitudes on the night-side, followed by the next three months at mid latitudes on the dayside moving to low latitudes on the night-side. In addition to its normal orbit, which has a periapsis of approximately 150 km, MAVEN conducts a few deep dip orbits where the spacecraft has a periapsis closer to 125km. The first deep dip was at dusk at mid latitudes, the second at noon at the equator, with the third going from dawn to night in the southern hemisphere. Initial analysis of the Neutral Gas and Ion Mass Spectrometer (NGIMS) closed source data from all orbits with good pointing revealed an enhanced He density on the night-side orbits and a decreased He density on the dayside. This enhancement of He demonstrates a bulge at Mars that will continue to be explored over the course of the mission.

  6. Seasonal variation of temporal niche in wild owl monkeys (Aotus azarai azarai) of the Argentinean Chaco: a matter of masking?

    Science.gov (United States)

    Erkert, Hans G; Fernandez-Duque, Eduardo; Rotundo, Marcelo; Scheideler, Angelika

    2012-07-01

    Among the more than 40 genera of anthropoid primates (monkeys, apes, and humans), only the South American owl monkeys, genus Aotus, are nocturnal. However, the southernmostly distributed species, Aotus azarai azarai, of the Gran Chaco may show considerable amounts of its 24-h activity during bright daylight. Due to seasonal changes in the duration of photophase and climatic parameters in their subtropical habitat, the timing and pattern of their daily activity are expected to show significant seasonal variation. By quantitative long-term activity recordings with Actiwatch AW4 accelerometer data logger devices of 10 wild owl monkeys inhabiting a gallery forest in Formosa, Argentina, the authors analyzed the seasonal variation in the temporal niche and activity pattern resulting from entrainment and masking of the circadian activity rhythm by seasonally and diurnally varying environmental factors. The owl monkeys always displayed a distinct bimodal activity pattern, with prominent activity bouts and peaks during dusk and dawn. Their activity rhythm showed distinct lunar and seasonal variations in the timing and daily pattern. During the summer, the monkeys showed predominantly crepuscular/nocturnal behavior, and a crepuscular/cathemeral activity pattern with similar diurnal and nocturnal activity levels during the cold winter months. The peak times of the evening and morning activity bouts were more closely related to the times of sunset and sunrise, respectively, than activity-onset and -offset. Obviously, they were better circadian markers for the phase position of the entrained activity rhythm than activity-onset and -offset, which were subject to more masking effects of environmental and/or internal factors. Total daily activity was lowest during the two coldest lunar months, and almost twice as high during the warmest months. Nighttime (21:00-06:00 h) and daytime (09:00-18:00 h) activity varied significantly across the year, but in an opposite manner. Highest

  7. Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals

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    Y. I. Feldstein

    2006-09-01

    Full Text Available We investigate variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. Special attention was paid to the complex structure of the electrojets and their interrelationship with diffuse and discrete particle precipitation and field-aligned currents in the dusk sector. During magnetospheric substorms the eastward electrojet (EE location in the evening sector changes with local time from cusp latitudes (Φ~77° during early afternoon to latitudes of diffuse auroral precipitation (Φ~65° equatorward of the auroral oval before midnight. During the main phase of an intense magnetic storm the eastward currents in the noon-early evening sector adjoin to the cusp at Φ~65° and in the pre-midnight sector are located at subauroral latitude Φ~57°. The westward electrojet (WE is located along the auroral oval from evening through night to the morning sector and adjoins to the polar electrojet (PE located at cusp latitudes in the dayside sector. The integrated values of the eastward (westward equivalent ionospheric current during the intense substorm are ~0.5 MA (~1.5 MA, whereas they are 0.7 MA (3.0 MA during the storm main phase maximum. The latitudes of auroral particle precipitation in the dusk sector are identical with those of both electrojets. The EE in the evening sector is accompanied by particle precipitation mainly from the Alfvén layer but also from the near-Earth part of the central plasma sheet. In the lower-latitude part of the EE the field-aligned currents (FACs flow into the ionosphere (Region 2 FAC, and at its higher-latitude part the FACs flow out of the ionosphere (Region 1 FAC. During intense disturbances, in addition to the Region 2 FAC and the Region 1 FAC, a Region 3 FAC with the downward current was identified. This FAC is accompanied by diffuse

  8. Structure of the auroral precipitation region in the dawn sector: relationship to convection reversal boundaries and field-aligned currents

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    electrons and isotropic ion precipitation (AO is mapped to the dawn periphery of the Central Plasma Sheet (CPS; the soft small scale structured precipitation (SSSL is mapped to the outer magnetosphere close to the magnetopause, i.e. the Low Latitude Boundary Layer (LLBL. In the near-noon sector, earthward fluxes of soft electrons, which cause the Diffuse Red Aurora (DRA, are observed. The ion energies decrease with increasing latitude. The plasma spectra of the DRA regime are analogous to the spectra of the Plasma Mantle (PM. In the dawn sector, the large-scale field-aligned currents flow into the ionosphere at the SSSL latitudes (Region 1 and flow out at the AO or DAZ latitudes (Region 2. In the dawn and dusk sectors, the large-scale Region 1 and Region 2 FAC generation occurs in different plasma domains of the distant magnetosphere. The dawn and dusk FAC connection to the traditional Region 1 and Region 2 has only formal character, as FAC generating in various magnetospheric plasma domains integrate in the same region (Region 1 or Region 2. In the SSSL, there is anti-sunward convection; in the DAZ and the AO, there is the sunward convection. At PM latitudes, the convection is controlled by the azimuthal IMF component (By . It is suggested to extend the notation of the plasma pattern boundaries, as proposed by Newell et al. (1996, for the nightside sector of the auroral oval to the dawn sector.

    Key words. Magnetospheric physics (current systems; magnetospheric configuration and dynamics; plasma convection

  9. Large enhancements in low latitude total electron content during 15 May 2005 geomagnetic storm in Indian zone

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    N. Dashora

    2009-05-01

    Full Text Available Results pertaining to the response of the equatorial and low latitude ionosphere to a major geomagnetic storm that occurred on 15 May 2005 are presented. These results are also the first from the Indian zone in terms of (i GPS derived total electron content (TEC variations following the storm (ii Local low latitude electrodynamics response to penetration of high latitude convection electric field (iii effect of storm induced traveling atmospheric disturbances (TAD's on GPS-TEC in equatorial ionization anomaly (EIA zone.

    Data set comprising of ionospheric TEC obtained from GPS measurements, ionograms from an EIA zone station, New Delhi (Geog. Lat. 28.42° N, Geog. Long. 77.21° E, ground based magnetometers in equatorial and low latitude stations and solar wind data obtained from Advanced Composition Explorer (ACE has been used in the present study. GPS receivers located at Udaipur (Geog. Lat. 24.73° N, Geog. Long. 73.73° E and Hyderabad (Geog. Lat. 17.33° N, Geog. Long. 78.47° E have been used for wider spatial coverage in the Indian zone. Storm induced features in vertical TEC (VTEC have been obtained comparing them with the mean VTEC of quiet days. Variations in solar wind parameters, as obtained from ACE and in the SYM-H index, indicate that the storm commenced on 15 May 2005 at 02:39 UT. The main phase of the storm commenced at 06:00 UT on 15 May with a sudden southward turning of the Z-component of interplanetary magnetic field (IMF-Bz and subsequent decrease in SYM-H index. The dawn-to-dusk convection electric field of high latitude origin penetrated to low and equatorial latitudes simultaneously as corroborated by the magnetometer data from the Indian zone. Subsequent northward turning of the IMF-Bz, and the penetration of the dusk-to-dawn electric field over the dip equator is also discernible. Response of the low latitude ionosphere to this storm may be characterized in terms of (i

  10. Personal and trip characteristics associated with safety equipment use by injured adult bicyclists: a cross-sectional study

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    Teschke Kay

    2012-09-01

    Full Text Available Abstract Background The aim of this study was to estimate use of helmets, lights, and visible clothing among cyclists and to examine trip and personal characteristics associated with their use. Methods Using data from a study of transportation infrastructure and injuries to 690 adult cyclists in Toronto and Vancouver, Canada, we examined the proportion who used bike lights, conspicuous clothing on the torso, and helmets on their injury trip. Multiple logistic regression was used to examine associations between personal and trip characteristics and each type of safety equipment. Results Bike lights were the least frequently used (20% of all trips although they were used on 77% of trips at night. Conspicuous clothing (white, yellow, orange, red was worn on 33% of trips. Helmets were used on 69% of trips, 76% in Vancouver where adult helmet use is required by law and 59% in Toronto where it is not. Factors positively associated with bike light use included night, dawn and dusk trips, poor weather conditions, weekday trips, male sex, and helmet use. Factors positively associated with conspicuous clothing use included good weather conditions, older age, and more frequent cycling. Factors positively associated with helmet use included bike light use, longer trip distances, hybrid bike type, not using alcohol in the 6 hours prior to the trip, female sex, older age, higher income, and higher education. Conclusions In two of Canada’s largest cities, helmets were the most widely used safety equipment. Measures to increase use of visibility aids on both daytime and night-time cycling trips may help prevent crashes.

  11. Tissue specific diurnal rhythms of metabolites and their regulation during herbivore attack in a native tobacco, Nicotiana attenuata.

    Directory of Open Access Journals (Sweden)

    Sang-Gyu Kim

    Full Text Available Ecological performance is all about timing and the endogenous clock that allows the entrainment of rhythms and anticipation of fitness-determining events is being rapidly characterized. How plants anticipate daily abiotic stresses, such as cold in early mornings and drought at noon, as well as biotic stresses, such as the timing of pathogen infections, is being explored, but little is known about the clock's role in regulating responses to insect herbivores and mutualists, whose behaviors are known to be strongly diurnally regulated and whose attack is known to reconfigure plant metabolomes. We developed a liquid chromatography-mass spectrometry procedure and analyzed its output with model-based peak picking algorithms to identify metabolites with diurnal accumulation patterns in sink/source leaves and roots in an unbiased manner. The response of metabolites with strong diurnal patterns to simulated attack from the specialist herbivore, Manduca sexta larvae was analyzed and annotated with in-house and public databases. Roots and leaves had largely different rhythms and only 10 ions of 182 oscillating ions in leaves and 179 oscillating ions in roots were rhythmic in both tissues: root metabolites mainly peaked at dusk or night, while leaf metabolites peaked during the day. Many oscillating metabolites showed tissue-specific regulation by simulated herbivory of which systemic responses in unattacked tissues were particularly pronounced. Diurnal and herbivory-elicited accumulation patterns of disaccharide, phenylalanine, tyrosine, lyciumoside I, coumaroyl tyramine, 12-oxophytodienoic acid and jasmonic acid and those of their related biosynthetic transcripts were examined in detail. We conclude that oscillating metabolites of N. attenuata accumulate in a highly tissue-specific manner and the patterns reveal pronounced diurnal rhythms in the generalized and specialized metabolism that mediates the plant's responses to herbivores and mutualists. We

  12. Responses of properties in the plasma sheet and at the geosynchronous orbit to interplanetary shock

    Institute of Scientific and Technical Information of China (English)

    YAO Li; LIU ZhenXing; ZUO PingBing; ZHANG LingQian; DUAN SuPing

    2009-01-01

    On July 22,2004,the WIND spacecraft detected a typical interplanetary shock. There was sustaining weak southward magnetic field in the preshock region and the southward field was suddenly enhanced across the shock front (i.e.,southward turning). When the shock impinged on the magnetosphere,the magnetospheric plasma convection was abruptly enhanced in the central plasma sheet,which was directly observed by both the TC-1 and Cluster spacecraft located in different regions. Simultaneously,the Cluster spacecraft observed that the dawn-to-dusk electric field was abruptly enhanced. The variations of the magnetic field observed by TC-1,Cluster,GOES-10 and GOES-12 that were distributed in different regions in the plasma sheet and at the geosynchronous orbit are obviously distinct. TC-1 observations showed that the magnetic intensity kept almost unchanged and the elevation angle decreased,but the Cluster spacecraft,which was also in the plasma sheet and was further from the equator,observed that the magnetic field was obviously enhanced. Simultaneously,GOES-12 located near the midnight observed that the magnetic intensity sharply increased and the elevation angle decreased,but GOES-10 located in the dawn side observed that the magnetic field was merely compressed with its three components all sharply increasing. Furthermore,the energetic proton and electron fluxes at nearly all channels observed by five LANL satellites located at different magnetic local times (MLTs) all showed impulsive enhancements due to the compression of the shock. The responses of the energetic particles were much evident on the dayside than those on the nightside. Especially the responses near the midnight were rather weak. In this paper,the possible reasonable physical explanation to above observations is also discussed. All the shock-induced responses are the joint effects of the solar wind dynamic pressure pulse and the magnetic field southward turning.

  13. Digital clocks: simple Boolean models can quantitatively describe circadian systems.

    Science.gov (United States)

    Akman, Ozgur E; Watterson, Steven; Parton, Andrew; Binns, Nigel; Millar, Andrew J; Ghazal, Peter

    2012-09-07

    The gene networks that comprise the circadian clock modulate biological function across a range of scales, from gene expression to performance and adaptive behaviour. The clock functions by generating endogenous rhythms that can be entrained to the external 24-h day-night cycle, enabling organisms to optimally time biochemical processes relative to dawn and dusk. In recent years, computational models based on differential equations have become useful tools for dissecting and quantifying the complex regulatory relationships underlying the clock's oscillatory dynamics. However, optimizing the large parameter sets characteristic of these models places intense demands on both computational and experimental resources, limiting the scope of in silico studies. Here, we develop an approach based on Boolean logic that dramatically reduces the parametrization, making the state and parameter spaces finite and tractable. We introduce efficient methods for fitting Boolean models to molecular data, successfully demonstrating their application to synthetic time courses generated by a number of established clock models, as well as experimental expression levels measured using luciferase imaging. Our results indicate that despite their relative simplicity, logic models can (i) simulate circadian oscillations with the correct, experimentally observed phase relationships among genes and (ii) flexibly entrain to light stimuli, reproducing the complex responses to variations in daylength generated by more detailed differential equation formulations. Our work also demonstrates that logic models have sufficient predictive power to identify optimal regulatory structures from experimental data. By presenting the first Boolean models of circadian circuits together with general techniques for their optimization, we hope to establish a new framework for the systematic modelling of more complex clocks, as well as other circuits with different qualitative dynamics. In particular, we anticipate

  14. Quantifying Solar Wind-Polar Cap Interactions

    Science.gov (United States)

    Urban, K. D.; Gerrard, A. J.; Lanzerotti, L. J.; Weatherwax, A. T.; Huang, Y.

    2015-12-01

    It is well known that the solar wind is a major driver of ultra-low frequency [ULF] power at ground locations from low to high latitudes. However, due to the scarcity of deep polar cap magnetometer sites, it is not clear when, where, or if this is true deep inside the polar cap on open field lines where interplanetary magnetic field [IMF] ULF waves could possibly be directly detected. Given recent observations of very large Joule heating estimates from DMSP data, together with the large heating reported by the CHAMP satellite, it is important to understand the degree to which ULF waves in the solar wind can directly cause such heating. Using a time series of lagged correlation sequences ("dynamic correlograms") between GSM Bz ULF power (computed via data obtained from NASA's Advanced Composition Explorer [ACE] ahead of Earth in the solar wind) and the horizontal ULF power (H^2=N^2+E^2) from ground-based magnetometers in Earth's southern polar cap, we investigate the direct penetration of ULF waves from the solar wind into the polar ionosphere during a gamut of space weather conditions at a distributed network of Automated Geophysical Observatories [AGOs] in Antarctica. To infer causation, a predicted lag correlation maximum at each time step is computed by simply dividing the associated distance of ACE from Earth by the concurrent bulk solar wind speed. This technique helps parse out direct penetration of solar wind ULF waves from other sources (e.g., via leakage from closed field line resonances due to the bulk solar wind plasma viscously interacting at dawn/dusk flanks inducing Kelvin-Helmholtz instabilities [KHI] or compressional modes induced by impulses in solar wind dynamic pressure). The identified direct-penetrating ULF waves are related to the DMSP-derived Poynting fluxes by regression analysis, and conclusions are drawn for the importance of the ULF source for the measured heating.

  15. A Simulation Study of the Thermosphere Mass Density Response to Substorms Using GITM Model

    Science.gov (United States)

    Liu, X.; Ridley, A. J.

    2014-12-01

    The temporal and spatial variations of the thermosphere mass density during a variety of idealized substorms were investigated using the Global Ionosphere Thermosphere Model (GITM) simulation and Challenging Minisatellite Payload (CHAMP) satellite. From the GITM simulation, the maximum mass density perturbation of an idealized substorm with a peak variation of Hemispheric Power (HP) Index of 50 GW and interplanetary magnetic field (IMF) Bz of -2 nT was ~14% about 50 min after the substorm onset in the nightside sector of the aurora zone. About 110 min after onset, a negative mass density perturbation (~-5%) occurred in the night sector, which was consistent with the mass density measurement of the CHAMP satellite. Further investigation suggests that a large scale in situ gravity wave was generated in the aurora zone and propagated to the mid and low latitudes. Simulations with IMF Bz changes, with HP being constant and HP changing and IMF Bz being constant were run to investigate any nonlinearities in the combined response. The mass density perturbation due the IMF Bz variation peaks in the dusk sector and the density perturbation due to HP input peaks in the nightside sector. The non-linear of the mass density response to different energy input is less than 6%. The thermospheric mass density at higher altitudes is more sensitive to the Joule heating energy input. The change in hemisphere power adds electron density to lower altitudes, so the heating due to the HP change is at lower altitudes than the heating due to the IMF Bz change. This causes the density change due to the HP change to be larger than the density change due to the IMF change.

  16. Ions from Different Sources in the near-Earth High-Latitude Magnetotail

    Science.gov (United States)

    Koleva, R.; Semkova, J.; Fedorov, A.; Smirnov, V.

    2003-04-01

    We investigate the characteristics of the ion population in the near-Earth (distances from 5 Re to 10 Re) magnetotail region poleward of the exterior cusp and the auroral field lines. The study presented is based on data from the Low Energy Plasma Composition Experiment (AMEI-2) aboard the high-apogee INTERBALL-1 satellite. Characteristic features of the region are the low plasma density and the low electron energy. We discuss several cases of ion spectral and composition measurements, using He++ as a tracer of SW plasma and O+ as a tracer of ionospheric plasma. Ion fluxes exhibit complex structure bearing the history of ions origin and consecutive acceleration. Both Solar wind and ionospheric ions are present in this region. O+ beams are regularly observed, as expected, going away or towards the Earth, with energies up to about 2 keV/q. A small amount of isotropic, high-temperature plasma sheet ions is always present. But dominating is a He++ population with energies in the interval 1 - 2.5 keV/q, either isotropic in pitch angle or consisting of counter-flowing ions with wide pitch-angular distribution. We discuss the possible relation of these populations with the ion populations observed downtail in the lobes, the PSBL, the 'mixed region' at the dusk flunk as identified by Fuselier et al. on base of ISEE-1 and ISEE-2 (J. Geophys. Res., 1999) and the lobe-plasma transition layer, defined by WIND data by Wilbert et al, (J. Geophys. Res., 2001).

  17. Empirical studies of magnetosheath and tail field and current structure, and model comparisons. Ph.D. Thesis

    Energy Technology Data Exchange (ETDEWEB)

    Kaymaz, Z.

    1993-12-31

    In this dissertation, the authors present the observational results obtained with IMP-8 in the magnetosheath and magnetotail, and compare them with the results from the gas dynamic (GD) and global magnetohydrodynamic (MHD) models. Although the magnetotail has been investigated by many others, the magnetosheath is one of the least studied regions of space despite its importance in solar wind-magnetosphere coupling. In this study, by utilizing a large magnetometer data set obtained simultaneously from IMP-8 and ISEE-3, the authors construct average magnetic field vector maps of the magnetosheath and tail in the cross-sectional plane. They determine how this average structure is influenced by the IMF, the Earth`s dipole tilt angle, and geomagnetic activity. For equatorial IMF`s, the magnetosheath field drapes asymmetrically around the magnetosphere causing a rotation of the field draping pattern, the tail current sheet twists, and plasma sheet field lines cease to show north-south symmetry. The magnetic field structure for north/south IMF`s is also shown to exhibit different properties including irregularities in the sheath (for southward) and placement of the dipolar and flaring regions in the tail. An IMF related perturbation field is observed in the tail which is strongest on the plasma sheet dawn and dusk sides for equatorial IMF, and on the flanks for north-south IMF. The Earth`s dipole tilt with respect to the geomagnetic equator affects the magnetotail current structure by causing its displacement from the geomagnetic equator. The authors examine the structure of the current sheet shape and location extensively using 16-years of IMP-8 magnetic field data. They show how geomagnetic activity affects this displacement. Many other field and current properties of the tail structure are also investigated such as the spatial distribution of the current density vectors and the (J x B) forces.

  18. Dst Index in the 2008 GEM Modeling Challenge - Model Performance for Moderate and Strong Magnetic Storms

    Science.gov (United States)

    Rastaetter, Lutz; Kuznetsova, Maria; Hesse, Michael; Chulaki, Anna; Pulkkinen, Antti; Ridley, Aaron J.; Gombosi, Tamas; Vapirev, Alexander; Raeder, Joachim; Wiltberger, Michael James; Mays, M. L.; Fok, Mei-Ching H.; Weigel, Robert S.; Welling, Daniel T.

    2010-01-01

    The GEM 2008 modeling challenge efforts are expanding beyond comparing in-situ measurements in the magnetosphere and ionosphere to include the computation of indices to be compared. The Dst index measures the largest deviations of the horizontal magnetic field at 4 equatorial magnetometers from the quiet-time background field and is commonly used to track the strength of the magnetic disturbance of the magnetosphere during storms. Models can calculate a proxy Dst index in various ways, including using the Dessler-Parker Sckopke relation and the energy of the ring current and Biot-Savart integration of electric currents in the magnetosphere. The GEM modeling challenge investigates 4 space weather events and we compare models available at CCMC against each other and the observed values of Ost. Models used include SWMF/BATSRUS, OpenGGCM, LFM, GUMICS (3D magnetosphere MHD models), Fok-RC, CRCM, RAM-SCB (kinetic drift models of the ring current), WINDMI (magnetosphere-ionosphere electric circuit model), and predictions based on an impulse response function (IRF) model and analytic coupling functions with inputs of solar wind data. In addition to the analysis of model-observation comparisons we look at the way Dst is computed in global magnetosphere models. The default value of Dst computed by the SWMF model is for Bz the Earth's center. In addition to this, we present results obtained at different locations on the Earth's surface. We choose equatorial locations at local noon, dusk (18:00 hours), midnight and dawn (6:00 hours). The different virtual observatory locations reveal the variation around the earth-centered Dst value resulting from the distribution of electric currents in the magnetosphere during different phases of a storm.

  19. Gene and genome parameters of mammalian liver circadian genes (LCGs.

    Directory of Open Access Journals (Sweden)

    Gang Wu

    Full Text Available The mammalian circadian system controls various physiology processes and behavior responses by regulating thousands of circadian genes with rhythmic expressions. In this study, we redefined circadian-regulated genes based on published results in the mouse liver and compared them with other gene groups defined relative to circadian regulations, especially the non-circadian-regulated genes expressed in liver at multiple molecular levels from gene position to protein expression based on integrative analyses of different datasets from the literature. Based on the intra-tissue analysis, the liver circadian genes or LCGs show unique features when compared to other gene groups. First, LCGs in general have less neighboring genes and larger in both genomic and 3'-UTR lengths but shorter in CDS (coding sequence lengths. Second, LCGs have higher mRNA and protein abundance, higher temporal expression variations, and shorter mRNA half-life. Third, more than 60% of LCGs form major co-expression clusters centered in four temporal windows: dawn, day, dusk, and night. In addition, larger and smaller LCGs are found mainly expressed in the day and night temporal windows, respectively, and we believe that LCGs are well-partitioned into the gene expression regulatory network that takes advantage of gene size, expression constraint, and chromosomal architecture. Based on inter-tissue analysis, more than half of LCGs are ubiquitously expressed in multiple tissues but only show rhythmical expression in one or limited number of tissues. LCGs show at least three-fold lower expression variations across the temporal windows than those among different tissues, and this observation suggests that temporal expression variations regulated by the circadian system is relatively subtle as compared with the tissue expression variations formed during development. Taken together, we suggest that the circadian system selects gene parameters in a cost effective way to improve tissue

  20. Storm Signatures and Irregularities in the Equatorial Ionosphere Observed by Using FORMOSAT-3/COSMIC (Invited)

    Science.gov (United States)

    Liu, J. G.; Chen, L.; Hsu, R.; Lee, I.; Chang, G.; Yu, S.; Liu, T.

    2013-12-01

    This paper reports that fluctuations in the vertical electron density triggering by magnetic storms and irregularities of S4 scintillations in the equatorial ionosphere probed by FORMOSAT-3/COSMIC (F3/C). For the storm study, the electron density profiles derived by the F3/C RO (radio occultation) in high-, mid- and low-latitudes during the quiet time and disturbed periods are subdivided into four sectors, noon, dusk, midnight, and dawn, to find wavy characteristics. The wavelet transformation is further applied to examine the profiles before and during the storm period. Above 300km, the ionosphere becomes very structured, and the amplitude in fluctuations of 15~30km wavelength significantly enhances during the storm period, especially high latitude region. The concurrence in changes of the geomagnetic index and the ionospheric density suggest that penetration electric fields and energy inputs at high latitudes play important roles. On the other hand, the F3/C RO provides an excellent opportunity to monitor three-dimensional structures and dynamics of the ionospheric scintillations during the low solar activity year of 2007-2013. Measurements of the global F3/C S4 index are subdivided and examined in various latitudes, longitudes, altitudes, and seasons. The F-region scintillations in the equatorial and low-latitude ionosphere start around post-sunset period and often persist till post-midnight hours (0300 MLT, magnetic local time) during the March and September equinox as well as December Solstice seasons. The E-region scintillations reveal a clear solar zenith effect and yield pronounced intensities in mid-latitudes during the Summer Solstice seasons, which are well correlated with occurrences of the sporadic E-layer. Finally, impact of the F3/C follow-on, FORMOSAT-7/COSMIC-2, mission on ionospheric space weather monitoring will be briefed.

  1. Thermal variation and factors influencing vertical migration behavior in Daphnia populations.

    Science.gov (United States)

    Glaholt, Stephen P; Kennedy, Meghan L; Turner, Elizabeth; Colbourne, John K; Shaw, Joseph R

    2016-08-01

    The antipredator behavior diel vertical migration (DVM), common in aquatic keystone species Daphnia, involves daily migration from warmer surface waters before dawn to cooler deeper waters after dusk. Plasticity in Daphnia DVM behavior optimizes fitness via trade-offs between growth, reproduction, and predator avoidance. Migration behavior is affected by co-varying biotic and abiotic factors, including light, predator cues, and anthropogenic stressors making it difficult to determine each factor's individual contribution to the variation in this behavior. This study aims to better understand this ecologically significant behavior in Daphnia by: (1) determining how Daphnia pulicaria thermal preferences vary within and among natural populations; (2) distinguishing the role of temperature verses depth in Daphnia vertical migration; and (3) defining how two anthropogenic stressors (copper and nickel) impact Daphnia migratory behavior. Simulated natural lake stratification were constructed in 8L (0.5m tall, 14.5cm wide) water columns to monitor under controlled laboratory conditions the individual effects of temperature gradients, depth, and metal stressors on Daphnia vertical migration. Three major findings are reported. First, while no difference in thermal preference was found among the four populations studied, within lake populations variability among isolates was high. Second, decoupling temperature and depth revealed that depth was a better predictor of Daphnia migratory patterns over temperature. Third, exposure to environmentally relevant concentrations of copper or nickel inhibited classic DVM behavior. These findings revealed the high variability in thermal preference found within Daphnia populations, elucidated the individual roles that depth and temperature have on migratory behavior, and showed how copper and nickel can interfere with the natural response of Daphnia to fish predator cues. Thus contributing to the body of knowledge necessary to predict how

  2. Host-Seeking Behavior and Arbovirus Detection in Mosquitoes of Habahe County, Xinjiang Uigur Autonomous Region, China.

    Science.gov (United States)

    Guo, Xiao-Xia; Zhang, Ying-Mei; Li, Chun-Xiao; Zhang, Gui-Lin; Zheng, Zhong; Dong, Yan-De; Xue, Rui-De; Xing, Dan; Zhao, Tong-Yan

    2015-12-01

    Mosquitoes in Habahe County of Xinjiang Uigur Autonomous Region in China are considered a serious nuisance problem to local residents, but little is known of their role in enzootic disease. Therefore, host-seeking behavior and virus detection in mosquitoes were investigated in this study. Adult host-seeking mosquitoes were sampled using the Centers for Disease Control and Prevention (CDC) light traps operated at three locations in June through August 2008. Nine traps were used at each location at 3 different heights (1 m, 3 m, and 5 m). Seven mosquito species from 4 genera were collected by CDC light traps in different habitats. In total, 90,055 mosquitoes were captured, of which Aedes vexans was the most abundant species, comprising 88.02% of all mosquitoes collected. The second most abundant species was Anopheles messese, which comprised about 5.86%. Other species caught were Culex modestus (2.89%), Aedes caspius (1.11%), Coquillettidia richiardii (0.61%), Ae. dorsalis (1.36%), and An. hyrcanus (0.14%). About 93.5% of Ae. vexans individuals were caught in CO2-baited CDC light traps at 1 m above the ground. The highest numbers of Cx. modestus were caught at the highest trap level, 5 m above ground. Overall, significantly more mosquitoes of all species were collected at dusk than at dawn. Based on blood-meal analyses, Ae. vexans and An. messese fed on various vertebrate hosts, whereas Cx. modestus fed on ducks only. From a total of 335 mosquito pools tested, 10 pools of Ae. vexans were found positive for alphavirus. Comparison with the gene database revealed that the alphavirus deoxyribonucleic acid fragment obtained (GenBank accession no. HM160530) was 100% homologous at the nucleotide level to chikungunya virus isolate LK (PB) chik3408, chikungunya virus isolate SGEHICHD122508, and chikungunya virus strain FD080231. The results of this study suggest that ongoing, integrated mosquito and arbovirus surveillance is necessary in this river wetland.

  3. Temporal and spatial variations in microclimate influence the larval foraging behaviors and performance of a conifer-feeding sawfly.

    Science.gov (United States)

    Johns, R C; Boone, J; Leggo, J J; Smith, S; Carleton, D; Quiring, D T

    2012-06-01

    Herbivorous insects are often exposed to broad temporal and spatial variations in microclimate conditions within their host plants and have adapted a variety of behaviors, such as avoidance or basking, to either offset or benefit from such variation. Field experiments were carried out to investigate the influence of daily and intratree variations in microclimate on the behaviors (feeding, resting, dispersal, and hiding) and associated performance of late-instar larvae of the yellowheaded spruce sawfly, Pikonema alaskensis (Rohwer) (Hymenoptera: Tenthredinidae) within crowns of 1.25-1.5 m tall black spruce (Picea mariana [Miller] Britton Sterns Poggenburg); late instars feed on developing shoots of young spruce and are often exposed to microclimatic extremes with unknown effects on performance. Larvae fed diurnally from just after dawn (0800 h) until dusk (2000 h) and rested throughout the night, with brief periods of dispersal occurring in the morning and evening. Neither larval behavior nor abiotic conditions differed significantly between the upper and lower crowns of trees. Temperature, humidity, and solar insolation all explained >90% of variation in feeding; however, sunrise and sunset were the most likely cues influencing diurnal behavior. Most larvae (94%) fed on the bottom, shaded side of shoots, and field experiments indicated that this behavior is adaptive with respect to microclimate, probably reducing hygrothermal stress. Thus, behavioral adaptations by P. alaskensis to daily and within-shoot microclimatic variation may reduce the risk of hygrothermal stress during dispersal or feeding, while still allowing larvae to feed on the preferred and highly nutritious upper crown foliage of young spruce.

  4. Combining Synthetic Human Odours and Low-Cost Electrocuting Grids to Attract and Kill Outdoor-Biting Mosquitoes: Field and Semi-Field Evaluation of an Improved Mosquito Landing Box.

    Science.gov (United States)

    Matowo, Nancy S; Koekemoer, Lizette L; Moore, Sarah J; Mmbando, Arnold S; Mapua, Salum A; Coetzee, Maureen; Okumu, Fredros O

    2016-01-01

    On-going malaria transmission is increasingly mediated by outdoor-biting vectors, especially where indoor insecticidal interventions such as long-lasting insecticide treated nets (LLINs) are widespread. Often, the vectors are also physiologically resistant to insecticides, presenting major obstacles for elimination. We tested a combination of electrocuting grids with synthetic odours as an alternative killing mechanism against outdoor-biting mosquitoes. An odour-baited device, the Mosquito Landing Box (MLB), was improved by fitting it with low-cost electrocuting grids to instantly kill mosquitoes attracted to the odour lure, and automated photo switch to activate attractant-dispensing and mosquito-killing systems between dusk and dawn. MLBs fitted with one, two or three electrocuting grids were compared outdoors in a malaria endemic village in Tanzania, where vectors had lost susceptibility to pyrethroids. MLBs with three grids were also tested in a large semi-field cage (9.6 × 9.6 × 4.5m), to assess effects on biting-densities of laboratory-reared Anopheles arabiensis on volunteers sitting near MLBs. Significantly more mosquitoes were killed when MLBs had two or three grids, than one grid in wet and dry seasons (Pmosquitoes, 99% were non-blood fed, suggesting host-seeking status. In the semi-field, the MLBs reduced mean number of malaria mosquitoes attempting to bite humans fourfold. The improved odour-baited MLBs effectively kill outdoor-biting malaria vector mosquitoes that are behaviourally and physiologically resistant to insecticidal interventions e.g. LLINs. The MLBs reduce human-biting vector densities even when used close to humans, and are insecticide-free, hence potentially antiresistance. The devices could either be used as surveillance tools or complementary mosquito control interventions to accelerate malaria elimination where outdoor transmission is significant.

  5. Simultaneous Double Star and Cluster FTEs observations on the dawnside flank of the magnetosphere

    Directory of Open Access Journals (Sweden)

    A. Marchaudon

    2005-11-01

    Full Text Available We present Cluster and Double Star-1 (TC-1 observations from a close magnetic conjunction on 8 May 2004. The five spacecraft were on the dawnside flank of the magnetosphere, with TC-1 located near the equatorial plane and Cluster at higher geographic latitudes in the Southern Hemisphere. TC-1, at its apogee, skimmed the magnetopause for almost 8h (between 08:00-16:00 UT. Flux Transfer Events (FTEs, moving southward/tailward from the reconnection site, were observed by TC-1 throughout almost all of the period. Cluster, travelling on a mainly dawn-dusk trajectory, crossed the magnetopause at around 10:30 UT in the same Magnetic Local Time (MLT sector as TC-1 and remained close to the magnetopause boundary layer in the Southern Hemisphere. The four Cluster spacecraft observed FTEs for a period of 6.5h between 07:30 and 14:00 UT.

    The very clear signatures and the finite transverse sizes of the FTEs observed by TC-1 and Cluster imply that, during this event, sporadic reconnection occurred. From the properties of these FTEs, the reconnection site was located northward of both TC-1 and Cluster on the dawn flank of the magnetosphere. Reconnection occurred between draped magnetosheath and closed magnetospheric field lines. Despite variable interplanetary magnetic field (IMF conditions and IMF-Bz turnings, the IMF clock angle remained greater than 70° and the location site appeared to remain relatively stable in position during the whole period. This result is in agreement with previous studies which reported that the dayside reconnection remained active for an IMF clock angle greater than 70°. The simultaneous observation of FTEs at both Cluster and TC-1, separated by 2h in MLT, implies that the reconnection site on the magnetopause must have been extended over several hours in MLT.

  6. Automated Thermal Image Processing for Detection and Classification of Birds and Bats - FY2012 Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Duberstein, Corey A.; Matzner, Shari; Cullinan, Valerie I.; Virden, Daniel J.; Myers, Joshua R.; Maxwell, Adam R.

    2012-09-01

    Surveying wildlife at risk from offshore wind energy development is difficult and expensive. Infrared video can be used to record birds and bats that pass through the camera view, but it is also time consuming and expensive to review video and determine what was recorded. We proposed to conduct algorithm and software development to identify and to differentiate thermally detected targets of interest that would allow automated processing of thermal image data to enumerate birds, bats, and insects. During FY2012 we developed computer code within MATLAB to identify objects recorded in video and extract attribute information that describes the objects recorded. We tested the efficiency of track identification using observer-based counts of tracks within segments of sample video. We examined object attributes, modeled the effects of random variability on attributes, and produced data smoothing techniques to limit random variation within attribute data. We also began drafting and testing methodology to identify objects recorded on video. We also recorded approximately 10 hours of infrared video of various marine birds, passerine birds, and bats near the Pacific Northwest National Laboratory (PNNL) Marine Sciences Laboratory (MSL) at Sequim, Washington. A total of 6 hours of bird video was captured overlooking Sequim Bay over a series of weeks. An additional 2 hours of video of birds was also captured during two weeks overlooking Dungeness Bay within the Strait of Juan de Fuca. Bats and passerine birds (swallows) were also recorded at dusk on the MSL campus during nine evenings. An observer noted the identity of objects viewed through the camera concurrently with recording. These video files will provide the information necessary to produce and test software developed during FY2013. The annotation will also form the basis for creation of a method to reliably identify recorded objects.

  7. An empirical RBF model of the magnetosphere parameterized by interplanetary and ground-based drivers

    Science.gov (United States)

    Tsyganenko, N. A.; Andreeva, V. A.

    2016-11-01

    In our recent paper (Andreeva and Tsyganenko, 2016), a novel method was proposed to model the magnetosphere directly from spacecraft data, with no a priori knowledge nor ad hoc assumptions about the geometry of the magnetic field sources. The idea was to split the field into the toroidal and poloidal parts and then expand each part into a weighted sum of radial basis functions (RBF). In the present work we take the next step forward by having developed a full-fledged model of the near magnetosphere, based on a multiyear set of space magnetometer data (1995-2015) and driven by ground-based and interplanetary input parameters. The model consolidates the largest ever amount of data and has been found to provide the best ever merit parameters, in terms of both the overall RMS residual field and record-high correlation coefficients between the observed and model field components. By experimenting with different combinations of input parameters and their time-averaging intervals, we found the best so far results to be given by the ram pressure Pd, SYM-H, and N-index by Newell et al. (2007). In addition, the IMF By has also been included as a model driver, with a goal to more accurately represent the IMF penetration effects. The model faithfully reproduces both externally and internally induced variations in the global distribution of the geomagnetic field and electric currents. Stronger solar wind driving results in a deepening of the equatorial field depression and a dramatic increase of its dawn-dusk asymmetry. The Earth's dipole tilt causes a consistent deformation of the magnetotail current sheet and a significant north-south asymmetry of the polar cusp depressions on the dayside. Next steps to further develop the new approach are also discussed.

  8. Photopigment basis for dichromatic color vision in the horse.

    Science.gov (United States)

    Carroll, J; Murphy, C J; Neitz, M; Hoeve, J N; Neitz, J

    2001-01-01

    Horses, like other ungulates, are active in the day, at dusk, dawn, and night; and, they have eyes designed to have both high sensitivity for vision in dim light and good visual acuity under higher light levels (Walls, 1942). Typically, daytime activity is associated with the presence of multiple cone classes and color-vision capacity (Jacobs, 1993). Previous studies in other ungulates, such as pigs, goats, cows, sheep and deer, have shown that they have two spectrally different cone types, and hence, at least the photopigment basis for dichromatic color vision (Neitz & Jacobs, 1989; Jacobs, Deegan II, Neitz, Murphy, Miller, & Marchinton, 1994; Jacobs, Deegan II, & Neitz, 1998). Here, electroretinogram flicker photometry was used to measure the spectral sensitivities of the cones in the domestic horse (Equus caballus). Two distinct spectral mechanisms were identified and are consistent with the presence of a short-wavelength-sensitive (S) and a middle-to-long-wavelength-sensitive (M/L) cone. The spectral sensitivity of the S cone was estimated to have a peak of 428 nm, while the M/L cone had a peak of 539 nm. These two cone types would provide the basis for dichromatic color vision consistent with recent results from behavioral testing of horses (Macuda & Timney, 1999; Macuda & Timney, 2000; Timney & Macuda, 2001). The spectral peak of the M/L cone photopigment measured here, in vivo, is similar to that obtained when the gene was sequenced, cloned, and expressed in vitro (Yokoyama & Radlwimmer, 1999). Of the ungulates that have been studied to date, all have the photopigment basis for dichromatic color vision; however, they differ considerably from one another in the spectral tuning of their cone pigments. These differences may represent adaptations to the different visual requirements of different species.

  9. Locust displacing winds in eastern Australia reassessed with observations from an insect monitoring radar

    Science.gov (United States)

    Hao, Zhenhua; Drake, V. Alistair; Sidhu, Leesa; Taylor, John R.

    2017-07-01

    Based on previous investigations, adult Australian plague locusts are believed to migrate on warm nights (with evening temperatures >25 °C), provided daytime flight is suppressed by surface winds greater than the locusts' flight speed, which has been shown to be 3.1 m s-1. Moreover, adult locusts are believed to undertake briefer `dispersal' flights on nights with evening temperature >20 °C. To reassess the utility of these conditions for forecasting locust flight, contingency tests were conducted comparing the nights selected on these bases (predicted nights) for the months of November, January, and March and the nights when locust migration were detected with an insect monitoring radar (actual nights) over a 7-year period. In addition, the wind direction distributions and mean wind directions on all predicted nights and actual nights were compared. Observations at around 395 m above ground level (AGL), the height at which radar observations have shown that the greatest number of locusts fly, were used to determine the actual nights. Tests and comparisons were also made for a second height, 990 m AGL, as this was used in the previous investigation. Our analysis shows that the proposed criteria are successful from predicting migratory flight only in March, when the surface temperature is effective as a predicting factor. Surface wind speed has no predicting power. It is suggested that a strong daytime surface wind speed requirement should not be considered and other meteorological variables need to be added to the requirement of a warm surface temperature around dusk for the predictions to have much utility.

  10. Host-dependent differences in resource use associated with Anilocra spp. parasitism in two coral reef fishes, as revealed by stable carbon and nitrogen isotope analyses

    Science.gov (United States)

    Welicky, Rachel; Demopoulos, Amanda W. J.; Sikkel, Paul C.

    2017-01-01

    The role of parasites in trophic ecology is poorly understood in marine ecosystems. Stable isotope analyses (SIA) have been widely used in studies of trophic ecology, but have rarely been applied to study the role of parasites. Considering that some parasites are associated with altered host foraging patterns, SIA can help elucidate whether parasitism influences host trophic interactions. French grunt (Haemulon flavolineatum), an abundant Caribbean coral reef fish, contributes greatly to trophic connectivity. They typically depart the reef at dusk, feed overnight in seagrass beds, and return to the reef at dawn. The large parasitic isopod Anilocra haemuli commonly infects French grunt, and infected fish are less likely to complete their diel migration, and are in poorer condition than uninfected conspecifics. Brown chromis (Chromis multilineata) are diurnally feeding planktivores and infection by Anilocra chromis does not influence host condition. To determine if Anilocra infection influences host diet and foraging locality, we conducted stable carbon and nitrogen isotope analyses on scale, muscle, heart and gill tissues of infected and uninfected French grunt and brown chromis. We determined that all French grunt had δ13C values representative of seagrass habitats, but infected French grunt were significantly enriched in 13C and 15N compared to uninfected conspecifics. This suggests that compared to uninfected conspecifics, infected French grunt forage in seagrass, but on isotopically enriched prey, and/or are in poorer condition, which can elevate δ13C and δ15N values. For brown chromis, infection did not significantly influence any δ13C and δ15N values; hence they all foraged in the same environment and on similar prey. This is the first study to use SIA to examine differences in resource use by Caribbean coral reef fishes associated with parasitism and to evaluate how closely related parasites might have host-dependent effects on host trophic ecology.

  11. The daytime cycle in dust aerosol direct radiative effects observed in the central Sahara during the Fennec campaign in June 2011

    KAUST Repository

    Banks, Jamie R.

    2014-12-16

    © 2014. American Geophysical Union. All Rights Reserved. The direct clear-sky radiative effect (DRE) of atmospheric mineral dust is diagnosed over the Bordj Badji Mokhtar (BBM) supersite in the central Sahara during the Fennec campaign in June 2011. During this period, thick dust events were observed, with aerosol optical depth values peaking at 3.5. Satellite observations from Meteosat-9 are combined with ground-based radiative flux measurements to obtain estimates of DRE at the surface, top-of-atmosphere (TOA), and within the atmosphere. At TOA, there is a distinct daytime cycle in net DRE. Both shortwave (SW) and longwave (LW) DRE peak around noon and induce a warming of the Earth-atmosphere system. Toward dusk and dawn, the LW DRE reduces while the SW effect can switch sign triggering net radiative cooling. The net TOA DRE mean values range from -9 Wm-2 in the morning to heating of +59 Wm-2 near midday. At the surface, the SW dust impact is larger than at TOA: SW scattering and absorption by dust results in a mean surface radiative cooling of 145Wm-2. The corresponding mean surface heating caused by increased downward LW emission from the dust layer is a factor of 6 smaller. The dust impact on the magnitude and variability of the atmospheric radiative divergence is dominated by the SW cooling of the surface, modified by the smaller SW and LW effects at TOA. Consequently, dust has a mean daytime net radiative warming effect on the atmosphere of 153Wm-2.

  12. Pressure Gradient Evolution and Substorm Onset

    Science.gov (United States)

    Zhonghua, Y.; Pu, Z.; Cao, X.; Nishimura, T.; Zhang, H.; Fu, S.; Xie, L.; Guo, R.

    2011-12-01

    Near-Earth current disruption (NECD) and substorm current wedge (SCW) formation are two related key phenomena for substorm onset. They are believed to be in close association with evolution of pressure gradient near the inner edge of plasma sheet. In the past, a few attempts have been made to investigate the pressure gradient in the late growth phase based on one- or two-spacecraft observations (e.g. , Korth et al., 1991; Pu et al., 1992; Shiokawa et al., 1998; Xing et al., 2010, 2011,etc). In this paper, with linearization assumption in the inner-probe region, we use THEMIS three-probe measurements to estimate the pressure gradient near the inner edge of the equatorward and duskward (dawnward) plasma sheet where pressure gradient in the Z-direction is almost vanished. We therefore can roughly get the two-dimensional pressure gradient in the X- and Y-direction simultaneously. Our observations indicate that the pressure gradients in both the X- and Y-direction enhance right after (within one minute) substorm onset. The enhanced pressure gradient in the Y-direction is duskward (dawnward) when the probes are in the duskside (dawnside) of the enhanced earthward flow in the growth phase. The enhanced dawn-dusk pressure gradients can drive downward field-aligned current (FAC) on the dawnside and upward FAC on the duskside, thus make contributions to the NECD and formation of SCW. THEMIS in situ data and all-sky auroral images for two events are presented, followed by a brief discussion.

  13. Meteorological observations on Martian surface : met-packages of Mars-96 Small Stations and Penetrators

    Science.gov (United States)

    Harri, A.-M.; Linkin, V.; Polkko, J.; Marov, M.; Pommereau, J.-P.; Lipatov, A.; Siili, T.; Manuilov, K.; Lebedev, V.; Lehto, A.; Pellinen, R.; Pirjola, R.; Carpentier, T.; Malique, C.; Makarov, V.; Khloustova, L.; Esposito, L.; Maki, J.; Lawrence, G.; Lystsev, V.

    1998-02-01

    The scientific objectives of a meterological experiment on the Martian surface are defined, and the meteorological equipment of the landing elements of the Mars-96 mission are described with emphasis on the applicability for re-use in forthcoming Mars missions. The general strategy for atmospheric surface observations is discussed. Meteorological surface observations are of utmost value in studying the Martian atmosphere. The climatological cycles and atmospheric circulations, as well as the boundary layer phenomena can be understood thoroughly only, if the contribution of in situ surface measurements are amalgamated with the remote observations. The Mars-96 mission had an ambitious goal of deploying four versatile payloads at four Northern hemispheric sites. The observations of pressure, temperature, wind, atmospheric optical thickness and humidity, as well as pressure and temperature measurements during the atmospheric descent were included in the meteorology experiment. Even though the Mars-96 mission was unsuccessful, the objectives and implementation of the meteorology experiment are applicable to any forthcoming landing mission to Mars. This applies both to a mission having a number of observation sites spread all over the surface of Mars, and to a single lander or rover. The main operational objective of this meteorological experiment is to provide a regular time series of the meteorological parameters with accelerated measurement campaigns during dawn and dusk. Such a data set would substantially improve our understanding of the atmospheric structure, dynamics, climatological cycles, and the atmosphere-surface interactions. The implementation of the meteorology instrument features advanced sensor technology and flexible system design. The application on the Mars-96 landing elements was, however, severely constrained by the limited power supply. The usefulness of the system can be substantially enhanced by modest additional resources and with few or no

  14. Analysis on Mathematical Model of “The Moon Hung above the Willow Tree”%对“月上柳梢头”的数学模型分析

    Institute of Scientific and Technical Information of China (English)

    李波; 王妍婷; 常星星

    2015-01-01

    研究2015年全国大学生数学建模竞赛C题,首先定义“月上柳梢头”时月亮在空中的角度和什么时间称为“黄昏后”,建立数学模型,用Mathematica软件编程,计算出结果;其次又建立模型,分析2016年北京地区“月上柳梢头,人约黄昏后”发生的日期与时间以及其他纬度地区能看到此景的日期与时间。计算数据表明,此情景主要发生在中纬度地区,高纬度地区一般少发生。%This paper studies the question C of 2015 China National Undergraduate Mathematical Contest in Modeling. Firstly, it gives the definition of the angle of the moon in the sky when “The moon hung above the willow tree” and when it is called “after dusk”, then establishes mathematical model ,and uses mathematics software programming to calculated results which are shown in Table 1 and 2. Secondly, it establishes another mathematical model to analyze the occurrence time and the occurrence date of“The moon hung above the willow tree, at dusk he had a tryst with me” in Beijing and other latitudes where this scene can be seen in 2016, and these results are shown in Table 3 and 4. These data shows that the scene mainly happens in middle⁃latitude areas and less occurs in high⁃latitude areas.

  15. Two-dimensional electric field measurements in the ionospheric footprint of a flux transfer event

    Directory of Open Access Journals (Sweden)

    K. A. McWilliams

    Full Text Available Line-of-sight Doppler velocities from the SuperDARN CUTLASS HF radar pair have been combined to produce the first two-dimensional vector measurements of the convection pattern throughout the ionospheric footprint of a flux transfer event (a pulsed ionospheric flow, or PIF. Very stable and moderate interplanetary magnetic field conditions, along with a preceding prolonged period of northward interplanetary magnetic field, allow a detailed study of the spatial and the temporal evolution of the ionospheric response to magnetic reconnection. The flux tube footprint is tracked for half an hour across six hours of local time in the auroral zone, from magnetic local noon to dusk. The motion of the footprint of the newly reconnected flux tube is compared with the ionospheric convection velocity. Two primary intervals in the PIF's evolution have been determined. For the first half of its lifetime in the radar field of view the phase speed of the PIF is highly variable and the mean speed is nearly twice the ionospheric convection speed. For the final half of its lifetime the phase velocity becomes much less variable and slows down to the ionospheric convection velocity. The evolution of the flux tube in the magnetosphere has been studied using magnetic field, magnetopause and magnetosheath models. The data are consistent with an interval of azimuthally propagating magnetopause reconnection, in a manner consonant with a peeling of magnetic flux from the magnetopause, followed by an interval of anti-sunward convection of reconnected flux tubes.

    Key words: Magnetospheric physics (magnetosphere · ionosphere interactions; plasma convection; solar wind · magnetosphere interactions

  16. High irradiance responses involving photoreversible multiple photoreceptors as related to photoperiodic induction of cell division in Euglena.

    Science.gov (United States)

    Bolige, Aoen; Goto, Ken

    2007-02-01

    Little is known about the photoreceptors involved in the photoperiodism of unicellular organisms, which we elucidated by deriving their action spectra. The flagellated alga Euglena gracilis exhibits photoperiodism, with a long-day response in cell reproduction. The underlying clock is a circadian rhythm with photoinductive capability, peaking at subjective dusk and occurring at the 26th hour in continuous darkness (DD) when transferred from continuous light (LL); it regulates photoinduction, a high-irradiance response (HIR), of a dark-capability of progressing through cell division. We derived the action spectra by irradiating E. gracilis with monochromatic light for 3h at around the 26th hour; the action maxima occurred at 380, 450-460, 480, 610, 640, 660, 680, and 740nm. Except for the maximum at 450-460nm, which was always a major maximum, the maxima greatly depended on the red (R)/far-red (FR) ratio of the prior LL. The high R/FR ratio resulted in a dominant major peak at 640nm and minor peaks at 480 and 680nm, whereas the low ratio resulted in dominant major peaks at 610 and 740nm and minor peaks at 380 and 660nm; the critical fluence was minimally about 60mmolm(-2). These HIRs resulted from the accumulation of corresponding low-fluence responses (LFRs) because we found that repetition of a 3-min light/dark cycle, with critical fluences of 1mmolm(-2), lasting for 3h resulted in the same photoinduction as the continuous 3-h irradiation. Moreover, these LFRs expressed photoreversibility. Thus, photoperiodic photoinduction involves Euglena-phytochrome (640 and 740nm) and blue photoreceptor (460nm). Although 380, 480, 610, 660, and 680nm may also represent Euglena-phytochrome, a definite conclusion awaits further study.

  17. DEET mosquito repellent sold through social marketing provides personal protection against malaria in an area of all-night mosquito biting and partial coverage of insecticide-treated nets: a case-control study of effectiveness.

    Science.gov (United States)

    Rowland, Mark; Freeman, Tim; Downey, Gerald; Hadi, Abdul; Saeed, Mohammed

    2004-03-01

    DEET (diethyl-3-methylbenzamide), the widely used mosquito repellent, has the potential to prevent malarial infection but hitherto there has been no study demonstrating this possibility during normal everyday use. Mosbar, a repellent soap containing DEET, was promoted through social marketing in villages in eastern Afghanistan. This was followed up with a case-control study of effectiveness against malarial infection conducted through local clinics. Mosbar was purchased by 43% of households. Reported use of insecticide-treated nets (ITNs) was 65% among the control group. There was a strong association between Mosbar use and ITN use, as 81% of Mosbar users also possessed ITN. The use of Mosbar was associated with a 45% reduction in the odds of malaria (95% CI: -11% to 72%, P=0.08) after adjusting for ITN and other unmatched factors. Ownership of ITNs was associated with a 46% reduction in the odds of malaria (95% CI: 12% to 67%, P=0.013) after adjusting for Mosbar and other unmatched factors. The greatest reduction in the odds of malaria was associated with combined use of Mosbar and ITN (69% reduction, 95% CI: 28% to 87%, P=0.007). The association between recalled use of Mosbar 10 days ago (nearer the time of infection) and reduction in malarial infections (adjusted odds ratio 0.08, 95% CI: 0.01-0.61, P=0.001) was significantly stronger than that shown by current use of Mosbar. Most purchasers of Mosbar were satisfied with the product (74%), although a minority said they preferred to use only ITN (8%). The local mosquito vectors, Anopheles stephensi and A. nigerrimus, started biting shortly after dusk and continued biting until early morning. It was shown that Mosbar prevented biting throughout this period. In regions where mosquito vectors bite during evening and night, repellents could have a useful supplementary role to ITN and their use should be more widely encouraged.

  18. Disentangling woodland caribou movements in response to clearcuts and roads across temporal scales.

    Directory of Open Access Journals (Sweden)

    David Beauchesne

    Full Text Available Although prey species typically respond to the most limiting factors at coarse spatiotemporal scales while addressing biological requirements at finer scales, such behaviour may become challenging for species inhabiting human altered landscapes. We investigated how woodland caribou, a threatened species inhabiting North-American boreal forests, modified their fine-scale movements when confronted with forest management features (i.e. clearcuts and roads. We used GPS telemetry data collected between 2004 and 2010 on 49 female caribou in a managed area in Québec, Canada. Movements were studied using a use--availability design contrasting observed steps (i.e. line connecting two consecutive locations with random steps (i.e. proxy of immediate habitat availability. Although caribou mostly avoided disturbances, individuals nonetheless modulated their fine-scale response to disturbances on a daily and annual basis, potentially compromising between risk avoidance in periods of higher vulnerability (i.e. calving, early and late winter during the day and foraging activities in periods of higher energy requirements (i.e. spring, summer and rut during dusk/dawn and at night. The local context in which females moved was shown to influence their decision to cross clearcut edges and roads. Indeed, although females typically avoided crossing clearcut edges and roads at low densities, crossing rates were found to rapidly increase in greater disturbance densities. In some instance, however, females were less likely to cross edges and roads as densities increased. Females may then be trapped and forced to use disturbed habitats, known to be associated with higher predation risk. We believe that further increases in anthropogenic disturbances could exacerbate such behavioural responses and ultimately lead to population level consequences.

  19. Ascent trajectory optimization for stratospheric airship with thermal effects

    Science.gov (United States)

    Guo, Xiao; Zhu, Ming

    2013-09-01

    Ascent trajectory optimization with thermal effects is addressed for a stratospheric airship. Basic thermal characteristics of the stratospheric airship are introduced. Besides, the airship’s equations of motion are constructed by including the factors about aerodynamic force, added mass and wind profiles which are developed based on horizontal-wind model. For both minimum-time and minimum-energy flights during ascent, the trajectory optimization problem is described with the path and terminal constraints in different scenarios and then, is converted into a parameter optimization problem by a direct collocation method. Sparse Nonlinear OPTimizer(SNOPT) is employed as a nonlinear programming solver and two scenarios are adopted. The solutions obtained illustrate that the trajectories are greatly affected by the thermal behaviors which prolong the daytime minimum-time flights of about 20.8% compared with that of nighttime in scenario 1 and of about 10.5% in scenario 2. And there is the same trend for minimum-energy flights. For the energy consumption of minimum-time flights, 6% decrease is abstained in scenario 1 and 5% decrease in scenario 2. However, a few energy consumption reduction is achieved for minimum-energy flights. Solar radiation is the principal component and the natural wind also affects the thermal behaviors of stratospheric airship during ascent. The relationship between take-off time and performance of airship during ascent is discussed. it is found that the take-off time at dusk is best choice for stratospheric airship. And in addition, for saving energy, airship prefers to fly downwind.

  20. Combining Synthetic Human Odours and Low-Cost Electrocuting Grids to Attract and Kill Outdoor-Biting Mosquitoes: Field and Semi-Field Evaluation of an Improved Mosquito Landing Box.

    Directory of Open Access Journals (Sweden)

    Nancy S Matowo

    Full Text Available On-going malaria transmission is increasingly mediated by outdoor-biting vectors, especially where indoor insecticidal interventions such as long-lasting insecticide treated nets (LLINs are widespread. Often, the vectors are also physiologically resistant to insecticides, presenting major obstacles for elimination. We tested a combination of electrocuting grids with synthetic odours as an alternative killing mechanism against outdoor-biting mosquitoes.An odour-baited device, the Mosquito Landing Box (MLB, was improved by fitting it with low-cost electrocuting grids to instantly kill mosquitoes attracted to the odour lure, and automated photo switch to activate attractant-dispensing and mosquito-killing systems between dusk and dawn. MLBs fitted with one, two or three electrocuting grids were compared outdoors in a malaria endemic village in Tanzania, where vectors had lost susceptibility to pyrethroids. MLBs with three grids were also tested in a large semi-field cage (9.6 × 9.6 × 4.5m, to assess effects on biting-densities of laboratory-reared Anopheles arabiensis on volunteers sitting near MLBs.Significantly more mosquitoes were killed when MLBs had two or three grids, than one grid in wet and dry seasons (P<0.05. The MLBs were highly efficient against Mansonia species and malaria vector, An. arabiensis. Of all mosquitoes, 99% were non-blood fed, suggesting host-seeking status. In the semi-field, the MLBs reduced mean number of malaria mosquitoes attempting to bite humans fourfold.The improved odour-baited MLBs effectively kill outdoor-biting malaria vector mosquitoes that are behaviourally and physiologically resistant to insecticidal interventions e.g. LLINs. The MLBs reduce human-biting vector densities even when used close to humans, and are insecticide-free, hence potentially antiresistance. The devices could either be used as surveillance tools or complementary mosquito control interventions to accelerate malaria elimination where

  1. Mercury's Na Exosphere from MESSENGER Data

    Science.gov (United States)

    Killen, Rosemary M.; Burger, M. H.; Cassidy, T. A.; Sarantos, M.; Vervack, R. J.; McClintock, W. El; Merkel, A. W.; Sprague, A. L.; Solomon, S. C.

    2012-01-01

    MESSENGER entered orbit about Mercury on March 18, 2011. Since then, the Ultraviolet and Visible Spectrometer (UWS) channel of MESSENGER's Mercury Atmospheric and Surface Composition Spectrometer (MASCS) has been observing Mercury's exosphere nearly continuously. Daily measurements of Na brightness were fitted with non-uniform exospheric models. With Monte Carlo sampling we traced the trajectories of a representative number of test particles, generally one million per run per source process, until photoionization, escape from the gravitational well, or permanent sticking at the surface removed the atom from the simulation. Atoms were assumed to partially thermally accommodate on each encounter with the surface with accommodation coefficient 0.25. Runs for different assumed source processes are run separately, scaled and co-added. Once these model results were saved onto a 3D grid, we ran lines of sight from the MESSENGER spacecraft :0 infinity using the SPICE kernels and we computed brightness integrals. Note that only particles that contribute to the measurement can be constrained with our method. Atoms and molecules produced on the nightside must escape the shadow in order to scatter light if the excitation process is resonant-light scattering, as assumed here. The aggregate distribution of Na atoms fits a 1200 K gas, with a PSD distribution, along with a hotter component. Our models constrain the hot component, assumed to be impact vaporization, to be emitted with a 2500 K Maxwellian. Most orbits show a dawnside enhancement in the hot component broadly spread over the leading hemisphere. However, on some dates there is no dawn/dusk asymmetry. The portion of the hot/cold source appears to be highly variable.

  2. Towards a synthesis of substorm electrodynamics: HF radar and auroral observations

    Directory of Open Access Journals (Sweden)

    A. Grocott

    2006-12-01

    Full Text Available At 08:35 UT on 21 November 2004, the onset of an interval of substorm activity was captured in the southern hemisphere by the Far UltraViolet (FUV instrument on board the IMAGE spacecraft. This was accompanied by the onset of Pi2 activity and subsequent magnetic bays, evident in ground magnetic data from both hemispheres. Further intensifications were then observed in both the auroral and ground magnetic data over the following ~3 h. During this interval the fields-of-view of the two southern hemisphere Tasman International Geospace Enviroment Radars (TIGER moved through the evening sector towards midnight. Whilst initially low, the amount of backscatter from TIGER increased considerably during the early stages of the expansion phase such that by ~09:20 UT an enhanced dusk flow cell was clearly evident. During the expansion phase the equatorward portion of this flow cell developed into a narrow high-speed flow channel, indicative of the auroral and sub-auroral flows identified in previous studies (e.g. Freeman et al., 1992; Parkinson et al., 2003. At the same time, higher latitude transient flow features were observed and as the interval progressed the flow reversal region and Harang discontinuity became very well defined. Overall, this study has enabled the spatial and temporal development of many different elements of the substorm process to be resolved and placed within a simple conceptual framework of magnetospheric convection. Specifically, the detailed observations of ionospheric flows have illustrated the complex interplay between substorm electric fields and associated auroral dynamics. They have helped define the distinct nature of different substorm current systems such as the traditional substorm current wedge and the more equatorward currents associated with polarisation electric fields. Additionally, they have revealed a radar signature of nightside reconnection which provides the promise of quantifying nightside reconnection in a

  3. On the propagation of bubbles in the geomagnetic tail

    Directory of Open Access Journals (Sweden)

    J. Birn

    2004-04-01

    Full Text Available Using three-dimensional magnetohydrodynamic simulations, we investigate the propagation of low-entropy magnetic flux tubes ("bubbles" in the magnetotail. Our simulations address fundamental properties of the propagation and dynamics of such flux tubes rather than the actual formation process. We find that the early evolution, after a sudden reduction of pressure and entropy on a localized flux tube, is governed by re-establishing the balance of the total pressure in the dawn-dusk and north-south directions through compression on a time scale less than about 20s for the typical magnetotail. The compression returns the equatorial pressure to its original unperturbed value, due to the fact that the magnetic field contributes only little to the total pressure, while farther away from the equatorial plane the magnetic field compression dominates. As a consequence the pressure is no longer constant along a flux tube. The subsequent evolution is characterized by earthward propagation at speeds of the order of 200-400km/s, depending on the initial amount of depletion and the cross-tail extent of a bubble. Simple acceleration without depletion does not lead to significant earthward propagation. It hence seems that both the entropy reduction and the plasma acceleration play an important role in the generation of fast plasma flows and their propagation into the near tail. Earthward moving bubbles are found to be associated with field-aligned current systems, directed earthward on the dawnward edge and tailward on the duskward edge. This is consistent with current systems attributed to observed bursty bulk flows and their auroral effects.

    Key words. Magnetospheric physics (magnetospheric configuration and dynamics; magnetotail; plasma sheetnguage:

  4. [Net CO2 exchange and carbon isotope flux in Acacia mangium plantation].

    Science.gov (United States)

    Zou, Lu-Liu; Sun, Gu-Chou; Zhao, Ping; Cai, Xi-An; Zeng, Xiao-Ping; Wang, Quan

    2009-11-01

    By using stable carbon isotope technique, the leaf-level 13C discrimination was integrated to canopy-scale photosynthetic discrimination (Deltacanopy) through weighted the net CO2 assimilation (Anet) of sunlit and shaded leaves and the stand leaf area index (L) in an A. mangium plantation, and the carbon isotope fluxes from photosynthesis and respiration as well as their net exchange flux were obtained. There was an obvious diurnal variation in Deltacanopy, being lower at dawn and at noon time (18.47 per thousand and 19.87 per thousand, respectively) and the highest (21.21 per thousand) at dusk. From the end of November to next May, the Deltacanopy had an increasing trend, with an annual average of (20.37 +/- 0.29) per thousand. The carbon isotope ratios of CO2 from autotrophic respiration (excluding daytime foliar respiration) and heterotrophic respiration were respectively (- 28.70 +/- 0.75) per thousand and (- 26.75 +/- 1.3) per thousand in average. The delta13 C of nighttime ecosystem-respired CO2 in May was the lowest (-30.14 per thousand), while that in November was the highest (-28.01 per thousand). The carbon isotope flux of CO2 between A. mangium forest and atmosphere showed a midday peak of 178.5 and 217 micromol x m(-2) x s(-1) x per thousand in May and July, with the daily average of 638.4 and 873.2 micromol x m(-2) x s(-1) x per thousand, respectively. The carbon isotope flux of CO2 absorbed by canopy leaves was 1.6-2.5 times higher than that of CO2 emitted from respiration, suggesting that a large sum of CO2 was absorbed by A. mangium, which decreased the atmospheric CO2 concentration and improved the environment.

  5. Auroral counterpart of magnetic field dipolarizations in Saturn's tail

    Science.gov (United States)

    Jackman, C. M.; Badman, S. V.; Achilleos, N.; Bunce, E. J.; Cowley, S. W. H.; Radioti, A.; Grodent, D.; Dougherty, M. K.; Pryor, W.

    2012-04-01

    Following magnetic reconnection in a planetary magnetotail, newly closed field lines can be rapidly accelerated back towards the planet, becoming "dipolarized" in the process. At Saturn, dipolarizations can be initially identified in magnetometer data by looking for a southward turning of the magnetic field, indicating the transition from a radially stretched configuration to a more dipolar field topology. The highly stretched geometry of the kronian magnetotail lobes gives rise to a tail current which flows eastward (dusk to dawn) in the near equatorial plane across the centre of the tail. During reconnection and associated dipolarization of the field, the inner edge of this tail current can be diverted through the ionosphere, in a situation analogous to the substorm current wedge picture at Earth. We present a picture of the current circuit arising from this tail reconfiguration, and outline the equations which govern the field-current relationship. We show an example of a dipolarization identified in the Cassini magnetometer data and use this formalism to constrain the ionospheric current density that would arise for this example and the implications for auroral electron acceleration in regions of upward directed field-aligned current. We then present a separate example of data from the Cassini UVIS instrument where we observe small 'spots' of auroral emission lying near the main oval; features thought to be associated with dipolarizations in the tail. In the example shown, such auroral spots are the precursor to more intense activity associated with recurrent energisation via particle injections from the tail following reconnection. We conclude that dipolarizations in Saturn's magnetotail have an observable auroral counterpart, opening up the possibility to search for further examples and to use this auroral property as a remote proxy for tail reconnection.

  6. Bird colour vision: behavioural thresholds reveal receptor noise.

    Science.gov (United States)

    Olsson, Peter; Lind, Olle; Kelber, Almut

    2015-01-15

    Birds have impressive physiological adaptations for colour vision, including tetrachromacy and coloured oil droplets, yet it is not clear exactly how well birds can discriminate the reflecting object colours that they encounter in nature. With behavioural experiments, we determined colour discrimination thresholds of chickens in bright and dim light. We performed the experiments with two colour series, orange and green, covering two parts of chicken colour space. These experiments allowed us to compare behavioural results with model expectations and determine how different noise types limit colour discrimination. At intensities ranging from bright light to those corresponding to early dusk (250-10 cd m(-2)), we describe thresholds accurately by assuming a constant signal-to-noise ratio, in agreement with an invariant Weber fraction of Weber's law. Below this intensity, signal-to-noise ratio decreases and Weber's law is violated because photon-shot noise limits colour discrimination. In very dim light (below 0.05 cd m(-2) for the orange series or 0.2 cd m(-2) for the green series) colour discrimination is possibly constrained by dark noise, and the lowest intensity at which chickens can discriminate colours is 0.025 and 0.08 cd m(-2) for the orange and green series, respectively. Our results suggest that chickens use spatial pooling of cone outputs to mitigate photon-shot noise. Surprisingly, we found no difference between colour discrimination of chickens and humans tested with the same test in bright light. © 2015. Published by The Company of Biologists Ltd.

  7. Surface conductivity of Mercury provides current closure and may affect magnetospheric symmetry

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    P. Janhunen

    2004-04-01

    Full Text Available We study what effect a possible surface conductivity of Mercury has on the closure of magnetospheric currents by making six runs with a quasi-neutral hybrid simulation. The runs are otherwise identical but use different synthetic conductivity models: run 1 has a fully conducting planet, run 2 has a poorly conducting planet ( $sigma{=}10^{-8} Omega^{-1}$ m$^{-1}$ and runs 3-6 have one of the hemispheres either in the dawn-dusk or day-night directions, conducting well, the other one being conducting poorly. Although the surface conductivity is not known from observations, educated guesses easily give such conductivity values that magnetospheric currents may close partly within the planet, and as the conductivity depends heavily on the mineral composition of the surface, the possibility of significant horizontal variations cannot be easily excluded. The simulation results show that strong horizontal variations may produce modest magnetospheric asymmetries. Beyond the hybrid simulation, we also briefly discuss the possibility that in the nightside there may be a lack of surface electrons to carry downward current, which may act as a further source of surface-related magnetospheric asymmetry.

    Key words. Magnetospheric physics (planetary magnetospheres; current systems; solar wind-magnetosphere interactions.6

  8. Spatial distribution of Mercury's flux ropes and reconnection fronts: MESSENGER observations

    Science.gov (United States)

    Sun, W. J.; Fu, S. Y.; Slavin, J. A.; Raines, J. M.; Zong, Q. G.; Poh, G. K.; Zurbuchen, T. H.

    2016-08-01

    We perform a statistical study of flux ropes and reconnection fronts based on MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER) magnetic field and plasma observations to study the implications for the spatial distribution of reconnection sites in Mercury's near magnetotail. The results show important differences of temporal and spatial distributions as compared to Earth. We have surveyed the plasma sheet crossings between -2 RM and -3 RM downtail from the planet, i.e., the location of Near-Mercury Neutral Line (NMNL). Plasma sheets were defined to be regions with β ≥ 0.5. Using this definition, 39 flux ropes and 86 reconnection fronts were identified in the plasma sheet. At Mercury, the distributions of flux ropes and reconnection fronts show clear dawn-dusk asymmetry with much higher occurrence rate on the dawnside plasma sheet than on the duskside. This suggests that magnetic reconnection in Mercury's magnetotail occurs more frequently in the dawnside than in the duskside plasma sheet, which is different than the observations in Earth's magnetotail showing more reconnection signatures in the duskside plasma sheet. The distribution of plasma sheet thickness shows that plasma sheet near the midnight is the thinnest part and does not show obvious asymmetry. Thus, the reasons that cause magnetic reconnection to preferentially occur on the dawnside of the magnetotail at Mercury may not be the plasma sheet thickness and require further study. The peak occurrence rates of flux ropes and reconnection fronts in Mercury's plasma sheet are ~ 60 times higher than that of Earth's values, which we interpret to be due to the highly variable magnetospheric conditions at Mercury. Such higher occurrence rate of magnetic reconnection would generate more plasma flows in the dawnside plasma sheet than in the duskside. These plasma flows would mostly brake and initiate the substorm dipolarization on the postmidnight sector at Mercury rather than the

  9. Long-Term Variability of Precipitation of Charged Particles on Mercury's Surface

    Science.gov (United States)

    Benna, M.; Slavin, J. A.; Boardsen, S. A.; Baker, D. N.; Anderson, B. J.; Korth, H.; McClintock, W. E.; Schriver, D.; Travnicek, P. M.; Zurbuchen, T.; Raines, J. M.; Solomon, S. C.

    2012-12-01

    direction and magnitude. Finally, these models show that particle precipitations on the terminators are dominated by a dawn-dusk asymmetry that is mainly to the result of solar wind aberration.

  10. Repellent efficacy of DEET, MyggA, neem (Azedirachta indica) oil and chinaberry (Melia azedarach) oil against Anopheles arabiensis, the principal malaria vector in Ethiopia.

    Science.gov (United States)

    Abiy, Ephrem; Gebre-Michael, Teshome; Balkew, Meshesha; Medhin, Girmay

    2015-05-03

    In Ethiopia, Anopheles arabiensis is the main vector responsible for the transmission of malaria in the country and its control mainly involves application of indoor residual spraying (IRS) and use of insecticide-treated bed nets (ITNs). Although the role of repellents for reducing man-vector contact is documented in the literature, the response of An. arabiensis to repellents was not previously evaluated under field conditions in Ethiopia. The trial was conducted in Sodere village assessing the repellent activities of four repellents, of which, two of them were commercially available DEET (N, N-diethyl-1,3-methylbenzamide) and MyggA (p-methane diol) and the other two were laboratory- produced, 20% neem oil and 20% chinaberry oil. A 6 by 6 Latin square design was employed by involving six volunteers who received rotated treatments of repellents and the Ethiopian Niger seed, noog abyssinia (Guizotia abyssinia), and locally called as noog oil (diluents to the two plant oils). Each volunteer also served as control. Volunteers were positioned at a distance of 20-40 m from each other and each was treated with one of the repellents, Niger seed/noog/ oil or untreated. Landing mosquitoes were collected from dusk to down using tests tubes. The tests were done in three replicates. Both DEET and MyggA provided more than 96% protection. The mean protection time for DEET was 8 hrs while the time for MyggA was 6 hrs. Protection obtained from neem oil and chinaberry oil was almost similar (more than 70%), however, the complete protection time for neem was 3 hrs, while that of chinaberry oil was one hour. The commercial products and laboratory-produced repellents can be utilized by individuals to avoid contact with An. arabiensis in Ethiopia.

  11. Dark or short nights: differential latitudinal constraints in nestling provisioning patterns of a nocturnally hunting bird species.

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    Markéta Zárybnická

    Full Text Available In diurnal bird species, individuals breeding at high latitudes have larger broods than at lower latitudes, which has been linked to differences in the daily time available for foraging. However, it remains unclear how latitude is linked with parental investment in nocturnal species. Here, we investigate nestling provisioning rates of male Tengmalm's owls in two populations at different latitudes (Czech Republic 50 °N; Finland 63 °N with the help of cameras integrated into nest boxes. Clutch sizes were smaller in the Czech population (CZ: 5.1 ± 0.1; FIN: 6.6 ± 0.1, but given the higher nestling mortality in the Finnish population, the number of fledglings did not differ between the two populations (CZ: 3.5 ± 0.3; FIN: 3.9 ± 0.2. Nestling provisioning patterns varied within days, over the reproductive season and between the two sites. Males delivered most food at dusk and dawn, having peak delivery rates at sun angles of -11° to -15° at both sites, and males increased the prey delivery rates with higher nestling requirements. Given the longer nights during summer in the Czech Republic compared to Finland, Czech males only showed a small shift in their delivery peak during the night from -17° in April to -14° in July. In contrast, Finnish males shifted their peak of prey delivery from -11° in April to -1° in July. Consequently, Czech males had a longer hunting time per night around midsummer when feeding young (360 min than Finnish males (270 min. This suggests that nocturnal owl species in northern populations are constrained by the short nights during the breeding season, which can limit the number of young they can raise. Moreover, owls in northern populations are additionally constrained through the unpredictable changes in food availability between years, and both these factors are likely to influence the reproductive investment between populations.

  12. Behaviour of captive Ostrich chicks from 10 days to 5 months of age

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    Marina Freire Amado

    2011-07-01

    Full Text Available The behaviour of ostrich chicks bred in captivity was studied by using groups with 30 birds in five age groups: from 10 to 40 days of age; from 41 to 60 days of age; from 61 to 90 days of age; from 91 to 120 days of age and from 121 to 150 days of age. Six birds at each age were ringed around one of their feet and observed for four consecutive days for eight hours daily in three periods (in the morning, at noon and in the afternoon, following the "one-zero" method for sampling. The order for observation of behaviour of the six selected birds was performed randomly at every thirty minutes, totalling 16 periods or 80 minutes/bird/day. Fourteen types of behaviour were observed. There were differences among ages for behaviour like standing, walking, running, ingesting stones, ingesting feces, picking and attacking. Non-parametric-tests were used to analyse the behaviour according to age of the bird and to the periods of the day. There was a statistical difference between in the morning and at noon periods on behaviours standing, walking, eating ration and in litophagia, which were observed more frequently at the first hours of the day. When periods of the morning and afternoon were compared, the birds' age had a significant effect on behaviour sand bathing. When the periods noon/afternoon were compared, the behaviours which presented significant differences were walking, running, drinking water, eating ration, litophagia, coprophagia, dancing, sand bathing, whose occurrence was the highest during dusk. It was observed that the behaviour of young ostriches diverge according to the age and to day period.

  13. DN1(p) circadian neurons coordinate acute light and PDF inputs to produce robust daily behavior in Drosophila.

    Science.gov (United States)

    Zhang, Luoying; Chung, Brian Y; Lear, Bridget C; Kilman, Valerie L; Liu, Yixiao; Mahesh, Guruswamy; Meissner, Rose-Anne; Hardin, Paul E; Allada, Ravi

    2010-04-13

    Daily behaviors in animals are determined by the interplay between internal timing signals from circadian clocks and environmental stimuli such as light. How these signals are integrated to produce timely and adaptive behavior is unclear. The fruit fly Drosophila exhibits clock-driven activity increases that anticipate dawn and dusk and free-running rhythms under constant conditions. Flies also respond to the onset of light and dark with acute increases in activity. Mutants of a novel ion channel, narrow abdomen (na), lack a robust increase in activity in response to light and show reduced anticipatory behavior and free-running rhythms, providing a genetic link between photic responses and circadian clock function. We used tissue-specific rescue of na to demonstrate a role for approximately 16-20 circadian pacemaker neurons, a subset of the posterior dorsal neurons 1 (DN1(p)s), in mediating the acute response to the onset of light as well as morning anticipatory behavior. Circadian pacemaker neurons expressing the neuropeptide PIGMENT-DISPERSING FACTOR (PDF) are especially important for morning anticipation and free-running rhythms and send projections to the DN1(p)s. We also demonstrate that DN1(p)Pdfr expression is sufficient to rescue, at least partially, Pdfr morning anticipation defects as well as defects in free-running rhythms, including those in DN1 molecular clocks. Additionally, these DN1 clocks in wild-type flies are more strongly reset to timing changes in PDF clocks than other pacemaker neurons, suggesting that they are direct targets. Taking these results together, we demonstrate that the DN1(p)s lie at the nexus of PDF and photic signaling to produce appropriate daily behavior.

  14. ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and Its Implication to the Cross-Polar Cap Pedersen Currents

    Science.gov (United States)

    Le, Guan; Slavin, J. A.; Strangeway, Robert

    2011-01-01

    In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

  15. Cluster observes the Earth’s magnetopause: coordinated four-point magnetic field measurements

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    M. W. Dunlop

    Full Text Available The four-spacecraft Cluster mission has provided high-time resolution measurements of the magnetic field from closely maintained separation distances (200–600 km. Four-point coverage of the Earth’s magnetopause began on the 9 and 10 November 2000 when all spacecraft first exited the dusk-side magnetosphere at about 19:00 LT, providing extensive coverage of the near flank magnetosheath and magnetopause boundary layer on re-entry to the magnetosphere. The traversals on this occasion were caused by the arrival of an intense CME at the Earth, which produced a large compression of the magnetopause and high magnetic activity. The magnetopause traversals represent an unprecedented data set, allowing detailed analysis of the local magnetic structure (gradients and dynamics of the magnetopause boundary. By performing minimum variance analysis (MVA on the magnetic field data from all four spacecraft, we demonstrate that the magnetopause was planar on the scale of the spacecraft separation scales and that the transverse scale size of the magnetopause boundary layer was 1000–1100 km. We also show that the motion of the boundary (defined by the magnetic shear at the current layer, is changing over the sequence of spacecraft crossings so that acceleration of the magnetopause can be very high in this region of the magnetosphere. Indeed, the magnetopause speed reaches the order of 300 km/s in response to the arrival of the interplanetary shock. Using MVA coordinates, we have identified a number of magnetospheric and magnetosheath FTE signatures, which are sampled simultaneously by all spacecraft at different distances from and on either side of the magnetopause. The signatures show a variation of scale with distance from the boundary.

    Key words. Magnetospheric physics (magnetopause, cusp and boundary layers Space plasma physics (discontinuities; magnetic reconnection

  16. A two-dimensional global simulation study of inductive-dynamic magnetosphere-ionosphere coupling

    Science.gov (United States)

    Tu, Jiannan; Song, Paul

    2016-12-01

    We present the numerical methods and results of a global two-dimensional multifluid-collisional-Hall magnetohydrodynamic (MHD) simulation model of the ionosphere-thermosphere system, an extension of our one-dimensional three-fluid MHD model. The model solves, self-consistently, Maxwell's equations, continuity, momentum, and energy equations for multiple ion and neutral species incorporating photochemistry, collisions among the electron, ion and neutral species, and various heating sources in the energy equations. The inductive-dynamic approach (solving self-consistently Faraday's law and retaining inertia terms in the plasma momentum equations) used in the model retains all possible MHD waves, thus providing faithful physical explanation (not merely description) of the magnetosphere-ionosphere/thermosphere (M-IT) coupling. In the present study, we simulate the dawn-dusk cross-polar cap dynamic responses of the ionosphere to imposed magnetospheric convection. It is shown that the convection velocity at the top boundary launches velocity, magnetic, and electric perturbations propagating with the Alfvén speed toward the bottom of the ionosphere. Within the system, the waves experience reflection, penetration, and rereflection because of the inhomogeneity of the plasma conditions. The reflection of the Alfvén waves may cause overshoot (stronger than the imposed magnetospheric convection) of the plasma velocity in some regions. The simulation demonstrates dynamic propagation of the field-aligned currents and ionospheric electric field carried by the Alfvén waves, as well as formation of closure horizontal currents (Pedersen currents in the E region), indicating that in the dynamic stage the M-I coupling is via the Alfvén waves instead of field-aligned currents or electric field mapping as described in convectional M-I coupling models.

  17. Traffic collisions between electric mobility devices (wheelchairs) and motor vehicles: Accidents, hubris, or self-destructive behavior?

    Science.gov (United States)

    LaBan, Myron M; Nabity, Thomas S

    2010-07-01

    This study had its genesis in a personally observed collision between a motor vehicle and a motorized wheelchair (electric mobility device) on a busy street in the middle of the block at an unmarked crossing. To the observer, at the time, this appeared to be a suicidal act. This investigation was initiated to both delineate the number of these crashes nationally and understand this phenomena as a potentially planned act of self-destruction. An initial survey of police reports was immediately frustrated by an inability to separate motor vehicle and electric mobility device collisions from the much larger group that involved ambulatory citizens because both types were classified together as "pedestrian" accidents. Instead, the search engine NexisLexis was used to identify 107 newspaper articles each of which described a motor vehicle and electric mobility device accident. In the motor vehicle and electric mobility device collisions, men predominated women (3:1 ratio) with an average age of 56 yrs. Sixty of these accidents were fatal. Ninety-four percent involved an electric mobility device and 6% a manual wheelchair. In 50% of the cases, the motor vehicle was a truck, van, or sport utility vehicle. Fifty percent occurred at dusk or dawn or at night. The electric mobility device occupant was cited as the guilty party in 39% of the cases and the driver of the motor vehicle in 27%. Twenty percent were unwitnessed hit-and-run accidents, whereas "no fault" was found in 8% of the cases. Although many accidents do happen by chance, when an electric mobility device operator openly challenges busy traffic by attempting to traverse it in the middle of the block at an unmarked crossing, predisposing psychosocial factors must also be considered. Hubris or premeditated self-destructive behavior or both need to be explored as preeminent issues with reference to the prodromal of the "accident process."

  18. Down-tail mass loss by plasmoids in Jupiter's and Saturn's magnetospheres

    Science.gov (United States)

    Cowley, S. W. H.; Nichols, J. D.; Jackman, C. M.

    2015-08-01

    Recent estimates of the plasma mass-loss rates by the formation and down-tail propagation of plasmoids observed in the plasma sheet in Jupiter's and Saturn's magnetosphere fall short of inner moon source rates by at least an order of magnitude. Here we argue that on the time scale between large-scale disconnection events, ~15 h at Jupiter and ~45 h at Saturn, mass-loaded closed flux tubes will typically have stretched out a few hundred planetary radii down tail at speeds ~100-200 km s-1. Consequently, the "plasmoids" of order ~10 planetary radii in length observed at closer planetary distances represent only a small planetward portion of the overall structure that is disconnected and lost down tail. Plasmoid mass-loss estimates are then revised upward by around an order of magnitude, becoming comparable to the moon source values. Additional "hidden," e.g., small-scale, mass-loss processes of comparable strength may not then be required. The essentially continuous azimuthally flowing source plasma in the dusk sector is shown to correspond to a plasma sheet layer adjacent to the magnetopause of width typically ~10% of the distance to the magnetopause in that local time sector. This physical picture also provides a simple explanation for the asymmetry in the plasmoid bipolar field signature observed at both Jupiter and Saturn and predicts that the apparent plasmoid length will increase with distance down tail to a limit beyond a few hundred planetary radii where the full ~100-200 planetary radii structures will be observed.

  19. Behavioral Traits and Airport Type Affect Mammal Incidents with U.S. Civil Aircraft

    Science.gov (United States)

    Schwarz, Kristin B.; Belant, Jerrold L.; Martin, James A.; DeVault, Travis L.; Wang, Guiming

    2014-10-01

    Wildlife incidents with aircraft cost the United States (U.S.) civil aviation industry >US1.4 billion in estimated damages and loss of revenue from 1990 to 2009. Although terrestrial mammals represented only 2.3 % of wildlife incidents, damage to aircraft occurred in 59 % of mammal incidents. We examined mammal incidents (excluding bats) at all airports in the Federal Aviation Administration (FAA) National Wildlife Strike Database from 1990 to 2010 to characterize these incidents by airport type: Part-139 certified (certificated) and general aviation (GA). We also calculated relative hazard scores for species most frequently involved in incidents. We found certificated airports had more than twice as many incidents as GA airports. Incidents were most frequent in October ( n = 215 of 1,764 total) at certificated airports and November ( n = 111 of 741 total) at GA airports. Most (63.2 %) incidents at all airports ( n = 1,523) occurred at night but the greatest incident rate occurred at dusk (177.3 incidents/hr). More incidents with damage ( n = 1,594) occurred at GA airports (38.6 %) than certificated airports (19.0 %). Artiodactyla (even-toed ungulates) incidents incurred greatest (92.4 %) damage costs ( n = 326; US51.8 million) overall and mule deer ( Odocoileus hemionus) was the most hazardous species. Overall, relative hazard score increased with increasing log body mass. Frequency of incidents was influenced by species relative seasonal abundance and behavior. We recommend airport wildlife officials evaluate the risks mammal species pose to aircraft based on the hazard information we provide and consider prioritizing management strategies that emphasize reducing their occurrence on airport property.

  20. Rhythmic and sustained oscillations in metabolism and gene expression of Cyanothece sp. ATCC 51142 under constant light

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    Sandeep Bhupendra Gaudana

    2013-12-01

    Full Text Available Cyanobacteria, a group of photosynthetic prokaryotes, oscillate between day and night time metabolisms with concomitant oscillations in gene expression in response to light/dark cycles (LD. The oscillations in gene expression have been shown to sustain in constant light (LL with a free running period of 24 h in a model cyanobacterium Synechococcus elongatus PCC 7942. However, equivalent oscillations in metabolism are not reported under LL in this non-nitrogen fixing cyanobacterium. Here we focus on Cyanothece sp. ATCC 51142, a unicellular, nitrogen-fixing cyanobacterium known to temporally separate the processes of oxygenic photosynthesis and oxygen-sensitive nitrogen fixation. In a recent report, metabolism of Cyanothece 51142 has been shown to oscillate between photosynthetic and respiratory phases under LL with free running periods that are temperature dependent but significantly shorter than the circadian period. Further, the oscillations shift to circadian pattern at moderate cell densities that are concomitant with slower growth rates. Here we take this understanding forward and demonstrate that the utradian rhythm under LL sustains at much higher cell densities when grown under turbulent regimes that simulate flashing light effect. Our results suggest that the ultradian rhythm in metabolism may be needed to support higher carbon and nitrogen requirements of rapidly growing cells under LL. With a comprehensive Real time PCR based gene expression analysis we account for key regulatory interactions and demonstrate the interplay between clock genes and the genes of key metabolic pathways. Further, we observe that several genes that peak at dusk in Synechococcus peak at dawn in Cyanothece and vice versa. The circadian rhythm of this organism appears to be more robust with peaking of genes in anticipation of the ensuing photosynthetic and respiratory metabolic phases.

  1. Coordination of the maize transcriptome by a conserved circadian clock

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    Harmon Frank G

    2010-06-01

    Full Text Available Abstract Background The plant circadian clock orchestrates 24-hour rhythms in internal physiological processes to coordinate these activities with daily and seasonal changes in the environment. The circadian clock has a profound impact on many aspects of plant growth and development, including biomass accumulation and flowering time. Despite recent advances in understanding the circadian system of the model plant Arabidopsis thaliana, the contribution of the circadian oscillator to important agronomic traits in Zea mays and other cereals remains poorly defined. To address this deficit, this study investigated the transcriptional landscape of the maize circadian system. Results Since transcriptional regulation is a fundamental aspect of circadian systems, genes exhibiting circadian expression were identified in the sequenced maize inbred B73. Of the over 13,000 transcripts examined, approximately 10 percent displayed circadian expression patterns. The majority of cycling genes had peak expression at subjective dawn and dusk, similar to other plant circadian systems. The maize circadian clock organized co-regulation of genes participating in fundamental physiological processes, including photosynthesis, carbohydrate metabolism, cell wall biogenesis, and phytohormone biosynthesis pathways. Conclusions Circadian regulation of the maize genome was widespread and key genes in several major metabolic pathways had circadian expression waveforms. The maize circadian clock coordinated transcription to be coincident with oncoming day or night, which was consistent with the circadian oscillator acting to prepare the plant for these major recurring environmental changes. These findings highlighted the multiple processes in maize plants under circadian regulation and, as a result, provided insight into the important contribution this regulatory system makes to agronomic traits in maize and potentially other C4 plant species.

  2. Attraction and consumption of methyl eugenol by male Bactrocera umbrosa Fabricius (Diptera: Tephritidae) promotes conspecific sexual communication and mating performance.

    Science.gov (United States)

    Wee, S L; Abdul Munir, M Z; Hee, A K W

    2017-06-19

    The Artocarpus fruit fly, Bactrocera umbrosa (Fabricius) (Diptera: Tephritidae), is an oligophagous fruit pest infesting Moraceae fruits, including jackfruit (Artocarpus heterophyllus Lamarck), a fruit commodity of high value in Malaysia. The scarcity of fundamental biological, physiological and ecological information on this pest, particularly in relation to behavioural response to phytochemical lures, which are instrumental to the success of many area-wide fruit fly control and management programmes, underpins the need for studies on this much-underrated pest. The positive response of B. umbrosa males to methyl eugenol (ME), a highly potent phytochemical lure, which attracts mainly males of many Bactrocera species, was shown to increase with increasing age. As early as 7 days after emergence (DAE), ca. 22% of males had responded to ME and over 50% by 10 DAE, despite no occurrence of matings (i.e. the males were still sexually immature). Male attraction to ME peaked from 10 to 27 DAE, which corresponded with the flies' attainment of sexual maturity. In wind-tunnel assays during the dusk courtship period, ME-fed males exhibited earlier calling activity and attracted a significantly higher percentage of virgin females compared with ME-deprived males. ME-fed males enjoyed a higher mating success than ME-deprived males at 1-day post ME feeding in semi-field assays. ME consumption also promotes aggregation behaviour in B. umbrosa males, as demonstrated in wind-tunnel and semi-field assays. We suggest that ME plays a prominent role in promoting sexual communication and enhancing mating performance of the Artocarpus fruit fly, a finding that is congruent with previous reports on the consequences of ME acquisition by other economically important Bactrocera species.

  3. Comment on Lockwood and Davis, "On the longitudinal extent of magnetopause reconnection pulses"

    Science.gov (United States)

    Heikkila, W. J.

    1999-02-01

    Lockwood and Davis (1996) present a concise description of magnetopause reconnection pulses, with the claimed support of three types of observations: (1) flux transfer events (FTE), (2) poleward-moving auroral forms on the dayside, and (3) steps in cusp ion dispersion characteristics. However, there are a number of errors and misconceptions in the paper that make their conclusions untenable. They do not properly take account of the fact that the relevant processes operate in the presence of a plasma. They fail to notice that the source of energy (a dynamo with E · J0) in transient phenomena, since energy (or information) cannot travel faster than the group velocity of waves in the medium (here the Alfvén velocity VA). In short, Lockwood and Davis use the wrong contour in their attempt to evaluate the electromotive force (emf). This criticism goes beyond their article: a dynamo is not included in the usual definition of reconnection, only the reconnection load. Without an explicit source of energy in the assumed model, the idea of magnetic reconnection is improperly posed. Recent research has carried out a superposed epoch analysis of conditions near the dayside magnetopause and has found the dynamo and the load, both within the magnetopause current sheet. Since the magnetopause current is from dawn to dusk, the sign of E · J reflects the sign of the electric field. The electric field reverses, within the magnetopause; this can be discovered by an application of Lenz's law using the concept of erosion of the magnetopause. The net result is plasma transfer across the magnetopause to feed the low latitude boundary layer, at least partly on closed field lines, and viscous interaction as the mechanism by which solar wind plasma couples to the magnetosphere.

  4. Vocal activity of lesser galagos (Galago spp.) at zoos.

    Science.gov (United States)

    Schneiderová, Irena; Zouhar, Jan; Štefanská, Lucie; Bolfíková, Barbora Černá; Lhota, Stanislav; Brandl, Pavel

    2016-01-01

    Almost nothing is known about the natural vocal behavior of lesser galagos living in zoos. This is perhaps because they are usually kept in nocturnal exhibits separated from the visitors by a transparent and acoustically insulating glass barrier. The aim of the present study was therefore to fill this gap in knowledge of the vocal behavior of lesser galagos from zoos. This knowledge might be beneficial because the vocalizations of these small primates can be used for species determination. We performed a 10-day-long acoustic monitoring of vocal activity in each of seven various groups of Galago senegalensis and G. moholi living at four zoos. We quantitatively evaluated the occurrence of four loud vocalization types present in both species, including the most species-specific advertisement call. We found that qualitative as well as quantitative differences exist in the vocal behavior of the studied groups. We confirmed that the observed vocalization types can be collected from lesser galagos living at zoos, and the success can be increased by selecting larger and more diverse groups. We found two distinct patterns of diel vocal activity in the most vocally active groups. G. senegalensis groups were most vocally active at the beginning and at the end of their activity period, whereas one G. moholi group showed an opposite pattern. The latter is surprising, as it is generally accepted that lesser galagos emit advertisement calls especially at dawn and dusk, i.e., at the beginning and at the end of their diel activity. © 2016 Wiley Periodicals, Inc.

  5. Cuelure but not zingerone make the sex pheromone of male Bactrocera tryoni (Tephritidae: Diptera) more attractive to females.

    Science.gov (United States)

    Kumaran, Nagalingam; Hayes, R Andrew; Clarke, Anthony R

    2014-09-01

    In tephritid fruit flies of the genus Bactrocera Macquart, a group of plant derived compounds (sensu amplo 'male lures') enhance the mating success of males that have consumed them. For flies responding to the male lure methyl eugenol, this is due to the accumulation of chemicals derived from the male lure in the male rectal gland (site of pheromone synthesis) and the subsequent release of an attractive pheromone. Cuelure, raspberry ketone and zingerone are a second, related group of male lures to which many Bactrocera species respond. Raspberry ketone and cuelure are both known to accumulate in the rectal gland of males as raspberry ketone, but it is not known if the emitted male pheromone is subsequently altered in complexity or is more attractive to females. Using Bactrocera tryoni as our test insect, and cuelure and zingerone as our test chemicals, we assess: (i) lure accumulation in the rectal gland; (ii) if the lures are released exclusively in association with the male pheromone; and (iii) if the pheromone of lure-fed males is more attractive to females than the pheromone of lure-unfed males. As previously documented, we found cuelure was stored in its hydroxyl form of raspberry ketone, while zingerone was stored largely in an unaltered state. Small but consistent amounts of raspberry ketone and β-(4-hydroxy-3-methoxyphenyl)-propionic acid were also detected in zingerone-fed flies. Males released the ingested lures or their analogues, along with endogenous pheromone chemicals, only during the dusk courtship period. More females responded to squashed rectal glands extracted from flies fed on cuelure than to glands from control flies, while more females responded to the pheromone of calling cuelure-fed males than to control males. The response to zingerone treatments in both cases was not different from the control. The results show that male B. tryoni release ingested lures as part of their pheromone blend and, at least for cuelure, this attracts more

  6. Fine-scale pathways used by adult sea lampreys during riverine spawning migrations

    Science.gov (United States)

    Holbrook, Christopher; Bergstedt, Roger A.; Adams, Noah S.; Hatton, Tyson; McLaughlin, Robert L.

    2015-01-01

    Better knowledge of upstream migratory patterns of spawning Sea Lampreys Petromyzon marinus, an invasive species in the Great Lakes, is needed to improve trapping for population control and assessment. Although trapping of adult Sea Lampreys provides the basis for estimates of lake-wide abundance that are used to evaluate the Sea Lamprey control program, traps have only been operated at dams due to insufficient knowledge of Sea Lamprey behavior in unobstructed channels. Acoustic telemetry and radiotelemetry were used to obtain movement tracks for 23 Sea Lampreys in 2008 and 18 Sea Lampreys in 2009 at two locations in the Mississagi River, Ontario. Cabled hydrophone arrays provided two-dimensional geographic positions from acoustic transmitters at 3-s intervals; depth-encoded radio tag detections provided depths. Upstream movements occurred at dusk or during the night (2015–0318 hours). Sea Lampreys were closely associated with the river bottom and showed some preference to move near banks in shallow glide habitats, suggesting that bottom-oriented gears could selectively target adult Sea Lampreys in some habitats. However, Sea Lampreys were broadly distributed across the river channel, suggesting that the capture efficiency of nets and traps in open channels would depend heavily on the proportion of the channel width covered. Lack of vertical movements into the water column may have reflected lamprey preference for low water velocities, suggesting that energy conservation was more beneficial for lampreys than was vertical searching in rivers. Improved understanding of Sea Lamprey movement will assist in the development of improved capture strategies for their assessment and control in the Great Lakes.

  7. Effect of night time-intervals, height of traps and lunar phases on sand fly collection in a highly endemic area for canine leishmaniasis.

    Science.gov (United States)

    Gaglio, Gabriella; Brianti, Emanuele; Napoli, Ettore; Falsone, Luigi; Dantas-Torres, Filipe; Tarallo, Viviana D; Otranto, Domenico; Giannetto, Salvatore

    2014-05-01

    The activity of phlebotomine sand flies was monitored in a sub-urban area of Sicily in order to acquire data on seasonality and to elucidate the effect of the night time-intervals, height of traps from ground and lunar phases on the abundance of the capture. The study was conducted in the farm of the University of Messina (Italy). Light traps were placed as in the following: biweekly, from dusk to dawn, and from May to November; for three consecutive nights from 18:00 to 6:00, with the net bag being changed every 2h; for 30 days, at different heights from 18:00 to 6:00. A total of five species (i.e., Phlebotomus perniciosus, Phlebotomus neglectus, Phlebotomus sergenti, Phlebotomus perfiliewi, and Sergentomyia minuta), three of which are proven vectors of Leishmania infantum, were captured. The most abundant species was P. perniciosus (73.3%) followed by S. minuta (23.3%). The highest number of phlebotomine sand flies was collected in August and September with a peak of collection recorded in the evening (i.e., from 20:01 to 22.00). The number of phlebotomine sand flies collected at 50cm above the ground was significantly higher (P=0.041) than that captured at 150cm. Results of this study shed light on the ecology of main phlebotomine species in the Mediterranean area, and on the influence of some factors, such as time and height of traps, on the light trap capture efficiency.

  8. MHD models compared with Artemis observations at -60 Re

    Science.gov (United States)

    Gencturk Akay, Iklim; Sibeck, David; Angelopoulos, Vassilis; Kaymaz, Zerefsan; Kuznetsova, Maria

    2016-07-01

    The distant magnetotail has been one of the least studied magnetic regions of the Earth's magnetosphere compared to the other near Earth both dayside and nightside magnetospheric regions owing to the limited number of spacecraft observations. Since 2011, ARTEMIS spacecraft give an excellent opportunity to study the magnetotail at lunar distances in terms of data quality and parameter space. This also gives opportunities to improve the magnetotail models at -60 Re and encourages the modelling studies of the distant magnetotail. Using ARTEMIS data in distant magnetotail, we create magnetic field and plasma flow vector maps in different planes and separated with IMF orientation to understand the magnetotail dynamics at this distance. For this study, we use CCMC's Run-on-Request resources of the MHD models; specifically SWMF-BATS-R-US, OpenGGCM, and LFM and perform the similar analysis with the models. Our main purpose in this study is to measure the performance of the MHD models at -60 Re distant magnetotail by comparing the model results with Artemis observations. In the literature, such a comprehensive comparative study is lacking in the distant tail. Preliminary results show that in general all three models underestimate the magnetic field structure while overestimating the flow speed. In the cross-sectional view, LFM seems to produce the better agreement with the observations. A clear dipolar magnetic field structure is seen with dawn-dusk asymmetry in all models owing to slight positive IMF By but the effect was found to be exaggerated. All models show tailward flows at this distance of the magnetotail, most possibly owing to the magnetic reconnection at the near Earth tail distances. A detailed comparison of several tail characteristics from the models will be presented and discussions will be given with respect to the observations from Artemis at this distance.

  9. A web-based survey of horse owners' perceptions and network analysis of horse movements relating to African horse sickness distribution in Namibia and South Africa.

    Science.gov (United States)

    Liebenberg, Danica; Piketh, Stuart; van Hamburg, Huib

    2016-06-01

    Africa horse sickness (AHS) is the most lethal infectious non-contagious horse disease and has accordingly been declared notifiable by the World Organisation for Animal Health. AHS is endemic to sub-Saharan Africa and causes considerable losses to the equestrian industry. The effect of diseases in livestock on socio-economic factors is well researched, but the effect of anthropogenic factors on the distribution of a disease is poorly understood. The purpose of the study was to assess Namibian and South African horse owners' perceptions and the effect of horse movement on AHS distribution. A cross-sectional study was conducted to collect information from horse owners in Namibia and South Africa. To that end 'Fluid survey' was used for survey development. The survey was launched on Facebook and the link shared to horse related focus groups in Namibia and South Africa. A total of 508 responses were collected during the survey period. Of the 417 completed questionnaires received, 22% were from Namibia and 78% from South Africa. The participants comprised of 71% social and 29% professional riders. The most popular precautionary measures used, in addition to vaccination, were chemical repellents (64%) and stabling of horses during dusk and dawn (59%). A network analysis was performed in Gephi 0.8.2.B to illustrate the movement of horses between countries and districts/provinces. Network analysis results indicate that areas with the highest movement of horses corresponded to the areas with a high occurrence of AHS. Although 93% of the participants were aware that AHS is a notifiable and controlled disease, the process and efficiency of reporting is mostly unknown. With this snapshot of horse owners' perceptions and the effect of horse movement on the distribution of AHS, it is clear that a more holistic approach is needed. To that end, all environmental and social factors must be taken into account in effective management strategies.

  10. Fauna of phlebotomine sand flies (Diptera, Psychodidae in areas with endemic American cutaneous leishmaniasis in the State of Mato Grosso do Sul, Brazil

    Directory of Open Access Journals (Sweden)

    Paulo Silva de Almeida

    2013-03-01

    Full Text Available Fauna of phlebotomine sand flies (Diptera, Psychodidae in areas with endemic American cutaneous leishmaniasis in the State of Mato Grosso do Sul, Brazil. The aim of this study was to investigate the ecological aspects of the main vectors of American cutaneous leishmaniasis (ACL in four monitoring stations situated in the municipalities of Naviraí, Nova Andradina, Novo Horizonte do Sul and Rio Verde de Mato Grosso. For each monitoring station, the captures of sand flies were undertaken each month from July 2008 to June 2010 using CDC and Shannon traps. The CDC traps were installed simultaneously for three consecutive nights in three collection sites: intradomicile, peridomicile and edge of the forest. A Shannon trap was installed from dusk to 10 pm, inside the forest, one night per month. A total of 7,651 sand flies belonging to nine genera and twenty-nine species were captured. Nyssomyia neivai (52.95%, Psathyromyia hermanlenti (10.91%, Psathyromyia runoides (9.16%, Nyssomyia whitmani (7.95%, Psathyromyia aragaoi (4. 89%, Nyssomyia antunesi (3.14% and Evandromyia bourrouli (2.20% were the most frequent species. Approximately 65% of the sand flies were collected in the forest environment. The municipalities presented significantly different indexes of species diversity. Naviraí presented the lowest species diversity index, however, it showed the highest abundance. Novo Horizonte do Sul had the highest species diversity index, but the lowest abundance (< 5%. It is noteworthy the occurrence of vector species of Leishmania in the areas studied, especially in Naviraí, where Ny. neivai presented high frequencies which may explain the increased number of ACL cases in this municipality.

  11. Seasonal patterns in the nocturnal distributionand behavior of the mesopelagic fish Maurolicus muelleri at high latitudes

    KAUST Repository

    Prihartato, Perdana

    2015-02-17

    Acoustic scattering layers (SL) ascribed to pearlside Maurolicus muelleri were studied in Masfjorden, Norway, using upward-looking echo sounders cabled to shore for continuous long-term measurements. The acoustic studies were accompanied by continuous measurements of surface light and supplemented with intermittent field campaigns. From autumn to spring, young M. muelleri formed an SL in the upper ∼75 to 150 m in the daytime, characterized by migration to near-surface water near dusk, subsequent \\'midnight sinking\\', followed by a dawn ascent before a return to the daytime habitat. Light levels were ∼1 order of magnitude lower during the dawn ascent than for ascent in the afternoon, with the latter terminating before fish reached upper layers on ∼1/3 of the nights from late November to mid-April. Adults showed less tendency of migration during autumn and winter, until the SLs of young and adults merged in late spring, and thereafter displayed coherent migration behavior. The midnight sinking became progressively deeper from autumn to winter but was strongly reduced from mid-May when the darkest nocturnal light intensity (PAR) at the surface was above 10-3 μmol m-2 s-1. The pearlside took on schooling in upper waters during the even lighter nights in early June, with minimum light of ∼5 × 10-3 to 10-1 μmol m-2 s-1 at the surface. Nocturnal schooling ceased in early July, and midnight sinking reappeared in mid-August. We suggest that the strong variation in nocturnal light intensity at high latitudes provides changing trade-offs between visual foraging and avoiding predators and hence varying time budgets for feeding in the upper, productive layers.

  12. Double-cusp simulation during northward IMF using 3D PIC global code

    Science.gov (United States)

    Esmaeili, Amin; Kalaee, Mohammad Javad

    2017-07-01

    The cusp has important effects on the transportation of particles and their energy from the solar wind to the magnetosphere, and ionosphere, and high-altitude atmosphere. The cusp can be considered to be a part of the magnetospheric boundary layer with weaker magnetic fields. It has been studied since 1971 by different satellite observations. Despite many years of investigation, some problems, such as the boundaries, shapes, and method of construction, remain to be solved. The double cusp was first reported by Wing using the observation of the DMSP satellite. He also compared the results of observations with the results of a 2D MHD simulation. In this study, by performing simulations and analyzing the results, we report the observation of a V-shaped double-cusp structure under the northward Interplanetary Magnetic Field (IMF). In our simulation, the double cusp was seen only for electrons, although a weak double cusp was observed for ions as well. We showed that this double cusp occurred because of electron precipitation from different sources of solar wind and magnetosphere with different magnetic field strengths. In previous studies of the double cusp, there were debates on its spatial structure or on its temporal behavior due to the cusp movement caused by the sharp solar wind effects on the magnetosphere shape. Here we report the spatial detection of the double cusp similar to the one observed by the DMSP satellite, but for the northward IMF case. Also, we investigate the asymmetry along the dawn-dusk side of the magnetosphere using our 3D PIC simulation code.

  13. Magnetotail Structure and its Internal Particle Dynamics During Northward IMF

    Science.gov (United States)

    Ashour-Abdalla, M.; Raeder, J.; El-Alaoui, M.; Peroomian, V.

    1998-01-01

    This study uses Global magnetohydrodynamic (MHD) simulations driven by solar wind data along with Geotail observations of the magnetotail to investigate the magnetotail's response to changes in the interplanetary magnetic field (IMF); observed events used in the study occurred on March 29, 1993 and February 9, 1995. For events from February 9, 1995, we also use the time-dependent MHD magnetic and electric fields and the large-scale kinetic (LSK) technique to examine changes in the Geotail ion velocity distributions. Our MHD simulation shows that on March 29, 1993, during a long period of steady northward IMF, the tail was strongly squeezed and twisted around the Sun-Earth axis in response to variations in the IMF B(sub y) component. The mixed (magnetotail and magnetosheath) plasma observed by Geotail results from the spacecraft's close proximity to the magnetopause and its frequent crossings of this boundary. In our second example (February 9, 1995) the IMF was also steady and northward, and in addition had a significant B(sub y) component. Again the magnetotail was twisted, but not as strongly as on March 29, 1993. The Geotail spacecraft, located approximately 30 R(sub E) downtail, observed highly structured ion distribution functions. Using the time-dependent LSK technique, we investigate the ion sources and acceleration mechanisms affecting the Geotail distribution functions during this interval. At 1325 UT most ions are found to enter the magnetosphere on the dusk side earthward of Geotail with a secondary source on the dawn side in the low latitude boundary layer (LLBL). A small percentage come from the ionosphere. By 1347 UT the majority of the ions come from the dawn side LLBL. The distribution functions measured during the later time interval are much warmer, mainly because particles reaching the spacecraft from the dawn side are affected by nonadiabatic scattering and acceleration in the neutral sheet.

  14. What doesn't kill you makes you wary? Effect of repeated culling on the behaviour of an invasive predator.

    Directory of Open Access Journals (Sweden)

    Isabelle M Côté

    Full Text Available As a result of being hunted, animals often alter their behaviour in ways that make future encounters with predators less likely. When hunting is carried out for conservation, for example to control invasive species, these behavioural changes can inadvertently impede the success of future efforts. We examined the effects of repeated culling by spearing on the behaviour of invasive predatory lionfish (Pterois volitans/miles on Bahamian coral reef patches. We compared the extent of concealment and activity levels of lionfish at dawn and midday on 16 coral reef patches off Eleuthera, The Bahamas. Eight of the patches had been subjected to regular daytime removals of lionfish by spearing for two years. We also estimated the distance at which lionfish became alert to slowly approaching divers on culled and unculled reef patches. Lionfish on culled reefs were less active and hid deeper within the reef during the day than lionfish on patches where no culling had occurred. There were no differences at dawn when removals do not take place. Lionfish on culled reefs also adopted an alert posture at a greater distance from divers than lionfish on unculled reefs. More crepuscular activity likely leads to greater encounter rates by lionfish with more native fish species because the abundance of reef fish outside of shelters typically peaks at dawn and dusk. Hiding deeper within the reef could also make remaining lionfish less likely to be encountered and more difficult to catch by spearfishers during culling efforts. Shifts in the behaviour of hunted invasive animals might be common and they have implications both for the impact of invasive species and for the design and success of invasive control programs.

  15. M-I coupling across the Harang reversal during storm--substorm activity driven by an interplanetry ICMEs

    Science.gov (United States)

    Farrugia, C. J.; Sandholt, P. E.; Denig, W. F.

    2013-12-01

    By ground - satellite conjunctions across the auroral oval at dusk we study events of dynamical magnetosphere--ionosphere (M-I) coupling from the plasma sheet - ring current system via R1 and R2 field-aligned currents (FACs) during auroral electrojet activations appearing on the poleward and equatorward sides of the Harang reversal (HR), respectively. The interval of ICME passage at Earth we study is characterized by repetitive substorm activity appearing as a series of westward expansions--eastward retreats of the westward electrojet (WEJ) across the 1800 MLT meridian. Harang region-north (HR-N) is characterized by R1 FAC closure, WEJ activity, poleward boundary intensifications (PBIs) - equatorward - moving auroral streamers (inverted V - arcs), and (at different times) poleward auroral expansions. Harang region-south (HR-S) is characterized by R2 FAC closure leading to eastward electrojet (EEJ) activity and precipitation in the southern auroral branch. Using this approach we documented the detailed temporal evolution of polar cap convection, as derived from the PCN index, in relation to direct observations of the dynamical behaviour of the two basic branches of the substorm current system, i. e. the R2 FAC coupling from the partial ring current (PRC) and the R1 FAC coupling from the plasma sheet. We distinguish between two activity levels: (i) major AL-excursions beyond -1000 nT (accompanied by large-scale field dipolarizations in the inner magnetotail), followed by SYM-H dips (plasma injections enhancing the PRC) and R2 FAC - EEJ enhancements, and (ii) partial AL - recovery (AL within -300 to -600 nT) characterized by a series of M - I coupling events with manifestations on both sides of the HR, including streamer events in HR-N, leading to equatorward/poleward motions of the HR boundary.

  16. Analysis of propagation delays of compressional Pi 2 waves between geosynchronous altitude and low latitudes

    Science.gov (United States)

    Imajo, Shun; Yumoto, Kiyohumi; Uozumi, Teiji; Kawano, Hideaki; Abe, Shuji; Ikeda, Akihiro; Koga, Kiyokazu; Matsumoto, Haruhisa; Obara, Takahiro; Marshall, Richard; Akulichev, Victor A.; Mahrous, Ayman; Liedloff, Adam; Yoshikawa, Akimasa

    2014-12-01

    The propagation of compressional Pi 2 waves in the inner magnetosphere is investigated by analyzing the onset delay times between the ground and the geosynchronous altitude. We use the compressional component (northward) of magnetic data from low-latitude stations and the geosynchronous satellite ETS-VIII (GMLat. = -10.8°, GMLon. = 217.5°). The onset delays are determined by a cross-correlation analysis, and we analyzed the events with high waveform correlations (correlation coefficient greater than 0.75). Some of these high-correlation events have the properties of propagating waves; Pi 2 waveforms at the ground stations and the satellite were synchronized with each other when the data were shifted by onset delays. The results of the statistical analysis show that 87% of the Pi 2 onsets at a ground station (Kuju, GMLat. = 26.13°, GMLon. = 202.96°) were delayed from the Pi 2 onsets at ETS-VIII, and the average of the delay times was 29 sec. This clearly shows Pi 2 onsets (initial perturbations of Pi 2) propagated from the geosynchronous altitude to the low-latitude ground. The delay times tended to be larger around the midnight sector than around the dawn and dusk sectors. These results are consistent with two-dimensional propagation of fast waves estimated by the model of Uozumi et al. (J Geophys Res 114:A11207, 2009). The delay times are nearly identical to the travel time of fast waves from geosynchronous altitude to the low-latitude ground, and the local time variation of the delay shows the azimuthal propagation along the geosynchronous orbit. We conclude that the initial compressional perturbations of Pi 2 waves propagate radially and longitudinally as a fast wave in the inner magnetosphere.

  17. Validation of the stream function method used for reconstruction of experimental ionospheric convection patterns

    Directory of Open Access Journals (Sweden)

    P.L. Israelevich

    Full Text Available In this study we test a stream function method suggested by Israelevich and Ershkovich for instantaneous reconstruction of global, high-latitude ionospheric convection patterns from a limited set of experimental observations, namely, from the electric field or ion drift velocity vector measurements taken along two polar satellite orbits only. These two satellite passes subdivide the polar cap into several adjacent areas. Measured electric fields or ion drifts can be considered as boundary conditions (together with the zero electric potential condition at the low-latitude boundary for those areas, and the entire ionospheric convection pattern can be reconstructed as a solution of the boundary value problem for the stream function without any preliminary information on ionospheric conductivities. In order to validate the stream function method, we utilized the IZMIRAN electrodynamic model (IZMEM recently calibrated by the DMSP ionospheric electrostatic potential observations. For the sake of simplicity, we took the modeled electric fields along the noon-midnight and dawn-dusk meridians as the boundary conditions. Then, the solution(s of the boundary value problem (i.e., a reconstructed potential distribution over the entire polar region is compared with the original IZMEM/DMSP electric potential distribution(s, as well as with the various cross cuts of the polar cap. It is found that reconstructed convection patterns are in good agreement with the original modelled patterns in both the northern and southern polar caps. The analysis is carried out for the winter and summer conditions, as well as for a number of configurations of the interplanetary magnetic field.

    Key words: Ionosphere (electric fields and currents; plasma convection; modelling and forecasting

  18. Earth's Magnetosphere Impinged by Interplanetary Shocks of Different Orientations

    Institute of Scientific and Technical Information of China (English)

    GUO Xiao-Cheng; HU You-Qiu; WANG Chi

    2005-01-01

    @@ Using a recently developed PPMLR-MHD code, we carry out a global numerical simulation of the interaction between interplanetary shocks and Earth's magnetosphere. The initial magnetosphere is in a quasi-steady state,embedded in a uniform solar wind and a spiral interplanetary magnetic field (IMF). An interplanetary (IP)shock interacts in turn with the bow shock, the magnetosheath, the magnetopause, and the magnetosphere, and changes the magnetosphere in shape and structure, and the distribution of the electric current and potential in the ionosphere as well. A preliminary comparison is made between two IP shocks of the same solar wind dynamic pressure and a vanishing IMF Bz on the downstream side, but with different propagation directions, one parallel and the other oblique to the Sun-Earth line. The numerical results show that both shocks cause a compression of the magnetosphere, an enhancement of magnetic field strength and field-aligned current in the magnetosphere, and an increase of the dawn-dusk electric potential drops across the polar ionosphere. Moreover, the magnetosphereionosphere system approaches a similar quasi-steady state after the interaction, for the downstream states are very close for the two shocks. However, the evolution processes of the system are remarkably different during the interaction with the two shocks of different orientations. The shock with the normal oblique to the Sun-Earth line results in a much longer evolution time for the system. This demonstrates that the shock orientation plays an important role in determining the associated geophysical effects and interpreting multisatellite observations of IP shock-magnetosphere interaction events.

  19. Numerical analysis of global ionospheric current system including the effect of equatorial enhancement

    Directory of Open Access Journals (Sweden)

    S. Tsunomura

    Full Text Available A modeling method is proposed to derive a two-dimensional ionospheric layer conductivity, which is appropriate to obtain a realistic solution of the polar-originating ionospheric current system including equatorial enhancement. The model can be obtained by modifying the conventional, thin shell conductivity model. It is shown that the modification for one of the non-diagonal terms (Σθφ in the conductivity tensor near the equatorial region is very important; the term influences the profile of the ionospheric electric field around the equator drastically. The proposed model can reproduce well the results representing the observed electric and magnetic field signatures of geomagnetic sudden commencement. The new model is applied to two factors concerning polar-originating ionospheric current systems. First, the latitudinal profile of the DP2 amplitude in the daytime is examined, changing the canceling rate for the dawn-to-dusk electric field by the region 2 field-aligned current. It is shown that the equatorial enhancement would not appear when the ratio of the total amount of the region 2 field-aligned current to that of region 1 exceeds 0.5. Second, the north-south asymmetry of the magnetic fields in the summer solstice condition of the ionospheric conductivity is examined by calculating the global ionospheric current system covering both hemispheres simultaneously. It is shown that the positive relationship between the magnitudes of high latitude magnetic fields and the conductivity is clearly seen if a voltage generator is given as the source, while the relationship is vague or even reversed for a current generator. The new model, based on the International Reference Ionosphere (IRI model, can be applied to further investigations in the quantitative analysis of the magnetosphere-ionosphere coupling problems.

    Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionosphere

  20. Multi-instrumentation observations of a transpolar arc in the northern hemisphere

    Directory of Open Access Journals (Sweden)

    A. Goudarzi

    2008-02-01

    Full Text Available A transpolar arc was imaged by the FUV instrument on the IMAGE spacecraft during a 3-h interval on 5 February 2002. Observations indicate that a burst of reconnection in the geomagnetic tail, which was not associated with a substorm, was responsible for the formation of the arc. The arc initially formed across the central polar cap, extending from near midnight to noon such that the polar cap was approximately divided in half. The subsequent motion of the arc was controlled by the amount of open flux being added to the dawn sector cap from a magnetopause reconnection site on the post-noon side of the magnetosphere. The dayside reconnection happened during a period when the IMF By component was dominant, although the Bz component initially remained positive, and resulted in strong westward azimuthal flows in the noon sector. The arc continued to move towards the duskside auroral oval after the IMF Bz turned southward. A keogram of the FUV/WIC auroral observations along the dawn-dusk meridian provides further evidence of the expansion and contraction of the polar cap during the period in which different IMF orientations occurred. Furthermore, comparing images from IMAGE and ionospheric convection flow from SuperDARN measurements, vortical convection flows occurred exactly at the time and location of the formation of the transpolar arc and subsequently followed the head of the transpolar arc as it moved across the polar cap. The observations are consistent with the prediction of a recent model for the formation of the transpolar cap by the closure of open flux in the geomagnetic tail, and its subsequent motion through changes in the open flux distribution within the polar cap.

  1. Martian Sunrise at Utopia Planitia

    Science.gov (United States)

    1978-01-01

    A Martian sunrise was captured in this Viking 2 Lander picture taken June 14, 1978, at the spacecraft's Utopia Planitia landing site. The data composing this image were acquired just as the Sun peaked over the horizon on the Lander's 631st sol (Martian solar day). Pictures taken at dawn (or dusk) are quite dark except where the sky is brightened above the Sun's position. The glow in the sky results as light from the Sun is scattered and preferentially absorbed by tiny particles of dust and ice in the atmosphere. When the Viking cameras are calibrated for darker scenes, the 'sky glow' tends to saturate their sensitivity and produce the bright regions seen here. The 'banding' and color separation effects are also artifacts, rather than real features, and are introduced because the cameras are not able to record continuous gradations of light. The cameras must represent such gradations in steps (bands) of brightness and color, and the process sometimes produces some 'false' colors within the bands. The scattering of light closest to the Sun's position tends to enhance blue wavelengths. The narrowing sky glow nearer the horizon above the Sun's position occurs as a result of light extinction. At that elevation, the optical path of sunlight through the atmosphere is at its longest penetration angle, and a substantial portion of the light is simply prevented from reaching the cameras by the dust, ice particles and other material in its way.NASA's Langley Research Center was the primary and extended mission manager; JPL assumed management for continued mission operations.

  2. Is the timing of scent emission correlated with insect visitor activity and pollination in long-spurred Satyrium species?

    Science.gov (United States)

    van der Niet, T; Jürgens, A; Johnson, S D

    2015-01-01

    Plants are expected to emit floral scent when their pollinators are most active. In the case of long-tubed flowers specialised for pollination by crepuscular or nocturnal moths, scent emissions would be expected to peak during dawn. Although this classic idea has existed for decades, it has rarely been tested quantitatively. We investigated the timing of flower visitation, pollination and floral scent emissions in six long-spurred Satyrium species (Orchidaceae). We observed multiple evening visits by pollinaria-bearing moths on flowers of all study species, but rarely any diurnal visits. The assemblages of moth pollinators differed among Satyrium species, even those that co-flowered, and the lengths of moth tongues and floral nectar spurs were strongly correlated, suggesting that the available moth pollinator fauna is partitioned by floral traits. Pollinarium removal occurred more frequently during the night than during the day in four of the six species. Scent emission, however, was only significantly higher at dusk than midday in two species. Analysis of floral volatiles using gas chromatography coupled with mass spectrometry yielded 168 scent compounds, of which 112 were species-specific. The scent blends emitted by each species occupy discrete clusters in two-dimensional phenotype space, based on multivariate analysis. We conclude that these long-spurred Satyrium species are ecologically specialised for moth pollination, yet the timing of their scent emission is not closely correlated with moth pollination activity. Scent composition was also more variable than expected from a group of closely related plants sharing the same pollinator functional group. These findings reveal a need for greater understanding of mechanisms of scent production and their constraints, as well as the underlying reasons for divergent scent chemistry among closely related plants.

  3. Dynamics in enzymatic protein complexes offer a novel principle for the regulation of melatonin synthesis in the human pineal gland.

    Science.gov (United States)

    Maronde, Erik; Saade, Anastasia; Ackermann, Katrin; Goubran-Botros, Hany; Pagan, Cecile; Bux, Roman; Bourgeron, Thomas; Dehghani, Faramarz; Stehle, Jörg H

    2011-08-01

    Time of day is communicated to the body through rhythmic cues, including pineal gland melatonin synthesis, which is restricted to nighttime. Whereas in most rodents transcriptional regulation of the arylalkylamine N-acetyltransferase (Aanat) gene is essential for rhythmic melatonin synthesis, investigations into nonrodent mammalian species have shown post-transcriptional regulation to be of central importance, with molecular mechanisms still elusive. Therefore, human pineal tissues, taken from routine autopsies were allocated to four time-of-death groups (night/dawn/day/dusk) and analyzed for daytime-dependent changes in phosphorylated AANAT (p31T-AANAT) and in acetyl-serotonin-methyltransferase (ASMT) expression and activity. Protein content, intracellular localization, and colocalization of p31T-AANAT and ASMT were assessed, using immunoblotting, immunofluorescence, and immunoprecipitation techniques. Fresh sheep pineal gland preparations were used for comparative purposes. The amount of p31T-AANAT and ASMT proteins as well as their intracellular localization showed no diurnal variation in autoptic human and fresh sheep pineal glands. Moreover, in human and sheep pineal extracts, AANAT could not be dephosphorylated, which was at variance to data derived from rat pineal extracts. P31T-AANAT and ASMT were often found to colocalize in cellular rod-like structures that were also partly immunoreactive for the pinealocyte process-specific marker S-antigen (arrestin) in both, human and sheep pinealocytes. Protein-protein interaction studies with p31T-AANAT, ASMT, and S-antigen demonstrated a direct association and formation of robust complexes, involving also 14-3-3. This work provides evidence for a regulation principle for AANAT activity in the human pineal gland, which may not be based on a p31T-AANAT phosphorylation/dephosphorylation switch, as described for other mammalian species.

  4. The Cluster Magnetic Field Investigation: overview of in-flight performance and initial results

    Directory of Open Access Journals (Sweden)

    A. Balogh

    Full Text Available The accurate measurement of the magnetic field along the orbits of the four Cluster spacecraft is a primary objective of the mission. The magnetic field is a key constituent of the plasma in and around the magnetosphere, and it plays an active role in all physical processes that define the structure and dynamics of magnetospheric phenomena on all scales. With the four-point measurements on Cluster, it has become possible to study the three-dimensional aspects of space plasma phenomena on scales commeasurable with the size of the spacecraft constellation, and to distinguish temporal and spatial dependences of small-scale processes. We present an overview of the instrumentation used to measure the magnetic field on the four Cluster spacecraft and an overview the performance of the operational modes used in flight. We also report on the results of the preliminary in-orbit calibration of the magnetometers; these results show that all components of the magnetic field are measured with an accuracy approaching 0.1 nT. Further data analysis is expected to bring an even more accurate determination of the calibration parameters. Several examples of the capabilities of the investigation are presented from the commissioning phase of the mission, and from the different regions visited by the spacecraft to date: the tail current sheet, the dusk side magnetopause and magnetosheath, the bow shock and the cusp. We also describe the data processing flow and the implementation of data distribution to other Cluster investigations and to the scientific community in general.

    Key words. Interplanetary physics (instruments and techniques – magnetospheric physics (magnetospheric configuration and dynamics – space plasma physics (shock waves

  5. The un-uniform observatories location effect in the Dst index

    Science.gov (United States)

    Wu, Y.

    2012-12-01

    The Dst index is a major planetary magnetic activity index proposed by Sugiura in 1964, which is designed to depict the temporal development of the magnetic storm and the intensity of the ring current system flowing in the equatorial plane of the magnetosphere at 3 to 8 Earth radii. It is an hourly index derived from the average value of the horizontal component of the geomagnetic field at four low latitudinal observatories (namely, HER, HON, KAK and SJG). For a long time, the Dst index is greatly doubted. Researchers have pointed out that a great proportion of the Dst index is originated from the Substorm Wedge current system, the Cross-tail current and the Partial ring current system [Turner et al., 2000; Liemohn et al., 2001; Ohtani et al., 2001; Rostoker, 2000; Friedrich et al., 1999; Maltsev, 2003; Huang, 2004; Hakkinen et al., 2002]. The ring current system and its disturbed storm-time field (Dst field) take on an enhanced dawn-dusk asymmetry during disturbed time. Therefore, the influence of the non-uniform location of four observatories of the Dst index will enhance. The purpose of this paper is to study the influence of the observatories' location on the Dst index. The hourly data of the horizontal component of the geomagnetic field in the observatories in geomagnetic latitude between 45°S and -45°N is used, to derive the local-time distribution model of the Dst field by the method of Nature Orthogonal Component and Cubic Polynomial Fitting. Results suggest that the maximum difference to the LT-model with four Dst index stations is about 5% lowness on 16UTmp, 3% highness on 05UTmp, and the minimum difference is around 11UTmp (UTmp corresponds to the universal time of the minimum of the Dst index). It proves some certain extent efficiency afforded by adding observatories in the SYM index.

  6. Carbon dioxide measurements in the nocturnal boundary layer over Amazonian forest

    Directory of Open Access Journals (Sweden)

    A. D. Culf

    1999-01-01

    Full Text Available Measurements of carbon dioxide concentration, temperature and windspeed were made in the nocturnal boundary layer over a tropical forest near Manaus, Brazil using a tethered balloon system. The measurements were made up to a maximum height of 300 m on ten consecutive nights in November 1995. Simultaneous surface flux and in-canopy concentration measurements were made at the surface close to the site. The observation period included several different types of conditions. Generally strong windshear and relatively weak temperature gradients prevented the formation of a strong capping inversion to the nocturnal boundary layer. On some nights, however, the inversion was sufficiently strong that the CO2 concentration at 100 m above the surface exceeded 400 ppm. The concentration within the canopy was largely controlled by the presence of an inversion very close to the canopy surface. The temperature and wind profiles are contrasted with conditions in Randônia, Brazil, where the windshear was found to be weaker and higher carbon dioxide concentrations were observed in the early morning. The difference in carbon dioxide concentrations in the nocturnal boundary layer between dusk and dawn is used to estimate the regional nighttime flux of carbon dioxide. The value obtained generally exceeds the measured surface flux and sometimes exceeds the sum of the surface flux and the in-canopy storage made at the tower site. The reasons for the discrepancy are not clear; either one of the methods is in error or the regional carbon dioxide budget differs significantly from the local budget measured at the tower site.

  7. Sex attractant pheromone of the red-shouldered stink bug Thyanta pallidovirens: a pheromone blend with multiple redundant components.

    Science.gov (United States)

    McBrien, H L; Millar, J G; Rice, R E; McElfresh, J S; Cullen, E; Zalom, F G

    2002-09-01

    The male-produced sex pheromone of the red-shouldered stink bug, Thyanta pallidovirens (Stål) (Hemiptera: Pentatomidae) consists of a blend of methyl (E2,Z4,Z6)-decatrienoate (E2,Z4,Z6-10:COOMe), and the sesquiterpenes (+)-alpha-curcumene, (-)-zingiberene, and (-)-beta-sesquiphellandrene. In laboratory bioassays, sexually mature males attracted sexually mature females but not males, and females did not attract either sex. Extracts of volatiles collected from sexually mature males contained compounds not present in extracts from females or sexually immature males, and male-produced extract was attractive to females. Biological activity was lost when the extract was fractionated, indicating that the pheromone consisted of at least two components having different chemical properties. Individually, pheromone components were not attractive to females, but E2,Z4,Z6-10:COOMe in combination with at least one of the three male-produced sesquiterpenes was attractive. The presence of more than one sesquiterpene in the blend did not increase attraction, indicating redundancy in the pheromone signal. Male extract was as attractive as a blend reconstructed from synthesized compounds, indicating all biologically active components had been identified. In bioassays conducted at dusk in a 1- x 1- x 1-m screen field cage, females were attracted to synthetic pheromone lures. In field trials, adult female T pallidovirens were attracted to pheromone-baited traps in relatively low numbers. The profile of volatiles released by sexually mature males of a congeneric species, Thyanta accerra custator McAtee, was remarkably similar to that of male T. pallidovirens, with the exception that the former species produced (E)-2-decenal, a compound that was not found in T. pallidovirens extracts.

  8. Mercury's Na Exosphere from MESSENGER Data

    Science.gov (United States)

    Killen, Rosemary M.; Burger, M. H.; Cassidy, T. A.; Sarantos, M.; Vervack, R. J.; McClintock, W. El; Merkel, A. W.; Sprague, A. L.; Solomon, S. C.

    2012-01-01

    MESSENGER entered orbit about Mercury on March 18, 2011. Since then, the Ultraviolet and Visible Spectrometer (UWS) channel of MESSENGER's Mercury Atmospheric and Surface Composition Spectrometer (MASCS) has been observing Mercury's exosphere nearly continuously. Daily measurements of Na brightness were fitted with non-uniform exospheric models. With Monte Carlo sampling we traced the trajectories of a representative number of test particles, generally one million per run per source process, until photoionization, escape from the gravitational well, or permanent sticking at the surface removed the atom from the simulation. Atoms were assumed to partially thermally accommodate on each encounter with the surface with accommodation coefficient 0.25. Runs for different assumed source processes are run separately, scaled and co-added. Once these model results were saved onto a 3D grid, we ran lines of sight from the MESSENGER spacecraft :0 infinity using the SPICE kernels and we computed brightness integrals. Note that only particles that contribute to the measurement can be constrained with our method. Atoms and molecules produced on the nightside must escape the shadow in order to scatter light if the excitation process is resonant-light scattering, as assumed here. The aggregate distribution of Na atoms fits a 1200 K gas, with a PSD distribution, along with a hotter component. Our models constrain the hot component, assumed to be impact vaporization, to be emitted with a 2500 K Maxwellian. Most orbits show a dawnside enhancement in the hot component broadly spread over the leading hemisphere. However, on some dates there is no dawn/dusk asymmetry. The portion of the hot/cold source appears to be highly variable.

  9. Investigating storm-enhanced density and polar tongue of ionization development during the 22 October 1999 great storm

    Science.gov (United States)

    Horvath, Ildiko; Lovell, Brian C.

    2015-02-01

    We investigate large-scale plasma density increases occurring during the 22 October 1999 great storm and focus on storm-enhanced density (SED) and polar tongue of ionization (TOI) development. Observations include two-hourly Global Ionosphere Map series coupled with multi-instrument in situ, space-based, and ground-based data plots, with Super Dual Auroral Radar Network two-cell convection maps and with model-generated neutral wind vector maps. Results demonstrate the equatorial electrojet events occurring in the Australian and American sectors, the high-density plasma features, and their underlying plasma transportation processes. During the main phase, a series of four prompt penetration electric field (PPEF) events occurred with subauroral polarization stream E field development forming a plasmaspheric drainage plume. These E field events caused the repeated development of equatorial ionization anomaly (EIA), SED bulge, and SED plume during the local dusk-midnight hours in those sectors that covered these local times. Showing a westward movement in accordance with their local time dependence, the EIA-SED structure developed first in the American sector, later on over the Pacific, and finally in the Australian sector. The SED plume plasma found its way into the polar cap through the dayside cusp region, created in the north some large polar cap enhancements reaching up to seven times of the quiet time levels, and evolved in each hemisphere into a polar TOI. We speculate that the enhanced growth of EIA, transporting high-density solar-produced plasma to the SED bulge via strong net eastward E field effects, and the mechanical effects of equatorward neutral winds contributed to the polar TOI's increasingly better development.

  10. The Harang Reversal and the Interchange Stability of the Magnetotail

    Science.gov (United States)

    Ohtani, S.; Gkioulidou, M.; Wang, C. P.; Wolf, R.

    2015-12-01

    During the substorm growth phase the overall convection, electric currents, and aurora structures in the nightside ionosphere often change very gradually over prolonged (> 1 hr) periods, and therefore the magnetosphere-ionosphere (M-I) system can be considered to be in a quasi-steady state. For the source region of a downward field-aligned current (FAC) the cross-tail current, which is carried mostly by ions, closes with a FAC, which is carried by electrons moving away from the ionosphere. Thus both ions and electrons accumulate there and accordingly, the plasma pressure increases. In the source region of an upward FAC, in contrast, the reduction of plasma pressure is expected. Since the plasma pressure, more precisely the entropy parameter (pVr), is most critical for the interchange stability of the magnetotail, this simple assessment raises a fundamental question about the magnetotail dynamics, that is, how the magnetotail remains to be steady. In this study we argue that if the magnetosphere is in a steady state, those expected increase and decrease in plasma pressure need to balance with the change due to the plasma transport by convection. This requirement, along with the condition for the interchange stability, leads to the conclusion that the associated pattern of convection has a structure that is presumably the magnetospheric counter part of the Harang reversal. More specifically, for the dusk convection cell, the convection flow is directed azimuthally westward in the source region of the downward R2 current, whereas it is directed sunward in the source region of the upward R1 current. We verify this idea by examining a quasi-steady magnetotail modeled by the RCM-Dungey code. Using equi-potential contours as a reference we also suggest that auroral arcs mapped to the equator tend to be oriented in the east-west and Sun-Earth direction if they are located in the premidnight R2 and R1 currents, respectively.

  11. Multi-instrument observations and numerical modeling of intense ion upflows during stormtime polar cap expansion

    Science.gov (United States)

    Zou, S.; Ozturk, D. S.; Ridley, A. J.; Jia, X.; Nicolls, M. J.; Coster, A. J.; Thomas, E. G.; Ruohoniemi, J. M.

    2016-12-01

    The Earth's ionosphere plays an important role in supplying plasma into the magnetosphere through ion upflow/outflow, particularly during periods of strong solar wind driving. An intense ion upflow flux event during the June 1, 2013 geomagnetic storm has been studied using observations from multiple instruments, including Poker Flat incoherent scatter radar (PFISR) and GPS total electron content (TEC), as well as numerical simulations. After the IMF southward turning, the open-closed field line boundary (OCB) and convection cells in the high latitude Northern hemisphere, as observed by the Defense Meteorological Satellite Program (DMSP) satellites and the Super Dual Auroral Radar Network (SuperDARN) radars, expanded equatorward rapidly. When the cusp moved into the PFISR field-of-view, divergent ion fluxes were observed by the field-aligned beam of PFISR with intense ion upflow fluxes reaching 1.9 x1014 m-2s-1 at 600 km altitude. Both ion and electron temperatures increased significantly within the ion upflow and thus this upflow event was classified as Type-2 upflow. We discuss possible contributing factors for the formation of such intense ion upflow fluxes, including preconditioning by storm-enhanced density (SED) and temperature dependent chemistry. The global ionosphere thermosphere model (GITM) has been employed to quantitatively study the formation mechanisms of the upflows. During this event, the OCB and cusp were detected by DMSP between 15-16 MLTs, unusually duskward. Results from a global MHD simulation using the Space Weather Modeling Framework (SWMF) have been used to provide a global context for this event. The global simulation suggests that due to the very low solar wind Mach number ( 4), magnetopause reconnection occurred across a wide range of local times extending into the dusk sector where DMSP observed the cusp.

  12. Urban malaria risk in sub-Saharan Africa: where is the evidence?

    Science.gov (United States)