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Sample records for auroral oval

  1. Ancient Norwegian literature in relation to the auroral oval

    International Nuclear Information System (INIS)

    The Poetic Edda and The King's Mirror are well preserved Norse documents from the period between 700 and 1300 A.D. The latter states that the aurora was known to people living in Greenland but probably not observed in Norway at about 1200 A.D. The Poetic Edda does not include any decisive evidence for the aurora being known to the Norse scalds in the Viking era. This is a rather surprising fact as the scalds were much inspired by natural phenomena, and in particular occupied by celestial gestalts. In a search for an explanation of this lack of inspiration from the northern lights among the Norse scalds it is maintained that the position and shape of the auroral oval was different in the Viking era from the present day auroral oval. (orig.)

  2. 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.

  3. Severe and localized GNSS scintillation at the poleward edge of the nightside auroral oval during intense substorm aurora

    CERN Document Server

    van der Meeren, Christer; Lorentzen, Dag A; Rietveld, Michael T; Clausen, Lasse B N

    2016-01-01

    In this paper we study how GPS, GLONASS, and Galileo navigation signals are compromised by strong irregularities causing severe phase scintillation ($\\mathit{\\sigma }_{\\phi }$ > 1) in the nightside high-latitude ionosphere during a substorm on 3 November 2013. Substorm onset and a later intensification coincided with polar cap patches entering the auroral oval to become auroral blobs. Using Global Navigation Satellite Systems (GNSS) receivers and optical data, we show severe scintillation driven by intense auroral emissions in the line of sight between the receiver and the satellites. During substorm expansion, the area of scintillation followed the intense poleward edge of the auroral oval. The intense auroral emissions were colocated with polar cap patches (blobs). The patches did not contain strong irregularities, neither before entering the auroral oval nor after the aurora had faded. Signals from all three GNSS constellations were similarly affected by the irregularities. Furthermore, two receivers space...

  4. Numerical simulation for a vortex street near the poleward boundary of the nighttime auroral oval

    Science.gov (United States)

    Yamamoto, T.

    2012-02-01

    The formation of a vortex street is numerically studied as an aftermath of a transient (≈1 min) depression of the energy density of injected particles. It is basically assumed that the kinetic energies of auroral particles are substantially provided by nonadiabatic acceleration in the tail current sheet. One of the causes of such energy density depression is an outward (away from the Earth) movement of the neutral line because in such situation, a particle passes the acceleration zone for a shorter time interval while it is inwardly transported in the current sheet. The numerical simulation shows that a long chain of many (≥5) vortices can be formed in the nighttime high-latitude auroral oval as a result of the hybrid Kelvin-Helmholtz/Rayleigh-Taylor (KH/RT) instability. The main characteristics of long vortex chains in the simulation such as the short lifetime (≲2 min) and the correlation between wavelength, λ, and arc system width, A, compare well with those of the periodic auroral distortions observed primarily in the high-latitude auroral oval. Specifically, either λ-A relationship from simulation or observation shows a positive correlation between λ and A but with considerable dispersion in λ. Since auroral vortices arising from the hybrid KH/RT instability are not accompanied by significant rotational motions, the magnetic shear instability caused by undulations in the field-aligned current (FAC) sheet could turn the vortices into spirals which wind or unwind in response to increase or decrease of FACs, respectively.

  5. Position of projections of the nightside auroral oval equatorward and poleward edges in the magnetosphere equatorial plane

    Science.gov (United States)

    Kirpichev, I. P.; Yagodkina, O. I.; Vorobjev, V. G.; Antonova, E. E.

    2016-07-01

    The position of the auroral oval poleward and equatorward boundary projections on the equatorial plane in the nightside MLT sector during magnetically quiet periods (| AL| balance of pressures during the nighttime have been taken into account. The morphological mapping method has been used to map the oval poleward and equatorward edges without the use of any magnetic field model on the assumption that the condition of magnetostatic equilibrium is valid. Ion pressures at ionospheric altitudes and in the equatorial plane have been compared. It has been shown that the auroral oval equatorward boundary in the midnight sector is localized at geocentric distances of ~7 R E , which is in good agreement with the position of the energetic particle injection boundary in the equatorial plane. The oval poleward edge is localized at the ~10 R E geocentric distance, which is in good agreement with the position of the equatorward boundary of the region with a high turbulence level in the Earth's magnetosphere plasma sheet.

  6. Dependence of substorm occurrence probability on the interplanetary magnetic field and on the size of the auroral oval

    International Nuclear Information System (INIS)

    The dependence of substorm occurrence probability on the north--south component Bz of the interplanetary magnetic field (IMF) and on the size of the auroral oval is examined on the basis of two independent data sets (Isis 1 and 2 low-energy electron data and all-sky camera data from the Alaska meridan). The occurrence of substorms is identified by the electron precipitation pattern (Isis data), the auroral features in the Alaskan sector, and available ground magnetic records. The substorm occurrence frequency increases as the oval expands and as the Bz component of the IMF decreases. It increases from approximately 25% to 100% for Bz values of the IMF ranging from +7 to -5 nT; here Bz values are averaged for 1 hour preceding the time of satellite passage and the onset of substorms observed by the all-sky cameras. The occurrence probability of quiet times increases with an increasing value of the northward IMF. It is interesting to note that there are almost no periods without substorms when the IMF has a large southward component, but substorms do occur even when the IMF has a large northward component. Since there is a close relationship between the direction of the IMF and the size of the auroral oval, our finding that the occurrence frequency of substorms increases with the expansion of the auroral oval suggests that the substorm probability may be related to the amount of energy stored in the magnetotail

  7. The spatial structure and temporal variability of Ganymede’s auroral ovals from Hubble Space Telescope observations

    Science.gov (United States)

    Musacchio, Fabrizio; Saur, Joachim; Roth, Lorenz; Retherford, Kurt D.; McGrath, Melissa A.; Feldman, Paul D.; Strobel, Darrel F.

    2015-11-01

    We analyze spectrally and spatially resolved images of Ganymede’s FUV-auroral ovals obtained during the past two decades by Hubble’s Space Telescope Imaging Spectrograph (HST/STIS). We find both, spatial inhomogeneities of the brightness-distribution on the observed disk as well as temporal variation as a function of Ganymede’s position relative to the Jovian current sheet. The brightness of the ovals is not equally distributed along the ovals, i.e., the Jupiter-facing side is always brighter than the anti-Jupiter side at least by ~60%. When Ganymede moves from high elevated magnetic latitudes towards the center region of the Jovian current sheet, the brightness of the aurora on the leading side increases by over 30% from ~80 Rayleigh up to ~108 Rayleigh. Simultaneously, inside the current sheet center the auroral ovals are displaced by an average of ~6° of planetographic latitude, i.e., the ovals shift furthermore down towards the planetographic equator on the leading side, and up towards the poles on the trailing side. Both effects, the increase of brightness and the moving of the ovals, are correlated to increased plasma interaction inside the current sheet. Ganymede’s electron-impact-excited auroral emissions are thought to be driven by electron acceleration by strong field-aligned currents at the boundary area between open and closed magnetic field lines of Ganymede’s mini-magnetosphere. The change of the auroral morphology is a direct response to the changing plasma environment, i.e., changing ram and thermal pressures. Thus, the investigation of the aurora proves to be a suitable diagnostic tool of the various processes that contribute to Ganymede’s complex plasma and magnetic field environment.

  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. A real-time hybrid aurora alert system: Combining citizen science reports with an auroral oval model

    Science.gov (United States)

    Case, N. A.; Kingman, D.; MacDonald, E. A.

    2016-06-01

    Accurately predicting when, and from where, an aurora will be visible is particularly difficult, yet it is a service much desired by the general public. Several aurora alert services exist that attempt to provide such predictions but are, generally, based upon fairly coarse estimates of auroral activity (e.g., Kp or Dst). Additionally, these services are not able to account for a potential observer's local conditions (such as cloud cover or level of darkness). Aurorasaurus, however, combines data from the well-used, solar wind-driven, OVATION Prime auroral oval model with real-time observational data provided by a global network of citizen scientists. This system is designed to provide more accurate and localized alerts for auroral visibility than currently available. Early results are promising and show that over 100,000 auroral visibility alerts have been issued, including nearly 200 highly localized alerts, to over 2000 users located right across the globe.

  10. Dynamics of polar boundary of the auroral oval derived from the IMAGE satellite data

    Science.gov (United States)

    Lukianova, R.; Kozlovsky, A.

    2013-01-01

    Based on a new database on positions of the auroral oval boundaries including measurements made by the IMAGE satellite in 2000-2002 with correct determination of the glow boundaries, statistical estimations of the latitudinal position of the polar cap boundary (PCB) are obtained depending on the IMF B y and B z , and the PCB evolution during a magnetic storm is analyzed. At zero IMF in the noon (midnight) sector, PCB is located approximately at 80° (76°) CGMLat. The PCB displacement along the noon-midnight meridian is controlled by the IMF B z , and in the noon (midnight) sector it is equal to 0.45° (0.15°) CGMLat when B z changes by 1 nT. The PCB displacement along the dawn-dusk meridian depends on the IMF B y , and it equals 0.1° CGMLat when B y changes by 1 nT. Accordingly, the north polar cap as a whole is shifted to the dawn (dusk) side at B y > 0 ( B y night boundary requires 25 h or more in order to be shifted to the pole to a latitude corresponding to B z > 0.

  11. The search for a subsurface ocean in Ganymede with Hubble Space Telescope observations of its auroral ovals

    Science.gov (United States)

    Saur, Joachim; Duling, Stefan; Roth, Lorenz; Jia, Xianzhe; Strobel, Darrell F.; Feldman, Paul D.; Christensen, Ulrich R.; Retherford, Kurt D.; McGrath, Melissa A.; Musacchio, Fabrizio; Wennmacher, Alexandre; Neubauer, Fritz M.; Simon, Sven; Hartkorn, Oliver

    2015-03-01

    We present a new approach to search for a subsurface ocean within Ganymede through observations and modeling of the dynamics of its auroral ovals. The locations of the auroral ovals oscillate due to Jupiter's time-varying magnetospheric field seen in the rest frame of Ganymede. If an electrically conductive ocean is present, the external time-varying magnetic field is reduced due to induction within the ocean and the oscillation amplitude of the ovals decreases. Hubble Space Telescope (HST) observations show that the locations of the ovals oscillate on average by 2.0° ±1.3°. Our model calculations predict a significantly stronger oscillation by 5.8° ± 1.3° without ocean compared to 2.2°±1.3° if an ocean is present. Because the ocean and the no-ocean hypotheses cannot be separated by simple visual inspection of individual HST images, we apply a statistical analysis including a Monte Carlo test to also address the uncertainty caused by the patchiness of observed emissions. The observations require a minimum electrical conductivity of 0.09 S/m for an ocean assumed to be located between 150 km and 250 km depth or alternatively a maximum depth of the top of the ocean at 330 km. Our analysis implies that Ganymede's dynamo possesses an outstandingly low quadrupole-to-dipole moment ratio. The new technique applied here is suited to probe the interior of other planetary bodies by monitoring their auroral response to time-varying magnetic fields.

  12. Magnetopause erosion during the 17 March 2015 magnetic storm: Combined field-aligned currents, auroral oval, and magnetopause observations

    Science.gov (United States)

    Le, G.; Lühr, H.; Anderson, B. J.; Strangeway, R. J.; Russell, C. T.; Singer, H.; Slavin, J. A.; Zhang, Y.; Huang, T.; Bromund, K.; Chi, P. J.; Lu, G.; Fischer, D.; Kepko, E. L.; Leinweber, H. K.; Magnes, W.; Nakamura, R.; Plaschke, F.; Park, J.; Rauberg, J.; Stolle, C.; Torbert, R. B.

    2016-03-01

    We present multimission observations of field-aligned currents, auroral oval, and magnetopause crossings during the 17 March 2015 magnetic storm. Dayside reconnection is expected to transport magnetic flux, strengthen field-aligned currents, lead to polar cap expansion and magnetopause erosion. Our multimission observations assemble evidence for all these manifestations. After a prolonged period of strongly southward interplanetary magnetic field, Swarm and AMPERE observe significant intensification of field-aligned currents. The dayside auroral oval, as seen by DMSP, appears as a thin arc associated with ongoing dayside reconnection. Both the field-aligned currents and the auroral arc move equatorward reaching as low as ~60° magnetic latitude. Strong magnetopause erosion is evident in the in situ measurements of the magnetopause crossings by GOES 13/15 and MMS. The coordinated Swarm, AMPERE, DMSP, MMS and GOES observations, with both global and in situ coverage of the key regions, provide a clear demonstration of the effects of dayside reconnection on the entire magnetosphere.

  13. Combined ESR and EISCAT observations of the dayside polar cap and auroral oval during the May 15, 1997 storm

    Directory of Open Access Journals (Sweden)

    H. Liu

    Full Text Available The high-latitude ionospheric response to a major magnetic storm on May 15, 1997 is studied and different responses in the polar cap and the auroral oval are highlighted. Depletion of the F2 region electron density occurred in both the polar cap and the auroral zone, but due to different physical processes. The increased recombination rate of O+ ions caused by a strong electric field played a crucial role in the auroral zone. The transport effect, however, especially the strong upward ion flow was also of great importance in the dayside polar cap. During the main phase and the beginning of the recovery phase soft particle precipitation in the polar cap showed a clear relation to the dynamic pressure of the solar wind, with a maximum cross-correlation coefficient of 0.63 at a time lag of 5 min.

    Key words: Ionosphere (auroral ionosphere; polar ionosphere - Magnetospheric physics (storms and substorms

  14. Cassini nightside observations of the oscillatory motion of Saturn's northern auroral oval

    OpenAIRE

    Bunce, E. J.; Grodent, D. C.; Jinks, S.L.; Andrews, D. J.; Badman, S. V.; Coates, A. J.; Cowley, S. W. H.; Dougherty, M. K.; W. S. Kurth; Mitchell, D.G.; G. Provan

    2014-01-01

    In recent years we have benefitted greatly from the first in-orbit multi-wavelength images of Saturn's polar atmosphere from the Cassini spacecraft. Specifically, images obtained from the Cassini UltraViolet Imaging Spectrograph (UVIS) provide an excellent view of the planet's auroral emissions, which in turn give an account of the large-scale magnetosphere-ionosphere coupling and dynamics within the system. However, obtaining near-simultaneous views of the auroral regions with in situ measur...

  15. Ground-based and satellite observations of high-latitude auroral activity in the dusk sector of the auroral oval

    Directory of Open Access Journals (Sweden)

    K. Kauristie

    Full Text Available On 7 December 2000, during 13:30–15:30 UT the MIRACLE all-sky camera at Ny Ålesund observed auroras at high-latitudes (MLAT ~ 76 simultaneously when the Cluster spacecraft were skimming the magnetopause in the same MLT sector (at ~ 16:00–18:00 MLT. The location of the auroras (near the ionospheric convection reversal boundary and the clear correlation between their dynamics and IMF variations suggests their close relationship with R1 currents. Consequently, we can assume that the Cluster spacecraft were making observations in the magnetospheric region associated with the auroras, although exact magnetic conjugacy between the ground-based and satellite observations did not exist. The solar wind variations appeared to control both the behaviour of the auroras and the magnetopause dynamics. Auroral structures were observed at Ny Ålesund especially during periods of negative IMF BZ. In addition, the Cluster spacecraft experienced periodic (T ~ 4 - 6 min encounters between magnetospheric and magnetosheath plasmas. These undulations of the boundary can be interpreted as a consequence of tailward propagating magnetopause surface waves. Simultaneous dusk sector ground-based observations show weak, but discernible magnetic pulsations (Pc 5 and occasionally periodic variations (T ~ 2 - 3 min in the high-latitude auroras. In the dusk sector, Pc 5 activity was stronger and had characteristics that were consistent with a field line resonance type of activity. When IMF BZ stayed positive for a longer period, the auroras were dimmer and the spacecraft stayed at the outer edge of the magnetopause where they observed electromagnetic pulsations with T ~ 1 min. We find these observations interesting especially from the viewpoint of previously presented studies relating poleward-moving high-latitude auroras with pulsation activity and MHD waves propagating at the magnetospheric boundary layers

  16. E and F region study of the evening sector auroral oval: A Chatanika/Dynamics Explorer 2/NOAA 6 comparison

    International Nuclear Information System (INIS)

    Simultaneous data obtained with the Chatanika incoherent scatter radar and the Dynamics Explorer 2 (DE 2) and NOAA 6 satellites are used to relate the locations of the precipitating particles, field-aligned currents, and E and F region ionization structures in the evening-sector auroral oval. The auroral E layer observed by the radar extends about 2 degree equatorward of the electron precipitation region, and its equatorward edge coincides with the equatorward edges of the region 2 field-aligned current and intense convection region (E ≅ 50 mV/m). It is shown that precipitating protons are responsible for part of the E region ionization within the electron precipitation region as well as south of it. E region density profiles calculated from ion spectra measured by the DE 2 and NOAA 5 satellites are in fairly good agreement with the Chatanika data. in the F region, a channel of enhanced ionization density, elongated along the east-west direction and having a width of about 100 km, marks the poleward edge of the main trough. it is colocated with the equatorward boundary of the electron precipitation from the central plasma sheet. Although enhanced fluxes of soft electrons are observed at this boundary, the energy input to the ionospheric electron gas, calculated from the radar data, shows that this ionization channel is not locally produced by this soft precipitation, but that it is rather a convected feature. In fact, both the trough and the ionization channel are located in a region where the plasma flows sunward at high speed, but the flux tubes associated with theses two features have different convective time histories. Keeping in mind that several processes operate together in the F region, the data set is consistent with the included trough and ionization channel formation mechanisms

  17. Evidence for parallel electric field particle acceleration in the dayside auroral oval

    International Nuclear Information System (INIS)

    Electron and ion energy spectra and electron pitch angle distributions are presented for two sounding rocket flights in the dayside auroral zone. At times, effect of dc electric fields parallel to the magnetic field are evident in that (1) within precipitation features, protons are decelerated by an amount of energy consistent with that which electrons gain and (2) electrons are sometimes aligned to within 3 0 (full width at half maximum) of the magnetic field. A maximum altitude for the accelerating region of several thousand kilometers is deduced from the narrow width of the pitch angle distribution and also from time-of-flight delays between the observation of accelerated electrons and decelerated protons

  18. B(sub y)-controlled field-aligned currents near midnight auroral oval during northward interplanetary magnetic field

    International Nuclear Information System (INIS)

    Using the magnetic field data from southern passes of Magsat for which the interplanetary magnetic field (IMF) Bz component was positive and the By component was particularly stable, the author presents a new By-controlled field-aligned current system which develops in the midnight sector. This current system is composed of three sheets of the field-aligned current approximately parallel to the auroral oval. This is referred to as the midnight sector triple-sheet (MTS) field-aligned current system. The MTS current system appears in the premidnight sector (postmidnight sector) of the southern hemisphere when By is negative (positive). When By is negative (positive), the current system consists of the most equatorward and the most poleward sheets with currents flowing away from (into) the ionosphere and a sheet in between with currents flowing into (away from) the ionosphere. The MTS current system develops at higher latitudes than the usual region 1 and region 2 field-aligned current system. When IMF Bz takes negative values or values close to zero, the region 1 and region 2 current system develops, and the MTS current system itself disappears. The MTS current system is defined in 70 passes among 100 passes from which IMF Bz was positive and By was stable. In most of the remaining 30 passes, one can see the region 1 and region 2 field-aligned current system that is similar to what is observed for southward IMF. Statistical results from the 70 cases indicate that the main controlling factors of the intensity of the MTS current system are magnitude of By and the magnetic local time

  19. Statistical study of the 'instantaneous' nightside auroral oval: The equatorward boundary of electron precipitation as observed by the Isis 1 and 2 satellites

    International Nuclear Information System (INIS)

    Electron spectrograms from 351 passes of the Isis 1 and 2 satellites were utilized to study statistically the effects of the interplanetary magnetic field (IMF), substorm activity, and the earth's dipole tilt angle on the latitude of the equatorward boundary of the nightside (2000--0400 magnetic local time) 'instantaneous' auroral oval. The boundary location (in invariant latitude) of the instantaneous oval at hourly local time intervals was identified in terms of the equatorward boundary of the diffuse >100-eV electron precipitation. The following characteristics were noted: (1) The north-south component (B/sub z/) of the IMF plays the dominant role in controlling the motion of this boundary. The invariant latitude of the boundary is shown to shift by approximately +- 40 depending on the direction of the IMF (northward and southward, respectively) relative to its position corresponding to B/sub z/=0. This indicates an inward motion of the associated boundary in the magnetotail by about 5 earth radii when the IMF changes its direction from northward to southward with large magnitude. There is a significant difference in the amount of the shift between the evening and morning sectors: i.e., for the same decrease in B/sub z/ value the boundary moves more equatorward in the morning sector than in the evening sector. When the obtained oval particle boundary was projected onto the equatorial plane of the magnetotail along magnetic field lines, good agreement was found between the projected boundary and the drift boundary (the Alfven layer) of low-energy electrons in the presence of the dawn-dusk electric field. (2) Substorm activity seems to have a separate role in determining the latitude of the equatorward boundary of the nightside auroral precipitation region

  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. 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

  2. Dependence of the open-closed field line boundary in Saturn's ionosphere on both the IMF and solar wind dynamic pressure: comparison with the UV auroral oval observed by the HST

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2008-02-01

    Full Text Available We model the open magnetic field region in Saturn's southern polar ionosphere during two compression regions observed by the Cassini spacecraft upstream of Saturn in January 2004, and compare these with the auroral ovals observed simultaneously in ultraviolet images obtained by the Hubble Space Telescope. The modelling employs the paraboloid model of Saturn's magnetospheric magnetic field, whose parameters are varied according to the observed values of both the solar wind dynamic pressure and the interplanetary magnetic field (IMF vector. It is shown that the open field area responds strongly to the IMF vector for both expanded and compressed magnetic models, corresponding to low and high dynamic pressure, respectively. It is also shown that the computed open field region agrees with the poleward boundary of the auroras as well as or better than those derived previously from a model in which only the variation of the IMF vector was taken into account. The results again support the hypothesis that the auroral oval at Saturn is associated with the open-closed field line boundary and hence with the solar wind interaction.

  3. IMF dependence of the open-closed field line boundary in Saturn's ionosphere, and its relation to the UV auroral oval observed by the Hubble Space Telescope

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2007-06-01

    Full Text Available We study the dependence of Saturn's magnetospheric magnetic field structure on the interplanetary magnetic field (IMF, together with the corresponding variations of the open-closed field line boundary in the ionosphere. Specifically we investigate the interval from 8 to 30 January 2004, when UV images of Saturn's southern aurora were obtained by the Hubble Space Telescope (HST, and simultaneous interplanetary measurements were provided by the Cassini spacecraft located near the ecliptic ~0.2 AU upstream of Saturn and ~0.5 AU off the planet-Sun line towards dawn. Using the paraboloid model of Saturn's magnetosphere, we calculate the magnetospheric magnetic field structure for several values of the IMF vector representative of interplanetary compression regions. Variations in the magnetic structure lead to different shapes and areas of the open field line region in the ionosphere. Comparison with the HST auroral images shows that the area of the computed open flux region is generally comparable to that enclosed by the auroral oval, and sometimes agrees in detail with its poleward boundary, though more typically being displaced by a few degrees in the tailward direction.

  4. Magnetospheric mapping of the dayside UV auroral oval at Saturn using simultaneous HST images, Cassini IMF data, and a global magnetic field model

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2011-07-01

    Full Text Available We determine the field-aligned mapping of Saturn's auroras into the magnetosphere by combining UV images of the southern dayside oval obtained by the Hubble Space Telescope (HST with a global model of the magnetospheric magnetic field. The model is tailored to simulate prevailing conditions in the interplanetary medium, corresponding to high solar wind dynamic pressure and variable interplanetary magnetic field (IMF strength and direction determined from suitably lagged field data observed just upstream of Saturn's dayside bow shock by the Cassini spacecraft. Two out of four images obtained in February 2008 when such simultaneous data are available are examined in detail, exemplifying conditions for northward and southward IMF. The model field structure in the outer magnetosphere and tail is found to be very different in these cases. Nevertheless, the dayside UV oval is found to have a consistent location relative to the field structure in each case. The poleward boundary of the oval is located close to the open-closed field boundary and thus maps to the vicinity of the magnetopause, consistent with previous results. The equatorward boundary of the oval then maps typically near the outer boundary of the equatorial ring current appropriate to the compressed conditions prevailing. Similar results are also found for related images from the January 2004 HST data set. These new results thus show that the mapped dayside UV oval typically spans the outer magnetosphere between the outer part of the ring current and the magnetopause. It does not encompass the region of primary corotation flow breakdown within the inner Enceladus torus.

  5. Dayside cosmic noise absorption at the equatorward boundary of auroral oval as observed from Maitri, Antarctica (L = 5; CGM 62.45°S, 55.45°E)

    Science.gov (United States)

    Behera, Jayanta K.; Sinha, Ashwini K.; Vichare, Geeta; Kozyreva, Olga; Rawat, Rahul; Dhar, Ajay

    2016-04-01

    On 02 April 2011, a couple of cosmic noise absorption (CNA) events were detected at Maitri, Antarctica (L = 5; CGM 63.14°S, 53.69°E) confining to nighttime and daytime. One of the two events that occurred during night hours was caused due to auroral substorm onset. The current study focuses on the later CNA event, which was recorded during daytime (10:00-13:00 magnetic local time (MLT), MLT = UT-1, at Maitri, Antarctica). We refer to this CNA event as dayside CNA (DCNA) event. Absence of westward electrojet during DCNA confirms its dissimilarity from auroral substorm absorption events. A comparison has been made between the DCNA event of 02 April 2011 with that of 14 July 2011, a day with substorm activity when Maitri is in dayside but without DCNA event. The comparison has been made in the light of interplanetary conditions, imaging riometer data, ground magnetic signatures, GOES electron flux density, and associated pulsations. The study shows that stronger prolonged eastward interplanetary electric field favors the occurrence of DCNA event. It is concluded that DCNA event is due to the gradient curvature drift of trapped nonrelativistic electrons in the equatorial plane. Estimated energy of trapped electrons using azimuthal drift time for a set of ground stations within the auroral oval confirms the enhancement in electron fluxes in the same energy band as recorded by geostationary satellites GOES 13 and GOES 15. The reason for precipitation of electrons is expected to be the loss cone scattering caused by wave-particle interaction triggered by ULF waves.

  6. 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

  7. Dayside Auroral Activity During Solar Maximum and Minimum Periods

    Science.gov (United States)

    Rawie, M.; Fasel, G. J.; Flicker, J.; Angelo, A.; Bender, S.; Alyami, M.; Sibeck, D. G.; Sigernes, F.; Lorentzen, D. A.; Green, D.

    2014-12-01

    It is well documented that the dayside auroral oval shifts equatorward when the interplanetary magnetic field (IMF) Bz-component turns southward [Burch, 1973; Akasofu, 1977; Horwitz and Akasofu, 1977; Sandholt et al., 1986, 1988]. During these periods of oval expansion dayside transients are observed to move away from the poleward edge of the auroral oval and drift poleward. These poleward-moving auroral forms are believed to be ionospheric signatures of dayside merging. The dayside auroral oval usually begins to contract when the interplanetary magnetic field turns sharply northward, Bz>0. Eighteen years of meridian scanning photometer (MSP) data from the Kjell Henriksen Observatory in Longyearbyen, Norway are analyzed. During the boreal winter the Sun is several degrees below the horizon. This permits optical observations throughout the daytime period. The MSP Data is selected two hours before and after local noon in Longyearbeyn. Solar wind data (solar wind pressure and speed, along with the IMF Bx, By, Bz components) are collected for each interval and combined with the MSP observations. This data is then separated using solar maximum and minimum periods. Auroral activity (oval expansions and contractions along with the frequency and number of poleward-moving auroral forms) is documented for both solar maximum and minimum periods.

  8. Patent foramen ovale

    Science.gov (United States)

    ... Drugs & Supplements Videos & Tools About MedlinePlus Show Search Search MedlinePlus GO GO About MedlinePlus Site Map FAQs Contact Us Health Topics Drugs & Supplements Videos & Tools Español You Are Here: Home → Medical Encyclopedia → Patent foramen ovale URL of this page: //medlineplus.gov/ ...

  9. Height-integrated conductivity in auroral substorms. 1. Data

    DEFF Research Database (Denmark)

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    2000-01-01

    are highly localized with a typical scale size of similar to 20 km and are associated with energetic (>10 keV) inverted V events. Except in the low-latitude part of the auroral oval the Hall to Pedersen ratio equals or exceeds 1.0, and it peaks in the high-latitude part of the surge where values of 3...

  10. Patent foramen ovale.

    Science.gov (United States)

    Homma, Shunichi; Messé, Steven R; Rundek, Tatjana; Sun, Yee-Ping; Franke, Jennifer; Davidson, Karina; Sievert, Horst; Sacco, Ralph L; Di Tullio, Marco R

    2016-01-01

    Patent foramen ovale (PFO) is the most common congenital heart abnormality of fetal origin and is present in approximately ∼25% of the worldwide adult population. PFO is the consequence of failed closure of the foramen ovale, a normal structure that exists in the fetus to direct blood flow directly from the right to the left atrium, bypassing the pulmonary circulation. PFO has historically been associated with an increased risk of stroke, the mechanism of which has been attributed to the paradoxical embolism of venous thrombi that shunt through the PFO directly to the left atrium. However, several studies have failed to show an increased risk of stroke in asymptomatic patients with a PFO, and the risk of stroke recurrence is low in patients who have had a stroke that may be attributed to a PFO. With the advent of transoesophageal and transthoracic echocardiography, as well as transcranial Doppler, a PFO can be routinely detected in clinical practice. Medical treatment with either antiplatelet or anticoagulation therapy is recommended. At the current time, closure of the PFO by percutaneous interventional techniques does not appear to reduce the risk of stroke compared to conventional medical treatment, as shown by three large clinical trials. Considerable controversy remains regarding the optimal treatment strategy for patients with both cryptogenic stroke and PFO. This Primer discusses the epidemiology, mechanisms, pathophysiology, diagnosis, screening, management and effects on quality of life of PFO. PMID:27188965

  11. Monitoring auroral electrojets with satellite data

    DEFF Research Database (Denmark)

    Vennerstrøm, Susanne; Moretto, T.

    2013-01-01

    The strong horizontal ionospheric currents in the auroral oval constitute an important space weather parameter. Here we present a method to estimate the latitude location and intensity of these currents from measurements of variations in the magnetic field magnitude made by low Earth polar orbiting...... satellites. The method is simple enough to be implemented for real-time monitoring, especially since it does not require the full vector field measurement. We demonstrate the method on 5 years of Challenging Minisatellite Payload (CHAMP) data and show how the monitoring depends on the local time of the...... and complement existing ground-based indices. The CHAMP magnetometer in 350–450km altitude easily measures an electrojet which on the ground would produce an Auroral Electrojet (AE)-type signal as small as 20 nT. Thus, while the signal decreases roughly proportionally to the square of the distance to...

  12. Harmonic motion and Cassini ovals

    OpenAIRE

    Khristo N. Boyadzhiev; Boyadzhiev, Irina A.

    2013-01-01

    We consider a two-dimensional free harmonic oscillator where the initial position is fixed and the initial velocity can change direction. All possible orbits are ellipses and their enveloping curve is an ellipse too. We show that the locus of the foci of all elliptical orbits is a Cassini oval. Depending on the magnitude of the initial velocity we observe all three kinds of Cassini ovals, one of which is the lemniscate of Bernoulli. These Cassini ovals have the same foci as the enveloping ell...

  13. Forecast of auroral activity

    International Nuclear Information System (INIS)

    A new technique is developed to predict auroral activity based on a sample of over 9000 auroral sites identified in global auroral images obtained by an ultraviolet imager on the NASA Polar satellite during a 6-month period. Four attributes of auroral activity sites are utilized in forecasting, namely, the area, the power, and the rates of change in area and power. This new technique is quite accurate, as indicated by the high true skill scores for forecasting three different levels of auroral dissipation during the activity lifetime. The corresponding advanced warning time ranges from 22 to 79 min from low to high dissipation levels

  14. Patent foramen ovale: Unanswered questions

    OpenAIRE

    Mojadidi, MK; Christia, P; Salamon, J; Liebelt, J; T Zaman; Gevorgyan, R; Nezami, N; Mojaddedi, S; Elgendy, IY; Tobis, JM; Faillace, R

    2015-01-01

    The foramen ovale is a remnant of the fetal circulation that remains patent in 20-25% of the adult population. Although long overlooked as a potential pathway that could produce pathologic conditions, the presence of a patent foramen ovale (PFO) has been associated with a higher than expected frequency in a variety of clinical syndromes including cryptogenic stroke, migraines, sleep apnea, platypnea-orthodeoxia, deep sea diving associated decompression illness, and high altitude pulmonary ede...

  15. Sophus Peter Tromholt: an outstanding pioneer in auroral research

    Directory of Open Access Journals (Sweden)

    K. Moss

    2012-03-01

    Full Text Available The Danish school teacher Sophus Peter Tromholt (1851–1896 was self-taught in physics, astronomy, and auroral sciences. Still, he was one of the brightest auroral researchers of the 19th century. He was the first scientist ever to organize and analyse correlated auroral observations over a wide area (entire Scandinavia moving away from incomplete localized observations. Tromholt documented the relation between auroras and sunspots and demonstrated the daily, seasonal and solar cycle-related variations in high-latitude auroral occurrence frequencies. Thus, Tromholt was the first ever to deduce from auroral observations the variations associated with what is now known as the auroral oval termed so by Khorosheva (1962 and Feldstein (1963 more than 80 yr later. He made reliable and accurate estimates of the heights of auroras several decades before this important issue was finally settled through Størmer's brilliant photographic technique. In addition to his three major scientific works (Tromholt, 1880a, 1882a, and 1885a, he wrote numerous short science notes and made huge efforts to collect historical auroral observations (Tromholt, 1898. Furthermore, Tromholt wrote a large number of popular science articles in newspapers and journals and made lecture tours all over Scandinavia and Germany, contributing to enhance the public educational level and awareness. He devoted most of his life to auroral research but as a self-taught scientist, he received little acclaim within the contemporary academic scientific society. With his non-academic background, trained at a college of education – not a university – he was never offered a position at a university or a research institution. However, Sophus Tromholt was an outstanding pioneer in auroral research.

  16. Sophus Peter Tromholt: an outstanding pioneer in auroral research

    Science.gov (United States)

    Moss, K.; Stauning, P.

    2012-03-01

    The Danish school teacher Sophus Peter Tromholt (1851-1896) was self-taught in physics, astronomy, and auroral sciences. Still, he was one of the brightest auroral researchers of the 19th century. He was the first scientist ever to organize and analyse correlated auroral observations over a wide area (entire Scandinavia) moving away from incomplete localized observations. Tromholt documented the relation between auroras and sunspots and demonstrated the daily, seasonal and solar cycle-related variations in high-latitude auroral occurrence frequencies. Thus, Tromholt was the first ever to deduce from auroral observations the variations associated with what is now known as the auroral oval termed so by Khorosheva (1962) and Feldstein (1963) more than 80 yr later. He made reliable and accurate estimates of the heights of auroras several decades before this important issue was finally settled through Størmer's brilliant photographic technique. In addition to his three major scientific works (Tromholt, 1880a, 1882a, and 1885a), he wrote numerous short science notes and made huge efforts to collect historical auroral observations (Tromholt, 1898). Furthermore, Tromholt wrote a large number of popular science articles in newspapers and journals and made lecture tours all over Scandinavia and Germany, contributing to enhance the public educational level and awareness. He devoted most of his life to auroral research but as a self-taught scientist, he received little acclaim within the contemporary academic scientific society. With his non-academic background, trained at a college of education - not a university - he was never offered a position at a university or a research institution. However, Sophus Tromholt was an outstanding pioneer in auroral research.

  17. Comparison of auroral structures at Earth and Jupiter

    Science.gov (United States)

    Hill, T.

    Bright, well-defined auroral structures generally mark the presence of strong upward Birkeland (magnetic-field-aligned) currents which couple the magnetosphere to the planetary ionosphere. These Birkeland currents tend to flow in sheets aligned with strong velocity shear layers in the magnetospheric plasma flow as mapped to the ionosphere. At Earth, velocity shear layers are produced in the magnetosphere's response to solar-wind forcing, and occur near the topological separator surface between open and closed magnetic field lines. At Jupiter, strong velocity shear is produced by internal magnetospheric processes far removed from the open-closed boundary. These processes include the enforcement of partial corotation of magnetospheric plasma, responsible for the "main oval" aurora, and the electrodynamic coupling of Jupiter to its Galilean moons, responsible for auroral spots at the magnetic footprints of Io, Europa, and Ganymede, and an auroral tail downstream of Io. Both planets also exhibit "polar-cap" auroral structures that share at least two features in common: they are more time-variable than the oval emissions, and their origins are not understood.

  18. Another Proof of Segre's Theorem about Ovals

    OpenAIRE

    Müller, Peter

    2013-01-01

    In 1955 B. Segre showed that any oval in a projective plane over a finite field of odd order is a conic. His proof constructs a conic which matches the oval in some points, and then shows that it actually coincides with the oval. Here we give another proof. We describe the oval by a possibly high degree polynomial, and then show that the degree is actually 2.

  19. Urban Crafts and Oval Brooches

    DEFF Research Database (Denmark)

    Sindbæk, Søren Michael

    2011-01-01

    This paper discusses technological and stylistic variations in copper-alloy workshops in Viking Age towns. In the decades around year 800 a cluster of new technologies, art styles and object types, including the characteristic oval brooches, were adopted across Scandinavia. Shared details of...... professional identity among craftspeople. This could indicate that the first urban craftspeople in Scandinavia were communities with a sense of civic identity, rather than itinerant cosmopolitans....

  20. Remote auroral activity detection and modeling using low frequency transmitter signal reception at a midlatitude site

    Directory of Open Access Journals (Sweden)

    E. D. Schmitter

    2010-09-01

    Full Text Available The low frequency propagation conditions along the path from Iceland to Germany (52° N 8° E using the NRK/TFK 37.5 kHz transmitter (63.9° N 22.5° W prove as an easy to monitor and reliable proxy for north auroral activity. Signal processing using wavelet decomposition allows for quantitative activity level estimations. Calibration is based upon NOAA POES auroral activity data. Using an auroral oval model for the local intensity distribution of solar energetic particle precipitation and a wave propagation model ionospheric D-layer height decreases along the path can be derived. This in turn gives a hint to the low latitude extension and intensity of the auroral electrojet currents that can be responsible for communication and power systems failures.

  1. 2-D Three Fluid Simulation of Upstreaming Ions Above Auroral Precipitation

    Science.gov (United States)

    Danielides, M. A.; Lummerzheim, D.; Otto, A.; Stevens, R. J.

    2006-12-01

    The ionosphere is a rich reservoir of charged particles from which a variable fraction is transported to the magnetosphere. An important transport phenomena is the formation of upward ion flow above auroral structure. A primary region of the outflow is not known, but contributions come from polar cap, dayside cusp/cleft region, auroral oval, or even from mid-latitudes. In the past global magnetospheric models and fluid codes were used to simulate large scale ion outflow above, e.g., the polar-cap aurora. However, satellites orbiting at low- altitudes have repeatingly detected localized ion outflow above the auroral oval. Ionosphere-magnetosphere coupling simulations gave first insides into the small-scale dynamics of aurora. The aim of this study is the investigation of coupled plasma and neutral dynamics in smaller scale aurora to explain the generation, structure, and dynamics of vertical ion upstream. We consider auroral electron precipitation at ionospheric heights in a 2-D three fluid ionospheric-magnetospheric coupling code (Otto and Zhu, 2003). Specially we examine the effects of the electron precipitation, heat conduction and heating in field- aligned current through coulomb collisions or turbulence causing: i) electron heating, ii) electron pressure gradients, and iii) upstreaming of ions through a resulting ambipolar electric field. Our first case studies are performed for different boundary conditions and for different auroral electron precipitation parameters (variation in characteristic auroral energy, auroral energy flux and horizontal scale). The results shall clarify how auroral precipitation can drive ions upwards. Finally we discuss the effect of ion drag and the interaction of the upstreaming ions with a stable neutral constituent. Otto, O. and H. Zhu, Fluid plasma simulation of coupled systems: Ionosphere and magnetosphere, Space Plasma Simulation. Edited by J. Buechner, C. Dum, and M. Scholer., Lecture Notes in Physics, vol. 615, p.193

  2. Saturn's auroral morphology and field-aligned currents during a solar wind compression

    Science.gov (United States)

    Badman, S. V.; Provan, G.; Bunce, E. J.; Mitchell, D. G.; Melin, H.; Cowley, S. W. H.; Radioti, A.; Kurth, W. S.; Pryor, W. R.; Nichols, J. D.; Jinks, S. L.; Stallard, T. S.; Brown, R. H.; Baines, K. H.; Dougherty, M. K.

    2016-01-01

    On 21-22 April 2013, during a coordinated auroral observing campaign, instruments onboard Cassini and the Hubble Space Telescope observed Saturn's aurora while Cassini traversed Saturn's high latitude auroral field lines. Signatures of upward and downward field-aligned currents were detected in the nightside magnetosphere in the magnetic field and plasma measurements. The location of the upward current corresponded to the bright ultraviolet auroral arc seen in the auroral images, and the downward current region was located poleward of the upward current in an aurorally dark region. Within the polar cap magnetic field and plasma fluctuations were identified with periods of ∼20 and ∼60 min. The northern and southern auroral ovals were observed to rock in latitude in phase with the respective northern and southern planetary period oscillations. A solar wind compression impacted Saturn's magnetosphere at the start of 22 April 2013, identified by an intensification and extension to lower frequencies of the Saturn kilometric radiation, with the following sequence of effects: (1) intensification of the auroral field-aligned currents; (2) appearance of a localised, intense bulge in the dawnside (04-06 LT) aurora while the midnight sector aurora remained fainter and narrow; and (3) latitudinal broadening and poleward contraction of the nightside aurora, where the poleward motion in this sector is opposite to that expected from a model of the auroral oval's usual oscillation. These observations are interpreted as the response to tail reconnection events, initially involving Vasyliunas-type reconnection of closed mass-loaded magnetotail field lines, and then proceeding onto open lobe field lines, causing the contraction of the polar cap region on the night side.

  3. Patent foramen ovale: clinical manifestations and treatment.

    OpenAIRE

    Kedia, G; Tobis, J; Lee, MS

    2008-01-01

    A persistent patent foramen ovale produces an intermittent intra-atrial right-to-left shunt and occurs in approximately 25% of the general population. Although the vast majority of people with patent foramen ovale are asymptomatic, a patent foramen ovale is believed to act as a pathway for chemicals or thrombus that can result in a variety of clinical manifestations, including stroke, migraine headache, decompression sickness, high-altitude pulmonary edema, and platypnea-orthodeoxia syndrome....

  4. Statistical study of the GNSS phase scintillation associated with two types of auroral blobs

    Science.gov (United States)

    Jin, Yaqi; Moen, Jøran I.; Miloch, Wojciech J.; Clausen, Lasse B. N.; Oksavik, Kjellmar

    2016-05-01

    This study surveys space weather effects on GNSS (Global Navigation Satellite System) signals in the nighttime auroral and polar cap ionosphere using scintillation receivers, all-sky imagers, and the European Incoherent Scatter Svalbard radar. We differentiate between two types of auroral blobs: blob type 1 (BT 1) which is formed when islands of high-density F region plasma (polar cap patches) enter the nightside auroral oval, and blob type 2 (BT 2) which are generated locally in the auroral oval by intense particle precipitation. For BT 1 blobs we have studied 41.4 h of data between November 2010 and February 2014. We find that BT 1 blobs have significantly higher scintillation levels than their corresponding polar cap patch; however, there is no clear relationship between the scintillation levels of the preexisting polar cap patch and the resulting BT 1 blob. For BT 2 blobs we find that they are associated with much weaker scintillations than BT 1 blobs, based on 20 h of data. Compared to patches and BT 2 blobs, the significantly higher scintillation level for BT 1 blobs implies that auroral dynamics plays an important role in structuring of BT 1 blobs.

  5. Patent foramen ovale: Unanswered questions.

    Science.gov (United States)

    Mojadidi, Mohammad Khalid; Christia, Panagiota; Salamon, Jason; Liebelt, Jared; Zaman, Tarique; Gevorgyan, Rubine; Nezami, Nariman; Mojaddedi, Sanaullah; Elgendy, Islam Y; Tobis, Jonathan M; Faillace, Robert

    2015-12-01

    The foramen ovale is a remnant of the fetal circulation that remains patent in 20-25% of the adult population. Although long overlooked as a potential pathway that could produce pathologic conditions, the presence of a patent foramen ovale (PFO) has been associated with a higher than expected frequency in a variety of clinical syndromes including cryptogenic stroke, migraines, sleep apnea, platypnea-orthodeoxia, deep sea diving associated decompression illness, and high altitude pulmonary edema. A unifying hypothesis is that a chemical or particulate matter from the venous circulation crosses the PFO conduit between the right and left atria to produce a variety of clinical syndromes. Although observational studies suggest a therapeutic benefit of PFO closure compared to medical therapy alone in patients with cryptogenic stroke, 3 randomized controlled trials (RCTs) did not confirm the superiority of PFO closure for the secondary prevention of stroke. However, meta-analyses of these RCTs demonstrate a significant benefit of PFO closure over medical therapy alone. Similarly, observational studies provide support for PFO closure for symptomatic relief of migraines. But one controversial randomized study failed to replicate the results of the observational studies while another two demonstrated a partial benefit. The goal of this review is to discuss the clinical conditions associated with PFO and provide internists and primary care physicians with current data on PFO trials, and clinical insight to help guide their patients who are found to have a PFO on echocardiographic testing. PMID:26489724

  6. Auroral electrojets during severely disturbed geomagnetic condition on 24 August 2005

    Science.gov (United States)

    Singh, Anand K.; Sinha, A. K.; Saini, S.; Rawat, Rahul

    2015-03-01

    Very intense and highly dynamic eastward and westward currents flowing in the auroral ionosphere are traditionally monitored by the auroral electrojet indices - AUand AL , respectively. In this study we show that on occasions of intense magnetic activity, entire auroral oval could be dominated by the westward flowing currents, which lead to depression not only in AL index but also in supposedly positive AU index. During negative AU intervals, there could be up to ∼ 20 % underestimation of the total maximum intensity of the auroral electrojet represented by AEindex (defined as AU - AL). A detailed investigation of a well-studied extremely intense event of 24 August 2005 has been carried out. Global prevalence of the westward auroral electrojet was clearly observed at the auroral latitudes during the unusually intense substorm (AL ∼ - 4000 nT) on the day. Moreover, along the noon meridian westward electrojet appeared in the auroral region whereas eastward electrojet shifted towards lower latitudes. This paper emphasizes that intense substorms are represented better by AL index than AE index.

  7. Spectral distribution of auroral energy according to model representation

    International Nuclear Information System (INIS)

    Examples of high-altitude distributions of the auroral energy radiation in the central oval line for τG = 0 and 12 hours within the spectrum interval 0.02-0.1 μm, 0.1-0.2 μm, 0.2-0.3 μm, 0.3-0.4 μm, 0.3-0.7 μmn, 0.3-1.3 μm for various Kp-values under moderate solar activity F10.7 = 150 at the time of the winter solstice are presented. 30 refs., 3 figs., 2 tabs

  8. Temporal and spatial evolution of discrete auroral arcs as seen by Cluster

    OpenAIRE

    Figueiredo, S.; G. T. Marklund; Karlsson, T.; Johansson, T.; Ebihara, Y.; Ejiri, M.; Ivchenko, N.; Lindqvist, P.-A.; Nilsson, H.; A. Fazakerley

    2005-01-01

    Two event studies are presented in this paper where intense convergent electric fields, with mapped intensities up to 1350 mV/m, are measured in the auroral upward current region by the Cluster spacecraft, at altitudes between 3 and 5 Earth radii. Both events are from May 2003, Southern Hemisphere, with equatorward crossings by the Cluster spacecraft of the pre-midnight auroral oval.

    Event 1 occurs during the end of the recove...

  9. Patent foramen ovale: clinical manifestations and treatment.

    Science.gov (United States)

    Kedia, Gautam; Tobis, Jonathan; Lee, Michael S

    2008-01-01

    A persistent patent foramen ovale produces an intermittent intra-atrial right-to-left shunt and occurs in approximately 25% of the general population. Although the vast majority of people with patent foramen ovale are asymptomatic, a patent foramen ovale is believed to act as a pathway for chemicals or thrombus that can result in a variety of clinical manifestations, including stroke, migraine headache, decompression sickness, high-altitude pulmonary edema, and platypnea-orthodeoxia syndrome. The optimal management of patients with patent foramen ovale who experience cryptogenic stroke is unclear. Percutaneous closure appears to have a low risk profile and has been considered in high-risk patients who are not candidates for randomized clinical trials. Randomized clinical trials that are underway should help define the best management of patent foramen ovale, as well as the true safety and efficacy of percutaneous closure devices. PMID:18953276

  10. Auroral Tomography Workshop, Proceedings

    International Nuclear Information System (INIS)

    In ionospheric and atmospheric physics the importance of multi-station imaging has grown as a consequence of the availability of scientific grade CCD cameras with digital output and affordable massive computing power. Tomographic inversion techniques are used in many different areas, e.g. medicine, plasma research and space physics. The tomography workshop was announced to gather a limited group of people interested in auroral tomography or tomographic inversion methods in general. ALIS (Auroral Large Imaging System) is a multi-station ground-based system developed primarily for three-dimensional auroral imaging, however other non-auroral objects can be studied with ALIS, e.g. stratospheric clouds. Several of the contributions in the workshop dealt with problems related to geometries similar to the ALIS-configuration. The Proceedings contain written contributions received either in abstract form or as full papers. The Proceedings also contain contributions intended for the Workshop but not presented due to the absence of the speaker. Separate abstracts have been prepared for 15 of the 17 papers

  11. Investigating the location and strength of the auroral electrojets using Swarm

    OpenAIRE

    Smith, Ashley; Whaler, Kathy; Beggan, Ciaran; MacMillan, Susan

    2016-01-01

    The auroral electrojets are a key space weather phenomenon. They are formed by horizontal Hall currents that flow within the ionospheric polar regions at an altitude of around 115 km. They form ovals around the magnetic poles but their latitudinal position, width, and strength are highly variable. These are governed by geomagnetic activity and solar wind conditions, along with a global ordering by the main magnetic field. Typically, greater geomagnetic activity will cause the electrojets to i...

  12. Variations of auroral hydrogen emission near substorm onset

    Directory of Open Access Journals (Sweden)

    L. P. Borovkov

    2005-07-01

    Full Text Available The results of coordinated optical ground-based observations of the auroral substorm on 26 March 2004 in the Kola Peninsula are described. Imaging spectrograph data with high spectral and temporal resolution recorded the Doppler profile of the Hα hydrogen emission; this allows us to estimate the average energy of precipitating protons and the emission intensity of the hydrogen Balmer line. Two different populations of precipitating protons were observed during an auroral substorm. The first of these is associated with a diffuse hydrogen emission that is usually observed in the evening sector of the auroral oval and located equatorward of the discrete electron arcs associated with substorm onset. The average energy of the protons during this precipitation was ~20–35 keV, and the energy flux was ~3x10–4Joule/m2s. The second proton population was observed 1–2min after the breakup during 4–5min of the expansion phase of substorm into the zone of bright, discrete auroral structures (N-S arcs. The average energy of the protons in this population was ~60 keV, and the energy flux was ~2.2x10–3Joule/m2s. The observed spatial structure of hydrogen emission is additional evidence of the higher energy of precipitated protons in the second population, relative to the protons in the diffuse aurora. We believe that the most probable mechanism of precipitation of the second population protons was pitch-angle scattering of particles due to non-adiabatic motion in the region of local dipolarization near the equatorial plane.

    Keywords. Auroral ionosphere; Particle precipitation; Storms and substorms

  13. Patent Foramen Ovale and Stroke.

    Science.gov (United States)

    Sun, Yee-Ping; Homma, Shunichi

    2016-07-25

    A patent foramen ovale (PFO) is common and found in nearly 25% of healthy individuals. The majority of patients with PFO remain asymptomatic and they are not at increased risk for developing a stroke. The presence of PFO, however, has been found to be higher in patients with cryptogenic stroke, suggesting there may be a subset of patients with PFO who are indeed at risk for stroke. Paradoxical embolization of venous thrombi through the PFO, which then enter the arterial circulation, is hypothesized to account for this relationship. Although aerated-saline transesophageal echocardiography is the gold standard for diagnosis, aerated-saline transthoracic echocardiography and transcranial Doppler are often used as the initial diagnostic tests for detecting PFO. Patients with cryptogenic stroke and PFO are generally treated with antiplatelet therapy in the absence of another condition for which anticoagulation is necessary. Based on the findings of 3 large randomized clinical trials, current consensus guidelines do not recommend percutaneous closure, though this is an area of controversy. The following review discusses the relationship of PFO and cryptogenic stroke, focusing on the epidemiology, pathophysiological mechanisms, diagnostic tools, associated clinical/anatomic factors and treatment. (Circ J 2016; 80: 1665-1673). PMID:27334127

  14. Using citizen science reports to define the equatorial extent of auroral visibility

    Science.gov (United States)

    Case, N. A.; MacDonald, E. A.; Viereck, R.

    2016-03-01

    An aurora may often be viewed hundreds of kilometers equatorward of the auroral oval owing to its altitude. As such, the NOAA Space Weather Prediction Center (SWPC) Aurora Forecast product provides a "view line" to demonstrate the equatorial extent of auroral visibility, assuming that it is sufficiently bright and high in altitude. The view line in the SWPC product is based upon the latitude of the brightest aurora, for each hemisphere, as specified by the real-time oval variation, assessment, tracking, intensity, and online nowcasting (OVATION) Prime (2010) aurora precipitation model. In this study, we utilize nearly 500 citizen science auroral reports to compare with the view line provided by an updated SWPC aurora forecast product using auroral precipitation data from OVATION Prime (2013). The citizen science observations were recorded during March and April 2015 using the Aurorasaurus platform and cover one large geomagnetic storm and several smaller events. We find that this updated SWPC view line is conservative in its estimate and that the aurora is often viewable further equatorward than is indicated by the forecast. By using the citizen reports to modify the scaling parameters used to link the OVATION Prime (2013) model to the view line, we produce a new view line estimate that more accurately represents the equatorial extent of visible aurora. An OVATION Prime (2013) energy flux-based equatorial boundary view line is also developed and is found to provide the best overall agreement with the citizen science reports, with an accuracy of 91%.

  15. Far ultraviolet auroral imager

    Institute of Scientific and Technical Information of China (English)

    FU LiPing; WANG YongMei; WANG YingJian; ZHANG ZhongMou; LU JianGong

    2009-01-01

    Reviewing the technology development of imaging the global FUV auroral morphology,we introduce a space-based FUV auroral imager prototype developed by the Center for Space Science and Applied Research(CSSAR).It is designed to obtain continuous observations on the temporal and spatial morphology of the aurora which occupies highly elliptical high-altitude near-polar orbits.Primarily composed of a telescope system,image intensifier system,CCD,and collection and control system,the instrument works in the spectral region from 140-190 nm in the field of view 25°×25°,and the spatial resolution is better than 0.1°.

  16. Thrombus in Transit through Patent Foramen Ovale

    OpenAIRE

    Hassan Baydoun; Iskander Barakat; Elie Hatem; Michel Chalhoub; Ali Mroueh

    2013-01-01

    A thrombus in transit through a patent foramen ovale (PFO) with impending paradoxical embolism is an extremely rare event. Due to its transient nature, it is unable to identify the thrombus, and most of the cases have been reported at autopsy. We are reporting a case of thrombus straddling the foramen ovale which was diagnosed by echocardiography and treated surgically. Through this personal case, an exhaustive review of the literature was performed. There were 88 cases reported. We concluded...

  17. MORPHOMETRIC AND MORPHOLOGICAL STUDY ON FORAMEN OVALE

    Directory of Open Access Journals (Sweden)

    Magi Murugan

    2014-11-01

    Full Text Available Back Ground: Foramen ovalee is an important foramen of the middle cranial fossa. Foramen ovalee is situated in the greater wing of the sphenoid bone, posterior to the foramen rotundum and lateral to the lingula and posterior end of the carotid groove. Through the foramen ovale the mandibular nerve, accessory meningeal artery and lesser petrossal nerve are passing through it. The shape of foramen ovale is ovale in shape as compare to other foramina of the skull, its shape and size is quite variable. Meterials and Methods: A total 250 skulls were used for this study. The skulls were collected with I MBBS student from different medical colleges in south India. Skulls in poor conditions or skulls with partly damaged surroundings of the foramen ovalee were not considered. Maximum length and width of foramen ovalee was measured. Variation in right and left side and sex difference in length and width were calculated, the variations in shape also recorded. Results: The mean value of length of left foramen ovale is 8.5+1.32mm and right was 8.9+1.67mm. In female it was 8.7+1.67mm and male was 8.4+1.71mm. The mean value of width of left foramen ovale is 3.7+1.03mm and right was 3.9+0.98mm. In female it was 3.8+0.92mm and male was 3.7+1.02mm.The shape of foramen ovale was ovale in 69% of skulls, almond in 29% of skulls and round was 2% of skulls. Conclusion: The present study conclude that there is significant difference between sizes of right and left side foramen ovale and found that between male and female foramen ovale sizes also not shown any significance difference. Foramen ovale has practical significance to both neurosurgical and functional cranial neuroanatomy as it provides transcutaneous approaches to the skull base especially in cases of trigeminal neuralgia, as the Gasserion ganglion can be approached through it.

  18. Ground-based and satellite observations of high-latitude auroral activity in the dusk sector of the auroral oval

    OpenAIRE

    Kauristie, K.; T. I. Pulkkinen; Amm, O.; Viljanen, A.; Syrjäsuo, M.; Janhunen, P.; Massetti, S.; Orsini, S.; Candidi, M.; Watermann, J.; Donovan, E.; P. Prikryl; Mann, I. R.; P. Eglitis; Smith, C.

    2001-01-01

    On 7 December 2000, during 13:30–15:30 UT the MIRACLE all-sky camera at Ny Ålesund observed auroras at high-latitudes (MLAT ~ 76) simultaneously when the Cluster spacecraft were skimming the magnetopause in the same MLT sector (at ~ 16:00–18:00 MLT). The location of the auroras (near the ionospheric convection reversal boundary) and the clear correlation between their dynamics and IMF variations suggests their close relationship with R1 currents. Consequently, we can assume that the Cl...

  19. Altitude Variations of the Peak Auroral Emissions within Auroral Structures

    Science.gov (United States)

    Sangalli, L.

    2015-12-01

    The MIRACLE network monitors auroral activity in the Fennoscandian sector of Europe. Network stations cover the range of 55° to 57° magnetic latitude North and span two hours in magnetic local time. Some of the MIRACLE network stations include digital all-sky cameras (ASC) with overlapping field-of-views located at the latitude aurora occurs. The ASCs in this network operate at three different wavelengths: 427.8 nm (blue line), 557.7 nm (green line) and 630.0 nm (red line). These wavelengths are selected using narrow band filters. The new ASC systems are based on electron multiplying CCDs (emCCD), which allow higher time and spatial resolutions. The peak auroral emission altitude is determined using two ASC images from a station pair. Different auroral events are used to evaluate the altitude variations of the peak auroral emissions within auroral structures and its evolution in time.

  20. Genetic marker suitable for identification and genotyping of Plasmodium ovale curtisi and Plasmodium ovale wallikeri.

    OpenAIRE

    Tanomsing, N.; Imwong, M.; Sutherland, CJ; Dolecek, C; Hien, TT; Nosten, F; Day, NP; White, NJ; Snounou, G.

    2013-01-01

    We present a seminested PCR method that specifically discriminates between Plasmodium ovale curtisi and P. ovale wallikeri with high sensitivity. The test is based on species-specific amplification of a size-polymorphic fragment of the tryptophan-rich antigen gene, potra, which also permits discrimination of intraspecific sequence variants at this locus.

  1. The auroral electron accelerator

    International Nuclear Information System (INIS)

    A model of the auroral electron acceleration process is presented in which the electrons are accelerated resonantly by lower-hybrid waves. The essentially stochastic acceleration process is approximated for the purposes of computation by a deterministic model involving an empirically derived energy transfer function. The empirical function, which is consistent with all that is known of electron energization by lower-hybrid waves, allows many, possibly all, observed features of the electron distribution to be reproduced. It is suggested that the process occurs widely in both space and laboratory plasmas. (author)

  2. Auroral electron acceleration

    International Nuclear Information System (INIS)

    Two theories of auroral electron acceleration are discussed. Part 1 examines the currently widely held view that the acceleration is an ordered process in a quasi-static electric field. It is suggested that, although there are many factors seeming to support this theory, the major qualifications and uncertainties that have been identified combine to cast serious doubt over its validity. Part 2 is devoted to a relatively new interpretation in terms of stochastic acceleration in turbulent electric fields. This second theory, which appears to account readily for most known features of the electron distribution function, is considered to provide a more promising approach to this central question in magnetospheric plasma physics. (author)

  3. An observation of ionospheric convection and auroral arc motion

    International Nuclear Information System (INIS)

    An all-sky imager operated at Sondre Stromfjord, Greenland has been used to make auroral measurements in correlation with data from the incoherent scatter radar. Reviewing the images as movie sequences with an apparent time compression ratio of 60 allows the eye to discern features which are not apparent in the individual frames. The faint 630 nm airglow background lying poleward of the bright auroral oval arcs appears to be structured in the time lapse observations and drifting at a uniform rate. Analysis of the motion of the airglow structures shows excellent agreement with Doppler radar measurement of the ion drift velocities. Electron density profiles derived from the radar data corroborate the existence of high altitude F-region ionization enhancements. The electron temperature in the patches was about 1,000 K and no higher than outside of the patch signifying that the patches were not produced by local soft electron precipitation. According to the radar Doppler data there was a small component of the drift velocity parallel to the arc at either side of the auroral boundary. The sense of those small components was consistent with drifts driven by a convergent electric field which would also produce an up going field aligned current. The larger component of drift velocity perpendicular to the arc appeared to be continuous on either side of the arc. This drift component shows the existence of an electric field parallel to the arc, showing that the arc was not on an equipotential. During the observations the arc moved slowly in the opposite sense to the ion drift, signifying that the auroral arc motion is not driven by the electric field impressed on the atmosphere by the magnetosphere. Calculations of the expected intensity of the 630 nm emissions are in good agreement with the measured intensities of the moving patches

  4. Auroral Spatial Structures Probe Project

    Data.gov (United States)

    National Aeronautics and Space Administration —    Methodology Fly a high altitude sounding rocket with multiple sub-payloads to measure electric and magnetic fields during an auroral event. Use...

  5. Response of northern winter polar cap to auroral substorms

    Science.gov (United States)

    Liou, Kan; Sotirelis, Thomas

    2016-05-01

    The three-phase substorm sequence has been generally accepted and is often tied to the Dungey cycle. Although previous studies have mostly agreed on the increase and decrease in the polar cap area during an episode of substorm, there are disparate views on when the polar cap starts to contract relative to substorm onset. Here we address this conflict using high-resolution (~1-3 min) snapshot global auroral images from the ultraviolet imager on board the Polar spacecraft. On the basis of 28 auroral substorm events, all observed in the Northern Hemispheric winter, it is found that the polar cap inflated prior to onset in all events and it attained the largest area ~6 min prior to the substorm expansion phase onset, while the dayside polar cap area remained steady around the onset. The onset of nightside polar cap deflation is found to be attributed to intensifications of aurora on the poleward edge of the nightside oval, mostly in the midnight sector. Although this result supports the loading-unloading and reconnection substorm models, it is not clear if the initial polar cap deflation and the substorm expansion are parts of the same process.

  6. Velocity of small-scale auroral ionospheric current systems over Indian Antarctic station Maitri

    Indian Academy of Sciences (India)

    Girija Rajaram; A N Hanchinal; R Kalra; K Unnikrishnan; K Jeeva; M Sridharan; A Dhar

    2002-03-01

    The Indian Antarctic station Maitri (geog. 70° 45/S, 11° 45/E, geom. 66° .03S, 53°.21E) occupies a sub-auroral location during magnetically quiet conditions ( Kp < 10), but attains an auroral position when the auroral oval shifts equatorwards with increasing strength of magnetic disturbance. At the latter times, triangulation with 3 uxgate magnetometers located at the vertices of a suitable triangle provides a means of monitoring mobile auroral ionospheric current systems over Maitri. The spacing between the magnetometers is typically kept at 75-200 km, keeping in mind the scale-sizes of ∼100 km for these mobile current systems. This work reports the results of two triangulation experiments carried out around Maitri in January 1992 and January 1995, both during Antarctic summer. The velocities estimated for pulsations of the Pc4 and Pc5 type were about 0.59 km/sec in the direction 102°.7 east of due north, in the first case, and about 1-3 km/sec in the second case in the east-west direction. While several magnetometer arrays exist in the northern auroral regions (e.g., the Alberta array in Canada, the Alaskan array in the U.S. and the IMS Scandinavian array), there is no report in literature of triangulation through arrays in Antarctica, except for a one-day study by Neudegg et al 1995 for ULF pulsations of the Pc1 and Pc2 type. The velocities obtained for the Pi3 type of irregular pulsations over Antarctica in the present study tally well with those obtained for northern auroral locations.

  7. Spatial monitoring of auroral emissions

    International Nuclear Information System (INIS)

    A ground based technique to monitor the three-dimensional distribution of auroral emissions is presented. The system is composed of two subsystems. A monochromatic imaging system with digitizing capability monitors the two-dimensional variation of auroral intensity with 50 degree field of view. A second height measuring system obtains in real time the height distribution of the auroral luminosity within the field of view of the imaging system. This paper is a report of the stepwise development of the complete system. The measurements will be carried out in the magnetic meridian plane through the EISCAT-site in Norway and the Kiruna Geophysical Institute. The operation of the optical system will as much as possible be combined with incoherent scatter radar measurements. (author)

  8. Interhemispheric asymmetries in the occurrence of magnetically conjugate sub-auroral polarisation streams

    Science.gov (United States)

    Parkinson, M. L.; Pinnock, M.; Wild, J. A.; Lester, M.; Yeoman, T. K.; Milan, S. E.; Ye, H.; Devlin, J. C.; Frey, H. U.; Kikuchi, T.

    2005-06-01

    Earthward injections of energetic ions and electrons mark the onset of magnetospheric substorms. In the inner magnetosphere (L{sim}4), the energetic ions drift westward and the electrons eastward, thereby enhancing the equatorial ring current. Wave-particle interactions can accelerate these particles to radiation belt energies. The ions are injected slightly closer to Earth in the pre-midnight sector, leading to the formation of a radial polarisation field in the inner magnetosphere. This maps to a poleward electric field just equatorward of the auroral oval in the ionosphere. The poleward electric field is subsequently amplified by ionospheric feedback, thereby producing auroral westward flow channels (AWFCs). In terms of electric field strength, AWFCs are the strongest manifestation of substorms in the ionosphere. Because geomagnetic flux tubes are essentially equi-potentials, similar AWFC signatures should be observed simultaneously in the Northern and Southern Hemispheres. Here we present magnetically conjugate SuperDARN radar observations of AWFC activity observed in the pre-midnight sector during two substorm intervals including multiple onsets during the evening of 30 November 2002. The Northern Hemisphere observations were made with the Japanese radar located at King Salmon, Alaska (57circLambda ), and the Southern Hemisphere observations with the Tasman International Geospace Environment Radar (TIGER) located at Bruny Island, Tasmania (-55circLambda ). LANL geosynchronous satellite observations of energetic ion and electron fluxes monitored the effects of substorms in the inner magnetosphere (L{sim}6). The radar-observed AWFC activity was coincident with activity observed at geosynchronous orbit, as well as westward current surges in the ionosphere observed using ground-based magnetometers. The location of AWFCs with respect to the auroral oval was inferred from FUV auroral images recorded on board the IMAGE spacecraft. DMSP SSIES ion drift measurements

  9. Patent Foramen Ovale: Stroke and Device Closure.

    Science.gov (United States)

    Suradi, Hussam S; Hijazi, Ziyad M

    2016-05-01

    Patent foramen ovale (PFO) is a common finding in healthy adults and has long been implicated in cryptogenic stroke. The pathogenesis is hypothesized to be caused by microemboli gaining access into the systemic circulation via a PFO. Proposed treatment options include medical therapy and/or PFO closure. Despite numerous studies and several randomized trials, much debate persists regarding the efficacy of this approach in reducing the risk of recurrent stroke in cryptogenic stroke patients. This article reviews the association between PFO and cryptogenic stroke, as well as current evidence for PFO device closure. PMID:27150171

  10. Patent foramen ovale: a new disease?

    Science.gov (United States)

    Drighil, Abdenasser; El Mosalami, Hanane; Elbadaoui, Nadia; Chraibi, Said; Bennis, Ahmed

    2007-10-31

    Patent foramen ovale is a frequent remnant of the fetal circulation. Affecting approximately 25% of the adult population. Its recognition, evaluation and treatment has attracted increasing interest as the importance and frequency of its implication in several pathologic processes, including ischemic stroke secondary to paradoxic embolism, the platypnea-orthodeoxia syndrome, decompression sickness (DCS) (an occupational hazard for underwater divers and high altitude aviators and astronauts) and migraine headache, has become better understood. Echocardiographic techniques have emerged as the principle means for diagnosis and assessment of PFO, in particular contrast echocardiography and transcranial Doppler. Its treatment remains controversial with a general tendency to propose a percutaneous closure among the symptomatic patients. PMID:17395315

  11. Ortodeoxia recorrente e foramen ovale patente.

    OpenAIRE

    Magalhães, L.; Pinto, R; Oliveira, J. de; Oliveira, F; E. Reis

    2011-01-01

    Introdução: Foramen ovale patente (FOP) ocorre em até 25% dos adultos saudáveis. Pode favorecer embolização paradoxal, enxaqueca e insuficiência respiratória (IR). Apresenta-se caso de IR e ortodeoxia por shunt direito-esquerdo via FOP sem evidência prévia de aumento da pressão intra-auricular direita. Encerramento do FOP resolveu eficazmente IR. Caso clínico: Homem, 52 anos. Mieloma múltiplo IgA/k diagnosticado um ano antes. Internado por IR hipoxémica grave ...

  12. Aurores boréales

    OpenAIRE

    Génot, Vincent

    1998-01-01

    Aurores boréales photographiées près d'Abisko (Suède, 68°21'N,18°49'E) en décembre 1998 par Vincent Génot (chercheur au CESR - Centre d'Etudes Spatiales des Rayonnements -, Toulouse, France) & Stéphanie Michiels.

  13. On the occurrence and motion of decametre-scale irregularities in the sub-auroral, auroral, and polar cap ionosphere

    Directory of Open Access Journals (Sweden)

    M. L. Parkinson

    reminiscent of "dusk scatter" (Ruohoniemi et al., 1988. There was a dusk "bite out" of large spectral widths between ~ 15 and 21 MLT and poleward of - 67 °L, and a pre-dawn enhancement of large spectral widths between ~  03 and 07 MLT, centred on ~ - 61 °L. The average LOS Doppler velocities revealed that frequent westward jets of plasma flow occurred equatorward of, but overlapping, the diffuse auroral oval in the pre-midnight sector.

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

  14. Ionospheric control of auroral occurrence

    International Nuclear Information System (INIS)

    Complete text of publication follows. Analogous to color CRTs, the aurora is a visual manifestation of the bombardment of atomic and molecular neutrals in the upper atmosphere by magnetic field-guided energetic charged particles (mainly electrons) from above. Based on this framework, the magnetosphere is the source of energetic particles, whereas the ionosphere is merely a passive 'illuminated target'. However, it is not clear if the magnetosphere is acting along in the energization of the particles because the energization occurs at the magnetosphere-ionosphere interface. The discovery of suppression of auroral acceleration events in sunlight [Newell et al., 1996] provides a new interpretation - the ionosphere is also playing an active role in the auroral production. The auroral sunlight effect is often attributed to an ionospheric feedback mechanism in which the background ionospheric conductance determines if an acceleration is required. However, a relationship between the background ionospheric conductance and the aurora has not been identified. In this presentation, we provide solid evidence to confirm that the ionospheric conductance plays a key role in modulating auroral intensity to a degree that may surpass its source's manipulation. This study is based on 56,675 Earth's disk FUV images of the polar regions acquired by TIMED/GUVI between February 2002 and November 2007. It is found that the occurrence rate of visible aurora reduces when the polar ionosphere is exposed to sunlight. Furthermore, the energy flux carried by precipitating electrons shows anti-correlation with the ionospheric background conductance. Suppression of the auroral energy flux is also found to continue in twilight until the ionosphere is totally in darkness - a strong evidence of ionospheric manipulation because the magnetospheric sunlight condition does not change. The present study suggests a new mechanism that governs our space disturbances, in addition to the more familiar

  15. Thrombus in Transit through Patent Foramen Ovale.

    Science.gov (United States)

    Baydoun, Hassan; Barakat, Iskander; Hatem, Elie; Chalhoub, Michel; Mroueh, Ali

    2013-01-01

    A thrombus in transit through a patent foramen ovale (PFO) with impending paradoxical embolism is an extremely rare event. Due to its transient nature, it is unable to identify the thrombus, and most of the cases have been reported at autopsy. We are reporting a case of thrombus straddling the foramen ovale which was diagnosed by echocardiography and treated surgically. Through this personal case, an exhaustive review of the literature was performed. There were 88 cases reported. We concluded that there is no medical consensus about the best option for treatment. Nevertheless, surgery, which is associated with fewer complications of recurrent embolic events than those of thrombolysis and anticoagulation, appeared to be the best approach in patients who are not at a high surgical risk. Anticoagulant treatment appears to be an acceptable therapeutic alternative to surgery, particularly in patients with comorbidities who are at high surgical risk and for patients with small PFO. Thrombolysis is linked to the highest mortality, which could be explained by the severity of the patient's initial presentation. In conclusion, and after the cumulative effects of these case reports, we propose a diagram consisting of the use of the three therapeutic options in the different clinical scenarios. PMID:24826281

  16. Thrombus in Transit through Patent Foramen Ovale

    Directory of Open Access Journals (Sweden)

    Hassan Baydoun

    2013-01-01

    Full Text Available A thrombus in transit through a patent foramen ovale (PFO with impending paradoxical embolism is an extremely rare event. Due to its transient nature, it is unable to identify the thrombus, and most of the cases have been reported at autopsy. We are reporting a case of thrombus straddling the foramen ovale which was diagnosed by echocardiography and treated surgically. Through this personal case, an exhaustive review of the literature was performed. There were 88 cases reported. We concluded that there is no medical consensus about the best option for treatment. Nevertheless, surgery, which is associated with fewer complications of recurrent embolic events than those of thrombolysis and anticoagulation, appeared to be the best approach in patients who are not at a high surgical risk. Anticoagulant treatment appears to be an acceptable therapeutic alternative to surgery, particularly in patients with comorbidities who are at high surgical risk and for patients with small PFO. Thrombolysis is linked to the highest mortality, which could be explained by the severity of the patient’s initial presentation. In conclusion, and after the cumulative effects of these case reports, we propose a diagram consisting of the use of the three therapeutic options in the different clinical scenarios.

  17. Auroral Electrojet Index Designed to Provide a Global Measure, Hourly Intervals, of Auroral Zone Magnetic Activity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Auroral Electrojet (AE) index is designed to provide a global quantitative measure of auroral zone magnetic activity produced by enhanced ionospheric currents...

  18. Jupiter's auroral-related thermal infrared emission from IRTF-TEXES

    Science.gov (United States)

    Sinclair, James; Orton, Glenn; Greathouse, Thomas; Fletcher, Leigh; Irwin, Patrick

    2015-11-01

    Auroral processes on Jupiter can be observed at a large range of wavelengths. Charged particles of the solar wind are deflected by Jupiter’s magnetic field and penetrate the atmosphere at high latitudes. This results in ion and/or electron precipitation, which produces emission at X-ray, UV, visible, near-infrared and even radio wavelengths. These observations indicate three distinct features of the aurora: 1) filament-like oval structures fixed at the magnetic poles (~80°W (System III) in the south, ~180°W in the north), 2) spatially-continuous but transient aurora that fill these oval regions and 3) discrete spots associated with the magnetic footprints of Io and other Galilean satellites. However, observations in the thermal infrared indicate the aurora also modify the neutral atmosphere. Enhanced emission of CH4 is observed coincident with the auroral ovals and indicates heightened stratospheric temperatures possibly as a result of joule heating by the influx of charged particles. Stronger emission is also observed of C2H2, C2H4, C2H6 and even C6H6 though previous work has struggled to determine whether this is a temperature or compositional effect. In order to quantify the auroral effects on the neutral atmosphere and to support the 2016 Juno mission (which has no thermal infrared instrument) we have performed a retrieval analysis of IRTF-TEXES (Texas Echelon Cross Echelle Spectrograph, 5- to 25-μm) spectra obtained on Dec 11th 2014 near solar maximum. The instrument slit was scanned east-west across high latitudes in each hemisphere and Jupiter’s rotation was used to obtain ~360° longitudinal coverage. Spectra of H2 S(1), CH4, C2H2, C2H4 and C2H6 emission were measured at a resolving power of R = 85000, allowing a large vertical range in the atmosphere (100 - 0.001 mbar) to be sounded. Preliminary retrievals of the vertical temperature profile from H2 S(1) and CH4 measurements at 60°N, 180°W (on aurora), in comparison to 60°N, 60°W (quiescent

  19. Pyronaridine for treatment of Plasmodium ovale and Plasmodium malariae infections.

    OpenAIRE

    Ringwald, P; Bickii, J; Same-Ekobo, A.; Basco, L K

    1997-01-01

    The clinical efficacy of oral pyronaridine was assessed in 22 symptomatic Cameroonian patients infected with Plasmodium ovale or Plasmodium malariae. All patients were cured on or before day 4. In vitro drug assays confirmed the sensitivity of P. ovale and P. malariae isolates to chloroquine and pyronaridine.

  20. Plasmodium ovale infection in Malaysia: first imported case

    Directory of Open Access Journals (Sweden)

    T Thiruventhiran

    2010-10-01

    Full Text Available Abstract Background Plasmodium ovale infection is rarely reported in Malaysia. This is the first imported case of P. ovale infection in Malaysia which was initially misdiagnosed as Plasmodium vivax. Methods Peripheral blood sample was first examined by Giemsa-stained microscopy examination and further confirmed using a patented in-house multiplex PCR followed by sequencing. Results and Discussion Initial results from peripheral blood smear examination diagnosed P. vivax infection. However further analysis using a patented in-house multiplex PCR followed by sequencing confirmed the presence of P. ovale. Given that Anopheles maculatus and Anopheles dirus, vectors of P. ovale are found in Malaysia, this finding has significant implication on Malaysia's public health sector. Conclusions The current finding should serve as an alert to epidemiologists, clinicians and laboratory technicians in the possibility of finding P. ovale in Malaysia. P. ovale should be considered in the differential diagnosis of imported malaria cases in Malaysia due to the exponential increase in the number of visitors from P. ovale endemic regions and the long latent period of P. ovale. It is also timely that conventional diagnosis of malaria via microscopy should be coupled with more advanced molecular tools for effective diagnosis.

  1. Percutaneous closure of the patent foramen ovale.

    Science.gov (United States)

    Surmely, J-F; Meier, B

    2007-10-01

    A patent foramen ovale (PFO) is a common finding present in 25% of the population. A relationship between PFO and several clinical conditions such as stroke, migraine, platypnea-orthodeoxia syndrome, neurological decompression illness in divers, high altitude pulmonary edema, sleep apnea, and economy class syndrome have been documented. Observational non-randomized studies have shown percutaneous PFO closure more effective than medical treatment for stroke prevention, in particular in patients with complete closure as well as in patients with more than one cerebrovascular event at baseline. In the case of migraine, PFO closure has been shown to result in a marked reduction in migraine burden or migraine days. PFO anatomy, epidemiological data on associated clinical conditions, comparison between percutaneous closure and medical treatment, as well as the technical aspect of the procedure are described in this review. PMID:17912171

  2. Mapping auroral activity with Twitter

    Science.gov (United States)

    Case, N. A.; MacDonald, E. A.; Heavner, M.; Tapia, A. H.; Lalone, N.

    2015-05-01

    Twitter is a popular, publicly accessible, social media service that has proven useful in mapping large-scale events in real time. In this study, for the first time, the use of Twitter as a measure of auroral activity is investigated. Peaks in the number of aurora-related tweets are found to frequently coincide with geomagnetic disturbances (detection rate of 91%). Additionally, the number of daily aurora-related tweets is found to strongly correlate with several auroral strength proxies (ravg≈0.7). An examination is made of the bias for location and time of day within Twitter data, and a first-order correction of these effects is presented. Overall, the results suggest that Twitter can provide both specific details about an individual aurora and accurate real-time indication of when, and even from where, an aurora is visible.

  3. On the formation of auroral arcs

    International Nuclear Information System (INIS)

    A new mechanism for auroral arc formation is presented. The characteristic linear shape of auroral arcs is determined by magnetically connected plasma clouds in the distant equatorial magnetosphere. These clouds originate as high speed plasma beams in the magnetotail and in the solar wind. It is found that the free energy for driving an auroral arc is provided by the difference of pressure between the cloud and the ambient plasma. (author)

  4. Auroral and photoelectron fluxes in cometary ionospheres

    International Nuclear Information System (INIS)

    The analytical yield spectrum method has been used to ascertain photoelectron and auroral electron fluxes in cometary ionospheres, with a view to determining the effects of cometocentric distances, solar zenith angle, and solar minimum and maximum conditions. Auroral electron fluxes are thus calculated for monoenergetic and observed primary electron spectra; auroral electrons are found to make a larger contribution to the observed electron spectrum than EUV-generated photoelectrons. Good agreement is established with extant theoretical works. 55 refs

  5. Analysis of Jupiter's Oval BA: A Streamlined Approach

    Science.gov (United States)

    Sussman, Michael G.; Chanover, Nancy J.; Simon-Miller, Amy A.; Vasavada, Ashwin R.; Beebe, Reta F.

    2010-01-01

    We present a novel method of constructing streamlines to derive wind speeds within jovian vortices and demonstrate its application to Oval BA for 2001 pre-reddened Cassini flyby data, 2007 post-reddened New Horizons flyby data, and 1998 Galileo data of precursor Oval DE. Our method, while automated, attempts to combine the advantages of both automated and manual cloud tracking methods. The southern maximum wind speed of Oval BA does not show significant changes between these data sets to within our measurement uncertainty. The northern maximum dries appear to have increased in strength during this time interval, tvhich likely correlates with the oval's return to a symmetric shape. We demonstrate how the use of closed streamlines can provide measurements of vorticity averaged over the encircled area with no a priori assumptions concerning oval shape. We find increased averaged interior vorticity between pre- and post-reddened Oval BA, with the precursor Oval DE occupying a middle value of vorticity between these two.

  6. GPS phase scintillation during the geomagnetic storm of March 17, 2015: The relation to auroral electrojet currents

    DEFF Research Database (Denmark)

    Prikryl, Paul; Ghoddousi-Fard, Reza; Connors, Martin;

    -enhanced plasma density (SED) and in the auroral oval during energetic particle precipitation events, substorms and pseudo-breakups in particular. In this paper we examine the relation to auroral electrojet currents observed by arrays of ground-based magnetometers and energetic particle precipitation observed...... mass ejections compounded by high-speed plasma streams from coronal holes. Geomagnetic storm of March 17, 2015 was the largest in the current solar cycle. The high-latitude ionosphere dynamics is studied using arrays of ground-based instruments including GPS receivers, HF radars, ionosondes, riometers...... by DMSP satellites. Equivalent ionospheric currents (EICs) are obtained from ground magnetometer data using the spherical elementary currents systems (SECS) technique developed by Amm and Viljanen (1999) that has been applied over the entire North American ground magnetometer network by Weygand et al...

  7. Reconstruction of Fine Scale Auroral Dynamics

    CERN Document Server

    Hirsch, Michael; Zettergren, Matthew; Dahlgren, Hanna; Goenka, Chhavi; Akbari, Hassanali

    2015-01-01

    We present a feasibility study for a high frame rate, short baseline auroral tomographic imaging system useful for estimating parametric variations in the precipitating electron number flux spectrum of dynamic auroral events. Of particular interest are auroral substorms, characterized by spatial variations of order 100 m and temporal variations of order 10 ms. These scales are thought to be produced by dispersive Alfv\\'en waves in the near-Earth magnetosphere. The auroral tomography system characterized in this paper reconstructs the auroral volume emission rate to estimate the characteristic energy and location in the direction perpendicular to the geomagnetic field of peak electron precipitation flux using a distributed network of precisely synchronized ground-based cameras. As the observing baseline decreases, the tomographic inverse problem becomes highly ill-conditioned; as the sampling rate increases, the signal-to-noise ratio degrades and synchronization requirements become increasingly critical. Our a...

  8. Advanced Stellar Compass Summary for the Auroral Lites mission

    DEFF Research Database (Denmark)

    Jørgensen, John Leif

    1998-01-01

    This document provides technical and managerial information about the Advanced Stellar Compass and its possible use in the Auroral Lites Project.The Auroral Lites is a NASA project.......This document provides technical and managerial information about the Advanced Stellar Compass and its possible use in the Auroral Lites Project.The Auroral Lites is a NASA project....

  9. OVATION Prime-2013: Extension of auroral precipitation model to higher disturbance levels

    Science.gov (United States)

    Newell, P. T.; Liou, K.; Zhang, Y.; Sotirelis, T.; Paxton, L. J.; Mitchell, E. J.

    2014-06-01

    OVATION Prime (OP) is an auroral precipitation model parameterized by solar wind driving. Distinguishing features of the model include an optimized solar wind-magnetosphere coupling function (dΦMP/dt) which predicts auroral power significantly better than Kp or other traditional parameters, the separation of aurora into categories (diffuse aurora, monoenergetic, broadband, and ion), the inclusion of seasonal variations, and separate parameter fits for each magnetic latitude (MLAT) × magnetic local time (MLT) bin, thus permitting each type of aurora and each location to have differing responses to season and solar wind input—as indeed they do. We here introduce OVATION Prime-2013, an upgrade to the 2010 version currently widely available. The most notable advantage of OP-2013 is that it uses UV images from the GUVI instrument on the satellite TIMED for high disturbance levels (dΦMP/dt > 1.2 MWb/s which roughly corresponds to Kp = 5+ or 6-). The range of validity is approximately 0 power from Polar UVI. Over the common range of validity of OP-2010 and OP-2013, the two models predict auroral power essentially identically, primarily because hemispheric power calculations were done in a way to minimize the impact of OP-2010s noise. To quantitatively demonstrate the improvement at high disturbance levels would require multiple very large substorms, which are rare, and insufficiently present in the limited data set of Polar UVI hemispheric power values. Nonetheless, although OP-2010 breaks down in a variety of ways above Kp = 5+ or 6-, OP-2013 continues to show the auroral oval advancing equatorward, at least to 55° MLAT or a bit less, and OP-2013 does not develop spurious large noise patches. We will also discuss the advantages and disadvantages of other precipitation models more generally, as no one model fits best all possible uses.

  10. Dayside convection and auroral morphology during an interval of northward interplanetary magnetic field

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    Full Text Available We investigate the dayside auroral dynamics and ionospheric convection during an interval when the interplanetary magnetic field (IMF had predominantly a positive Bz component (northward IMF but varying By. Polar UVI observations of the Northern Hemisphere auroral emission indicate the existence of a region of luminosity near local noon at latitudes poleward of the dayside auroral oval, which we interpret as the ionospheric footprint of a high-latitude reconnection site. The large field-of-view afforded by the satellite-borne imager allows an unprecedented determination of the dynamics of this region, which has not previously been possible with ground-based observations. The location of the emission in latitude and magnetic local time varies in response to changes in the orientation of the IMF; the cusp MLT and the IMF By component are especially well correlated, the emission being located in the pre- or post-noon sectors for By < 0 nT or By > 0 nT, respectively. Simultaneous ground-based observations of the ionospheric plasma drift are provided by the CUTLASS Finland HF coherent radar. For an interval of IMF By approx 0 nT, these convection flow measurements suggest the presence of a clockwise-rotating lobe cell contained within the pre-noon dayside polar cap, with a flow reversal closely co-located with the high-latitude luminosity region. This pattern is largely consistent with recent theoretical predictions of the convection flow during northward IMF. We believe that this represents the first direct measurement of the convection flow at the imaged location of the footprint of the high-latitude reconnection site.

    Key words: Magnetospheric physics (auroral phenomena; magnetopause · cusp · and boundary layers; plasma convection

  11. Plasmodium ovale infection in Malaysia: first imported case

    OpenAIRE

    T Thiruventhiran; Chew Ching; Mahmud Rohela; Lim Yvonne AL; Chua Kek

    2010-01-01

    Abstract Background Plasmodium ovale infection is rarely reported in Malaysia. This is the first imported case of P. ovale infection in Malaysia which was initially misdiagnosed as Plasmodium vivax. Methods Peripheral blood sample was first examined by Giemsa-stained microscopy examination and further confirmed using a patented in-house multiplex PCR followed by sequencing. Results and Discussion Initial results from peripheral blood smear examination diagnosed P. vivax infection. However fur...

  12. Chimpanzee malaria parasites related to Plasmodium ovale in Africa.

    Directory of Open Access Journals (Sweden)

    Linda Duval

    Full Text Available Since the 1970's, the diversity of Plasmodium parasites in African great apes has been neglected. Surprisingly, P. reichenowi, a chimpanzee parasite, is the only such parasite to have been molecularly characterized. This parasite is closely phylogenetically related to P. falciparum, the principal cause of the greatest malaria burden in humans. Studies of malaria parasites from anthropoid primates may provide relevant phylogenetic information, improving our understanding of the origin and evolutionary history of human malaria species. In this study, we screened 130 DNA samples from chimpanzees (Pan troglodytes and gorillas (Gorilla gorilla from Cameroon for Plasmodium infection, using cytochrome b molecular tools. Two chimpanzees from the subspecies Pan t. troglodytes presented single infections with Plasmodium strains molecularly related to the human malaria parasite P. ovale. These chimpanzee parasites and 13 human strains of P. ovale originated from a various sites in Africa and Asia were characterized using cytochrome b and cytochrome c oxidase 1 mitochondrial partial genes and nuclear ldh partial gene. Consistent with previous findings, two genetically distinct types of P. ovale, classical and variant, were observed in the human population from a variety of geographical locations. One chimpanzee Plasmodium strain was genetically identical, on all three markers tested, to variant P. ovale type. The other chimpanzee Plasmodium strain was different from P. ovale strains isolated from humans. This study provides the first evidence of possibility of natural cross-species exchange of P. ovale between humans and chimpanzees of the subspecies Pan t. troglodytes.

  13. Hemispheric Assymeries in Auroral Precipitation

    Science.gov (United States)

    Mende, S. B.

    2014-12-01

    It is widely accepted that the space weather related electrodynamic forcing of the geospace environment acts through the high geomagnetic latitude regions. At high latitudes inter-hemispheric asymmetries are largely due to the differences in solar illumination, the direction of the solar wind and interplanetary magnetic field components and to a lesser extent, due to differences between the two hemispheric internal fields. So far most research regarding interhemispheric differences concentrated on learning about the basic magnetosphere-ionosphere coupling mechanisms. It has been well established that sunlit conditions affect the energy flux of auroral precipitation resulting from the reduction in the mean energy of the auroral electrons in the sunlit summer hemisphere. This can be explained by the partial shorting out of the particle accelerating fields by the sunlight induced conductivity. It has also been found that sunlit conditions reduce the particle fluxes and therefore the associated field aligned currents. Unless the precipitation-induced conductivities overwhelm the sunlit component of conductivity, this would imply that the magnetospheric current generator responds to the ionospheric load in a highly non-linear manner. Interhemispheric currents may also play an important role that has not been fully explored. Interhemispheric asymmetries in substorm morphology have been explored critically because conjugacy implies that substorms have a common source at equatorial latitudes. In some cases the lack of conjugacy of substorms could be explained by considering the magnitude and direction of the IMF.

  14. Turbulent acceleration of auroral electrons

    International Nuclear Information System (INIS)

    It is shown that the characteristic peak in the auroral electron velocity distribution can be generated stochastically through resonant interactions with lower-hybrid electrostatic turbulence. The peak itself is shown to be a direct consequence of restrictions imposed on reflexion of electron velocities in the frame of reference of individual wave packets by the limitation in group velocity. A Monte-Carlo model demonstrates how the various properties of the acceleration region are reflected in the resultant electron distribution. It is shown, in particular, that the width of the peak is governed by the amplitude of the turbulence, while the amplitude of the peak reflects the column density of wave energy. Electron distributions encountered within three auroral arcs are interpreted to yield order of magnitude estimates of the amplitude and rms electric field of lower-hybrid wave packets. The velocities and frequencies of the resonant waves, the net electric field, the column density of wave energy and the electric-field energy density are also estimated. The results are found to be consistent with available electric-field measurements. A general broadening of the electron distribution caused by less systematic interactions between electrons and wave packets is shown to have a negligible effect on the peak resulting from the reflexion process; it does, though, lead to the creation of a characteristic high-energy tail. (author)

  15. Patent foramen ovale (PFO), stroke and pregnancy.

    Science.gov (United States)

    Chen, Lei; Deng, Wenjun; Palacios, Igor; Inglessis-Azuaje, Ignacio; McMullin, David; Zhou, Dong; Lo, Eng H; Buonanno, Ferdinando; Ning, MingMing

    2016-06-01

    Patent foramen ovale (PFO)-related stroke is increasingly recognized as an important etiology of ischemic embolic stroke-accounting for up to 50% of strokes previously considered 'cryptogenic' or with an unknown mechanism. As a 'back door to the brain,' PFO can allow venous clots to enter arterial circulation via interatrial right-to-left shunting, potentially resulting in ischemic stroke. We observe that clinically, PFO-related stroke affects women of childbearing age, and that pregnancy-owing to major changes in hemocoagulative, hormonal, and cardiovascular parameters-can enhance stroke risks. However, no systematic study has been performed and little is known regarding complications, pregnancy outcomes and treatment for PFO-related stroke during pregnancy. To identify and characterize the complications and clinical outcomes related to PFOs during pregnancy, we performed a literature review and analysis from all reported cases of pregnancy with PFO-related complications in the medical literature from 1970 to 2015. We find that during pregnancy and post-partum, PFO is associated with complications affecting multiple organs, including the brain, heart and lung. The three principal complications reported are stroke, pulmonary emboli and myocardial infarction. In contrast to other pregnancy-related stroke etiologies, which peak during later pregnancy and postpartum, PFO-related stroke peaks during early pregnancy (first and second trimester-60%), and most patients had good neurological outcome (77%). In patients with PFO with recurrent stroke during pregnancy, additional key factors include high-risk PFO morphology (atrial septal aneurysm), larger right-to-left shunt, multiple gestation and concurrent hypercoagulability. Compared to strokes of other etiologies during pregnancy, most PFO stroke patients experienced uneventful delivery (93%) of healthy babies with a good clinical outcome. We conclude with recommended clinical treatment strategies for pregnant patients

  16. 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

    Full Text Available

    Abstract. Simultaneous DMSP F7 and Viking satellite measurements of the dawnside high-latitude auroral energy electron and ion precipitation show that the region of the low and middle altitude auroral precipitation consists of three characteristic plasma regimes. The recommendation of the IAGA Working Group IIF/III4 at the IAGA Assembly in Boulder, July 1995 to decouple the nomenclature of ionospheric populations from magnetospheric population is used for their notation. The most equatorial regime is the Diffuse Auroral Zone (DAZ of diffuse spatially unstructured precipitating electrons. It is generated by the plasma injection to the inner magnetosphere in the nightside and the subsequent drift plasma to the dawnside around the Earth. Precipitating particles have a hard spectrum with typical energies of electrons and ions of more than 3 keV. In the DAZ, the ion pitch-angle distribution is anisotropic, with the peak near 90°. The next part is the Auroral Oval (AO, a structured electron regime which closely resembles the poleward portion of the night-side auroral oval. The typical electron energy is several keV, and the ion energy is up to 10 keV. Ion distributions are pre-dominantly isotropic. In some cases, this plasma regime may be absent in the pre-noon sector. Poleward of the Auroral Oval, there is the Soft Small Scale Luminosity (SSSL regime. It is caused by structured electron and ion precipitation with typical electron energy of about 0.3 keV and ion energy of about 1 keV. The connection of these low-altitude regimes with plasma domains of the distant magnetosphere is discussed. For mapping of the plasma regimes to the equatorial plane of the magnetosphere, the empirical model by Tsyganenko (1995 and the conceptual model by Alexeev et al. (1996 are used. The DAZ is mapped along the magnetic field lines to the Remnant Layer (RL, which is located in the outer radiation belt region; the zone of structured

  17. Statistical analysis of extreme auroral electrojet indices

    Science.gov (United States)

    Nakamura, Masao; Yoneda, Asato; Oda, Mitsunobu; Tsubouchi, Ken

    2015-09-01

    Extreme auroral electrojet activities can damage electrical power grids due to large induced currents in the Earth, degrade radio communications and navigation systems due to the ionospheric disturbances and cause polar-orbiting satellite anomalies due to the enhanced auroral electron precipitation. Statistical estimation of extreme auroral electrojet activities is an important factor in space weather research. For this estimation, we utilize extreme value theory (EVT), which focuses on the statistical behavior in the tail of a distribution. As a measure of auroral electrojet activities, auroral electrojet indices AL, AU, and AE, are used, which describe the maximum current strength of the westward and eastward auroral electrojets and the sum of the two oppositely directed in the auroral latitude ionosphere, respectively. We provide statistical evidence for finite upper limits to AL and AU and estimate the annual expected number and probable intensity of their extreme events. We detect two different types of extreme AE events; therefore, application of the appropriate EVT analysis to AE is difficult.

  18. Waterhole: An auroral-ionosphere perturbation experiment

    Science.gov (United States)

    Whalen, B. A.; Yau, A. W.; Creutzberg, F.; Pongratz, M. B.

    A sounding rocket carrying 100 kg of high explosives and plasma diagnostic instrumentation was launched from Churchill Research Range on 6 April 1980 over a premidnight auroral arc. The object of the experiment was to produce an ionospheric hole or plasma density depletion at about 300 km altitude on field lines connected to an auroral arc. The plasma depletion is produced when the explosive by-products (mostly water) charge-exchange with the ambient O+ ions and then rapidly recombine. It was speculated that the presence of the "hole" would interfere with the field-aligned current systems associated with the arc and would in turn perturb the auroral source mechanism. The release occurred about 10 km poleward of the auroral arc fieldlines. As expected, a large ionospheric hole was detected by rocket-borne plasma sensors. Within a few seconds following the release (a) the energetic electron precipitation observed in the hole dropped to background levels, (b) the luminosity of the auroral arc observed by a ground-based auroral scanning photometer decreased by a factor of two, and (c) the ionospheric E region density below the hole decayed at a rate consistent with a sudden reduction in particle precipitation. The simultaneous onset of these gross changes in electron precipitation coincident with the release strongly suggests a cause and effect relationship. In particular, these results suggest that the ionospheric plasma and the field-aligned current systems play a crucial role in the auroral acceleration process.

  19. Auroral Phenomena in Brown Dwarf Atmospheres

    Science.gov (United States)

    Pineda, J. Sebastian; Hallinan, Gregg

    2016-01-01

    Since the unexpected discovery of radio emission from brown dwarfs some 15 years ago, investigations into the nature of this emission have revealed that, despite their cool and neutral atmospheres, brown dwarfs harbor strong kG magnetic fields, but unlike the warmer stellar objects, they generate highly circularly polarized auroral radio emission, like the giant planets of the Solar System. Our recent results from Keck LRIS monitoring of the brown dwarf LSR1835+32 definitively confirm this picture by connecting the auroral radio emission to spectroscopic variability at optical wavelengths as coherent manifestations of strong large-scale magnetospheric auroral current systems. I present some of the results of my dissertation work to understand the nature brown dwarf auroral phenomena. My efforts include a survey of Late L dwarfs and T dwarfs, looking for auroral Hα emission and a concurrent survey looking for the auroral emission of H3+ from brown dwarfs with radio pulse detections. I discuss the potential connection of this auroral activity to brown dwarf weather phenomena and how brown dwarf aurorae may differ from the analogous emission of the magnetized giant planets in the Solar System.

  20. Auroral Morphologies of Jupiter and Saturn

    OpenAIRE

    Grodent, Denis

    2015-01-01

    We review the principal differences and similarities of the morphologies of Jupiter and Saturn's auroral emissions. We then show some examples of UV images that are expected to be acquired with Cassini UVIS at Saturn and Juno UVS at Jupiter.

  1. Auroral electrodynamics of plasma boundary regions

    OpenAIRE

    Liléo, Sónia

    2009-01-01

    The electrodynamic coupling between the auroral ionosphere and the magnetosphere is the main subject of this thesis. Satellite measurements of electric and magnetic fields and of charged particles are used to explore three distinct plasma boundaries, magnetically linked to the nightside auroral ionosphere. These boundaries are the inner edge of the plasma sheet (PS), and the inner and the outer edges of the plasma sheet boundary layer (PSBL). Strong ionospheric electric fields with amplitudes...

  2. Investigations of auroral dynamics: techniques and results

    International Nuclear Information System (INIS)

    This study is an experimental investigation of the dynamics of the aurora, describing both the systems developed for the optical measurements and the results obtained. It is found that during a auroral arc deformation, a fold travelling eastward along the arc is associated with an enhanced F-region ion temperature of 2700 K, measured by EISCAT, indicative of enhanced ionspheric electric fields. It is shown that for an auroral break-up, the large-scale westward travelling surge (WTS) is the last developed spiral in a sequence of spiral formations. It is proposed that the Kelvin-Helmholtz instability is the responsible process. In another event it is shown that large-amplitude long-lasting pulsations, observed both in ground-based magnetic field and photometer recordings, correspond to strong modulations of the particle intensity at the equatorial orbit (6.6 Re). In this event a gradual transition occurs between pulses classified as Ps6/auroral torches toward pulses with characteristics of substorms. The observations are explained by the Kelvin-Helmholtz instability in a magnetospheric boundary layer. The meridional neutral wind, at about 240 km altitude, is found to be reduced prior to or at the onset of auroral activity. These findings are suggestive of large-scale reconfigurations of the ionspheric electric fields prior to auroral onsets. A new real time triangulation technique developed to determine the altitude of auroral arcs is presented, and an alternative method to analyze incoherent scatter data is discussed. (With 46 refs.) (author)

  3. Observation of auroral fading before breakup

    International Nuclear Information System (INIS)

    We have obtained detailed observations of the onset of auroral breakup using a variety of instruments with time resolution of some tens of seconds. Rapid sequences of all-sky photographs, and fast meridian scans by photometers, show that breakup is usually preceded by moderate brightening, followed by fading of the auroral brightness lasting one or two minutes, before the actual breakup itself. At the time of the fading there is a brief darkening of the poleward sky. Often the breakup is preceded by one or more rapid intensifications, each one preceded by local fading. Pseudo-breakups may also occur without the development of a major event. A bonafide breakup may begin on the fading arc, on an adjacent arc, or in an entirely new region nearby. This optical activity is closely correlated with the development of auroral radar echoes, suggesting that variations in the ionospheric and magnetospheric electric and magnetic fields are responsible for the observed auroral variations. Data from the IMS magnetometer network provide some indication of a correlated response by the local auroral and ionospheric current, although this could be partly due to changes in conductivity. Riometer recordings show a slow decrease in ionsperic radio wave absorption over a period of about ten minutes prior to breakup, with the largest decrease essentially to quiet-time values in the region of auroral fading and subsequent breakup. The implications of these observations regarding the trigger mechanism for the expansion phase of a magnetospheric substorm are discussed. (author)

  4. Auroral current systems in Saturn's magnetosphere: comparison of theoretical models with Cassini and HST observations

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2008-09-01

    Full Text Available The first simultaneous observations of fields and plasmas in Saturn's high-latitude magnetosphere and UV images of the conjugate auroral oval were obtained by the Cassini spacecraft and the Hubble Space Telescope (HST in January 2007. These data have shown that the southern auroral oval near noon maps to the dayside cusp boundary between open and closed field lines, associated with a major layer of upward-directed field-aligned current (Bunce et al., 2008. The results thus support earlier theoretical discussion and quantitative modelling of magnetosphere-ionosphere coupling at Saturn (Cowley et al., 2004, that suggests the oval is produced by electron acceleration in the field-aligned current layer required by rotational flow shear between strongly sub-corotating flow on open field lines and near-corotating flow on closed field lines. Here we quantitatively compare these modelling results (the "CBO" model with the Cassini-HST data set. The comparison shows good qualitative agreement between model and data, the principal difference being that the model currents are too small by factors of about five, as determined from the magnetic perturbations observed by Cassini. This is suggested to be principally indicative of a more highly conducting summer southern ionosphere than was assumed in the CBO model. A revised model is therefore proposed in which the height-integrated ionospheric Pedersen conductivity is increased by a factor of four from 1 to 4 mho, together with more minor adjustments to the co-latitude of the boundary, the flow shear across it, the width of the current layer, and the properties of the source electrons. It is shown that the revised model agrees well with the combined Cassini-HST data, requiring downward acceleration of outer magnetosphere electrons through a ~10 kV potential in the current layer at the open-closed field line boundary to produce an auroral oval of ~1° width with UV emission intensities of a few tens of kR.

  5. Interhemispheric asymmetries in the occurrence of magnetically conjugate sub-auroral polarisation streams

    Directory of Open Access Journals (Sweden)

    M. L. Parkinson

    2005-06-01

    Full Text Available Earthward injections of energetic ions and electrons mark the onset of magnetospheric substorms. In the inner magnetosphere (L${sim}$4, the energetic ions drift westward and the electrons eastward, thereby enhancing the equatorial ring current. Wave-particle interactions can accelerate these particles to radiation belt energies. The ions are injected slightly closer to Earth in the pre-midnight sector, leading to the formation of a radial polarisation field in the inner magnetosphere. This maps to a poleward electric field just equatorward of the auroral oval in the ionosphere. The poleward electric field is subsequently amplified by ionospheric feedback, thereby producing auroral westward flow channels (AWFCs. In terms of electric field strength, AWFCs are the strongest manifestation of substorms in the ionosphere. Because geomagnetic flux tubes are essentially equi-potentials, similar AWFC signatures should be observed simultaneously in the Northern and Southern Hemispheres. Here we present magnetically conjugate SuperDARN radar observations of AWFC activity observed in the pre-midnight sector during two substorm intervals including multiple onsets during the evening of 30 November 2002. The Northern Hemisphere observations were made with the Japanese radar located at King Salmon, Alaska (57$^{circ}$$Lambda $, and the Southern Hemisphere observations with the Tasman International Geospace Environment Radar (TIGER located at Bruny Island, Tasmania (

  6. Relevanz eines persistierenden Foramen ovale bei pulmonal arterieller Hypertonie

    OpenAIRE

    Mascher, Ingo Frederik

    2015-01-01

    Die pulmonal arterielle Hypertonie (PAH) ist eine chronische Erkrankung der Blutgefäße in den Lungen. Sie kann unbehandelt innerhalb weniger Jahre durch ein Cor pulmonale chronicum mit konsekutivem Rechtsherzversagen zum Tode führen. Ein persistierendes Foramen ovale cordis (PFO) ist ein in den meisten Fällen wenige Millimeter kleines funktionell verschlossenes Loch. Bestimmte Druckverhältnisse, z.B. eine PAH, können das Foramen ovale öffnen und somit einen kardialen Rechts-Links-Shunt in...

  7. Origins of the Earth's Diffuse Auroral Precipitation

    Science.gov (United States)

    Ni, Binbin; Thorne, Richard M.; Zhang, Xiaojia; Bortnik, Jacob; Pu, Zuyin; Xie, Lun; Hu, Ze-jun; Han, Desheng; Shi, Run; Zhou, Chen; Gu, Xudong

    2016-02-01

    The Earth's diffuse auroral precipitation provides the major source of energy input into the nightside upper atmosphere and acts as an essential linkage of the magnetosphere-ionosphere coupling. Resonant wave-particle interactions play a dominant role in the scattering of injected plasma sheet electrons, leading to the diffuse auroral precipitation. We review the recent advances in understanding the origin of the diffuse aurora and in quantifying the exact roles of various magnetospheric waves in producing the global distribution of diffuse auroral precipitation and its variability with the geomagnetic activity. Combined scattering by upper-and lower-band chorus accounts for the most intense inner magnetospheric electron diffuse auroral precipitation on the nightside. Dayside chorus can be responsible for the weaker dayside electron diffuse auroral precipitation. Pulsating auroras, the dynamic auroral structures embedded in the diffuse aurora, can be mainly caused by modulation of the excitation of lower band chorus due to macroscopic density variations in the magnetosphere. Electrostatic electron cyclotron harmonic waves are an important or even dominant cause for the nightside electron diffuse auroral precipitation beyond {˜}8Re and can also contribute to the occurrence of the pulsating aurora at high L-shells. Scattering by electromagnetic ion cyclotron waves could quite possibly be the leading candidate responsible for the ion precipitation (especially the reversed-type events of the energy-latitude dispersion) in the regions of the central plasma sheet and ring current. We conclude the review with a summary of current understanding, outstanding questions, and a number of suggestions for future research.

  8. Origins of the Earth's Diffuse Auroral Precipitation

    Science.gov (United States)

    Ni, Binbin; Thorne, Richard M.; Zhang, Xiaojia; Bortnik, Jacob; Pu, Zuyin; Xie, Lun; Hu, Ze-jun; Han, Desheng; Shi, Run; Zhou, Chen; Gu, Xudong

    2016-04-01

    The Earth's diffuse auroral precipitation provides the major source of energy input into the nightside upper atmosphere and acts as an essential linkage of the magnetosphere-ionosphere coupling. Resonant wave-particle interactions play a dominant role in the scattering of injected plasma sheet electrons, leading to the diffuse auroral precipitation. We review the recent advances in understanding the origin of the diffuse aurora and in quantifying the exact roles of various magnetospheric waves in producing the global distribution of diffuse auroral precipitation and its variability with the geomagnetic activity. Combined scattering by upper-and lower-band chorus accounts for the most intense inner magnetospheric electron diffuse auroral precipitation on the nightside. Dayside chorus can be responsible for the weaker dayside electron diffuse auroral precipitation. Pulsating auroras, the dynamic auroral structures embedded in the diffuse aurora, can be mainly caused by modulation of the excitation of lower band chorus due to macroscopic density variations in the magnetosphere. Electrostatic electron cyclotron harmonic waves are an important or even dominant cause for the nightside electron diffuse auroral precipitation beyond {˜}8Re and can also contribute to the occurrence of the pulsating aurora at high L-shells. Scattering by electromagnetic ion cyclotron waves could quite possibly be the leading candidate responsible for the ion precipitation (especially the reversed-type events of the energy-latitude dispersion) in the regions of the central plasma sheet and ring current. We conclude the review with a summary of current understanding, outstanding questions, and a number of suggestions for future research.

  9. Auroral pulsations and accompanying VLF emissions

    Directory of Open Access Journals (Sweden)

    V. R. Tagirov

    Full Text Available Results of simultaneous TV observations of pulsating auroral patches and ELF-VLF-emissions in the morning sector carried out in Sodankylä (Finland on February 15, 1991 are presented. Auroral pulsating activity was typical having pulsating patches with characteristic periods of about 7 s. Narrow-band hiss emissions and chorus elements at intervals of 0.3–0.4 s formed the main ELF-VLF activity in the frequency range 1.0–2.5 kHz at the same time. The analysis of auroral images with time resolution of 0.04 s allowed perfectly separate analysis of spatial and temporal variations in the auroral luminosity. Mutual correspondence between the behaviour of the luminous auroral patches and the appearance of ELF noise type hiss emissions and VLF chorus trains was found in two intervals chosen for analysis. While the hiss emissions were associated with the appearance of luminosity inside a limited area close to the zenith, the structured VLF emissions were accompanied by rapid motion of luminosity inside the area. The spatial dimension of the pulsating area was about 45–50 km and luminosity propagated inside it with velocity of about 10–12 kms. We discuss a new approach to explain the 5–15 s auroral pulsation based on the theory of flowing cyclotron maser and relaxation characteristics of ionosphere.

    Key words. Magnetospheric physics (auroral phenomena; magnetosphere-ionosphere interactions · Space plasma physics (wave-particle interactions

  10. 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.

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

    International Nuclear Information System (INIS)

    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.

  12. Auroral and magnetic variations in the polar cusp and cleft. Signatures of magnetopause boundary layer dynamics

    International Nuclear Information System (INIS)

    By combining continous ground-based observations of polar cleft/cusp auroras and local magnetic variations with electromagnetic parameters obtained from satellites in polar orbit (low-altitude cleft/cusp) and in the magnetosheath/interplanetary space, different electrodynamic processes in the polar cleft/cusp have been investigated. One of the more controversial questions in this field is related to the observed shifts in latitude of cleft/cusp auroras and the relationships with the interplanetary magnetic field (IMF) orientation, local magnetic disturbances (DP2 and DPY modes) and magnetospheric substorms. A new approach which may contribute to clarifying these complicated relationships, simultaneous groundbased observations of the midday and evening-midnight sectors of the auroral oval, is illustrated. A related topic is the spatial relationship between the cleft/cusp auroras and the ionospheric convection currents. A characteristic feature of the polar cusp and cleft regions during negative IMF Bz is repeated occurrence of certain short-lived auroral structures moving in accordance with the local convection pattern. Satellite measurements of particle precipitation, magnetic field and ion drift components permit detailed investigations of the electrodynamics of these cusp/cleft structures. Information on electric field components, Birkeland currents, Poynting flux, height-integrated Pedersen conductivity and Joule heat dissipation rate has been derived. These observations are discussed in relation to existing models of temporal plasma injections from the magnetosheath

  13. Current-voltage and kinetic energy flux relations for relativistic field-aligned acceleration of auroral electrons

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2006-03-01

    Full Text Available Recent spectroscopic observations of Jupiter's "main oval" auroras indicate that the primary auroral electron beam is routinely accelerated to energies of ~100 keV, and sometimes to several hundred keV, thus approaching the relativistic regime. This suggests the need to re-examine the classic non-relativistic theory of auroral electron acceleration by field-aligned electric fields first derived by Knight (1973, and to extend it to cover relativistic situations. In this paper we examine this problem for the case in which the source population is an isotropic Maxwellian, as also assumed by Knight, and derive exact analytic expressions for the field-aligned current density (number flux and kinetic energy flux of the accelerated population, for arbitrary initial electron temperature, acceleration potential, and field strength beneath the acceleration region. We examine the limiting behaviours of these expressions, their regimes of validity, and their implications for auroral acceleration in planetary magnetospheres (and like astrophysical systems. In particular, we show that for relativistic accelerating potentials, the current density increases as the square of the minimum potential, rather than linearly as in the non-relativistic regime, while the kinetic energy flux then increases as the cube of the potential, rather than as the square.

  14. Modes of high-latitude auroral conductance variability derived from DMSP energetic electron precipitation observations: Empirical orthogonal function analysis

    Science.gov (United States)

    McGranaghan, Ryan; Knipp, Delores J.; Matsuo, Tomoko; Godinez, Humberto; Redmon, Robert J.; Solomon, Stanley C.; Morley, Steven K.

    2015-12-01

    We provide the first ever characterization of the primary modes of ionospheric Hall and Pedersen conductance variability as empirical orthogonal functions (EOFs). These are derived from six satellite years of Defense Meteorological Satellite Program (DMSP) particle data acquired during the rise of solar cycles 22 and 24. The 60 million DMSP spectra were each processed through the Global Airlglow Model. Ours is the first large-scale analysis of ionospheric conductances completely free of assumption of the incident electron energy spectra. We show that the mean patterns and first four EOFs capture ˜50.1 and 52.9% of the total Pedersen and Hall conductance variabilities, respectively. The mean patterns and first EOFs are consistent with typical diffuse auroral oval structures and quiet time strengthening/weakening of the mean pattern. The second and third EOFs show major disturbance features of magnetosphere-ionosphere (MI) interactions: geomagnetically induced auroral zone expansion in EOF2 and the auroral substorm current wedge in EOF3. The fourth EOFs suggest diminished conductance associated with ionospheric substorm recovery mode. We identify the most important modes of ionospheric conductance variability. Our results will allow improved modeling of the background error covariance needed for ionospheric assimilative procedures and improved understanding of MI coupling processes.

  15. An Electron Microscope Study of the Yeast Pityrosporum ovale

    NARCIS (Netherlands)

    Kreger-van Rij, N.J.W.; Veenhuis, M.

    1970-01-01

    Cells of Pityrosporum ovale were prepared for electron microscopy by different methods of fixation and embedding, all of them causing some degree of damage to the cells. Apart from the usual organelles seen in other yeast cells, a body was found which showed an electron-dense outer layer and an elec

  16. The Auroral Zone: A citizen science project to classify auroral imaging data

    Science.gov (United States)

    Chaddock, D.; Spanswick, E.; Gillies, D. M.; Quinney, A.; Donovan, E.; Murray, M. S.

    2015-12-01

    Currently, over 40 million images of the aurora have been recorded by University of Calgary all-sky imagers. Analysis of these images is an important and crucial step in the advancement of auroral physics. The number of images waiting to be analyzed is expected to increase dramatically with the introduction of TREx (Transition Region Explorer), a new high resolution imaging network set to be deployed in late 2016. In order to classify large amounts of images in a short period of time, we have designed a citizen science project aimed at engaging the general public in auroral science, called "The Auroral Zone". This project facilitates a symbiotic relationship between the scientific community and the general public. Using the data from this website, a large database of classified auroral images will be created and then used for future analysis by the scientific community. In exchange, the general public can learn about the aurora and contribute to auroral physics in a tangible way. The ultimate aim of this project is to create an ever expanding database of all-sky images classified by arc type (i.e. single arc, diffuse aurora, multiple arc, etc.) and filtered for adverse viewing conditions (i.e. snow, rain, light pollution, etc). We aim to introduce "The Auroral Zone" into the school systems to interest young scientists in the spectacular natural phenomenon that defines the Canadian North. "The Auroral Zone" is a collaborative project between the University of Calgary, Canadian Space Agency, AuroraMAX, and Aurorasaurus.

  17. Auroral Electrojet Indices Designed to Provide a Global Measure, 2.5-Minute Intervals, of Auroral Zone Magnetic Activity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Auroral Electrojet index (AE) is designed to provide a global quantitative measure of auroral zone magnetic activity produced by enhanced ionospheric currents...

  18. Auroral Electrojet Index Designed to Provide a Global Measure, l-minute Intervals, of Auroral Zone Magnetic Activity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Auroral Electrojet index (AE) is designed to provide a global quantitative measure of auroral zone magnetic activity produced by enhanced ionospheric currents...

  19. Electrondynamics of the auroral E region

    International Nuclear Information System (INIS)

    This study concentrates on the signatures of the interaction process seen closest to the Earth - i.e. in the region where the visible aurora is produced. A number of experimental investigations are presented which look at details of the dynamics and electrodynamics of auroral ionisation features in the ionospheric E region. The studies are based primarily on measurement with the EISCAT UHF incoherent scatter radar which is located in northern Scandinavia. Initial calibration of the radar, and some measurements of the properties of the background atmosphere are described first. These are a necessary basis for the detailed studies which follow, which are of two aspects of auroral electrodynamics - substorms and aurorally-associated sporadic E layers. For the substorm studies, all-sky camera observations of the aurora over Scandinavia and ultra-violet images from the Viking satellite are used to identify the auroral forms corresponding to EISCAT measurements. This allows the determination of representative conductivities for the different auroral features which are characteristic of the substorm development. These conductivities are an important input for modelling studies of the electric current systems and have not previously been measured directly. Particle measurements from the Viking satellite are used together with EISCAT to determine the origin of the particles precipitated into the ionosphere during the energy-storage phase prior to the substorm. The sporadic E layers studies address the question of how ion layers and associated neutral sodium layers can be produced by some process which is common in association with auroral activity. Two candidates are considered - gravity waves and electric fields. (author)

  20. Axi-symmetric models of auroral current systems in Jupiter's magnetosphere with predictions for the Juno mission

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2008-12-01

    Full Text Available We develop two related models of magnetosphere-ionosphere coupling in the jovian system by combining previous models defined at ionospheric heights with magnetospheric magnetic models that allow system parameters to be extended appropriately into the magnetosphere. The key feature of the combined models is thus that they allow direct connection to be made between observations in the magnetosphere, particularly of the azimuthal field produced by the magnetosphere-ionosphere coupling currents and the plasma angular velocity, and the auroral response in the ionosphere. The two models are intended to reflect typical steady-state sub-corotation conditions in the jovian magnetosphere, and transient super-corotation produced by sudden major solar wind-induced compressions, respectively. The key simplification of the models is that of axi-symmetry of the field, flow, and currents about the magnetic axis, limiting their validity to radial distances within ~30 RJ of the planet, though the magnetic axis is appropriately tilted relative to the planetary spin axis and rotates with the planet. The first exploration of the jovian polar magnetosphere is planned to be undertaken in 2016–2017 during the NASA New Frontiers Juno mission, with observations of the polar field, plasma, and UV emissions as a major goal. Evaluation of the models along Juno planning orbits thus produces predictive results that may aid in science mission planning. It is shown in particular that the low-altitude near-periapsis polar passes will generally occur underneath the corresponding auroral acceleration regions, thus allowing brief examination of the auroral primaries over intervals of ~1–3 min for the main oval and ~10 s for narrower polar arc structures, while the "lagging" field deflections produced by the auroral current systems on these passes will be ~0.1°, associated with azimuthal fields above the ionosphere of a few hundred nT.

  1. Auroral Electrojet (AE, AL, AO, AU) - A Global Measure of Auroral Zone Magnetic Activity

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The AE index is derived from geomagnetic variations in the horizontal component observed at selected (10-13) observatories along the auroral zone in the northern...

  2. Recurrence of particles in static and time varying oval billiards

    International Nuclear Information System (INIS)

    Dynamical properties are studied for escaping particles, injected through a hole in an oval billiard. The dynamics is considered for both static and periodically moving boundaries. For the static boundary, two different decays for the recurrence time distribution were observed after exponential decay for short times: A changeover to: (i) power law or; (ii) stretched exponential. Both slower decays are due to sticky orbits trapped near KAM islands, with the stretched exponential apparently associated with a single group of large islands. For time dependent case, survival probability leads to the conclusion that sticky orbits are less evident compared with the static case. -- Highlights: ► We consider properties of escaping particles in an oval billiard. ► Two different decays for the recurrence time distribution were observed following an exponential decay for short times: a power law or stretched exponential. ► Time-dependent boundaries suppress the slower decay at later times.

  3. A selective tropism of transfused oval cells for liver

    Institute of Scientific and Technical Information of China (English)

    Jian-Zhi Chen; Hai Hong; Jin Xiang; Ling Xue; Guo-Qiang Zhao

    2003-01-01

    AIM: To explore the biological behaviors of hepatic oval cells after transfused into the circulation of experimental animals.METHODS: Oval cells from male SD rat were transfused into the circulation of a female rat which were treated by a 2-AAF/CCl4 program, through caudal vein. Sex-determining gene sry which located on Y chromosome was examined by PCR and in situ hybridization technique in liver, kidney and spleen of the experimental animals, respectively.RESULTS: The results of the cell-transplant experiment showed that the srygene was detectable only in the liver but not in spleen and kidney of the experimental rats, and no signals could be detected in the control animals. It can be also morphologically proved that some exogenous cells had migrated into the parenchyma of the liver and settled there.CONCLUSION: The result means that there are exogenous cells located in the liver of the experimental animal and the localization is specific to the liver. This indicates that some "signal molecules" must exist in the circulation of the rats treated by 2-AAF/CCl4. These "signal molecules" might play an important role in specific localization and differentiation of transfused oval cells.

  4. Comparative anatomy of the foramen ovale in the Suina.

    Science.gov (United States)

    Macdonald, A A

    1988-01-01

    The structure of the foramen ovale from six species of Suina was studied using the scanning electron microscope. In each species, the foramen ovale, when viewed from the terminal part of the caudal vena cava had the appearance of a short tunnel. In the domestic pig (Sus scrofa), the wart hog (Phacochoerus aethiopicus) and the bush pig (Potamochoerus porcus) a fold of tissue projected from the caudal edge of the foramen ovale into the lumen of the left atrium. It constituted a large proportion of the tube, and its distal end was generally straight-edged. In some domestic pig hearts small holes were found in the fold, and single threads of tissue arose from its trailing edge. These were not found in specimens from the other pigs or from the collared peccary (Tayassu tajacu), which had a thin unfenestrated tissue fold ending in a straight edge. In both species of hippopotamidae, the hippopotamus (Hippopotamus amphibius) and the pigmy hippopotamus (Choeropsis liberiensis) the fold of tissue was tubular, with strands of tissue extending from the atrial wall to insert on the outer surface of its proximal half. This tube was orientated at an angle of approximately 90 degrees to the caudal vena cava. Its walls were unfenestrated proximally and fenestrated distally, the latter forming a network over the end of the tube. The knotted appearance of the fold after birth suggested that the strands of the network had shortened and coalesced. PMID:3377202

  5. Ground and satellite observations of auroral fragmentation into patches

    Science.gov (United States)

    Shiokawa, Kazuo; Nishi, Katsuki

    2016-07-01

    We review characteristic auroral fragmentation which is the process by which uniform aurora is broken into several fragments to form auroral patches, based on the all-sky camera observations at Tromsoe, Norway and THEMIS chain in Canada. The auroral fragmentation occurs as finger-like structures developing predominantly in meridional direction with speeds of several tens m/s and scale sizes of several tens kilometers without any shearing motion. These features suggest that pressure-driven instability in the balance between the earthward magnetic-tension force and the tailward pressure gradient force in the magnetosphere is the main driving force of the auroral fragmentation. Thus, these observations indicate that auroral fragmentation associated with pressure-driven instability is a process that creates auroral patches. Auroral fragmentation is seen from midnight to dawn local time and usually appears at the beginning of the substorm recovery phase, near the low latitude boundary of the auroral region. One example of plasma and magnetic field observations by the THEMIS satellite in the conjugate magnetosphere shows diamagnetic anti-phase variations of magnetic and plasma pressures with time scales of several to tens minutes associated with the auroral fragmentation. This observation also supports the idea of pressure-driven instability to cause the auroral fragmentation into patches.

  6. Genome-scale comparison of expanded gene families in Plasmodium ovale wallikeri and Plasmodium ovale curtisi with Plasmodium malariae and with other Plasmodium species

    KAUST Repository

    Ansari, Hifzur Rahman

    2016-07-05

    Malaria in humans is caused by six species of Plasmodium parasites, of which the nuclear genome sequences for the two Plasmodium ovale spp., P. ovale curtisi and P. ovale wallikeri, and Plasmodium malariae have not yet been analyzed. Here we present an analysis of the nuclear genome sequences of these three parasites, and describe gene family expansions therein. Plasmodium ovale curtisi and P. ovale wallikeri are genetically distinct but morphologically indistinguishable and have sympatric ranges through the tropics of Africa, Asia and Oceania. Both P. ovale spp. show expansion of the surfin variant gene family, and an amplification of the Plasmodium interspersed repeat (pir) superfamily which results in an approximately 30% increase in genome size. For comparison, we have also analyzed the draft nuclear genome of P. malariae, a malaria parasite causing mild malaria symptoms with a quartan life cycle, long-term chronic infections, and wide geographic distribution. Plasmodium malariae shows only a moderate level of expansion of pir genes, and unique expansions of a highly diverged transmembrane protein family with over 550 members and the gamete P25/27 gene family. The observed diversity in the P. ovale wallikeri and P. ovale curtisi surface antigens, combined with their phylogenetic separation, supports consideration that the two parasites be given species status.

  7. Auroral backscatter observed at HF from Ottawa

    International Nuclear Information System (INIS)

    Bistatic HF radar recordings of auroral scattering sources north of Ottawa are reported. Doppler frequency spreads over + or - 100 Hz were obtained at least 35 percent of the time. The peak of the Doppler frequency distribution was sometimes shifted from zero by as much as 50 Hz, and significant contributions often occurred at Doppler frequencies greater than 150 Hz. Signals received simultaneously on both arms of a two-arm direction-finding array were used to identify the specific elevations and bearings of the backscatter signals. A detailed study of a particular hour-long period is reported, and a large number of 'apparent' auroral backscatter sources are identified. The source regions, probably located in the F layer, were elongated mainly in the north-south direction and extended over at least 3 deg of latitude. North-south corridors were found between such sources in which echo returns were either absent or very weak. 14 references

  8. Auroral bright spot sequence near 14 MLT

    International Nuclear Information System (INIS)

    Optical observations of a dayside auroral brightening sequence, by means of all-sky TV cameras and meridian scanning photometers, have been combined with EISCAT ion drift observations within the same invariant latitude - MLT sector. The reported events, covering a 35 min interval around 14 MLT, are embedded within a longer period of similar auroral activity between 0830 (1200 MLT) and 1300 UT (1600 MLT). These observations are discussed in relation to recent models of boundary layer plasma dynamics and the associated magnetosphere-ionosphere coupling. The ionospheric events may correspond to large-scale wavelike motions of the low-latitude boundary layer. Based on this interpretation the observed spot size, speed and repetition period (∼ 10 min) give a wavelenght ∼ 900 km in the present case. The events can also be explained as ionospheric signatures of newly opened flux tubes associated with reconnection bursts at the magnetopause near 1400 MLT. 46 refs., 11 figs

  9. Experimental study of diffuse auroral precipitations

    International Nuclear Information System (INIS)

    First chapter is devoted to low energy electron precipitation in the evening sector of the auroral magnetosphere, during quiet and disturbed magnetic periods. Four subjects are studied in detail: the latitude distribution of the varied auroral forms and their relations to external magnetosphere; the time coefficients related to precipitations, the form and the dynamic of the diffuse precipitation equatorial frontier; the precipitation effect on the ionosphere concentration. The last part of the chapter shows that the plasma convection in the magnetosphere, associated to wave-particle interactions near the equatorial accounts for the principal characteristics of the evening sector diffuse electronic precipitations. The second chapter deals with subauroral precipitations of low energy ions, after the magnetospheric substorms, in the high latitude regions of the morning sector

  10. The convection electric field in auroral substorms

    DEFF Research Database (Denmark)

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    2001-01-01

    Dynamics Explorer 2 (DE 2) electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge-type auroral substorms. Thirty-one individual DE 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained...... this database enabled us to compile a model of the ionospheric convection electric field. The characteristics of the premidnight convection reversal show a pronounced local time dependency. Far west of the surge it is a fairly well defined point reversal or convection shear. Approaching the surge and within...... the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields. Therefore we adopt the term Harang region rather than the Harang discontinuity for the premidnight convection reversal. A relatively narrow convection...

  11. A numerical simulation of auroral ionospheric electrodynamics

    Science.gov (United States)

    Mallinckrodt, A. J.

    1985-01-01

    A computer simulation of auroral ionospheric electrodynamics in the altitude range 80 to 250 km has been developed. The routine will either simulate typical electron precipitation profiles or accept observed data. Using a model background ionosphere, ion production rates are calculated from which equilibrium electron densities and the Hall and Pedersen conductivities may be determined. With the specification of suitable boundary conditions, the entire three-dimensional current system and electric field may be calculated within the simulation region. The results of the application of the routine to a typical inverted-V precipitation profile are demonstrated. The routine is used to explore the observed anticorrelation between electric field magnitude and peak energy in the precipitating electron spectrum of an auroral arc.

  12. Sophus Peter Tromholt: an outstanding pioneer in auroral research

    OpenAIRE

    Moss, K.; P. Stauning

    2012-01-01

    The Danish school teacher Sophus Peter Tromholt (1851–1896) was self-taught in physics, astronomy, and auroral sciences. Still, he was one of the brightest auroral researchers of the 19th century. He was the first scientist ever to organize and analyse correlated auroral observations over a wide area (entire Scandinavia) moving away from incomplete localized observations. Tromholt documented the relation between auroras and sunspots and demonstrated the daily, seasonal and solar cyc...

  13. Cluster in situ studies of the auroral acceleration region

    OpenAIRE

    Li, Bin

    2014-01-01

    This thesis addresses a central topic in auroral physics, namely particle accelerationproducing intense aurora as well as energetic plasma outflow. Cluster satellitemeasurements of electric and magnetic fields, electrons and ions, collected across auroralfield lines, are used to study various aspects of the quasi-static auroral accelerationregion (AAR), its relation to the auroral density cavity, and the relative role of quasistaticand Alfvénic acceleration for producing aurora.The accelerati...

  14. Propagation of auroral hiss at high altitudes

    Czech Academy of Sciences Publication Activity Database

    Santolík, Ondřej; Gurnett, D. A.

    2002-01-01

    Roč. 29, č. 10 (2002), s. 119-1-119-4, doi: 10.1029/2001GL013666. ISSN 0094-8276 R&D Projects: GA ČR GA205/01/1064 Grant ostatní: NASA(US) NAG5-7943 Institutional research plan: CEZ:AV0Z3042911; CEZ:MSM 113200004 Keywords : auroral hiss * electron beams * wave measurement Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.150, year: 2002

  15. Encerramento do foramen oval patente : risco ou mais-valia?

    OpenAIRE

    Carvalho, Rute Carlos Vieira de

    2012-01-01

    Introdução: O Foramen Oval Patente é uma anomalia congénita com elevada prevalência na população geral (≈25%). Na maioria dos casos é um achado incidental sem necessidade de tratamento. Porém, esta patologia foi associada a inúmeras condições patológicas major, nomeadamente, embolia paradoxal, enxaqueca, síndrome de descompressão em mergulhadores e síndrome de platipneia-ortodoxa. Esta anomalia é mais prevalente em pacientes com história de acidente vascular cerebral de idade inferior a 50 an...

  16. An interhemispheric comparison of GPS phase scintillation with auroral emission observed at the South Pole and from the DMSP satellite

    Directory of Open Access Journals (Sweden)

    Paul Prikryl

    2013-06-01

    Full Text Available The global positioning system (GPS phase scintillation caused by high-latitude ionospheric irregularities during an intense high-speed stream (HSS of the solar wind from April 29 to May 5, 2011, was observed using arrays of GPS ionospheric scintillation and total electron content monitors in the Arctic and Antarctica. The one-minute phase-scintillation index derived from the data sampled at 50 Hz was complemented by a proxy index (delta phase rate obtained from 1-Hz GPS data. The scintillation occurrence coincided with the aurora borealis and aurora australis observed by an all-sky imager at the South Pole, and by special sensor ultraviolet scanning imagers on board satellites of the Defense Meteorological Satellites Program. The South Pole (SP station is approximately conjugate with two Canadian High Arctic Ionospheric Network stations on Baffin Island, Canada, which provided the opportunity to study magnetic conjugacy of scintillation with support of riometers and magnetometers. The GPS ionospheric pierce points were mapped at their actual or conjugate locations, along with the auroral emission over the South Pole, assuming an altitude of 120 km. As the aurora brightened and/or drifted across the field of view of the all-sky imager, sequences of scintillation events were observed that indicated conjugate auroras as a locator of simultaneous or delayed bipolar scintillation events. In spite of the greater scintillation intensity in the auroral oval, where phase scintillation sometimes exceeded 1 radian during the auroral break-up and substorms, the percentage occurrence of moderate scintillation was highest in the cusp. Interhemispheric comparisons of bipolar scintillation maps show that the scintillation occurrence is significantly higher in the southern cusp and polar cap.

  17. Thermal ion measurements on board Interball Auroral Probe by the Hyperboloid experiment

    Directory of Open Access Journals (Sweden)

    N. Dubouloz

    identified associated to the polar edge of the auroral oval. Detailed distribution functions of injected magnetosheath ions and ouflowing cleft fountain ions are measured down to a few eVs in the dayside.

    Key words. Ionosphere (auroral ionosphere; particle acceleration; ionosphere-magnetosphere interactions

     

  18. Turbulence-double-layer synergetic auroral electron acceleration

    International Nuclear Information System (INIS)

    In this letter we present a theoretical discussion on the problem of the auroral electron acceleration that supports the conjecture of wave-particle interaction (turbulence) assisting the auroral electron acceleration due to a dc magnetic field aligned electric field, created by a double layer, working as to enhance the electron flux

  19. An Anatomical Study on the Foramen Ovale and the Foramen Spinosum

    OpenAIRE

    Khairnar, Karan Bhagwawan; Bhusari, Prashant Amanrao

    2013-01-01

    Introduction: An anatomical study was undertaken to note the shape of the foramen ovale(FO), foramen spinosum (FS) & presence or absence of canalis innominatus. FO is present in the posterior part of the greater wing of sphenoid. FS is located posterolareral to foramen ovale.

  20. Two theories of auroral electron acceleration

    International Nuclear Information System (INIS)

    Two theories of auroral electron acceleration are discussed. The first is the currently widely held view that the acceleration is an ordered process in a quasi-static electric field. It is suggested that, although there are many factors seeming to support this theory, the major qualifications and uncertainties that have been identified combine to cast serious doubt over its validity. The second is a relatively new interpretation in terms of stochastic acceleration in turbulent electric fields. This second theory, which appears to account readily for most known features of the electron distribution function, is considered to provide a more promising approach to this central question in magnetospheric plasma physics. (author)

  1. EXPERIMENTS ON HYDRODYNAMIC INTERACTION BETWEEN 3-D OVAL AND WALL

    Institute of Scientific and Technical Information of China (English)

    SUN Ke; SHENG Qi-hu; ZHANG Liang; LI Feng-lai

    2007-01-01

    The boundary hydrodynamic interaction of a 3-D oval body was experimentally surveyed for different cases. The regression method was employed to find the experimental formulae of hydrodynamic coefficients relating to the attack angle, clearance to wall, and moving speed. The mechanism of interaction was discussed. The experimental results show that there exists a lifting effect, similar to wings in flow. The lifting effect is remarkable. The boundary hydrodynamic interaction of the small aspect ratio model is almost linearly dependent on the attack angle, but the effect of the moving speed of the body on the hydrodynamic coefficients is very small. The effect of clearance is related to the geometric shape. The boundary hydrodynamic interaction always enhances the lifting effect if the clearance is small.

  2. Determination of the Stable Slope Configuration of Oval-Shaped Furrow Pits

    Institute of Scientific and Technical Information of China (English)

    ZHU Nai-long; ZHANG Shi-xiong

    2004-01-01

    The space effects of oval-shaped furrow pit slopes were analyzed by the elastic mechanics principle. The interaction of limit equilibrium slope angle, friction coefficient, cohesion and horizontal radius of oval-shaped furrow pits has been derived. The oval trumpet-like rock mass is homogeneous and elastic while only loadedby its dead weight. The interaction indicates that the deeper an oval-shaped furrow pit is excavated, the greater thelimit equilibrium slope angle. Both the theory base for reducing stripping waste rock in an oval- shaped furrow pitand the basic way to determine the configuration of a stable slope were developed from the mentioned interaction.The theory includes the preceding principles of stability analysis of slopes. Compared with the configuration deter-mined by traditional theory of slope stability, a great quantity of stripping waste rock can be reduced by that deter-mined in this paper under stable conditions.

  3. Laboratory study of auroral cyclotron emission processes

    Science.gov (United States)

    Ronald, Kevin

    2007-11-01

    Electrons encounter an increasing magnetic field and increase in pitch angle as they descend towards the auroral ionosphere, according to the conservation of the magnetic moment. This process results in a horseshoe shaped distribution function in electron velocity space which has been observed by satellites [1]. Research has shown this distribution to be unstable to a cyclotron maser instability [2] and the emitted Auroral Kilometric Radiation is observed to be polarised in the extraordinary mode. Experimental results are presented based on an electron beam of energy 75keV having a cyclotron frequency of 4.45GHz, compressed using magnet coils to mimic the naturally occurring phenomenon. The emitted radiation spectrum was observed to be close to the cyclotron frequency. Electron transport measurements confirmed that the horseshoe distribution function was obtained. Measurements of the antenna pattern radiated from the output window demonstrated the radiation to be polarised and propagating perpendicular to the static magnetic field. The radiation generation efficiency was estimated to be 2% in close agreement to the numerical predictions of the 2D PiC code KARAT. The efficiency was also comparable with estimates of the astrophysical phenomenon. [1] R. J. Strangeway et al, Geophys. Rev. Lett., 25, 1998, pp. 2065-2068 [2] I Vorgul et al, Physics of Plasmas, 12, 2005, pp. 1-8

  4. Carl Størmer Auroral Pioneer

    CERN Document Server

    Egeland, Alv

    2013-01-01

    This biography summarizes the seminal contributions to auroral and space science of Carl Størmer (1874 - 1957). He was the first to develop precise photographic methods to calculate heights and morphologies of diverse auroral forms during four solar cycles. Størmer independently devised numerical techniques to determine the trajectories of high-energy charged particles allowed and forbidden in the Earth’s magnetic field. His theoretical analyses explained cosmic ray access to the upper atmosphere, 20 years before they were identified by other scientists. Størmer’s crowning achievement, “The Polar Aurora,” published when he was 81 years old, stands to this day as a regularly cited guide in graduate-level courses on space physics.   The authors present the life of this prodigious scientist in relation to the cultural life of early 20th century in Norway and to the development of the space sciences in the post-Sputnik era.

  5. ISIS-II Scanning Auroral Photometer.

    Science.gov (United States)

    Anger, C D; Fancott, T; McNally, J; Kerr, H S

    1973-08-01

    The ISIS-II dual wavelength scanning auroral photometer is designed to map the distribution of auroral emissions at 5577 A and 3914 A over the portion of the dark earth visible to the spacecraft. A combination of internal electronic scanning and the natural orbital and rotational motions of the spacecraft causes a dual wavelength photometer to be scanned systematically across the earth. The data will be reproduced directly in the form of separate pictures representing emissions at each wavelength, which will be used to study the large-scale distribution and morphology of auroras, to study the ratio of 3914-A and 5577-A emissions thought to depend upon the energies of exciting particles), and to compare with results from other instruments on board the spacecraft and on the ground. The Red Line Photometer experiment on the same spacecraft is described in an accompanying paper by Shepherd et al. [Appl. Opt. 12, 1767 (1973)]. The instrument can be thought of as the photometric equivalent of an all-sky color camera which will view the aurora from above instead of below and with a much wider vantage point unobstructed by cloud and haze. In one satellite pass, the instrument will be capable of surveying (in one hemisphere) the entire polar region in which auroras normally occur. PMID:20125605

  6. Cluster in the Auroral Acceleration Region

    Science.gov (United States)

    Pickett, Jolene S.; Fazakerley, Andrew N.; Marklund, Gorun; Dandouras, Iannis; Christopher, Ivar W.; Kistler, Lynn; Lucek, Elizabeth; Masson, Arnaud; Taylor, Matthew G.; Mutel, Robert L.; Santolik, Ondrej; Bell, Timothy F.; Fung, Shing; Pottelette, Raymond; Hanasz, Jan; Schreiber, Roman; Hull, Arthur J.

    2010-01-01

    Due to a fortuitous evolution of the Cluster orbit, the Cluster spacecraft penetrated for the first time in its mission the heart of Earth's auroral acceleration region (AAR) in December 2009 and January 2010. During this time a special AAR campaign was carried out by the various Cluster instrument teams with special support from ESA and NASA facilities. We present some of the first multi-spacecraft observations of the waves, particles and fields made during that campaign. The Cluster spacecraft configuration during these AAR passages was such that it allowed us to explore the differences in the signatures of waves, particles, and fields on the various spacecraft in ways not possible with single spacecraft. For example, one spacecraft was more poleward than the other three (C2), one was at higher altitude (C1), and one of them (0) followed another (C4) through the AAR on approximately the same track but delayed by three minutes. Their separations were generally on the order of a few thousand km or less and occasionally two of them were lying along the same magnetic field line. We will show some of the first analyses of the data obtained during the AAR campaign, where upward and downward current regions, and the waves specifically associated with those regions, as well as the auroral cavities, were observed similarly and differently on the various spacecraft, helping us to explore the spatial, as well as the temporal, aspects of processes occurring in the AAR.

  7. Preliminary results from Project Waterhole - an auroral modification experiment

    International Nuclear Information System (INIS)

    A sounding rocket carrying 100 kg of high explosives and plasma diagnostic instrumentation was launched from Churchill Research Ranch on 6 April 1980 over a premidnight auroral arc. The object of the experiment was to produce an ionospheric hole or plasma density depletion near 300 km altitude on field lines connected to an auroral arc. The plasma depletion is produced when the explosive by-products (mostly water) charge-exchange with the ambient O+ ions and then rapidly recombine. It was speculated that the presence of the 'hole' would interfere with the field-aligned current systems associated with the arc and would in turn perturb the auroral source mechanism. The release occurred about 10 km poleward of the auroral arc field lines. As expected, a large ionospheric hole was detected by the rocket-borne plasma sensors. Within a few seconds following the release, (a) the energetic electron precipitation observed in the hole dropped to background levels, (b) the luminosity of the auroral arc observed by a ground-based auroral scanning photometer decreased by a factor of two, and (c) the ionospheric E region density below the hole decayed at a rate consistent with a sudden reduction in particle precipitation. The simultaneous onset of these gross changes in electron precipitation coincident with the release strongly suggests a cause and effect relationship and demonstrates the intimate relationship that exists between the state of the ionospheric plasma and the auroral acceleration mechanism

  8. 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

    The magnetospheric electron precipitation along the upward field-aligned currents without the potential difference causes diffuse aurora, and the magnetospheric electrons accelerated by a field-aligned potential difference cause the intense and bright type of aurora, namely discrete aurora. In this study, we are trying to find out when and where the aurora can be caused with or without electron acceleration. We statistically investigate electron density, temperature, thermal current, and conductivity in the plasma sheet using the data from the electrostatic analyzer (ESA) onboard the THEMIS-D satellite launched in 2007. According to Knight (Planet. Space Sci., 1973) and Lyons (JGR, 1980), the thermal current, jth(∝ nT^(1/2) where n is electron density and T is electron temperature in the plasma sheet), represents the upper limit to field aligned current that can be carried by magnetospheric electrons without field-aligned potential difference. The conductivity, K(∝ nT^(-1/2)), represents the efficiency of the upward field-aligned current (j) that the field-aligned potential difference (V) can produce (j=KV). Therefore, estimating jth and K in the plasma sheet is important in understanding the ability of plasma sheet electrons to carry the field-aligned current which is driven by various magnetospheric processes such as flow shear and azimuthal pressure gradient. Similar study was done by Shiokawa et al. (2000) based on the auroral electron data obtained by the DMSP satellites above the auroral oval and the AMPTE/IRM satellite in the near Earth plasma sheet at 10-18 Re on February-June 1985 and March-June 1986 during the solar minimum. The purpose of our study is to examine auroral electrons with pitch angle information inside 12 Re where Shiokawa et al. (2000) did not investigate well. For preliminary result, we found that in the dawn side inner magnetosphere (source of the region 2 current), electrons can make sufficient thermal current without field

  9. ISOLATION OF Rickettsia bellii FROM Amblyomma ovale AND Amblyomma incisum TICKS FROM SOUTHERN BRAZIL

    Directory of Open Access Journals (Sweden)

    Richard Pacheco

    2008-08-01

    Full Text Available Objective. To isolate and characterize rickettsiae from the ticks Amblyomma ovale and Amblyomma incisum collected in the state of São Paulo. Materials and methods. Adult, free-living A. ovale and A. incisum were collected in an Atlantic rainforest area in the state of São Paulo, Brazil. Each tick was tested using the hemolymph assay; samples from positive ticks were placed in shell vials in order to isolate rickettsiae and subsequently grown in Vero cells. Amplification of three rickettsial genes (gltA, htrA and ompA was attempted using polymerase chain reaction (PCR for each isolate obtained. Amplicons were subsequently sequenced. Results. A total of 388 A. incisum and 50 A. ovale were collected. Only one A. incisum and one A. ovale were hemolymph-test positive. Rickettsiae were successfully isolated from these ticks; however establishment in Vero cell culture was successful only for the isolate from A. ovale. Bacterial contamination in the first cell passage of the A. incisum isolate precluded successful isolation of the organism. PCR products were obtained with the gltA and htrA primers for the two isolates, but no product was obtained with the ompA primers. By BLAST analysis, partial gltA and htrA sequences of isolates from A. ovale and A. incisum were similar to the corresponding sequences of R. bellii. Conclusions. This is the first report of R. bellii infecting A. incisum and the first successful isolation from A. ovale.

  10. Immunohistochemical study of hepatic oval cells in human chronic viral hepatitis

    Institute of Scientific and Technical Information of China (English)

    Xiong Ma; De Kai Qiu; Yan Shen Peng

    2001-01-01

    AIM To detect immunohistochemically the presence of oval cells in chronic viral hepatitis with antibody against c-kit.METHODS We detected oval cells in paraffin-embedded liver sections of 3 normal controls and 26 liver samples from patients with chronic viral hepatitis, using immunohistochemistry with antibodies against c-kit, π-class glutathione Stransferase ( Tr-GST ) and cytokeratins 19(CK19).RESULTS Oval cells were not observed in normal livers. In chronic viral hepatitis, hepatic oval cells were located predominantly in the periportal . region and fibrosis septa,characterized by an ovoid nucleus, small size,and scant cytoplasm. Antibody against stem cell factor receptor, c-kit, had higher sensitivity and specificity than π-GST and CK19. About 50% -70% of c-kit positive oval cells were stained positively for either π-GST or CK19.CONCLUSION Oval cells are frequently detected in human livers with chronic viral hepatitis, suggesting that oval cell proliferation is associated with the liver regeneration in this condition.

  11. Hepatic non-parenchymal cells and extracellular matrix participate in oval cell-mediated liver regeneration

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Xiao-Ping Chen; Wan-Guang Zhang; Feng Zhang; Shuai Xiang; Han-Hua Dong; Lei Zhang

    2009-01-01

    AIM: To elucidate the interaction between nonparenchymal cells, extracellular matrix and oval cells during the restituting process of liver injury induced by partial hepatectomy (PH). METHODS: We examined the localization of oval cells, non-parenchymal cells, and the extracellular matrix components using immunohistochemical and double immunofluorescent analysis during the proliferation and differentiation of oval cells in N-2-acetylaminofluorene (2-AAF)/PH rat model. RESULTS: By day 2 after PH, small oval cells began to proliferate around the portal area. Most of stellate cells and laminin were present along the hepatic sinusoids in the periportal area. Kupffer cells and fibronectin markedly increased in the whole hepatic lobule. From day 4 to 9, oval cells spread further into hepatic parenchyma, closely associated with stellate cells, fibronectin and laminin. Kupffer cells admixed with oval cells by day 6 and then decreased in the periportal zone. From day 12 to 15, most of hepatic stellate cells (HSCs), laminin and fibronectin located around the small hepatocyte nodus, and minority of them appeared in the nodus. Kupffer cells were mainly limited in the pericentral sinusoids. After day 18, the normal liver lobule structures began to recover.CONCLUSION: Local hepatic microenvironment may participate in the oval cell-mediated liver regeneration through the cell-cell and cell-matrix interactions.

  12. Limited Polymorphism of the Kelch Propeller Domain in Plasmodium malariae and P. ovale Isolates from Thailand.

    Science.gov (United States)

    Nakeesathit, Supatchara; Saralamba, Naowarat; Pukrittayakamee, Sasithon; Dondorp, Arjen; Nosten, Francois; White, Nicholas J; Imwong, Mallika

    2016-07-01

    Artemisinin resistance in Plasmodium falciparum, the agent of severe malaria, is currently a major obstacle to malaria control in Southeast Asia. A gene named "kelch13" has been associated with artemisinin resistance in P. falciparum The orthologue of the kelch gene in P. vivax was identified and a small number of mutations were found in previous studies. The kelch orthologues in the other two human malaria parasites, P. malariae and P. ovale, have not yet been studied. Therefore, in this study, the orthologous kelch genes of P. malariae, P. ovale wallikeri, and P. ovale curtisi were isolated and analyzed for the first time. The homologies of the kelch genes of P. malariae and P. ovale were 84.8% and 82.7%, respectively, compared to the gene in P. falciparum kelch polymorphisms were studied in 13 P. malariae and 5 P. ovale isolates from Thailand. There were 2 nonsynonymous mutations found in these samples. One mutation was P533L, which was found in 1 of 13 P. malariae isolates, and the other was K137R, found in 1 isolate of P. ovale wallikeri (n = 4). This result needs to be considered in the context of widespread artemisinin used within the region; their functional consequences for artemisinin sensitivity in P. malariae and P. ovale will need to be elucidated. PMID:27114275

  13. Current Closure in the Auroral Ionosphere: Results from the Auroral Current and Electrodynamics Structure Rocket Mission

    Science.gov (United States)

    Kaeppler, S. R.; Kletzing, C. A.; Bounds, S. R.; Gjerloev, J. W.; Anderson, B. J.; Korth, H.; LaBelle, J. W.; Dombrowski, M. P.; Lessard, M.; Pfaff, R. F.; Rowland D. E.; Jones, S.; Heinselman, C. J.

    2012-01-01

    The Auroral Current and Electrodynamics Structure (ACES) mission consisted of two sounding rockets launched nearly simultaneously from Poker Flat Research Range, AK on January 29, 2009 into a dynamic multiple-arc aurora. The ACES rocket mission was designed to observe electrodynamic and plasma parameters above and within the current closure region of the auroral ionosphere. Two well instrumented payloads were flown along very similar magnetic field footprints, at different altitudes, with small temporal separation between both payloads. The higher altitude payload (apogee 360 km), obtained in-situ measurements of electrodynamic and plasma parameters above the current closure region to determine the input signature. The low altitude payload (apogee 130 km), made similar observations within the current closure region. Results are presented comparing observations of the electric fields, magnetic components, and the differential electron energy flux at magnetic footpoints common to both payloads. In situ data is compared to the ground based all-sky imager data, which presents the evolution of the auroral event as the payloads traversed through magnetically similar regions. Current measurements derived from the magnetometers on the high altitude payload observed upward and downward field-aligned currents. The effect of collisions with the neutral atmosphere is investigated to determine if it is a significant mechanism to explain discrepancies in the low energy electron flux. The high altitude payload also observed time-dispersed arrivals in the electron flux and perturbations in the electric and magnetic field components, which are indicative of Alfven waves.

  14. Patent foramen ovale: indications for closure and techniques.

    Science.gov (United States)

    Taramasso, Maurizio; Nietlispach, Fabian; Maisano, Francesco; Meier, Bernhard

    2016-05-17

    Non-surgical closure of the patent foramen ovale (PFO) has been possible for 40 years and proved safe in probably a million cases performed worldwide. Nonetheless, indications are still restricted as only a few are supported by randomised data. Paradoxical embolism through a PFO causes stroke, myocardial infarction, and visceral or peripheral ischaemia. The PFO is a likely mediator of migraine, diving or high altitude sickness, dyspnoea, and sleep apnoea problems. As untoward effects of a PFO are rare and spaced widely timewise, large cohorts and long follow-ups are required to prove unequivocally that PFO closure is bene-ficial and appropriate in comparison to no treatment or medical therapy. The most compelling respective randomised data have been gathered so far in the realm of secondary prevention of cerebral attacks and migraine. Invariably they showed a numerical advantage of PFO closure with significant difference in sub-analyses. Evidence-based medicine carries a danger of underutilising valuable therapies while accumulating further data. PFO closure is an example. Its documented innocuousness invites a more proactive reflection in upcoming guidelines. At worst, PFO closure may not convey the projected amount of benefit. This even opens the door for primary prevention in some PFOs with high-risk characteristics. PMID:27174117

  15. Effectiveness of percutaneous closure of patent foramen ovale for hypoxemia.

    Science.gov (United States)

    Fenster, Brett E; Nguyen, Bryant H; Buckner, J Kern; Freeman, Andrew M; Carroll, John D

    2013-10-15

    The aim of this study was to evaluate the ability of percutaneous patent foramen ovale (PFO) closure to improve systemic hypoxemia. Although PFO-mediated right-to-left shunt (RTLS) is associated with hypoxemia, the ability of percutaneous closure to ameliorate hypoxemia is unknown. Between 2004 and 2009, 97 patients who underwent PFO closure for systemic hypoxemia and dyspnea that was disproportionate to underlying lung disease were included for evaluation. All patients exhibited PFO-mediated RTLS as determined by agitated saline echocardiography. Procedural success was defined as implantation of a device without major complications and mild or no residual shunt at 6 months. Clinical success was defined as a composite of an improvement in New York Heart Association (NYHA) functional class, reduction of dyspnea symptoms, or decreased oxygen requirement. Procedural success was achieved in 96 of 97 (99%), and clinical success was achieved in 68 of 97 (70%). The presence of any moderate or severe interatrial shunt by agitated saline study (odds ratio [OR] = 4.7; p RTLS, NYHA functional class, and oxygen requirement. PMID:23871675

  16. RFP for the Auroral Multiscale Midex (AMM) Mission star tracker

    DEFF Research Database (Denmark)

    Riis, Troels; Betto, Maurizio; Jørgensen, John Leif;

    1999-01-01

    This document is in response to the John Hopkins University - Applied Physics Laboratory RFP for the Auroral Multiscale Midex Mission star tracker.It describes the functionality, the requirements and the performance of the ASC Star Tracker.......This document is in response to the John Hopkins University - Applied Physics Laboratory RFP for the Auroral Multiscale Midex Mission star tracker.It describes the functionality, the requirements and the performance of the ASC Star Tracker....

  17. Ionospheric heating, upwelling, and depletions in auroral current systems

    Science.gov (United States)

    Zettergren, M. D.; Semeter, J. L.

    2010-12-01

    This research investigates aspects of ionospheric dynamics relevant to magnetosphere-ionosphere coupling in auroral arc current systems. Auroral electric fields and particle precipitation deposit energy in the ionosphere, often resulting in enhanced ion or electron temperatures. This heating has a wide variety of consequences for the ionosphere. High ion temperatures alter chemical balance in the lower F-region, resulting in conversion to a molecular ion plasma, faster recombination, and plasma depletions. Pressure enhancements resulting from both ion and electron heating are capable of generating intense ion upflows. Ion upflow and depletion processes redistribute and structure the auroral plasma in ways that are likely of consequence to wave coupling of the magnetosphere and ionosphere. These implications are examined through the use of a fluid-kinetic model of the auroral ionosphere and new incoherent scatter radar data analysis techniques. Results indicate that enhanced recombination of molecular ions in auroral downward current regions may work in concert with well-known electrodynamic depletion processes, in the F-region ionosphere. Furthermore, ionospheric upflows in auroral upward and downward current regions may be quite different in terms of intensity and types of upflowing ions.

  18. Numerical Simulation of the Turbulent Flow around an Oval-Sail

    Directory of Open Access Journals (Sweden)

    Ouahiba Guerri

    2016-01-01

    Full Text Available This paper presents numerical study of an oval-sail, a bluff-body equipped with a grid all along the span. Suction based flow control is applied to this body that is developed for wind assisted ship propulsion. First, a choice of numerical turbulence model is discussed through results of an oval-sail without suction. Three turbulence models are applied: the Ri j SSG, the Ri j EBRSM and the v2 f model. Then, computations are performed for the oval-sail fitted with suction grid. These last simu- lations are carried out with the low-Reynolds-number Ri j EBRSM turbulence model. The influence of the grid geometry on the oval-sail aerodynamic performances is highlighted. All simulations are carried out for the sail set at zero incidence. The Reynolds number based on the free stream velocity and the profile chord is Re = 5105. Results are compared to available experimental data.

  19. The drawing of the dome of Borromini? San Carlino alle Quattro Fontane: canonic oval?

    Directory of Open Access Journals (Sweden)

    Marco Canciani

    2015-07-01

    Full Text Available  The oval that characterizes the dome of the church of San Carlino, designed by Francesco Castelli, called Borromini, is a subject that has always attracted the interest of many scholars. Many design drawings describe a geometric trace of a polycentric curve, or an oval, with a complex plot of lines, some needed to geometrical construction and correspondence with architectural drawing, others of uncertain interpretation. This study aims to investigate the actual role which has the oval shape in the project of San Carlino by comparing the design drawings and the detailed study of the model derived from the survey. In particular this study analyze the sections of the elements where the shape of the oval is present:the tiburium, the coffered dome, the lantern.

  20. Comparison of Bacterial Leakage between 3 Different Root Canal Obturation Techniques in Oval Shaped Canals

    OpenAIRE

    Eshagh-ali Saberi; Shahram Shahraki; Sediqe Ebrahimipour; Anousheh Rashed Mohassel; Narjes Akbari; Majid Rezaei

    2014-01-01

    Introduction: The purpose of this study was to evaluate the sealing ability of 3 obturation techniques in oval-shaped canals by bacterial leakage assessment. Methods: Sixty mandibular incisors with oval canals were selected after providing buccolingual and mesiodistal radiographs. The teeth were sectioned at a 10 mm distance from the apex. After instrumentation, the teeth were divided into 3 groups and the canals in the three groups were obturated with lateral condensation (G1), warm vertical...

  1. On the lifetime and extent of an auroral westward flow channel (AWFC observed during a magnetospheric substorm

    Directory of Open Access Journals (Sweden)

    M. L. Parkinson

    Full Text Available A -190-nT negative bay in the geomagnetic X component measured at Macquarie Island ( -65° L showed that an ionospheric substorm occurred during 09:58 to 11:10 UT on 27 February 2000. Signatures of an auroral westward flow channel (AWFC were observed nearly simultaneously in the backscatter power, LOS Doppler velocity, and Doppler spectral width measured using the Tasman International Geospace Environment Radar (TIGER, a Southern Hemisphere HF SuperDARN radar. Many of the characteristics of the AWFC were similar to those occurring during a polarisation jet (PJ, or subauroral ion drift (SAID event, and suggest that it may have been a pre-cursor to a fully developed, intense westward flow channel satisfying all of the criteria defining a PJ/SAID. A beam-swinging analysis showed that the westward drifts (poleward electric field associated with the flow channel were very structured in time and space, but the smoothed velocities grew to ~ 800 ms-1 (47 mVm-1 during the 22-min substorm onset interval 09:56 to 10:18 UT. Maximum west-ward drifts of >1.3 km s-1 (>77 mVm-1 occurred during a ~ 5-min velocity spike, peaking at 10:40 UT during the expansion phase. The drifts decayed rapidly to ~ 300 ms-1 (18 mVm-1 during the 6-min recovery phase interval, 11:04 to 11:10 UT. Overall, the AWFC had a lifetime of 74 min, and was located near -65° L in the evening sector west of the Harang discontinuity. The large westward drifts were confined to a geographic zonal channel of longitudinal ex-tent >20° (>1.3 h magnetic local time, and latitudinal width ~2° L. Using a half-width of ~ 100 km in latitude, the peak electric potential was >7.7 kV. However, a transient velocity of >3.1 km s-1 with potential >18.4 kV was observed further poleward at the end of the recovery phase. Auroral oval boundaries determined

  2. Establishment of a porcine model of patent foramen ovale

    International Nuclear Information System (INIS)

    Objective: To investigate the feasibility of developing an animal model of patent foramen ovale (PFO) in piglets by percutaneous atrial septal puncture and balloon dilation. Methods: A standardized percutaneous atrial trans-septal puncture and balloon dilation was conducted in eleven healthy piglets under general anesthesia. A Rups-100 system inserted through a femoral vein was used for the trans-septal puncture, and subsequent balloon dilatation was performed at the puncture site to imitate a PFO. Euthanasia and autopsy were performed on day-1 in 1 piglet (early autopsy), and on day-21 in the remaining 10 piglets (late autopsy). Results: Artificial PFO was successfully created in all piglets and verified by fluoroscopy. No major technical difficulty or complication was encountered except in one which developed mild hemopericardium. In the piglet which had early autopsy, the artificial foramen was measured 0.8 cm x 0.7 cm in cross-section and aggregates of erythrocytes were revealed over its rim under light microscopy. In the late autopsy group (n=10), 7 piglets had the created foramens healed and sealed off; while the other 3 showed relatively small residual lumens measuring 0.1 cm x 0.2 cm, 0.2 cm x 0.2 cm and 0.1 cm x 0.3 cm in cross-section respectively. Histological examination of specimens from the late autopsy group showed variable neointima hyperplasia, loss of neointima, infiltration of lymphocytes, focal hydropic degeneration of cardiac muscle, and focal fibrosis of interstitium at the immediate vicinity of regardless of the course of healing. Conclusion: Artificial creation of PFO in piglets is feasible by percutaneous atrial septal puncture and balloon dilation. This protocol may serve as a research model for PFO-related stroke in human. (authors)

  3. Observations of magnetic field dipolarization during auroral substorm onset

    Science.gov (United States)

    Frank, L. A.; Paterson, W. R.; Sigwarth, J. B.; Kokubun, S.

    2000-07-01

    The dynamical behavior of plasmas and magnetic fields in the vicinity of the equatorial crossing of magnetic field lines threading the onset auroral arc is examined for two substorms on November 26, 1997. The locations of the initial brightenings of the auroral arcs were determined with the cameras for visible and far-ultraviolet wavelengths on board the Polar spacecraft. The equatorial positions of the field lines were in the range of radial distances of 8-12RE as computed with models of Earth's global magnetic field. The radial distance of the Geotail spacecraft was 14 RE at a position in the premidnight sector that was 2RE below the current sheet. This spacecraft was embedded in a low-β plasma that was located adjacent to the central hot plasma sheet. For the first substorm, with onset at 1310 UT, no substantial effect was observed in the plasmas and magnetic fields, although the Geotail spacecraft was located only about 2 hours in magnetic local time from the field lines threading the onset auroral arc. For the second substorm onset, at 1354 UT, the spacecraft was positioned within tens of minutes in local time of the position of the magnetic field lines threading the onset auroral arc. This fortuitous spacecraft position in the relatively quiescent plasma and magnetic fields adjacent to the central plasma sheet and within several Earth radii of the position of the onset mechanism allowed determination of the beginning time of the dipolarization of the magnetic fields. This time was simultaneous with the onset brightening of the auroral arc within the approximately 1-min time resolution of the auroral images. The simultaneity of the initial brightening of the auroral arc and of the initiation of the dipolarization of the magnetic field, presumably due to diversion of current from the equatorial current sheet to the ionosphere, provides an important guideline for global dynamical MHD models of Earth's magnetosphere.

  4. Etude des émissions radio aurorales de Saturne, modélisation et aurores UV

    Science.gov (United States)

    Lamy, Laurent

    2008-09-01

    Cette thèse porte sur l'étude du rayonnement radio auroral kilométrique de Saturne (SKR pour Saturn Kilometric Radiation) observé de façon quasi-continue par les antennes radio de la sonde Cassini depuis son entrée en orbite autour de Saturne en juillet 2004. Comme les rayonnements radio auroraux des autres planètes magnétisées, le SKR est généré sur des lignes de champ magnétique de haute latitude prés des pôles magnétiques. Tirant parti de plusieurs années d'observations, les propriétés macroscopiques du SKR (spectre, polarisation, conjuguaison des sources de chaque hémisphère, mode d'émission) sont déduites par une analyse statistique. Elles montrent en particulier que les caractéristiques de l'émission dépendent fortement de la position de l'observateur. Ceci est une conséquence directe de l'anisotropie du SKR qui engendre de forts effets de visibilité, visibles dans les cartes d'intensité temps-fréquence (arcs, régions d'invisibilité de l'émission). La simulation de ces effets de visibilité apporte de nouvelles contraintes sur les propriétés microscopiques des sources (énergie et distribution des électrons auroraux). Le SKR est connu pour être modulé à une période variable. Une analyse de la variation de cette période radio sur plusieurs années révèle des oscillations à court terme de l'ordre de 20-30 jours dont l'origine est attribuée à la variation de la vitesse caractéristique du vent solaire au niveau de Saturne. Une étude parallèle du rayonnement auroral kilométrique terrestre (AKR), observé lors du survol de la Terre par Cassini en août 1999, met en évidence la découverte d'une modulation diurne semblable à celle du SKR. Enfin, la technique de goniopolarimétrie permet de faire de l'imagerie radio des sources du SKR. L'étude de leur distribution moyenne montre pour la première fois l'existence d'un ovale radio. La comparaison des images des sources du SKR avec celles des ovales auroraux (observ

  5. Stochastic modeling of the auroral electrojet index

    Science.gov (United States)

    Anh, V. V.; Yong, J. M.; Yu, Z. G.

    2008-10-01

    Substorms are often identified by bursts of activities in the magnetosphere-ionosphere system characterized by the auroral electrojet (AE) index. The highly complex nature of substorm-related bursts suggests that a stochastic approach would be needed. Stochastic models including fractional Brownian motion, linear fractional stable motion, Fokker-Planck equation and Itô-type stochastic differential equation have been suggested to model the AE index. This paper provides a stochastic model for the AE in the form of fractional stochastic differential equation. The long memory of the AE time series is represented by a fractional derivative, while its bursty behavior is modeled by a Lévy noise with inverse Gaussian marginal distribution. The equation has the form of the classical Stokes-Boussinesq-Basset equation of motion for a spherical particle in a fluid with retarded viscosity. Parameter estimation and approximation schemes are detailed for the simulation of the equation. The fractional order of the equation conforms with the previous finding that the fluctuations of the magnetosphere-ionosphere system as seen in the AE reflect the fluctuations in the solar wind: they both possess the same extent of long-range dependence. The introduction of a fractional derivative term into the equation to capture the extent of long-range dependence together with an inverse Gaussian noise input describe the right amount of intermittency inherent in the AE data.

  6. Theory for the asymmetry in the auroral ionization density profile for the generation of auroral infrasonic waves

    International Nuclear Information System (INIS)

    Traveling pressure waves with periods from 10 to 100 seconds are generated in the lower ionosphere by auroral electrojet current filaments as they move supersonically in an equatorward direction. The infrasonic waves produced by the auroral motions propagate to the ground as highly directional bow waves that can be detected by infrasonic microphones on the surface. There is an asymmetry in the reception of auroral infrasonic waves (AIW) with respect to whether the auroral arcs are moving equatorward to poleward. In the literature it is suggested that the asymmetry may be due to anisotropic propagation conditions along the acoustic ray path from the E-region, where AIW are produced, to the surface. Some intrinsic property of the AIW generation mechanism itself has also been suggested as a possible explanation. In this thesis anisotropic propagation is eliminated as the cause of the AIW reception asymmetry. Theoretical calculations, beginning with a model of an auroral precipitation region, are presented to show that there can be a significant difference in the transverse ionization density profiles between an auroral arc that is moving equatorward and an arc that is moving poleward, for a given equatorward-directed E-region ambient electric field. The calculation has been accomplished by solving the equations of motion and continuity for the cross-sectional ionization density profile associated with the transverse motion of a filamentary auroral electrojet. Thus, it is shown that there is an asymmetry in the ionization profiles associated with moving arcs, and in their coupling, that is related to the relative direction of motion of the arc with respect to the ambient electric field, and that it is this asymmetry that is probably the cause of the observed AIW reception asymmetry

  7. [Percutaneous closure of patent foramen ovale: a wise approach].

    Science.gov (United States)

    Gaspardone, Achille; Iani, Cesare; Papa, Marco

    2008-09-01

    Patent foramen ovale (PFO) is a remnant of the normal fetal circulation consisting in a communication between septum primum and septum secundum. Postnatally, the two septa fuse completing separation of the atria. In 25% of normal individuals incomplete fusion leads to the persistence of the flap valve leaving a PFO. In the recent years a variety of clinical conditions has been associated with or attributed to PFO. In particular, PFO has been implicated in the pathogenesis of cryptogenic stroke/transient ischemic attack due to paradoxical embolism and to the pathogenesis of migraine headache. PFO has also been associated with decompression illness in divers and to minor diseases such as platypnea-orthodeoxia syndrome and high-altitude pulmonary edema. Meta-analyses and observational studies indicate that the prevalence of PFO is approximately 3-fold higher in patients with cryptogenic stroke and migraineurs compared controls. Conversely, observational evidences indicate a 2-3-fold increased prevalence of migraine and cerebrovascular events in PFO carriers. Observational studies and meta-analyses suggest that, compared to optimal medical treatment, transcatheter closure of PFO might significantly reduce the recurrence of ischemic cerebrovascular events in patients with previous stroke/transient ischemic attack; however, albeit mechanical closure of PFO is an attractive alternative to medical therapy, randomized trials supporting the efficacy of this approach have not been completed. Furthermore, about 80% of patients undergoing PFO closure for nonmigraine indications reported improvement in their migraine symptoms. However, these studies were predominantly retrospective, nonrandomized and conducted in highly selected populations. The recently published MIST trial, the only randomized study available, failed to demonstrate a significant favorable effect of PFO closure for migraine resolution and/or migraine improvement. At present, as insufficient evidence exists to

  8. DMSP Auroral Charging at Solar Cycle 24 Maximum

    Science.gov (United States)

    Chandler, M.; Parker, L. Neergaard; Minow, J. I.

    2013-01-01

    It has been well established that polar orbiting satellites can experience mild to severe auroral charging levels (on the order of a few hundred volts to few kilovolts negative frame potentials) during solar minimum conditions. These same studies have shown a strong reduction in charging during the rising and declining phases of the past few solar cycles with a nearly complete suppression of auroral charging at solar maximum. Recently, we have observed examples of high level charging during the recent approach to Solar Cycle 24 solar maximum conditions not unlike those reported by Frooninckx and Sojka. These observations demonstrate that spacecraft operations during solar maximum cannot be considered safe from auroral charging when solar activity is low. We present a survey of auroral charging events experienced by the Defense Meteorological Satellite Program (DMSP) F16 satellite during Solar Cycle 24 maximum conditions. We summarize the auroral energetic particle environment and the conditions necessary for charging to occur in this environment, we describe how the lower than normal solar activity levels for Solar Cycle 24 maximum conditions are conducive to charging in polar orbits, and we show examples of the more extreme charging events, sometimes exceeding 1 kV, during this time period.

  9. THE DUPLICATION OF THE FORAMEN OVALE IN HUMAN SKULLS OF SOUTH INDIAN POPULATION

    Directory of Open Access Journals (Sweden)

    Girish V

    2014-09-01

    Full Text Available Foramen ovale connects the middle cranial fossa to the infratemporal fossa. It is traversed by the mandibular nerve, accessory meningeal artery and lesser petrosal nerve and emissary vein which connects the cavernous venous sinus to the pterygoid venous plexus in the infratemporal fossa. Duplication of the Foramen ovale is a rare phenomenon. It is seen in both sexes and presents at various ages. Racal difference has also been reported. The presence of duplication of Foramen ovale was studied in 100 adult human skulls, collected from the department of Anatomy & Forensic medicine. It includes 30 skulls aged below 40 years of age and 70 skulls aged above 40 years. Duplication of foramen ovale was found in 3 skulls. All were unilateral (2 left and 1 Right. Knowledge regarding duplication of foramen ovale is useful during surgical exploration of the same especially during trigeminal neuralgia. Also the knowledge is useful in radio diagnosis of such conditions. The case may be mis - interpreted as any bony deformations.

  10. Dynamics of the AMPERE Region 1 Birkeland current oval during storms, substorms and steady magnetospheric convection

    Science.gov (United States)

    Baker, J. B.; Clausen, L.; Ruohoniemi, J. M.; Milan, S. E.; Kissinger, J.; Anderson, B. J.; Wing, S.

    2012-12-01

    Using radial current densities provided by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) we employ a fitting scheme to identify the location of the maximum Region 1 field-aligned (Birkeland) current at all magnetic local times. We call this parameter the "R1 oval" and we investigate its behavior during various modes of magnetospheric activity such as storms, substorms and steady magnetospheric convection (SMCs). Results show the following: (1) during substorms the radius of the R1 oval undergoes a cyclic inflation and contraction which matches the standard paradigm for substorm growth (loading) and expansion (unloading); (2) during SMCs the R1 oval is relatively steady consistent with balanced dayside and nightside reconnection during these events; and (3) during magnetic storms the size of the R1 oval is strongly correlated with the strength of the ring current specified by the Sym-H index. We also examine the behavior of the R1 oval in the northern and southern hemispheres simultaneously as a function of season in an effort to understand the role that internal magnetosphere-ionosphere coupling influences may play in modulating the response of the magnetosphere during these various types of events.

  11. Auroral Phenomenology and Magnetospheric Processes: Earth and Other Planets

    Science.gov (United States)

    Schultz, Colin

    2013-07-01

    The dancing glow of the aurorae, the long tendrils of light that seem to reach up into space, has mesmerized scientists for centuries. More than a beautiful display, the aurorae tell us about the Earth—about its atmosphere, its magnetic field, and its relationship with the Sun. As technology developed, researchers looking beyond Earth's borders discovered an array of auroral processes on planets throughout the solar system. In the AGU monograph Auroral Phenomenology and Magnetospheric Processes: Earth and Other Planets, editors Andreas Keiling, Eric Donovan, Fran Bagenal, and Tomas Karlsson explore the many open questions that permeate the science of auroral physics and the relatively recent field of extraterrestrial aurorae. In this interview, Eos talks to Karlsson about extraterrestrial aurorae, Alfvén waves, and the sounds of the northern lights.

  12. The Auroral Planetary Imaging and Spectroscopy (APIS) service

    CERN Document Server

    Lamy, Laurent; Henry, Florence; Sidaner, Pierre Le

    2015-01-01

    The Auroral Planetary Imaging and Spectroscopy (APIS) service, accessible online, provides an open and interactive access to processed auroral observations of the outer planets and their satellites. Such observations are of interest for a wide community at the interface between planetology and magnetospheric and heliospheric physics. APIS consists of (i) a high level database, built from planetary auroral observations acquired by the Hubble Space Telescope (HST) since 1997 with its mostly used Far-UltraViolet spectro-imagers, (ii) a dedicated search interface aimed at browsing efficiently this database through relevant conditional search criteria and (iii) the ability to interactively work with the data online through plotting tools developed by the Virtual Observatory (VO) community, such as Aladin and Specview. This service is VO compliant and can therefore also been queried by external search tools of the VO community. The diversity of available data and the capability to sort them out by relevant physical...

  13. About the relationship between auroral electrojets and ring currents

    Directory of Open Access Journals (Sweden)

    A. Grafe

    Full Text Available The relationship between the storm-time ring current and the auroral electrojets is investigated using IMAGE magnetometer data, DSt and H-SYM, and solar wind data. Statistical results as well as the investigation of single events show that the auroral electrojets occur also during nonstorm conditions without storm-time ring current development and even during the storm recovery phase of increasing DSt. A close correlation between electrojet intensity and ring current intensity was not found. Though the eastward electrojet moves equatorward during the storm main phase there is no unequivocal relationship between the movement of the westward electrojet and the ring current development. All these results suggest that the auroral electrojets and the ring current develop more or less independently of each other.

    Key words: Magnetospheric physics (magnetosphere-ionosphere interactions; storms and substorms

  14. Electric field measurements in the auroral E region

    International Nuclear Information System (INIS)

    Dipole electric field, positive ion and electron densities and temperatures, vehicle potential, and plasma sheath measurements have been made in the auroral E region by means of rockets flown from Fort Churchill, Canada. These results are described and compared over the altitude region 100 to 165 km. On a rocket flight launched on 10 December 1969 during very quiet conditions, adjacent to a stable, low intensity auroral arc, the plasma density and temperatures are found to be high and the electric fields large and steady. Electric field components of the order of -17 mv m-1 to +6 mv m-1 were measured along the Earth's magnetic field. The plasma results indicate that these fields may be contributing to enhanced electron temperatures. On a flight of 9 March 1970 during a large magnetic storm with widespread auroral activity, lower plasma densities and temperatures and much smaller and more erratic electric fields were observed with no significant component parallel to the magnetic field. (auth)

  15. Auroral emission at Jupiter, through Juno's UVS eyes

    OpenAIRE

    Grodent, Denis; Bonfond, Bertrand; Gladstone, G.; Gérard, Jean-Claude; Gustin, Jacques; Radioti, Aikaterini; Dumont, Maïté; Palmaerts, Benjamin; The Juno Science Team

    2015-01-01

    Juno’s orbit insertion around Jupiter will take place in little bit more than one year (July 2016). After a 107-day capture orbit (Oct. 2016), it will perform a series of 33 eleven-day science polar orbits offering unprecedented views of the auroral regions of Jupiter. The science payload of Juno includes an UltraViolet Spectrograph (UVS) that will characterize the UV auroral emissions of Jupiter over all science orbits. It will obtain high-resolution images and spectra that will provide cont...

  16. Auroral electron acceleration by lower-hybrid waves

    International Nuclear Information System (INIS)

    Because the particles and electric fields association with inverted-V electron streams do not have the characteristics expected for acceleration by a quasistatic potential difference, the possiblity that the electrons are stochastically accelerated by waves is investigated. It is demonstrated that the lower hybrid waves seen on auroral field lines have the righ properties to account for the electron acceleration. It is further shown that the lower hybrid wave power measured on auroral field lines can be generated by the streaming ions observed at the boundary of the plasma sheet, and that this wave power is sufficient to account for the electron power observed close to the atmosphere. (author)

  17. V and V Efforts of Auroral Precipitation Models: Preliminary Results

    Science.gov (United States)

    Zheng, Yihua; Kuznetsova, Masha; Rastaetter, Lutz; Hesse, Michael

    2011-01-01

    Auroral precipitation models have been valuable both in terms of space weather applications and space science research. Yet very limited testing has been performed regarding model performance. A variety of auroral models are available, including empirical models that are parameterized by geomagnetic indices or upstream solar wind conditions, now casting models that are based on satellite observations, or those derived from physics-based, coupled global models. In this presentation, we will show our preliminary results regarding V&V efforts of some of the models.

  18. Height-integrated conductivity in auroral substorms. 1. Data

    DEFF Research Database (Denmark)

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    We present height-integrated Hall and Pedersen conductivity (conductance) calculations from 31 individual Dynamics Explorer 2 (DE 2) substorm crossings. All are northern hemisphere (except one) nighttime passes which took place from September 1981 to January 1982. Global auroral images are used to...... select substorms which display a typical bulge-type auroral emission pattern and to organize the position of individual DE 2 passes with respect to key features in the emission pattern. The Hall and Pedersen conductances are calculated from electron precipitation data obtained by the low altitude plasma...

  19. Analysis of auroral infrared emissions observed during the ELIAS experiment

    Directory of Open Access Journals (Sweden)

    G. E. Caledonia

    Full Text Available The ELIAS (Earth Limb Infrared Atmospheric Structure experiment was flown from the Poker Flat Research Range, Alaska in 1983 and successfully monitored visible and infrared emissions from an IBC III+ aurora. Measurements were performed in both staring and scanning modes over several hundred seconds. The data for short- and mid-wave infrared regions have been analyzed in terms of auroral excitation of the NO and NO+ vibrational bands. Auroral excitation efficiencies and kinetic implications are presented.

  20. Jupiter's Various Auroral Emission Enhancements Observed by Hisaki/EXCEED

    Science.gov (United States)

    Tao, Chihiro

    2016-07-01

    Onboard a JAXA Earth-orbiting platform, the planetary telescope Hisaki monitors extreme ultraviolet emissions from Jovian aurora and Io plasma torus continuously. Hisaki succeeded to detect sporadic, large auroral power enhancements displaying both short- (a few rotations) variations and their modulations by Io's volcanic activity over several weeks. The spectral information taken by Hisaki enables us to investigate (1) the time variation of the auroral electron precipitating fluxes during these emission enhancements, (2) the occurrence statistics of polar-dominant events, and (3) the associated magnetospheric dynamics for these emission enhancement events using Knight's aurora acceleration theory. Expected collaborative observations with Juno will be discussed.

  1. Feedback between neutral winds and auroral arc electrodynamics

    Science.gov (United States)

    Lyons, L. R.; Walterscheid, R. L.

    1986-01-01

    The feedback between neutral atmospheric winds and the electrodynamics of a stable, discrete auroral arc is analyzed. The ionospheric current continuity equation and the equation for neutral gas acceleration by ion drag are solved simultaneously, as a function of time. The results show that, in general, the electric field in the ionosphere adjusts to neutral wind acceleration so as to keep auroral field-aligned currents and electron acceleration approximately independent of time. It is thus concluded that the neutral winds that develop as a result of the electrodynamical forcing associated with an arc do not significantly affect the intensity of the arc.

  2. Adult brain abscess associated with patent foramen ovale: a case report

    Directory of Open Access Journals (Sweden)

    Stathopoulos Georgios T

    2007-08-01

    Full Text Available Abstract Brain abscess results from local or metastatic septic spread to the brain. The primary infectious site is often undetected, more commonly so when it is distant. Unlike pediatric congenital heart disease, minor intracardiac right-to-left shunting due to patent foramen ovale has not been appreciated as a cause of brain abscess in adults. Here we present a case of brain abscess associated with a patent foramen ovale in a 53-year old man with dental-gingival sepsis treated in the intensive care unit. Based on this case and the relevant literature we suggest a link between a silent patent foramen ovale, paradoxic pathogen dissemination to the brain, and development of brain abscess.

  3. Anthralin is a potent inhibitor of pityrosporum orbiculare/ovale in vitro.

    Science.gov (United States)

    Bunse, T; Mahrle, G

    1992-01-01

    Two strains of Pityrosporum orbiculare/ovale were grown in a liquid medium and exposed to different concentrations of the imidazoles ketoconazole and clotrimazole as well as anthralin, liquor carbonis detergens and salicylic acid. With regard to growth inhibition of yeast cells, the efficacies of anthralin and the imidazoles were similar, a half-maximal inhibition being achieved with an anthralin concentration of 7 mg/l. Liquor carbonis detergens and salicylic acid also inhibited growth of Pityrosporum orbiculare/ovale, but only at much higher concentrations. The response to salicylic acid was mainly due to its acid pH. PMID:1350155

  4. ISOLATION OF Ricket tsia bellii FROM Amblyomma ovale AND Amblyomma incisum TICKS FROM SOUTHERN BRAZIL

    OpenAIRE

    Richard Pacheco; Simone Rosa; Leonardo Richtzenhain; Szabó, Matias P. J.; Marcelo B Labruna

    2008-01-01

    Objetivo. Aislar Rickettsias mediante cultivo celular a partir de muestras de garrapatas Amblyomma ovale y Amblyomma incisum del estado de São Paulo Materiales y métodos. A. ovale y A. incisum adultas de vida libre fueron colectadas en una área de selva tropical Atlántica en el estado de São Paulo, Brazil. Cada garrapata fue sometida a la prueba de hemolinfa, las garrapatas positivas en esta prueba fueron evaluadas con la técnica de shell vial con el propósito de aislar rickettsias en cultivo...

  5. Notas de ixodologia: IX. O complexo ovale do gênero Amblyomma

    Directory of Open Access Journals (Sweden)

    Henrique Aragão

    1961-07-01

    Full Text Available It was impossible to confirm either WARBUTON's conservative nor TONELLI RONDELLI's opposite belief on the number of valid species after studying many lots of ticks of the ovale group, mainly from Brazil. Two species are recognized: Amblyomma ovale Koch, 1844 and Amblyomma aureolatum (Pallas, 1772, corresponding respectively to A. fossum Neumann, 1898 and A. stratum Koch, 1844. A list of synonyms is presented. Both species are redescribed and intraspecific morphological variation show to be the cause of the multiplication of species by those working with insufficient material. Color plates of both species are presented and hosts and localities of captures are recorded.

  6. Fractal approach to the description of the auroral region

    Energy Technology Data Exchange (ETDEWEB)

    Chernyshov, A. A., E-mail: achernyshov@iki.rssi.ru; Mogilevsky, M. M. [Russian Academy of Sciences, Space Research Institute (Russian Federation); Kozelov, B. V. [Russian Academy of Sciences, Polar Geophysical Institute, Kola Science Center (Russian Federation)

    2013-07-15

    The plasma of the auroral region, where energetic particles precipitate from the magnetosphere into the ionosphere, is highly inhomogeneous and nonstationary. In this case, traditional methods of classical plasma physics turn out to be inapplicable. In order to correctly describe the dynamic regimes, transition processes, fluctuations, and self-similar scalings in this region, nonlinear dynamics methods based of the concepts of fractal geometry and percolation theory can be used. In this work, the fractal geometry and percolation theory are used to describe the spatial structure of the ionospheric conductivity. The topological properties, fractal dimensions, and connective indices characterizing the structure of the Pedersen and Hall conductivities on the nightside auroral zone are investigated theoretically. The restrictions imposed on the fractal estimates by the condition of ionospheric current percolation are analyzed. It is shown that the fluctuation scalings of the electric fields and auroral glow observed in the auroral zone fit well the restrictions imposed by the critical condition on the percolation of the Pedersen current. Thus, it is demonstrated that the fractal approach is a promising and convenient method for studying the properties of the ionosphere.

  7. First results of the Auroral Turbulance II rocket experiment

    DEFF Research Database (Denmark)

    Danielides, M.A.; Ranta, A.; Ivchenco, N.;

    1999-01-01

    The Auroral Turbulance II sounding rocket was launched on February 11, 1997 into moderately active nightside aurora from the Poker Flat Research Range, Alaska, US. The experiment consisted of three independent, completely instrumented payloads launched by a single vehicle. The aim of the experiment...

  8. Stepwise Progression of Right-to-Left Atrial Shunting through a Combination of Patent Foramen Ovale and Tricuspid Regurgitation

    Science.gov (United States)

    Kransdorf, Lisa N.; Fortuin, F. David; Sweeney, John P.; Wilansky, Susan

    2016-01-01

    Patent foramen ovale is a common clinical finding that generally becomes a concern in the presence of transient ischemic attack or stroke. Rarely, patent foramen ovale is associated with hypoxemia in the presence of substantial right-to-left atrial shunting. We present the case of an 86-year-old woman with a pacemaker, who was initially asymptomatic notwithstanding a patent foramen ovale. Over 1.5 years, her symptoms progressed in a stepwise fashion, in the setting of progressive pacemaker-associated tricuspid regurgitation. Ultimately, the patient's symptoms and her hypoxemia resolved after percutaneous closure of her patent foramen ovale with use of a 25-mm “Cribriform” occluder device. This case highlights the fact that clinically significant right-to-left shunting requires an anatomic lesion, such as patent foramen ovale, together with elevated right atrial pressure, which in this case was contributed by severe tricuspid regurgitation.

  9. Characterization and diagnostic methods for geomagnetic auroral infrasound waves

    Science.gov (United States)

    Oldham, Justin J.

    Infrasonic perturbations resulting from auroral activity have been observed since the 1950's. In the last decade advances in infrasonic microphone sensitivity, high latitude sensor coverage, time series analysis methods and computational efficiency have elucidated new types of auroral infrasound. Persistent periods of infrasonic activity associated with geomagnetic sub-storms have been termed geomagnetic auroral infrasound waves [GAIW]. We consider 63 GAIW events recorded by the Fairbanks, AK infrasonic array I53US ranging from 2003 to 2014 and encompassing a complete solar cycle. We make observations of the acoustic features of these events alongside magnetometer, riometer, and all-sky camera data in an effort to quantify the ionospheric conditions suitable for infrasound generation. We find that, on average, the generation mechanism for GAIW is confined to a region centered about ~60 0 longitude east of the anti-Sun-Earth line and at ~770 North latitude. We note furthermore that in all cases considered wherein imaging riometer data are available, that dynamic regions of heightened ionospheric conductivity periodically cross the overhead zenith. Consistent features in concurrent magnetometer conditions are also noted, with irregular oscillations in the horizontal component of the field ubiquitous in all cases. In an effort to produce ionosphere based infrasound free from the clutter and unknowns typical of geophysical observations, an experiment was undertaken at the High Frequency Active Auroral Research Program [HAARP] facility in 2012. Infrasonic signals appearing to originate from a source region overhead were observed briefly on 9 August 2012. The signals were observed during a period when an electrojet current was presumed to have passed overhead and while the facilities radio transmitter was periodically heating the lower ionosphere. Our results suggest dynamic auroral electrojet currents as primary sources of much of the observed infrasound, with

  10. Energy levels and far-infrared spectra of oval-shaped nanorings

    Science.gov (United States)

    Gutiérrez, W.; García, L. F.; Mikhailov, I. D.

    2014-05-01

    The evolution of the Aharonov-Bohm oscillation of low-lying states and far infrared spectrum associated to variation of the path curvature for electron motion along nanorings with centerlines in a form of a set of Cassini ovals, whose shape is changed continuously from a single elongated loop to two separated loops is theoretically investigated.

  11. Energy levels and far-infrared spectra of oval-shaped nanorings

    International Nuclear Information System (INIS)

    The evolution of the Aharonov-Bohm oscillation of low-lying states and far infrared spectrum associated to variation of the path curvature for electron motion along nanorings with centerlines in a form of a set of Cassini ovals, whose shape is changed continuously from a single elongated loop to two separated loops is theoretically investigated

  12. Intracranial lipoma with extracranial extension through foramen ovale in a patient with encephalocraniocutaneous lipomatosis syndrome

    Energy Technology Data Exchange (ETDEWEB)

    Fitoz, S. [Atatuerk Sitesi, Hayri Cecen S., Ankara (Turkey); Department of Radiology, University of Ankara School of Medicine, Ankara (Turkey); Atasoy, C.; Erden, I.; Akyar, S. [Department of Radiology, University of Ankara School of Medicine, Ankara (Turkey)

    2002-02-01

    We present CT and MR features of a large intracranial lipoma located in the left sphenocavernosal region in a patient with a history of spinal intradural lipoma excision. The lipomatous lesion surrounded the internal carotid artery and trigeminal nerve and extended extracranially into the infratemporal region through a smoothly dilated foramen ovale. (orig.)

  13. CT-guided percutaneous adriamycin injection blocking foramen ovale in the treatment of trigeminal neuralgia

    International Nuclear Information System (INIS)

    Objective: To investigate the technique and clinical value of CT-guided percutaneous adriamycin injection blocking foramen ovale in the treatment of trigeminal neuralgia. Methods: Sixty-three patients (24 males, 39 females; the age ranged from 43 to 77 years with a mean of 59) with trigeminal neuralgia were treated with percutaneous adriamycin injection by CT-guided foramen ovale blocking therapy. All the patients were diagnosed with typical symptoms and had been treated by medicine, and 38 of them were also treated by other operation approaches (27 by chemical medicine blocking, 7 by radiofrequency thermocoagulation, and 4 by microvascular decompression). Results: All patients were successfully treated by CT-guided adriamycin blocking therapy. Adriamycin (0.2-0.5 ml) was slowly and fractionally injected when the tip was ascertained in ganglion of foramen ovale. Instant total pain relief was obtained in 61 cases (96.8%), obvious pain relief in 1 and slight relief in 1. After the initial procedure, pain relief rate at 6 and 12 months was 84.1% and 79.4% , respectively. No serious complications occurred. Conclusion: CT-guided percutaneous foramen ovale blocking therapy was a precise, non-painful, highly effective, mini-traumatic, and safe treatment, and it was also an alternative treatment to classic technique. (authors)

  14. Energy levels and far-infrared spectra of oval-shaped nanorings

    Energy Technology Data Exchange (ETDEWEB)

    Gutiérrez, W.; García, L. F.; Mikhailov, I. D. [Escuela de Física, Universidad Industrial de Santander, A. A. 678, Bucaramanga (Colombia)

    2014-05-15

    The evolution of the Aharonov-Bohm oscillation of low-lying states and far infrared spectrum associated to variation of the path curvature for electron motion along nanorings with centerlines in a form of a set of Cassini ovals, whose shape is changed continuously from a single elongated loop to two separated loops is theoretically investigated.

  15. Semi-Analytical Weight Estimation Method for Fuselages with Oval Cross-Section

    NARCIS (Netherlands)

    Vos, R.; Hoogreef, M.F.M.

    2013-01-01

    This paper presents a semi-analytical method for the weight estimation of fuselages with an oval cross-section, applied to blended wing body aircraft. The weight estimation of the fuselage primary structure is based on a structural analysis of two-dimensional crosssections and it is completed by a s

  16. Auroral electrostatic solitons and supersolitons in a magnetized nonthermal plasma

    Energy Technology Data Exchange (ETDEWEB)

    Rufai, O. R. [Council for Scientific and Industrial Research, NRE, Pretoria (South Africa)

    2015-05-15

    Exploiting the spacecraft measurements in the auroral region, finite amplitude nonlinear low frequency electrostatic solitons and supersolitons in a magnetized plasma consisting of cold ions fluid, Boltzmann protons, and nonthermal hot electrons are studied by applying a pseudo-potential technique. The localized solution of the nonlinear structures is obtained through the charge neutrality condition. Further numerical investigation shows the existence of supersoliton solutions at supersonic Mach numbers regime. The amplitude of ion-acoustic structures decreased with an increase in nonthermal electrons and ion density ratio. For the plasma parameters relevant to the auroral zone of the Earth's magnetosphere, the electric field amplitude of supersolitons is found to be about 9 mV/m, which is in agreement with satellite observations.

  17. Hollowness of the observed auroral kilometric radiation pattern

    International Nuclear Information System (INIS)

    Presumably also generated by electron cyclotron emission, the earth's auroral kilometric radiation would be expected to exhibit a hollow pattern in the direction of the source magnetic field, similar to that reported for the comparable emissions from Jupiter. Although previously overlooked, such hollowness is clearly present in the new pattern measurements of Green and Gallagher (1985) at 56 kHz, occupying source-centered latitudes of 30 degree to 45 degree and hence occurring exactly where it was predicted and previously observed. Being distributed in longitude and spanning the entire evening sector, presumably reflecting a similar longitudinal distribution of auroral zone sources, this hollowness is attributed to sources beamed preferentially in the poleward magnetic meridian

  18. Auroral Undulations During Magnetic Storms: TIMED/GUVI Observations

    Science.gov (United States)

    Zhang, Y.; Paxton, L. J.; Morrison, D.; Lui, T.; Kil, H.; Wolven, B.; Meng, C. I.

    2005-05-01

    Giant undulations on the equatorward edge of the diffuse aurora have been identified in TIMED/GUVI auroral images in the far ultraviolet wavelengths. Some new features have been observed: (1) The GUVI 121.6nm auroral images provide direct optical evidence that the undulations occur in the proton aurora, (2) Undulations are not limited to the dusk sector, they can occur in all local time sectors, (3) Both large ionospheric ion drift velocity (1000 m/s and above) and strong velocity shear (> 0.1 1/s) appear to be a necessary condition for the undulation to occur, (4) While almost all of the undulation events are observed during magnetic storms (Dst K-H instability.

  19. A simple kinetic theory of auroral arc scales

    Science.gov (United States)

    Chiu, Y. T.

    1986-01-01

    A kinetic theory of the origins of the auroral arc scale spectrum is presented in this paper. The conceptual basis of the theory is current conservation in a turbulent plasma at the magnetospheric equatorial region in which a field-aligned current is generated and the local electrostatic potential structure is forced to adjust to the presence of the field-aligned current. This simple model uses an ad hoc Ohm's law relationship between the perpendicular current and the perpendicular electric field, but with a negative conductance in the generator region so that J(perpendicular) x E(perpendicular) is less than 0. An exact solution of a simple model of the concept yields a bistatic auroral generator for which multiple-arc formation is predicted if the field-aligned current exceeds a critical value. The predicted scale spectrum is inversely proportional to the square root of the field-aligned current strength spectrum.

  20. Height-integrated conductivity in auroral substorms - 2. Modeling

    DEFF Research Database (Denmark)

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    Calculations of height-integrated conductivity from 31 individual Dynamics Explorer (DE 2) substorm crossings presented by Gjerloev and Hoffman [this issue] are used to compile empirical models of the height-integrated Pedersen and Hall conductivities (conductances) in a bulge-type auroral substorm....... Global auroral images obtained by Dynamics Explorer 1 (DE 1) were used to select substorms displaying a typical bulge-type emission pattern and each individual DE 2 pass was positioned with respect to key features in the observed emission pattern. The conductances were calculated for each DE 2 pass using...... electron precipitation data and a monoenergetic conductance model. All passes were divided into six different sectors, and average conductance profiles were carefully deduced for each of these sectors. Using a simple boxcar filter, smoothed average sector passes were calculated and from linear...

  1. Threshold of auroral intensification reduced by electron precipitation effect

    CERN Document Server

    Hiraki, Yasutaka

    2016-01-01

    It has been known that discrete aurora suddenly intensifies and deforms from an arc-like to a variety of wavy/vortex structures, especially during a substorm period. The instability of Alfv$\\acute{\\rm e}$n waves reflected from the ionosphere has been analyzed in order to comprehend the ignition process of auroral intensification. It was presented that the prime key is an enhancement of plasma convection, and the convection electric field has a threshold. This study examined effects of auroral electron precipitation, causing the ionization of neutral atmosphere, on the linear instability of Alfv$\\acute{\\rm e}$n waves. It was found that the threshold of convection electric fields is significantly reduced by increasing the ionization rate, the realistic range of which could be estimated from observed electron energy spectra.

  2. Particle simulation of auroral double layers. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Smith, B.L.

    1992-06-01

    Externally driven magnetic reconnection has been proposed as a possible mechanism for production of auroral electrons during magnetic substorms. Fluid simulations of magnetic reconnection lead to strong plasma flows towards the increasing magnetic field of the earth. These plasma flows must generate large scale potential drops to preserve global charge neutrality. We have examined currentless injection of plasma along a dipole magnetic field into a bounded region using both analytic techniques and particle simulation.

  3. Ion cyclotron harmonics in the Saturn downward current auroral region

    OpenAIRE

    Menietti, J.D.; Schippers, P.; Santolík, O; Gurnett, D. A.; Crary, F.; Coates, A. J.

    2011-01-01

    Observations of intense upgoing electron beams and diffuse ion beams have been reported during a pass by Cassini in a downward current auroral region, nearby a source region of Saturn kilometric radiation. Using the Cassini Radio and Plasma Wave Science (RPWS) instrument low frequency waveform receiver and the Cassini Plasma Spectrometer Investigation (CAPS) instrument we have been able to identify ion cyclotron harmonic waves associated with the particle beams. These observations indicate si...

  4. Coordinated ATS 5 electron flux and simultaneous auroral observations

    International Nuclear Information System (INIS)

    All-sky camera (ASCA) observations were made at the field line conjugate of the ATS 5 satellite. The field of view of these cameras covered the region of the magnetosphere from L=5 to L=11 at the approximate longitude of the ATS field line conjugate. With this coverage, definite statements can be made concerning the correlation of the auroras observed by the ASCA's and the magnetospheric trapped fluxes. In general, auroral forms are not simply correlated with the synchronous altitude electron fluxes. The presence of hot plasma at the ATS 5 satellite is a necessary but not sufficient condition for the occurrence of local auroras. On quiet days the hot plasma does not penetrate into the magnetosphere far enough to reach the ATS 5 orbit. Under these conditions, no auroras are observed at the field line conjugate, but auroras are usually observed on higher-latitude field lines. On more disturbed days, auroral arcs are observed at lower latitudes when the plasma sheet penetrates into the ATS 5 orbit. There is no general correlation between the intensity of the trapped electron fluxes observed by ATS 5 and the intensity of auroras observed by the ASCA's. Auroral displays exhibit very fast fluctuations, whereas the ATS 5 electron fluxes change on a much slower time scale. However, significant qualitative correlation between the ASCA data and the trapped fluxes is observed when a local plasma injection event occurs near ATS 5. The clearest signature of the injection event is magnetic and is most pronounced as a recovery of a negative bay in the north-south component of the field at the ATS 5. The local injection generally produces structured auroras such as breakup events and sometimes westward-traveling surges. A significant correlation is observed with the intensification of a diffuse uniform glow accompanying the structured auroral activity

  5. Control factor of solar cycle variation of auroral kilometric radiation

    OpenAIRE

    Kumamoto,Atsushi/Ono, Takayuki/Oya,Hiroshi

    2003-01-01

    Solar cycle variations of auroral kilometric radiation (AKR) observed by the Akebono satellite have been compared with the variations of F10.7 and solar wind dynamic pressure. F10.7 and solar wind dynamic pressure show different solar cycle variations: F10.7 increases during solar maximum and decreases during solar minimum. Solar wind dynamic pressure suddenly increases in the declining phase of solar activity and gradually decreases. The pressure minimum occurs during solar maximum. Statisti...

  6. Visualizing Space Weather: The Planeterrella Auroral Simulator as a Heliophysics Public Outreach Tool

    Science.gov (United States)

    Masongsong, E. V.; Lilensten, J.; Booth, M. J.; Suri, G.; Heflinger, T. G.; Angelopoulos, V.

    2014-12-01

    The NASA THEMIS and ARTEMIS satellite missions study "space weather," which describes the solar wind influence on Earth's protective magnetic shield, the magnetosphere. Space weather is important to study and predict because it can damage critical GPS and communications satellites, harm space travelers, and even disable our global electrical grid. The Planeterrella is an innovative heliophysics outreach demonstration, expanding public awareness of space weather by visualizing the sun-Earth connection up close and in-person. Using a glass vacuum chamber, two magnetized spheres and a 1kV power supply, the device can simulate plasma configurations of the solar corona, solar wind, Van Allen radiation belts, and auroral ovals, all of which are observable only by satellites. This "aurora in a bottle" is a modernized version of the original Terrella built by Kristian Birkeland in the 1890s to show that the aurora are electrical in nature. Adapted from plans by Lilensten et al. at CNRS-IPAG, the UCLA Planeterrella was completed in Nov. 2013, the second device of its kind in the U.S., and the centerpiece of the THEMIS/ARTEMIS mobile public outreach exhibit. In combination with captivating posters, 3D magnetic field models, dazzling aurora videos and magnetosphere animations, the Planeterrella has already introduced over 1200 people to the electrical link between our sun and the planets. Most visitors had seen solar flare images in the news, however the Planeterrella experience enhanced their appreciation of the dynamic solar wind and its effects on Earth's invisible magnetic field. Most importantly, visitors young and old realized that magnets are not just cool toys or only for powering hybrid car motors and MRIs, they are a fundamental aspect of ongoing life on Earth and are key to the formation and evolution of planets, moons, and stars, extending far beyond our galaxy to other planetary systems throughout the universe. Novel visualizations such as the Planeterrella can

  7. Latitudinal and longitudinal dispersion of energetic auroral protons

    Directory of Open Access Journals (Sweden)

    D. A. Lorentzen

    Full Text Available Using a collision by collision model from Lorentzen et al., the latitudinal and longitudinal dispersion of single auroral protons are calculated. The proton energies varies from 1 to 50 keV, and are released into the atmosphere at 700 km altitude. The dipole magnetic field has a dip-angle of 8 degrees. Results show that the main dispersion region is at high altitudes (300-350 km and occurs during the first few charge exchange collisions. As the proton travels further down the atmosphere the mean free path becomes smaller, and as a result the spreading effect will not be as pronounced. This means that the first few charge exchange collisions fully determines the width of both the latitudinal and longitudinal dispersion. The volume emission rate was calculated for energies between 1 and 50 keV, and it was found that dayside auroral hydrogen emissions rates were approximately 10 times weaker than nightside emission rates. Simulations were also performed to obtain the dependence of the particle dispersion as a function of initial pitch-angle. It was found that the dispersion varies greatly with initial pitch-angle, and the results are summarized in two tables; a main and an extreme dispersion region.

    Key words. Ionosphere (auroral ionosphere; · particle precipitation · Space plasma physics · (transport processes

  8. Auroral Spatial Structures Probe Sub-Orbital Mission Preliminary Results

    Science.gov (United States)

    Pratt, J.; Swenson, C.; Martineau, R. J.; Fish, C. S.; Conde, M.; Hampton, D.; Crowley, G.

    2015-12-01

    The NASA Auroral Spatial Structures Probe, 49.002, was launched January 28, 2015 from the Poker Flat Research Range into active aurora over the northern coast of Alaska. The primary objective of this mission was to determine the contribution of small spatial and temporal scale fluctuations of the electric fields to the larger-scale energy deposition processes associated with the aurora. The Auroral Spatial Structures Probe Sub-Orbital Mission consisted of a formation of 7 spacecraft (a main payload with 6 deployable sub-payloads) designed for multiple temporally spaced co-located measurements of electric and magnetic fields in the earth's ionosphere. The mission was able to make observations at a short time scale and small spatial scale convergence that is unobservable by either satellite or ground-based observations. The payloads included magnetometers, electric field double probes, and Langmuir probes as well as a sweeping impedance probe on the main payload. We present here preliminary results from the measurements taken that hint at the underlying spatial structure of the currents and energy deposition in the aurora. The Poynting flux derived from the observations is shown and implications are discussed in terms of the contribution of small spatial scale, rapid temporal scale fluctuations in the currents that deposit energy in the auroral region. Funding provided by NASA Grants NNX11AE23G and NNX13AN20A.

  9. Effects of interplanetary shock inclinations on auroral power intensity

    CERN Document Server

    Oliveira, D M; Tsurutani, B T; Gjerloev, J W

    2015-01-01

    We derive fast forward interplanetary (IP) shock speeds and impact angles to study the geoeffectivness of 461 IP shocks that occurred from January 1995 to December 2013 using ACE and WIND spacecraft data. The geomagnetic activity is inferred from the SuperMAG project data. SuperMAG is a large chain which employs more than 300 ground stations to compute enhanced versions of the traditional geomagnetic indices. The SuperMAG auroral electroject SME index, an enhanced version of the traditional AE index, is used as an auroral power (AP) indicator. AP intensity jumps triggered by shock impacts are correlated with both shock speed and impact angle. It is found that high AP intensity events typically occur when high speed IP shocks impact the Earths magnetosphere with the shock normal almost parallel to the Sun-Earth line. This result suggests that symmetric and strong magnetospheric compression leads to favorable conditions for intense auroral power release, as shown previously by simulations and observations. Some...

  10. Testing the Auroral Current-Voltage Relation in Multiple Arcs

    Science.gov (United States)

    Cameron, T. G.; Knudsen, D. J.; Cully, C. M.

    2013-12-01

    The well-known current-voltage relation within auroral inverted-V regions [Knight, Planet. Space Sci., 21, 741, 1973] predicts current carried by an auroral flux tube given the total potential drop between a plasma-sheet source region and the ionosphere. Numerous previous studies have tested this relation using spacecraft that traverse auroral arcs at low (ionospheric) or mid altitudes. Typically, the potential drop is estimated at the peak of the inverted-V, and field-aligned current is estimated from magnetometer data; statistical information is then gathered over many arc crossings that occur over a wide range of source conditions. In this study we use electron data from the FAST satellite to examine the current-voltage relation in multiple arc sets, in which the key source parameters (plasma sheet density and temperature) are presumed to be identical. We argue that this approach provides a more sensitive test of the Knight relation, and we seek to explain remaining variability with factors other than source variability. This study is supported by a grant from the Natural Sciences and Engineering Research Council of Canada.

  11. A hybrid simulation model for a stable auroral arc

    Directory of Open Access Journals (Sweden)

    P. Janhunen

    Full Text Available We present a new type of hybrid simulation model, intended to simulate a single stable auroral arc in the latitude/altitude plane. The ionospheric ions are treated as particles, the electrons are assumed to follow a Boltzmann response and the magnetospheric ions are assumed to be so hot that they form a background population unaffected by the electric fields that arise. The system is driven by assumed parallel electron energisation causing a primary negative charge cloud and an associated potential structure to build up. The results show how a closed potential structure and density depletion of an auroral arc build up and how they decay after the driver is turned off. The model also produces upgoing energetic ion beams and predicts strong static perpendicular electric fields to be found in a relatively narrow altitude range (~ 5000–11 000 km.

    Key words. Magnetospheric physics (magnetosphere-ionosphere interactions; auroral phenomena – Space plasma physics (numerical simulation studies

  12. 3D-modelling of the stellar auroral radio emission

    CERN Document Server

    Leto, P; Buemi, C S; Umana, G; Ingallinera, A; Cerrigone, L

    2016-01-01

    The electron cyclotron maser is the coherent emission process that gives rise to the radio lighthouse effect observed in the hot magnetic chemically peculiar star CU Virginis. It has also been proposed to explain the highly circularly polarized radio pulses observed on some ultra cool dwarfs, with spectral type earlier than M7. Such kind of coherent events resemble the auroral radio emission from the magnetized planets of the solar system. In this paper, we present a tridimensional model able to simulate the timing and profile of the pulses emitted by those stars characterized by a dipolar magnetic field by following the hypothesis of the laminar source model, used to explain the beaming of the terrestrial auroral kilometric radiation. This model proves to be a powerful tool to understand the auroral radio-emission phenomenon, allowing us to derive some general conclusions about the effects of the model's free parameters on the features of the coherent pulses, and to learn more about the detectability of such...

  13. E-region echo characteristics governed by auroral arc electrodynamics

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    Full Text Available Observations of a pair of auroral arc features by two imagers, one ground- and one space-based, allows the associated field-aligned current (FAC and electric field structure to be inferred. Simultaneous observations of HF radar echoes provide an insight into the irregularity-generating mechanisms. This is especially interesting for the E-region echoes observed, which form the focus of our analysis, and from which several conclusions can be drawn, summarized as follows. Latitudinal variations in echo characteristics are governed by the FAC and electric field background. Particularly sharp boundaries are found at the edges of auroral arcs. Within regions of auroral luminosity, echoes have Doppler shifts below the ion-acoustic speed and are proportional to the electric field, suggesting scatter from gradient drift waves. Regions of downward FAC are associated with mixed high and low Doppler shift echoes. The high Doppler shift component is greatly in excess of the ion-acoustic speed, but seems to be commensurate with the driving electric field. The low Doppler shift component appears to be much depressed below expectations.

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

  14. 3D modelling of stellar auroral radio emission

    Science.gov (United States)

    Leto, P.; Trigilio, C.; Buemi, C. S.; Umana, G.; Ingallinera, A.; Cerrigone, L.

    2016-06-01

    The electron cyclotron maser is the coherent emission process that gives rise to the radio lighthouse effect observed in the hot magnetic chemically peculiar star CU Virginis. It has also been proposed to explain the highly circularly polarized radio pulses observed in some ultracool dwarfs with spectral type earlier than M7. Coherent events of this kind resemble auroral radio emission from the magnetized planets of the Solar system. In this article, we present a three-dimensional model able to simulate the timing and profile of the pulses emitted by those stars characterized by a dipolar magnetic field by following the hypothesis of the laminar source model, used to explain the beaming of terrestrial auroral kilometric radiation. This model proves to be a powerful tool with which to understand the auroral radio emission phenomenon, allowing us to derive some general conclusions about the effects of the model's free parameters on the features of coherent pulses and to learn more about the detectability of such pulsed radio emission.

  15. Tromboembolismo pulmonar masivo de alto riesgo asociado a foramen oval permeable High-risk massive pulmonary thromboembolism associated with patent foramen ovale

    Directory of Open Access Journals (Sweden)

    Antonio Miranda

    2012-04-01

    Full Text Available La alta mortalidad de los pacientes con tromboembolismo pulmonar masivo de alto riesgo amerita un enfoque terapéutico enérgico e invasivo que incluya la embolectomía pulmonar quirúrgica en aquellos pacientes con contraindicación para trombolisis o trombolisis fallida. Describimos un caso de tromboembolismo pulmonar masivo de alto riesgo que recibió tratamiento quirúrgico en vez de trombolisis debido a que al momento del diagnóstico presentaba un trombo móvil a través de un foramen oval permeable con altísima posibilidad de embolismo paradójico arterial.High mortality rate associated with massive pulmonary embolism requires an aggressive invasive approach including surgical pulmonary embolectomy when thrombolytic therapy has failed or is contraindicated. We describe a case of high-risk massive pulmonary embolism who underwent surgical treatment due to the presence of a mobile intracardiac clot in a patent foramen ovale, and the possible risk of paradoxical arterial embolism.

  16. Experimental study on the spiral and oval spiral EGR cooler efficiencies in a diesel engine

    Science.gov (United States)

    Park, Sang-Ki; Lee, Jungkoo; Kim, Hyung-Man

    2014-12-01

    The cooled exhaust gas recirculation (EGR) system is one of the most effective techniques currently available for reducing nitrogen oxide emissions in diesel engine. Because the combustion characteristics in diesel engine involves high temperature and load, the amount of particulate matter (PM) emission tends to increase, thereby the PM fouling in EGR cooler degrades the heat transfer performance considerably, which in turn has a significant influence on the design of the EGR cooler. In the present study, engine dynamometer tests are performed to investigate the influences of PM fouling on the heat exchange characteristics of spiral and oval-spiral type EGR coolers equipped with a diesel engine. The evaluation test results show that the oval-spiral type EGR cooler has higher efficiency by approximate 10 % than the spiral type EGR cooler because of the increase of heat transfer area and the increased removal of PM from the deposit layer due to fluid shear force.

  17. Correzione percutanea del Forame Ovale Pervio : follow-up clinico-strumentale a lungo termine

    OpenAIRE

    Vignali, Luigi

    2009-01-01

    Circa il 30-40% degli stroke ischemici senza chiara eziologia vengono definiti criptogenetici, e nel loro meccanismo patogenetico sembra essere implicata la persistenza di forame ovale pervio (PFO). Il PFO sembra inoltre essere implicato nella patogenesi dell’emicrania con aura. Al fine di prevenire i fenomeni neurologici ischemici ricorrenti, la chiusura percutanea del PFO è stata considerata nella letteratura scientifica più recente, in alternativa alla terapia medica. Scopo dello stu...

  18. Cohort study of multiple brain lesions in sport divers: role of a patent foramen ovale.

    OpenAIRE

    Knauth, M; Ries, S.; Pohimann, S.; Kerby, T.; Forsting, M; Daffertshofer, M.; HENNERICI, M; Sartor, K

    1997-01-01

    OBJECTIVE: To investigate the role of a patient foramen ovale in the pathogenesis of multiple brain lesions acquired by sport divers in the absence of reported decompression symptoms. DESIGN: Prospective double blind cohort study. SETTING: Diving clubs around Heidelberg and departments of neuroradiology and neurology. SUBJECTS: 87 sport divers with a minimum of 160 scuba dives (dives with self contained underwater breathing apparatus). MAIN OUTCOME MEASURES: Presence of multiple brain lesions...

  19. Recurrent strokes under anticoagulation therapy: Sticky platelet syndrome combined with a patent foramen ovale

    OpenAIRE

    Gehoff, A.; Kluge, J. G.; Gehoff, P.; Jurisch, D.; Pfeifer, D; Hinz, J.; A. F. Popov

    2011-01-01

    The sticky platelet syndrome (SPS) is a congenital disorder characterized by platelet hyperaggregability to epinephrine and/or adenosine diphosphate; this predisposes affected individuals to acute myocardial infarction, ischemic optic neuropathy, recurrent venous thromboembolism, and transient ischemic cerebral attacks and strokes. Here, we describe an unusual case with recurrent cerebrovascular accidents due to SPS, in the presence of a patent foramen ovale (PFO). We report an unusual case o...

  20. Patent foramen ovale as a preferential mechanism for increasing the likelihood of brain tumor metastasis

    OpenAIRE

    Rigatelli, Gianluca; Rossi, Andrea; Dell'Avvocata, Fabio; Cardaioli, Paolo

    2011-01-01

    Metastases are the most common tumors of the central nervous system which may lie dormant behind the brain blood- barrier sheltering from chemiotherapeutic drugs, and whose presence usually indicates a poor prognosis. Development of brain metastases includes the intravasation of the cancer cells through the tumor blood vessels, their circulation within the venous system, passing through the pulmonary filter thus reaching the systemic circulation. Patent foramen ovale (PFO) is a natural commun...

  1. Cryptogenic Stroke Associated With Patent Foramen Ovale in a Collegiate Volleyball Athlete

    OpenAIRE

    Miyazawa, Aimee; Vardiman, Phillip; Magee, Lawrence M.; Washington, Erin

    2010-01-01

    Cryptogenic stroke is a form of cerebral vascular accident that has an unknown origin and is rarely associated with patent foramen ovale (PFO) and migraine headaches. This is an uncommon occurrence in young, healthy, active adults, and it is increasingly rare for the episode to occur during an athletic competition. Stroke is easily recognizable with its distinct signs and symptoms, but it is also easily confused with many of its differential diagnoses, such as seizures or head trauma, if the ...

  2. Performance of Rapid Diagnostic Tests for Plasmodium ovale Malaria in Japanese Travellers

    OpenAIRE

    Tanizaki, Ryutaro; Kato, Yasuyuki; Iwagami, Moritoshi; Kutsuna, Satoshi; Ujiie, Mugen; Takeshita, Nozomi; Hayakawa, Kayoko; Kanagawa, Shuzo; Kano, Shigeyuki; Ohmagari, Norio

    2014-01-01

    Background: Rapid diagnostic tests (RDTs) are used widely in the diagnosis of malaria. Although the effectiveness of RDTs for malaria has been described in many previous studies, the low performance of RDT particularly for Plasmodium ovale malaria in traveller has rarely been reported. Methods: This was a retrospective cohort study conducted on Japanese travellers diagnosed with malaria at the National Center for Global Health and Medicine between January 2004 and June 2013. The diagnosis of ...

  3. Effect of body position and oxygen tension on foramen ovale recruitment

    OpenAIRE

    Moses, Kayla L.; Beshish, Arij G.; Heinowski, Nicole; Baker, Kim R.; Pegelow, David F.; Eldridge, Marlowe W.; Bates, Melissa L.

    2014-01-01

    While there is an increased prevalence of stroke at altitude in individuals who are considered to be low risk for thrombotic events, it is uncertain how venous thrombi reach the brain. The patent foramen ovale (PFO) is a recruitable intracardiac shunt between the right and left atrium. We aimed to determine whether body position and oxygen tension affect blood flow through the PFO in healthy adults. We hypothesized that hypoxia and body positions that promote right atrial filling would indepe...

  4. Quasi-Stationary Global Auroral Ionospheric Model: E-layer

    Science.gov (United States)

    Nikolaeva, Vera; Gordeev, Evgeny; Kotikov, Andrey; Makarova, Ludmila; Shirochkov, Aleksander

    2014-05-01

    E-layer Auroral Ionospheric Model (E-AIM) is developed to provide temporal and spatial density distribution of the main ionosphere neutral species (NO, N(4S),N(2D)), and ions (N2+, NO+,O2+,O+) in the altitude range from 90 to 150 km. NRLMSISE-00 model [Picone et al., JGR 2003] is used for neutral atmosphere content and temperature determination, that is the input for the E-AIM model. The E-AIM model based on chemical equilibrium state in E-layer that reaches in chemical reactions between ionospheric species considering solar radiation ionization source, superposed with sporadic precipitation of magnetospheric electrons. The chemical equilibrium state in each location under specific solar and geomagnetic activity conditions reaches during numerical solution of the continuity equations for the neutrals and ions using the high-performance Gear method [Gear, 1971] for ordinary differential equation (ODE) systems. Applying the Gear method for solving stiff ODE system strongly reduce the computation time and machine resources comparing to widely used methods and provide an opportunity to calculate the global spatial E-layer ion content distribution. In contrast to the mid-latitude ionosphere, structure and dynamics of the auroral zone ionosphere (φ ≡ 60-75° MLat) associated not only with shortwave solar radiation. Precipitating magnetospheric particle flux is the most important ionization source and is the main cause of E-layer disturbances. Precipitated electrons with initial energies of 1 - 30 keV influence the auroral ionosphere E-layer. E-AIM model can estimate ionization rate corresponds to auroral electron precipitation in two different ways: 1. with direct electron flux satellite data; 2. with differential energy spectrum reconstructed from OVATION-Prime empirical model [Newell, JGR 2009] average values, that allows to estimate ionosphere ion content for any time and location in the auroral zone. Comparison of E-AIM results with direct ionospheric observations

  5. Can patent foramen ovale affect rehabilitation? The uncommon association of platypnea-orthodeoxia syndrome and stroke.

    Science.gov (United States)

    Gallerini, S; Calchetti, B; Cianchi, C; Di Troia, A M; Madonna, R; Cresti, A; Mancuso, M

    2011-06-01

    Platypnea-orthodeoxia is a rare syndrome characterized by dyspnea and deoxygenation induced by a change to a sitting or standing from a recumbent position. It is the result of posturally accentuated intracardiac or pulmonary right-to-left shunt leading to arterial oxygen desaturation. Only few cases of platypnea-orthodeoxia syndrome are reported in the literature and the association between stroke and platypnea-orthodeoxia syndrome with evidence of patent foramen ovale is extremely rare. We describe the case of a 67-year-old female admitted to our Rehabilitation Unit for disabling basilar stroke due to paradoxical embolism from patent foramen ovale that during the first days of rehabilitation showed signs and symptoms of platypnea-orthodeoxia syndrome. To remove a life-threatening condition for the patient and in order to develop the normal rehabilitation project, that was stopped by the platypnea-orthodeoxia syndrome, the patient fastly underwent to percutaneous closure of patent foramen ovale. The stabilization of oxygen arterial saturation with postural changes and the disappearance of symptoms of POS allowed to develop the rehabilitation project with progressive neurological improvement. PMID:21468677

  6. Dynamics of classical particles in oval or elliptic billiards with a dispersing mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Diogo Ricardo da [Instituto de Física da USP, Rua do Matão, Travessa R, 187, Cidade Universitária, CEP 05314-970 São Paulo, SP (Brazil); School of Mathematics, University of Bristol, Bristol (United Kingdom); Departamento de Física, UNESP-Univ Estadual Paulista, Av. 24A, 1515, 13506-900 Rio Claro, SP (Brazil); Dettmann, Carl P. [School of Mathematics, University of Bristol, Bristol (United Kingdom); Oliveira, Juliano A. de [UNESP-Univ Estadual Paulista, Câmpus de São João da Boa Vista, São João da Boa Vista, SP (Brazil); Leonel, Edson D. [Departamento de Física, UNESP-Univ Estadual Paulista, Av. 24A, 1515, 13506-900 Rio Claro, SP (Brazil)

    2015-03-15

    Some dynamical properties for an oval billiard with a scatterer in its interior are studied. The dynamics consists of a classical particle colliding between an inner circle and an external boundary given by an oval, elliptical, or circle shapes, exploring for the first time some natural generalizations. The billiard is indeed a generalization of the annular billiard, which is of strong interest for understanding marginally unstable periodic orbits and their role in the boundary between regular and chaotic regions in both classical and quantum (including experimental) systems. For the oval billiard, which has a mixed phase space, the presence of an obstacle is an interesting addition. We demonstrate, with details, how to obtain the equations of the mapping, and the changes in the phase space are discussed. We study the linear stability of some fixed points and show both analytically and numerically the occurrence of direct and inverse parabolic bifurcations. Lyapunov exponents and generalized bifurcation diagrams are obtained. Moreover, histograms of the number of successive iterations for orbits that stay in a cusp are studied. These histograms are shown to be scaling invariant when changing the radius of the scatterer, and they have a power law slope around −3. The results here can be generalized to other kinds of external boundaries.

  7. Comparison of Bacterial Leakage between 3 Different Root Canal Obturation Techniques in Oval Shaped Canals

    Directory of Open Access Journals (Sweden)

    Eshagh-ali Saberi

    2014-06-01

    Full Text Available Introduction: The purpose of this study was to evaluate the sealing ability of 3 obturation techniques in oval-shaped canals by bacterial leakage assessment. Methods: Sixty mandibular incisors with oval canals were selected after providing buccolingual and mesiodistal radiographs. The teeth were sectioned at a 10 mm distance from the apex. After instrumentation, the teeth were divided into 3 groups and the canals in the three groups were obturated with lateral condensation (G1, warm vertical condensation (G2 and thermoplasticized injectable gutta percha (G3. The teeth were exposed to human saliva. Observing the turbidity of the BHI broth for a period of 63 days the number of days required for the complete contamination of root canals was recorded. The data were analyzed using descriptive statistical methods and Kruskal-Wallis test with SPSS statistical software. Results: Warm vertical condensation (G2 needed a significantly greater average time for leakage than the two other methods. No significant differences were found between lateral condensations and thermoplasticized injectable G.P techniques. Conclusion: warm vertical condensation provides a better seal against bacterial leakage than lateral condensation and obtura II method in obturating oval-canals.

  8. Patent Foramen Ovale in Patients with Cerebral Infarction: A Transesophageal Echocradigraphy Study

    Science.gov (United States)

    Petty, George W.; Khandheria, Bijoy K.; Chu, Chu-Pin; Sicks, JoRean D.; Whisnant, Jack P.

    1997-01-01

    Patent foramen ovale was detected in 37 patients (32%). Mean age was similar in those with (60 years) and those without (64 years) PFO. Patent foramen ovale was more frequent among men (39%) than women (20%, P=.03). Patients with PFO had a lower frequency of atrial fibrillation, diabetes me!litus, hypertension, and peripheral vascular disease compared with those without PFO. There was no difference in frequency of the following characteristics in patients with PFO compared with those without PFO: pulmonary embolus, chronic obstructive pulmonary disease, pulmonary hypertension, peripheral embolism, prior cerebral infarction, nosocomial cerebral infarction, Valsalva maneuver at the time of cerebral infarction, recent surgery, or hemorrhagic transformation of cerebral infarction. Patent foramen ovale was found in 22 (40%) of 55 patients with infarcts of uncertain cause and in 15 (25%) of 61 with infarcts of known cause (cardioembolic, 21%; large vessel atherostenosis, 25%; lacune, 40%) (P=.08). When the analysis was restricted to patients who underwent Valsalva maneuver, PFO with right to left or bidirectional shunt was found in 19 (50%) of 38 patients with infarcts of uncertain cause and in 6 (20%) of 30 with infarcts of known cause (P=.Ol). Conclusion: Although PFO was over-represented in patients with infarcts of uncertain cause in our and other studies, it has a high frequency among patients with cerebral infarction of all types. The relation between PFO and stroke requires further study.

  9. A case study of HF radar spectra and 630.0 nm auroral emission in the pre-midnight sector

    Directory of Open Access Journals (Sweden)

    M. Lester

    Full Text Available A comparison of HF radar backscatter observed by the CUTLASS Finland radar, meridian scanning photometer data from Longyearbyen, magnetic field variations from IMAGE stations, and particle precipitation measured by the DMSP F12 spacecraft is presented. The interval under discussion occurred in the pre-midnight local time sector, during a period of weakly northward interplanetary magnetic field. A region of HF backscatter, typically 8 degrees wide, occurred in the field of view of the CUTLASS Finland radar. A well defined gradient in the spectral width parameter was present, with mainly low (< 200 m s - 1 spectral widths in the lower latitude part of the scatter and predominantly large (> 200 ms - 1 spectral widths in the higher latitude part. The relationship between the spectral width and the red line (630.0 nm emission measured by the meridian scanning photometer is considered. The poleward border of the red line emission, which has, in the past, been proposed as being representative of the polar cap boundary, was co-located to within 1° of magnetic latitude with the gradient in spectral width for part of the interval. Statistically, large spectral widths occurred poleward of the red line emission, while small spectral widths occurred within or equatorward of the red line emission. Near simultaneous DMSP particle observations in the 20 eV to 20 keV range indicate that the poleward border of the red line emission and the gradient in spectral width occurred at the same latitude as the transition from auroral oval to polar rain particle energies. We conclude that the large spectral widths were not caused by particle precipitation associated with the auroral oval. There were two periods of special interest when the relationship between the red line and the spectral width broke down. The first of these happened during enhanced red line and green line (557.7 nm emission, with a drop out of the radar scatter and an enhanced, narrow westward

  10. ABNORMAL BONE OUTGROWTHS AND OSSEOUS STRUCTURES AROUND THE FORAMEN OVALE MAY LEADS TO MANDIBULAR COMPRESSION OR ENTRAPMENT NEUROPATHY

    OpenAIRE

    Kalyan Chakravarthi

    2013-01-01

    Foramina ovale is an important opening on the infratemporal surface of the posterior part of the greater wing of the sphenoid bone, any bone outgrowths and osseous structures around it could influence the anatomical organisation of the nerves and vessels that run through this opening. Accordingly the present study was designed to find out the bony outgrowths and osseous structures around the foramen ovale in available dried adult human skulls. The study was carried out using 100 dried adult h...

  11. Oxidative Stress and Oval Cell Accumulation in Mice and Humans with Alcoholic and Nonalcoholic Fatty Liver Disease

    OpenAIRE

    Roskams, Tania; Yang, Shi Qi; Koteish, Aymen; Durnez, Anne; DeVos, Rita; Huang, Xiawen; Achten, Ruth; Verslype, Chris; Diehl, Anna Mae

    2003-01-01

    In animals, the combination of oxidative liver damage and inhibited hepatocyte proliferation increases the numbers of hepatic progenitors (oval cells). We studied different murine models of fatty liver disease and patients with nonalcoholic fatty liver disease or alcoholic liver disease to determine whether oval cells increase in fatty livers and to clarify the mechanisms for this response. To varying degrees, all mouse models exhibit excessive hepatic mitochondrial production of H2O2, a know...

  12. Platypnea-orthodeoxia syndrome related to right hemidiaphragmatic elevation and a ‘stretched’ patent foramen ovale

    OpenAIRE

    Sakagianni, Katerina; Evrenoglou, Despina; Mytas, Dimitrios; Vavuranakis, Manolis

    2012-01-01

    Patent foramen ovale (PFO), although frequently observed in adults, rarely causes adverse clinical consequences. The most serious among them, are cryptogenic strokes and less commonly significant hypoxia resulting from right-to-left shunt (RLS). Platypnea-orthodeoxia syndrome referring to abnormal oxygenation in the upright position has been correlated with reopening of foramen ovale and acute right-to-left intracardiac shunt. We report a case of platypnea-orthodeoxia syndrome secondary to th...

  13. A Monte Carlo model of auroral hydrogen emission line profiles

    Directory of Open Access Journals (Sweden)

    J.-C. Gérard

    2005-06-01

    Full Text Available Hydrogen line profiles measured from space-borne or ground-based instruments provide useful information to study the physical processes occurring in the proton aurora and to estimate the proton flux characteristics. The line shape of the hydrogen lines is determined by the velocity distribution of H atoms along the line-of-sight of the instrument. Calculations of line profiles of auroral hydrogen emissions were obtained using a Monte Carlo kinetic model of proton precipitation into the auroral atmosphere. In this model both processes of energy degradation and scattering angle redistribution in momentum and charge transfer collisions of the high-energy proton/hydrogen flux with the ambient atmospheric gas are considered at the microphysical level. The model is based on measured cross sections and scattering angle distributions and on a stochastic interpretation of such collisions. Calculations show that collisional angular redistribution of the precipitating proton/hydrogen beam is the dominant process leading to the formation of extended wings and peak shifts in the hydrogen line profiles. All simulations produce a peak shift from the rest line wavelength decreasing with increasing proton energy. These model predictions are confirmed by analysis of ground-based H-β line observations from Poker Flat, showing an anti-correlation between the magnitude of the peak shift and the extent of the blue wing of the line. Our results also strongly suggest that the relative extension of the blue and red wings provides a much better indicator of the auroral proton characteristic energy than the position of the peak wavelength.

  14. Experimental study of plasma dynamics in the auroral ionosphere

    International Nuclear Information System (INIS)

    In March 1979, the third and fourth Porcupine sounding rockets were launched into auroral arcs from a launch site in northern Sweden. At the beginning of each flight two instrumented subpayloads, a xenon ion source, and a barium shaped charge were ejected from the main payload. This thesis covers measurements returned by the instrumented subpayloads of the electric fields, magnetic fields, plasma waves, and particle fluxes in the auroral arcs and during the operation of the xenon ion source. During the fourth flight, the subpayloads flew through the northern edge of an intense auroral arc. Two abrupt decreases in the precipitating electron energy and number flux were observed, and the precipitation boundaries were correlated with 20 to 60 mV/m increases in the ionospheric electric field and 0.1 to 0.2 A/m upward field aligned currents. The divergence of the electric field was calculated using simultaneous measurements by the two subpayloads and showed the expected build up of polarization charge at the precipitation boundaries. The direction and magnitude of the field aligned currents accompanying the electric field increases indicated that the magnetosphere was the source of the electric field perturbations and that the ionosphere was acting as a resistive load. Downward field aligned currents were observed adjacent to the regions of electron precipitation and may have been carried by ionospheric electrons moving up the magnetic field lines. These upward moving electrons may have drifted into the precipitation boundary and could have supplied the current necessary to maintain the observed electric field gradient

  15. Solar Array and Auroral Charging Studies of DMSP Spacecraft

    Science.gov (United States)

    Matias, Kelwin

    2013-01-01

    The SSJ electrostatic analyzers and the SSIES plasma instruments on the DMSP spacecraft in low Earth polar orbit can be used to conduct case studies of auroral and solar array charging. We will use a program written in the Interactive Data Language (IDL) to evaluate questionable charging events in the SSJ records by comparing charging signatures in SSJ and SSIES data. In addition, we will assemble a number of case studies of solar array charging showing the signatures from the SSJ data and compare to the SSIES charging signatures. In addition we will use Satellite Tool Kit (STK) to propagate orbits, obtain solar intensity, and use to verify onset of charging with sunrise.

  16. Ground and space observations of medium frequency auroral radio emissions

    Science.gov (United States)

    Broughton, Matthew C.

    The auroral zone is a rich source of natural radio emissions that can be observed in space and at ground-level. By studying these waves, scientists can gain insight into the plasma processes that generate them and use the near-Earth space environment as a large-scale plasma physics laboratory. This thesis uses both ground-level and in situ observations to study two kinds of natural radio emissions. First, we report observations of a new kind of auroral radio emission. The waves have frequencies ranging from 1.3-2.2 MHz, bandwidths ranging from 90-272 kHz, and durations ranging from 16-355 s. Spectral analysis of the waveform data has revealed that the emission has a complex combination of at least three kinds of fine structures. For model auroral electron distributions, calculations indicate that Langmuir waves could be excited at frequencies consistent with observations. The remainder of the thesis discusses auroral medium frequency (MF) burst, an impulsive, broadband natural radio emission observed at ground-level within a few minutes of local substorm onset. LaBelle [2011] proposed that MF burst originates as Langmuir/Z-mode waves on the topside of the ionosphere that subsequently mode convert to L-mode waves and propagate to ground-level. Using continuous waveform measurements and combined observations with the Sondrestrom Incoherent Scatter Radar, we have performed two tests of this mechanism. The results of these tests are consistent with the mechanism described in LaBelle [2011]. A survey of 8,624 half-orbits of the DEMETER spacecraft has revealed 68 observations of bursty MF waves. We have compared the wave properties of these waves to those of MF burst and have found that although it is uncertain, the balance of the evidence suggests that the bursty MF waves observed with DEMETER are the same phenomenon as the ground-level MF burst. Finally, we have used numerical simulations to model both the fine structure of MF burst and to estimate the attenuation the

  17. Auroral phenomenology and magnetospheric processes earth and other planets

    CERN Document Server

    Keiling, Andreas; Bagenal, Fran; Karlsson, Tomas

    2013-01-01

    Published by the American Geophysical Union as part of the Geophysical Monograph Series. Many of the most basic aspects of the aurora remain unexplained. While in the past terrestrial and planetary auroras have been largely treated in separate books, Auroral Phenomenology and Magnetospheric Processes: Earth and Other Planets takes a holistic approach, treating the aurora as a fundamental process and discussing the phenomenology, physics, and relationship with the respective planetary magnetospheres in one volume. While there are some behaviors common in auroras of the diffe

  18. Investigating the auroral electrojets with low altitude polar orbiting satellites

    DEFF Research Database (Denmark)

    Moretto, T.; Olsen, Nils; Ritter, P.; Lu, G.

    2002-01-01

    Three geomagnetic satellite missions currently provide high precision magnetic field measurements from low altitude polar orbiting spacecraft. We demonstrate how these data can be used to determine the intensity and location of the horizontal currents that flow in the ionosphere, predominantly in...... the auroral electrojets. First, we examine the results during a recent geomagnetic storm. The currents derived from two satellites at different altitudes are in very good agreement, which verifies good stability of the method. Further, a very high degree of correlation (correlation coefficients of 0...

  19. Multi-Spacecraft Observations of the Auroral Acceleration Region

    OpenAIRE

    Sadeghi, Soheil

    2012-01-01

    The two major agents for producing aurora are generally believed to be the quasi-static parallel electric fields, accelerating electrons in the auroral acceleration region (AAR), and Alfvén waves. The Cluster spacecraft quartet has made multi-spacecraft measurements in the AAR possible for the first time. Four event studies are included and discussed in this thesis, using Cluster data inside and at the top of the AAR, to address various open issues regarding the nature of the quasistatic elec...

  20. Daytime measurements of optical auroral emissions from Antarctica

    International Nuclear Information System (INIS)

    Optical methods have enabled to detect auroral emissions during daytime conditions, and to identify a narrow latitudinal region of energetic particle precipitation from the Indian station Maitri (11 deg38'E; 70deg45'S; 62.8degS I-lat.) in Antarctica. These observations are new. The energetic particles originate within the closed geomagnetic field lines close to the plasmapause region and maximize ∼ 0830 h MLT (magnetic local time) (∼1200 UT). Enhanced proton precipitation activity could also be inferred during a moderate geomagnetic storm, suggesting the enhancement/activation of acceleration mechanisms during this event. (author). 11 refs., 2 figs

  1. Investigating the auroral electrojets with low altitude polar orbiting satellites

    DEFF Research Database (Denmark)

    Moretto, T.; Olsen, Nils; Ritter, P.;

    2002-01-01

    in the auroral electrojets. First, we examine the results during a recent geomagnetic storm. The currents derived from two satellites at different altitudes are in very good agreement, which verifies good stability of the method. Further, a very high degree of correlation (correlation coefficients of 0...... to another event for which the combined measurements of the three satellites provide a comprehensive view of the current systems. The analysis hereof reveals some surprising results concerning the connection between solar wind driver and the resulting ionospheric currents. Specifically, preconditioning...

  2. Modulation of stable auroral red (SAR) arc occurrence rates

    International Nuclear Information System (INIS)

    Data taken by the Pacific Northwest Laboratory photometer chain have been reviewed in a comprehensive search for stable auroral red (SAR) arc events during the period 1968--1978. Results of this search indicate both a seasonal and solar cycle control of SAR arclike events. The occurrence rate of these events is shown to follow the solar activity cycle. though with a phase lag of 2--3 years. Further, a rather distinct summertime minimum of occurrence frequency is pointed out (northern hemisphere). Possible mechanisms for the existence of this effect are discussed

  3. Magnetosphere-ionosphere coupling currents in Jupiter's middle magnetosphere: effect of magnetosphere-ionosphere decoupling by field-aligned auroral voltages

    Directory of Open Access Journals (Sweden)

    J. D. Nichols

    2005-03-01

    Full Text Available We consider the effect of field-aligned voltages on the magnetosphere-ionosphere coupling current system associated with the breakdown of rigid corotation of equatorial plasma in Jupiter's middle magnetosphere. Previous analyses have assumed perfect mapping of the electric field and flow along equipotential field lines between the equatorial plane and the ionosphere, whereas it has been shown that substantial field-aligned voltages must exist to drive the field-aligned currents associated with the main auroral oval. The effect of these field-aligned voltages is to decouple the flow of the equatorial and ionospheric plasma, such that their angular velocities are in general different from each other. In this paper we self-consistently include the field-aligned voltages in computing the plasma flows and currents in the system. A third order differential equation is derived for the ionospheric plasma angular velocity, and a power series solution obtained which reduces to previous solutions in the limit that the field-aligned voltage is small. Results are obtained to second order in the power series, and are compared to the original zeroth order results with no parallel voltage. We find that for system parameters appropriate to Jupiter the effect of the field-aligned voltages on the solutions is small, thus validating the results of previously-published analyses.

  4. Shift of the auroral electron precipitation boundaries in the dawn-dusk sector in association with geomagnetic activity and interplanetary magnetic field

    International Nuclear Information System (INIS)

    On the basis of the auroral precipitating electron data along the dawn-dusk meridian from a Defense Meteorological Satellite Program satellite (DMSP-F2), we show that the electron precipitation region extends poleward, often to the geomagnetic latitudes > or approx. =850 from the average oval location, during quiet periods (namely, during periods of a large positive B/sub z/ component). This result may be interpreted as an indication that only a small amount of geomagnetic flux interconnects with the northward IMF, resulting in a contracted ''open'' region (the polar cap). The control of the location of the poleward boundary by the north-south component of the IMF is also statistically examined. The rate of latitudinal movement is about 0.40 to 0.80 per 1 nT for positive IMF B/sub z/ values and about 0.70 to 1.10D per 1 nT for negative IMF B/sub z/ values. The shift of the equatorward boundary is not obvious, however, for positive IMF B/sub z/ values. As geomagnetic activity increases, both the poleward and equatorward boundaries shift toward lower latitudes. The equatorward shift of the poleward and equatorward boundaries is greater than that of the equatorward boundary, resulting in a thinner electron precipitation region during disturbed periods than during quiet periods

  5. Recurrent thromboembolic events after percutaneous device closure of patent foramen ovale.

    Science.gov (United States)

    Börgermann, Jochen; Hakim, Kavous; Friedrich, Ivar; Diez, Claudius

    2003-06-01

    We report on a 34-year-old male with recurrent transient ischemic attacks 1 year after transcatheter closure of a patent foramen ovale. Echocardiography demonstrated thrombus attached to the device, although the patient had been anticoagulated with phenprocoumon. There was no residual shunt. Computed tomography and transcranial Doppler ultrasonography showed no evidence of a new stroke. The thrombosed device was removed under cardiopulmonary bypass and the defect was closed with a pericardial patch. The patient was discharged home and has been well for almost 2 years. At this time, there is no evidence for any new neurological events. PMID:17670007

  6. Isolated brain metastases of osteosarcoma in a patient presenting with a patent foramen ovale

    International Nuclear Information System (INIS)

    We report the case of a patient in whom brain MR imaging was requested for initial symptoms of intracranial hypertension. The presence of multiple intracranial hemorrhagic lesions suggested brain metastases. Body screening showed periosteal osteosarcoma of the left fibula with no lung metastases, but with a patent foramen ovale which probably allowed neoplastic cells to reach the brain without being filtered through the lungs. The conclusion of this study was that a left-right cardiac communication is to be considered in cases of isolated brain metastases from osteosarcoma. (orig.). With 3 figs

  7. [Perioperative Challenges and Strategies for Patent Foramen Ovale Patients Undergoing Non-cardiac Surgery].

    Science.gov (United States)

    Wang, Tian; Zhu, Bin

    2015-08-01

    The close relationship between patent foramen ovale(PFO)and cryptogenic ischemic cerebrovascular disease and migraine has been concerned for years. However,in the field of non-cardiac surgery and anesthesiology, PFO and related clinical problems are less recognized. Under perioperative circumstances,PFO may generate many challenges such as paradoxical systematic embolism and severe hypoxemia. This article briefly introduces the epidemiology, paradoxical embolism, and detection methods of PFO and discribes the perioperative complications and corresponding perioperative strategies for prevention and cure. PMID:26564467

  8. Auroral E-region electron density gradients measured

    Directory of Open Access Journals (Sweden)

    G. Hussey

    Full Text Available In the theory of E-region plasma instabilities, the ambient electric field and electron density gradient are both included in the same dispersion relation as the key parameters that provide the energy for the generation and growth of electrostatic plasma waves. While there exist numerous measurements of ionospheric electric fields, there are very few measurements and limited knowledge about the ambient electron density gradients, ∇Ne, in the E-region plasma. In this work, we took advantage of the EISCAT CP1 data base and studied statistically the vertical electron density gradient length, Lz=Ne/(dNe/dz, at auroral E-region heights during both eastward and westward electrojet conditions and different ambient electric field levels. Overall, the prevailing electron density gradients, with Lz ranging from 4 to 7 km, are found to be located below 100 km, but to move steadily up in altitude as the electric field level increases. The steepest density gradients, with Lz possibly less than 3 km, occur near 110 km mostly in the eastward electrojet during times of strong electric fields. The results and their implications are examined and discussed in the frame of the linear gradient drift instability theory. Finally, it would be interesting to test the implications of the present results with a vertical radar interferometer.Key words: Ionosphere (auroral ionosphere; ionospheric irregularities; plasma waves and instabilities  

  9. Auroral X ray emission at Jupiter: Depth effects

    International Nuclear Information System (INIS)

    Auroral X-ray emissions from Jupiter with a total power of about 1 GW have been observed by the Einstein Observatory, Roentgen satellite, Chandra X-ray Observatory, and XMM-Newton. Previous theoretical studies have shown that precipitating energetic sulfur and oxygen ions can produce the observed X-rays. This study presents the results of a hybrid Monte Carlo (MC) model for sulfur and oxygen ion precipitation at high latitudes, looks at differences with the continuous slow-down model, and compares the results to synthetic spectra fitted to observations. We concentrate on the effects of altitude on the observed spectrum. The opacity of the atmosphere to the outgoing X-ray photons is found to be important for incident ion energies greater than about 1.2 MeV per nucleon for both sulfur and oxygen. Model spectra are calculated for intensities with and without any opacity effects. These synthetic spectra were compared with the results shown by Hui et al. (2010) which fit Chandra X-ray Observatory observations for the north and south Jovian auroral emissions. Quenching of long-lived excited states of the oxygen ions is found to be important. Opacity considerably diminishes the outgoing X-ray intensity calculated, particularly when the viewing geometry is not favorable.

  10. Insulin-like growth factor binding protein-3 is required for the regulation of rat oval cell proliferation and differentiation in the 2AAF/PHX model

    OpenAIRE

    Steiger-Luther, Nicole C; Darwiche, Houda; Oh, Seh-Hoon; Williams, Jennifer M.; PETERSEN, BRYON E.

    2010-01-01

    Oval cell-mediated liver regeneration is a highly complex process that involves the coordination of several signaling factors, chemokines and cytokines to allow for proper maintenance of the liver architecture. When hepatocyte proliferation is inhibited, an hepatic stem cell population, often referred to as “oval cells”, is activated to aid in liver regeneration. The function of insulin-like growth factor binding protein-3 (IGFBP-3) during this process of oval cell activation is of particular...

  11. 12-hour case study of auroral phenomena in the midnight sector: Electrojet and precipitating particle characteristics

    International Nuclear Information System (INIS)

    Airborne observations of auroral activity at midnight were conducted for a period of 9 hours by employing an ionospheric sounder and all-sky cameras. During the observation period, two substorms occurred. The first substorm was assciated with a compression of the magnetosphere (as measured by Dst) and with oscillations of the earth's bow shock. At this time, auroral activity was characterized by a series of poleward and equatorward motions and by the absence of a breakup phase. Magnetic disturbances were confined to a small region in the midnight sector. The second auroral substorm displayed many of the features assocated with a large-scale polar magnetic substorm. For selected times the locations of the eastward and westward electrojets were inferred from a number of high-latitude magnetic records. All-sky photographs and ionosonde data indicate that the poleward edge of the westward electrojet was bounded by a westward moving auroral surge accompanied by a strong sporadic E ionization. The equatorward electrojet boundary was less well defined by visual auroral forms. Soft particle spectrometer measurements from the Isis 2 satellite were made in conjunction with the aircraft measurements and indicate that large fluxes of field-aligned electrons gave rise to the bright auroral surge, more isotropic fluxes of less energetic electrons contributing to the auroral E layer

  12. Influence of the ionosphere on the altitude of discrete auroral arcs

    Directory of Open Access Journals (Sweden)

    C. S. Deehr

    2005-03-01

    Full Text Available The altitude of the maximum luminosity of single, discrete auroral arcs was measured by photometric triangulation from two stations (College and Fort Yukon, Alaska located 226km apart on nearly the same magnetic meridian. The average height of the evening aurora decreases smoothly with increasing solar depression angle (sda from 160km near 12° sda to 100km after 18° sda. The average height remains constant until around 12° sda in the morning. This diurnal variation is similar to that of the electron density in the F region of the ionosphere. Thus, the behavior is consistent with the concept that the mean auroral electron energy increases as the ionospheric conductivity decreases due to ionospheric recombination in the evening twilight. However, the mean electron energy decreases in magnitude at dawn when the solar ionizing radiation returns and the electron density in the F region increases. The magnetospheric acceleration mechanism associated with discrete auroral arcs thus appears to be inversely proportional to the ionospheric conductivity, because the time variation of the acceleration mechanism coincides with the local F region electron density and not with any obvious magnetospheric process. Previous auroral altitude observations, using similar triangulation methods, showed that the altitude of discrete auroral arcs increases as a function of latitude. When these data are corrected for the twilight effect, the dependence of altitude on latitude disappears. Thus, the average altitude of discrete auroral arcs and, by inference the magnetospheric auroral electron acceleration mechanism, is significantly influenced by the initial ionospheric conductance.

  13. The effect of multiple scattering on the aspect sensitivity and polarization of radio auroral echoes

    International Nuclear Information System (INIS)

    A Monte Carlo model of radio wave scattering in the auroral electrojet has been developed to investigate multiple scattering of radio auroral echoes. Using this model, predictions of the aspect angle behavior of first-, second-, and third-order scattered power have been made. The results indicate that multiple scattering may be an important effect for VHF radars which observe the auroral E region at large magnetic aspect angles. The model shows that linearly polarized radio waves can become depolarized because of multiple scattering if the radio transmitter is horizontally polarized but not if the radio transmitter is vertically polarized. 52 refs

  14. Coordinated rocket and satellite measurements of an auroral event. I - Satellite observations and analysis

    Science.gov (United States)

    Rees, M. H.; Stewart, A. I.; Sharp, W. E.; Hays, P. B.; Hoffman, R. A.; Brace, L. H.; Doering, J. P.; Peterson, W. K.

    1977-01-01

    Results of a coordinated auroral experiment involving the Atmosphere Explorer C satellite and a sounding rocket are reported. Auroral primary electron fluxes and neutral gas densities measured by instruments on the satellite are used in a model calculation of the thermospheric manifestation of the aurora. There is encouraging agreement between the calculated and measured electron density, electron temperature, secondary electron flux, and O I emissions at 5577 and 6300 A. A discrepancy between the calculated and the rocket-measured 3914-A emission profile is discussed in terms of experiment geometry and auroral physics. The coordinated measurements are used to infer vertical fluxes of ionization and of electron thermal energy at high altitudes

  15. Lessons from Hepatocyte-Specific Cyp51 Knockout Mice: Impaired Cholesterol Synthesis Leads to Oval Cell-Driven Liver Injury

    Science.gov (United States)

    Lorbek, Gregor; Perše, Martina; Jeruc, Jera; Juvan, Peter; Gutierrez-Mariscal, Francisco M.; Lewinska, Monika; Gebhardt, Rolf; Keber, Rok; Horvat, Simon; Björkhem, Ingemar; Rozman, Damjana

    2015-03-01

    We demonstrate unequivocally that defective cholesterol synthesis is an independent determinant of liver inflammation and fibrosis. We prepared a mouse hepatocyte-specific knockout (LKO) of lanosterol 14α-demethylase (CYP51) from the part of cholesterol synthesis that is already committed to cholesterol. LKO mice developed hepatomegaly with oval cell proliferation, fibrosis and inflammation, but without steatosis. The key trigger was reduced cholesterol esters that provoked cell cycle arrest, senescence-associated secretory phenotype and ultimately the oval cell response, while elevated CYP51 substrates promoted the integrated stress response. In spite of the oval cell-driven fibrosis being histologically similar in both sexes, data indicates a female-biased down-regulation of primary metabolism pathways and a stronger immune response in males. Liver injury was ameliorated by dietary fats predominantly in females, whereas dietary cholesterol rectified fibrosis in both sexes. Our data place defective cholesterol synthesis as a focus of sex-dependent liver pathologies.

  16. Stress assessment based on ovality and thickness asymmetry for an internally pressurized pipe elbow at high temperature

    International Nuclear Information System (INIS)

    In this paper the material creep behavior and multiaxial stress state of high temperature pipe elbow were investigated. The stress distribution in the pipe elbow during creep is discussed. The maximum stress area of pipe elbow transfers from inner wall to outer wall during creep. The ovality and the different initial thickness asymmetry of steam pipe elbows subjected to a uniform internal pressure at high temperature are calculated with Finite Element Analysis (FEA). The initial ovality and wall-thickness play a very large role in stress distribution in the elbows, and vary with time during creep. That explains the transfer of stress distribution in the elbows. Based on influence of ovality and thickness an analytical model to calculate equivalent stress of elbow through straight pipe stress is presented. (authors)

  17. Remarkable heterogeneity displayed by oval cells in rat and mouse models of stem cell-mediated liver regeneration

    DEFF Research Database (Denmark)

    Jelnes, Peter; Santoni-Rugiu, Eric; Rasmussen, Morten;

    2007-01-01

    The experimental protocols used in the investigation of stem cell-mediated liver regeneration in rodents are characterized by activation of the hepatic stem cell compartment in the canals of Hering followed by transit amplification of oval cells and their subsequent differentiation along hepatic...... the molecular phenotypes of oval cells in several of the most commonly used protocols of stem cell-mediated liver regeneration-namely, treatment with 2-acetylaminofluorene and partial (70%) hepatectomy (AAF/PHx); a choline-deficient, ethionine-supplemented (CDE) diet; a 3,5-diethoxycarbonyl-1...... results delineate remarkable phenotypic discrepancies exhibited by oval cells in stem cell-mediated liver regeneration between rats and mice and underline the importance of careful extrapolation between individual species....

  18. Dual effects of adenovirus-mediated thrombopoietin gene transfer on hepatic oval cell proliferation and platelet counts

    International Nuclear Information System (INIS)

    Thrombopoietin (TPO) is the growth factor for megakaryocytes and platelets, however, it also acts as a potent regulator of stem cell proliferation. To examine the significance of TPO expression in proliferation of hepatic oval cells, the effect of adenovirus-mediated TPO gene transfer into livers of the Solt-Farber model, which mimics the condition where liver regeneration is impaired, was examined. Hepatic TPO mRNA peaked its expression at 2 days after gene transduction and then gradually decreased. The peripheral platelet number began to increase at 4 days (P < 0.05) and reached its plateau at 9 days (P < 0.01). Oval cells expressed c-Mpl, a receptor for TPO as well as immature hematopoietic and hepatocytic surface markers such as CD34 and AFP. The proliferating cell nuclear antigen-positive oval cells in rats into which adenovirus-TPO gene was transferred at 7 and 9 days were significantly greater than those in adenovirus-LacZ gene transferred (P < 0.05, each), and the total numbers of oval cells in the adenovirus-TPO gene transferred at 9 and 13 days were also significantly greater than those in adenovirus-LacZ gene transferred (P < 0.05, each). Expression of SCF protein was increased at 4, 7, and 9 days by TPO gene administration and that of c-Kit was increased at 4 and 7 days. These data suggest that adenovirus-mediated TPO gene transfer stimulated oval cell proliferation in liver as well as increasing peripheral platelet counts, emphasizing the significance of the TPO/c-Mpl system in proliferation of hepatic oval cells

  19. A mobilidade do Septum primum não depende do diâmetro do forame oval em fetos normais Mobility of the Septum primum does not depend on the foramen ovale diameter in normal fetuses

    Directory of Open Access Journals (Sweden)

    Paulo Zielinsky

    2004-10-01

    Full Text Available OBJETIVO: Testar a hipótese de que existe correlação entre o diâmetro máximo diastólico do forame oval e o índice de excursão do septum primum em fetos normais. MÉTODOS: Foram examinados, por ecocardiografia, 102 fetos normais de gestantes com idades gestacionais entre 20 e 40 semanas. O diâmetro do forame oval e a excursão máxima do septum primum foram medidos num corte de 4 câmaras. Na análise dos dados utilizou-se o coeficiente de correlação de Pearson. RESULTADOS: A média do forame oval foi de 5,06 ± 1,29 mm; a da excursão máxima do septum primum de 5,42 ± 1,41 mm; a do átrio esquerdo 11,47 ± 2,76 mm e a do índice de excursão 0,48 ± 0,09. A relação média FO/IE foi de 11,35 ± 3,94 mm. Não houve correlação FO/IE (r = -0,03 e observou-se correlação fraca do forame oval com o átrio esquerdo (r = 0,031 e com a excursão do septum primum (r = 0,21. CONCLUSÃO: A mobilidade do septum primum não depende do diâmetro do forame oval em fetos normais, sugerindo que as modificações da sua excursão diastólica não decorram do grau de abertura interatrial.OBJECTIVE: To test the hypothesis that a correlation exists between the maximum foramen ovale diastolic diameter and the excursion index (EI of the septum primum in normal fetuses. METHODS: One hundred and two normal fetuses with gestational ages ranging from 20 to 40 weeks were submitted to echocardiography. The foramen ovale diameter and the "maximal excursion" of the septum primum were measured in a 4-chamber view. The data were analyzed by Pearson's correlation coefficient. RESULTS: The mean foramen ovale (FO diameter was 5.06 ± 1.29 mm; the maximal excursion of the septum primum was 5.42 ± 1.41 mm; the left atrium diameter 11.47 ± 2.76 mm; the septum primum "excursion index" was 0.48 ± 0.09. Mean FO/EI ratio was 11.35 ± 3.94 mm. No FO/EI correlation (r = -0.03 existed, and a weak foramen ovale/left atrium correlation (r = 0.31 was observed, as well as a

  20. Simultaneous auroral observations described in the historical records of China, Japan and Korea from ancient times to AD 1700

    Directory of Open Access Journals (Sweden)

    D. M. Willis

    Full Text Available Early auroral observations recorded in various oriental histories are examined in order to search for examples of strictly simultaneous and indisputably independent observations of the aurora borealis from spatially separated sites in East Asia. In the period up to ad 1700, only five examples have been found of two or more oriental auroral observations from separate sites on the same night. These occurred during the nights of ad 1101 January 31, ad 1138 October 6, ad 1363 July 30, ad 1582 March 8 and ad 1653 March 2. The independent historical evidence describing observations of mid-latitude auroral displays at more than one site in East Asia on the same night provides virtually incontrovertible proof that auroral displays actually occurred on these five special occasions. This conclusion is corroborated by the good level of agreement between the detailed auroral descriptions recorded in the different oriental histories, which furnish essentially compatible information on both the colour (or colours of each auroral display and its approximate position in the sky. In addition, the occurrence of auroral displays in Europe within two days of auroral displays in East Asia, on two (possibly three out of these five special occasions, suggests that a substantial number of the mid-latitude auroral displays recorded in the oriental histories are associated with intense geomagnetic storms.

    Key words. Magnetospheric physics (auroral phenomena; storms and substorms

  1. Auroral ion precipitation at Jupiter: Predictions for Juno

    Science.gov (United States)

    Ozak, N.; Cravens, T. E.; Schultz, D. R.

    2013-08-01

    The spatially localized and highly variable polar cap emissions at Jupiter are part of a poorly understood current system linking the ionosphere and the magnetopause region. Strong X-ray emission has been observed from the polar caps and has been explained by the precipitation of oxygen and sulfur ions of several MeV energy. The present paper presents results of an extended model of the ion precipitation process at Jupiter. Specifically, we add to a previous model a more complete treatment of ionization of the atmosphere, generation of secondary electron fluxes and their escape from the atmosphere, and generation of downward field-aligned currents. Predictions relevant to observations by the upcoming NASA Juno mission are made, namely the existence of escaping electrons with energies from a few eV up to 10 keV, auroral H2 band emission rates of 80 kR, and downward field-aligned currents of at least 2 MA.

  2. Measuring auroral precipitation parameters without in situ microchannel plate instrumentation

    Science.gov (United States)

    Lynch, K. A.; Hampton, D. L.; Zettergren, M. D.; Conde, M.; Lessard, M.; Michell, R.; Samara, M.

    2013-12-01

    Recent advances in groundbased detector technology have resulted in accurate, high-sensitivity, emission-line filtered images of aurora with sub- to a few- km resolution over a few 100 km region collected at a few second to a few Hz cadence. By combining these images with information from other groundbased instrumentation (ISR, remote photometers, and FPIs) and using well-documented empirical relationships between intensity and precipitating electron characteristics, these images hold the potential for providing an accurate, mesoscale, 2-D time history of the key parameters (characteristic energy and energy flux) of the precipitating electrons that caused the optical aurora within the imager's field of view. In situ measurements can be more accurate, but they are limited to highly localized 1-D line trajectories and are of limited use for meso-scale modeling. However, a limitation of the groundbased technique is that subvisual (low energy) precipitation is not captured. Onboard measurements of total number flux provide low resource measurements capturing specific boundary crossings and gradients as well as net precipitation including the portion not observed optically. The combination of minimal onboard instrumentation supplementing rigorous groundbased inversions can provide an optimal set of inputs for ionospheric modelling tools. Thus we are investigating the capabilities and limitations of using inversions of groundbased observations in the place of in situ precipitation monitors. While several inversion techniques are possible we will discuss two methods used in the analysis of recent rocket experiments. The first, used for the Cascades2 rocket, compares measured altitude profiles of auroral emissions to those from a 1-D electron transport code to confirm optically that two arcs transited by the rocket were produced by significantly different electron spectra. The second method, for the MICA rocket, uses the 2-D temperature maps from the Scanning Doppler

  3. Fluctuations of precipitated electron intensity in flickering auroral arcs

    International Nuclear Information System (INIS)

    This paper reports on electron spectra associated with two aurorae observed by ground-based television. One auroral arc was observed to flicker, large variations in the precipitated electron energy occurring on a time scale of 114 ms. The major variations occur at the higher energies of the 0.5--20 keV range covered by the detectors. Changes in the particle flux occur primarily in the pitch angle range 00 to 600. Analysis of the video data shows a larger variation in intensity along the lower border of the arc in keeping with the results of the electron spectra. The second arc was not observed to flicker, and the associated electron spectra and video data show no large variations in precipitated electron energy or video intensity modulation. While pitch angle distributions tend to be field-aligned in the first arc, the distributions in the second arc are nearly isotropic or peaked from 600 to 900 in the downward hemisphere

  4. Field line projections of 6300 AA auroral emissions into the outer magnetosphere

    International Nuclear Information System (INIS)

    An empirical magnetospheric model is employed to project auroral intensity boundaries into the magnetosphere. The auroral data are in the form of instantaneous maps of 6300AA emission, acquired with the ISIS-II spacecraft and correspond to fluxes of low energy electrons. These are specific to a particular universal time and date. The magnetospheric model used is a purely empirical one, designed by Mead and Fairfield (1975) from 44.76 x 106 magnetic measurements made by 4 IMP satellites. Their model includes the dipole tilt as a variable, and permits selection from four different disturbance levels, so is particularly suited to these data. In a general way, the auroral projections agree with what is expected, giving some confidence in this application of the model. But a number of features appear that were not predicted, and which should permit new insights into the relationship of specific auroral boundaries to the structure of the magnetosphere. (author)

  5. Wave-particle interaction in the auroral ionosphere in LF and HF range

    International Nuclear Information System (INIS)

    Plasma wave observations using the sounding rockets, S-310JA-11 and S-310JA-12 have disclosed the following new aspects of wave-particle interaction processes in the auroral ionosphere: 1) generation of intense Z-mode waves by auroral particles through the inverse Landau damping, 2) confirmation of the leaked components of auroral kilometric radiation, and 3) detection of naturally generated electrostatic electron cyclotron harmonic (ESCH) waves in the frequency range lower than the local electron cyclotron frequency. It is pointed out that Z-mode waves in the auroral region have a very important role because the waves are easily generated being coupled with the particle precipitation. The leaked component of AKR is an important manifestation of the mode conversion processes. The generation of ESCH waves are associated with the nonlinear wave-particle interaction. The newly detected ESCH wave phenomena correspond to n = 0 case of the fDn emissions. (author)

  6. M and X Class Flares During 2011 to 2013 and their Connection to Auroral Electrojet Indices

    Directory of Open Access Journals (Sweden)

    Debojyoti Halder

    2014-07-01

    Full Text Available Solar bursts recorded in the frequency range 50 to 300 MHz by using log periodic dipole array over Kalyani (22°58´N, 88°46´E have been statistically analyzed for the years 2011-2013. Scatter plots of flare intensity for both M- and X-class flares as well as the number of occurrences of the two categories have been examined. The characteristics of the auroral electrojet indices are correlated directly to the solar flare activity. The auroral indices data obtained from various sources are sorted accordingly. The daily averaged data of the auroral indices are plotted for a period of 5 years, 2009 to 2013. Regression analysis of the indices data has been done meticulously. The regression analysis data are also plotted as residual plots and line fit plots. We have tried to discuss the possible connection between the occurrences of solar flares and the auroral electrojet indices

  7. Relationship between Alfvén Wave and Quasi-Static Acceleration in Earth's Auroral Zone

    Science.gov (United States)

    Mottez, Fabrice

    2016-02-01

    There are two main categories of acceleration processes in the Earth's auroral zone: those based on quasi-static structures, and those based on Alfvén wave (AW). AWs play a nonnegligible role in the global energy budget of the plasma surrounding the Earth because they participate in auroral acceleration, and because auroral acceleration conveys a large portion of the energy flux across the magnetosphere. Acceleration events by double layers (DLs) and by AW have mostly been investigated separately, but many studies cited in this chapter show that they are not independent: these processes can occur simultaneously, and one process can be the cause of the other. The quasi-simultaneous occurrences of acceleration by AW and by quasi-static structures have been observed predominantly at the polar cap boundary of auroral arc systems, where often new bright arcs develop or intensify.

  8. Identification of possible intense historical geomagnetic storms using combined sunspot and auroral observations from East Asia

    Directory of Open Access Journals (Sweden)

    D. M. Willis

    2005-03-01

    Full Text Available Comprehensive catalogues of ancient sunspot and auroral observations from East Asia are used to identify possible intense historical geomagnetic storms in the interval 210 BC-AD 1918. There are about 270 entries in the sunspot catalogue and about 1150 entries in the auroral catalogue. Special databases have been constructed in which the scientific information in these two catalogues is placed in specified fields. For the purposes of this study, an historical geomagnetic storm is defined in terms of an auroral observation that is apparently associated with a particular sunspot observation, in the sense that the auroral observation occurred within several days of the sunspot observation. More precisely, a selection criterion is formulated for the automatic identification of such geomagnetic storms, using the oriental records stored in the sunspot and auroral databases. The selection criterion is based on specific assumptions about the duration of sunspot visibility with the unaided eye, the likely range of heliographic longitudes of an energetic solar feature, and the likely range of transit times for ejected solar plasma to travel from the Sun to the Earth. This selection criterion results in the identification of nineteen putative historical geomagnetic storms, although two of these storms are spurious in the sense that there are two examples of a single sunspot observation being associated with two different auroral observations separated by more than half a (synodic solar rotation period. The literary and scientific reliabilities of the East Asian sunspot and auroral records that define the nineteen historical geomagnetic storms are discussed in detail in a set of appendices. A possible time sequence of events is presented for each geomagnetic storm, including possible dates for both the central meridian passage of the sunspot and the occurrence of the energetic solar feature, as well as likely transit times for the ejected solar plasma

  9. Effects of Geomagnetic Disturbances on Offshore Magnetic Directional Wellbore Positioning in the Northern Auroral Zone

    OpenAIRE

    Edvardsen, Inge

    2016-01-01

    This thesis focuses on how disturbances in the geomagnetic field, offshore northern Norway, may affect the accuracy of magnetic directional wellbore surveying. The topics discussed are, however, applicable to the entire northern auroral zone. Suggestions on how to manage the effect of increased geomagnetic activity on magnetic directional wellbore survey operations in and near the auroral zone are described. The results from our study of the geomagnetic conditions in the Norwegian Sea ...

  10. Auroral electrojets during deep solar minimum at the end of solar cycle 23

    OpenAIRE

    Pulkkinen, Tuija I.; Tanskanen, E. I.; Viljanen, A.; N. Partamies; Kauristie, K.

    2011-01-01

    We investigate the auroral electrojet activity during the deep minimum at the end of solar cycle 23 (2008–2009) by comparing data from the IMAGE magnetometer chain, auroral observations in Fennoscandia and Svalbard, and solar wind and interplanetary magnetic field (IMF) observations from the OMNI database from that period with those recorded one solar cycle earlier. We examine the eastward and westward electrojets and the midnight sector separately. The electrojets during 2008–2009 were found...

  11. Deducing composition and incident electron spectra from ground-based auroral optical measurements: A study of auroral red line processes

    International Nuclear Information System (INIS)

    We conclude from a study of the production and loss of O(1D) in auroras that the ''traditional'' sources, direct electron impact excitation of atomic oxygen and dissociative recombination of molecular oxygen ions, can account for most of the O I 6300-A emission rate. In a specific application of the model to the comprehensive observation of an auroral event by Sharp et al. (1979), we show that there is no compelling need for the reaction N(2D)+O2→NO+O(1D). We also present a study of the sensitivity of the red line emission rate to a wide variety of input conditions. copyright American Geophysical Union 1989

  12. Tromboembolismo pulmonar masivo de alto riesgo asociado a foramen oval permeable

    Directory of Open Access Journals (Sweden)

    Antonio Miranda

    2012-04-01

    Full Text Available La alta mortalidad de los pacientes con tromboembolismo pulmonar masivo de alto riesgo amerita un enfoque terapéutico enérgico e invasivo que incluya la embolectomía pulmonar quirúrgica en aquellos pacientes con contraindicación para trombolisis o trombolisis fallida. Describimos un caso de tromboembolismo pulmonar masivo de alto riesgo que recibió tratamiento quirúrgico en vez de trombolisis debido a que al momento del diagnóstico presentaba un trombo móvil a través de un foramen oval permeable con altísima posibilidad de embolismo paradójico arterial.

  13. Efficacy and safety of percutaneous transvenous mitral commisurotomy (PTMC) performed through patent foramen ovale (PFO)

    International Nuclear Information System (INIS)

    Methodology: The aim of this study was to assess efficacy and safety of PTMC in patients with severe eitral stenosis (MS) perform throqgh patent foraman ovale. Methodology: All symptomatic patients with severe MS were included in the study from January 1998 to Decembeb 2010, at Cardiology department, Lady Readijg Hospital, Peshawar. Transthoracic and trans-esophageal echocardiogram was pdrformed to excLude left atrial appendage/left atrial clot and check pha anatomy of interatrial septum. Severely aalcified mitral valve and severe -Itral regurgitation were exaluded. Patent fnramen o6ala was cro3sed in majority of cases to reach left atriui. Stenosed mitral valve was dilated with Inoue balloon. Results: Total number of patients was 1818. Females were 74% (p0.05). Stroke was present in 1.5% patientr. Conclusion: PTMC through is a safe procedure, with few complications. (author)

  14. Pulmonary embolism and patent foramen ovale thrombosis: the key role of TEE

    Directory of Open Access Journals (Sweden)

    Reverberi Claudio

    2007-08-01

    Full Text Available Abstract This is a case report of a 35 young man with Klinefelter Syndrome presented breathlessness, palpitations and chest pain. It shows a rare case of a thrombus located through the PFO, in patient with pulmonary and paradoxical embolism, which takes back to exciting hypothesis on thrombus growth. A thrombus, which has grown 'in situ' or trapped through the patent foramen ovale, may be a cause of relapsing pulmonary or systemic embolism during anticoagulation therapy. To prevent recurrent paradoxical embolism, percutaneous closure of PFO is recommended, but in this case, thrombus was trapped through the PFO and the patient was referred to the surgeon. We believe that under these circumstances the clinician should be informed of the presence of PFO in critical pulmonary embolism; this case points out the key role of TEE to face a diagnostic and therapeutic scenarios.

  15. Transient Ischemic Attack After Foam Sclerotherapy in a Woman With a Patent Foramen Ovale.

    Science.gov (United States)

    Kim, Michael; Niroumandpour, Mehrdad; Poustinchian, Brian

    2016-05-01

    Sclerotherapy is an increasingly popular treatment modality for patients with chronic venous insufficiency and varicose veins. Potential complications of foam sclerotherapy include cerebrovascular accidents and transient ischemic attacks (TIAs). We report the case of a 55-year-old woman who had a TIA shortly after undergoing foam sclerotherapy. She had presented for treatment with no confirmed risk factors for microemboli formation or thrombus. After the procedure, however, she had transient visual loss, dysarthria, confusion, and frontal headache, which resolved within 30 minutes of onset. A subsequent diagnosis of a patent foramen ovale was thought to have put her at risk for TIA in the setting of foam sclerotherapy. Osteopathic physicians should be aware of the potential for neurologic sequelae after foam sclerotherapy and inform patients prior to consent. PMID:27111786

  16. How prevalent are Plasmodium ovale and P. malariae in East Asia?

    Science.gov (United States)

    Kawamoto, F; Liu, Q; Ferreira, M U; Tantular, I S

    1999-10-01

    Plasmodium ovale and Plasmodium malariae, two of the four human malaria parasites, are usually found at very low prevalence in East Asia, even in areas with intense malaria transmission. In this article, Fumihiko Kawamoto, Qing Liu, Marcelo Ferreira and Indah Tantular review data obtained in recent field surveys, using alternative diagnostic methods such as acridine orange staining and PCR-based methods, to evaluate the prevalence of these two malaria species in East Asia. They argue that these species might be much more prevalent in East Asia than reported previously. In addition, they discuss the implications of sequence variations found in the small subunit ribosomal RNA genes of the two species targeted by diagnostic PCR and compare morphological criteria for speciation of malaria parasites stained with Giemsa and acridine orange. PMID:10481157

  17. Longitudinal and Hemispheric Variations of Nighttime E-Layer Electron Density in the Auroral Zone

    Science.gov (United States)

    Luan, X.; Wang, W.; Dou, X.; Burns, A. G.; Yue, X.

    2014-12-01

    The longitudinal patterns of nighttime E layer electron density in the auroral zone are analyzed in both hemispheres using COSMIC observation under quiet and solar minimum conditions. These l patterns are compared with the variations of particle precipitating energy flux from TIMED/GUVI under similar geophysical conditions, and also the solar radiation source of the auroral E layer are discussed. Our main conclusions are: (1) the nighttime maximum E-layer electron density presents pronounced longitudinal variations in the auroral zone, which depends on seasons and hemispheres. In local winter of both hemispheres and in northern equinox, maximum electron density is located in most western sectors within magnetic longitudes of 120-360°E. In local summer of both hemispheres and in southern equinox, greater the electron density occurs in a wide longitudinal sector centered at 0°E. (2) Hemispheric asymmetry occurs in auroral E layer electron density in all seasons, including equinox. In local winter, the maximum density of the northern hemisphere is much higher than that of southern hemisphere. In equinox, the longitudinal patterns of the electron density are out of phase between the two hemispheres. (3) The effects of the auroral precipitation are dominant in building the E layer electron density in the auroral zone for all seasons, except in southern summer in sector of 300-90°E MLON, where strong solar radiation takes place.

  18. Comparative anatomy of the foramen ovale in the hearts of cetaceans.

    Science.gov (United States)

    Macdonald, Alastair A; Carr, Peter A; Currie, Richard J W

    2007-07-01

    The structure of the cardiac foramen ovale from 17 species representing six cetacean families, the Monodontidae, Phocoenidae, Delphinidae, Ziphiidae, Balaenidae and the Balaenopteridae, was studied using the scanning electron microscope. Eight white whale fetuses (Delphinapterus leucas) and a narwhal fetus (Monodon monoceros) represented the Monodontidae; one fetal and nine neonatal harbour porpoises (Phocoena phocoena) and a finless porpoise fetus (Neophocoena phocoenoides) represented the Phocoenidae; two white-beaked dolphin fetuses (Lagenorhynchus albirostris), four fetal and one neonatal Atlantic white-sided dolphins (Lagenorhynchus acutus), a Risso's dolphin fetus (Grampus griseus), two common bottle-nosed dolphin neonates (Tursiops truncatus), a female short-beaked common dolphin fetus (Delphinus delphis), four killer whale fetuses (Orcinus orca) and two long-finned pilot whale fetuses (Globicephala melas) represented the Delphinidae; two northern bottlenose whale fetuses (Hyperoodon ampullatus) represented the Ziphiidae; one bowhead whale fetus (Balaena mysticetus) represented the Balaenidae and five Common minke whale fetuses (Balaenoptera acutorostrata), one blue whale fetus (Balaenoptera musculus), nine fin whale fetuses (Balaenoptera physalus) and four humpback whale fetuses (Megaptera novaeangliae) represented the Balaenopteridae. The hearts of an additional two incompletely identified toothed and four baleen whale fetuses were also studied. In each species the fold of tissue derived from the cardiac septum primum and subtended by the foramen ovale had the appearance of a short tunnel or sleeve which was fenestrated at its distal end. In the toothed whales the tissue fold was tunnel-shaped with the interatrial septum as the floor whereas in baleen whales it was more sleeve-like. In toothed whales thin threads extended from the fold to insert into the interatrial septum whereas a network of threads covered the distal end of the sleeve in the baleen

  19. Multidetector Row CT Detection of a Patent Foramen Ovale Causing Neurologic Deficits in an Adolescent: A Case Report

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jung Bin [Dept. of Radiology, Soonchunhyang University College of Medicine, Bucheon (Korea, Republic of); Kim, Dong Hun; Oh, Jae Hee [Dept. of Radiology, Chosun University College of Medicine, Gwangju (Korea, Republic of); Seo, Hye Sun [Dept. of Internal Medicine, Soonchunhyang University College of Medicine, Bucheon (Korea, Republic of); Suk, Eun Ha [Dept. of Anesthesiology and Pain Medicine, Asan Medical Center, Seoul (Korea, Republic of)

    2012-02-15

    A patent foramen ovale (PFO) is a persisting fetal circulation structural abnormality that can cause neurologic deficits such as migraine and cryptogenic stroke. Here we report a case of PFO diagnosed by cardiac multidetector row CT in an adolescent male with chronic migraine and stroke.

  20. Multidetector Row CT Detection of a Patent Foramen Ovale Causing Neurologic Deficits in an Adolescent: A Case Report

    International Nuclear Information System (INIS)

    A patent foramen ovale (PFO) is a persisting fetal circulation structural abnormality that can cause neurologic deficits such as migraine and cryptogenic stroke. Here we report a case of PFO diagnosed by cardiac multidetector row CT in an adolescent male with chronic migraine and stroke.

  1. Variation of Jupiter's aurora observed by Hisaki/EXCEED:2. estimations of auroral parameters and magnetospheric dynamics

    OpenAIRE

    Tao, Chihiro; Kimura, Tomoki; Badman, Sarah V.; André, Nicolas; Tsuchiya, Fuminori; Murakami, Go; Yoshioka, Kazuo; Yoshikawa, Ichiro; Yamazaki, Atsushi; Fujimoto, Masaki

    2016-01-01

    Jupiter's auroral parameters are estimated from observations by a spectrometer EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) onboard JAXA's Earth-orbiting planetary space telescope Hisaki. EXCEED provides continuous auroral spectra covering the wavelength range over 80–148 nm from the whole northern polar region. The auroral electron energy is estimated using a hydrocarbon color ratio adopted for the wavelength range of EXCEED, and the emission power in the long wavelength...

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

    Directory of Open Access Journals (Sweden)

    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

  3. Interactive Auroral Science for Hearing-Impaired Students

    Science.gov (United States)

    Samara, M.; Michell, R. G.; Jahn, J.; Pfeifer, M.; Ibarra, S.; Hampton, D. L.; Powell, D.

    2012-12-01

    Under a NASA E/PO grant, we have partnered with San Antonio's Sunshine Cottage School for Deaf Children to develop a science class experience where students directly interact with scientists and participate in a research-grade space science measurement campaign. The unique aspect of partnering with Sunshine Cottage lies in Sunshine's approach of auditory-verbal communication. Aided by technology (hearing aids, cochlear implants), a diverse student body with students of all levels of hearing loss (moderate through profound) is taught in an entirely auditory-verbal environment at Sunshine Cottage. Bringing these students into early contact with research work can lay the foundation for future careers in the STEM field that normally they might not consider as indicated by the first year of this collaboration where the student response was distinctly positive. Here we report on the first year of those activities, as they related to a ground based imaging approach to exploring the northern lights and from the point of view of the scientists that participated. The major components of that activity included a site visit to SwRI by the students and their teachers, a semester long lab at school utilizing current research tools and a real-time campaign night. The students used a number of diagnostics to first predict and then verify auroral activity. One of the tools used was the MOOSE observatory which is a community resource state of the art observatory comprised of 5 EMCCD imagers in Alaska, established through an NSF MRI grant. We will discuss the approach and lessons learned during the first year of the project and the directions that we will likely take in the second year. Lessons learned from teaching these students space science related topic can be flowed right back into mainstream classroom settings. One other significant and unexpected aspect of this first year was that we were able to connect two groups of students through skype (in the 4th to 5th grades) that

  4. Impulsive ion injections in the morning auroral region

    Science.gov (United States)

    Clemmons, J. H.; Carlson, C. W.; Boehm, M. H.

    1995-01-01

    Low altitude (less than 1000 km) measurements of ions precipitating into the morning auroral region are presented and analyzed. The ion fluxes exhibited time-energy signatures consistent with impulsive injection onto high-altitude field lines, followed by time-of-flight dispersion. The origin of these ions is investigated through the detailed examination of these signatures in conjunction with simultaneous measurements of precipitating electrons and a magnetic field model. A model is developed which indicates that the source for these particles was located in or near the magnetopause boundary layer, with the position deduced to be in the midlatitude flank region about 20-30 R(sub E) tailward of the Earth. The model explains the existence of multiple injections on a given field line as due to a quasi-periodic source, with the periodicity being about 100-200 s at the source. Several mechanisms are examined in an attempt to explain the injections, with a mechanism related to the propagation of waves on the surface of the boundary layer found to be the most plausible. The observations and results are compared to those of similar experiments and some unifying ideas are discussed.

  5. Langmuir turbulence in the auroral ionosphere 1: Linear theory

    Science.gov (United States)

    Newman, D. L.; Goldman, M. V.; Ergun, R. E.; Boehm, M. H.

    1994-01-01

    Intense bursts of Langmuir waves with electric fields of 50 to 500 mV / m have been frequently observed at altitudes greater than 500 km in the auroral ionosphere. These bursts are driven by 20 eV to 4 keV field-aligned electrons, which are embedded in an approximately isotropic nonthermal tail of scattered electrons. The Langmuir bursts are often observed at altitudes where the ionosphere is moderately magnetized (OMEGA (sub e) approximately equals omega (sub pe)). Both the moderate magnetization and the scattered electrons have a major influence on the linear dispersion and damping of Langmuir waves. In particular, the linear dispersion is topologically different depending on whether the magnetic field is subcritical (OMEGA (sub e) less than omega (sub pe)) or supercritical (OMEGA (sub e) greater than omega (sub pe)). The correct dispersion and damping can account for the observed polarization of the Langmuir waves, which is very nearly parallel to the geomagnetic field. Inferred properties of the linear instability driven by the field-aligned electrons are discussed. The linear dispersion and damping derived here provide the basis for a nonlinear turbulence study described in a companion paper (Newman et al., this issue).

  6. Juno's Earth flyby: the Jupiter infrared auroral mapper preliminary results

    Science.gov (United States)

    Adriani, Alberto; Mura, Alessandro; Grassi, Davide; Piccioni, Giuseppe; Di Iorio, Tatiana; Tosi, Federico; Noschese, Raffaella; Moriconi, Maria Luisa; Filacchione, Gianrico; Sindoni, Giuseppe; Cicchetti, Andrea

    The Juno spacecraft has been launched on August 2011 with the goal of investigating the origin and evolution of Jupiter. JIRAM, the Jupiter Infrared Auroral Mapper on board the spacecraft, is a spectro-imager whose science objectives are the auroras’ analysis, the atmospheric component gases retrieval in hot spots and the constraining of the Jupiter’s formation environment through the study of the composition and the abundances of the chemical species in the Jovian atmosphere. To achieve these objectives JIRAM is equipped with a IR imager split in two spectral channels: L band, centered at 3.45 mum with a 290 nm bandwidth, and M band, centered at 4.78 mum with a 480 nm bandwidth, and a spectrometer in the 2.0-5.0 mum interval. JIRAM status and capabilities have been tested on 9 October 2013 during the Juno’s Earth flyby. The instrument targeted the Moon for about half an hour. Beyond the scientific value of the observation, this has been so far the first occasion during the cruise phase to verify the execution of the science observing sequences as they will be operated at Jupiter. Here the first elaboration of that series of observations is presented. The imager in M band has been able to capture the Moon region straddling the terminator. Some surface features are recognizable and have been mapped with the support of the geometric information available for JIRAM data. Spectra from the most prominent surface structure visualized, are also shown.

  7. Laboratory Reproduction of Auroral Magnetospheric Radio Wave Sources

    Science.gov (United States)

    Ronald, K.; Speirs, D. C.; McConville, S. L.; Gillespie, K. M.; Phelps, A. D. R.; Cross, A. W.; Bingham, R.; Robertson, C. W.; Whyte, C. G.; Vorgul, I.; Cairns, R. A.; Kellett, B. J.; He, W.

    2008-10-01

    Auroral Kilometric Radiation, AKR, occurs naturally in the polar regions of the Earth's magnetosphere where electrons are accelerated by electric fields into the increasing planetary magnetic dipole. Here conservation of the magnetic moment converts axial to rotational momentum forming a horseshoe distribution in velocity phase space. This distribution is unstable to cyclotron emissions and radiation is emitted in the X-mode. In the laboratory a 75-85kV electron beam of 5-40A was magnetically compressed by a system of solenoids. Results are presented for an electron beam gyrating at cyclotron frequencies of 4.42GHz and 11.7GHz resonating with near cut-off TE01 and TE03 modes respectively. Measurements of the electron transport combined with numerical simulations demonstrated that a horseshoe distribution function was formed in electron velocity space. Analysis of the experimental measurements allowed the inference of the 1D number density as a function of the electron beam pitch angle. The total power emitted experimentally was ~19-35 kW with a maximum RF emission efficiency of ~2%. These results were compared to those obtained numerically using a 2D PiC code KARAT with a maximum efficiency of 2% predicted for the same mode and frequency, consistent with astrophysical and theoretical results.

  8. Laboratory Reproduction of Auroral Magnetospheric Radio Wave Sources

    International Nuclear Information System (INIS)

    Auroral Kilometric Radiation, AKR, occurs naturally in the polar regions of the Earth's magnetosphere where electrons are accelerated by electric fields into the increasing planetary magnetic dipole. Here conservation of the magnetic moment converts axial to rotational momentum forming a horseshoe distribution in velocity phase space. This distribution is unstable to cyclotron emissions and radiation is emitted in the X-mode. In the laboratory a 75-85kV electron beam of 5-40A was magnetically compressed by a system of solenoids. Results are presented for an electron beam gyrating at cyclotron frequencies of 4.42GHz and 11.7GHz resonating with near cut-off TE01 and TE03 modes respectively. Measurements of the electron transport combined with numerical simulations demonstrated that a horseshoe distribution function was formed in electron velocity space. Analysis of the experimental measurements allowed the inference of the 1D number density as a function of the electron beam pitch angle. The total power emitted experimentally was ∼19-35 kW with a maximum RF emission efficiency of ∼2%. These results were compared to those obtained numerically using a 2D PiC code KARAT with a maximum efficiency of 2% predicted for the same mode and frequency, consistent with astrophysical and theoretical results.

  9. Volumetric imaging of the auroral ionosphere: Initial results from PFISR

    Science.gov (United States)

    Semeter, Joshua; Butler, Thomas; Heinselman, Craig; Nicolls, Michael; Kelly, John; Hampton, Donald

    2009-05-01

    The Poker Flat Incoherent Scatter Radar (PFISR) is the first dedicated ISR built with an electronically steerable array. This paper demonstrates the capabilities of PFISR for producing three-dimensional volumetric images of E-region ionization patterns produced by the aurora. The phase table was configured to cycle through 121 beam positions arranged in an 11×11 grid. A 13-baud Barker coded pulse was used, which provided ~1.5-km range resolution out to a maximum range of 250 km. Backscattered power was converted to electron density by correcting for path loss and applying the Buneman approximation assuming equal electron and ion temperatures. The results were then interpolated onto a three-dimensional cartesian grid. Volumetric images are presented at 5-min, 1-min, and 14.6-s integration times (corresponding to 960, 192, and 48 pulses-per-position, respectively) to illustrate the tradeoff between spatio-temporal resolution and data quality. At 14.6 s cadence, variability in plasma density within the volume appears to be fully resolved in space and time, a result that is supported by both observational evidence and theoretical predictions of ionospheric response times. Some potential applications of this mode for studying magnetosphere-ionosphere interactions in the auroral zone are discussed.

  10. Parameterization of ionization rate by auroral electron precipitation in Jupiter

    Directory of Open Access Journals (Sweden)

    Y. Hiraki

    2008-02-01

    Full Text Available We simulate auroral electron precipitation into the Jovian atmosphere in which electron multi-directional scattering and energy degradation processes are treated exactly with a Monte Carlo technique. We make a parameterization of the calculated ionization rate of the neutral gas by electron impact in a similar way as used for the Earth's aurora. Our method allows the altitude distribution of the ionization rate to be obtained as a function of an arbitrary initial energy spectrum in the range of 1–200 keV. It also includes incident angle dependence and an arbitrary density distribution of molecular hydrogen. We show that there is little dependence of the estimated ionospheric conductance on atomic species such as H and He. We compare our results with those of recent studies with different electron transport schemes by adapting our parameterization to their atmospheric conditions. We discuss the intrinsic problem of their simplified assumption. The ionospheric conductance, which is important for Jupiter's magnetosphere-ionosphere coupling system, is estimated to vary by a factor depending on the electron energy spectrum based on recent observation and modeling. We discuss this difference through the relation with field-aligned current and electron spectrum.

  11. Velocities of auroral coherent echoes at 12 and 144 MHz

    Directory of Open Access Journals (Sweden)

    A. V. Koustov

    Full Text Available Two Doppler coherent radar systems are currently working at Hankasalmi, Finland, the STARE and CUTLASS radars operating at ~144 MHz and ~12 MHz, respectively. The STARE beam 3 is nearly co-located with the CUTLASS beam 5, providing an opportunity for echo velocity comparison along the same direction but at significantly different radar frequencies. In this study we consider an event when STARE radar echoes are detected at the same ranges as CUT-LASS radar echoes. The observations are complemented by EISCAT measurements of the ionospheric electric field and electron density behaviour at one range of 900 km. Two separate situations are studied; for the first one, CUTLASS observed F-region echoes (including the range of the EIS-CAT measurements, while for the second one CUTLASS observed E-region echoes. In both cases STARE E-region measurements were available. We show that F-region CUT-LASS velocities agree well with the convection component along the CUTLASS radar beam, while STARE velocities are typically smaller by a factor of 2–3. For the second case, STARE velocities are found to be either smaller or larger than CUTLASS velocities, depending on the range. Plasma physics of E-and F-region irregularities is discussed in attempt to explain the inferred relationship between various velocities. Special attention is paid to ionospheric refraction that is important for the detection of 12-MHz echoes.

    Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; auroral ionosphere

  12. Juno's Earth flyby: the Jovian infrared Auroral Mapper preliminary results

    Science.gov (United States)

    Adriani, A.; Moriconi, M. L.; Mura, A.; Tosi, F.; Sindoni, G.; Noschese, R.; Cicchetti, A.; Filacchione, G.

    2016-08-01

    The Jovian InfraRed Auroral Mapper, JIRAM, is an image-spectrometer onboard the NASA Juno spacecraft flying to Jupiter. The instrument has been designed to study the aurora and the atmosphere of the planet in the spectral range 2-5 μm. The very first scientific observation taken with the instrument was at the Moon just before Juno's Earth fly-by occurred on October 9, 2013. The purpose was to check the instrument regular operation modes and to optimize the instrumental performances. The testing activity will be completed with pointing and a radiometric/spectral calibrations shortly after Jupiter Orbit Insertion. Then the reconstruction of some Moon infrared images, together with co-located spectra used to retrieve the lunar surface temperature, is a fundamental step in the instrument operation tuning. The main scope of this article is to serve as a reference to future users of the JIRAM datasets after public release with the NASA Planetary Data System.

  13. Ionospheric current system accompanied by auroral vortex streets

    CERN Document Server

    Hiraki, Yasutaka

    2016-01-01

    High resolution optical measurements have revealed that a sudden brightening of aurora and its deformation from an arc-like to a vortex street structure appear just at the onset of substorm. The instability of Alfv$\\acute{\\rm e}$n waves reflected from the ionosphere has been studied by means of magnetohydrodynamic simulations in order to comprehend the formation of auroral vortex streets. Our previous work reported that an initially placed arc intensifies, splits, and deforms into a vortex street during a couple of minutes, and the prime key is an enhancement of the convection electric field. This study elaborated physics of the ionospheric horizontal currents related to the vortex street in the context of so-called Cowling polarization. One component is due to the perturbed electric field by Alfv$\\acute{\\rm e}$n waves, and the other is due to the perturbed electron density (or polarization) in the ionosphere. It was found that, when a vortex street develops, upward/downward pair currents in its leading/trail...

  14. Characteristics of a stable auroral red arc event

    International Nuclear Information System (INIS)

    An intense (approx.2.2 kR) stable auroral red (SAR) arc was observed on October 23, 1981 by the Dynamics Explorer 1 and 2 satellites as well as by a ground based photometer operated by the Pacific Northwest Laboratory at Battelle Observatory in Richland, Washington, providing a unique series of nearly simultaneous measurements. The DE satellites provided in-situ electric-field and particle measurements at altitudes of about 850 km and 6000 km along approximately the same flux tube as well as in-situ electron temperature and density measurements at 850 km for this red arc. These measurements along with ground-based determination of arc position and intensity allowed a comprehensive analysis of the arc. Calculations of the electron heating rate and temperature which result from the observed precipitating electron flux at the arc location indicate that the heat required to establish the necessary and observed ionospheric electron temperatures is provided by the extrapolated low energy electron particle flux. The available data does not provide sufficient information to uniquely determine the energy source for this flux

  15. Role of ionospheric effects and plasma sheet dynamics in the formation of auroral arcs

    Science.gov (United States)

    Prakash, Manju; Rankin, R.

    2001-01-01

    At the ionospheric level, the substorm onset (expansion phase) is marked by the initial brightening and subsequent breakup of a pre-existing auroral arc. According to the field line resonance (FLR) wave model, the substorm-related auroral arc is caused by the field-aligned current carried by FLRs. The FLRs are standing shear Alfvén wave structures that are excited along the dipole/quasi-dipole lines of the geomagnetic field. The FLRs (that can cause auroral arc) thread from the Earthward edge of the plasma sheet and link the auroral arc to the plasma sheet region of 6-15 R_E. The region is associated with magnetic fluctuations that result from the nonlinear wave-wave interactions of the cross-field current-instability. The instability (excited at the substorm onset) disrupts the cross-tail current which is built up during the growth phase of the substorms and results in magnetic fluctuations. The diversion of the current to polar regions can lead to auroral arc intensification. The current FLR model is based on the amplitude equations that describe the nonlinear space-time evolution of FLRs in the presence of ponderomotive forces exerted by large amplitude FLRs (excited during substorms). The present work will modify the FLR wave model to include the effects arising from magnetic fluctuations that result from current disruption near the plasma sheet (6-15 R_E). The nonlinear evolution of FLRs is coupled with the dynamics of plasma sheet through a momentum exchange term (resulting from magnetic fluctuations due to current disruption) in the generalized Ohm's law. The resulting amplitude equations including the effects arising from magnetic fluctuations can be used to study the structure of the auroral arcs formed during substorms. We have also studied the role of feedback mechanism (in a dipole geometry of the geomagnetic field) in the formation of the discrete auroral arc observed on the nightside magnetosphere. The present nonlinear dispersive model (NDM) is

  16. Insulin-like growth factor binding protein-3 is required for the regulation of rat oval cell proliferation and differentiation in the 2AAF/PHX model

    Directory of Open Access Journals (Sweden)

    Nicole C Steiger-Luther

    2010-02-01

    Full Text Available Nicole C Steiger-Luther1, Houda Darwiche1, Seh-Hoon Oh1, Jennifer M Williams1, Bryon E Petersen1,21Department of Pathology, Immunology and Laboratory Medicine, 2Program in Stem Cell Biology and Regenerative Medicine, College of Medicine, University of Florida, Gainesville, FL, USAAbstract: Oval cell-mediated liver regeneration is a highly complex process that involves the coordination of several signaling factors, chemokines and cytokines to allow for proper maintenance of the liver architecture. When hepatocyte proliferation is inhibited, an hepatic stem cell population, often referred to as “oval cells”, is activated to aid in liver regeneration. The function of insulin-like growth factor binding protein-3 (IGFBP-3 during this process of oval cell activation is of particular interest because it is produced in liver and has been shown to induce migration and differentiation of other stem cell populations both in vitro and in vivo. Additionally, IGFBP-3 production has been linked to the transforming growth factor-β (TGF-β superfamily, a pathway known to be induced during oval cell proliferation. In this study, we set out to determine whether IGFBP-3 plays a role in oval cell proliferation, migration and differentiation during this specific type of regeneration. Through activation of the oval cell-mediated liver regeneration in a rat model, we found that IGFBP-3 is elevated in the liver and serum of animals during peak days of oval cell activation and proliferation. Furthermore, in vitro assays found that WB-344 cells, a liver stem cell line similar to oval cells, were induced to migrate in the presence of IGFBP-3. When expression of IGFBP-3 was knocked down during oval cell activation in vivo, we found that oval cell proliferation was increased and observed the appearance of numerous atypical ductular structures, which were OV-6 and Ki67-positive. Finally, quantitative realtime PCR analysis of liver tissue from IGFBP-3 small interfering

  17. Brain magnetic resonance imaging findings in cryptogenic stroke patients under 60 years with patent foramen ovale

    International Nuclear Information System (INIS)

    Purpose: To compare magnetic resonance imaging (MRI) brain feature in cryptogenic stroke patients with patent foramen ovale (PFO), cryptogenic stroke patients without PFO and patients with cardioembolic stroke. Materials and methods: The ethics committee required neither institutional review board approval nor informed patient consent for retrospective analyses of the patients’ medical records and imaging data. The patients’ medical files were retrospectively reviewed in accordance with human subject research protocols. Ninety-two patients under 60 years of age were included: 15 with cardioembolic stroke, 32 with cryptogenic stroke with PFO and 45 with cryptogenic stroke without PFO. Diffusion-weighted imaging of brain MRI was performed by a radiologist blinded to clinical data. Univariate, Fischer's exact test for qualitative data and non-parametric Wilcoxon test for quantitative data were used. Results: There was no statistically significant difference found between MRI features of patients with PFO and those with cardioembolic stroke (p < .05). Patients without PFO present more corticosubcortical single lesions (p < .05) than patients with PFO. Patients with PFO have more often subcortical single lesions larger than 15 mm, involvement of posterior cerebral arterial territory and intracranial occlusion (p < .05) than patients with cryptogenic stroke without PFO. Conclusion: Our study suggests a cardioembolic mechanism in ischemic stroke with PFO

  18. The role of persistent foramen ovale and other shunts in decompression illness.

    Science.gov (United States)

    Wilmshurst, Peter T

    2015-06-01

    A persistent foramen ovale (PFO) and other types of right-to-left shunts are associated with neurological, cutaneous and cardiovascular decompression illness (DCI). A right-to-left shunt is particularly likely to be implicated in causation when these types of DCI occur after dives that are not provocative. It is believed that venous nitrogen bubbles that form after decompression pass through the shunt to circumvent the lung filter and invade systemic tissues supersaturated with nitrogen (or other inert gas) and as a result there is peripheral amplification of bubble emboli in those tissues. Approximately a quarter of the population have a PFO, but only a small proportion of the population with the largest right-to-left shunts are at high risk of shunt-mediated DCI. The increased risk of DCI in people with migraine with aura is because migraine with aura is also associated with right-to-left shunts and this increased risk of DCI appears to be confi ned to those with a large PFO or other large shunt. Various ultrasound techniques can be used to detect and assess the size of right-to-left shunts by imaging the appearance of bubble contrast in the systemic circulation after intravenous injection. In divers with a history of shunt-mediated DCI, methods to reduce the risk of recurrence include cessation of diving, modification of future dives to prevent venous bubble liberation and transcatheter closure of a PFO. PMID:26165532

  19. Steady state operation of a copper-water LHP with a flat-oval evaporator

    International Nuclear Information System (INIS)

    In order to dissipate the heat generated by electronic boxes in avionic systems, a copper-water LHP with a flat-oval evaporator was fabricated and tested at steady state. The LHP consists of a flat shaped evaporator, 7 mm thick, including compensation chamber with attached heat exchanger. The condenser is cooled by forced convection of liquid. The variable parameters are the heat sink and ambient temperatures (20 and 55 oC), the orientation (-90o to +90o in two perpendicular planes) and the power input (0-100 W). Evaporator wall temperatures are higher when the evaporator is placed above the condenser. For heat sink and ambient temperature of 20 oC the evaporator wall temperature does not vary much with heat load for all measured elevations. But it fluctuates at heat sink and ambient temperature equal to 55 oC when the evaporator is placed below the condenser. The LHP total thermal resistance is governed by the condenser resistance. It decreases with increasing heat load, whatever the operating conditions, because the part of the condenser internal surface area used for condensation increases too. A minimum thermal resistance of 0.2 K/W was obtained. The maximum thermal resistance was 2.7 K/W.

  20. Extracting contours of oval-shaped objects by Hough transform and minimal path algorithms

    Science.gov (United States)

    Tleis, Mohamed; Verbeek, Fons J.

    2014-04-01

    Circular and oval-like objects are very common in cell and micro biology. These objects need to be analyzed, and to that end, digitized images from the microscope are used so as to come to an automated analysis pipeline. It is essential to detect all the objects in an image as well as to extract the exact contour of each individual object. In this manner it becomes possible to perform measurements on these objects, i.e. shape and texture features. Our measurement objective is achieved by probing contour detection through dynamic programming. In this paper we describe a method that uses Hough transform and two minimal path algorithms to detect contours of (ovoid-like) objects. These algorithms are based on an existing grey-weighted distance transform and a new algorithm to extract the circular shortest path in an image. The methods are tested on an artificial dataset of a 1000 images, with an F1-score of 0.972. In a case study with yeast cells, contours from our methods were compared with another solution using Pratt's figure of merit. Results indicate that our methods were more precise based on a comparison with a ground-truth dataset. As far as yeast cells are concerned, the segmentation and measurement results enable, in future work, to retrieve information from different developmental stages of the cell using complex features.

  1. A patient with pulmonary embolism and patent foramen ovale. The value of transcranial doppler

    Directory of Open Access Journals (Sweden)

    Maria Stougianni

    2013-06-01

    Full Text Available SUMMARY: The case is presented of a 46 year-old male, obese and a heavy smoker, who presented with acute dyspnea a few hours after elective arthroscopy of his left knee. He was admitted to the intensive care unit (ICU because of severe hypoxaemia, and was started on anticoagulant therapy because of intermediate risk of pulmonary embolism. In view of the refractory hypoxaemia that worsened during intense Valsalva manoeuvre, the suspicion of an intracardiac (interatrial right-to-left shunt was raised, most probably a patent foramen ovale (PFO or atrial septal defect (ASD. In view of the severe hypoxaemia and the anticoagulant therapy, initial assessment with transcranial Doppler (TCD examination with bubble test study was deemed preferable and this confirmed a shunt. Subsequent transoesophageal echocardiography (TEE bubble test assessment demonstrated the presence of a PFO. Recent recommendations favour TCD as the method of choice for detecting PFO because it is non-invasive, cheaper, faster to perform and comparable with TEE in terms of sensitivity and specificity. The introduction of portable ultrasound devices into the everyday hospital routine renders the application of TCD easier for clinicians of various specialties.

  2. Performance of Three Single Instrument Systems in the Preparation of Long Oval Canals.

    Science.gov (United States)

    Coelho, Beatriz Serrato; Amaral, Rodrigo Otavio Jatahy Ferreira do; Leonardi, Denise Piotto; Marques-da-Silva, Bruno; Silva-Sousa, Yara Teresinha Corrêa; Carvalho, Fredson Marcio Acris de; Baratto-Filho, Flares

    2016-01-01

    This study aimed to evaluate the performance of the Wave One, Easy ProDesign Logic and One Shape systems in the preparation of long oval root canals. Forty-two mandibular incisors were randomized into three groups: Group I, Wave One Primary (WO) (#25.08); Group II, Easy ProDesign Logic (EPL) (#25.06) and Group III, One Shape (OS) (#25.06). Micro-computed tomography scans were obtained pre- and post-preparation of the samples. Instrument fractures or loss of working length did not occur in any of the groups. There was a statistically significant difference in total root canal volume between the WO and EPL (pEPL and 71.8% in the OS (p>0.05). The OS system had the strongest correlation between volume increase and instrumented area (R=0.63). The WO, EPL and OS systems presented mean preparation times of 2.13 min, 0.54 min, and 2.21 min (pEPL system was the fastest. PMID:27058387

  3. In vitro proliferation and differentiation of hepatic oval cells and their potential capacity for intrahepatic transplantation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Z.; Chen, J. [Liaocheng People' s Hospital, Department of Hepatobiliary Surgery, Liaocheng, Shandong, China, Department of Hepatobiliary Surgery, Liaocheng People’s Hospital, Liaocheng, Shandong (China); Li, L.; Ran, J.H.; Liu, J. [The First People' s Hospital of Kunming, Kunming, Yunnan, China, The First People’s Hospital of Kunming, Kunming, Yunnan (China); Gao, T.X.; Guo, B.Y. [Dongchangfu Hospital of Women and Child Health Care, Liaocheng, Shandong (China); Li, X.H.; Liu, Z.H.; Liu, G.J.; Gao, Y.C.; Zhang, X.L. [Liaocheng People' s Hospital, Department of Hepatobiliary Surgery, Liaocheng, Shandong, China, Department of Hepatobiliary Surgery, Liaocheng People’s Hospital, Liaocheng, Shandong (China)

    2013-07-30

    Hepatic oval cells (HOCs) are recognized as facultative liver progenitor cells that play a role in liver regeneration after acute liver injury. Here, we investigated the in vitro proliferation and differentiation characteristics of HOCs in order to explore their potential capacity for intrahepatic transplantation. Clusters or scattered HOCs were detected in the portal area and interlobular bile duct in the liver of rats subjected to the modified 2-acetylaminofluorene and partial hepatectomy method. Isolated HOCs were positive for c-kit and CD90 staining (99.8% and 88.8%, respectively), and negative for CD34 staining (3.6%) as shown by immunostaining and flow cytometric analysis. In addition, HOCs could be differentiated into hepatocytes and bile duct epithelial cells after leukemia inhibitory factor deprivation. A two-cuff technique was used for orthotopic liver transplantation, and HOCs were subsequently transplanted into recipients. Biochemical indicators of liver function were assessed 4 weeks after transplantation. HOC transplantation significantly prolonged the median survival time and improved the liver function of rats receiving HOCs compared to controls (P=0.003, Student t-test). Administration of HOCs to rats also receiving liver transplantation significantly reduced acute allograft rejection compared to control liver transplant rats 3 weeks following transplantation (rejection activity index score: control=6.3±0.9; HOC=3.5±1.5; P=0.005). These results indicate that HOCs may be useful in therapeutic liver regeneration after orthotopic liver transplantation.

  4. In vitro proliferation and differentiation of hepatic oval cells and their potential capacity for intrahepatic transplantation

    International Nuclear Information System (INIS)

    Hepatic oval cells (HOCs) are recognized as facultative liver progenitor cells that play a role in liver regeneration after acute liver injury. Here, we investigated the in vitro proliferation and differentiation characteristics of HOCs in order to explore their potential capacity for intrahepatic transplantation. Clusters or scattered HOCs were detected in the portal area and interlobular bile duct in the liver of rats subjected to the modified 2-acetylaminofluorene and partial hepatectomy method. Isolated HOCs were positive for c-kit and CD90 staining (99.8% and 88.8%, respectively), and negative for CD34 staining (3.6%) as shown by immunostaining and flow cytometric analysis. In addition, HOCs could be differentiated into hepatocytes and bile duct epithelial cells after leukemia inhibitory factor deprivation. A two-cuff technique was used for orthotopic liver transplantation, and HOCs were subsequently transplanted into recipients. Biochemical indicators of liver function were assessed 4 weeks after transplantation. HOC transplantation significantly prolonged the median survival time and improved the liver function of rats receiving HOCs compared to controls (P=0.003, Student t-test). Administration of HOCs to rats also receiving liver transplantation significantly reduced acute allograft rejection compared to control liver transplant rats 3 weeks following transplantation (rejection activity index score: control=6.3±0.9; HOC=3.5±1.5; P=0.005). These results indicate that HOCs may be useful in therapeutic liver regeneration after orthotopic liver transplantation

  5. Exercise treadmill saline contrast echocardiography for the detection of patent foramen ovale in hypoxia.

    Science.gov (United States)

    Fenster, Brett E; Freeman, Andrew M; Silveira, Lori; Buckner, J Kern; Curran-Everett, Douglas; Carroll, John D

    2015-12-01

    Percutaneous patent foramen ovale (PFO) occluder placement improves dyspnea and oxygen requirement in hypoxic patients with PFO-mediated right-to-left shunt (RTLS). Although saline contrast echocardiography (SCE) in the resting state can identify PFO RTLS, SCE performed with exercise stress testing may provide incremental diagnostic yield compared to rest SCE. We evaluated the ability of exercise SCE to predict PFO presence and size using intracardiac echocardiography (ICE) as a gold standard in a hypoxic cohort. Thirty-three hypoxic patients with suspected PFO RTLS who underwent rest, Valsalva, and exercise stress SCE prior to ICE were evaluated retrospectively. PFO RTLS was defined by ICE findings including PFO anatomy, RTLS by saline contrast and color Doppler, and probe patency. SCE shunt severity was compared to the presence of ICE-defined PFO RTLS and PFO size. Exercise SCE for the detection of PFO RTLS performed with an area under the curve of 0.77, sensitivity of 73%, and specificity of 86%. Among 26 patients with PFO RTLS, exercise SCE identified four additional patients with PFO that had negative rest SCE and two patients with negative Valsalva SCE. Exercise SCE had a stronger correlation with PFO size than resting or Valsalva SCE. Exercise SCE detects PFO RTLS and predicts PFO size in a hypoxic cohort. In addition, exercise SCE can identify PFO RTLS that is otherwise undetected with rest or Valsalva SCE. Exercise SCE may be appropriate when a clinical suspicion for PFO RTLS persists despite negative rest and Valsalva SCE. PMID:26231342

  6. Planar Microwave Sensor for Theranostic Therapy of Organic Tissue Based on Oval Split Ring Resonators.

    Science.gov (United States)

    Reimann, Carolin; Puentes, Margarita; Maasch, Matthias; Hübner, Frank; Bazrafshan, Babak; Vogl, Thomas J; Damm, Christian; Jakoby, Rolf

    2016-01-01

    Microwave sensors in medical environments play a significant role due to the contact-less and non-invasive sensing mechanism to determine dielectric properties of tissue. In this work, a theranostic sensor based on Split Ring Resonators (SRRs) is presented that provides two operation modes to detect and treat tumor cells, exemplary in the liver. For the detection mode, resonance frequency changes due to abnormalities are evaluated, and in the treatment mode, microwave ablation is performed. The planar sensor structure can be integrated into a needle like a surgery tool that evokes challenges concerning size limitations and biocompatibility. To meet the size requirements and provide a reasonable operating frequency, properties of oval shaped SRRs are investigated. By elongating the radius of the SRR in one direction, the resonance frequency can be decreased significantly compared to circular SRR by a factor of two below 12 GHz. In order to validate the detection and treatment characteristics of the sensor, full wave simulations and measurements are examined. Clear resonance shifts are detected for loading the sensor structures with phantoms mimicking healthy and malignant tissue. For treatment mode evaluation, ex vivo beef liver tissue was ablated leading to a lesion zone 1.2 cm × 1 cm × 0.3 cm with a three minute exposure of maximum 2.1 W. PMID:27618050

  7. Branch Retinal Artery Occlusion in a Patient with Patent Foramen Ovale

    Directory of Open Access Journals (Sweden)

    Nasser Shoeibi

    2013-01-01

    Full Text Available Purpose: To report branch retinal artery occlusion (BRAO in a patient with patent foramen ovale (PFO. Case Report: A 29-year-old female patient was referred for sudden onset superior visual field defect in her left eye. Ocular examination revealed visual acuity of 20/32 in the affected eye along with a positive relative afferent pupillary defect. A calcified white embolus was noted at the first bifurcation of the inferior temporal artery in her left eye together with mild retinal edema. With a diagnosis of BRAO, the patient received oral acetazolamide, topical timolol, ocular massage and anterior chamber paracentesis. The visual field defect partially recovered and the embolus moved to the third bifurcation level as revealed by fundus examination. An extensive workup, including neurology, rheumatology, cardiology and hematology consultation, carotid ultrasonography, transthoracic/transesophageal echocardiography and laboratory testing was performed. All results were within normal limits except for a small-sized PFO detected by transesophageal echocardiography. Low-dose aspirin therapy was initiated and over the subsequent two years, no other embolic event occurred. Conclusion: The association between PFO and BRAO has not yet been reported. Intracardiac right-to-left shunting through a PFO, accentuated by Valsalva maneuver, may predispose to embolic events while the source of initial thrombosis remains unknown.

  8. Auroral images and particle precipitations observed by S-310JA-8, -9, and -10 at Syowa Station

    International Nuclear Information System (INIS)

    Three sounding rockets were launched in 1984 from Syowa Station in Antarctica into different types of aurora, designated as AURORA I (an active auroral arc at the substorm expansion phase), II (a stable are prior to the substrom onset) and III (a diffuse aurora during the recovery phase). A new television camera was used to take an auroral picture, together with the electron spectrometers to measure the energy spectrum of auroral particles. AURORA I showed greater values in both auroral emission and electron density than for AURORA II. In AURORA III, although the auroral emission intensity was much less in comparison with AURORA I, the electron density showed a pronounced enhancement in the D-region and was comparable with the case of AURORA I above the E-region. As for an energy spectrum of auroral electrons, AURORA I and II showed an inverted-V type monoenergetic peak with much higher energy for AURORA I than for AURORA II, whereas AURORA III exhibits a power-law spectrum with a small superposing monoenergetic peak around 0.5 keV above 200 km in altitude. The television camera showed a dependence of auroral color spectrum on the auroral activity, i.e., the ratio of an apparent emission rate at 427.8 nm and an illuminance in a visible range (400 to 800 nm) becomes greater for brighter aurora. (author)

  9. Oclusão de artéria central da retina associada ao forame oval patente

    OpenAIRE

    Patrícia Regina de Pinho Tavares; Mariana Rezende de Oliveira; Eduardo de Castro Miranda Diniz; Rafael Mourão Agostini; Daniela Vieira de Aguiar

    2014-01-01

    Oclusão da artéria central da retina é uma doença comumente encontrada em pacientes idosos, mas pode também ser vista em crianças e adultos jovens. Nestes, as principais causas são anomalias cardíacas, sendo o forame oval patente o mais observado. O objetivo do trabalho é relatar o caso de um paciente jovem com oclusão da artéria central da retina apresentando persistência de forame oval e, também, salientar a importância de uma propedêutica detalhada nos casos de oclusões vasculares da retin...

  10. The 2008 Passage of Jupiter's Great Red Spot and Oval BA as Observed from Hubble/WFPC2

    Science.gov (United States)

    Simon-Miller, Amy A.; Chanover, N. J.; Orton, G. S.; Tsavaris, I.

    2008-01-01

    Hubble Space Telescope data of the passage of Jupiter's Great Red Spot (GRS) and Oval BA were acquired on May 15, June 28 (near closest approach), and July 8. Wind fields were measured from Wide Field Planetary Camera 2 (WFPC2) data with 10-hour separations before and after closest approach, and within the GRS with 40-minute separations on all three dates. Color information was also derived using 8 narrowband WFPC2 filters from 343 to 673-nm on all three dates. We will present the results of principal components and wind analyses and discuss unique features seen in this data set. In addition, we will highlight any changes observed in the GRS, Oval BA and their surroundings as a result of the passage, including the movement of a smaller red anticyclone from west of the GRS, around its southern periphery, and to the east of the GRS.

  11. Oclusão de artéria central da retina associada ao forame oval patente

    Directory of Open Access Journals (Sweden)

    Patrícia Regina de Pinho Tavares

    2014-10-01

    Full Text Available Oclusão da artéria central da retina é uma doença comumente encontrada em pacientes idosos, mas pode também ser vista em crianças e adultos jovens. Nestes, as principais causas são anomalias cardíacas, sendo o forame oval patente o mais observado. O objetivo do trabalho é relatar o caso de um paciente jovem com oclusão da artéria central da retina apresentando persistência de forame oval e, também, salientar a importância de uma propedêutica detalhada nos casos de oclusões vasculares da retina.

  12. Comparative anatomy of the cardiac foramen ovale in cats (Felidae), dogs (Canidae), bears (Ursidae) and hyaenas (Hyaenidae).

    OpenAIRE

    Macdonald, A A; Johnstone, M.

    1995-01-01

    The structure of the foramen ovale from 16 species representing 4 carnivore families, the Felidae, Canidae, Ursidae and Hyaenidae, was studied using the scanning electron microscope. The Felidae were represented by 9 domestic cat fetuses (Felis catus), 2 snow leopard neonates (Uncia uncia), an ocelot neonate (Leopardus pardalis), 2 lion neonates (Panthera leo), a panther neonate (Panthera pardus) and 3 tigers (Neofelis tigris), comprising 2 fetuses and a neonate. The Canidae were represented ...

  13. CT and MR imaging findings of subdural dermoid cyst extending into right foramen ovale: a case report

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, You Cheol; Park, Cheol Min; Lee, Si Kyeong [Seoul Medical Center, Seoul (Korea, Republic of)

    2006-12-15

    Intracranial dermoid cyst is a rare congenital benign disease, representing less than 0.5% of primary brain tumors. Nevertheless, if ruptured spontaneously or during surgery, it has a poor prognosis due to chemical meningitis. Therefore, it is essential to perform accurate diagnosis and proper treatment. We report an intracranial subdural dermoid cyst that may be misdiagnosed as extracranial or epidural lesion because of extension into the right foramen ovale, and describe the CT and MR imaging findings.

  14. Hypoxemia without persistent right-to-left pressure gradient across a patent foramen ovale: A clinical challenge

    OpenAIRE

    2013-01-01

    Patent foramen ovale (PFO) closure for systemic hypoxemia is controversial. The first systematic, albeit retrospective, study was recently presented which showed good procedural and clinical success for PFO closure for this indication. We present a case of acute right to left intra-cardiac shunt across PFO where the shunting is not persistent. Hence making a decision on PFO closure based on the aforementioned promising trial may not have been the right decision for the patient. This case high...

  15. Highlights in the studies of the relationship of geomagnetic field changes to auroral luminosity

    International Nuclear Information System (INIS)

    In the middle of the 18th century Celsius observed that there was a correspondence between a great aurora in Europe and the extreme motion of his observed compass needle. By the nineteenth century it was well established that the geomagnetic field always fluctuated violently at the height of an auroral display, that the high latitude zones of peak field disturbance and luminosity and similar locations, and that there were concurrent solar cycle changes in activity levels for the two phenomena. After the International Geophysical Year of 1957 to 1959 the correspondence of the ionospheric electrojet currents and auroral forms became a focus of observational programs. In these recent times the studies of a relationship between short-period pulsations of the geomagnetic field and luminosity pulsations (or the pulsations of bombarding, low energy electrons causing the auroral intensity changes) appeared prominently in the literature. A summary of the scientific progress in the study of these phenomena is presented in this paper. (author)

  16. Nonlinear interactions of electromagnetic waves with the auroral ionosphere

    International Nuclear Information System (INIS)

    The ionosphere provides us with an opportunity to perform plasma experiments in an environment with long confinement times, very large-scale lengths, and no confining walls. The auroral ionosphere with its nearly vertical magnetic field geometry is uniquely endowed with large amount of free energy from electron and ion precipitation along the magnetic field and mega-ampere current across the magnetic field. To take advantage of this giant outdoor laboratory, two facilities HAARP and HIPAS, with frequencies ranging from the radio to optical bands, are now available for active probing of and interaction with this interesting region. The ponderomotive pressures from the self-consistent wave fields have produced significant local perturbations of density and particle distributions at heights where the incident EM frequency matches a plasma resonance. This paper will review theory and experiments covering the nonlinear phenomena of parametric decay instability to wave collapse processes. At HF frequencies plasma lenses can be created by preconditioning pulses to focus what is a normally divergent beam into a high-intensity spot to further enhance nonlinear phenomena. At optical wavelengths a large rotating liquid metal mirror is used to focus laser pulses up to a given height. Such laser pulses are tuned to the same wavelengths of selected atomic and molecular resonances, with resulting large scattering cross sections. Ongoing experiments on dual-site experiments and excitation of ELF waves will be presented. The connection of such basic studies to environmental applications will be discussed. Such applications include the global communication using ELF waves, the ozone depletion and remediation and the control of atmospheric CO2 through the use of ion cyclotron resonant heating

  17. Current-voltage relationship in the auroral particle acceleration region

    Directory of Open Access Journals (Sweden)

    M. Morooka

    2004-11-01

    Full Text Available The current-voltage relationship in the auroral particle acceleration region has been studied statistically by the Akebono (EXOS-D satellite in terms of the charge carriers of the upward field-aligned current. The Akebono satellite often observed field-aligned currents which were significantly larger than the model value predicted by Knight (1973. We compared the upward field-aligned current estimated by three different methods, and found that low-energy electrons often play an important role as additional current carriers, together with the high-energy primary electrons which are expected from Knight's relation. Such additional currents have been observed especially at high and middle altitudes of the particle acceleration region. Some particular features of electron distribution functions, such as "cylindrical distribution functions" and "electron conics", have often been observed coinciding with the additional currents. They indicated time variability of the particle acceleration region. Therefore, we have concluded that the low-energy electrons within the "forbidden" region of electron phase space in the stationary model often contribute to charge carriers of the current because of the rapid time variability of the particle acceleration region. "Cylindrical distribution functions" are expected to be found below the time-varying potential difference. We statistically examined the locations of "cylindrical distribution function", and found that their altitudes are related to the location where the additional currents have been observed. This result is consistent with the idea that the low-energy electrons can also carry significant current when the acceleration region changes in time.

  18. Nonlinear interactions of electromagnetic waves with the auroral ionosphere

    Science.gov (United States)

    Wong, Alfred Y.

    1999-09-01

    The ionosphere provides us with an opportunity to perform plasma experiments in an environment with long confinement times, very large-scale lengths, and no confining walls. The auroral ionosphere with its nearly vertical magnetic field geometry is uniquely endowed with large amount of free energy from electron and ion precipitation along the magnetic field and mega-ampere current across the magnetic field. To take advantage of this giant outdoor laboratory, two facilities HAARP and HIPAS, with frequencies ranging from the radio to optical bands, are now available for active probing of and interaction with this interesting region. The ponderomotive pressures from the self-consistent wave fields have produced significant local perturbations of density and particle distributions at heights where the incident EM frequency matches a plasma resonance. This paper will review theory and experiments covering the nonlinear phenomena of parametric decay instability to wave collapse processes. At HF frequencies plasma lenses can be created by preconditioning pulses to focus what is a normally divergent beam into a high-intensity spot to further enhance nonlinear phenomena. At optical wavelengths a large rotating liquid metal mirror is used to focus laser pulses up to a given height. Such laser pulses are tuned to the same wavelengths of selected atomic and molecular resonances, with resulting large scattering cross sections. Ongoing experiments on dual-site experiments and excitation of ELF waves will be presented. The connection of such basic studies to environmental applications will be discussed. Such applications include the global communication using ELF waves, the ozone depletion and remediation and the control of atmospheric CO2 through the use of ion cyclotron resonant heating.

  19. THEMIS ground-space observations during the development of auroral spirals

    Directory of Open Access Journals (Sweden)

    A. Keiling

    2009-11-01

    Full Text Available A simultaneous observation of an auroral spiral and its generator region in the near-Earth plasma sheet is rather unlikely. Here we present such observations using the THEMIS spacecraft as well as the THEMIS ground network of all-sky imagers and magnetometers. Two consecutive auroral spirals separated by approximately 14 min occurred during a substorm on 19 February 2008. The spirals formed during the expansion phase and a subsequent intensification, and were among the brightest features in the aurora with diameters of 200–300 km. The duration for the formation and decay of each spiral was less than 60 s. Both spirals occurred shortly after the formation of two oppositely rotating plasma flow vortices in space, which were also accompanied by dipolarizations and ion injections, at ~11 RE geocentric distance. Observations and model calculations also give evidence for a magnetic-field-aligned current generation of approximately 0.1 MA via the flow vortices, connecting the generator region of the spirals with the ionosphere, during the formation of both spirals. In the ionosphere, a pair of equivalent ionospheric current (EIC vortices with opposite rotations (corresponding to upward and downward currents was present during both auroral spirals with enhanced EICs and ionospheric flows at the locations of the auroral spirals and along the auroral arcs. The combined ground and space observations suggest that each auroral spiral was powered by two oppositely rotating plasma flow vortices that caused a current enhancement in the substorm current wedge.

  20. Auroral physics at Jupiter: Outstanding issues to be addressed by Juno

    Science.gov (United States)

    Kurth, W. S.; Connerney, J. E. P.; McComas, D. J.; Mauk, B. H.; Gladstone, R.; Adriani, A.; Bagenal, F.; Bolton, S. J.

    2015-10-01

    Juno is on course to enter polar orbit at Jupiter on July 4, 2016. After a small number of preliminary orbits during which the orbital period is reduced, approximately 30 science orbits will be executed to explore the interior of Jupiter, hence, its origin. A second primary objective of the mission, and the subject of this talk, is to carry out the first exploration of Jupiter's polar magnetosphere with an emphasis on the physics of the Jovian aurora. All previous missions to Jupiter, including Ulysses, remained at low Jovian latitudes at close range, hence, our knowledge of Jupiter's polar magnetosphere and, in particular auroral processes, is a composite of remote sensing (such as radio emissions in the hectometric and decametric bands as well as IR and UV images); application of observations of Earth's auroral and polar cap particles, fields, and auroral emissions; and modeling. While these likely inform our expectations of what Juno will actually measure qualitatively, Juno will provide the first in depth exploration of auroral processes at another planet, other than a small number of very brief encounters of Saturn's kilometric radio source region by Cassini. With a reasonably complete suite of in situ magnetospheric measurements coupled with remote sensing, Juno will enable us to compare the physics of Jupiter's polar magnetosphere with those expectations. Certainly, understanding the nature of auroral currents and mechanisms for particle acceleration are high on the list of priorities for these studies. In addition, it is expected that Juno will greatly improve our understanding of the mapping of auroral processes from high latitudes and low altitudes to the middle and outer magnetosphere.

  1. The optical manifestation of dispersive field-aligned bursts in auroral breakup arcs

    Science.gov (United States)

    Dahlgren, H.; Semeter, J. L.; Marshall, R. A.; Zettergren, M.

    2013-07-01

    High-resolution optical observations of a substorm expansion show dynamic auroral rays with surges of luminosity traveling up the magnetic field lines. Observed in ground-based imagers, this phenomenon has been termed auroral flames, whereas the rocket signatures of the corresponding energy dispersions are more commonly known as field-aligned bursts. In this paper, observations of auroral flames obtained at 50 frames/s with a scientific-grade Complementary Metal Oxide Semiconductor (CMOS) sensor (30° × 30° field of view, 30 m resolution at 120 km) are used to provide insight into the nature of the precipitating electrons similar to high-resolution particle detectors. Thanks to the large field of view and high spatial resolution of this system, it is possible to obtain a first-order estimate of the temporal evolution in altitude of the volume emission rate from a single sensor. The measured volume emission rates are compared with the sum of modeled eigenprofiles obtained for a finite set of electron beams with varying energy provided by the TRANSCAR auroral flux tube model. The energy dispersion signatures within each auroral ray can be analyzed in detail during a fraction of a second. The evolution of energy and flux of the precipitation shows precipitation spanning over a large range of energies, with the characteristic energy dropping from 2.1 keV to 0.87 keV over 0.2 s. Oscillations at 2.4 Hz in the magnetic zenith correspond to the period of the auroral flames, and the acceleration is believed to be due to Alfvenic wave interaction with electrons above the ionosphere.

  2. Plasma sheet fast flows and auroral dynamics during substorm: a case study

    Directory of Open Access Journals (Sweden)

    N. L. Borodkova

    Full Text Available Interball-1 observations of a substorm development in the mid-tail on 16 December 1998 are compared with the auroral dynamics obtained from the Polar UV imager. Using these data, the relationship between plasma flow directions in the tail and the location of the auroral activation is examined. Main attention is given to tailward and earth-ward plasma flows, interpreted as signatures of a Near Earth Neutral Line (NENL. It is unambiguously shown that in the mid-plasma sheet the flows were directed tailward when the auroral bulge developed equatorward of the spacecraft ionospheric footprint. On the contrary, when active auroras moved poleward of the Interball-1 projection, earthward fast flow bursts were observed. This confirms the concept that the NENL (or flow reversal region is the source of auroras forming the poleward edge of the auroral bulge. The observed earthward flow bursts have all typical signatures of Bursty Bulk Flows (BBFs, described by Angelopolous et al. (1992. These BBFs are related to substorm activations starting at the poleward edge of the expanded auroral bulge. We interpret the BBFs as a result of reconnection pulses occurring tail-ward of Interball-1. In addition, some non-typically observed phenomena were detected in the plasma sheet during this substorm: (i tailward/earthward flows were superimposed on a very strong duskward flow, and (ii wavy structures of both magnetic field and plasma density were registered. The latter observation is probably linked to the filamentary structure of the current sheet.

    Key words. Magnetospheric physics (auroral phenomena; plasma sheet; storms and substorms

  3. Dengue infection as a potential trigger of an imported Plasmodium ovale malaria relapse or a long incubation period in a non-endemic malaria region

    OpenAIRE

    Otília Lupi; Felipe Ridolfi; Sidnei da Silva; Graziela Maria Zanini; Aline Lavigne; Rita Maria Ribeiro Nogueira; Maria de Fátima Ferreira da Cruz; Cláudio Tadeu Daniel-Ribeiro; Patrícia Brasil

    2016-01-01

    Objectives: To report that dengue fever (DF) could have triggered Plasmodium ovale wallikeri malaria. Methods: A retrospective case report of P. ovale malaria and DF in a single patient in Rio de Janeiro, Brazil, who had lived in Angola, is presented. Results: On the second week of illness, the patient was referred to our research service. As symptoms had persisted up to day 14, malaria was also considered, based on the patient's long-standing epidemiological history. On day 16 of illne...

  4. Prospect of China's Auroral Fine-structure Imaging System (CAFIS) at Zhongshan station in Antarctica

    Institute of Scientific and Technical Information of China (English)

    LIU Shun-lin; HAN De-sheng; HU Hong-qiao; HUANG De-hong; ZHANG Bei-chen; YANG Hui-gen

    2008-01-01

    A new auroral imaging system is reported which is planned to be deployed at Zhongshan Station in Antarctica in the end of 2009. The system will focus on study of optical auroras in small scales and be called China' s Auroral Fine-structure Imaging System (CAFIS). The project of CAFIS is carried out by support of 'the tenth five-year plan for capacity building' of China. CAFIS will be a powerful groundbased platform for aurora observational experiments. Composing and advantages of CAFIS are introduced in this brief report. Some potential study topics involved CAFIS are also considered.

  5. Auroral spectrograph data annals of the international geophysical year, v.25

    CERN Document Server

    Carrigan, Anne; Norman, S J

    1964-01-01

    Annals of the International Geophysical Year, Volume 25: Auroral Spectrograph Data is a five-chapter text that contains tabulations of auroral spectrograph data. The patrol spectrograph built by the Perkin-Elmer Corporation for the Aurora and Airglow Program of the IGY is a high-speed, low-dispersion, automatic instrument designed to photograph spectra of aurora occurring along a given magnetic meridian of the sky. Data from each spectral frame were recorded on an IBM punched card. The data recorded on the cards are printed onto the tabulations in this volume. These tabulations are available

  6. Generation of radiation at combination frequencies in the region of the auroral electric jet

    Energy Technology Data Exchange (ETDEWEB)

    Kapustin, I.N.; Pertsovskii, R.A.; Vasil' ev, A.N.; Smirnov, V.S.; Raspopov, O.M.; Solov' eva, L.E.; Ul' yachenko, A.A.; Arykov, A.A.; Galakhova, N.V.

    1977-03-05

    An experiment was performed aimed at recording radiation at combination frequencies when the ionosphere is acted upon, by high-power amplitude-modulated short-wave radio emission in the region of the auroral electric jet. It is found that the intensity of the radiation at the combination frequency depends on the distance between the auroral current jet from the center of the zone of the active action in the ionosphere, as well as on the strength of the current in the electric jet.

  7. Determination of collapse loads in pipe bends with ovality and variable wall thickness under internal pressure and in-plane opening moment

    International Nuclear Information System (INIS)

    The combined effect of ovality and variable wall thickness on collapse load of pipe bends under in-plane opening bending moment with internal pressure was investigated using finite element limit analysis considering large geometric change effect. The material was assumed to be elastic–perfectly plastic. The collapse moments were obtained from moment-rotation curves drawn for each bend using twice-elastic-slope method. Thickening/thinning effect on collapse load is very minimal and can be neglected. The effect of ovality is significant with the reduction of collapse load by a maximum of 39.1% for the maximum internal pressure and ovality considered. Based on the finite element results, a mathematical expression is proposed to determine collapse load of the pipe bends with ovality and this equation has been verified with experimental collapse loads. - Highlights: • Shape imperfect pipe bends subject to in-plane bending and internal pressure is studied. • Ovality produces significant effect on collapse moments of pipe bends while thinning has negligible effect. • Based on the FE results, a mathematical expression is proposed to determine collapse load of the pipe bends with ovality

  8. Ex vivo evaluation of three instrumentation techniques on E. faecalis biofilm within oval shaped root canals

    Directory of Open Access Journals (Sweden)

    Vitor Cesar NAKAMURA

    2015-01-01

    Full Text Available The objective of the present study was to assess the effectiveness of reciprocating instrumentation in disinfecting oval-shaped root canals infected with Enterococcus faecalis. Forty-five human lower premolars were infected with a culture of E. faecalis (ATCC 29212 for 28 days. Five other teeth that were neither contaminated nor instrumented were used as controls. The 45 specimens were divided into three experimental groups (n = 15 based on the root canal preparation technique used: manual (K-type, Dentsply Maillefer, Ballaigues, Switzerland; rotary (MTwo, VDW GmbH, Munich, Germany; and reciprocating (Reciproc R50, VDW GmbH, Munich, Germany instruments. During chemomechanical preparation, 21 mL of 2.5% NaOCl was used as the irrigating solution. Microbiological sampling was performed before (S1 and immediately after (S2 the chemomechanical preparation using sterilized paper points. Specimens were then cleaved, and 0.02 g of dentine chips was collected from the root thirds to verify the presence of microorganisms in dentinal tubules. All three preparation techniques reduced the number of microorganisms in the root canal lumen and dentine chips from the root thirds, but no significant differences were observed between the three groups (p > 0.05. Reciprocating instrumentation with Reciproc R50 was effective in reducing the number of microorganisms within the root canal system. Although this technique involves the use of only one file to perform the root canal therapy, it is as effective as conventional rotary instrumentation in reducing theE. faecalis biofilm from the root canal system. However, further clinical investigations are warranted in order to ratify these results.

  9. Pathophysiology of inner ear decompression sickness: potential role of the persistent foramen ovale.

    Science.gov (United States)

    Mitchell, Simon J; Doolette, David J

    2015-06-01

    Inner-ear decompression sickness (inner ear DCS) may occur in isolation ('pure' inner-ear DCS), or as part of a multisystem DCS presentation. Symptoms may develop during decompression from deep, mixed-gas dives or after surfacing from recreational air dives. Modelling of inner-ear inert gas kinetics suggests that onset during decompression results from supersaturation of the inner-ear tissue and in-situ bubble formation. This supersaturation may be augmented by inert gas counterdiffusion following helium to nitrogen gas switches, but such switches are unlikely, of themselves, to precipitate inner-ear DCS. Presentations after surfacing from air dives are frequently the 'pure' form of inner ear DCS with short symptom latency following dives to moderate depth, and the vestibular end organ appears more vulnerable than is the cochlea. A large right-to-left shunt (usually a persistent foramen ovale) is found in a disproportionate number of cases, suggesting that shunted venous gas emboli (VGE) cause injury to the inner-ear. However, this seems an incomplete explanation for the relationship between inner-ear DCS and right-to-left shunt. The brain must concomitantly be exposed to larger numbers of VGE, yet inner-ear DCS frequently occurs in the absence of cerebral symptoms. This may be explained by slower inert gas washout in the inner ear than in the brain. Thus, there is a window after surfacing within which VGE arriving in the inner-ear (but not the brain) would grow due to inward diffusion of supersaturated inert gas. A similar difference in gas kinetics may explain the different susceptibilities of cochlear and vestibular tissue within the inner-ear itself. The cochlea has greater perfusion and a smaller tissue volume, implying faster inert gas washout. It may be susceptible to injury by incoming arterial bubbles for a shorter time after surfacing than the vestibular organ. PMID:26165533

  10. Patent foramen ovale closure in over-60-years old patients with diastolic dysfunction

    Institute of Scientific and Technical Information of China (English)

    Gianluca Rigatelli; Fabio Dell'Avvocata; Patio Cardaioli; Massimo Giordan; Gabriele Braggion; Loris Roncon

    2008-01-01

    Background Patent foramen ovale (PFO)-related stroke is a possible and not easily manageable occurrence in ≤60-years-old patients due to the presence of different comorbidities and in particular of diastolic dysfunction which is considered as a contraindication to PFO closure.The grade of diastolic dysfunction for which PFO closure is contraindicated and whether there are changes in diastolic dysfunction class after closure have not been investigated in deep yet.Methods We prospectively enrolled patients who were referred to our centre over a 12 months period for PFO transcatheter closure having echocardiographic demonstration of diastolic dysfunction (≤Ⅲ class diastolic dysfunction).Echocardiography was scheduled at 1,6 and 12 months in order to assess changes in haemodynamic parameters of left ventricle function.Results Thirteen out of 80 patients referred to our centre (16.2%,mean age 65 + 6.4 years) over a 24-month period were enrolled in the study (Table 1).Eighteen Amplatzer PFO Occluder 25 mm and one 35 mm,two Amplatzer 25/25 mm Cribriform Occluder and two 25 nun Premere Occlusion System were successfully implanted with no intraoperative complications.As collateral findings on ICE 8/12 patients (66.7 %) had hypertrophy of the interatrial septum (thickness of the rims > 1.2 mm) probably imputable to hypertensive cardiomyopathy.Four patients developed atrial fibrillation during the first month post-implantation,all successfully treated with antiarrhythmic drugs.After a mean follow-up of 40±4.3 months left ventricle performance indices (ejection fraction and end-diastolic volume) and diastolic dysfunction parameters (E/A,deceleration time,diastolic dysfunction class) did not change significantly.Conclusion The present study suggests that PFO transcatheter closure may be safely performed in aged patients with diastolic dysfunction class 1-2.(J Geriatr Cardio12008;5:3-6.)

  11. Local Heat Transfer for Finned-Tube Heat Exchangers using Oval Tubes

    Energy Technology Data Exchange (ETDEWEB)

    O' Brien, James Edward; Sohal, Manohar Singh

    2000-08-01

    This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with either a circular tube or an elliptical tube in crossflow. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.56 x 10-3 to 15.6 x 10-3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 630 – 6300 with a duct height of 1.106 cm and a duct width-toheight ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. The elliptical tube had an aspect ratio of 3:1 and a/H equal to 4.33. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of circular and oval tubes and their relationship to the complex horseshoe vortex system that forms in the flow stagnation region. Fin surface stagnation-region Nusselt numbers are shown to be proportional to the square-root of Reynolds number.

  12. Antiplatelet effects of clopidogrel and aspirin after interventional patent foramen ovale/ atrium septum defect closure.

    Science.gov (United States)

    Polzin, Amin; Dannenberg, Lisa; Sophia Popp, Valérie-; Kelm, Malte; Zeus, Tobias

    2016-06-01

    The optimal antiplatelet therapy after patent foramen ovale (PFO)/ atrium septum defect (ASD) closure is a matter of discussion. It is challenging as inter-individual responses to antiplatelet medication vary significantly and common complications are bleeding and ischemic events. In this study, we aimed to analyze the incidence of high on-treatment platelet reactivity (HTPR) to antiplatelet medication in patients undergoing PFO/ASD closure as well as clinical complications and thrombus formation on the occluder during six-month follow-up. This hypothesis generating pilot study was observed, which included 140 patients undergoing PFO/ASD closure. The primary endpoint was pharmacodynamic response to antiplatelet medication. A composite of death, myocardial infarction, bleeding, stroke and thrombus formation on the occluder during six-month follow-up was the secondary endpoint. HTPR to clopidogrel was analyzed using the vasodilator-stimulated protein phosphorylation (VASP), HTPR to aspirin by light-transmission aggregometry (LTA). In 71% of patients HTPR to clopidogrel was detected, HTPR to aspirin in only 4%. We observed 12 complications, 9 bleeding events (including 3 major bleeding events) and 3 transient ischemic attacks. No stroke and no thrombus formation on the occluder occurred. The primary endpoint was not associated with the secondary endpoint. The incidence of HTPR to clopidogrel in PFO/ASD closure patients is very high. Despite this high incidence, no stroke or thrombus formation on the occluder occurred at all. This leads to the hypothesis, that the benefit of additional clopidogrel medication is questionable and has to be investigated in large-scale clinical trials. PMID:26556101

  13. Effect of body position and oxygen tension on foramen ovale recruitment.

    Science.gov (United States)

    Moses, Kayla L; Beshish, Arij G; Heinowski, Nicole; Baker, Kim R; Pegelow, David F; Eldridge, Marlowe W; Bates, Melissa L

    2015-01-01

    While there is an increased prevalence of stroke at altitude in individuals who are considered to be low risk for thrombotic events, it is uncertain how venous thrombi reach the brain. The patent foramen ovale (PFO) is a recruitable intracardiac shunt between the right and left atrium. We aimed to determine whether body position and oxygen tension affect blood flow through the PFO in healthy adults. We hypothesized that hypoxia and body positions that promote right atrial filling would independently recruit the PFO. Subjects with a PFO (n = 11) performed 11 trials, combining four different fractions of inhaled oxygen (FiO₂) (1.0, 0.21, 0.15, and 0.10) and three positions (upright, supine, and 45° head down), with the exception of FiO₂ = 0.10, while 45° head down. After 5 min in each position, breathing the prescribed oxygen tension, saline bubbles were injected into an antecubital vein and a four-chamber echocardiogram was obtained to evaluate PFO recruitment. We observed a high incidence of PFO recruitment in all conditions, with increased recruitment in response to severe hypoxia and some contribution of body position at moderate levels of hypoxia. We suspect that increased pulmonary vascular pressure, secondary to hypoxia-induced pulmonary vasoconstriction, increased right atrial pressure enough to recruit the PFO. Additionally, we hypothesize that the minor increase in breathing resistance that was added by the mouthpiece, used during experimental trials, affected intrathoracic pressure and venous return sufficiently to recruit the PFO. PMID:25394826

  14. Solar and auroral evidence for an intense recurrent geomagnetic storm during December in AD 1128

    Directory of Open Access Journals (Sweden)

    D. M. Willis

    Full Text Available The earliest known drawing of sunspots appears in The Chronicle of John of Worcester, which was compiled in the first half of the twelfth century. In this medieval chronicle, the Latin text describing the sunspots is accompanied by a colourful drawing, albeit idealised, which shows the apparent positions and sizes of two sunspots on the solar disk. The date of this observation of sunspots from Worcester, England is firmly established as AD 1128 December 8. Assuming that the drawing was prepared fairly carefully, the angular diameters of the two sunspots are at least about 3 arcmin and 2 arcmin in the northern and southern hemispheres, respectively. Similarly, the heliographic latitudes of both sunspots are within the approximate range of 25°–35°. About five days after this observation of sunspots on the solar disk, on the night of AD 1128 December 13, a red auroral display was observed from Songdo, Korea (the modern city of Kaesong. This auroral observation was recorded in the Koryo-sa, the official Korean chronicle of the period. In addition, five Chinese and five Korean descriptions of auroral displays were recorded in various East-Asian histories between the middle of AD 1127 and the middle of AD 1129. The ten oriental auroral records in this particular interval correspond to six distinct auroral events, which provide evidence for recurrent, though possibly intermittent, auroral activity on a timescale almost exactly equal to the synodic-solar-rotation period (approximately 27 days. The six distinct auroral events were apparently associated with two series of recurrent geomagnetic storms, both of which were sufficiently intense to produce mid-latitude auroral displays in East Asia. These ancient solar and auroral observations are interpreted in terms of present-day understanding of solar-terrestrial physics. Con-temporary ground-based and satellite measurements during the last few decades have indicated that recurrent

  15. Auroral research at the Tromsø Northern Lights Observatory: the Harang directorship, 1928-1946

    Science.gov (United States)

    Egeland, Alv; Burke, William J.

    2016-03-01

    The Northern Lights Observatory in Tromsø began as Professor Lars Vegard's dream for a permanent facility in northern Norway, dedicated to the continuous study of auroral phenomenology and dynamics. Fortunately, not only was Vegard an internationally recognized spectroscopist, he was a great salesman and persuaded the Rockefeller Foundation that such an observatory represented an important long-term investment. A shrewd judge of talent, Vegard recognized the scientific and managerial skills of Leiv Harang, a recent graduate from the University of Oslo, and recommended that he become the observatory's first director. In 1929, subsequent to receiving the Rockefeller Foundation grant, the University of Oslo established a low temperature laboratory to support Vegard's spectroscopic investigations. This paper follows the scientific accomplishments of observatory personnel during the 18 years of Harang's directorship. These include: identifying the chemical sources of auroral emissions, discovering the Vegard-Kaplan bands, quantifying height distributions of different auroral forms, interpreting patterns of magnetic field variations, remotely probing auroral electron distribution profiles in the polar ionosphere, and monitoring the evolving states of the ozone layer. The Rockefeller Foundation judges got it right: the Tromsø Nordlysobservatoriet was, and for decades remained, an outstanding scientific investment.

  16. Auroral boundary dynamics observed simultaneously from the Viking spacecraft and from the ground

    International Nuclear Information System (INIS)

    High spatial and temporal resolution auroral imaging from space and from the ground contiues to improve our understanding of auroral dynamics. The ultraviolet imager on the Viking spacecraft gives global information on the activity of the auroral distribution. The ground-based optical facility at Swedish Institute of Space Physics, in Kiruna, Sweden, gives information on the finer-scale auroral structure. Simultaneous satellite- and ground-based measurements using this instrumentation were obtained for three selected events during the spring of 1986. For some aspects the authors find a remarkable correspondence of particular features observed from space and from the ground. For others the different views are complementary in nature. Taken together, they provide a comprehensive picture of presubstorm, substorm, and postsubstorm dynamics. The major findings are (1) a narrow active rayed arc set within a background of softer precipitation that defines what is generally called the diffuse aurora, with repeated fading on the time scale of 5 min; (2) a period of rapid convection manifested by the disappearance of transpolar arcs and the onset of undulations of the poleward boundary arc observed well before substorm onset; and (3) two clearly separated latitudinal regions following substorm onset, the poleward one being more variable on a time scale of 10 min, but the equatorward one having at its equatorward boundary a coherent pulsating feature with periods in the range 1-3 min

  17. Characterization of a Penning discharge for investigation of auroral radio wave generation mechanisms

    International Nuclear Information System (INIS)

    Auroral Kilometric Radiation (AKR), observed by satellites in the Earth's magnetosphere, is naturally generated in regions of partial plasma depletion (auroral density cavity) in the polar magnetosphere at approximately 3200 km altitude. As an electron descends through these regions of partial plasma depletion along magnetic field lines towards the Earth's ionosphere, the field lines increases and, through conservation of the magnetic moment, the electron gives up axial velocity in favour of perpendicular velocity. This results in a horseshoe-shaped distribution function in parallel/perpendicular-velocity space which is unstable to X-mode radiation, near the cyclotron frequency. Power levels as high as GW levels have been recorded with frequencies around 300 kHz. The background plasma frequency within the auroral density cavity is approximately 9 kHz corresponding to a plasma density 1 cm−3. A laboratory experiment scaled from auroral frequency to microwave frequency has previously been reported. Here, the addition of a Penning trap to simulate the background plasma of the density cavity is reported, with measurements ne ∼ 2 × 1014–2.17 × 1015 m−3, fpe ∼ 128–418 MHz and fce ∼ 5.21 GHz giving a ratio of ωce/ωpe comparable to the magnetospheric AKR source region.

  18. Small-scale structure of the auroral electron and ion acceleration mechanisms

    International Nuclear Information System (INIS)

    High time resolution data obtained from sounding rocket flights reaching altitudes of 1,000 km now permit spatial measurements on the order of the particle gyrodiameters. The electron precipitation responsible for the auroral light emission has two distinct populations; the isotropic in pitch angle electrons that apparently have a magnetospheric source and have been further accelerated within one or two Re of the ionosphere, and, a very field-aligned component which is cold and apparently has an ionospheric source. The field-aligned component provides much of the fine structure and dynamic motion of the visual aurora. Time dispersion of these electrons also places their acceleration region one to two Re from the ionosphere. Much of the heavy ion population of the trapped radiation comes from the ionosphere. These ions apparently receive their initial acceleration transverse to B at altitudes on the order of 1,000 km during auroral events and then are further accelerated as they pass through the higher altitude auroral acceleration region. Recent measurements show that the volume of transverse ion acceleration can be as small as several tens of meters transverse to B and arc also volumes of ionospheric density depletion and intense waves near the lower hybrid frequency having electric field amplitudes of hundreds of mv/m. These regions of microscale transverse ion acceleration are generally co-located with the auroral field-aligned electron bursts

  19. Phenomenological analysis of Jovian north auroral H2 Lyman band emissions

    International Nuclear Information System (INIS)

    Low-dispersion spectra taken with the IUE SWP from 1981-88 are examined for gross longitudinal features in Jovian north auroral emission activity and for evidence of long-term trends in auroral characteristics. Integrated photon flux in the H2 Lyman-band region is extracted from each of the spectra, characterizing auroral emission strength at time of exposure. A plot of flux vs. Jovian central meridian longitude (System III) corroborates an enhanced emission region centered at about 1800 reported by Skinner et al., (1984). Curves fit to fluxes grouped as ''scans'' (consecutive exposures made over a single Jovian rotation) vs. longitude characterize width, position and intensity of the enhanced region. Study includes examination of possible long-term variation in auroral peak intensity and width of the enhanced region vs. time, as well as possible correlation of the light curve integrated over longitude as a measure of total power emitted, vs. the longitudinal position of the intensity peak; more energetic aurorae appear to peak at values of central meridian longitude lower than the previously reported 1800. An analysis is made of longitudinal dependence in the ratio of photon flux in the Lyman and Werner bands, an indicator of primary particle energy

  20. Auroral Current and Electrodynamics Structure Measured by Two SOunding Rockets in Flight Simultaneously

    Science.gov (United States)

    Bounds, Scott R.; Kaeppler, Steve; Kletzing, Craig; Lessard, Marc; Cohen, Ian J.; Jones, Sarah; Pfaff, Robert F.; Rowland, Douglas E.; Anderson, Brian Jay; Gjerloev, Jesper W.; Labelle, James W.; Dombrowski, Micah P.; Dudok de Wit, Thierry; Heinselman, Craig J.

    2011-01-01

    On January 29, 2009, two identically instrumented sounding rockets were launched into a sub-storm auroral arc from Poker Flat Alaska. Labeled the Auroral Currents and Electrodynamics Structure (ACES) mission, the payloads were launched to different apogees (approx.350km and approx.120km) and staggered in time so as to optimize their magnetic conjunctions. The different altitudes provided simultaneous in-situ measurements of magnetospheric input and output to the ionosphere and the ionospheric response in the lower F and E region. Measurements included 3-axis magnetic field, 2-axis electric field nominally perpendicular to the magnetic field, energetic particles, electron and ion, up to 15keV, cold plasma temperature and density. In addition, PFISR was also operating in a special designed mode to measure electric field and density profiles in the plane defined by the rocket trajectories and laterally to either side of the trajectories. Observation of the measured currents and electrodynamics structure of the auroral form encountered are presented in the context of standard auroral models and the temporal/spatial limitations of mission designs.

  1. Variation of Jupiter's aurora observed by Hisaki/EXCEED: 2. Estimations of auroral parameters and magnetospheric dynamics

    Science.gov (United States)

    Tao, Chihiro; Kimura, Tomoki; Badman, Sarah V.; André, Nicolas; Tsuchiya, Fuminori; Murakami, Go; Yoshioka, Kazuo; Yoshikawa, Ichiro; Yamazaki, Atsushi; Fujimoto, Masaki

    2016-05-01

    Jupiter's auroral parameters are estimated from observations by a spectrometer EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) on board Japanese Aerospace Exploration Agency's Earth-orbiting planetary space telescope Hisaki. EXCEED provides continuous auroral spectra covering the wavelength range over 80-148 nm from the whole northern polar region. The auroral electron energy is estimated using a hydrocarbon color ratio adopted for the wavelength range of EXCEED, and the emission power in the long wavelength range 138.5-144.8 nm is used as an indicator of total emitted power before hydrocarbon absorption and auroral electron energy flux. The quasi-continuous observations by Hisaki provide the auroral electron parameters and their relation under different auroral activity levels. Short- (within one planetary rotation) enhancements of auroral power accompany increases of the electron number flux rather than the electron energy variations. The relationships between the auroral electron energy (~70-400 keV) and flux (1026-1027/s, 0.08-0.9 μA/m2) estimated from the observations over a 40 day interval are in agreement with field-aligned acceleration theory when incorporating probable magnetospheric parameters. Applying the electron acceleration theory to each observation point, we explore the magnetospheric source plasma variation during these power-enhanced events. Possible scenarios to explain the derived variations are (i) an adiabatic variation of the magnetospheric plasma under a magnetospheric compression and/or plasma injection, and (ii) a change of the dominant auroral component from the main emission (main aurora) to the emission at the open-closed boundary.

  2. Vitamin K2-enhanced liver regeneration is associated with oval cell expansion and up-regulation of matrilin-2 expression in 2-AAF/PH rat model.

    Science.gov (United States)

    Lin, M; Sun, P; Zhang, G; Xu, X; Liu, G; Miao, H; Yang, Y; Xu, H; Zhang, L; Wu, P; Li, M

    2014-03-01

    Normal liver has a great potential of regenerative capacity after partial hepatectomy. In clinic, however, most patients receiving partial hepatectomy are usually suffering from chronic liver diseases with severely damaged hepatocyte population. Under these conditions, activation of hepatic progenitor cell (oval cell in rodents) population might be considered as an alternative mean to enhance liver functional recovery. Vitamin K2 has been shown to promote liver functional recovery in patients with liver cirrhosis. In this study, we explored the possibility of vitamin K2 treatment in activating hepatic oval cell for liver regeneration with the classic 2-acetamido-fluorene/partial hepatectomy (2-AAF/PH) model in Sprague-Dawley rats. In 2-AAF/PH animals, vitamin K2 treatment induced a dose-dependent increase of liver regeneration as assessed by the weight ratio of remnant liver versus whole body and by measuring serum albumin level. In parallel, a drastic expansion of oval cell population as assessed by anti-OV6 and anti-CK19 immunostaining was noticed in the periportal zone of the remnant liver. Since matrilin-2 was linked to oval cell proliferation and liver regeneration after partial hepatectomy, we assessed its expression at both the mRNA and protein levels. The results revealed a significant increase after vitamin K2 treatment in parallel with the expansion of oval cell population. Consistently, knocking down matrilin-2 expression in vivo largely reduced vitamin K2-induced liver regeneration and oval cell proliferation in 2-AAF/PH animals. In conclusion, these data suggest that vitamin K2 treatment enhances liver regeneration after partial hepatectomy, which is associated with oval cell expansion and matrilin-2 up-regulation. PMID:24236453

  3. Lower thermospheric wind variations in auroral patches during the substorm recovery phase

    Science.gov (United States)

    Oyama, Shin-ichiro; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Hosokawa, Keisuke; Watkins, Brenton J.; Kurihara, Junichi; Tsuda, Takuo T.; Fallen, Christopher T.

    2016-04-01

    Measurements of the lower thermospheric wind with a Fabry-Perot interferometer (FPI) at Tromsø, Norway, found the largest wind variations in a night during the appearance of auroral patches at the substorm recovery phase. Taking into account magnetospheric substorm evolution of plasma energy accumulation and release, the largest wind amplitude at the recovery phase is a fascinating result. The results are the first detailed investigation of the magnetosphere-ionosphere-thermosphere coupled system at the substorm recovery phase using comprehensive data sets of solar wind, geomagnetic field, auroral pattern, and FPI-derived wind. This study used three events in November 2010 and January 2012, particularly focusing on the wind signatures associated with the auroral morphology, and found three specific features: (1) wind fluctuations that were isolated at the edge and/or in the darker area of an auroral patch with the largest vertical amplitude up to about 20 m/s and with the longest oscillation period about 10 min, (2) when the convection electric field was smaller than 15 mV/m, and (3) wind fluctuations that were accompanied by pulsating aurora. This approach suggests that the energy dissipation to produce the wind fluctuations is localized in the auroral pattern. Effects of the altitudinal variation in the volume emission rate were investigated to evaluate the instrumental artifact due to vertical wind shear. The small electric field values suggest weak contributions of the Joule heating and Lorentz force processes in wind fluctuations. Other unknown mechanisms may play a principal role at the recovery phase.

  4. Energy deposition and non-equilibrium infared radiation of energetic auroral electrons

    Science.gov (United States)

    Wu, Yadong; Gao, Bo; Zhu, Guangsheng; Li, Ziguang

    2016-07-01

    Infrared radiation caused by energetic auroral electrons plays an important role in the thermospheric hear budget, and may be seen as background by infrared surveillance sensors. The auroral electron deposition leads to the ionization, excitation, and dissociation of neutral species(N2,O2,and O), and initiates a series of chemical reaction in the upper atmosphere, finally causes the optical emission of infared excited emitters. In this study, the whole progress from the initial auroral electrons energy deposition to the final infrared emissions has been modeled, which including space plasma, atmospheric physical chemistry, and radiative transfer. The initial atmosphere parameters before auroral disturbing are given by MSIS00 model. The primary electron flux at the top of atmosphere is given by a statistical fitting with the sum of three distribution terms, a power law, a Maxwellian and a Guassian. A semi-emprical model is used in the calculation of energy depositon of single primary electron. The total integral ion pairs production rate is obtained after combining with the initial primary electron flux. The production rate and flux of secondary electrons are modeled with a continuous slow down approximation, using different excitation, ionization, dissociation cross sections of N2, O2, and O to electrons. The photochemical reactions with auroral disturbance is analysed, and its calculation model is established. A "three-step" calculation method is created to obtain number densities of eleven species in the hight between 90-160 km, which containing N2+, O2+, O+, O2+(a4Π), O+(2D), O+(2P), N2(A3Σ), N(2D), N(4S), NO+, and N+. Number densities of different vibraional levels of NO and NO+ are got with steady state assumption, considering 1-12 vibrational levels of NO and 1-14 vibrational levels of NO+. The infared emissions and the spectral lines of the two radiating bodies are calculated with a fuzzy model of spectral band.

  5. Substorm associated radar auroral surges: a statistical study and possible generation model

    Directory of Open Access Journals (Sweden)

    B. A. Shand

    Full Text Available Substorm-associated radar auroral surges (SARAS are a short lived (15–90 minutes and spatially localised (~5° of latitude perturbation of the plasma convection pattern observed within the auroral E-region. The understanding of such phenomena has important ramifications for the investigation of the larger scale plasma convection and ultimately the coupling of the solar wind, magnetosphere and ionosphere system. A statistical investigation is undertaken of SARAS, observed by the Sweden And Britain Radar Experiment (SABRE, in order to provide a more extensive examination of the local time occurrence and propagation characteristics of the events. The statistical analysis has determined a local time occurrence of observations between 1420 MLT and 2200 MLT with a maximum occurrence centred around 1700 MLT. The propagation velocity of the SARAS feature through the SABRE field of view was found to be predominately L-shell aligned with a velocity centred around 1750 m s–1 and within the range 500 m s–1 and 3500 m s–1. This comprehensive examination of the SARAS provides the opportunity to discuss, qualitatively, a possible generation mechanism for SARAS based on a proposed model for the production of a similar phenomenon referred to as sub-auroral ion drifts (SAIDs. The results of the comparison suggests that SARAS may result from a similar geophysical mechanism to that which produces SAID events, but probably occurs at a different time in the evolution of the event.

    Key words. Substorms · Auroral surges · Plasma con-vection · Sub-auroral ion drifts

  6. Nonlinear model of short-scale electrodynamics in the auroral ionosphere

    Directory of Open Access Journals (Sweden)

    J.-M. A. Noël

    Full Text Available The optical detection of auroral subarcs a few tens of m wide as well as the direct observation of shears several m/s per m over km to sub km scales by rocket instrumentation both indicate that violent and highly localized electrodynamics can occur at times in the auroral ionosphere over scales 100 m or less in width. These observations as well as the detection of unstable ion-acoustic waves observed by incoherent radars along the geomagnetic field lines has motivated us to develop a detailed time-dependent two-dimensional model of short-scale auroral electrodynamics that uses current continuity, Ohm's law, and 8-moment transport equations for the ions and electrons in the presence of large ambient electric fields to describe wide auroral arcs with sharp edges in response to sharp cut-offs in precipitation (even though it may be possible to describe thin arcs and ultra-thin arcs with our model, we have left such a study for future work. We present the essential elements of this new model and illustrate the model's usefulness with a sample run for which the ambient electric field is 100 mV/m away from the arc and for which electron precipitation cuts off over a region 100 m wide. The sample run demonstrates that parallel current densities of the order of several hundred µA m-2 can be triggered in these circumstances, together with shears several m/s per m in magnitude and parallel electric fields of the order of 0.1 mV/m around 130 km altitude. It also illustrates that the local ionospheric properties like densities, temperature and composition can strongly be affected by the violent localized electrodynamics and vice-versa.

    Key words: Ionosphere (auroral ionosphere, electric fields and currents, ionosphere-magnetosphere interactions

  7. SA13B-1900 Auroral Charging of the International Space Station

    Science.gov (United States)

    Minow, Joseph I.; Chandler, Michael O.; Wright, Kenneth H., Jr.

    2011-01-01

    Electrostatic potential variations of the International Space Station (ISS) relative to the space plasma environment are dominated by interaction of the negatively grounded 160 volt US photovoltaic power system with the plasma environment in sunlight and inductive potential variations across the ISS structure generated by motion of the vehicle across the Earth's magnetic field. Auroral charging is also a source of potential variations because the 51.6? orbital inclination of ISS takes the vehicle to sufficiently high magnetic latitudes to encounter precipitating electrons during geomagnetic storms. Analysis of auroral charging for small spacecraft or isolated insulating regions on ISS predict rapid charging to high potentials of hundreds of volts but it has been thought that the large capacitance of the entire ISS structure on the order of 0.01 F will limit frame potentials to less than a volt when exposed to auroral conditions. We present three candidate auroral charging events characterized by transient ISS structure potentials varying from approximately 2 to 17 volts. The events occur primarily at night when the solar arrays are unbiased and cannot therefore be due to solar array current collection. ISS potential decreases to more negative values during the events indicating electron current collection and the events are always observed at the highest latitudes along the ISS trajectory. Comparison of the events with integral >30 keV electron flux measurements from NOAA TIROS spacecraft demonstrate they occur within regions of precipitating electron flux at levels consistent with the energetic electron thresholds reported for onset of auroral charging of the DMSP and Freja satellites. In contrast to the DMSP and Freja events, one of the ISS charging events occur in sunlight.

  8. Patent Foramen Ovale in Young Adults with Cryptogenic Stroke or Transient Ischemic Attack

    Directory of Open Access Journals (Sweden)

    Mohsen Mahdinezhad Kashani

    2009-09-01

    Full Text Available Background: Stroke, one of the most important causes of morbidity and mortality in the world, is of great importance in young adults (15-45 years, amongst whom the causes of stroke and transient ischemic attack (TIA are different from those in older ages and a significant portion of them have no known etiology. Patent foramen ovale (PFO is considered a probable cause in this group.Methods: Patients between 15 and 45 years of age with TIA or stroke were examined and evaluated for causes of cerebrovascular accidents. Patients with no definite cause for stroke or TIA, except for PFO, despite our extensive evaluations were categorized as cryptogenic. The controls were comprised of those between 15 and 45 years old who underwent transesophageal echocardiography (TEE for reasons other than stroke. The frequency of PFO and its characteristics were compared between the two groups.Results: The case group comprised 48 patients with cryptogenic stroke (n=31 and TIA (n=17, and the control group consisted of 57 patients. The age distribution of the groups was normal, and there was no significant difference between the age and gender of the two groups. The frequency of PFO in the case and control groups was 52% and 25%, respectively (p value=0.003, odds ratio=3.33, confidence interval=1.46-7.63. The exaggerated motion of the interatrial septum (IAS in the case and control groups was 18.8% and 0%, respectively. Right-to-left shunt at rest in the case and control groups was 78% and 28%, respectively (significant differences. The differences in terms of PFO size, number of bubbles, and atrial septal aneurysm were not significant between the two groups.Conclusion: PFO had a relation with stroke and TIA in the young adults, and right-to-left shunt at rest and exaggerated motion of the IAS could increase the possibility of paradoxical emboli. It seems that the presence of atrial septal aneurysm, number of bubbles, and PFO size did not increase the risk of

  9. A Long-lived and Color Changing Oval on Jupiter's NTrZ (at 19ºN)

    Science.gov (United States)

    Barrado-Izagirre, N.; Legarreta, J.; Sanchez-Lavega, A.; Hueso, R.; Perez-Hoyos, S.; Rojas, J. F.; Mendikoa, I.

    2015-12-01

    A long lived oval located in the boundary between the North Tropical Zone and the North Equatorial Band (NEBn) of Jupiter at 19º of planetographic latitude is being observed at least since 2008. At this latitude the mean wind profile of the planet provide winds of around 10 m/s [1]. Since 2012 and using the PVOL image database of Jupiter (http://www.pvol.ehu.es/pvol/) we have tracked it observing and characterizing its changes. In this period of time, it has merged with another oval (in February 2013) and it has changed it color from white to red (in September 2013) and again white. We have also performed some EPIC simulations of the merger between both ovals. Thanks to Hubble Space Telescope data in Septembers 2012, we have also been able to measure its internal rotation while it was white, unfortunately this set of images only have observations in the near infrared (F763M) and in the ultraviolet (F275W). And finally, using HST and PlanetCam (a planetary camera developed in our research team) images, we are trying to measure the color and the altitude-opacity indexes [2] to assess the color change it has suffered. Acknowledgements: This work has been funded by the Spanish MICIIN proyect AYA2012-36666 with FEDER support, Grupos Gobierno Vasco IT765-13 and UPV/EHU UFI11/55. [1] García-Melendo & Sanchéz-Lavega., Icarus, 152, 136 (2001). [2] Sánchez-Lavega et al., JGR, 118, 1-21 (2013).

  10. Chamfer machining of oval hole on small end of link by abrasive belt%连杆小端椭圆孔的砂带倒角加工

    Institute of Scientific and Technical Information of China (English)

    王友林; 姜英

    2012-01-01

    分析了连杆小头斜端面上的椭圆孔倒角加工存在的问题,介绍了砂带倒角加工方法及椭圆孔砂带倒角机床的结构与工作原理;在砂带倒角机床上,利用砂带的挠性和卷曲变形,替代加工中刀具或工件沿椭圆的长轴移动的附加运动,工件端面上椭圆孔的棱边在砂带的压力与运动作用下被砂带上的磨料切除,形成倒角平面,实现了椭圆孔的倒角加工.%The chamfer of oval hole on oblique surface of small end of link method presented problems are analyzed, the structure and working principle of oval holes abrasive belt chamfering machine tool are introduced ,on the abrasive belt chamfering machine tool, using of the flexible deformation and curling deformation of abrasive belt method substitute that additional movement of cutting tool or the workpiece along the long axis of oval hole, the edge of oval hole be removed by grinding material on abrasive belt under the influence of movement and pressure, obtain a chamfer plane, achieve chamfer machining of oval hole.

  11. Circularity, Solidity, Axes of a Best Fit Ellipse, Aspect Ratio, and Roundness of the Foramen Ovale: A Morphometric Analysis With Neurosurgical Considerations.

    Science.gov (United States)

    Zdilla, Matthew J; Hatfield, Scott A; McLean, Kennedy A; Cyrus, Leah M; Laslo, Jillian M; Lambert, H Wayne

    2016-01-01

    The structure of the foramen ovale of the sphenoid bone is clinically important, particularly with regard to surgical procedures that cannulate the foramen such as percutaneous trigeminal rhizotomy for the treatment of trigeminal neuralgia, percutaneous biopsy of parasellar lesions, and electroencephalographic analysis of the temporal lobe among patients undergoing selective amygdalohippocampectomy. Differences in the morphology of the foramen ovale (FO) have been reported to contribute to difficulties in the cannulation of the FO. Reports regarding the structure of the FO, however, use subjective and ambiguous descriptions of morphology, including "oval," "truly oval," "elongated oval," "elongated," "semicircular," "almond," "round," "rounded," "slit," "irregular," "D shape," and "pear." Therefore, it is necessary to describe the structure of the FO with reproducible objective morphometric data. This study analyzed 169 foramina to determine normative morphometric shape descriptions of the following: area, perimeter, circularity, solidity, axes of a best fit ellipse, aspect ratio, and roundness. The shape descriptors reported herein may aid in identification and description of structural variation in FO including bony projections encroaching upon the foramina and may improve surgical approaches to transovale cannulation. PMID:26703050

  12. Comparison of transcranial contrast Doppler sonography and transesophageal contrast echocardiography for the detection of patent foramen ovale in young stroke patients.

    Science.gov (United States)

    Job, F P; Ringelstein, E B; Grafen, Y; Flachskampf, F A; Doherty, C; Stockmanns, A; Hanrath, P

    1994-08-15

    The prevalence of a patent foramen ovale was assessed by simultaneously performing transesophageal contrast echocardiography and transcranial contrast Doppler sonography (TCD) in 137 subjects (mean age 36 years) with stroke of unclarified etiology (n = 41), clarified etiology (n = 33), and in normal subjects (n = 63; mean age 32 years). Patent foramen ovale was found significantly more often in patients with unclarified than clarified strokes or in normal subjects (66% vs 33%, or 43%). Massive paradoxical embolism through a patent foramen ovale, identified by TCD, occurred significantly (p < 0.01) more often in patients with unclarified (64%) than clarified (27%) strokes or in normal subjects (3%). However, minimal shunts were typical in normal subjects (79%). Patent foramen ovale was detected indirectly by TCD when calculated on the basis of transesophageal contrast echocardiographic findings (sensitivity 89%, specificity 92%). Thus, TCD reliably detects paradoxical cerebral embolism through a patent foramen ovale, and provides important additional information for evaluating its clinical relevance by semi-quantification of embolic contrast material. PMID:7914717

  13. A study of photopolarimeter system UV absorption data on Jupiter, Saturn, Uranus, and Neptune - Implications for auroral haze formation

    International Nuclear Information System (INIS)

    The present investigation of the dark hazes of Jupiter, Saturn, Uranus, and Neptune on the basis of Voyager 2 UV data notes a geographic correlation between the auroral zones of Jupiter and Saturn and UV-dark polar regions. While the auroral fluxes and penetration depths on Jupiter and Saturn may suffice for a darkening of the polar regions by auroras' action on methane, Uranus and Neptune are found to be bright at all latitudes. In the former case, this brightness is in keeping with auroral electron energies too small to reach the CH4 homopause at which haze production occurs; in the latter case, a UV-dark band exists from 30 deg S to 5 deg N which is probably unrelated to auroral processes. 63 refs

  14. Equatorial ionospheric response to isolated auroral substorms over a solar cycle (1980-85): evidence of longitudinal anomaly

    Science.gov (United States)

    Hajkowicz, L. A.

    1996-09-01

    The equatorial ionospheric response to 228 isolated, rapid-onset auroral substorms (as defined from the auroral electrojet index AE) was found from enhancements of the virtual (minimum) height of the F-region (h(') F) in the declining phase of a solar cycle (1980-85). The responses, found for three longitudinal sectors at the equator: Africa (Ouagadougou and Dakar), Asia (Manila) and America (Huancayo), were compared with the response close to the auroral source region at Yakutsk (northern Siberia). The auroral substorm onsets were centered at 17 and 15 UT at sunspot maximum (1980-82) and minimum (1983-85), preceding by 3-5 h the period of post-sunset height rise in the African sector whereas other sectors were in the early afternoon (Huancayo) and morning (Manila). The African response, particularly at Ouagadougou, was distinctly different from other sectors. In the sunspot maximum years (1980-81) the auroral surges were followed after about 3 h by a sharp depression (h(') Fh(') F=0) in 1982. A response polarity reversal (h(') F>0) was noted in this sector for sunspot minimum (1983-85) when large h(') F enhancements were observed at the sunset region. The responses in the Asian and American sector were positive except for a case in Huancayo when response was negative, following an auroral surge before the sunset at this station. It appears that the aurorally generated large-scale travelling ionospheric disturbances (LSTIDs), which first cause positive height enhancements in a sub-auroral location (Yakutsk), subsequently affect the unstable post-sunset ionosphere in the equatorial Africa.

  15. Equatorial ionospheric response to isolated auroral substorms over a solar cycle (1980−85: evidence of longitudinal anomaly

    Directory of Open Access Journals (Sweden)

    L. A. Hajkowicz

    Full Text Available The equatorial ionospheric response to 228 isolated, rapid-onset auroral substorms (as defined from the auroral electrojet index AE was found from enhancements of the virtual (minimum height of the F-region (∆h$^prime$F in the declining phase of a solar cycle (1980–85. The responses, found for three longitudinal sectors at the equator: Africa (Ouagadougou and Dakar, Asia (Manila and America (Huancayo, were compared with the response close to the auroral source region at Yakutsk (northern Siberia. The auroral substorm onsets were centered at 17 and 15 UT at sunspot maximum (1980–82 and minimum (1983–85, preceding by 3–5 h the period of post-sunset height rise in the African sector whereas other sectors were in the early afternoon (Huancayo and morning (Manila. The African response, particularly at Ouagadougou, was distinctly different from other sectors. In the sunspot maximum years (1980–81 the auroral surges were followed after about 3 h by a sharp depression (∆h$^prime$F<0 in the post-sunset height rise, with a period of little or no response (∆h$^prime$F=0 in 1982. A response polarity reversal (∆h$^prime$F>0 was noted in this sector for sunspot minimum (1983–85 when large h$^prime$F enhancements were observed at the sunset region. The responses in the Asian and American sector were positive except for a case in Huancayo when response was negative, following an auroral surge before the sunset at this station. It appears that the aurorally generated large-scale travelling ionospheric disturbances (LSTIDs, which first cause positive height enhancements in a sub-auroral location (Yakutsk, subsequently affect the unstable post-sunset ionosphere in the equatorial Africa.

  16. Separation of spatial and temporal structure of auroral particle precipitation (Invited)

    Science.gov (United States)

    Boudouridis, A.; Spence, H.

    2013-12-01

    Knowledge of the dominant temporal and spatial scales of auroral features is instrumental in understanding the various mechanisms responsible for auroral particle precipitation. Single spacecraft data suffer from temporal/spatial ambiguity. In an effort to separate the temporal and spatial variations of the aurora, we use electron and ion precipitation data from two co-orbiting satellites, F6 and F8 of the Defense Meteorological Satellite Program (DMSP). The two spacecraft have almost identical polar orbits with a small difference in period. As a result the time difference between the two measurements varies with time. We use two statistical tools in order to determine the most probable lifetimes and spatial dimensions of the prevalent auroral features, Cross Correlation Analysis (CCA) and Cross Spectral Analysis (CSA). The CCA is applied to the magnetic latitude series of electron and ion, integral number and energy fluxes measured by the two DMSP spacecraft. As one spacecraft overtakes the other, the variable time lag between the two measurements results in different cross correlation of the two series. We explore the dependence of this variation on the time lag between the satellites. We find that the electron precipitation exhibits a decreasing correlation between the two spacecraft with increasing time lag, whereas there is only a small similar effect for the ion precipitation data. For the CSA we compute the so-called coherence function as a function of frequency (or inverse wavelength), and hence size of the auroral features. The coherence function is a measure of the stability of auroral features of different sizes. We investigate its variation as a function of the time separation between the two DMSP spacecraft measurements. We show that the coherence function of both electrons and ions remains high for up to 1.5 min spacecraft separations for all features larger than about 100 km in width. For smaller features the coherence is lower even for time lags of

  17. Global Auroral Energy Deposition during Substorm Onset Compared with Local Time and Solar Wind IMF Conditions

    Science.gov (United States)

    Spann, J. F.; Brittnacher, M.; Fillingim, M. O.; Germany, G. A.; Parks, G. K.

    1998-01-01

    The global images made by the Ultraviolet Imager (UVI) aboard the IASTP/Polar Satellite are used to derive the global auroral energy deposited in the ionosphere resulting from electron precipitation. During a substorm onset, the energy deposited and its location in local time are compared to the solar wind IMF conditions. Previously, insitu measurements of low orbiting satellites have made precipitating particle measurements along the spacecraft track and global images of the auroral zone, without the ability to quantify energy parameters, have been available. However, usage of the high temporal, spatial, and spectral resolution of consecutive UVI images enables quantitative measurement of the energy deposited in the ionosphere not previously available on a global scale. Data over an extended period beginning in January 1997 will be presented.

  18. Mode-coupling and nonlinear Landau damping effects in auroral Farley-Buneman turbulence

    CERN Document Server

    Hamza, Abdelaziz M

    2015-01-01

    The fundamental problem of Farley-Buneman turbulence in the auroral $E$-region has been discussed and debated extensively in the past two decades. In the present paper we intend to clarify the different steps that the auroral $E$-region plasma has to undergo before reaching a steady state. The mode-coupling calculation, for Farley-Buneman turbulence, is developed in order to place it in perspective and to estimate its magnitude relative to the anomalous effects which arise through the nonlinear wave-particle interaction. This nonlinear effect, known as nonlinear ``Landau damping'' is due to the coupling of waves which produces other waves which in turn lose energy to the bulk of the particles by Landau damping. This leads to a decay of the wave energy and consequently a heating of the plasma. An equation governing the evolution of the field spectrum is derived and a physical interpration for each of its terms is provided.

  19. Auroral ion beams and ion acoustic wave generation by fan instability

    International Nuclear Information System (INIS)

    Satellite observations indicate that efficient energy transport among various plasma particles and between plasma waves and plasma particles is taking place in auroral ion beam regions. These observations show that two characteristic wave types are associated with the auroral ion beam regions: electrostatic hydrogen cyclotron waves with frequencies above hydrogen gyrofrequency, and low frequency waves with frequencies below hydrogen gyrofrequency. We speculate that the low frequency waves can be ion acoustic waves generated through the fan instability. The presence of a cold background ion component is necessary for the onset of this instability. A cold ion component has been directly observed and has been indirectly suggested from observations of solitary wave structures. The wave-particle interaction during the development of the fan instability results in an efficient ion beam heating in the direction perpendicular to the ambient magnetic field. The fan instability development and the ion beam heating is demonstrated in a numerical particle simulation. 23 refs, 16 figs

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

    International Nuclear Information System (INIS)

    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.

  1. Coordinated rocket and satellite measurements of an auroral event. II - The rocket observations and analysis

    Science.gov (United States)

    Sharp, W. E.; Rees, M. H.; Stewart, A. I.

    1979-01-01

    A rocket-borne payload launched into an aurora and a simultaneous overpass of the Atmosphere Explorer C satellite yielded measurements of auroral optical emission rates, thermal ion and electron densities, and low-energy electron fluxes. Model calculations of the thermospheric manifestation of the aurora were performed through use of rocket-determined auroral ionization rates and satellite-determined neutral gas densities. Measured oxygen densities provided a means of assessing the quenching rate of an excited state of N2. Energy transfer from this excited state appears to be the major source of 5577-A emission. Optical emission at 6300 A cannot be explained either by electron impact on atomic oxygen or by dissociative recombination of O2(+).

  2. Unusual rainbow and white rainbow: A new auroral candidate in oriental historical sources

    Science.gov (United States)

    Hayakawa, Hisashi; Isobe, Hiroaki; Davis Kawamura, Akito; Tamazawa, Harufumi; Miyahara, Hiroko; Kataoka, Ryuho

    2016-06-01

    Solar activity has been recorded as auroras or sunspots in various historical sources. These records are of great importance for investigating both long-term solar activities and extremely intense solar flares. According to previous studies, they were recorded as "vapor," "cloud," or "light," especially in oriental historical sources; however, this terminology has not been discussed adequately, and remains still quite vague. In this paper, we suggest the possibility of using "unusual rainbow" and "white rainbow" as candidates of historical auroras in oriental historical sources, and examine if this is probable. This discovery will help us to make more comprehensive historical auroral catalogues, and require us to add these terms to auroral candidates in oriental historical sources.

  3. "Unusual Rainbow and White Rainbow" A new auroral candidate in oriental historical sources

    CERN Document Server

    Hayakawa, Hisashi; Kawamura, Akito Davis; Tamazawa, Harufumi; Miyahara, Hiroko; Kataoka, Ryuho

    2016-01-01

    Solar activity has been recorded as auroras or sunspots in various historical sources. These records are of much importance for investigating both long-term solar activities and extremely intense solar flares. In previous studies, they were recorded as "vapor," "cloud," or "light," especially in oriental historical sources; however, the terminology was not discussed adequately and is still quite vague. In this paper, we suggest the possibility of "unusual rainbow" and "white rainbow" as candidates of historical auroras in oriental historical sources and examine if it is probable. This discovery will help us to make more comprehensive historical auroral catalogues and require us to add these terms to auroral candidates in oriental historical sources.

  4. Ion distribution effects of turbulence on a kinetic auroral arc model

    Science.gov (United States)

    Cornwall, J. M.; Chiu, Y. T.

    1982-03-01

    An inverted-V auroral arc structure plasma-kinetic model is extended to phenomenologically include the effects of electrostatic turbulence, with k-parallel/k-perpendicular being much less than unity. It is shown that, unless plasma sheet ions are very much more energetic than the electrons, anomalous resistivity is not a large contributor to parallel electrostatic potential drops, since the support of the observed potential drop requires a greater dissipation of energy than can be provided by the plasma sheet. Wave turbulence can, however, be present, with the ion cyclotron turbulence levels suggested by the ion resonance broadening saturation mechanism of Dum and Dupree (1970) being comparable to those observed on auroral field lines. The diffusion coefficient and net growth rate are much smaller than estimates based solely on local plasma properties.

  5. Cluster observations and theoretical identification of broadband waves in the auroral region

    Directory of Open Access Journals (Sweden)

    M. Backrud-Ivgren

    2005-12-01

    Full Text Available Broadband waves are common on auroral field lines. We use two different methods to study the polarization of the waves at 10 to 180 Hz observed by the Cluster spacecraft at altitudes of about 4 Earth radii in the nightside auroral region. Observations of electric and magnetic wave fields, together with electron and ion data, are used as input to the methods. We find that much of the wave emissions are consistent with linear waves in homogeneous plasma. Observed waves with a large electric field perpendicular to the geomagnetic field are more common (electrostatic ion cyclotron waves, while ion acoustic waves with a large parallel electric field appear in smaller regions without suprathermal (tens of eV plasma. The regions void of suprathermal plasma are interpreted as parallel potential drops of a few hundred volts.

  6. Investigation of Io's auroral hiss emissions due to its motion in Jupiter's magnetosphere

    Institute of Scientific and Technical Information of China (English)

    Mohsen H. Moghimi

    2012-01-01

    The left-hand side of the auroral hiss emission observed by Galileo has a frequency time profile shaped very similar to the funnel shape observed in the Earth's auroral region.This close similarity indicates that we can use the theory of whistlermode propagation near the resonance cone to locate the emission source.The general characteristics of the whistler mode are discussed.Then the position of the emission source is investigated using a geometrical method that takes into account the trajectory of Galileo.Initially a point source is assumed.Then the possibility of a sheet source aligned along the magnetic field lines which are tangent to the surface of Io is investigated.Both types of sources show that the whistler mode radiation originates very close to the surface of Io.

  7. 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.

  8. Aspect angle dependence of backscatter intensity of 1-m auroral plasma waves

    International Nuclear Information System (INIS)

    The backscatter intensities of primary and secondary 1-m unstable plasma waves in the auroral E region have been measured as a function of magnetic aspect angle (α) for electric field values between 25 and 30 mV/m. The variation of the absorption A, measured in decibels, is of the form A = -IaCo cos2 α/(1 + Co cos2 α). The best fits to the observed attenuation yield parameter values of (Ia, Co) = (49.6, 530) and (48.8, 900) for primary and secondary waves, respectively. The backscatter intensity from primary waves has the same aspect angle dependence as the mean Doppler velocity aspect angle-dependence observed in previous auroral radar data sets (Nielsen, 1986). The observations suggest that the radar backscatter cross section of the primary waves maximizes a few kilometers higher in altitude than that of the secondary waves

  9. Laboratory diagnosis on three cases of imported plasmodium ovale malaria infection%三例输入性卵形疟的实验室诊断

    Institute of Scientific and Technical Information of China (English)

    田斌; 段绩辉; 徐明忠; 张兵; 廖瑜; 申晓君; 文岚

    2014-01-01

    Objective To analyze 3 cases of imported malaria infection,in order to reduce the misdiagnosis and missed diagnosis of ovale malaria infection. Methods By morphological test,nested polymerase chain reaction (PCR) and sequence analysis were used to confirm the 3 cases of imported malaria infection.Results The morphological test results showed no plasmodium (laboratory initial inspection),plasmodium ovale mixed infection with plasmodium falciparum and plasmodium ovale.However,plasmodium ovale,plasmodium ovale mixed infection with plasmodium falciparum and plasmodium ovale mixed infection with plasmodium vivax were detected by nested PCR by follow.Conclusions The morphological technique training and the application of molecular biology techniques should be strengthen for imported plasmodium ovale malaria infection,and can reduce the misdiagnosis and missed diagnosis of imported plasmodium ovale malaria infection.%目的:分析3例输入性疟疾的实验室诊断,减少卵形疟的误诊与漏诊。方法采用形态学检查、巢氏聚合酶链反应(PCR)及序列分析等方法确诊3例输入性疟疾病例。结果3例患者形态学检查结果分别是未检出疟原虫(实验室初次检查)、检出卵形与恶性疟原虫和检出卵形疟原虫;巢氏PCR检测结果依次是卵形疟原虫感染、卵形与恶性疟原虫混合感染和卵形与间日疟原虫混合感染。结论需加强疟疾消除地区疟原虫形态学检查技术的培训和推广。应用分子生物学检查技术可减少输入性卵形疟的误诊与漏诊。

  10. Dengue infection as a potential trigger of an imported Plasmodium ovale malaria relapse or a long incubation period in a non-endemic malaria region

    Directory of Open Access Journals (Sweden)

    Otília Lupi

    2016-03-01

    Conclusions: Concurrent infections of DENV and malaria have rarely been reported; the actual impact of these sequential or simultaneous infections remains unknown. Therefore, DF must be considered as a potential co-morbidity for malaria, because of its influence on fluid electrolyte management. The case presented showed consistent temporal, clinical, and laboratory evidence that the relapse or the long incubation period of P. ovale malaria may have been triggered by a recent DF episode. To the authors’ knowledge, this is the first report of DENV and P. ovale co-infection.

  11. Storm time dynamics of auroral electrojets: CHAMP observation and the Space Weather Modeling Framework comparison

    Directory of Open Access Journals (Sweden)

    H. Wang

    2008-03-01

    Full Text Available We investigate variations of the location and intensity of auroral currents during two magnetic storm periods based on magnetic field measurements from CHAMP separately for both hemispheres, as well as for the dayside and nightside. The corresponding auroral electrojet current densities are on average enhanced by about a factor of 7 compared to the quiet time current strengths. The nightside westward current densities are on average 1.8 (2.2 times larger than the dayside eastward current densities in the Northern (Southern Hemisphere. Both eastward and westward currents are present during the storm periods with the most intense electrojets appearing during the main phase of the storm, before the ring current maximizes in strength. The eastward and westward electrojet centers can expand to 55° MLat during intense storms, as is observed on 31 March 2001 with Dst=−387 nT. The equatorward shift of auroral currents on the dayside is closely controlled by the southward IMF, while the latitudinal variations on the nightside are better described by the variations of the Dst index. However, the equatorward and poleward motion of the nightside auroral currents occur earlier than the Dst variations. The Space Weather Modeling Framework (SWMF can capture the general dynamics of the storm time current variations. Both the model and the actual data show that the currents tend to saturate when the merging electric field is larger than 10 mV/m. However, the exact prediction of the temporal development of the currents is still not satisfactory.

  12. Fast Auroral Snapshot Mission Unique Electronics Complete Spacecraft Electronics Contained in a Single Enclosure

    OpenAIRE

    Dougherty, Lamar; Gruner, Timothy; Wilmot, Jonathan; Chiville, Michael

    1995-01-01

    The Fast Auroral Snapshot (FAST) Mission Unique Electronics (MUE), housed in a single container, controls all major spacecraft functions. The functions include, Command and Data Handling (C&DH), Attitude Control and Stabilization (ACS), battery charge control and power distribution which comprise the Power System Electronics (PSE), thermal sensing and control, pyrotechnic device firing, spacecraft health and safety functions, Instrument Data Processing Unit (IDPU) interface and Small Launch V...

  13. Cassini UVIS Saturn Auroral Images from the 2013 HST/Cassini Campaign

    OpenAIRE

    Pryor, Wayne; Jouchoux, Alain; Esposito, Larry; Crary, Franck; Radioti, Aikaterini; Grodent, Denis; Gustin, Jacques; Gérard, Jean-Claude; Kurth, William; Mitchell, Donald; Nichols, Jonathan; Badman, Sarah

    2013-01-01

    In 2013 coordinated observations of Saturn by the Cassini spacecraft and Hubble Space Telescope (HST) were obtained. During these observations the Cassini spacecraft provided a high-latitude view of Saturn's auroras. Intense auroras were observed by the Ultraviolet Imaging Spectrograph (UVIS) from close range (about 5 Saturn radii away). A 6-frame UVIS movie has been constructed from some of the observations from May 20- 21, 2013 showing the evolution of two bright auroral features. We report...

  14. Nonlinear wave structures in collisional plasma of auroral E-region ionosphere

    Directory of Open Access Journals (Sweden)

    A. V. Volosevich

    Full Text Available Studies of the auroral plasma with small-scale inhomogenieties producing the VHF-radar reflections (radar aurora when observed in conditions of the saturated Farley-Buneman instability within the auroral E region, show strong nonlinear interactions and density fluctuations of 5–15%. Such nonlinearity and high fluctation amplitudes are inconsistent with the limitations of the weak turbulence theory, and thus a theory for arbitrary amplitudes is needed. To this end, a nonlinear theory is described for electrostatic MHD moving plasma structures of arbitrary amplitude for conditions throughout the altitude range of the collisional auroral E region. The equations are derived, from electron and ion motion self-consistent with the electric field, for the general case of the one-dimensional problem. They take into account nonlinearity, electron and ion inertia, diffusion, deviation from quasi-neutrality, and dynamical ion viscosity. The importance of the ion viscosity for dispersion is stressed, while deviation from the quasi-neutrality can be important only at rather low plasma densities, not typical for the auroral E region. In a small amplitude limit these equations have classical nonlinear solutions of the type of "electrostatic shock wave" or of knoidal waves. In a particular case these knoidal waves degrade to a dissipative soliton. A two-dimensional case of a quasi-neutral plasma is considered in the plane perpendicular to the magnetic field by way of the Poisson brackets, but neglecting the nonlinearity and ion inertia. It is shown that in these conditions an effective saturation can be achieved at the stationary turbulence level of order of 10%.

  15. Rocket observation of energetic electrons in the low-altitude auroral ionosphere during the DELTA campaign

    Science.gov (United States)

    Ogasawara, K.; Asamura, K.; Takashima, T.; Saito, Y.; Mukai, T.

    2006-09-01

    This paper reports on properties of energetic electrons observed by the Auroral Particle Detector (APD) on board the sounding rocket S-310-35, which was launched from And/0ya Rocket Range, Norway, at 0033:00 UT on 13 December 2004 during the DELTA campaign. The APD was designed to measure energy spectra of energetic electrons in the range of 3.5 to 65 keV every 10 ms using avalanche photodiodes. The measurement was done at altitudes of 90-140 km (apogee height of the rocket flight), which corresponded to the collisional interaction region of precipitating electrons with the atmospheric constituents. The overall profile of energetic electron precipitations was consistent with auroral images taken from the ground. The downward fluxes almost always exceeded those of upward electrons, and the ratio of downward to upward fluxes increased with energy and also with altitude. This is reasonably understood in terms of the effect of collisions between the energetic electrons and the atmospheric constituents. An interesting feature in energy spectra of precipitating electrons is the existence of non-thermal electrons at higher energies, regardless of inside or outside of auroral arcs. In order to predict the incident downward spectra at the top of the atmosphere, we have applied an analytic method of Luhmann (1976) to evaluate the collisional effect on the electron spectra. As a result, most of the observed energy spectra of precipitating electrons are well expressed by kappa distributions with the thermal energy of a few hundreds of eV and kappa of 5-8, while the spectrum inside a strong arc is better fitted by the sum of a Maxwellian distribution on the lower energy side and a power law at higher energies. To the authors' knowledge, this is the first direct and reliable measurement of energy spectra of electrons in the 10-keV energy range in the auroral ionosphere.

  16. Composite imaging of convective flows and auroral forms during a substorm cycle

    Science.gov (United States)

    Semeter, J. L.; Butler, T.; Zettergren, M. D.; Nicolls, M. J.; Heinselman, C. J.

    2009-12-01

    Measurements obtained with the electronically steerable Poker Flat Incoherent Scatter Radar (PFISR) and a collocated all-sky camera have been used to construct composite images of ionospheric convective flows and auroral forms associated with an isolated substorm on 26 March 2008. The radar was configured to cycle through a 5x5 grid of beam positions. A statistical inversion of line-of-sight velocities was used to construct images of the overlying flow field at 30-km spatial resolution and 1-min time resolution over a 100x100-km field. The flow fields were co-registered with all-sky images recorded at 20-s cadence. Analysis of the composite images has revealed several interesting contrasts between growth-, expansion-, and recover-phase morphology. These include, (1) anti-correlation between ion velocity (electric field) and luminosity (plasma density, hence, conductance) in space and time during growth- and expansion-phases; identical velocities inside and outside the aurora during recovery phase, (2) large tangential velocity directed along auroral boundaries during all phases (consistent with electric field directed into the aurora), irrespective of the orientation of the arc boundary, and (3) large relative drift (~2 km/s) between aurora forms and convective flows during the recovery phase; little or no proper motion during growth phase. The results are interpreted with respect to electrodynamic models of auroral M-I coupling. Composite image showing convective flows (arrows), ion temperature at 200 km (contours), and auroral forms at onset of a pseudo-breakup event.

  17. Thermospheric Control of the Auroral Source of O+Ions for the Magnetosphere

    OpenAIRE

    Lockwood, Mike

    1984-01-01

    Linear theory, model ion-density profiles and MSIS neutral thermospheric predictions are used to investigate the stability of the auroral, topside ionosphere to oxygen cyclotron waves: variations of the critical height, above which the plasma is unstable, with field-aligned current, thermal ion density and exospheric temperature are considered. In addition, probabilities are assessed that interactions with neutral atomic gases prevent O+ ions from escaping into the magnetosphere after they ha...

  18. 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

  19. Towards a synthesis of substorm electrodynamics: HF radar and auroral observations

    Science.gov (United States)

    Grocott, A.; Lester, M.; Parkinson, M. L.; Yeoman, T. K.; Dyson, P. L.; Devlin, J. C.; Frey, H. U.

    2006-12-01

    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 way which has

  20. Inhomogeneous transverse electric fields and wave generation in the auroral region : a statistical study

    OpenAIRE

    Hamrin, Maria; ANDRE, M; Ganguli, G; Gavrishchaka, VV; Koepke, ME; Zintl, MW; Ivchenko, N.; Karlsson, T.; Clemmons, JH

    2001-01-01

    We use data from the Freja satellite to investigate the importance of localized transverse DC electric fields for the generation of broadband waves responsible for ion heating in the auroral region. Theoretical models indicate that shear in the plasma Row perpendicular to the geomagnetic field can generate waves in a broad range around the ion gyrofrequency for parallel currents significantly below the threshold of the current-driven electrostatic ion cyclotron instability. We compare in situ...

  1. Anomalous width variation of rarefactive ion acoustic solitary waves in the context of auroral plasmas

    Directory of Open Access Journals (Sweden)

    S. S. Ghosh

    2004-01-01

    Full Text Available The presence of dynamic, large amplitude solitary waves in the auroral regions of space is well known. Since their velocities are of the order of the ion acoustic speed, they may well be considered as being generated from the nonlinear evolution of ion acoustic waves. However, they do not show the expected width-amplitude correlation for K-dV solitons. Recent POLAR observations have actually revealed that the low altitude rarefactive ion acoustic solitary waves are associated with an increase in the width with increasing amplitude. This indicates that a weakly nonlinear theory is not appropriate to describe the solitary structures in the auroral regions. In the present work, a fully nonlinear analysis based on Sagdeev pseudopotential technique has been adopted for both parallel and oblique propagation of rarefactive solitary waves in a two electron temperature multi-ion plasma. The large amplitude solutions have consistently shown an increase in the width with increasing amplitude. The width-amplitude variation profile of obliquely propagating rarefactive solitary waves in a magnetized plasma have been compared with the recent POLAR observations. The width-amplitude variation pattern is found to fit well with the analytical results. It indicates that a fully nonlinear theory of ion acoustic solitary waves may well explain the observed anomalous width variations of large amplitude structures in the auroral region.

  2. Study of AKR hollow pattern characteristics at sub-auroral regions

    Science.gov (United States)

    Boudjada, Mohammed Y.; Sawas, Sami; Galopeau, Patrick; Berthelier, Jean-Jacques; Schwingenschuh, Konrad

    2014-05-01

    The Earth's auroral kilometric radiation (AKR) is expected to exhibit a hollow pattern similar to that reported for the comparable emissions from Jupiter (e.g. Jovian decametric emissions - DAM). The hollow pattern is a hollow cone beam with apex at the point of AKR emission, axis tangent to the magnetic field direction, and an opening angle of the order of 80°. The properties of the hollow cone can be derived from the so-called dynamic spectrum which displays the radiation versus the observation time and the frequency. We analyze the auroral kilometric radiation recorded by the electric field experiment (ICE) onboard DEMETER micro-satellite. The dynamic spectra lead us to study the occurrence of the AKR recorded in the sub-auroral regions when the micro-satellite was at altitudes of about 700 km. We address in this contribution issues concerning the characteristics (occurrence, latitude and longitude) of the AKR hollow beam and their relations to the seasonal and solar activity variations.

  3. Boundary layer plasmas as a source for high-latitude, early afternoon, auroral arcs

    International Nuclear Information System (INIS)

    Simultaneous measurements of hot boundary layer plasma from PROGNOZ-7 and particle precipitation from the TIROS/NOAA satellite in nearly magnetically conjugate regions have been used to study the dynamo process responsible for the formation of high latitude, early afternoon, auroral arcs. Characteristic for the PROGNOZ-7 observations in the dayside boundary layer at high latitudes is the frequent occurrence of regions with injected magnetosheath plasma embedded in a 'halo' of antisunward flowing magnetosphere plasma. The injected magnetosheath plasma have several features which indicate that it also acts as a local source of EMF in the boundary layer. The process resembles that of a local MHD dynamo driven by the excess drift velocity of the injected magnetosheath plasma relative to the background magnetospheric plasma. The dynamo region is capable of driving fielc-aligned currents that couple to the ionosphere, where the upward current is associated with the high latitude auroral arcs. We demonstrate that the large-scale morphology as well as the detailed data intercomparison between PROGNOZ-7 and TIROS-N both agree well with a local injection of magnetosheath plasma into the dayside boundary layer as the main dynamo process powering the high-latitude, early afternoon auroral arcs. (Author)

  4. Statistics of 1-m wavelength plasma irregularities and convection in the auroral E region

    International Nuclear Information System (INIS)

    Data from the Sweden and Britain Radar Auroral Experiment have been utilized in a statistical study of auroral backscatter due to 1-m-scale plasma irregularities and of plasma convection in the auroral E layer. An examination of approximately 15,000 hours of backscatter amplitude data indicates that (1) the strongest backscatter is invariably associated with the main electrojets, between 1300-1900 UT and 2300-0300 UT, (2) only weak backscatter occurs in the vicinity of the convection reversals, particularly in the morning sector, and (3) the backscatter intensity can exhibit an aspect angle attenuation of between 0 and 10 dB/deg depending on the absolute intensity measured. Average convection patterns obtained from approximately 1400 hours of two-station measurements reveal a well-defined two-cell structure for all magnetic conditions. As magnetic activity increases the Harang discontinuity moves toward earlier local times, the flow speed increases and the morning convection cell expands relative to the evening cell. 32 references

  5. An empirical determination of the production efficiency for auroral 6300 AA emmission by energetic electrons

    International Nuclear Information System (INIS)

    Auroral data from the Soft Particle Spectrometer and the Red Line Photometer on the ISIS-2 spacecraft have been selected to form an electron energy flux and optical auroral emission data base. The energy fluxes are stored as integrated fluxes over four energy bands, and the corresponding stored optical emission rates are corrected for airglow and for albedo. Because of the variety of electron energy spectra represented in the data base it was possible to perform a regression analysis that yielded the production efficiency for the production of emission for each of the four bands. While the results of this analysis are interesting to compare with theoretical predictions of 6300 AA excitation processes, these statistical results are not as precise as the comparisons of individual experiments where all parameters, such as the atmospheric composition and temperature profiles are measured. The significance of this approach is that it permits a multiparameter description of an electron energy spectrum, and its relationship to a specific optical emission, by purely empirical means. This is particularly useful in the interpretation of ISIS-2 data from the instruments which provided the results, but should find further application in optical-particle auroral studies. (author)

  6. GREECE -- Ground-to-Rocket Electrodynamics-Electrons Correlative Experiment: High resolution rocket and ground-based investigations of small-scale auroral structure and dynamics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Methodology The methodology is based on making comparisons between downward electron flux, DC electric fields, electromagnetic waves, and auroral morphology. The...

  7. Longitudinal (UT effect in the onset of auroral disturbances over two solar cycles as deduced from the AE-index

    Directory of Open Access Journals (Sweden)

    L. A. Hajkowicz

    Full Text Available Statistical study on the universal time variations in the mean hourly auroral electrojet index (AE-index has been undertaken for a 21 y period over two solar cycles (1957–1968 and 1978–1986. The analysis, applied to isolated auroral substorm onsets (inferred from rapid variations in the AE-index and to the bulk of the AE data, indicates that the maximum in auroral activity is largely confined to 09–18 UT, with a distinct minimum at 03–06 UT. The diurnal effect was clearly present throughout all seasons in the first cycle but was mainly limited to northern winter in the second cycle. Severe storms (AE > 1000 nT tended to occur between 9–18 UT irrespective of the seasons whereas all larger magnetic disturbances (AE > 500 nT tended to occur in this time interval mostly in winter. On the whole the diurnal trend was strong in winter, intermediate at equinox and weak in summer. The implication of this study is that Eastern Siberia, Japan and Australia are mostly at night, during the period of maximum auroral activity whereas Europe and Eastern America are then mostly at daytime. The minimum of auroral activity coincides with near-midnight conditions in Eastern America. It appears that the diurnal UT distribution in the AE-index reflects a diurnal change between interplanetary magnetic field orientation and the Earth's magnetic dipole inclination.

    Key words. Ionosphere (auroral ionosphere · Magnetospheric physics (auroral phenomena; storms and substorms.

  8. DEMETER observations of bursty MF emissions and their relation to ground-level auroral MF burst

    Science.gov (United States)

    Broughton, M. C.; LaBelle, J.; Parrot, M.

    2014-12-01

    A survey of medium frequency (MF) electric field data from selected orbits of the Detection of Electro-Magnetic Emissions Transmitted from Earthquakes (DEMETER) spacecraft reveals 68 examples of a new type of bursty MF emissions occurring at high latitudes associated with auroral phenomena. These resemble auroral MF burst, a natural radio emission observed at ground level near local substorm onsets. Similar to MF burst, the bursty MF waves observed by DEMETER have broadband, impulsive frequency structure covering 1.5-3.0 MHz, amplitudes of 50-100 μV/m, an overall occurrence rate of ˜0.76% with higher occurrence during active times, and strong correlation with auroral hiss. The magnetic local time distribution of the MF waves observed by DEMETER shows peak occurrence rate near 18 MLT, somewhat earlier than the equivalent peak in the occurrence rate of ground level MF burst, though propagation effects and differences in the latitudes sampled by the two techniques may explain this discrepancy. Analysis of solar wind and SuperMAG data suggests that while the bursty MF waves observed by DEMETER are associated with enhanced auroral activity, their coincidence with substorm onset may not be as exact as that of ground level MF burst. One conjunction occurs in which MF burst is observed at Churchill, Manitoba, within 8 min of MF emissions detected by DEMETER on field lines approximately 1000 km southeast of Churchill. These observations may plausibly be associated with the same auroral event detected by ground level magnetometers at several Canadian observatories. Although it is uncertain, the balance of the evidence suggests that the bursty MF waves observed with DEMETER are the same phenomenon as the ground level MF burst. Hence, theories of MF burst generation in the ionosphere, such as beam-generated Langmuir waves excited over a range of altitudes or strong Langmuir turbulence generating a range of frequencies within a narrow altitude range, need to be revisited to

  9. Measurements of auroral particles by means of sounding rockets of mother-daughter type

    International Nuclear Information System (INIS)

    The scientific objective of the S17 payloads was to study the ionosphere during auroral situations and especially with regards to the local fine structure and a possible separation of spatial and temporal variations of auroral phenomena. The intensities of 8 keV and 2 keV electrons have been measured from one sounding rocket launched into a breakup aurora of moderate activity and from another rocket launched into a very active substorm situation. Both the rockets were of mother-daughter type i.e. had two separated payloads. The general features in the data of different particle energies were very similar over the whole flight time of the rockets. Special events and gradients and well identifiable shapes in the particle intensities were studied to see if the intensity fluctuations obtained from two detectors in one payload or from detectors into separate payloads were time delayed. Such time delays in the particle flux intensities were obvious in both of the rocket measurements and most of these time shifts could be understood as caused by spatial variations in the particle precipitation. In parts of the rocket flights the particle intensity variations were true temporal changes. The time lags between 8 keV and 2 keV electron intensities detected in the same payload, which could be observed and were obtained by crosscorrelation analyses, were in the range less than 0.3 s and most of them less than 0.1 s. If the time differences are assumed to be caused by the velocity dispersion of the particles, the particle data reported here placed the modulation source at a distance of less than 10 000 km from the rocket position. Measurements at the S17-1 mother payload of the electric field have been compared with data of precipitating electrons and low-light-level-TV-recording of the auroral situation. An inverted-V precipitation event was observed and was associated with auroral arcs and with reversals of the measured electric field components implicating the possibility of

  10. Predictive ability of four auroral precipitation models as evaluated using Polar UVI global images

    Science.gov (United States)

    Newell, P. T.; Sotirelis, T.; Liou, K.; Lee, A. R.; Wing, S.; Green, J.; Redmon, R.

    2010-12-01

    Auroral precipitation models have been valuable tools for several decades, but it has been difficult to estimate their objective accuracy. The use of global UV imagers, which make relatively instantaneous estimates of hemispheric auroral power, provides one approach forward. We present the first such validation and quantitative comparison of auroral precipitation models. Specifically, we correlated Polar UVI images with the predictions of four precipitation models. These are the Hardy Kp model, the Brautigam IMF-based model, the Evans nowcast model currently used at NOAA, and OVATION Prime, recently introduced by Newell and colleagues. Because calibration uncertainties exist for all particle detectors, and for imagers as well, we focus on correlation coefficients rather than the absolute magnitudes. To minimize dayglow, the nightside precipitating power (1800-0600 MLT) is considered and only for cases where that entire region is within the Polar UVI field of view. Also, only instances where each model has a prediction are considered (i.e., there must be IMF data, and there must be a NOAA satellite pass within the last 1 h). Altogether, 27,613 1 min ("instantaneous") images satisfied these criteria from 1996 to 1997. The four models investigated predict roughly half the variance in auroral power. From least to best at predicting instantaneous auroral power, the results are Brautigam IMF model (r = 0.68, r2 = 46%); Evans nowcast model (r = 0.70, r2 = 49%); Hardy Kp model (r = 0.72, r2 = 52%); and OVATION Prime IMF (r = 0.75, r2 = 56%). We also considered 1 h averages of UVI images. All four models improved, but the nowcast jumped from third to first: Brautigam IMF (r = 0.69, r2 = 48%); Hardy Kp (r = 0.74, r2 = 55%); OVATION Prime IMF (r = 0.76, r2 = 58%); Evans nowcast (r = 0.77, r2 = 59%). The nowcast approach benefits most from hourly averaging because at times more than one satellite pass is available. In principle, with enough satellites, the nowcast approach

  11. Auroral signatures of Bursty Bulk Flows from magnetosphere-ionosphere coupling models

    Science.gov (United States)

    Echim, M.; de Keyser, J. M.; Roth, M. A.

    2010-12-01

    The relationship between bursty bulk flows (BBFs) in the magnetospheric tail and the activation of auroral forms is well established from satellite and ground-based observations. Starting from a self-consistent description of BBFs based on a Vlasov equilibrium we provide a quantitative evaluation of the associated auroral effects by using a quasi-stationary magnetosphere-ionosphere (MI) coupling model. The self-consistent BBF model is based on a kinetic description of a 1-D plasma slab moving in background plasma and electromagnetic field. The model considers two exact constants of motion and one adiabatic invariant (the magnetic moment). It solves the coupled Vlasov-Maxwell system of equations in one spatial dimension (perpendicular to the BBFs plasma bulk velocity and the main magnetic field) assuming the BBF is a 1D structure elongated in the direction of the background magnetic field. The BBF model provides the self-consistent profile of Φm, the electric potential, showing the formation of convergent electric fields at the dawnward flank of the Earth-ward oriented BBFs. It has been shown that magnetospheric convergent electric fields drive field-aligned (FA) potential drops, FA currents and electron precipitation and acceleration. A stationary MI coupling model developed for discontinuity-like magnetospheric generators with convergent electric fields developed earlier is adapted to describe the coupling between the BBFs and the auroral ionosphere. The kernel of the MI coupling model is the condition of current continuity at the topside ionosphere, from which we compute the electric potential in the ionosphere for a given Φm. The MI coupling model is based on a Knight-type current-voltage relationship and a height-integrated conductivity model that depends on the energy deposited in the ionosphere by precipitating electrons. We show that the convergent electric field formed at the flanks of the BBF drive a FA potential drop and downward electron acceleration

  12. Influence of geometry change on creep failure life of 90 deg. pressurised pipe bends with no initial ovality

    International Nuclear Information System (INIS)

    The influence of the geometry change during creep on the failure life of 90 deg. pipe bends, subjected to internal pressure, was investigated using finite element creep damage analyses. The bends were considered to be circular in shape with no initial ovality. The failure lives obtained using the material properties for a CrMoV pipe steel at 640 deg. C clearly show a significant life reduction when the geometry change is included. In the range of the pipe bend dimension ratios investigated, it was found that the failure lives could be reduced to between 65 and 78% of those obtained from constant geometry cases, indicating that the influence of geometry change may need to be appraised for detailed numerical analysis. The results were compared with those of the corresponding straight pipes and their relevance considered. It has been shown that under constant geometry conditions, the failure life for pipe bends is about 30% lower than that for the straight pipes

  13. Comparative anatomy of the cardiac foramen ovale in cats (Felidae), dogs (Canidae), bears (Ursidae) and hyaenas (Hyaenidae).

    Science.gov (United States)

    Macdonald, A A; Johnstone, M

    1995-04-01

    The structure of the foramen ovale from 16 species representing 4 carnivore families, the Felidae, Canidae, Ursidae and Hyaenidae, was studied using the scanning electron microscope. The Felidae were represented by 9 domestic cat fetuses (Felis catus), 2 snow leopard neonates (Uncia uncia), an ocelot neonate (Leopardus pardalis), 2 lion neonates (Panthera leo), a panther neonate (Panthera pardus) and 3 tigers (Neofelis tigris), comprising 2 fetuses and a neonate. The Canidae were represented by a golden jackal neonate (Canis aureus), a newborn wolf (Canis lupus), 8 domestic dog fetuses (Canis familiaris), 3 red fox neonates (Vulpes vulpes) and a dhole neonate (Cuon alpinus). The Ursidae were represented by a brown bear neonate (Ursus arctos), a day-old grizzly bear cub (Ursus arctos horribilis), a polar bear neonate (Ursus maritimus), and 2 additional bear fetuses (species unknown). The Hyaenidae were represented by a striped hyaena neonate (Hyaena hyaena). In each species, the foramen ovale, when viewed from the terminal part of the caudal vena cava, had the appearance of a short tunnel. A thin fold of tissue, the developed remains of the embryonic septum primum, extended from the distal end of the caudal vena cava for a variable distance into the lumen of the left atrium and contributed towards the 'tunnel' appearance in all specimens. It constituted a large proportion of the tube, and its distal end was straight-edged. There was fibrous material underlying the endothelium of the flap, the apparent morphology of which suggested that it comprised cardiac muscle.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7649822

  14. First Record of Amblyomma ovale (Koch, 1844 (Acari: Ixodidae parasitizing Lontra longicaudis (Olfers, 1818 (Carnivora: Mustelidae in Santa Catarina Island, Florianópolis, Sc, Brazil

    Directory of Open Access Journals (Sweden)

    Bibiana Verdin De Andrade

    2015-04-01

    Full Text Available Three female and one male Amblyomma ovale (Acari: Ixodidae were found parasitizing a neotropical otter (Lontra longicaudis (Carnivora: Mustelidae in Florianópolis, SC, Brazil. This is the first record of the occurrence of A. ovale in Santa Catarina Island and the second report of this ectoparasite in a mustelid species in Brazil. A. ovale has been reported in wild carnivores in several Brazilian states and is considered one of the main predominant species of the Atlantic rainforest. The Amblyomma ticks are primarily responsible for the spread of BSF in humans. Among the species of Amblyomma infesting dogs is the A. ovale and the proximity between man and the dog favors the parasite sharing. Santa Catarina Island has many rural and wild environments shared by domestic animals, especially dogs, such as the environment where the otter was found in this study. Proper determination of tick species and their distribution in different geographical regions is essential for the understanding of the epidemiology of Rickettsiosis.

  15. Magnetospheric Interaction of the Galilean Satellites with Jupiter: Auroral Emissions from the Satellites and their Magnetic Footprints

    Science.gov (United States)

    Clarke, J. T.

    2003-12-01

    Each of the Galilean satellites of Jupiter has an electrodynamic interaction with Jupiter's magnetic field, due to their motion with respect to the corotating field which sweeps past each satellite. With the exception of Callisto, these interactions can be observed via auroral emissions from the magnetic footprints of each satellite in Jupiter's atmosphere, and also via auroral emissions produced in the satellite's atmosphere. Remote sensing observations from the JIMO spacecraft could provide measurements of these auroral emissions with excellent spatial resolution and time coverage, strongly complementing in situ plasma and field measurements near each satellite. The measurement of the auroral emissions at both ends of the field lines threading each satellite would provide important constraints on the nature and strength of the interaction. Extended time series made possible by remote sensing would reveal the variations of these emissions with the location of each satellite in Jupiter's field and the corotating plasma. The time coverage would also provide a baseline for the interpretation of the in situ measurements, which measure one location at a time. The prospects for this remote sensing by JIMO will be explored based on information from the Hubble Space Telescope measurements of Jupiter's auroral emissions.

  16. Comparative evaluation of Amblyomma ovale ticks infected and noninfected by Rickettsia sp. strain Atlantic rainforest, the agent of an emerging rickettsiosis in Brazil.

    Science.gov (United States)

    Krawczak, Felipe S; Agostinho, Washington C; Polo, Gina; Moraes-Filho, Jonas; Labruna, Marcelo B

    2016-04-01

    In 2010, a novel spotted fever group rickettsiosis was reported in the Atlantic rainforest coast of Brazil. The etiological agent was identified as Rickettsia sp. strain Atlantic rainforest, and the tick Amblyomma ovale was incriminated as the presumed vector. The present study evaluated under laboratory conditions four colonies of A. ovale: two started from engorged females that were naturally infected by Rickettsia sp. strain Atlantic rainforest (designated as infected groups); the two others started from noninfected females (designated as control groups). All colonies were reared in parallel from F0 engorged female to F2 unfed nymphs. Tick-naïve vesper mice (Calomys callosus) or domestic rabbits were used for feeding of each tick stage. Rickettsia sp. strain Atlantic rainforest was preserved by transstadial maintenance and transovarial transmission in A. ovale ticks for at least 2 generations (from F0 females to F2 nymphs), because nearly 100% of the tested larvae, nymphs, and adults from the infected groups were shown by PCR to contain rickettsial DNA. All vesper mice and rabbits infested by larvae and nymphs, and 50% of the rabbits infested by adults from the infected groups seroconverted, indicating that these tick stages were vector competent for Rickettsia sp. strain Atlantic rainforest. Expressive differences in mortality rates and reproductive performance were observed between engorged females from the infected and control groups, as indicated by 75.0% and 97.1% oviposition success, respectively, and significantly lower egg mass weight, conversion efficiency index, and percentage of egg hatching for the infected groups. Our results indicate that A. ovale can act as a natural reservoir for Rickettsia sp. strain Atlantic rainforest. However, due to deleterious effect caused by this rickettsial agent on engorged females, amplifier vertebrate hosts might be necessary for persistent perpetuation of Rickettsia sp. strain Atlantic rainforest in A. ovale under

  17. Coordinated use of ground-based auroral and high-precision LEO magnetic and electric field measurements to investigate auroral electrodynamics

    Science.gov (United States)

    Donovan, E.

    2008-12-01

    There are now dozens of sensitive All-Sky Imagers (ASIs) deployed in networks spanning latitudes from the subauroral zone into the polar cap and many hours of magnetic local time. These new networks are collecting data with unprecedented spatial coverage and temporal resolution and in numerous scientifically interesting wavelength ranges. As well, direct satellite overflights of ground-based images that were once rare occurrences are becoming increasingly commonplace. This talk will focus on the scientific opportunities afforded by the integrated use of ground-based auroral images and magnetic and electric field data from existing and planned LEO missions including CHAMP, Oersted, and Swarm. These opportunities include exploring the relationship between field-aligned current and Poynting flux and different types of aurora, as well as reducing spatio-temporal ambiguity in the in situ measurements.

  18. The Plausibility of the Stationary Inertial Alfven Wave in Explaining Important Morphological and Temporal Signatures of Auroral Arcs based on Laboratory Experiments and Auroral Observations

    Science.gov (United States)

    Nogami, S. H.; Koepke, M. E.; Gillies, D. M.; Knudsen, D. J.; Vincena, S. T.; Van Compernolle, B.; Donovan, E.

    2015-12-01

    The Stationary Inertial Alfven Wave (StIAW) [Knudsen J. Geophys. Res., 101, 10761 (1996)] is a non-fluctuating, non-travelling, spatially periodic pattern in electromagnetic field and fluid quantities that arises in the simultaneous presence of a magnetic-field-aligned current channel and cross-magnetic field plasma flow. Theory predicts [Finnegan et al., Nonlin. Proc. Geophys., 15, 957 (2008)] that the wave appears as an ion density perturbation that is static in the laboratory frame and that the wave electric field can accelerate electrons parallel to a background magnetic field. For experiments in the afterglow plasma in LAPD-U, results of which are reported on in this poster, the necessary conditions for the stationary wave are generated by a biased segmented electrode that creates a convective flow and a planar-mesh electrode that draws current parallel to the background magnetic field. An electrostatic probe and a retarding field energy analyzer measure fixed (in the laboratory frame) patterns in the ion density and electron energy. Spatial patterns of electron acceleration are reminiscent of the patterns present during the formation of discrete auroral arcs. Observation of long-lived discrete arcs indicates that some arcs require a generation mechanism that supports electron acceleration parallel to auroral field lines for tens of minutes. We present arc lifetime statistics to emphasize the paucity of physical models that explain these observations. *Support from NSF grant PHY-130-1896 and grants from the Canadian Space Agency is gratefully acknowledged. We also thank the THEMIS ASI Teams at U Calgary and UC Berkeley.

  19. Transcranial Doppler for patent foramen ovale screening: is there a good correlation with transesophageal echocardiography? Doppler transcraniano contrastado para triagem de forame oval patente: existe boa correlação com ecocardiograma transesofágico?

    Directory of Open Access Journals (Sweden)

    Marcos Christiano Lange

    2008-12-01

    Full Text Available Right-to-left shunt (RLS can be identified by contrast-enhanced transcranial Doppler (cTCD in patent foramen ovale (PFO patients. AIM: To evaluate cTCD for PFO screening comparing it to cTEE. METHOD: 45 previous cTCD performed for PFO diagnosis and correlated its findings with cTEE. Patients were submitted to a cTCD standardized technique and were divided in two groups according to RLS: Group 1, patients with a positive RLS and Group 2 when RLS was negative. RESULTS: 29 (65% patients were included in group 1 and 16 (35% in group 2. PFO confirmation by cTEE was performed in 28 (62% patients. cTCD had a 92.85% sensitivity, 82.35% specificity, 89.65% positive predictive value and 87.5% negative predictive value when compared to cTEE for PFO diagnosis. CONCLUSION: Standardized technique cTCD allows for RLS visualization in PFO patients with a good correlation with cTEE and can be used as a screening test before cTEE.A comunicação direita-esquerda (CDE pode ser identificada por Doppler transcraniano contrastado (DTCc em pacientes com forame oval patente (FOP. OBJETIVOS: Analisar o DTCc para triagem de FOP comparado a ecocardiografia transesofágica (ETEc. MÉTODO: Realizamos 45 exames de DTCc para diagnóstico de FOP e correlacionamos com os achados do ETEc. Os pacientes foram submetidos a técnica padronizada e divididos em dois grupos conforme a positividade do exame. RESULTADOS: 29 (65% pacientes foram incluídos no grupo 1 (CDE positiva e 16 (35% no grupo 2 (CDE negativa. A confirmação do FOP pelo ETEc ocorreu em 28 (62% pacientes. O DTCc apresentou sensibilidade de 92,85%, especificidade de 82,35%, valor preditivo positivo de 89,65% e valor preditivo negativo de 87,5% comparado ao ETEc para o diagnóstico de FOP. CONCLUSÃO: A técnica padronizada de DTCc possibilita a visualização de CDE em pacientes com FOP com boa correlação com o ETEc.

  20. Parallel electric field in the auroral ionosphere: excitation of acoustic waves by Alfvén waves

    Directory of Open Access Journals (Sweden)

    P. L. Israelevich

    2004-09-01

    Full Text Available We investigate a new mechanism for the formation of a parallel electric field observed in the auroral ionosphere. For this purpose, the excitation of acoustic waves by propagating Alfvén waves was studied numerically. We find that the magnetic pressure perturbation due to finite amplitude Alfvén waves causes the perturbation of the plasma pressure that propagates in the form of acoustic waves, and gives rise to a parallel electric field. This mechanism explains the observations of the strong parallel electric field in the small-scale electromagnetic perturbations of the auroral ionosphere. For the cases when the parallel electric current in the small-scale auroral perturbations is so strong that the velocity of current carriers exceeds the threshold of the ion sound instability, the excited ion acoustic waves may account for the parallel electric fields as strong as tens of mV/m.

  1. The dependence of modeled OI 1356 and N2 Lyman Birge Hopfield auroral emissions on the neutral atmosphere

    Science.gov (United States)

    Germany, G. A.; Torr, M. R.; Richards, P. G.; Torr, D. G.

    1990-01-01

    The sensitivity of selected auroral emissions to anticipated changes in the neutral atmosphere was investigated from the results of a series of sensitivity studies conducted using an auroral emission code developed by Richards and Torr (1990). In particular, the behavior of OI 1356 and two Lyman Birge Hopfield (LBH) bands and their ratios to each other with changing atmospheric composition was examined. It was found that, for anticipated average uncertainties in the neutral atmosphere (factor 2 at auroral altitudes), the resultant change in the modeled intensities is comparable to or less than the uncertainty in the neutral atmosphere. The variation in the I 1356/I 1838 ratio over the equivalent of a solar cycle is less than 50 percent, and the summer-to-winter changes are approximately a factor of 2.

  2. Observed relation between magnetic field aligned electric fields and downward electron energy fluxes in the vicinity of auroral forms

    International Nuclear Information System (INIS)

    Using electron observations in the vicinity of, and over, auroral forms obtained from three rocket flights, we have found that the net downward electron energy flux generally varied as V2, where V is the magnetic-field-aligned electric potential difference inferred from the peak in the observed energy spectra of precipitating electrons. We show that this relation implies that V is proportional to the net downward number flux of electrons from the magnetosphere to the auroral ionosphere and thus that increases in V and increases in the net downward number flux of electrons are equally responsible for the enhanced electron energy deposition responsible for auroral forms. This also indicates a direct physical connection may exist between V and the net downward electron number flux

  3. Some characteristics of the parallel electric field acceleration of electrons over discrete auroral arcs as observed from two rocket flights

    International Nuclear Information System (INIS)

    Measurements of energetic electrons from two rocket flights, both crossing discrete auroral arc structures, are examined with respect to low altitude parallel potential drops accelerating electrons of magnetospheric origin downward. In both flights the traversals of magnetic field lines connected to discrete auroral arc structures were associated with inverted V like electron spectral features with the highest peak energies closely related to the brightest auroral forms. The most equatorward inverted V structures, associated with the main arc, seems to mark a boundary south of which the magnetospheric electron population had a higher temperature than north of it. The magnitude and altitude of the potential drop can in principle be obtained by using a model for the acceleration applied to the observed energy and pitch angle distribution of the energetic electrons. A method to study the acceleration mechanism by means of some relations connected to integral flux measurements (eg energy flux and current density of energetic electrons) is suggested. (author)

  4. A Wide Field Auroral Imager (WFAI for low Earth orbit missions

    Directory of Open Access Journals (Sweden)

    N. P. Bannister

    2007-03-01

    Full Text Available A comprehensive understanding of the solar wind interaction with Earth's coupled magnetosphere-ionosphere system requires an ability to observe the charged particle environment and auroral activity from the same platform, generating particle and photon image data which are matched in time and location. While unambiguous identification of the particles giving rise to the aurora requires a Low Earth Orbit satellite, obtaining adequate spatial coverage of aurorae with the relatively limited field of view of current space bourne auroral imaging systems requires much higher orbits. A goal for future satellite missions, therefore, is the development of compact, wide field-of-view optics permitting high spatial and temporal resolution ultraviolet imaging of the aurora from small spacecraft in low polar orbit. Microchannel plate optics offer a method of achieving the required performance. We describe a new, compact instrument design which can observe a wide field-of-view with the required spatial resolution. We report the focusing of 121.6 nm radiation using a spherically-slumped, square-pore microchannel plate with a focal length of 32 mm and an F number of 0.7. Measurements are compared with detailed ray-trace simulations of imaging performance. The angular resolution is 2.7±0.2° for the prototype, corresponding to a footprint ~33 km in diameter for an aurora altitude of 110 km and a spacecraft altitude of 800 km. In preliminary analysis, a more recent optic has demonstrated a full width at half maximum of 5.0±0.3 arcminutes, corresponding to a footprint of ~1 km from the same spacecraft altitude. We further report the imaging properties of a convex microchannel plate detector with planar resistive anode readout; this detector, whose active surface has a radius of curvature of only 100 mm, is shown to meet the spatial resolution and sensitivity requirements of the new wide field auroral imager (WFAI.

  5. Large scale patterns of auroral ionospheric convection observed with the Chatanika radar

    International Nuclear Information System (INIS)

    Ionospheric convection at auroral latitudes has been examined during a series of long duration experiments with the Chatanika, Alaska, incoherent scatter radar. These experiments have been carefully designed to obtain maximum latitudinal coverage (56 0Λ to 75 0Λ) while maintaining a temporal resolution of 30 min in order to resolve the effects of individual substorms on the convection pattern. Design criteria for the experiments are described together with presentation of observational data acquired during 400 hr of radar operations during various levels of geophysical disturbance. The data accentuate the repeatability of the gross features of the auroral convection and its basic conformity to the two0cell pattern predicted from the large-scale magnetospheric circulation. For moderate to active geomagnetic conditions uniform sunward convection with velocities of 800 to 1200 m/s spans the 62 0Λ to 72 0Λ latitude band at both dawn and dusk. In quieter circumstances the sunward convection continues in this region, but has smaller speeds and is centered at higher latitudes. Little evidence of a throat in the dayside convection pattern is seen at latitudes below 75 0Λ except in very disturbed circumstances. During several experiments coordinated operation of the Chatanika and Millstone Hill, Massachusetts, radars permitted the simultaneous observation of the auroral convection pattern at two different local times. substorms affect the convection at all local times and appears to generally enhance the rate of convection without seriously changing its direction. Near midnight, latitudinal displacements and expansions of the convection pattern during substorms may result in a local rotation or reversal of the direction of convection, while near dawn and dusk, convection velocities are enhanced and the region of sunward flow expands to lower latitudes

  6. Jupiter Thermospheric General Circulation Model (JTGCM): Global Structure and Dynamics Driven by Auroral and Joule Heating

    Science.gov (United States)

    Bougher, S. W.; J. Il. Waite, Jr.; Majeed, T.

    2005-01-01

    A growing multispectral database plus recent Galileo descent measurements are being used to construct a self-consistent picture of the Jupiter thermosphere/ionosphere system. The proper characterization of Jupiter s upper atmosphere, embedded ionosphere, and auroral features requires the examination of underlying processes, including the feedbacks of energetics, neutral-ion dynamics, composition, and magnetospheric coupling. A fully 3-D Jupiter Thermospheric General Circulation Model (JTGCM) has been developed and exercised to address global temperatures, three-component neutral winds, and neutral-ion species distributions. The domain of this JTGCM extends from 20-microbar (capturing hydrocarbon cooling) to 1.0 x 10(exp -4) nbar (including aurora/Joule heating processes). The resulting JTGCM has been fully spun-up and integrated for greater than or equal to40 Jupiter rotations. Results from three JTGCM cases incorporating moderate auroral heating, ion drag, and moderate to strong Joule heating processes are presented. The neutral horizontal winds at ionospheric heights vary from 0.5 km/s to 1.2 km/s, atomic hydrogen is transported equatorward, and auroral exospheric temperatures range from approx.1200-1300 K to above 3000 K, depending on the magnitude of Joule heating. The equatorial temperature profiles from the JTGCM are compared with the measured temperature structure from the Galileo AS1 data set. The best fit to the Galileo data implies that the major energy source for maintaining the equatorial temperatures is due to dynamical heating induced by the low-latitude convergence of the high-latitude-driven thermospheric circulation. Overall, the Jupiter thermosphere/ionosphere system is highly variable and is shown to be strongly dependent on magnetospheric coupling which regulates Joule heating.

  7. A Rocket-Base Study of Auroral Electrodynamics Within the Current Closure Ionosphere

    Science.gov (United States)

    Kaeppler, Stephen R.; Kletzing, Craig; Bounds, Scott R.; Sigsbee, Kristine M.; Gjerloev, Jesper W.; Anderson, Brian Jay; Korth, Haje; Lessard, Marc; Labelle, James W.; Dombrowski, Micah P.; Pfaff, Robert F.; Rowland, Douglas E.; Jones, Sarah; Heinselman, Craig J.; DudokdeWit, Thierry

    2011-01-01

    The Auroral Current and Electrodynamics Structure (ACES) mission consisted of two sounding rockets launched nearly simultaneously from Poker Flat Research Range, AK on January 29, 2009 into a dynamic multiple-arc aurora. The ACES rocket mission, in conjunction with the PFISR Radar, was designed to observe the three-dimensional current system of a stable auroral arc system. ACES utilized two well instrumented payloads flown along very similar magnetic field footprints, at various altitudes with small temporal separation between both payloads. ACES High, the higher altitude payload (apogee 360 km), took in-situ measurements of the plasma parameters above the current closure region to provide the input signature into the lower ionosphere. ACES Low, the low-altitude payload (apogee 130 km), took similar observations within the current closure region, where cross-field currents can flow. We present results comparing observations of the electric fields, magnetic fields, electron flux, and the electron temperature at similar magnetic footpoints between both payloads. We further present data from all-sky imagers and PFISR detailing the evolution of the auroral event as the payloads traversed regions connected by similar magnetic footpoints. Current measurements derived from the magnetometers on both payloads are further compared. We examine data from both PFISR and observations on the high-altitude payload which we interpreted as a signature of electron acceleration by means of Alfv n waves. We further examine all measurements to understand ionospheric conductivity and how energy is being deposited into the ionosphere through Joule heating. Data from ACES is compared against models of Joule heating to make inferences regarding the effect of collisions at various altitudes.

  8. Upwelling to Outflowing Oxygen Ions at Auroral Latitudes during Quiet Times: Exploiting a New Satellite Database

    Science.gov (United States)

    Redmon, Robert J.

    The mechanisms by which thermal O+ escapes from the top of the ionosphere and into the magnetosphere are not fully understood even with 30 years of active research. This thesis introduces a new database, builds a simulation framework around a thermospheric model and exploits these tools to gain new insights into the study of O+ ion outflows. A dynamic auroral boundary identification system is developed using Defense Meteorological Satellite Program (DMSP) spacecraft observations at 850 km to build a database characterizing the oxygen source region. This database resolves the ambiguity of the expansion and contraction of the auroral zone. Mining this new dataset, new understanding is revealed. We describe the statistical trajectory of the cleft ion fountain return flows over the polar cap as a function of activity and the orientation of the interplanetary magnetic field y-component. A substantial peak in upward moving O+ in the morning hours is discovered. Using published high altitude data we demonstrate that between 850 and 6000 km altitude, O+ is energized predominantly through transverse heating; and acceleration in this altitude region is relatively more important in the cusp than at midnight. We compare data with a thermospheric model to study the effects of solar irradiance, electron precipitation and neutral wind on the distribution of upward O+ at auroral latitudes. EUV irradiance is shown to play a dominant role in establishing a dawn-focused source population of upwelling O+ that is responsible for a pre-noon feature in escaping O+ fluxes. This feature has been corroborated by observations on platforms including the Dynamics Explorer 1 (DE-1), Polar, and Fast Auroral Snapshot SnapshoT (FAST) spacecraft. During quiet times our analysis shows that the neutral wind is more important than electron precipitation in establishing the dayside O+ upwelling distribution. Electron precipitation is found to play a relatively modest role in controlling dayside, and a

  9. Resolving the temporal-spatial ambiguity with the Auroral Spatial Structures Probe

    Science.gov (United States)

    Farr, Daniel

    The Auroral Spatial Structures Probe (ASSP) is a National Aeronautics and Space Administration (NASA) sounding rocket mission to measure small scale temporal and spatial variations in the Earth's electric and magnetic fields during breakup aurora conditions. Multiple time-separated measurements of the same spatial location must be made in order to resolve the temporal-spatial ambiguity. ASSP achieves multipoint measurements by ejecting a constellation of six subpayloads from the main payload. This thesis develops a method for identifying the optimal ejection vector, propose an automated test plan for calibrating the seven payloads, and discuss several challenges relating to the interpretation of ASSP data.

  10. Wideband satellite phase coherent beacon observations at auroral and equatorial latitudes - A review

    International Nuclear Information System (INIS)

    This paper presents a brief review of some of the principal results from the first two years of operation of the Wideband satellite which transmits phase-coherent signals from S-band to VHF. The auroral zone data show narrow regions of enhanced scintillation well equatorward of the discrete aurora. Such enhancements can be explained as a purely geometrical effect if the irregularities within the major precipitation regions have a sheet-like structure. Evidence of a localized irregularity source at the poleward boundary of the plasma trough is also found. Model computations are discussed and applied to the interpretation of equatorial data

  11. Search for auroral belt E-parallel fields with high-velocity barium ion injections

    Science.gov (United States)

    Heppner, J. P.; Ledley, B. G.; Miller, M. L.; Marionni, P. A.; Pongratz, M. B.

    1989-01-01

    In April 1984, four high-velocity shaped-charge Ba(+) injections were conducted from two sounding rockets at 770-975 km over northern Alaska under conditions of active auroral and magnetic disturbance. Spatial ionization (brightness) profiles of high-velocity Ba(+) clouds from photometric scans following each release were found to be consistent with the 28-sec theoretical time constant for Ba photoionization determined by Carlsten (1975). These observations therefore revealed no evidence of anomalous fast ionization predicted by the Alfven critical velocity hypothesis.

  12. Observations of E region irregularities generated at auroral latitudes by a high-power radio wave

    Science.gov (United States)

    Djuth, F. T.; Jost, R. J.; Noble, S. T.; Gordon, W. E.; Stubbe, P.

    1985-01-01

    The initial results of a series of observations made with the high-power HF heating facility near Tromso, Norway are reported. During these experiments, attention was focused on the production of artificial geomagnetic field-aligned irregularities (AFAIs) in the auroral E region by HF waves. A mobile 46.9-MHz radar was used to diagnose the formation of AFAIs having spatial scales of 3.2 across geomagnetic field lines. The dynamic characteristics of the AFAIs are discussed within the context of current theoretical work dealing with the natural production of AFAIs in the ionosphere.

  13. Kilometric radio waves generated along auroral field lines observed by ground facilities - A theoretical model

    Science.gov (United States)

    Ziebell, L. F.; Wu, C. S.; Yoon, Peter H.

    1991-01-01

    A theory of generation of radio waves observed by ground-based facilities in the frequency range 150-700 kHz is discussed. This work is a continuation of an earlier discussion (Wu et al., 1989) in which it was proposed that the trapped electrons along the auroral field lines can lead to a cyclotron instability which amplifies the whistler waves observed at ground level. The objective of the present study is to investigate the propagation effect on the wave amplification and to examine whether the proposed mechanism is indeed viable.

  14. What high altitude observations tell us about the auroral acceleration: A Cluster/DMSP conjunction

    OpenAIRE

    A. Vaivads; ANDRE, M; S. Buchert; Eriksson, A.; Olsson, A; Wahlund, J. E.; Janhunen, P.; Marklund, G.; Kistler, L. M.; Mouikis, S.; Winningham, D.; Fazakerley, A.N.; Newell, P.

    2003-01-01

    Magnetic conjugate observations by Cluster and DMSP F14 satellites are used to study the field lines of auroral arc. Cluster is well above the acceleration region and observes upward keV ion beams and bipolar electric structures. The integrated potential at Cluster altitudes shows a dip that is consistent with the keV electron acceleration energy at low altitude. The earthward Poynting flux at Cluster altitudes is comparable to the electron energy flux at low altitudes. Thus, for this event t...

  15. Ring current and auroral electrojets in connection with interplanetary medium parameters during magnetic storm

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    Full Text Available The relationship between the auroral electrojet indices (AE and the ring current magnetic field (DR was investigated by observations obtained during the magnetic storm on 1-3 April 1973. During the storm main phase the DR development is accompanied by a shift of the auroral electrojets toward the equator. As a result, the standard AE indices calculated on the basis of data from auroral observatories was substantially lower than the real values (AE'. To determine AE' during the course of a storm main phase data from subauroral magnetic observatories should be used. It is shown that the intensity of the indices (AE' which take into account the shift of the electrojets is increased substantially relative to the standard indices during the storm main phase. AE' values are closely correlated with geoeffective solar wind parameters. A high correlation was obtained between AE' and the energy flux into the ring current during the storm main phase. Analysis of magnetic field variations during intervals with intense southward IMF components demonstrates a decrease of the saturation effect of auroral electrojet currents if subauroral stations magnetic field variations are taken into account. This applies both to case studies and statistical data. The dynamics of the electrojets in connection with the development of the ring current and of magnetospheric substorms can be described by the presence (absence of saturation for minimum (maximum AE index values during a 1-h interval. The ring current magnetic field asymmetry (ASY was calculated as the difference between the maximum and minimum field values along a parallel of latitude at low latitudes. The ASY value is closely correlated with geoeffective solar wind parameters and simultaneously is a more sensitive indicator of IMF Bz variations than the symmetric ring current.

  16. Resonant generation of ion waves on auroral field lines by positive slopes in ion velocity space

    International Nuclear Information System (INIS)

    Simultaneous observations of wave spectra and particle velocity distributions obtained by the S3-3 satellite on auroral field lines, are studied. Emissions below the lower hybrid frequency occur just below multiples of the proton gyrofrequency. At higher frequencies the observed spectra show peaks just above such multiples. The ion and electron distributions are modeled, and numerical methods are used ot calculated the corresponding spatial wave growth rates. This theoretically obtained growth agrees rather well with the observed emissions. The major source of free energy is a positive slope perpendicular to the ambient magnetic field in the ion velocity distribution. (author)

  17. Combining Information on Multiple Detection Techniques to Estimate the Effect of Patent Foramen Ovale on Susceptibility to Decompression Illness

    Science.gov (United States)

    Feiveson, Alan H.; Foster, Philip P.

    2001-01-01

    The assembly and the maintenance of the International Space Station is expected to require hundreds of extravehicular excursions (EVA's) in the next 10 years. During an EVA, in order to allow movement and bending of limbs, spacesuit pressures are reduced to about 4.3 psi. as compared with about 14.7 psi. for normal atmospheric pressure at sea level. However, the exposure of astronauts to reduced pressures in spacesuits, is conducive to fonnation and growth of gas bubbles within venous blood or tissues, which could cause decompression illness (DCI), a pathology best known to occur among deep-sea divers when they return to the surface. To reduce the risk of DCI, astronauts adjust to the reduced pressure in stages for a prolonged time known as a "pre-breathe" period prior to their extravehicular activity. Despite the use of pre-breathe protocols, an increased risk of DCI can arise for about 25% of humans who have a small hole, known as a patent foramen ovale (PFO), between two chambers of the heart. The atrial septum's fossa oval is, an embryological remnant of a flap between the septae primum and secundum allows fetal right atrial blood to pass into the left atrium, and usually closes after birth (Hagen, et al,. 1984). If fusion does not occur, a valve-like opening, the foramen ovale persists between the two atria. It has been suggested that astronauts with PFO's might be at greater risk of stroke or other serious neurological DCI because bubbles from a venous site may traverse a PFO, travel to the aorta and then enter the cerebral circulatory system causing a stroke (Figure 1). Astronauts are not now screened for PFO's, however consideration is being given to doing so. Here, we study three main methods abbreviated here as "ITE", "TCD" and "TEE", for detecting PFO's in living subjects. All involve the introduction of bubbles into a vein, immediately after which a sensory probe attempts to detect the bubbles in systemic circulation. Presence of the injected bubbles in

  18. Correlation between Patent Foramen Ovale, Cerebral "Lesions" and Neuropsychometric Testing in Experienced Sports Divers: Does Diving Damage the Brain?

    Science.gov (United States)

    Balestra, Costantino; Germonpré, Peter

    2016-01-01

    SCUBA diving exposes divers to decompression sickness (DCS). There has been considerable debate whether divers with a Patent Foramen Ovale of the heart have a higher risk of DCS because of the possible right-to-left shunt of venous decompression bubbles into the arterial circulation. Symptomatic neurological DCS has been shown to cause permanent damage to brain and spinal cord tissue; it has been suggested that divers with PFO may be at higher risk of developing subclinical brain lesions because of repeated asymptomatic embolization of decompression-induced nitrogen bubbles. These studies however suffer from several methodological flaws, including self-selection bias. We recruited 200 volunteer divers from a recreational diving population who had never suffered from DCS; we then randomly selected 50 of those for further investigation. The selected divers underwent brain Magnetic Resonance Imaging to detect asymptomatic brain lesions, contrast trans-oesophageal echocardiography for PFO, and extensive neuro-psychometric testing. Neuro-psychometry results were compared with a control group of normal subjects and a separate control group for subjects exposed to neurotoxic solvents. Forty two divers underwent all the tests and are included in this report. Grade 2 Patent Foramen Ovale was found in 16 (38%) of the divers; brain Unidentified Bright Objects (UBO's) were found in 5 (11.9%). There was no association between PFO and the presence of UBO's (P = 0.693) or their size (p = 0.5) in divers. Neuropsychometric testing in divers was significantly worse from controls in two tests, Digit Span Backwards (DSB; p Coordination (EYE) tests. There was no correlation between PFO, number of UBO's and any of the neuro-psychometric tests. We conclude that for uneventful recreational diving, PFO does not appear to influence the presence of UBO's. Diving by itself seems to cause some decrease of short-term memory and higher cognitive function, including visual-motor skills; this

  19. Interatrial shunt. Diagnosis of patent foramen ovale and atrial septal defect with 64-row coronary computed tomography angiography

    International Nuclear Information System (INIS)

    The aim of this study was to investigate the frequency with which interatrial shunts are found during routine coronary computed tomography (CT) angiography and to describe imaging characterizations of patent foramen ovale (PFO), atrial septal defect (ASD), and atrial septal aneurysm (ASA). A total of 1081 adult patients were evaluated retrospectively for interatrial shunting; 77 were excluded from the study. CT diagnosis of PFO was defined as (1) a channel-like appearance of the interatrial septum (IAS) and (2) a contrast agent jet flow from the left atrium (LA) to the right atrium (RA). ASD was defined as (1) the IAS resembling a membrane with a hole and (2) a contrast jet flow between the two atria. ASA was identified by detecting a minimum 10-mm protrusion of the LA beyond the IAS into the RA. Among 1004 patients, 86 patients (8.6%) were diagnosed to have PFO. Another 23 patients (2.3%) had a hole in the IAS and were diagnosed as having ASD: 21 with an ostium secundum-type ASD and 2 with the sinus venosus type. ASA accompanied ASD in three patients. Electrocardiography-gated CT using the saline-chaser contrast injection technique that is routinely used for coronary arterial imaging can be used to detect interatrial shunts. The technique can also serve as a method for differentiating PFO, ASD, and ASA. (author)

  20. Assessment of Hypercoagulation State in Patients with Embolic Cerebrovascular or Transient Ischemic Attack and Patent Foramen Ovale

    Directory of Open Access Journals (Sweden)

    D Nikfarjam

    2010-03-01

    Full Text Available Background: Patent foramen ovale (PFO causes a right-to-left shunt in about a quarter of normal population. Hypercoagulation may be a risk factor for embolic cerebrovascular accidents (CVA in these patients by paradoxical emboli. In this study, we checked hypercoagulation states in the embolic CVA patients with PFO. Methods: In a cross- sectional study, 40 patients with CVA or transient ischemic attack ( TIA and PFO participated in the study. Serum level of Homocystein, lupus anticoagulant screening test, Factor V leiden, Anti Cardiolipin Antibody (ACLA (IgG, IgM , Anti- thrombin III, protein C, protein S,Anti B2 glycoprotein1 and platelet count were checked in all patients. The data were analyzed using the statistical package for social science series (SPSS 15.0 and descriptive statistical method.Results: The mean age was 42.4± 12.1. Seventeen (42.5% patients were females. Twenty- two (55% cases were diagnosed as having CVA and the others as TIA. Three (7.5% of the patients were diabetic and 8 (20% had a history of different stages of hypertension. Hyperlipidemia was detected in 6 (15% patients and according to the laboratory data none had any signs of hypercoagulation.Conclusion: According to the present study, hypercoagulation as a cofactor in CVA patients with PFO did not seem to be a direct risk factor for embolic CVA at least any higher than for normal population.

  1. Parametric peak stress functions of 90o pipe bends with ovality under steady-state creep conditions

    International Nuclear Information System (INIS)

    Stress-based life prediction techniques are commonly used to estimate the failure life of pressurised pipe-related components, such as welds and bends, under creep conditions. Previous research has shown that reasonable life predictions can be obtained, based on the steady-state peak stresses, compared with the life predictions obtained from creep damage modelling. In this work, a series of parametric steady-state peak rupture stress functions of right-angled pipe bends with ovality are presented, which are based on the results obtained from finite element (FE) analyses, covering a number of material property and geometry parameters in practical ranges. Methods used to determine the stress functions are described. The FE analyses have been performed using axisymmetric models, subjected to internal pressure only, with a Norton creep law. Typical examples of parametric peak stress curve fitting are shown. In particular, the accuracy of the interpolation and extrapolation abilities of the stress functions is assessed. The results show that in most cases the interpolated and extrapolated peak stresses are accurate to within ±3% and ±5%, respectively.

  2. Interventional Closure of Patent Foramen Ovale (PFO with Amplatzer PFO Occluder in Patients with Paradoxical Cerebral Embolism

    Directory of Open Access Journals (Sweden)

    Ali Mohammad Haji Zeinali

    2006-08-01

    Full Text Available Background: Percutaneous transcatheter closure has been proposed as an alternative to surgical closure or long-term anticoagulation in patients with presumed paradoxical embolism and patent foramen ovale (PFO. Methods: There were two symptomatic patients (29 and 47 years old who underwent percutaneous transcatheter closure of PFO after at least two events of cerebral ischemia; one embolic event had occurred under anti-platelet therapy. For both patients, Amplatzer PFO occluder measuring 25 mm in diameter were used. In both cases, complete occlusion by color Doppler and transesophageal contrast echocardiography investigation was achieved after the procedure and lasted at least up to 3 months after implantation as determined by our follow up. Mean fluoroscopy time was 16.7 minutes. Results: Percutaneous transcatheter closure was technically successful in both patients (100%. No residual shunt was seen at the end of the procedure or in follow-ups. In-hospital follow-up was uneventful. At a mean follow-up of 3 months, no recurrent embolic neurological events were observed. Conclusion: Transcatheter closure of PFO with Amplatzer PFO occluder devices is a safe and effective therapy for patients with previous paradoxical embolism PFO. Percutaneous closure is associated with a high success rate, low incidence of hospital complications, and freedom of cerebral ischemic events.

  3. Prevalence of Patent Foramen Ovale De-tected by Transcranial Color Coded Duplex Sonography in Cryp-togenic Stroke Patients

    Directory of Open Access Journals (Sweden)

    K. Ghandehari

    2004-06-01

    Full Text Available Background/Objectives: Contrast transcranial doppler has been used for detection of right-to-left shunts, such as the patent foramen ovale (PFO. Materials and Methods: All consecutive patients with cryptogenic brain infarction admitted to the Walter Mackenzie Hospital, Canada, during 2003-2004, enrolled in a prospective study. Cryptogenic stroke was determined using a standard battery of diagnostic investigations. Transcranial color coded duplex sonography (TCCDS with saline contrast was performed with an HP Sono 5500, USA device and a 4MHz linear probe. The middle cerebral artery was insonated at a 50-55 mm depth through a transtemporal window. Microbubble signals were recorded during normal respiration and Valsalva maneuver. Results: 114 patients (70 females, 44 males with cryptogenic stroke had contrast TCCDS done. PFO was detected in 41 patients (30 females, 11 males; 35.9%. In the overall study group, females were more preponderant to have PFO, however the difference was not significant (P=0.053. The frequency of PFO was not significantly different between age groups =45 years (P = 0.96. Conclusion: PFO detected by TCCD is an age independent factor in cryptogenic stroke, and its detection is more feasible with Valsalva maneuver.

  4. Patent Foramen Ovale in Patients with Sickle Cell Disease and Stroke: Case Presentations and Review of the Literature

    Directory of Open Access Journals (Sweden)

    Sheila Razdan

    2013-01-01

    Full Text Available Although individuals with sickle cell disease (SCD are at increased risk for stroke, the underlying pathophysiology is incompletely understood. Intracardiac shunting via a patent foramen ovale (PFO is associated with cryptogenic stroke in individuals without SCD. Recent evidence suggests that PFOs are associated with stroke in children with SCD, although the role of PFOs in adults with stroke and SCD is unknown. Here, we report 2 young adults with SCD, stroke, and PFOs. The first patient had hemoglobin SC and presented with a transient ischemic attack and a subsequent ischemic stroke. There was no evidence of cerebral vascular disease on imaging studies and the PFO was closed. The second patient had hemoglobin SS and two acute ischemic strokes. She had cerebral vascular disease with moyamoya in addition to a peripheral deep venous thrombosis (DVT. Chronic transfusion therapy was recommended, and the DVT was managed with warfarin. The PFO was not closed, and the patients' neurologic symptoms were stabilized. We review the literature on PFOs and stroke in SCD. Our cases and the literature review illustrate the dire need for further research to evaluate PFO as a potential risk factor for stroke in adults with SCD.

  5. Identification of broad-band waves above the auroral acceleration region: Cluster observations

    Directory of Open Access Journals (Sweden)

    M. Backrud

    2004-12-01

    Full Text Available We investigate broad-band emissions at frequencies above the ion gyrofrequency on auroral field lines at geocentric distances of about 4.5 Earth radii. Observations by the Cluster satellites are used to study the wave characteristics and to determine the wave modes involved. All events include some bursts of broad-band emissions with a substantial component of the electric field parallel to the geomagnetic field. Studying the polarization of the emissions we find that linear waves in a homogeneous plasma can be used to theoretically describe the observations.

    The broad-band emissions include short bursts of ion acoustic waves, and longer periods of ion Bernstein and Electrostatic Ion Cyclotron (EIC waves. All waves occur during the same event within a few seconds, with EIC waves as the most common. Theoretically, there is no sharp limit between these wave modes and they can be described by the same dispersion surface. These emissions are closely associated with low-frequency Alfvén waves, indicating a possible generation mechanism.

    Key words. Magnetospheric physics (auroral phenomena; electric fields; plasma waves and instabilities

  6. Searching for Far-Ultraviolet Auroral/Dayglow Emission from HD209458b

    CERN Document Server

    France, Kevin; Yang, Hao; Linsky, Jeffrey L; Wolven, Brian C; Froning, Cynthia S; Green, James C; Osterman, Steven N

    2010-01-01

    We present recent observations from the HST-Cosmic Origins Spectrograph aimed at characterizing the auroral emission from the extrasolar planet HD209458b. We obtained medium-resolution (R~18-20,000) far-ultraviolet (1150-1700A) spectra at both the Phase 0.25 and Phase 0.75 quadrature positions as well as a stellar baseline measurement at secondary eclipse. This analysis includes a catalog of stellar emission lines and a star-subtracted spectrum of the planet. We present an emission model for planetary H2 emission, and compare this model to the planetary spectrum. No unambiguously identifiable atomic or molecular features are detected, and upper limits are presented for auroral/dayglow line strengths. An orbital velocity cross-correlation analysis finds a statistically significant (3.8 sigma) feature at +15 (+/- 20) km/s in the rest frame of the planet, at 1582 A. This feature is consistent with emission from H2 B-X (2-9) P(4) (lambda_{rest} = 1581.11 A), however the physical mechanism required to excite this ...

  7. Probing Io's putative global magma ocean through FUV auroral spot morphology

    Science.gov (United States)

    Roth, Lorenz

    2013-10-01

    Whether Io possesses a magma ocean or not is a central issue for understanding the most volcanically active body in our solar system and is a long standing question as well. Khurana et al., Science 2011, recently substantiated the existence of a highly conductive magma layer inside Io's interior based on Galileo magnetometer measurements and techniques similar to those used to probe the crusts of Europa, Ganymede, and Callisto for liquid water oceans. If a global magma ocean modifies Io's local magnetic field environment, it will also significantly alter the morphology of Io's UV aurora. The most prominent aurora features are two bright spots that rock around the equator roughly in correlation with the varying orientation of the tilted Jovian magnetic field. Magnetic induction in a magma ocean would strongly attenuate the rocking of these near-surface spots. Interestingly, in previous STIS FUV observations the measured spot locations disagree considerably from the locations theoretically predicted for the global magma ocean case, but are in reasonable agreement if there is no ocean. However, the temporal and orbital coverage of Io's rocking auroral spots for the STIS dataset is presently insufficient to conclusively exclude or further investigate the molten magma layer idea. We therefore propose two visits of five consecutive STIS orbits to trend the auroral spot feature locations over a full variation cycle of the Jovian magnetic field near western elongation. This investigation will decisively constrain the molten magma layer inside Io and tests the putative evidence for a global ocean by Khurana et al. {2011}.

  8. Magnetosphere-ionosphere coupling during periods of extended high auroral activity: a case study

    Directory of Open Access Journals (Sweden)

    S. Liléo

    2008-03-01

    Full Text Available Results are presented from a case study of a plasma boundary crossing by the Cluster spacecraft during an extended period of high auroral activity. The boundary between the magnetotail lobe region of the Southern Hemisphere and the plasma sheet boundary layer, was characterized by intense electric and magnetic field variations, structured upward accelerated ion beams, narrow-scale large field-aligned Poynting fluxes directed upward away from the ionosphere, and a relatively sharp plasma density gradient.

    The observations are shown to be consistent with the concept of a multi-layered boundary with temporal and/or spatial variations in the different layers. H+ and O+ ion beams are seen to be accelerated upwards both by means of a field-aligned electric field and by magnetic pumping caused by large-amplitude and low-frequency electric field fluctuations. The peak energy of the ion beams may here be used as a diagnostic tool for the temporal evolution of the spatial structures, since the temporal changes occur on a time-scale shorter than the times-of-flight of the detected ion species.

    The case study also shows the boundary region to be mainly characterized by a coupling of the detected potential structures to the low ionosphere during the extended period of high auroral activity, as indicated by the intense field-aligned Poynting fluxes directed upward away from the ionosphere.

  9. Dynamics of the auroral electrojets and their mapping to the magnetosphere

    International Nuclear Information System (INIS)

    Data of the EISCAT and IMAGE magnetic observatories chains in combination with data of three Russian observatories (St. Petersburg, Borok and Moscow) were used to determine the eastward and westward electrojet dynamics in the course of magnetic storms. During the storm main phase and maximum substorm intensity the eastward electrojet is located at latitudes lower than usual. During intervals between substorms the westward electrojet centre shifts equatorwards as Dst increases. At a substorm maximum the westward electrojet widens polewards. The spectrograms of precipitating electrons and ions of auroral energies obtained onboard the DMSP F8, F10 and F11 satellites allow to connect the regions of the electrojet location with characteristic plasma structures at ionospheric altitudes. The eastward electrojet in the evening sector is located in the region of diffuse electron precipitations. The electrojet centre coincides with the latitude of an energy flux maximum of auroral protons. In the course of substorms the westward electrojet at the nightside is located at latitudes of both diffuse and discrete electron precipitations. The electrojets and plasma region boundaries are mapped to the magnetosphere. The paraboloid model of the magnetosphere is used here. The influence of paraboloid model input parameters on the dayside cusp latitude, on the ionospheric boundaries between open and closed as well as dipole-like and tail-like field lines is considered. It is shown that tail currents influence magnetic field line configuration in the nightside magnetosphere stronger than the ring current

  10. In-situ observation of electron kappa distributions associated with discrete auroral arcs

    Science.gov (United States)

    Ogasawara, Keiichi; Livadiotis, George; Samara, Marilia; Michell, Robert; Grubbs, Guy

    2016-04-01

    The Medium-energy Electron SPectrometer (MESP) sensor aboard a NASA sounding rocket was launched from Poker Flat Research Range on 3 March 2014 as a part of Ground-to-Rocket Electrodynamics-Electrons Correlative Experiment (GREECE) mission. GREECE targeted to discover convergent E-field structures at low altitude ionosphere to find their contribution to the rapid fluid-like structures of aurora, and MESP successfully measured the precipitating electrons from 2 to 200 keV within multiple discrete auroral arcs with the apogee of 350 km. MESP's unprecedented electron energy acceptance and high geometric factor made it possible to investigate precise populations of the suprathermal components measured in the inverted-V type electron energy distributions. The feature of these suprathermal electrons are explained by the kappa distribution functions with the parameters (densty, temperature, and kappa) consistent with the near-Earth tail plasma sheet, suggesting the source population of the auroral electrons. The kappa-values are different between each arc observed as a function of latitude, but are almost stable within one discrete arc. We suggest that this transition of kappa reflects the probagation history of source electrons through the plasma sheet by changing its state from non-equilibrium electron distributions to thermal ones.

  11. Development and performance of a suprathermal electron spectrometer to study auroral precipitations

    Science.gov (United States)

    Ogasawara, Keiichi; Grubbs, Guy; Michell, Robert G.; Samara, Marilia; Stange, Jason L.; Trevino, John A.; Webster, James; Jahn, Jörg-Micha

    2016-05-01

    The design, development, and performance of Medium-energy Electron SPectrometer (MESP), dedicated to the in situ observation of suprathermal electrons in the auroral ionosphere, are summarized in this paper. MESP employs a permanent magnet filter with a light tight structure to select electrons with proper energies guided to the detectors. A combination of two avalanche photodiodes and a large area solid-state detector (SSD) provided 46 total energy bins (1 keV resolution for 3-20 keV range for APDs, and 7 keV resolution for >20 keV range for SSDs). Multi-channel ultra-low power application-specific integrated circuits are also verified for the flight operation to read-out and analyze the detector signals. MESP was launched from Poker Flat Research Range on 3 March 2014 as a part of ground-to-rocket electrodynamics-electrons correlative experiment (GREECE) mission. MESP successfully measured the precipitating electrons from 3 to 120 keV in 120-ms time resolution and characterized the features of suprathermal distributions associated with auroral arcs throughout the flight. The measured electrons were showing the inverted-V type spectra, consistent with the past measurements. In addition, investigations of the suprathermal electron population indicated the existence of the energetic non-thermal distribution corresponding to the brightest aurora.

  12. Coordinated data on auroral electrodynamics from ground based radar diagnostics and Aureol-3 satellite

    International Nuclear Information System (INIS)

    Coordinated ground-satellite measurements of VHF radar arcs, magnetic variations and all-sky auroral imagery were performed from Kola-peninsula and from Finland together with direct particle and field measurements from AUREOL-3 satellite. The detailed analysis of two satellite passes in the evening (midnight) MLT sector in the conditions of predominantly northward (westward) ionospheric electric field show that inverted V-associated electrodynamical pattern was the same in both events. Model calculations summarizing all the above ionosphere-satellite results within the limits of unified electrodynamical scheme show that a) meridional ionospheric (Hall+Pedersen) closing current direction is a decisive factor controlling the direction of currents in the meridional Birkeland current loop of the inverted V. A summarizing interpretative scheme is proposed of the hierarchy of meridional Birkeland current loops, larger one encircling single, or multiple, smaller ones: zone 2/zone 1 large-scale current loop, inverted V current loops, and auroral arc-associated current loops, all with the same direction of the ionospheric closing current, northward in the evening and southward in the morning

  13. Multiscale and cross entropy analysis of auroral and polar cap indices during geomagnetic storms

    Science.gov (United States)

    Gopinath, Sumesh; Prince, P. R.

    2016-01-01

    In order to improve general monoscale information entropy methods like permutation and sample entropy in characterizing the irregularity of complex magnetospheric system, it is necessary to extend these entropy metrics to a multiscale paradigm. We propose novel multiscale and cross entropy method for the analysis of magnetospheric proxies such as auroral and polar cap indices during geomagnetic disturbance times. Such modified entropy metrics are certainly advantageous in classifying subsystems such as individual contributions of auroral electrojets and field aligned currents to high latitude magnetic perturbations during magnetic storm and polar substorm periods. We show that the multiscale entropy/cross entropy of geomagnetic indices vary with scale factor. These variations can be attributed to changes in multiscale dynamical complexity of non-equilibrium states present in the magnetospheric system. These types of features arise due to imbalance in injection and dissipation rates of energy with variations in magnetospheric response to solar wind. We also show that the multiscale entropy values of time series decrease during geomagnetic storm times which reveals an increase in temporal correlations as the system gradually shifts to a more orderly state. Such variations in entropy values can be interpreted as the signature of dynamical phase transitions which arise at the periods of geomagnetic storms and substorms that confirms several previously found results regarding emergence of cooperative dynamics, self-organization and non-Markovian nature of magnetosphere during disturbed periods.

  14. X-Ray Probes of Jupiter's Auroral Zones, Galilean Moons, and the Io Plasma Torus

    Science.gov (United States)

    Elsner, R. F.; Ramsey, B. D.; Swartz, D. A.; Rehak, P.; Waite, J. H., Jr.; Cooper, J. F.; Johnson, R. E.

    2005-01-01

    Remote observations from the Earth orbiting Chandra X-ray Observatory and the XMM-Newton Observatory have shown the the Jovian system is a rich and complex source of x-ray emission. The planet's auroral zones and its disk are powerful sources of x-ray emission, though with different origins. Chandra observations discovered x-ray emission from the Io plasma torus and from the Galilean moons Io, Europa, and possibly Ganymede. The emission from the moons is due to bombardment of their surfaces by highly energetic magnetospheric protons, and oxygen and sulfur ions, producing fluorescent x-ray emission lines from the elements in their surfaces against an intense background continuum. Although very faint when observed from Earth orbit, an imaging x-ray spectrometer in orbit around the icy Galilean moons would provide a detail mapping of the elemental composition in their surfaces. Here we review the results of Chandra and XMM-Newton observations of the Jovian system and describe the characteristics of X-MIME, an imaging x-ray spectrometer undergoing study for possible application to future missions to Jupiter such as JIMO. X-MIME has the ultimate goal of providing detailed high-resolution maps of the elemental abundances of the surfaces of Jupiter's icy moons and Io, as well as detailed study of the x-ray mission from the Io plasma torus, Jupiter's auroral zones, and the planetary disk.

  15. Shape-Constrained Sparse and Low-Rank Decomposition for Auroral Substorm Detection.

    Science.gov (United States)

    Yang, Xi; Gao, Xinbo; Tao, Dacheng; Li, Xuelong; Han, Bing; Li, Jie

    2016-01-01

    An auroral substorm is an important geophysical phenomenon that reflects the interaction between the solar wind and the Earth's magnetosphere. Detecting substorms is of practical significance in order to prevent disruption to communication and global positioning systems. However, existing detection methods can be inaccurate or require time-consuming manual analysis and are therefore impractical for large-scale data sets. In this paper, we propose an automatic auroral substorm detection method based on a shape-constrained sparse and low-rank decomposition (SCSLD) framework. Our method automatically detects real substorm onsets in large-scale aurora sequences, which overcomes the limitations of manual detection. To reduce noise interference inherent in current SLD methods, we introduce a shape constraint to force the noise to be assigned to the low-rank part (stationary background), thus ensuring the accuracy of the sparse part (moving object) and improving the performance. Experiments conducted on aurora sequences in solar cycle 23 (1996-2008) show that the proposed SCSLD method achieves good performance for motion analysis of aurora sequences. Moreover, the obtained results are highly consistent with manual analysis, suggesting that the proposed automatic method is useful and effective in practice. PMID:25826810

  16. Correlated low-frequency electric and magnetic noise along the auroral field lines

    Science.gov (United States)

    Gurnett, D. A.; Huff, R. L.; Menietti, J. D.; Burch, J. L.; Winningham, J. D.; Shawhan, S. D.

    1984-01-01

    Dynamics Explorer 1 measurements of intense low-frequency electric and magnetic noise observed at low altitudes over the auroral zone are described. The intensity of both the electric and magnetic fields decreases rapidly with increasing frequency. Most of the energy is at frequencies below the O(+) cyclotron frequency, and some evidence is found for a cutoff or change in spectral slope near that frequency. The magnetic to electric field ratio decreases rapidly with increasing radial distance and also decreases with increasing frequency. The polarization of the electric field in a plane perpendicular to the earth's magnetic field is essentially random. The transverse electric and magnetic fields are closely correlated, with the average Poynting flux directed toward the earth. The total electromagnetic power flow associated with the noise is substantial. Two general models are discussed to interpret these observations, one based on static electric and magnetic fields imbedded in the ionosphere and the other based on Alfven waves propagating along the auroral field lines.

  17. Development and performance of a suprathermal electron spectrometer to study auroral precipitations.

    Science.gov (United States)

    Ogasawara, Keiichi; Grubbs, Guy; Michell, Robert G; Samara, Marilia; Stange, Jason L; Trevino, John A; Webster, James; Jahn, Jörg-Micha

    2016-05-01

    The design, development, and performance of Medium-energy Electron SPectrometer (MESP), dedicated to the in situ observation of suprathermal electrons in the auroral ionosphere, are summarized in this paper. MESP employs a permanent magnet filter with a light tight structure to select electrons with proper energies guided to the detectors. A combination of two avalanche photodiodes and a large area solid-state detector (SSD) provided 46 total energy bins (1 keV resolution for 3-20 keV range for APDs, and 7 keV resolution for >20 keV range for SSDs). Multi-channel ultra-low power application-specific integrated circuits are also verified for the flight operation to read-out and analyze the detector signals. MESP was launched from Poker Flat Research Range on 3 March 2014 as a part of ground-to-rocket electrodynamics-electrons correlative experiment (GREECE) mission. MESP successfully measured the precipitating electrons from 3 to 120 keV in 120-ms time resolution and characterized the features of suprathermal distributions associated with auroral arcs throughout the flight. The measured electrons were showing the inverted-V type spectra, consistent with the past measurements. In addition, investigations of the suprathermal electron population indicated the existence of the energetic non-thermal distribution corresponding to the brightest aurora. PMID:27250414

  18. Low-energy ion precipitation structures associated with pulsating auroral patches

    Science.gov (United States)

    Liang, Jun; Donovan, E.; Nishimura, Y.; Yang, B.; Spanswick, E.; Asamura, K.; Sakanoi, T.; Evans, D.; Redmon, R.

    2015-07-01

    Pulsating auroras often appear in forms of geo-stable or slowly convecting "patches." These patches can maintain their rough shape and size over many sequences of luminosity pulsations, yet they slowly drift with ionospheric E × B convection. Because of these characteristics, there has long been a speculation that the pulsating auroral patch (PAP) is connected to flux tubes filled with enhanced cold plasma. In this study, we perform a survey on pulsating auroral events when the footprints of low-Earth-orbit satellites traversed the PAPs, with a focus on the low-energy particle signatures associated with the PAPs. As a result, we identified, in a majority (~2/3) of events, the existence of a low-energy ion precipitation structure that is collocated with the PAP, with core energies ranging from several tens of eV up to a few hundred eV. This result supports the hypothesis that a PAP connects to flux tubes filled with enhanced cold plasma. We further propose that the plasma outflows from the ionosphere are the origin of such cold plasma flux tubes. We suggest that the PAP is formed by a combination of high-energy electrons of a magnetospheric origin, the low-energy plasma structure of an ionospheric origin, and certain ELF/VLF waves that are intensified and modulated in interactions with both the hot and cold plasma populations.

  19. Auroral Current and Electrodynamics Structure (ACES) Observations of Ionospheric Feedback in the Alfven Resonator

    Science.gov (United States)

    Cohen, Ian J.; Lessard, Marc; Lund, Eric J.; Bounds, Scott R.; Kletzing, Craig; Kaeppler, Stephen R.; Sigsbee, Kristine M.; Streltsov, Anatoly V.; Labelle, James W.; Dombrowski, Micah P.; Pfaff, Robert F.; Rowland, Doug; Jones, Sarah; Anderson, Brian Jay; Heinselman, Craig J.; Gjerloev, Jesper W.; Dudok de Wit, Thierry

    2011-01-01

    In 2009, the Auroral Current and Electrodynamics Structure (ACES) High and Low sounding rockets were launched from the Poker Flat Rocket Range (PFRR) in Alaska, with the science objective of gathering in-situ data to quantify current closure in a discrete auroral arc. As ACES High crossed through the return current of an arc (that was monitored using an all sky camera from the ground at Fort Yukon), its instruments recorded clear Alfv nic signatures both poleward and equatorward of the return current region, but not within the main region of the return current itself. These data provide an excellent opportunity to study ionospheric feedback and how it interacts with the Alfv n resonator. We compare the observations with predictions and new results from a model of ionospheric feedback in the ionospheric Alfv n resonator (IAR) and report the significance and impact of these new data for the Magnetosphere-Ionosphere Coupling in the Alfv n Resonator (MICA) rocket mission to launch from PFRR this winter. MICA s primary science objectives specifically focus on better understanding the small-scale structure that the model predicts should exist within the return current region.

  20. 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.

  1. A right atrial mass, patent foramen ovale, and indwelling central venous catheter in a patient with a malignancy: a diagnostic and therapeutic dilemma.

    Science.gov (United States)

    Funt, Samuel; Lerakis, Stamatios; McLean, Dalton S; Willis, Patrick; Book, Wendy; Martin, Randolph P

    2010-04-01

    A 33-year-old woman with a history of gestational trophoblastic disease presented for investigation of a right atrial mass. She had been receiving chemotherapy administered via a Port-a-Cath system for 2 months prior to presentation. On transesophageal echocardiography and magnetic resonance imaging, she was found to have a mass attached to the right atrial free wall, with a segment projecting across a patent foramen ovale. Because of the risk for an embolic event, the mass was surgically removed and the patent foramen ovale repaired. Pathology showed an organized thrombus. This case emphasizes the need for high suspicion for thrombus when a right atrial mass is found in a patient with a hypercoagulable state due to underlying malignancy who has a central venous catheter. PMID:19879732

  2. Incremental Value of Three-Dimensional Transesophageal Echocardiography over the Two-Dimensional Technique in the Assessment of a Thrombus in Transit through a Patent Foramen Ovale.

    Science.gov (United States)

    Thind, Munveer; Ahmed, Mustafa I; Gok, Gulay; Joson, Marisa; Elsayed, Mahmoud; Tuck, Benjamin C; Townsley, Matthew M; Klas, Berthold; McGiffin, David C; Nanda, Navin C

    2015-05-01

    We report a case of a right atrial thrombus traversing a patent foramen ovale into the left atrium, where three-dimensional transesophageal echocardiography provided considerable incremental value over two-dimensional transesophageal echocardiography in its assessment. As well as allowing us to better spatially characterize the thrombus, three-dimensional transesophageal echocardiography provided a more quantitative assessment through estimation of total thrombus burden. PMID:25827179

  3. A Case of Cryptogenic Stroke Associated with Patent Foramen Ovale Coexisting with Pulmonary Embolisms, Deep Vein Thromboses, and Renal Artery Infarctions

    OpenAIRE

    Park, Moon-Sik; Park, Jong-Pil; Yun, So-Hee; Lee, Jae-Un; Kim, Joong-Keun; Lee, Na-Eun; Song, Ji-Eun; Lee, Shin-Eun; John, Sung-Hee; Lim, Ji-Hyun; Rhew, Jay-Young

    2012-01-01

    A paradoxical embolism is defined as a systemic arterial embolism requiring the passage of a venous thrombus into the arterial circulatory system through a right-to-left shunt, and is commonly related to patent foramen ovale (PFO). However, coexisting pulmonary embolisms, deep vein thromboses (DVT), and multipe systemic arterial embolisms, associated with PFO, are rare. Here, we report a patient who had a cryptogenic ischemic stroke, associated with PFO, which is complicated with a massive pu...

  4. The ears of the African elephant: unexpected high seroprevalence of Plasmodium ovale and Plasmodium malariae in healthy populations in Western Africa

    OpenAIRE

    Doderer-Lang, Cécile; Atchade, Pascal S; Meckert, Lydia; Haar, Elodie; Perrotey, Sylvie; Filisetti, Denis; Aboubacar, Ahmed; Alexander W Pfaff; Brunet, Julie; Chabi, Nicodème W; Akpovi, Casimir D; Anani, Ludovic; Bigot, André; Sanni, Ambaliou; Candolfi, Ermanno

    2014-01-01

    Background Malaria Is A Life-Threatening Pathology In Africa. Plasmodium Falciparum And Plasmodium Vivax Attract The Most Focus Because Of Their High Prevalence And Mortality. Knowledge About The Prevalence Of The Cryptic Pathogens Plasmodium Ovale And Plasmodium Malariae Is Limited. Thanks To Recombinant Tools, Their Seroprevalence Was Measured For The First Time, As Well As The Prevalence Of Mixed Infections In A Malaria-Asymptomatic Population In Benin, A Malaria-Endemic Country. Methods A...

  5. Epidemiologic characteristics of Plasmodium ovale in China in 2011-2014%2011-2014年中国卵形疟原虫流行特征

    Institute of Scientific and Technical Information of China (English)

    周升; 肖宁; 李中杰

    2016-01-01

    目的:分析2011—2014年中国输入性单纯卵形疟原虫感染病例(卵形疟输入病例)流行特征,为我国消除阶段制订卵形疟防治策略提供科学依据。方法在全国疾病监测信息报告管理系统中收集2011—2014年的卵形疟个案(临床与实验室病例)和人口数据,从寄生虫病防治信息管理系统中收集2011—2014年卵形疟病例的流行病学调查数据(仅含输入病例)(不包括中国香港、澳门、台湾以及外籍病例)。分析卵形疟输入病例的流行病学特征、诊断和报告情况。结果2011—2014年,中国共报告卵形疟输入病例373例,年龄的P50(P25~P75)为40(32~46)岁,2011—2014年分别报告单纯卵形疟病例为17、35、123和198例,呈逐年上升的趋势;男性为367例(98.4%),女性为6例(1.6%)。2011—2014年中国卵形疟输入病例前5位的省份分别是江苏(100例)、广西(76例)、河南(55例)、安徽(28例)、山东(18例)。中国共有21个省份的182个县报告了卵形疟输入病例,感染地来自非洲的病例有353例(94.6%)。综合医院、CDC和传染病院报告卵形疟输入病例分别占40.0%(149例)、37.8%(141例)和16.6%(62例)。卵形疟输入病例发病到诊断耗时的P50(P25~P75)为4(2~8)d。结论2011—2014年,中国卵形疟输入病例的数量逐年增加,发生范围不断扩大,发病到诊断耗时较长;输入性单纯卵形疟的诊断和规范治疗以及复发病例需引起重视。%Objective To investigate the epidemiological characteristics of Plasmodium ovale in 2011-2014 for malaria control policy making during the phase of malaria elimination in China. Methods The data of individual Plasmodium ovale case (probable and confirmed) and population during 20011-2014 were collated from China National Notifiable Infectious Disease Reporting Information System, and the data of epidemiological

  6. Ultrastructure of oval cells in children with chronic hepatitis B, with special emphasis on the stage of liver fibrosis: The first pediatric study

    Institute of Scientific and Technical Information of China (English)

    Maria Elzbieta Sobaniec-Lotowska; Joanna Maria Lotowska; Dariusz Marek Lebensztejn

    2007-01-01

    AIM: To investigate the ultrastructure of oval ceils in children with chronic hepatitis B, with special emphasis on their location in areas of collagen fibroplasia.METHODS: Morphological investigations were conducted on biopsy material obtained from 40 children,aged 3-16 years with chronic hepatitis B. The stage of fibrosis was assessed histologically using the arbitrary semiquantitative numerical scoring system proposed by Ishak et al. The material for ultrastructural investigation was fixed in glutaraldehyde and paraformaldehyde and processed for transmission-electron microscopic analysis.RESULTS: Ultrastructural examination of biopsy specimens obtained from children with chronic hepatitis B showed the presence of two types of oval cells, the hepatic progenitor cells and intermediate hepatic-like cells. These cells were present in the parenchyma and were seen most commonly in areas of intense periportal fibrosis (at least stage 2 according to Ishak et al) and in the vicinity of the limiting plate of the lobule. The activated nonparenchymal hepatic cells, i.e. transformed hepatic stellate cells and Kupffer cells were seen in close proximity to the intermediate hepatic-like cells.CONCLUSION: We found a distinct relationship between the prevalence of oval cells (hepatic progenitor cells and intermediate hepatocyte-like cells) and fibrosis stage in pediatric patients with chronic hepatitis B.

  7. The challenge of diagnosing Plasmodium ovale malaria in travellers: report of six clustered cases in french soldiers returning from West Africa

    Directory of Open Access Journals (Sweden)

    Deparis Xavier

    2010-12-01

    Full Text Available Abstract Background Plasmodium ovale is responsible for 5% of imported malaria in French travellers. The clinical and biological features of six clustered cases of P. ovale malaria in an army unit of 62 French soldiers returning from the Ivory Coast are reported. Case report All patients were symptomatic and developed symptoms on average 50 days after their return and 20 days after the end of chemoprophylaxis (doxycycline. Clinical features included fever (6/6, mostly tertian (4/6, aches (6/6, nausea (3/6, abdominal pain (2/6, diarrhoea (2/6, or cough (2/6. Thrombocytopaenia was lower than 100,000/mm3 in half the cases only, and the haemoglobin count was normal for all patients. The diagnosis was made after at least three thick and thin blood smear searches. Parasitaemia was always lower than 0.5%. All rapid diagnostic tests were negative for HRP2 and pLDH antigens. Discussion Plasmodium ovale malaria is currently a problem to diagnose in travellers, notably in French soldiers returning from the Ivory Coast. Early attempts at diagnosis are difficult due to the lack of specific clinical features, the rarity of biological changes and the poor sensitivity of diagnostic tools to detect low parasitaemia. Thus, the diagnosis is commonly delayed or missed. Physicians should be aware of this diagnostic challenge to avoid relapses and provide prompt and adequate treatment with chloroquine and radical cure with primaquine.

  8. GPS phase scintillation associated with optical auroral emissions:first statistical results from the geographic South Pole

    OpenAIRE

    Kinrade, Joe; Mitchell, Cathryn N; Smith, Nathan D.; Ebihara, Yusuke; Weatherwax, Allan T.; Bust, Gary S.

    2013-01-01

    Ionospheric irregularities affect the propagation of Global Navigation Satellite System (GNSS) signals, causing radio scintillation. Particle precipitation from the magnetosphere into the ionosphere, following solar activity, is an important production mechanism for ionospheric irregularities. Particle precipitation also causes the aurorae. However, the correlation of aurorae and GNSS scintillation events is not well established in literature. This study examines optical auroral events during...

  9. Forame oval patente e acidente vascular cerebral isquêmico em jovens: associação causal ou estatística? Patent foramen ovale and ischemic stroke in young people: statistical association or causal relation?

    Directory of Open Access Journals (Sweden)

    Edson Marcio Negrão

    2007-05-01

    Full Text Available OBJETIVOS: Determinar se há evidências de uma relação causal entre forame oval patente (FOP e acidente vascular cerebral isquêmico (AVCI criptogênico em jovens. Analisar essa relação à luz dos critérios de causalidade. MÉTODOS: Avaliaram-se, retrospectivamente, 168 pacientes jovens com AVCI, divididos em dois grupos: criptogênico e de causa definida. Como parte da rotina, os pacientes foram submetidos a pesquisa de FOP por ecocardiograma transesofágico e/ou Doppler transcraniano, ambos associados ao teste de bolhas. Demonstrada a associação estatística univariada entre FOP e AVCI, procedeu-se a análise multivariada. RESULTADOS: Após análise multivariada, a associação FOP e AVCI criptogênico mostrou-se ainda estatisticamente significante, com razão de chance (RCajustada de 3,3 (IC95% 1,5-7,4. O número total de lesões no encéfalo também apresentou associação significativa com o AVCI criptogênico (RCajustada= 0,4 IC95% 0,2-0,9. A associação FOP e AVCI criptogênico satisfez todos os critérios de causalidade. CONCLUSÃO: A relação causal entre o FOP e o AVCI criptogênico em jovens é altamente provável. Esse fato deve ser considerado na decisão terapêutica.OBJECTIVES: To determine if there are evidences of a causal relation between patent foramen ovale (PFO x cryptogenic ischemic stroke (IS in the young population and to analyze this relation in terms of causal criteria. METHODS: A total of 168 young patients with IS was retrospectively evaluated and divided into two groups: cryptogenic and with a defined cause. As a routine procedure, the patients underwent investigation of the PFO by means of transesophageal echocardiogram and/or transcranial Doppler sonography, both of them associated with the bubble test. Multivariate analysis was performed after demonstration of univariate statistical association between PFO x IS. RESULTS: After multivariate analysis, the association between PFO x cryptogenic IS was still

  10. Patent foramen ovale in a cohort of young patients with cryptogenic ischemic stroke Forame oval patente em uma coorte de pacientes jovens com acidente vascular cerebral isquêmico

    Directory of Open Access Journals (Sweden)

    Marcus Tulius T. Silva

    2005-06-01

    Full Text Available OBJECTIVE: Although its role is a matter of debate, some studies described a higher prevalence of patent foramen ovale (PFO and atrial septal aneurysm (ASA in young stroke patients, with higher risk with PFO / ASA association (OR 4.96. The aim of this study was determine the prevalence of PFO and ASA in a cohort of cryptogenic ischemic stroke (IS patients younger than 55 years and to follow-up after surgical or percutaneous endovascular closure (PEC. METHOD: In 21 months we identified all patients less than 55 years old with IS who were admitted to our hospital. Cryptogenic IS was considered if there is not an identifiably cause to cerebral ischemia. Transesophageal echocardiography (TEE was performed in all patients. After interatrial septal abnormalities diagnosis, percutaneous device closure was offered to all. Patients were followed monthly and keeped with oral AAS or Clopidogrel. RESULTS: We identified 189 patients with IS and 32 were less than 55 years old (16.9%. In 29 the IS was cryptogenic. TEE was performed in all patients and some form of interatrial septal abnormality was identified in 12 (12/29 - 41.3%; 5 had a PFO and in 7 there was PFO plus ASA. Ten patients were submitted to PEC and 2 were submitted to surgical closure. In mid-term follow-up (28 months no ischemic events occurred and 2 patients related disappearance of migraine symptoms. CONCLUSION: Our small series description is in accordance with other studies and suggests a possible relation between interatrial septal abnormalities and IS in a cohort of young patient.OBJETIVO: A associação das anormalidades do septo interatrial - forame oval patente (FOP e aneurisma de septo interatrial (ASA - com acidente vascular cerebral isquêmico (AVCI ainda é questão de incerteza para muitos autores. No entanto, vários estudo mostram que em pacientes jovens tais anormalidades podem estar relacionadas à gênese de eventos isquêmicos. Nosso objetivo é descrever a prevalência do

  11. Ion shell distributions as free energy source for plasma waves on auroral field lines mapping to plasma sheet boundary layer

    Directory of Open Access Journals (Sweden)

    A. Olsson

    2004-06-01

    Full Text Available Ion shell distributions are hollow spherical shells in velocity space that can be formed by many processes and occur in several regions of geospace. They are interesting because they have free energy that can, in principle, be transmitted to ions and electrons. Recently, a technique has been developed to estimate the original free energy available in shell distributions from in-situ data, where some of the energy has already been lost (or consumed. We report a systematic survey of three years of data from the Polar satellite. We present an estimate of the free energy available from ion shell distributions on auroral field lines sampled by the Polar satellite below 6 RE geocentric radius. At these altitudes the type of ion shells that we are especially interested in is most common on auroral field lines close to the polar cap (i.e. field lines mapping to the plasma sheet boundary layer, PSBL. Our analysis shows that ion shell distributions that have lost some of their free energy are commonly found not only in the PSBL, but also on auroral field lines mapping to the boundary plasma sheet (BPS, especially in the evening sector auroral field lines. We suggest that the PSBL ion shell distributions are formed during the so-called Velocity Dispersed Ion Signatures (VDIS events. Furthermore, we find that the partly consumed shells often occur in association with enhanced wave activity and middle-energy electron anisotropies. The maximum downward ion energy flux associated with a shell distribution is often 10mWm-2 and sometimes exceeds 40mWm-2 when mapped to the ionosphere and thus may be enough to power many auroral processes. Earlier simulation studies have shown that ion shell distributions can excite ion Bernstein waves which, in turn, energise electrons in the parallel direction. It is possible that ion shell distributions are the link between the X-line and the auroral wave activity and electron

  12. 基于宏程序的椭球面加工刀路算法%Macroprogram-based Algorithms of Tool Trajectory for Cutting Oval Sphere Surface

    Institute of Scientific and Technical Information of China (English)

    胡翔云; 肖仁

    2013-01-01

      椭球形、球形表面在现代机械生产中比较常见,这类特征需要数控加工。使用计算机自动编程时,程序修改不方便,加工程序编制时间长。通过分析椭球形电极表面加工工艺,分别给出球刀、立铣刀、牛鼻刀加工椭球表面的刀路算法、参数方程及适用范围。并以球刀层切椭球面为例,采用两个嵌套的循环语句编制宏程序,可使用G65指令调用,相当于给数控系统增加了一个固定循环功能,实现了该类零件加工程序的参数化,提高了加工程序的编制速度,可用于椭球、球类零件表面的铣削加工。通过一个具体实例对宏程序进行了验证。%Oval sphere and spherical surface are often seen in modern machinery manufacturing,and numerical control (NC) machining is required for this kind of characteristics. When computer used for automatic programming,modification of a program is not easy,and a long period of time is taken for writing the cutting program. By analyzing the cutting technology for oval sphere surface of an electrode,the algorithm of tooltrajectory,parameter equation and applicable scope were given separately for the ball tool,vertical milling tool and cownose tool for cutting oval sphere surface. Moreover by taking an example of layer cutting of oval sphere surface with ball tool,a macroprogram was wrote with two embedded circulate sentences. It could be invoked by G65 code,which was equivalent to add a fixed circular function to the NC system. The parameterization of cutting program for this kind of parts is realized,and writing speed for the cutting program is improved. It can be used for milling and cutting parts with oval sphere and spherical surface. The macroprogram is verified by a detailed practical example.

  13. On the current-voltage relationship in auroral breakups and westwards-travelling surges

    Directory of Open Access Journals (Sweden)

    A. Olsson

    Full Text Available Auroral precipitating electrons pass through an acceleration region before entering the atmosphere. Regardless of what produces it, a parallel electric field is assumed to cause the acceleration. It is well known that from kinetic theory an expression for the corresponding upward field-aligned current can be calculated, which under certain assumptions can be linearized to j=KV. The K constant, referred to as the Lyons-Evans-Lundin constant, depends on the source density and thermal energy of the magnetospheric electrons; it is an important parameter in magnetosphere-ionosphere coupling models. However, the K parameter is still rather unknown, and values are found in a wide range of 10–8–10–10 S m–2. In this study, we investigated how the type of auroral structure affects the K values. We look at onset and westwards-travelling surge (WTS events and make comparisons with earlier results from observations of more stable auroral arcs. A new analysis technique for studying those magnetospheric parameters using ground-based measurements is introduced. Electron density measurements are taken with the EISCAT radar, and through an inversion technique the flux-energy spectra are calculated. Source densities, thermal energies and potential drops are estimated from fittings of accelerated Maxwellian distributions. With this radar technique we have the possibility to study the changes of the mentioned parameters during the development of onsets and the passage of surges over EISCAT. The study indicates that the linearization of the full Knight formulation holds even for the very high potential drops and thermal temperatures found in the dynamic onset and WTS events. The values of K are found to be very low, around 10–11 S m–2 in onset cases as well as WTS events. The results may establish a new technique where ionospheric

  14. 24/7 Solar Minimum Polar Cap and Auroral Ion Temperature Observations

    Science.gov (United States)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig; Bilitza, Dieter

    2011-01-01

    During the International Polar Year (IPY) two Incoherent Scatter Radars (ISRs) achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the International Reference Ionosphere (IRI) a fiduciary E- and F-region ionosphere description for solar minimum conditions in both the auroral and polar cap regions. The ionospheric description being electron density, ion temperature and electron temperature profiles from as low as 90 km extending to several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.1 N latitude, 212.5 E longitude where the NSF s new Poker Flat Incoherent Scatter Radar (PFISR) is located. This location during solar minimum conditions is in the auroral region for most of the day but is at midlatitudes, equator ward of the cusp, for about 4-8 h per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78.2 N latitude, 16.0 E longitude where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap with a noon sector passage often through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be distinguished between quiet and disturbed geomagnetic conditions. During the IPY year, 1 March 2007 - 29 February 2008, about 50 solar wind Corotating Interaction Regions (CIRs) impacted geospace. Each CIR has a two to five day geomagnetic disturbance that is observed in the ESR and PFISR observations. Hence, this data set also enables the quiet-background ionospheric climatology to be established as a function of season and local time. These two separate climatologies for the ion temperature at an altitude of 300 km are presented and compared with IRI ion temperatures. The IRI ion temperatures are about 200-300 K hotter than the observed values. However, the MSIS neutral temperature at 300 km compares favorably

  15. Strategies for understanding and reducing the Plasmodium vivax and Plasmodium ovale hypnozoite reservoir in Papua New Guinean children: a randomised placebo-controlled trial and mathematical model.

    Directory of Open Access Journals (Sweden)

    Leanne J Robinson

    2015-10-01

    Full Text Available The undetectable hypnozoite reservoir for relapsing Plasmodium vivax and P. ovale malarias presents a major challenge for malaria control and elimination in endemic countries. This study aims to directly determine the contribution of relapses to the burden of P. vivax and P. ovale infection, illness, and transmission in Papua New Guinean children.From 17 August 2009 to 20 May 2010, 524 children aged 5-10 y from East Sepik Province in Papua New Guinea (PNG participated in a randomised double-blind placebo-controlled trial of blood- plus liver-stage drugs (chloroquine [CQ], 3 d; artemether-lumefantrine [AL], 3 d; and primaquine [PQ], 20 d, 10 mg/kg total dose (261 children or blood-stage drugs only (CQ, 3 d; AL, 3 d; and placebo [PL], 20 d (263 children. Participants, study staff, and investigators were blinded to the treatment allocation. Twenty children were excluded during the treatment phase (PQ arm: 14, PL arm: 6, and 504 were followed actively for 9 mo. During the follow-up time, 18 children (PQ arm: 7, PL arm: 11 were lost to follow-up. Main primary and secondary outcome measures were time to first P. vivax infection (by qPCR, time to first clinical episode, force of infection, gametocyte positivity, and time to first P. ovale infection (by PCR. A basic stochastic transmission model was developed to estimate the potential effect of mass drug administration (MDA for the prevention of recurrent P. vivax infections. Targeting hypnozoites through PQ treatment reduced the risk of having at least one qPCR-detectable P. vivax or P. ovale infection during 8 mo of follow-up (P. vivax: PQ arm 0.63/y versus PL arm 2.62/y, HR = 0.18 [95% CI 0.14, 0.25], p < 0.001; P. ovale: 0.06 versus 0.14, HR = 0.31 [95% CI 0.13, 0.77], p = 0.011 and the risk of having at least one clinical P. vivax episode (HR = 0.25 [95% CI 0.11, 0.61], p = 0.002. PQ also reduced the molecular force of P. vivax blood-stage infection in the first 3 mo of follow-up (PQ arm 1.90/y

  16. Fission of transactinide elements described in terms of generalized Cassinian ovals: Fragment mass and total kinetic energy distributions

    Science.gov (United States)

    Carjan, N.; Ivanyuk, F. A.; Oganessian, Yu.; Ter-Akopian, G.

    2015-10-01

    The total deformation energy at scission for Z = 100, 102, 104 and 106 isotopes is calculated using the Strutinsky's procedure and nuclear shapes described in terms of Cassinian ovals generalized by the inclusion of three additional shape parameters: α1, α4 and α6. The corresponding fragment-mass distributions are estimated supposing they are due to thermal fluctuations in the mass asymmetry degree of freedom. For these four series of isotopes the experimentally observed transition from asymmetric to symmetric fission, that happens with increasing mass number A, is qualitatively reproduced. In lighter isotopes (e.g. 254Fm and 254Rf) two mass-asymmetric fission modes are predicted to occur with comparable yields: one having relatively compact and the other relatively elongated scission configurations. On the other hand, in heavier isotopes (e.g. 264Fm and 264Rf) the fragment-mass distributions are predicted to be narrow single-peaked around A / 2 corresponding to essentially one mass-symmetric fission mode. The mass distributions are estimated separately for each fission mode, in the case of Fm and Rf isotopes, in order to display their inversion when A increases. Finally the distributions of the total kinetic energy of the fragments are calculated, for the same isotopes, in the point-charge approximation. Non-Gaussian shapes are obtained. With increasing mass number A, a transition from a distribution tailing towards higher energies to a distribution tailing towards lower energies and an increase of the difference in the peak positions of the two modes were observed; again in qualitative agreement with experimental data.

  17. Saline contrast echocardiography for the detection of patent foramen ovale in hypoxia: a validation study using intracardiac echocardiography.

    Science.gov (United States)

    Fenster, Brett E; Curran-Everett, Douglas; Freeman, Andrew M; Weinberger, Howard D; Kern Buckner, J; Carroll, John D

    2014-04-01

    Although the "3 beat rule" is widely utiized to discriminate patent foramen ovale (PFO)-mediated right-to-left shunt (RTLS) from intrapulmonary RTLS using saline contrast transthoracic echocardiography (SCE), SCE diagnostic performance has yet to be validated using an invasive intracardiac standard. Percutaneous PFO occluder placement was recently shown to ameliorate hypoxia in patients with suspected PFO-mediated RTLS. We evaluated the ability of SCE to predict PFO presence and size using intracardiac echocardiography (ICE) as a gold standard in a hypoxic cohort. Sixty-three hypoxic patients with suspected PFO-mediated RTLS who underwent SCE at rest, with Valsalva maneuver, and with cough prior to ICE were evaluated retrospectively. PFO RTLS was defined by ICE findings including PFO anatomy, RTLS by saline contrast and color Doppler, and probe patency. SCE shunt severity and timing of left heart saline target appearance were compared to the presence of ICE-defined PFO RTLS. Forty-seven patients (75%) met criteria for PFO-mediated RTLS. A 4 beat cutoff for resting SCE provided optimal diagnostic performance for detection of PFO-mediated RTLS with a 71% sensitivity, 94% specificity, and 97% positive predictive value (PPV). Valsalva and cough maneuvers improved sensitivity compared to rest SCE (89% and 80%, respectively). Valsalva SCE shunt severity more accurately predicted PFO size than resting SCE. In contrast to the widely accepted "3 beat rule," resting SCE for the detection of PFO RTLS in a hypoxic population performs optimally using a 4-cycle cutoff with both excellent specificity and PPV. PMID:24138568

  18. Short- and Mid-term Results of Atrial Septal Defect and Patent Foramen Ovale Occlusion with Starway Septal Occluder Device

    Directory of Open Access Journals (Sweden)

    J Kojuri

    2011-09-01

    Full Text Available Background: With a prevalence of almost 7% of all congenital heart diseases, atrial septal defect (ASD is a common condition. Patent foramen ovale (PFO is also a congenital heart disease which is frequently sustained into adulthood. Objectives: To study the feasibility of closure of ASD and PFU by Starway septal occluder device and the incidence of its inherent complications and procedural failure in 62 patients referred to our center. Methods: Starway septal occluder device was used for closure of ASD and PFO in 62 patients. After left and right heart catheterization, transesophageal echocardiography-guided closure was done for the patients with immediate recording of the results. Patients were followed for 6 months by transesophageal echocardiography for observing short- and mid-term complications. Results: The 62 studied patients were categorized into 2 groups. Group 1 included 31 patients (64% females with ASD (mean±SD age: 26.7±7.6 years. Group 2 consisted of 31 patients (35.6% females with PFO (mean±SD age: 53.5±12.4 years. Size of the right ventricle (RV annulus was significantly (P=0.005 decreased after the intervention in the ASD group. Overall 5 (8% patients developed post-intervention complications (transient ischemic attack, leg edema, and residual shunt and procedural failure—4 (13% in ASD group and 1 (3% in PFO group. None of the patients developed device-related thrombosis, significant arrhythmia, aortic regurgitation and pericardial effusion after intervention. Conclusion: Starway occluder device is effective and safe with very low short- and mid-term complication rates.

  19. Urotensin-II-Mediated Reactive Oxygen Species Generation via NADPH Oxidase Pathway Contributes to Hepatic Oval Cell Proliferation.

    Directory of Open Access Journals (Sweden)

    XiaoTong Yu

    Full Text Available Urotensin II (UII, a somatostatin-like cyclic peptide, is involved in tumor progression due to its mitogenic effect. Our previous study demonstrated that UII and its receptor UT were up-regulated in human hepatocellular carcinoma (HCC, and exogenous UII promoted proliferation of human hepatoma cell line BEL-7402. Hepatic progenitor cell (HPCs are considered to be one of the origins of liver cancer cells, but their relationship with UII remains unclear. In this work, we aimed to investigate the effect of UII on ROS generation in HPCs and the mechanisms of UII-induced ROS in promoting cell proliferation. Human HCC samples were used to examine ROS level and expression of NADPH oxidase. Hepatic oval cell line WB-F344 was utilized to investigate the underlying mechanisms. ROS level was detected by dihydroethidium (DHE or 2', 7'-dichlorofluorescein diacetate (DCF-DA fluorescent probe. For HCC samples, ROS level and expression of NADPH oxidase were significantly up-regulated. In vitro, UII also increased ROS generation and expression of NADPH oxidase in WB-F344 cells. NADPH oxidase inhibitor apocynin pretreatment partially abolished UII-increased phosphorylation of PI3K/Akt and ERK, expression of cyclin E/cyclin-dependent kinase 2. Cell cycle was then analyzed by flow cytometry and UII-elevated S phase proportion was inhibited by apocynin pretreatment. Finally, bromodeoxyuridine (Brdu incorporation assay showed that apocynin partially abolished UII induced cell proliferation. In conclusion, this study indicates that UII-increased ROS production via the NADPH oxidase pathway is partially associated with activation of the PI3K/Akt and ERK cascades, accelerates G1/S transition, and contributes to cell proliferation. These results showed that UII plays an important role in growth of HPCs, which provides novel evidence for the involvement of HPCs in the formation and pathogenesis of HCC.

  20. Contributions of Q-machine experiments to understanding auroral particle acceleration processes

    International Nuclear Information System (INIS)

    Experiments performed over the past 40 years on Q-machine plasma devices [N. Rynn and N. D'Angelo, Rev. Sci. Instrum. 31, 1326 (1960)] have contributed significantly to the basic understanding of plasma behavior. Many of these laboratory results are relevant to plasma processes in the Earth's ionosphere and magnetosphere. Here are reviewed examples in which Q-machine experiments contributed to understanding particle acceleration in the Earth's auroral energization region by discovering unexpected behavior, developing physical insight, benchmarking theoretical models, and establishing observational signatures relevant to space plasmas. Magnetic-field-aligned (parallel) electric fields, solitary structures, ion-cyclotron waves, ion-acoustic waves, Kelvin-Helmholtz waves, and lower-hybrid waves are discussed. The legacy of these contributions is a tribute to the Q-machine design

  1. Modulation of auroral electrojet currents using dual HF beams with ELF phase offset

    Science.gov (United States)

    Golkowski, M.; Cohen, M.; Moore, R. C.

    2012-12-01

    The modulation of naturally occuring ionospheric currents with high power radio waves in the high frequency (HF, 3-10 MHz) band is a well known technique for generation of extremely low frequency (ELF, 3-3000 Hz) and very low frequency (VLF, 3-30 kHz) waves. We use the heating facility of the High Frequency Active Auroral Research Program (HAARP) to investigate the effect of using dual HF beams with an ELF/VLF phase offset between the modulation waveforms. Experiments with offset HF beams confirm the model of independent ELF/VLF sources. Experiments with co-located HF beams exhibit interaction between the first and second harmonics of the modulated tones when square and sine wave modulation waveforms are employed. Using ELF/VLF phase offsets for co-loacted beams is also shown to be a potential diagnostic for the D-region ionospheric profile.

  2. The Ionospheric Model Adaptation to the Auroral Latitudes With UHF EISCAT Radar and Tromso Magnetometer Data

    Science.gov (United States)

    Nikolaeva, Vera; Gordeev, Evgeny; Kotikov, Andrey

    E-layer Auroral Ionosphere Model (E-AIM) developed in Arctic and Antarctic Research Institute can provide temporal and spatial distribution of the main ionosphere parameters: ion and electron density distribution in the altitude range from 90 to 150 km. The statistical study of E-layer electron density dependence on substorm activity was made to improve model results in high latitudes. About fifty substorms were included to the data analysis. Particular attention was paid to the dynamics of magnetic disturbances and ionospheric parameters measured by the radar. Correlation of electron density values measured by the UHF EISCAT incoherent scattering radar with geomagnetic indices was determined. Applicability of geomagnetic indices as input parameters of the local E-AIM model was estimated.

  3. Artificial stimulation of auroral electron acceleration by intense field aligned currents

    International Nuclear Information System (INIS)

    A cesium doped high explosion was detonated at 165 km altitude in the auroral ionosphere during quiet conditions. An Alfven wave pulse with a 200 mV/m electric field was observed with the peak occurring 135 ms after the explosion at a distance of about 1 km. The count rate of fixed energy 2 keV electron detectors abruptly increased at 140 ms, peaked at 415 ms and indicated a downward field aligned beam of accelerated electrons. An anomalously high field aligned beam of backscattered electrons was also detected. We interpret the acceleration as due to a production of an electrostatic shock or double layer between 300 and 800 km altitude. The structure was probably formed by an instability of the intense field aligned currents in the Alfven wave launched by the charge separation electric field due to the explosion

  4. Auroral electron fluxes induced by static magnetic field aligned electric field and plasma wave turbulence

    International Nuclear Information System (INIS)

    We have studied the formation of auroral electron fluxes induced by a field aligned dc electric field in the presence of plasma wave turbulence. The effect of the wave spectral shape on the production rate has been considered. This acceleration scheme was modelled by the weak turbulence approach. The electron fluxes for narrow and broad band spectra, in the case of low and high phase velocities, are calculated, and it is found as a general feature, for all modes, that their enhancement is larger the weaker the background electric field, while for its absolute enhancement it is just the opposite. The electron fluxes are enhanced by many orders of magnitude over that without turbulence. It is also shown that the modes enhance the runaway production rate via their Cherenkov dissipation, and that a synergetic effect occurs in the enhancement when more than one mode turbulent is present in the acceleration region. (author)

  5. On the importance of doubly charged ions in the auroral ionosphere

    International Nuclear Information System (INIS)

    Consideration has been given to the auroral ionospheric O+ density dilemma as discussed by Donahue et al. (1970). If the temperature dependences of the reactions O++O2→O2++O and O++N2→NO++N are of the type found by Stubbe (1969) and Johnsen and Biondi (1973), the line of explanation invoking intense electric fields and high ion temperature faces serious trouble. This would make the O+ density problem all the more pathological. However, a simple explanation was possible in terms of O2++ and N2++ ion chemistry. The beauty of this explanation lay in the fact that neither high temperatures nor electric fields need be invoked. Physicochemical problems connected with the new explanation are discussed, and it is suggested that the properties of the doubly charged ions deserve a closer study in the laboratory

  6. Scintillation and loss of signal lock from poleward moving auroral forms in the cusp ionosphere

    CERN Document Server

    Oksavik, K; Lorentzen, D A; Baddeley, L J; Moen, J

    2016-01-01

    We present two examples from the cusp ionosphere over Svalbard,where poleward moving auroral forms (PMAFs) are causing significant phase scintillation in signals from navigation satellites. The data were obtained using a combination of ground-based optical instruments and a newly installed multiconstellation navigation signal receiver at Longyearbyen. Both events affected signals from GPS and Global Navigation Satellite System (GLONASS). When one intense PMAF appeared, the signal from one GPS spacecraft also experienced a temporary loss of signal lock. Although several polar cap patches were also observed in the area as enhancements in total electron content, the most severe scintillation and loss of signal lock appear to be attributed to very intense PMAF activity. This shows that PMAFs are locations of strong ionospheric irregularities, which at times may cause more severe disturbances in the cusp ionosphere for navigation signals than polar cap patches.

  7. Stellar wind-magnetosphere interaction at exoplanets: computations of auroral radio powers

    CERN Document Server

    Nichols, J D

    2016-01-01

    We present calculations of the auroral radio powers expected from exoplanets with magnetospheres driven by an Earth-like magnetospheric interaction with the solar wind. Specifically, we compute the twin cell-vortical ionospheric flows, currents, and resulting radio powers resulting from a Dungey cycle process driven by dayside and nightside magnetic reconnection, as a function of planetary orbital distance and magnetic field strength. We include saturation of the magnetospheric convection, as observed at the terrestrial magnetosphere, and we present power law approximations for the convection potentials, radio powers and spectral flux densities. We specifically consider a solar-age system and a young (1 Gyr) system. We show that the radio power increases with magnetic field strength for magnetospheres with saturated convection potential, and broadly decreases with increasing orbital distance. We show that the magnetospheric convection at hot Jupiters will be saturated, and thus unable to dissipate the full av...

  8. Kinetic model for an auroral double layer that spans many gravitational scale heights

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Scott [Department of Physics, University of Colorado, Boulder, Colorado 80309-0390 (United States)

    2014-12-15

    The electrostatic potential profile and the particle densities of a simplified auroral double layer are found using a relaxation method to solve Poisson's equation in one dimension. The electron and ion distribution functions for the ionosphere and magnetosphere are specified at the boundaries, and the particle densities are found from a collisionless kinetic model. The ion distribution function includes the gravitational potential energy; hence, the unperturbed ionospheric plasma has a density gradient. The plasma potential at the upper boundary is given a large negative value to accelerate electrons downward. The solutions for a wide range of dimensionless parameters show that the double layer forms just above a critical altitude that occurs approximately where the ionospheric density has fallen to the magnetospheric density. Below this altitude, the ionospheric ions are gravitationally confined and have the expected scale height for quasineutral plasma in gravity.

  9. Separating spatial and temporal variations in auroral electric and magnetic fields by Cluster multipoint measurements

    Directory of Open Access Journals (Sweden)

    T. Karlsson

    2004-07-01

    Full Text Available Cluster multipoint measurements of the electric and magnetic fields from a crossing of auroral field lines at an altitude of 4RE are used to show that it is possible to resolve the ambiguity of temporal versus spatial variations in the fields. We show that the largest electric fields (of the order of 300mV/m when mapped down to the ionosphere are of a quasi-static nature, unipolar, associated with upward electron beams, stable on a time scale of at least half a minute, and located in two regions of downward current. We conclude that they are the high-altitude analogues of the intense return current/black auroral electric field structures observed at lower altitudes by Freja and FAST. In between these structures there are temporal fluctuations, which are shown to likely be downward travelling Alfvén waves. The periods of these waves are 20-40s, which is not consistent with periods associated with either the Alfvénic ionospheric resonator, typical field line resonances or substorm onset related Pi2 oscillations. The multipoint measurements enable us to estimate a lower limit to the perpendicular wavelength of the Alfvén waves to be of the order of 120km, which suggests that the perpendicular wavelength is similar to the dimension of the region between the two quasi-static structures. This might indicate that the Alfvén waves are ducted within a wave guide, where the quasi-static structures are associated with the gradients making up this waveguide.

  10. The thermospheric auroral red line polarization: confirmation of detection and first quantitative analysis

    Directory of Open Access Journals (Sweden)

    Moen Joran

    2013-01-01

    Full Text Available The thermospheric atomic oxygen red line is among the brightest in the auroral spectrum. Previous observations in Longyearbyen, Svalbard, indicated that it may be intrinsically polarized, but a possible contamination by light pollution could not be ruled out. During the winter 2010/2011, the polarization of the red line was measured for the first time at the Polish Hornsund polar base without contamination. Two methods of data analysis are presented to compute the degree of linear polarization (DoLP and angle of linear polarization (AoLP: one is based on averaging and the other one on filtering. Results are compared and are in qualitative agreement. For solar zenith angles (SZA larger than 108° (with no contribution from Rayleigh scattering, the DoLP ranges between 2 and 7%. The AoLP is more or less aligned with the direction of the magnetic field line, in agreement with the theoretical predictions of Bommier et al. (2010. However, the AoLP values range between ±20° around this direction, depending on the auroral conditions. Correlations between the polarization parameters and the red line intensity I were considered. The DoLP decreases when I increases, confirming a trend observed during the observations in Longyearbyen. However, for small values of I, DoLP varies within a large range of values, while for large values of I, DoLP is always small. The AoLP also varies with the red line intensity, slightly rotating around the magnetic field line.

  11. Modeling the Perpendicular Electric Field Structure in the Vicinity of Auroral Precipitation Arcs

    Science.gov (United States)

    de Boer, J. D.; Noel, J. A.; Perron, P.; St-Maurice, J.

    2012-12-01

    We have developed a model of auroral electrodynamics which allows one to quantitatively understand the relationship between parallel electric currents and precipitation-induced conductivity gradients. The latitudinal structure of the modeled perpendicular electric field strength also generally conforms to observed structure. However the magnitude of the perpendicular electric field perturbations around an auroral arc is not well reproduced by the model, and we believe the discrepancy lies in one or more of three avenues we are now exploring: first, the effect of shear-modified current-driven, electrostatic ion-acoustic instability on the parallel current density; second, the role of the non-linear, inertial term in the electron momentum balance; third, the finite energy available below any given altitude to support the perpendicular electric field and the finite propagation time required to access energy from higher in the magnetosphere. These three areas of physics have required improvements to our model. The first two physical factors require us to consider a non-Ohmic relationship between the parallel electric field and the parallel current density. The third factor has required us to adopt a time-dependent method of solution for the electric field and the magnetic field disturbance, rather than the time-independent solution of the scalar electric potential with time-dependent conductivities that we had heretofore employed. Additionally, all of these new aspects of physics have required significant changes in our code to raise the practical upper boundary for the top of the domain. This has had to be done while not losing the advantage our model has of solving the time-dependent, coupled ionosphere-thermosphere-electrodynamics with a sub-kilometre resolution in latitude within the E-region, and while also avoiding any loss in L-shell resolution while achieving this increase in domain height. Some preliminary results are presented and compared with observations.

  12. Results of the Jupiter Infrared Auroral Mapper from the Juno Earth fly-by

    Science.gov (United States)

    Adriani, A.; Mura, A.; Filacchione, G.; Di Iorio, T.; Turrini, D.; Noschese, R.; Cicchetti, A.; Grassi, D.; Sindoni, G.; Zambelli, M.; Piccioni, G.; Capria, M. T.; Tosi, F.; Orosei, R.; Dinelli, B. M.; Moriconi, M. L.; Lunine, J. I.

    2013-12-01

    The InfraRed Auroral Mapper (JIRAM) is simultaneously an imager and a spectrometer on board of the Juno mission. Jupiter's reflected and emitted light in the range 2-5 μm can be sensed through its spectral channel and H3+ emissions analyzed to retrieve auroral parameters. JIRAM is also able to map the infrared Jupiter aurora in the 3.5 μm and planet's thermal emissions in the 5 μm wavelength ranges through its L-band and M-band imager filters . The main scientific goals are the study of auroras, hot spots and other Jupiter atmospheric structures detectable in its working spectral range. Concurrently with the Juno Earth fly-by, that will occur on October 9th of this current year, JIRAM will observe the Moon during its transit approaching the Earth. As the instrument's temperature cannot be actively controlled, operating with a passive cooling system, the Earth will not be observed during the closest approach. A dramatic temperature increase of the instrument, far above its performance limit, is expected in fact by the illumination of the instrument's cooling radiators due to our planet reflection of the solar illumination. The Moon will be the only chance for an extended target observation that JIRAM can experience before Jupiter. Consequently, this opportunity is of pivotal importance being the only chance for a real in-flight test to verify the instrument performances and the radiometric calibration in real observational set up. The instrument will be operated in the same functional configuration that it will use at Jupiter. So far, the only absolute radiometric calibration has been performed in lab during the on ground calibration and functional test sessions. The internal calibration unit is mainly devoted to the spectral calibration checking while the absolute radiometric calibration has to verified and confirmed in flight. Results of lunar observations will be presented.

  13. The Jovian Auroral Distributions Experiment (JADE) on the Juno Mission to Jupiter

    Science.gov (United States)

    McComas, D. J.; Alexander, N.; Allegrini, F.; Bagenal, F.; Beebe, C.; Clark, G.; Crary, F.; Desai, M. I.; De Los Santos, A.; Demkee, D.; Dickinson, J.; Everett, D.; Finley, T.; Gribanova, A.; Hill, R.; Johnson, J.; Kofoed, C.; Loeffler, C.; Louarn, P.; Maple, M.; Mills, W.; Pollock, C.; Reno, M.; Rodriguez, B.; Rouzaud, J.; Santos-Costa, D.; Valek, P.; Weidner, S.; Wilson, P.; Wilson, R. J.; White, D.

    2013-05-01

    The Jovian Auroral Distributions Experiment (JADE) on Juno provides the critical in situ measurements of electrons and ions needed to understand the plasma energy particles and processes that fill the Jovian magnetosphere and ultimately produce its strong aurora. JADE is an instrument suite that includes three essentially identical electron sensors (JADE-Es), a single ion sensor (JADE-I), and a highly capable Electronics Box (EBox) that resides in the Juno Radiation Vault and provides all necessary control, low and high voltages, and computing support for the four sensors. The three JADE-Es are arrayed 120∘ apart around the Juno spacecraft to measure complete electron distributions from ˜0.1 to 100 keV and provide detailed electron pitch-angle distributions at a 1 s cadence, independent of spacecraft spin phase. JADE-I measures ions from ˜5 eV to ˜50 keV over an instantaneous field of view of 270∘×90∘ in 4 s and makes observations over all directions in space each 30 s rotation of the Juno spacecraft. JADE-I also provides ion composition measurements from 1 to 50 amu with m/Δm˜2.5, which is sufficient to separate the heavy and light ions, as well as O+ vs S+, in the Jovian magnetosphere. All four sensors were extensively tested and calibrated in specialized facilities, ensuring excellent on-orbit observations at Jupiter. This paper documents the JADE design, construction, calibration, and planned science operations, data processing, and data products. Finally, the Appendix describes the Southwest Research Institute [SwRI] electron calibration facility, which was developed and used for all JADE-E calibrations. Collectively, JADE provides remarkably broad and detailed measurements of the Jovian auroral region and magnetospheric plasmas, which will surely revolutionize our understanding of these important and complex regions.

  14. Substorm related changes in precipitation in the dayside auroral zone – a multi instrument case study

    Directory of Open Access Journals (Sweden)

    A. J. Kavanagh

    Full Text Available A period (08:10–14:40 MLT, 11 February 1997 of enhanced electron density in the D- and E-regions is investigated using EISCAT, IRIS and other complementary instruments. The precipitation is determined to be due to substorm processes occurring close to magnetic midnight. Energetic electrons drift eastward after substorm injection and precipitate in the morning sector. The precipitation is triggered by small pulses in the solar wind pressure, which drive wave particle interactions. The characteristic energy of precipitation is inferred from drift timing on different L-shells and apparently verified by EISCAT measurements. The IMF influence on the precipitation in the auroral zone is also briefly discussed. A large change in the precipitation spectrum is attributed to increased numbers of ions and much reduced electron fluxes. These are detected by a close passing DMSP satellite. The possibility that these ions are from the low latitude boundary layer (LLBL is discussed with reference to structured narrow band Pc1 waves observed by a search coil magnetometer, co-located with IRIS. The intensity of the waves grows with increased distance equatorward of the cusp position (determined by both satellite and HF radar, contrary to expectations if the precipitation is linked to the LLBL. It is suggested that the ion precipitation is, instead, due to the recovery phase of a small geomagnetic storm, following on from very active conditions. The movement of absorption in the later stages of the event is compared with observations of the ionospheric convection velocities. A good agreement is found to exist in this time interval suggesting that E × B drift has become the dominant drift mechanism over the gradient-curvature drift separation of the moving absorption patches observed at the beginning of the morning precipitation event.

    Key words. Ionosphere (auroral ionosphere; particle precipitation Magnetospheric physics (storms and substorms

  15. Multi-Instrumental Vector Magnetic Observations and Techniques for Investigating Auroral Dynamics

    Science.gov (United States)

    Redmon, Robert; Knipp, Delores; Kilcommons, Liam; Richmond, Art; Matsuo, Tomoko; Anderson, Brian; Korth, Haje; Slavin, James; Le, Guan; Wilson, Gordon; Rich, Fred; Denig, William

    2014-05-01

    Space based magnetometers in highly inclined low earth orbits are essential for characterizing the state of the auroral space environment and the dynamic processes within. This paper demonstrates the utility of data derived from multiple satellites including AMPERE (70 Iridium spacecraft), DMSP (4 spacecraft) and ST5 (3 spacecraft), and the AMIENext technique to investigate periods of interest in 2006 and 2010. A new satellite conjunction-finding technique magnetically maps in situ observations to a common altitude in the APEX coordinate system to assess the spatial and temporal stability and quality of vector magnetic measurements (Knipp et al., 2014). In March of 2006, the ST5 constellation was launched into a pearls-on-a-string configuration. Subsequent data processing produced superb, quality controlled magnetic observations from the 90-day mission (e.g. Slavin et al., 2008, Le et al., 2009; Wang et al., 2009). We present conjunction comparisons between the ST5 and DMSP spacecraft during the ST5 mission lifetime, which was dominated by a series of high-speed solar wind events. In May of 2010, a unipolar Magnetic Cloud passed Earth, providing an opportunity to investigate the magnetopshere-ionosphere coupling response to a slow moving transient followed by higher speed flow. This event included significant, long-lived disturbances in the asymmetric ring current and auroral electrojet (AE) index. Assimilation of space-based magnetic observations via the AMIENext procedure, reveal twisting in the dayside patterns, consistent with the sign changes in IMF By and a highly structured topology as IMF Bz turned northward. We present a detailed comparison between the magnetic observations from DMSP and AMPERE. To aid in investigating the local magnetic field and in providing data to assimilative models, we have also created new datasets in self-describing NASA CDF formats for the DMSP and ST5 vector magnetometers and for the DMSP precipitating ion and electron

  16. Reconstruction of three-dimensional auroral ionospheric conductivities via an assimilative technique

    Science.gov (United States)

    McGranaghan, R. M.; Knipp, D. J.; Matsuo, T.; Solomon, S. C.

    2015-12-01

    Energy redistribution in the magnetosphere-ionosphere-thermosphere (MIT) system is largely controlled by a complex system of field-aligned, Hall, and Pedersen currents, and the electrodynamics underlying their distributions. Application of Ohm's law to the auroral zone requires knowledge of the ionospheric conductivity, whose estimation has often been simplified by invoking Maxwellian behavior of the impacting particles and height independent conductance. Though these assumptions have allowed us to study height-integrated conductivities (conductances), they have also limited our ability to understand how the MIT system operates as a whole. We are now in a position to address conductivity variations, and thus energy redistribution, in three dimensions. We present an objective analysis of the fully three-dimensional (3-D) ionospheric Hall and Pedersen auroral conductivities for the November 30, 2011 coronal mass ejection event. We show: 1) a fundamental picture of ionospheric conductivity variability organized into empirical orthogonal functions [McGranaghan et al., 2015; accepted] and 2) an event reconstruction of the ionospheric conductivities. Figure 1 provides a proof of concept for part 1 by showing the first primary mode of variability (EOF1) of the Hall conductivity at four altitudes through the E- and lower F-regions. Our reconstruction relies on a data assimilation scheme that optimally combines Defense Meteorological Satellite Program (DMSP) satellite observations with an error covariance model created from the conductivity EOFs. We find significant 3-D structure in the ionospheric conductivities that can drastically modify the E- and lower F-region behavior. We suggest an exciting opportunity to extend these analyses to other data sets, such as the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC).

  17. Experimental investigation of auroral generator regions with conjugate Cluster and FAST data

    Directory of Open Access Journals (Sweden)

    O. Marghitu

    2006-03-01

    Full Text Available Here and in the companion paper, Hamrin et al. (2006, we present experimental evidence for the crossing of auroral generator regions, based on conjugate Cluster and FAST data. To our knowledge, this is the first investigation that concentrates on the evaluation of the power density, E·J, in auroral generator regions, by using in-situ measurements. The Cluster data we discuss were collected within the Plasma Sheet Boundary Layer (PSBL, during a quiet magnetospheric interval, as judged from the geophysical indices, and several minutes before the onset of a small substorm, as indicated by the FAST data. Even at quiet times, the PSBL is an active location: electric fields are associated with plasma motion, caused by the dynamics of the plasma-sheet/lobe interface, while electrical currents are induced by pressure gradients. In the example we show, these ingredients do indeed sustain the conversion of mechanical energy into electromagnetic energy, as proved by the negative power density, E·J<0. The plasma characteristics in the vicinity of the generator regions indicate a complicated 3-D wavy structure of the plasma sheet boundary. Consistent with this structure, we suggest that at least part of the generated electromagnetic energy is carried away by Alfvén waves, to be dissipated in the ionosphere, near the polar cap boundary. Such a scenario is supported by the FAST data, which show energetic electron precipitation conjugated with the generator regions crossed by Cluster. A careful examination of the conjunction timing contributes to the validation of the generator signatures.

  18. The relationship between VHF radar auroral backscatter amplitude and Doppler velocity: a statistical study

    Directory of Open Access Journals (Sweden)

    B. A. Shand

    Full Text Available A statistical investigation of the relationship between VHF radar auroral backscatter intensity and Doppler velocity has been undertaken with data collected from 8 years operation of the Wick site of the Sweden And Britain Radar-auroral Experiment (SABRE. The results indicate three different regimes within the statistical data set; firstly, for Doppler velocities <200 m s–1, the backscatter intensity (measured in decibels remains relatively constant. Secondly, a linear relationship is observed between the backscatter intensity (in decibels and Doppler velocity for velocities between 200 m s–1 and 700 m s–1. At velocities greater than 700 m s–1 the backscatter intensity saturates at a maximum value as the Doppler velocity increases. There are three possible geophysical mechanisms for the saturation in the backscatter intensity at high phase speeds: a saturation in the irregularity turbulence level, a maximisation of the scattering volume, and a modification of the local ambient electron density. There is also a difference in the dependence of the backscatter intensity on Doppler velocity for the flow towards and away from the radar. The results for flow towards the radar exhibit a consistent relationship between backscatter intensity and measured velocities throughout the solar cycle. For flow away from the radar, however, the relationship between backscatter intensity and Doppler velocity varies during the solar cycle. The geometry of the SABRE system ensures that flow towards the radar is predominantly associated with the eastward electrojet, and flow away is associated with the westward electrojet. The difference in the backscatter intensity variation as a function of Doppler velocity is attributed to asymmetries between the eastward and westward electrojets and the geophysical parameters controlling the backscatter amplitude.

  19. Inductive electric fields in the magnetotail and their relation to auroral and substorm phenomena

    International Nuclear Information System (INIS)

    The paper reviews the importance of inductive electric fields in explaining different magnetospheric and auroral phenomena during moderately and highly distrubed conditions. Quiet-time particle energization and temporal development of the tail structure during the substorm growth phase are explained by the presence of a large-scale elctrostatic field directed from dawn to dusk over the magentotail. Conservation of the first adiabatic invariant in the neutral sheet with a small value of the gradient in the magnetic field implies that the longitudical energy increases at each crossing of the neutral sheet. At a certain moment, this may result in a rapid local growth of the current and in an instability that triggers the onset. During the growth phase energy is stored in the magnetic field, since the energy density in the electric field is negligible compared to that of the magnetic field. An analytical model is described in which the characteristic observations of a substorm onset are taken into account. One major feature is that the triggering is confined to a small local time sector. During moderate disturbances, the induction fields in the magnetotail are stronger by at least one order of magnitude than the average cross-tail field. Temporal development of the disturbed area results in X- and O-type neutral lines. Particles near to these neutral lines are energized to over 1 MeV energies within a few seconds, due to an effective combination of linear and betatron acceleration. The rotational property of the induction field promotes energization in a restricted area wiht dimensions equivalent to a few Earth's radii. The model also predicts the existence of highly localized cable-type field-aligned currents appearing on the eastern and western edges of the expanding auroral bulge

  20. Reconstruction of energetic electron spectra in the upper atmosphere: balloon observations of auroral X-rays coordinated with measurements from the EISCAT radar

    International Nuclear Information System (INIS)

    Energetic electron precipitation in the auroral zone has been studied using coordinated auroral X-ray measurements from balloons, altitude profiles of the ionospheric electron density measured by the EISCAT radar above the balloons, and cosmic noise absorption data from the Scandinavian riometer network. The data were obtained during the Coordinated EISCAT and Balloon Observations (CEBO) campaign in August 1984. The energy spectral variations of both the X-ray fluxes and the primary precipitating electrons were examined for two precipitation events in the morning sector. As far as reasonably can be concluded from observations of magnetic activity in the auroral zone, and from the temporal development of the energy spectra, the two precipitation events can be interpreted in the frame of present models of energetic electron precipitation on the mordning side of the auroral zone. 96 refs., 70 figs., 11 tabs

  1. Patent foramen ovale

    Science.gov (United States)

    ... air bubbles will be seen moving from the right to left side of the heart. ... leg veins) breaks free and travels to the right side of the heart. ... to the brain and become stuck there, preventing blood flow to ...

  2. Factors associated with shunt dynamic in patients with cryptogenic stroke and patent foramen ovale: an observational cohort study

    Directory of Open Access Journals (Sweden)

    Allendörfer Jens

    2011-08-01

    Full Text Available Abstract Background As previously reported there is evidence for a reduction in right to left shunt (RLS in stroke patients with patent foramen ovale (PFO. This occurs predominantly in patients with cryptogenic stroke (CS. We therefore analysed factors associated with a shunt reduction on follow-up in stroke patients suffering of CS. Methods On index event PFO and RLS were proven by transesophageal echocardiography and contrast-enhanced transcranial Doppler-sonography (ce-TCD. Silent PE was proved by ventilation perfusion scintigraphy (V/Q within the stroke work-up on index event; all scans were re-evaluated in a blinded manner by two experts. The RLS was re-assessed on follow-up by ce-TCD. A reduction in shunt volume was defined as a difference of ≥20 microembolic signals (MES or the lack of evidence of RLS on follow-up. For subsequent analyses patients with CS were considered; parameters such as deep vein thrombosis (DVT and silent pulmonary embolism (PE were analysed. Results In 39 PFO patients suffering of a CS the RLS was re-assessed on follow-up. In all patients (n = 39 with CS a V/Q was performed; the median age was 40 years, 24 (61.5% patients were female. In 27 patients a reduction in RLS was evident. Silent PE was evident in 18/39 patients (46.2%. Factors such as atrial septum aneurysm, DVT or even silent PE were not associated with RLS dynamics. A greater time delay from index event to follow-up assessment was associated with a decrease in shunt volume (median 12 vs. 6 months, p = 0.013. Conclusions In patients with CS a reduction in RLS is not associated with the presence of a venous embolic event such as DVT or silent PE. A greater time delay between the initial and the follow-up investigation increases the likelihood for the detection of a reduction in RLS.

  3. Integrated approach to run 4-1/2 inches casing in 6-3/4 inches open hole with high ovalization trend formation

    Energy Technology Data Exchange (ETDEWEB)

    Maestri, Gustavo; Ochoa, Francisco [Weatherford International de Argentina S.A. (Argentina); Garbers, Martin [Total Austral S.A., Buenos Aires (Argentina)

    2012-07-01

    The objective of this document is to present the fit-for-purpose solution implemented to solve major problems related to running production casing to bottom, while dealing with abnormally stressed formations in horizontal wells. The geomechanical behavior of abnormally stressed formations might lead to formation breakout, widely known as borehole ovalization. Severe ovalization of the borehole while drilling has a major impact in the friction between casing strings and the open hole. When the overall friction force overcomes the buckling limit of the tubular, the string will not go any further. This was the case during the pilot phase of the tight sand campaign in the central part of the Neuquen Basin (Argentina). The first three wells were drilled, during which several stuck pipe situations, including casing running problems. Even when some changes in the design were effectively implemented to deal with the ovalization problem during these first three wells; the fourth well of the campaign almost ended catastrophically; nearly half of the horizontal lateral remained uncased due to a stuck casing event during the conventional running operation. Running the production casing was identified as the weak point of the overall operation. Well design's robustness was severely criticized and the further development of the project was almost jeopardized. This is remarked to illustrate the importance of the problem. The real step change that took place after this major problem consisted of re-engineering the whole casing running operation in order to rotate and ream-in the casing string down to bottom. Even when this practice is extensively applied in some regions, it had not been considered nor applied before in the basin. Furthermore, this successfully implemented solution gave the project the necessary strength to validate its development. (author)

  4. Right-to-left interatrial shunt secondary to right hemidiaphragmatic paralysis: an unusual scenario for urgent percutaneous closure of patent foramen ovale.

    Science.gov (United States)

    Fabris, Tommaso; Buja, Paolo; Cucchini, Umberto; D'Amico, Gianpiero; Cazzuffi, Riccardo; Balestro, Elisabetta; Tarantini, Giuseppe

    2015-04-01

    A 66 year-old female presented with a refractory hypoxaemia in association with an isolated paralysis of the right hemidiaphragm. Transoesophageal echocardiography (TEE) with both colour Doppler and bubble test demonstrated a significant patent foramen ovale (PFO)-mediated right-to-left shunt (RTLS) without an increased interatrial pressure gradient. The PFO was urgently closed by deployment of an AMPLATZER(®) occluder device, resulting in complete recovery of the arterial oxygen saturation and patient's symptoms. As noted on TEE, the RTLS was due to redirection of blood flow from the inferior vena cava directly through the PFO secondary to distortion of the cardiac anatomy by right hemidiaphragmatic paralysis. PMID:25499594

  5. H3(+) fundamental band in Jupiter's auroral zones at high resolution from 2400 to 2900 inverse centimeters

    International Nuclear Information System (INIS)

    Following the previous detection of H3(+) in the southern auroral zone of Jupiter from its 2nu2 band, a search was made for the fundamental at 4 microns. Up to 42 lines of this band were detected in emission, at high resolution, on the auroral spot of each hemisphere. A rotational temperature was derived for the southern and northern zones, respectively, of 1000 + or - 40K and 835 + or - 50 K. The intensity of the lines was on the average two times stronger in the south than in the north. The 2nu2 band, which was sought in the north only on this occasion, was not detectable. A purely thermal mechanism for the H3(+) production is implied. Spatial extension and temporal variability of the excitation is discussed. 20 refs

  6. Effect of excess superthermal hot electrons on finite amplitude ion-acoustic solitons and supersolitons in a magnetized auroral plasma

    Energy Technology Data Exchange (ETDEWEB)

    Rufai, O. R., E-mail: rrufai@csir.co.za [Council for Scientific and Industrial Research, Pretoria (South Africa); Bharuthram, R., E-mail: rbharuthram@uwc.ac.za [University of the Western Cape, Bellville (South Africa); Singh, S. V., E-mail: satyavir@iigs.iigm.res.in; Lakhina, G. S., E-mail: lakhina@iigs.iigm.res.in [Indian Institute of Geomagnetism, New Panvel (W), Navi, Mumbai-410218 (India)

    2015-10-15

    The effect of excess superthermal electrons is investigated on finite amplitude nonlinear ion-acoustic waves in a magnetized auroral plasma. The plasma model consists of a cold ion fluid, Boltzmann distribution of cool electrons, and kappa distributed hot electron species. The model predicts the evolution of negative potential solitons and supersolitons at subsonic Mach numbers region, whereas, in the case of Cairn's nonthermal distribution model for the hot electron species studied earlier, they can exist both in the subsonic and supersonic Mach number regimes. For the dayside auroral parameters, the model generates the super-acoustic electric field amplitude, speed, width, and pulse duration of about 18 mV/m, 25.4 km/s, 663 m, and 26 ms, respectively, which is in the range of the Viking spacecraft measurements.

  7. Ion and electron injection in ionosphere and magnetosphere. Application to the parallel electric field measurement in auroral zones

    International Nuclear Information System (INIS)

    New methods of measuring parallel electric field in auroral zones are investigated in this thesis. In the studied methods, artificial injection of ions Li+ and electrons from a spacecraf is used. Measurements obtained during the ARAKS experiment are also presented. The behaviour of the ionospheric plasma located few hundred meters from a 0,5A electron beam injected in ionosphere from a rocket is studied, together with the behaviour of a Cs plasma artificially injected from the same spacecraft

  8. Enhanced E-layer ionization in the auroral zones observed by radio occultation measurements onboard CHAMP and Formosat-3/COSMIC

    OpenAIRE

    Mayer, C.; Jakowski, N.

    2009-01-01

    Particle precipitation of magnetospheric origin causes additional ionization in the auroral zone at E-layer heights. During night-time, in particular at winter-night, the E-layer ionization may dominate over the F2-layer ionization level. To study the geophysical conditions and characteristics of the related ionospheric processes in more detail, we use GPS radio occultation electron density profile retrievals from CHAMP and Formosat-3/COSMIC to extract thos...

  9. Forecasting of DST index from auroral electrojet indices using time-delay neural network + particle swarm optimization

    Science.gov (United States)

    Lazzús, J. A.; López-Caraballo, C. H.; Rojas, P.; Salfate, I.; Rivera, M.; Palma-Chilla, L.

    2016-05-01

    In this study, an artificial neural network was optimized with particle swarm algorithm and trained to predict the geomagmetic DST index one hour ahead using the past values of DST and auroral electrojet indices. The results show that the proposed neural network model can be properly trained for predicting of DST(t + 1) with acceptable accuracy, and that the geomagnetic indices used have influential effects on the good training and predicting capabilities of the chosen network.

  10. An interpretation for the bipolar electric field structures parallel to the magnetic field observed in the auroral ionosphere

    OpenAIRE

    Jiankui Shi; M. N. S. Qureshi; K. Torkar; Dunlop, M.; Zhenxing Liu; Zhang, T. L.

    2008-01-01

    A physical model for the existence of bipolar structures in the electric field that are parallel to the magnetic field and observed in the auroral ionosphere, is established by deriving the "Sagdeev potential" from the two-fluid equations in a cylindrical coordinate system. The model shows that the bipolar electric field structure can develop not only from an ion acoustic wave, but also from an ion cyclotron wave, when the Mach number and the initial electric field satisfy certain c...

  11. Effect of auroral substorms on the ionospheric range spread-F enhancements at high southern midlatitudes using real time vertical-sounding ionograms

    Science.gov (United States)

    Hajkowicz, Lech A.

    2016-03-01

    A comprehensive study has been undertaken on the effect of magnetic substorm onsets (as deduced from the auroral hourly electrojet AE-index) on the occurrence of high midlatitude (or sub-auroral latitude) ionospheric range spread-F (Sr). Unlike the previous reports real-time ionograms were used in this analysis thus eliminating ambiguities stemming from the correlating secondary evidence of spread-F with auroral substorms. The Australian southernmost ionosonde station Hobart (51.6°S geom.) proved to be uniquely suitable for the task as being sufficiently close to the southern auroral zone. Sr was assigned in km to each hourly nighttime ionogram at two sounding frequencies: Sr1 (at 2 MHz) and Sr2 (at 6 MHz) for four months in 2002: January and June (representing southern summer and winter solstices), and March and September (representing autumn and vernal equinoxes). It is evident that the southern winter solstitial period (June) is associated with high endemic midlatitude spread-F activity. All other seasons are closely linked with temporal sequences of enhanced spread-F activity following substorm onsets. For the first time it was possible not only find a simultaneous occurrence pattern of these diverse phenomena but to deduce numerical characteristics of the response of midlatitude ionosphere to the global auroral stimulus. Excellent case events, hitherto unpublished, are shown illustrating the presence of the AE peaks (in nT) being ahead of Sr peaks (in km) by a time shift ∆t (in h). Sr1 magnitude showed a significant correlation with the magnitudes of the preceding AE with a correlation coefficient (r) of 0.51 (probability of the occurrence by chance less than 0.01). Sr2 peaks were more sensitive to auroral disturbances but were not correlated with the AE magnitude variations. The time shift (∆t) was on average 4 h with a standard deviation of 3 h. The general pattern in the occurrence of magnetic substorms and spread-F is very similar. A number of

  12. The APIS service : a tool for accessing value-added HST planetary auroral observations over 1997-2015

    Science.gov (United States)

    Lamy, L.; Henry, F.; Prangé, R.; Le Sidaner, P.

    2015-10-01

    The Auroral Planetary Imaging and Spectroscopy (APIS) service http://obspm.fr/apis/ provides an open and interactive access to processed auroral observations of the outer planets and their satellites. Such observations are of interest for a wide community at the interface between planetology, magnetospheric and heliospheric physics. APIS consists of (i) a high level database, built from planetary auroral observations acquired by the Hubble Space Telescope (HST) since 1997 with its mostly used Far-Ultraviolet spectro- imagers, (ii) a dedicated search interface aimed at browsing efficiently this database through relevant conditional search criteria (Figure 1) and (iii) the ability to interactively work with the data online through plotting tools developed by the Virtual Observatory (VO) community, such as Aladin and Specview. This service is VO compliant and can therefore also been queried by external search tools of the VO community. The diversity of available data and the capability to sort them out by relevant physical criteria shall in particular facilitate statistical studies, on long-term scales and/or multi-instrumental multispectral combined analysis [1,2]. We will present the updated capabilities of APIS with several examples. Several tutorials are available online.

  13. The presence of large sunspots near the central solar meridian at the times of modern Japanese auroral observations

    Directory of Open Access Journals (Sweden)

    D. M. Willis

    2006-10-01

    Full Text Available The validity of a technique developed by the authors to identify historical occurrences of intense geomagnetic storms, which is based on finding approximately coincident observations of sunspots and aurorae recorded in East Asian histories, is corroborated using more modern sunspot and auroral observations. Scientific observations of aurorae in Japan during the interval 1957–2004 are used to identify geomagnetic storms that are sufficiently intense to produce auroral displays at low geomagnetic latitudes. By examining white-light images of the Sun obtained by the Royal Greenwich Observatory, the Big Bear Solar Observatory, the Debrecen Heliophysical Observatory and the Solar and Heliospheric Observatory spacecraft, it is found that a sunspot large enough to be seen with the unaided eye by an "experienced" observer was located reasonably close to the central solar meridian immediately before all but one of the 30 distinct Japanese auroral events, which represents a 97% success rate. Even an "average" observer would probably have been able to see a sunspot with the unaided eye before 24 of these 30 events, which represents an 80% success rate. This corroboration of the validity of the technique used to identify historical occurences of intense geomagnetic storms is important because early unaided-eye observations of sunspots and aurorae provide the only possible means of identifying individual historical geomagnetic storms during the greater part of the past two millennia.

  14. Possible evidence for partial demagnetization of electrons in the auroral E-region plasma during electron gas heating

    Directory of Open Access Journals (Sweden)

    C. Haldoupis

    Full Text Available A previous study, based on incoherent and coherent radar measurements, suggested that during auroral E-region electron heating conditions, the electron flow in the auroral electrojet undergoes a systematic counterclockwise rotation of several degrees relative to the E×B direction. The observational evidence is re-examined here in the light of theoretical predictions concerning E-region electron demagnetization caused by enhanced anomalous cross-field diffusion during strongly-driven Farley-Buneman instability. It is shown that the observations are in good agreement with this theory. This apparently endorses the concept of wave-induced diffusion and anomalous electron collision frequency, and consequently electron demagnetization, under circumstances of strong heating of the electron gas in the auroral electrojet plasma. We recognize, however, that the evidence for electron demagnetization presented in this report cannot be regarded as definitive because it is based on a limited set of data. More experimental research in this direction is thus needed.

  15. Estimates of the field-aligned current density in current-carrying filaments using auroral zone ground-based observations

    Directory of Open Access Journals (Sweden)

    M. A. Danielides

    Full Text Available We described the ground signatures of dynamic substorm features as observed by the imaging riometer, magnetometers and all-sky camera (ASC at Kilpisjärvi, Finland on 5 and 25 October 1999 during the late evening hours. The magnetometer data was consistent with the motion of up-ward field-aligned currents (FACs associated with absorption patches moving within the field of view of the riometer. We used riometer data in order to estimate the intensity of FACs associated with these local current-carrying filaments. It is shown that during these events, the estimated FAC intensity exceeds a threshold value that corresponds to the excitation of the low-frequency turbulence in the upper ionosphere. As a result, a quasi-oscillating regime of anomalous resistivity on the auroral field lines can give rise to the burst-like electron acceleration responsible for simultaneously observed auroral forms and bursts of Pi1B pulsations.

    Key words. Ionosphere (active experiments; auroral ionosphere; electric fields and currents

  16. Substorm processes in the geomagnetic tail and their effect in the nightside auroral zone ionosphere as observed by EISCAT

    International Nuclear Information System (INIS)

    Current understanding of magnetospheric substorms is reviewed with special emphasis on the relation between space-based and ground-based observations. Traditional means of monitoring substorms from the ground (by using magnetometers, riometers and auroral observations) give only a selective picture of the whole phenomenon, related to the precipitation of electrons with energies above 1 keV. Measurements by incoherent scatter radar, such as the European incoherent scatter facility (EISCAT), give a more complete and continuous picture. The 'neutral line' model of substorms provides a natural, physical basis on which relevant data can be interpreted. In this picture, two sources of flow are anticipated in the nightside auroral zones, one 'directly driven' (with a delay of 15-20 min) by the interplanetary magnetic field (IMF) Bz component and associated with dayside reconnection, and the other appearing typically an hour after southward turnings of the IMF and associated with rapid tail reconnection during substorms. Evidence for the influence of both sources of flow is found in nightside EISCAT data. These data also reveal that, overall, the nightside ionospheric flow and plasma parameters often vary in a quasi-periodic way with a period of ca. 1 h. In two cases in which concurrent interplanetary data are available it appears that the periodicity is inherent in IMF Bz, but this is not expressed unmodified in the auroral zone because of the presence of the two sources of flow which depend on IMF Bz in different ways. (author)

  17. Ion acoustic instability of HPT particles, FAC density, anomalous resistivity and parallel electric field in the auroral region

    Indian Academy of Sciences (India)

    C S Jayasree; G Renuka; C Venugopal

    2003-12-01

    During the magnetic storm of 21st March 1990, the DE-1 spacecraft encountered the auroral region at high invariant latitude at altitudes ranging from a few thousand kilometers in the ionosphere to many earth radii in the magnetosphere. The magnetic field perturbations interpretable as field aligned current (FAC) layers and the electrostatic turbulence possibly due to electrostatic ion acoustic instability driven by these currents are shown. The critical drift velocity of Hot Plasma Torus (HPT) electrons and the growth rate of ion acoustic wave as a function of electron to ion temperature ratio (/) for low and high current densities and energy of HPT electrons are found out. The intense FAC destabilizes the ion acoustic wave and the resultant electrostatic turbulence creates an anomalous resistivity. The current driven resistivity produces parallel electric field and high power dissipation. The anomalous resistivity , potential differnece along the auroral field lines ∥, intensity of electric field turbulence ∥ and power produced per unit volume are computed. It is found that the change in westward magnetic perturbation increases ∥; ; ∥ ;∥ and . Hence HPT electrons are heated and accelerated due to power dissipation during magnetically active periods in the auroral region. Concerning, applications, such HPT electrons can be used in particle accelerators like electron ring accelerator, smokatron etc.

  18. Controlling Charging and Arcing on a Solar Powered Auroral Orbiting Spacecraft

    Science.gov (United States)

    Ferguson, Dale C.; Rhee, Michael S.

    2008-01-01

    The Global Precipitation Measurement satellite (GPM) will be launched into a high inclination (65 degree) orbit to monitor rainfall on a global scale. Satellites in high inclination orbits have been shown to charge to high negative potentials, with the possibility of arcing on the solar arrays, when three conditions are met: a drop in plasma density below approximately 10,000 cm(exp -3), an injection of energetic electrons of energy more that 7-10 keV, and passage through darkness. Since all of these conditions are expected to obtain for some of the GPM orbits, charging calculations were done using first the Space Environment and Effects (SEE) Program Interactive Spacecraft Charging Handbook, and secondly the NASA Air-force Spacecraft Charging Analyzer Program (NASCAP-2k). The object of the calculations was to determine if charging was likely for the GPM configuration and materials, and specifically to see if choosing a particular type of thermal white paint would help minimize charging. A detailed NASCAP-2k geometrical model of the GPM spacecraft was built, with such a large number of nodes that it challenged the capability of NASCAP-2k to do the calculations. The results of the calculations were that for worst-case auroral charging conditions, charging to levels on the order of -120 to -230 volts could occur on GPM during night-time, with differential voltages on the solar arrays that might lead to solar array arcing. In sunlit conditions, charging did not exceed -20 V under any conditions. The night-time results were sensitive to the spacecraft surface materials chosen. For non-conducting white paints, the charging was severe, and could continue unabated throughout the passage of GPM through the auroral zone. Somewhat conductive (dissipative) white paints minimized the night-time charging to levels of -120 V or less, and thus were recommended for GPM thermal control. It is shown that the choice of thermal control paints is important to prevent arcing on high

  19. Multifunctional Oval Shape Gold Nanoparticle Based Selective Detection of Breast Cancer Cells Using Simple Colorimetric and Highly Sensitive Two-Photon Scattering Assay

    Science.gov (United States)

    Lu, Wentong; Arumugam, Sri Ranjini; Senapati, Dulal; Singh, Anant K.; Arbneshi, Tahir; Yu, Sadia Afrin Khan Hongtao; Ray, Paresh Chandra

    2010-01-01

    Breast cancer is the most common cancer among women and it is the second leading cause of cancer deaths in women today. The key to the effective and ultimately successful treatment of diseases such as cancer is an early and accurate diagnosis. Driven by the need, in this article, we report for the first time a simple colorimetric and highly sensitive two-photon scattering assay for highly selective and sensitive detection of breast cancer SK-BR-3 cell lines in 100-cells/ml level using multifunctional (monoclonal anti-HER2/c-erb-2 antibody and S6 RNA aptamers conjugated) oval shape gold nanoparticle based nanoconjugate. When multifunctional oval shape gold nanoparticles were mixed with breast cancer SK-BR-3 cell line, a distinct color change occurs and two-photon scattering intensity increases by about 13 times. Experimental data with HaCaT non-cancerous cell line, as well as with MDA-MB-231 breast cancer cell line clearly demonstrated that our assay was highly sensitive to SK-BR-3 and it was able to distinguish from other breast cancer cell line which expresses low levels of HER-2. The mechanism of selectivity and assay’s response change, have been discussed. Our experimental results reported here open up a new possibility of rapid, easy and reliable diagnosis of cancer cell lines by monitoring the colorimetric change and measuring TPS intensity from multifunctional gold nanosystems. PMID:20155973

  20. Heat and fluid flow characteristics of an oval fin-and-tube heat exchanger with large diameters for textile machine dryer

    Science.gov (United States)

    Bae, Kyung Jin; Cha, Dong An; Kwon, Oh Kyung

    2016-01-01

    The objectives of this paper are to develop correlations between heat transfer and pressure drop for oval finned-tube heat exchanger with large diameters (larger than 20 mm) used in a textile machine dryer. Numerical tests using ANSYS CFX are performed for four different parameters; tube size, fin pitch, transverse tube pitch and longitudinal tube pitch. The numerical results showed that the Nusselt number and the friction factor are in a range of -16.2 ~ +3.1 to -7.7 ~ +3.9 %, respectively, compared with experimental results. It was found that the Nusselt number linearly increased with increasing Reynolds number, but the friction factor slightly decreased with increasing Reynolds number. It was also found that the variation of longitudinal tube pitch has little effect on the Nusselt number and friction factor than other parameters (below 2.0 and 2.5 %, respectively). This study proposed a new Nusselt number and friction factor correlation of the oval finned-tube heat exchanger with large diameters for textile machine dryer.