WorldWideScience

Sample records for auroral oval

  1. Calculating Auroral Oval Pattern by AE Index

    Institute of Scientific and Technical Information of China (English)

    CHEN Anqin; LI Jiawei; YANG Guanglin; WANG Jingsong

    2008-01-01

    The relationship between the auroral oval pattern, i.e., location, size, shape, and intensity, and the auroral electrojet activity index (AE index) is studied. It is found that the maximal auroral intensity is elliptically distributed, and the lengths of semimajor and semiminor axes are positively correlated to AE.The intensity along the normal of the auroral oval can be satisfyingly described by a Gaussian distribution,and the maximum and the full width at half maximum of the Gaussian distribution are both positively correlated to AE. Based on these statistical results, a series of experimental formulas as a function of AE are developed to calculate the location, size, shape, and intensity of the auroral oval. These formulas are validated by the auroral images released by SWPC/NOAA.

  2. The discovery and the first studies of the auroral oval: A review

    Science.gov (United States)

    Feldstein, Y. I.

    2016-03-01

    The auroral oval concept radically changed the view that existed for a century in geophysics on the patterns in aurora planetary spatial-temporal distributions. The auroral zone, which is located around the geomagnetic pole as a continuous ring at a constant angular distance of ~23°, was replaced by the auroral oval in 1960. The auroral oval spatial position reflects the shape of the Earth's magnetosphere, which is compressed by the solar wind on the dayside and stretches into the magnetotail on the nightside. The oval is fixed relative to the direction toward the Sun and is located around the geomagnetic pole at altitudes of the upper atmosphere at an angular distance of ~12° at noon and ~23° at midnight. After an animated discussion over several subsequent years, the existence of the auroral oval was accepted by the scientific community as a paradigm of a new science, i.e., solar-terrestrial physics. The oval location indicates the zone where electron fluxes with energies varying from ~100 eV to ~20 keV precipitate into the upper atmosphere and is related to the structure of plasma domains in the Earth's magnetosphere. The paper describes the scientific studies that resulted in the concept of the auroral oval existence. It has been shown how this concept was subsequently justified in the publications by Y.I. Feldstein and O.B. Khorosheva. The issue of the priority of the auroral oval concept introduction into geophysics has been considered. The statement that the concept of the oval is an archaic paradigm of solar-terrestrial physics has been called into question. Some scientific fields in which the term auroral oval or simply oval was and is the paradigm have been listed.

  3. 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.

  4. 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...

  5. MITHRAS studies of the auroral oval and polar cap

    Science.gov (United States)

    Delabeaujardiere, Odile; Watermann, Juergen; Johnson, Robert M.

    1991-01-01

    MITHRAS is a program of coordinated experiments dedicated to studying the coupling between the magnetosphere, the ionosphere, and the thermosphere. MITHRAS observations mostly involve the Sondrestrom radar in Greenland, but other incoherent scatter radars around the world were also used. Contract highlights include the following items. (1) The most extensive comparisons ever made between incoherent scatter radar data and numerical simulation models were performed. These comparisons were based on both individual case studies and averaged data, and included observations from all the incoherent scatter radars. The comparisons showed general agreement between observations and model calculations but they also showed significant differences. (2) During solar maximum conditions, the contribution to the height integrated Pederson conductivity from solar produced F-region ionization can be as large as 60 pct. of the total. (3) Under certain geophysical conditions it appears possible to identify the low altitude cusp and distinguish it from the cleft. The cusp proper appears to be characterized by enhanced F region plasma density collocated with elevated F region electron temperature; it does not appear to be associated with a particular plasma flow pattern signature. (4) A new mechanism was proposed to explain how auroral surges might be formed. It was suggested that the surge was associated with a distortion of the poleward boundary of the aurora, and that this distortion was caused by the field aligned current.

  6. 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.

  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. 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.

  9. 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

  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. 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.

  12. 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

  13. 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

  14. 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

  15. 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...

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

    Science.gov (United States)

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

    2014-04-01

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

  17. 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

  18. MITHRAS studies of the auroral oval and polar cap. Final report, 1 May 87-31 Dec 90

    Energy Technology Data Exchange (ETDEWEB)

    De la Beaujardiere, O.; Watermann, J.; Johnson, R.M.

    1991-01-01

    MITHRAS is a program of coordinated experiments dedicated to studying the coupling between the magnetosphere, the ionosphere, and the thermosphere. MITHRAS observations mostly involve the Sondrestrom radar in Greenland, but other incoherent scatter radars around the world were also used. Contract highlights include: (1) The most extensive comparisons ever made between incoherent scatter radar data and numerical simulation models were performed. These comparisons were based on both individual case studies and averaged data, and included observations from all the incoherent scatter radars. The comparisons showed general agreement between observations and model calculations but they also showed significant differences. (2) During solar-maximum conditions, the contribution to the height integrated Pederson conductivity from solar-produced F-region ionization can be as large as 60% of the total. (3) Under certain geophysical conditions it appears possible to identify the low-altitude cusp and distinguish it from the cleft. The cusp proper appears to be characterized by enhanced F region plasma density collocated with elevated F region electron temperature; it does not appear to be associated with a particular plasma flow pattern signature. (4) A new mechanism was proposed to explain how auroral surges might be formed. It was suggested that the surge was associated with a distortion of the poleward boundary of the aurora, and that this distortion was caused by the field aligned currents within the head of the surge.

  19. 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.

  20. 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.

  1. 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.

  2. Equatorial magnetospheric particles and auroral precipitations

    Science.gov (United States)

    McIlwain, C. E.

    The injection boundary beyond which fresh hot plasma appears each magnetospheric substorm is generalized and extended to circle the Earth. The concept of an auroral shell representing the inner limit of active auroral processes is introduced. It is proposed that at low altitudes, this shell marks the equatorward edge of the auroral ovals, and that at high altitudes, it marks the injection boundary. The auroral ring is defined as the intersection of the auroral shell with the magnetic equator. A simple equation for computing the expected location of the auroral ring as a function of local time and magnetic disturbance level is obtained. Tests indicate that the model is valid and reasonably accurate.

  3. 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.

  4. Investigations of the auroral luminosity distribution and the dynamics of discrete auroral forms in a historical retrospective

    Science.gov (United States)

    Feldstein, Y. I.; Vorobjev, V. G.; Zverev, V. L.; Förster, M.

    2014-05-01

    Research results about planetary-scale auroral distributions are presented in a historical retrospective, beginning with the first "maps of isochasms" - lines of equal visibility of auroras in the firmament (Fig. 2) - up to "isoaurora maps" - lines of equal occurrence frequency of auroras in the zenith (Fig. 4). The exploration of auroras in Russia from Lomonosov in the 18th century (Fig. 1) until the start of the International Geophysical Year (IGY) in 1957 is shortly summed up. A generalised pattern of discrete auroral forms along the auroral oval during geomagnetically very quiet intervals is presented in Fig. 5. The changes of discrete auroral forms versus local time exhibit a fixed pattern with respect to the sun. The auroral forms comprise rays near noon, homogeneous arcs during the evening, and rayed arcs and bands during the night and in the morning. This fixed auroral pattern is unsettled during disturbances, which occur sometimes even during very quiet intervals. The azimuths of extended auroral forms vary with local time. Such variations in the orientation of extended forms above stations in the auroral zone have been used by various investigators to determine the position of the auroral oval (Fig. 9). Auroral luminosity of the daytime and nighttime sectors differ owing to different luminosity forms, directions of motion of the discrete forms, the height of the luminescent layers, and the spectral composition (predominant red emissions during daytime and green emissions during the night). Schemes that summarise principal peculiarities of daytime luminosity, its structure in MLT (magnetic local time) and MLat (magnetic latitude) coordinates, and the spectral composition of the luminosity are presented in Figs. 15 and 19. We discuss in detail the daytime sector dynamics of individual discrete forms for both quiet conditions and auroral substorms. The most important auroral changes during substorms occur in the nighttime sector. We present the evolution of

  5. Global response of the upper thermospheric winds to large ion drifts in the Jovian ovals

    Science.gov (United States)

    Majeed, T.; Bougher, S. W.; Ridley, A. J.; Waite, J. H.; Gladstone, G. R.; Bell, J. M.

    2016-05-01

    We use our fully coupled 3-D Jupiter Thermosphere General Circulation Model (JTGCM) to quantify processes which are responsible for generating neutral winds in Jupiter's oval thermosphere from 20 µbar to 10-4 nbar self-consistently with the thermal structure and composition. The heat sources in the JTGCM that drive the global circulation of neutral flow are substantial Joule heating produced in the Jovian ovals by imposing high-speed anticorotational ion drifts (~3.5 km s-1) and charged particle heating from auroral processes responsible for bright oval emissions. We find that the zonal flow of neutral winds in the auroral ovals of both hemispheres is primarily driven by competition between accelerations resulting from Coriolis forcing and ion drag processes near the ionospheric peak. However, above the ionospheric peak (<0.01 µbar), the acceleration of neutral flow due to pressure gradients is found to be the most effective parameter impacting zonal winds, competing mainly with acceleration due to advection with minor contributions from curvature and Coriolis forces in the southern oval, while in the northern oval it competes alone with considerable Coriolis forcing. The meridional flow of neutral winds in both ovals in the JTGCM is determined by competition between meridional accelerations due to Coriolis forcing and pressure gradients. We find that meridional flow in the lower thermosphere, near the peak of the auroral ionosphere, is poleward, with peak wind speeds of ~0.6 km s-1 and ~0.1 km s-1 in the southern and northern oval, respectively. The corresponding subsiding flow of neutral motion is ~5 m s-1 in the southern oval, while this flow is rising in the northern oval with reduced speed of ~2 m s-1. We also find that the strength of meridional flow in both auroral ovals is gradually weakened and turned equatorward near 0.08 µbar with wind speeds up to ~250 m s-1 (southern oval) and ~75 m s-1 (northern oval). The corresponding neutral motion in this

  6. Investigating the auroral electrojets using Swarm

    Science.gov (United States)

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

    2016-04-01

    The auroral electrojets are large horizontal currents that flow within the ionosphere in ovals around the polar regions. They are an important aspect of space weather and their position and intensity vary with solar wind conditions and geomagnetic activity. The electrojet positions are also governed by the Earth's main magnetic field. During more active periods, the auroral electrojets typically move equatorward and become more intense. This causes a range of effects on Earth and in space, including geomagnetically induced currents in power transmission networks, disturbance to radio communications and increased drag on satellites due to expansion of the atmosphere. They are also indicative of where the aurora are visible. Monitoring of the auroral electrojets in the pre-satellite era was limited to the network of ground-based magnetic observatories, from which the traditional AE activity indices are produced. These suffer in particular from the stations' poor distribution in position and so this motivates the use of satellite-based measurements. With polar low-Earth orbit satellites carrying magnetometers, all latitudes can be sampled with excellent resolution. This poster presents an investigation using Swarm's magnetometer data to detect the electrojets as the spacecraft move above them. We compare and contrast two approaches, one which uses vector data and the other which uses scalar data (Hamilton and Macmillan 2013, Vennerstrom and Moretto, 2013). Using ideas from both approaches we determine the oval positions and intensities from Swarm and earlier satellites. The variation in latitude and intensity with solar wind conditions, geomagnetic activity and secular variation of the main field is investigated. We aim to elucidate the relative importance of these factors. Hamilton, B. and Macmillan, S., 2013. Investigation of decadal scale changes in the auroral oval positions using Magsat and CHAMP data. Poster at IAGA 12th Scientific Assembly, 2013. http

  7. 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/ ...

  8. Influence of auroral streamers on rapid evolution of SAPS flows

    Science.gov (United States)

    Gallardo-Lacourt, B.; Nishimura, T.; Lyons, L. R.; Ruohoniemi, J. M.; Donovan, E.; Angelopoulos, V.; Nishitani, N.

    2015-12-01

    An important manifestation of plasma transport in the ionosphere is Subauroral Polarization Streams or SAPS, which are strong westward flow lying just equatorward of the electron auroral oval and thus of enhanced ionospheric conductivities of the auroral oval. While SAPS are known to intensify due to substorm injections, recent studies showed that large variability of SAPS flow can occur well after substorm onset and even during non-substorm times. These SAPS enhancements have been suggested to occur in association with auroral streamers that propagate equatorward, a suggestion that would indicate that plasma sheet fast flows propagate into the inner magnetosphere and increase subauroral flows. We present auroral images from the THEMIS ground-based all-sky-imager array and 2-d line-of-sight flow observations from the SuperDARN radars that share fields of view with the imagers to investigate systematically the association between SAPS and auroral streamers. We surveyed events from December 2007 to April 2013 for which high or mid-latitude SuperDARN radars were available to measure the SAPS flows, and identified 60 events. For streamers observed near the equatorward boundary of the auroral oval, we find westward flow enhancements of ~200 m/s slightly equatorward of the streamers. A preliminary survey suggests that >90% of the streamers that reach close to the equatorward boundary lead to westward flow enhancements. We also characterize the SAPS flow channel width and timing relative to streamers reaching radar echo meridians. The strong influence of auroral streamers on rapid SAPS flow evolution suggests that transient fast earthward plasma sheet flows can lead to westward SAPS flow enhancements in the subauroral region, and that such enhancements are far more common than only during substorms because of the frequent occurrences of streamers under various geomagnetic conditions.

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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...

  14. Global Response of the Upper Thermosphere to Large Ion Drifts in the Jovian Ovals

    Science.gov (United States)

    Majeed, T.; Bougher, S. W.; Ridley, A. J.; Gladstone, R.; Waite, J. H., Jr.; Bell, J. M.

    2015-12-01

    We use our fully coupled 3-D Jupiter Thermosphere General Circulation Model (JTGCM) to quantify wind processes that are responsible for generating neutral winds in the auroral thermosphere from 20 μbar to 10-4 nbar self-consistently with the thermal structure and compositions. The heat sources in the JTGCM that drive the global circulation of neutral flow are charge particle heating from particle impact of extreme auroral conditions and large amount of Joule heating produced in the Jovian ovals by imposing high speed anticorotational ion drifts up to ~3.5 kms-1. These sources are strongly related to the current system in the equatorial plasma sheet that allows plasma to flow outward from the ionosphere to the magnetosphere in the inner part and return from the magnetosphere to the ionosphere in the outer part. We find that strong pressure gradients are developed in the auroral regions, affecting zonal and meridional winds in addition to local temperature distributions. We also find that the zonal flow of neutral winds in the ovals of both hemispheres is primarily driven by competition between Coriolis forcing and ion drag processes near the ionospheric peak. However, above the ionospheric peak, the acceleration of neutral flow due to pressure gradients is found to be the most effective parameter impacting zonal winds. One of the most important findings of this investigation is that the meridional flow of neutral winds in the Jovian ovals is poleward near the peak of the auroral ionosphere. The strength of this flow is gradually weakened and turned equatorward at the sub-nanobar levels with wind speeds up to ~250 ms-1 in the southern oval and ~75 ms-1 in the northern oval. The corresponding neutral motion in this region is upward with wind speeds up to 4 ms-1 in both ovals. We will discuss the model assumptions, numerical framework and several parameterizations of inputs quantities. Comparisons of key model outputs (e.g. neutral temperatures and wind components

  15. 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...... of the satellite orbit and how it varies with local time and season in both hemispheres. Statistically, the strongest currents are observed in the predawn and predusk local time quadrants at latitudes that depend on the general magnetic activity level. We also show how the satellite-derived parameters relate......, this does not significantly affect the utility of the method for space weather applications even for satellites at substantially higher altitudes. The results for several individual magnetic storm periods demonstrate that large variability can exist in both the latitude and intensity of the currents during...

  16. 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

  17. Auroral kilometric radiation source characteristics using ray tracing techniques

    Science.gov (United States)

    Schreiber, R.; Santolik, O.; Parrot, M.; Lefeuvre, F.; Hanasz, J.; Brittnacher, M.; Parks, G.

    2002-11-01

    3-D ray tracing to the presumed auroral kilometric radiation (AKR) source region has been performed using the input data from wave distribution function (WDF) based on the AKR waveforms recorded on board the Interball 2 satellite by the French wave experiment MEMO. Both the direction of the WDF maximum and the WDF form and angular size have been taken into account. Two instances of AKR emissions were observed on 28 January 1997 at 2037 and 2107 UT. Rays traced in R-X mode out of the s/c point toward two different active regions on the auroral oval (as seen with Polar UV imager after projection of the source region along the magnetic field lines down to the ionosphere level). Source region apparent angular sizes based on WDF are compatible with sizes estimated from signal modulation produced by electric antenna system rotation.

  18. Effects of solar wind density on auroral electrojets and brightness under influence of substorms

    Directory of Open Access Journals (Sweden)

    J.-H. Shue

    2009-01-01

    Full Text Available Using the auroral electrojet indices and Polar Ultraviolet Imager auroral images, we examined two fortuitous events during which the solar wind density had clear enhancements while the other solar wind parameters were relatively constant. Two electrojet enhancements were found in each event. The first electrojet enhancement was likely to be related to a substorm in which an auroral bulge appeared at premidnight. The second electrojet enhancement was driven by the density enhancement in the solar wind. The auroral oval became wider in latitude and the auroral distribution became dispersed after the density enhancement arrived at the Earth. The total auroral power integrated over the entire nightside region from 50 to 80° MLAT, however, did not increase significantly in response to the density enhancement. Our interpretation is that the substorm that occurred prior to the solar wind density enhancement had drained out a significant portion of the stored energy in the magnetotail; therefore, less precipitation energy was deposited into the auroral ionosphere by the density enhancement.

  19. 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.

  20. 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

  1. 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...

  2. 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

  3. 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 technology indicate close communication between workshops in Ribe and Birka, yet craftspeople cultivated styles which were specific to the particular town. However, the distribution of the products is not confined to specific regions. The persistence of the stylistic choices is suggested to be a marker...

  4. 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°.

  5. 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

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

    Science.gov (United States)

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

    2005-10-01

    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 recovery phase of a strong substorm. A system of auroral arcs associated with convergent electric field structures, with a maximum perpendicular potential drop of about ~10 kV, and upflowing field-aligned currents with densities of 3 µA/m2 (mapped to the ionosphere), was detected at the boundary between the Plasma Sheet Boundary Layer (PSBL) and the Plasma Sheet (PS). The auroral arc structures evolve in shape and in magnitude on a timescale of tens of minutes, merging, broadening and intensifying, until finally fading away after about 50 min. Throughout this time, both the PS region and the auroral arc structure in its poleward part remain relatively fixed in space, reflecting the rather quiet auroral conditions during the end of the substorm. The auroral upward acceleration region is shown for this event to extend beyond 3.9 Earth radii altitude. Event 2 occurs during a more active period associated with the expansion phase of a moderate substorm. Images from the Defense Meteorological Satellite Program (DMSP) F13 spacecraft show that the Cluster spacecraft crossed the horn region of a surge-type aurora. Conjugated with the Cluster spacecraft crossing above the surge horn, the South Pole All Sky Imager recorded the motion and the temporal evolution of an east-west aligned auroral arc, 30 to 50 km wide. Intense electric field variations are measured by the Cluster spacecraft when crossing above the auroral arc structure, collocated with the density gradient at the PS poleward boundary, and coupled to intense upflowing field-aligned currents with

  7. 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%.

  8. 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.

  9. The auroral and ionospheric flow signatures of dual lobe reconnection

    Directory of Open Access Journals (Sweden)

    S. M. Imber

    2006-11-01

    Full Text Available We present the first substantial evidence for the occurrence of dual lobe reconnection from ionospheric flows and auroral signatures. The process of dual lobe reconnection refers to an interplanetary magnetic field line reconnecting with lobe field lines in both the northern and southern hemispheres. Two bursts of sunward plasma flow across the noon portion of the open/closed field line boundary (OCB, indicating magnetic flux closure at the dayside, were observed in SuperDARN radar data during a period of strongly northward IMF. The OCB is identified from spacecraft, radar backscatter, and auroral observations. In order for dual lobe reconnection to take place, we estimate that the interplanetary magnetic field clock angle must be within ±10° of zero (North. The total flux crossing the OCB during each burst is small (1.8% and 0.6% of the flux contained within the polar cap for the two flows. A brightening of the noon portion of the northern auroral oval was observed as the clock angle passed through zero, and is thought to be due to enhanced precipitating particle fluxes due to the occurrence of reconnection at two locations along the field line. The number of solar wind protons captured by the flux closure process was estimated to be ~2.5×1030 (4 tonnes by mass, sufficient to populate the cold, dense plasma sheet observed following this interval.

  10. 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)

  11. 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

  12. The Wave-Like Auroral Structure around Auroral Expansion Onset

    Institute of Scientific and Technical Information of China (English)

    TANG Chao-Ling

    2011-01-01

    We present the direct connection between the wave-like auroral structure around the time of auroral expansion onset and the ballooning mode waves in the near-Earth magnetotail. Based on the NASA mission time history of events and macroscale interactions during substorms (THEMIS) ground-based all-sky imagers, we show that around the time of auroral expansion onset, a wave-like auroral structure first has four luminosity peaks separated by 2-3° magnetic longitude (MLON). Subsequently, the wave-like structure propagates in the azimuthal direction and an overall bright arc spans approximately 1 h magnetic local time. The wavelength is estimated to be 120-180 km. Finally, a noticeable poleward auroral expansion is observed. The ballooning mode waves are identified by two THEMIS probes in the near-Earth magnetotail. The observed wavelength of the ballooning mode waves is approximately equal to the order of the ion Larmor radius. The wavelength of 1500 3000 km in the near-Earth magnetotail is comparable with the wave-like auroral structure estimate. This study suggests that the ballooning mode waves might play a crucial role in auroral expansion onset, corresponding to the wave-like auroral structure in this study.%We present the direct connection between the wave-like auroral structure around the time of auroral expansion onset and the ballooning mode waves in the near-Earth magnetotail.Based on the NASA mission time history of events and macroscale interactions during substorms (THEMIS) ground-based all-sky imagers,we show that around the tirne of auroral expansion onset,a wave-like auroral structure first has four luminosity peaks separated by 2-3° magnetic longitude (MLON).Subsequently,the wave-like structure propagates in the azimuthal direction and an overall bright arc spans approximately 1 h magnetic local time.The wavelength is estimated to be 120-180 km.Finally,a noticeable poleward auroral expansion is observed.The ballooning mode waves are identified by two

  13. 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.

  14. 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...

  15. 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.

  16. Thermospheric vertical winds in the auroral oval/polar cap region

    OpenAIRE

    Greet, P. A.; Innis, J. L.; P. L. Dyson

    2002-01-01

    Thermospheric mean vertical winds from high-resolution Fabry-Perot Spectrometer observations of the l630 nm emission (from ~ 240 km altitude), over a four year interval 1997–2000, from Mawson (67.6° S, 62.9° E, Inv 70.5° S) and Davis (68.6° S, 78.0° E, Inv 74.6° S) are presented. Combining the four years of data shows Mawson mean hourly vertical winds vary between -10 ms-1 and +4 ms-1, while D...

  17. Characteristics of Extreme Auroral Charging Events

    Science.gov (United States)

    Minow, Joseph I.; Willis, Emily; Parker, Linda Neergaard

    2014-01-01

    Today’s presentation describes preliminary results from a study of extreme auroral charging in low Earth orbit. Goal of study is to document characteristics of auroral charging events of importance to spacecraft design, operations, and anomaly investigations.

  18. 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.

  19. 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.

  20. 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

  1. Diagnosis of an imported Plasmodium ovale wallikeri infection in Malaysia.

    Science.gov (United States)

    Liew, Jonathan Wee Kent; Mahmud, Rohela; Tan, Lian Huat; Lau, Yee Ling

    2016-01-06

    Plasmodium ovale is rare and not exactly known to be autochthonous in Malaysia. There are two distinct forms of the parasite, namely P. ovale curtisi (classic form) and P. ovale wallikeri (variant form). Here, the first sequence confirmed case of an imported P. ovale wallikeri infection in Malaysia is presented. Microscopy found Plasmodium parasites with morphology similar to P. ovale or Plasmodium vivax in the blood films. Further confirmation using polymerase chain reaction (PCR) targeting the small-subunit rRNA gene of the parasite was unsuccessful. Genus-specific PCR was then performed and the product was sequenced and analysed. Sequence analyses confirmed the aetiological agent as P. ovale wallikeri. New species-specific primers (rOVA1v and rOVA2v) were employed and P. ovale wallikeri was finally confirmed. The findings highlight the need to look out for imported malaria infections in Malaysia and the importance of a constantly updated and validated diagnostic technique.

  2. 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

  3. 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...

  4. The Evolving Flow of Jupiter's White Ovals and Adjacent Cyclones

    CERN Document Server

    Choi, David S; Vasavada, Ashwin R; 10.1016/j.icarus.2009.10.013

    2013-01-01

    We present results regarding the dynamical meteorology of Jupiter's White Ovals at different points in their evolution. Starting from the era with three White Ovals FA, BC, and DE (Galileo), continuing to the post-merger epoch with only one Oval BA (Cassini), and finally to Oval BA's current reddened state (New Horizons), we demonstrate that the dynamics of their flow have similarly evolved along with their appearance. The northern periphery of Oval BA increased in speed by 20 m/s from Cassini to New Horizons, ending up at a speed nearly identical to that of the northern periphery of Oval DE during Galileo. However, the peak speeds along the southern rim of the newly formed Oval BA were consistently faster than the corresponding speeds in Oval DE, and they increased still further between Cassini and New Horizons, ending up at ~140 to 150 m/s. The modest strengthening of the winds in Oval BA, the appearance of red aerosols, and the appearance of a turbulent, cyclonic feature to Oval BA's northwest create a str...

  5. 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.

  6. 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 ...

  7. 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

  8. 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...

  9. 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.

  10. 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.

  11. 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....

  12. 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.

  13. 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)

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

    DEFF Research Database (Denmark)

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    2000-01-01

    instrument (LAPI) carried on DE 2 and the monoenergetic conductance model by Reiff [1984]. This method is shown to effectively minimize undesirable smearing of parameters in statistical substorm studies. Large spatial gradients in the conductance profiles are common in high-latitude part of the premidnight...... substorm region. The conductances maximizes in the high-latitude part of the surge with average Hall and Pedersen conductances of 38 and 18 mho respectively. During six different DE 2 passes we found Hall conductance peaks exceeding 100 mho in the high-latitude part of the surge or surge hem. These peaks...... 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 or more...

  15. 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.

  16. 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.

  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. 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.

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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...

  4. 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...

  5. 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.

  6. 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 (

  7. 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

  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 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.

  10. Function of oval cells in hepatocellular carcinoma in rats

    Institute of Scientific and Technical Information of China (English)

    Chi-Hua Fang; Jia-Qing Gong; Wei Zhang

    2004-01-01

    AIM: To study oval cells' pathological characteristics and relationship with the occurrence of hepatocellular carcinoma (HCC); to observe the form and structural characteristics of oval cells; to explore the expression characteristics of C-kit, PCNA mRNA and c-myc gene during the occurrence and development of HCC and the effect of ulinastatin (UTI) on C-kit and PCNA expression.METHODS: One hundred and twenty-five SD rats fed on 3,3'-diaminobenzidine (DAB) to construct HCC models were divided into control group, cancer-inducing group and UTI intervention group. In each group, rat liver samples were collected at weeks 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 and 24 respectively to study pathological distribution characteristics of oval cells in the process of carcinogenesis under optical microscope. Oval cells were separated by the methods of improved density gradient centrifugation and their structural characteristics were observed under optical microscope and electronic microscope respectively; the oval cells expressing C-kit and PCNA in the collected samples were observed by the methods of immunohistochemistry and image analysis and the expression of c-myc mRNA was also detected by reverse transcription polymerase chain reaction (RT-PCR).RESULTS: Oval cells proliferated firstly in the portal area then gradually migrated into hepatic parenchyma in the inducing group and intervention group. The oval cells distributed inside and outside the carcinoma nodes. The oval cells presented the characteristics of undifferentiated cells: a high ratio of nucleolus and cellular plasm and obvious nucleoli, rare organelle in plasm. Only a few mitochondria and endoplasmic reticulum and some villuslike apophysis on surface of cells could be seen. Cells stained with C-kit and PCNA antibody were mainly oval cells distributed in the portal area. The expression of cmyc mRNA increased with the progression of HCC.However, in the intervention group, UTI could retard its i n c rea se

  11. PFISR nightside observations of naturally enhanced ion acoustic lines, and their relation to boundary auroral features

    Directory of Open Access Journals (Sweden)

    R. G. Michell

    2008-11-01

    Full Text Available We present results from a coordinated camera and radar study of the auroral ionosphere conducted during March of 2006 from Poker Flat, Alaska. The campaign was conducted to coincide with engineering tests of the first quarter installation of the Poker Flat Incoherent Scatter Radar (PFISR. On 31 March 2006, a moderately intense auroral arc, (~10 kR at 557.7 nm, was located in the local magnetic zenith at Poker Flat. During this event the radar observed 7 distinct periods of abnormally large backscattered power from the F-region. These were only observed in the field-aligned radar beam, and radar spectra from these seven times show naturally enhanced ion-acoustic lines (NEIALs, the first observed with PFISR. These times corresponded to (a when the polar cap boundary of the auroral oval passed through the magnetic zenith, and (b when small-scale filamentary dark structures were visible in the magnetic zenith. The presence of both (a and (b was necessary for their occurrence. Soft electron precipitation occurs near the magnetic zenith during these same times. The electron density in the vicinity where NEIALs have been observed by previous studies is roughly between 5 and 30×1010 m−3. Broad-band extremely low frequency (BBELF wave activity is observed in situ by satellites and sounding rockets to occur with similar morphology, during active auroral conditions, associated with the poleward edge of the aurora and soft electron precipitation. The observations presented here suggest further investigation of the idea that NEIALs and BBELF wave activity are differently-observed aspects of the same wave phenomenon. If a connection between NEIALs and BBELF can be established with more data, this could provide a link between in situ measurements of downward current regions (DCRs and dynamic aurora, and ground-based observations of dark auroral structures and NEIALs. Identification of in situ processes, namely wave activity, in ground

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  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. 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...

  20. Embolismo cerebral recurrente, foramen oval permeable e hipercoagulabilidad

    Directory of Open Access Journals (Sweden)

    Dr. Luis Gutiérrez Jaikel

    2007-05-01

    Full Text Available Se presenta el caso de una paciente con embolismo cerebral recurrente, formen oval permeable, hipercoagulabilidad y masa atrial derecha de aspecto semejante a mixoma atrial que durante el cierre quirúrgico, se documentó que correspondía a músculo atrial redundante.We present the case of a patient with recurrent brain embolism, patent foramen ovale and hypercoagulable state, with a myxoma like mass in the right atrium that during the surgical time, was demonstrated to be redundant atrial muscle.

  1. 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...

  2. 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.

  3. 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

  4. 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.

  5. Ground-based observations of Saturn's auroral ionosphere over three days: Trends in H3+ temperature, density and emission with Saturn local time and planetary period oscillation

    Science.gov (United States)

    O'Donoghue, James; Melin, Henrik; Stallard, Tom S.; Provan, G.; Moore, Luke; Badman, Sarah V.; Cowley, Stan W. H.; Baines, Kevin H.; Miller, Steve; Blake, James S. D.

    2016-01-01

    On 19-21 April 2013, the ground-based 10-m W.M. Keck II telescope was used to simultaneously measure H3+ emissions from four regions of Saturn's auroral ionosphere: (1) the northern noon region of the main auroral oval; (2) the northern midnight main oval; (3) the northern polar cap and (4) the southern noon main oval. The H3+ emission from these regions was captured in the form of high resolution spectral images as the planet rotated. The results herein contain twenty-three H3+ temperatures, column densities and total emissions located in the aforementioned regions - ninety-two data points in total, spread over timescales of both hours and days. Thermospheric temperatures in the spring-time northern main oval are found to be cooler than their autumn-time southern counterparts by tens of K, consistent with the hypothesis that the total thermospheric heating rate is inversely proportional to magnetic field strength. The main oval H3+ density and emission is lower at northern midnight than it is at noon, in agreement with a nearby peak in the electron influx in the post-dawn sector and a minimum flux at midnight. Finally, when arranging the northern main oval H3+ parameters as a function of the oscillation period seen in Saturn's magnetic field - the planetary period oscillation (PPO) phase - we see a large peak in H3+ density and emission at ∼115° northern phase, with a full-width at half-maximum (FWHM) of ∼44°. This seems to indicate that the influx of electrons associated with the PPO phase at 90° is responsible at least in part for the behavior of all H3+ parameters. A combination of the H3+ production and loss timescales and the ±10° uncertainty in the location of a given PPO phase are likely, at least in part, to be responsible for the observed peaks in H3+ density and emission occurring at a later time than the peak precipitation expected at 90° PPO phase.

  6. 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

  7. 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...

  8. 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

  9. 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.

  10. 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...

  11. 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...

  12. Tail reconnection region versus auroral activity inferred from conjugate ARTEMIS plasma sheet flow and auroral observations

    Science.gov (United States)

    Nishimura, Y.; Lyons, L. R.; Xing, X.; Angelopoulos, V.; Donovan, E. F.; Mende, S. B.; Bonnell, J. W.; Auster, U.

    2013-09-01

    sheet flow bursts have been suggested to correspond to different types of auroral activity, such as poleward boundary intensifications (PBIs), ensuing auroral streamers, and substorms. The flow-aurora association leads to the important question of identifying the magnetotail source region for the flow bursts and how this region depends on magnetic activity. The present study uses the ARTEMIS spacecraft coordinated with conjugate ground-based auroral imager observations to identify flow bursts beyond 45 RE downtail and corresponding auroral forms. We find that quiet-time flows are directed dominantly earthward with a one-to-one correspondence with PBIs. Flow bursts during the substorm recovery phase and during steady magnetospheric convection (SMC) periods are also directed earthward, and these flows are associated with a series of PBIs/streamers lasting for tens of minutes with similar durations to that of the series of earthward flows. Presubstorm onset flows are also earthward and associated with PBIs/streamers. The earthward flows during those magnetic conditions suggest that the flow bursts, which lead to PBIs and streamers, originate from further downtail of ARTEMIS, possibly from the distant-tail neutral line (DNL) or tailward-retreated near-Earth neutral line (NENL) rather than from the nominal NENL location in the midtail. We find that tailward flows are limited primarily to the substorm expansion phase. They continue throughout the period of auroral poleward expansion, indicating that the expansion-phase flows originate from the NENL and that NENL activity is closely related to the auroral expansion of the substorm expansion phase.

  13. 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.

  14. 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.

  15. 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

  16. Upstream drivers of poleward moving auroral forms by satellite-imager coordinated observations

    Science.gov (United States)

    Wang, B.; Nishimura, T.; Lyons, L. R.; Angelopoulos, V.; Frey, H. U.; Mende, S. B.

    2015-12-01

    Poleward moving auroral forms (PMAFs) are observed near the dayside poleward auroral oval boundary. PMAFs are thought to be an ionospheric signature of dayside reconnection and flux transfer events. PMAFs tend to occur when the IMF is southward. Although a limited number of PMAFs has been found in association with IMF southward turning, events without appreciable changes in IMF have also been reported. While those PMAFs could be triggered spontaneously, many of the past studies used solar wind measurements far away from the bow shock nose and may have used inaccurate time shift or missed small-scale structures in the solar wind. To examine how often PMAFs are triggered by upstream structures using solar wind measurements close to the bow shock nose, we use the AGO all sky imager in Antarctic and THEMIS B and C satellites in 2008, 2009 and 2011. We identified 24 conjunction events, where at least one of the THEMIS satellites is in the solar wind and the AGO imager is located within 3 MLT from the THEMIS MLT. We found that, in 14 out of 24 conjunction events, PMAFs occur soon after IMF southward turning, indicating that IMF southward turning could be the major triggering of PMAFs. Interestingly, among these 14 cases, there are 7 cases with different IMF structures between THEMIS B/C and OMNI, which obtained IMF information from WIND and ACE. And the larger correlation coefficients between PMAFs and IMFs observed by THMEIS B/C than OMNI present the advantages of THEMIS B/C. Among the 10 cases without correlating with IMF structures, PMAFs in two events are shown to have good correlation with reflected ions in the foreshock. Based on all the conjunction events we identified, IMF southward turning is the major trigger of PMAFs and reflected ions have minor effects. The rest of the cases could be spontaneous PMAFs, although foreshock activities, even if exists, may be missed due to the IMF orientation.

  17. 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.

  18. Effect of Energetic Electrons on Quiet Auroral Arc Formation

    Science.gov (United States)

    Hasegawa, Hiroki; Ohno, Nobuaki; Sato, Tetsuya

    2010-11-01

    The theory of feedback instability between the magnetosphere and ionosphere is believed as one of the candidate to explain the formation of quiet auroral arc. Then, some magneto-hydro- dynamics simulations showed the arc formation by this macroscopic instability, while the effect of auroral energetic electrons on the arc formation was neglected or given as a macroscopic parameter in these simulations. On the other hand, because of the recent development of particle simulations, auroral energetic electrons are thought to be produced by the super ion-acoustic double layer that should be created by microscopic instability. To make close investigation of auroral arc formation, it is necessary to consider the interaction with microscopic instability. In this paper, we numerically study the effect of energetic electrons on quiet auroral arc formation by means of the Macro-Micro Interlocked simulation.

  19. Auroral ion outflow: low altitude energization

    OpenAIRE

    Lynch, K.A.; Semeter, J. L.; Zettergren, M.; Kintner, P.; R. Arnoldy; Klatt, E.; J. LaBelle; Michell, R. G.; Macdonald, E. A.; Samara, M.

    2007-01-01

    International audience; The SIERRA nightside auroral sounding rocket made observations of the origins of ion upflow, at topside F-region altitudes (below 700 km), comparatively large topside plasma densities (above 20 000/cc), and low energies (10 eV). Upflowing ions with bulk velocities up to 2 km/s are seen in conjunction with the poleward edge of a nightside substorm arc. The upflow is limited within the poleward edge to a region (a) of northward convection, (b) where Alfvénic and Pedersen...

  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. 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

     

  2. 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...

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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....

  9. 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.

  10. 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.

  11. Astrid-2, an advanced microsatellite for auroral research

    Directory of Open Access Journals (Sweden)

    G. T. Marklund

    Full Text Available The successful launch of the Swedish microsatellite Astrid-2 in December 1998 began a new era of auroral research, with advanced microprobes of 30 kg or less used as research tools. Innovative technologies and low-mass solutions were used for the sensors and deployment systems to allow a fairly complete set of scientific instruments within the 10 kg allocated for the scientific payload. A newly developed wire boom deployment system proved to function excellently. During its seven month lifetime Astrid-2 collected more than 26 Gbytes of high-quality data of auroral electric and magnetic fields, and auroral particle and plasma characteristics from approximately 3000 orbits at an inclination of 83° and an altitude of about 1000 km. Scientific results cover a broad range of topics, from the physics of energization of auroral particles to how the magnetosphere responds to the energy input from the solar wind and global magnetic field modelling. The fulfilment of both the technological and the scientific mission objectives has opened entirely new possibilities to carry out low-budget multipoint measurements in near-Earth space.

    Key words. Ionosphere (auroral ionosphere; instruments and techniques – Magnetospheric physics (auroral phenomena

  12. 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.

  13. A rocket-borne investigation of auroral electrodynamics within the auroral-ionosphere

    Science.gov (United States)

    Kaeppler, Stephen Roland

    This dissertation focuses on data analyzed from the Auroral Current and Electrodynamics Structure (ACES) sounding rocket mission. ACES consisted of two payloads launched nearly simultaneously in 2009 into a dynamic multiple-arc aurora. The mission was designed to observe the three-dimensional current system of an auroral arc system. To constrain the spatial-temporal ambiguity, the payloads were flown along nearly conjugate magnetic field footpoints, at various altitudes with small temporal separation. The high altitude payload took in situ measurements of the plasma parameters above the current closure region to measure the input signature into the lower ionosphere. The low-altitude payload took similar observations within the current closure region, where perpendicular cross-field currents can flow. A detailed description of the experimental configuration is presented, including operational details of the fields and plasma instruments flown on both payloads. The methods used to process data from the electrostatic particle detectors and the fluxgate magnetometer on both payloads are presented. Data from the all-sky imager details the auroral configuration at the time of launch. In situ data are presented detailing observations of the electric fields, magnetic fields, and the electron differential energy flux, as the payloads crossed nearly conjugate magnetic field lines. Field-aligned currents were calculated from magnetometer observations on the high altitude payload. These data were combined with electron flux data to show that the high altitude payload traversed regions of upward and downward field-aligned current. The low altitude payload observed signatures in the residual magnetic field components consistent with perpendicular closure current. Ionospheric collisionality is investigated to determine if it is a significant mechanism to explain observed differences in the low energy electron flux between the high altitude and low altitude payload. As a result of

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. Transcatheter closure of patent foramen ovale using the internal jugular venous approach.

    Science.gov (United States)

    Węglarz, Przemysław; Konarska-Kuszewska, Ewa; Zębik, Tadeusz; Kuszewski, Piotr; Drzewiecka-Gerber, Agnieszka; Motyka, Marek; Ludyga, Tomasz; Bajor, Grzegorz

    2014-01-01

    Transcatheter closure of patent foramen ovale is routinely performed using the transfemoral approach, which is safe and technically easy. Our case represents the rare situation where the procedure needs to be performed using the right internal jugular venous approach. According to our best knowledge this is the first report of a patent foramen ovale closure procedure with access through the internal jugular with necessity to advance the guide wire and transseptal sheath into the left ventricle. Developing alternative techniques of transcatheter patent foramen ovale closure seems to be especially important in rare cases where transfemoral access is unavailable.

  2. Space Weather Monitoring for ISS Space Environments Engineering and Crew Auroral Observations

    Science.gov (United States)

    Minow, Joseph; Pettit, Donald R.; Hartman, William A.

    2012-01-01

    Today s presentation describes how real time space weather data is used by the International Space Station (ISS) space environments team to obtain data on auroral charging of the ISS vehicle and support ISS crew efforts to obtain auroral images from orbit. Topics covered include: Floating Potential Measurement Unit (FPMU), . Auroral charging of ISS, . Real ]time space weather monitoring resources, . Examples of ISS auroral charging captured from space weather events, . ISS crew observations of aurora.

  3. 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

  4. 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.

  5. 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.

  6. 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...

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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)

  12. The peak altitude of H3+ auroral emission: comparison with the ultraviolet

    Science.gov (United States)

    Blake, J.; Stallard, T.; Miller, S.; Melin, H.; O'Donoghue, J.; Baines, K.

    2013-09-01

    The altitude of Saturn's peak auroral emission has previously been measured for specific cases in both the ultraviolet (UV) and the infrared (IR). Gerard et al [2009] concludes that the night side H2 UV emission is within the range of 800 to 1300 km above the 1-bar pressure surface. However, using colour ratio spectroscopy, Gustin et al [2009] located the emission layer at or above 610 km. Measurements of the infrared auroral altitude was conducted by Stallard et al [2012] on H3+ emissions from nine VIMS Cassini images, resulting in a measurement of 1155 ± 25 km above the 1-bar pressure surface. Here we present data analysed in a manner similar to Stallard et al [2012] on the observations of H3+ emission in twenty images taken by the Visual Infrared Mapping Spectrometer (VIMS) aboard the spacecraft Cassini from the years 2006, 2008 and 2012. The bins covered were 3.39872, 3.51284, 3.64853, 4.18299 and 4.33280 μm. These observations were selected from a set of 15,000 as they contained a useful alignment of the aurorae on the limb and the body of the planet. The specific conditions that had to be met for each image were as follows; minimum integration time of 75 milliseconds per pixel, minimum number of pixels in the x and y direction of 32, the image must include the latitude range of 70 to 90 degrees for either hemisphere and the sub spacecraft angle must be between 0 and 20 degrees. This alignment allowed for the altitudinal profiles to be analysed in terms of the difference between the latitude of aurorae on the limb and on the body of Saturn; thus permitting an investigation into the effects of misalignment. In this instance, misalignment was defined as the difference between the latitude of the peak emission latitude on the planet and the latitude of the limb; assuming the aurorae to be approximately circular. A statistical study by Badman et al [2011] showed that centre of the oval is on average offset anti sunward of the pole by about 1.6 degrees. To

  13. 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.

  14. 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...

  15. Evolution of Jupiter's auroral-related stratospheric heating and chemistry

    Science.gov (United States)

    Sinclair, James; Orton, Glenn S.; Greathouse, Thomas K.; Fletcher, Leigh N.; Moses, Julianne I.; Hue, Vincent; Irwin, Patrick Gerard Joseph; Melin, Henrik; Giles, Rohini Sara

    2016-10-01

    Auroral processes on Jupiter are evident over a large range of wavelengths. Emission at X-ray, UV and near-infrared wavelengths highlights the precipitation of charged particles in Jupiter's ionosphere. Jupiter's auroral regions also exhibit enhanced mid-infrared emission of CH4 (7.8-μm), C2H2 (13-μm), C2H4 (10.5-μm) and C2H6 (12.2-μm), which indicates auroral processes modify the thermal structure and chemistry of the neutral stratosphere at pressures from 10 mbar to 10 μbar. In Sinclair et al., 2016a (submitted), 2016b (in preparation), we investigated these processes further by performing a retrieval analysis of Voyager-IRIS (Infrared Interferometer Spectrometer) observations measured in November 1979, Cassini-CIRS (Composite Infrared Spectrometer) observations measured in January 2001 and IRTF-TEXES (Texas Echelon Cross Echelle Spectrograph on NASA's Infrared Telescope Facility) spectra measured in December 2014. These datasets however captured Jupiter at significantly different epochs and thus the overall global evolution of atmospheric conditions as well as differences in spatial sampling, spectral resolution (and therefore vertical resolution in the atmosphere) have made inferences of the temporal evolution in auroral regions a challenge. However, in April 2016, we acquired IRTF-TEXES observations of Jupiter's high latitudes, using observing parameters very similar to those in December 2014. By performing a similar analysis of these observations and comparing results between December 2014 and April 2016, we can investigate the evolution of the thermal structure and chemistry in Jupiter's auroral regions over a 15 month timescale. The magnitude of temperature/composition changes and the altitudes at which they occur will provide insights into how auroral processes in the ionosphere propagate to the stratosphere. In particular, we can assess whether the evolution of stratospheric conditions in auroral regions is related to the decrease in solar activity

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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...

  1. Auroral substorm response to solar wind pressure shock

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Two cases of auroral substorms have been studied with the Polar UVI data, which were associated with solar wind pressure shock arriving at the Earth. The global aurora activities started bout 1-2 min after pressure shocks arrived at dayside magnetopause, then nightside auroras intensified rapidly 3-4 min later, with auroral substorm onset. The observations in synchronous orbit indicated that the compressing effects on magnetosphere were observed in their corresponding sites about 2 min after the pressure shocks impulse magnetopause. We propose that the uroral intensification and substorm onset possibly result from hydromagnetic wave produced by the pressure shock.The fast-mode wave propagates across the magnetotail lobes with higher local Alfven velocity, magnetotail was compressed rapidly and strong lobe field and cross-tail current were built in about 1-2 min, and furthermore the substorm was triggered due to an instability in current sheet.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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...

  8. 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.

  9. Saturation and energy-conversion efficiency of auroral kilometric radiation

    Science.gov (United States)

    Wu, C. S.; Tsai, S. T.; Xu, M. J.; Shen, J. W.

    1981-01-01

    A quasi-linear theory is used to study the saturation level of the auroral kilometric radiation. The investigation is based on the assumption that the emission is due to a cyclotron maser instability as suggested by Wu and Lee and Lee et al. The thermodynamic bound on the radiation energy is also estimated separately. The energy-conversion efficiency of the radiation process is discussed. The results are consistent with observations.

  10. 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...

  11. 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...

  12. Effects of Interplanetary Shock Inclinations on Nightside Auroral Power Intensity

    Science.gov (United States)

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

    2016-02-01

    We derive fast forward interplanetary (IP) shock speeds and impact angles to study the geoeffectiveness 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 Earth's 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 potential mechanisms will be discussed.

  13. 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.

  14. 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

  15. 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...

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. 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

  1. Persistent truncus arteriosus and patent foramen ovale in a Simmentaler x Braunvieh calf.

    Science.gov (United States)

    Schwarzwald, C; Gerspach, C; Glaus, T; Scharf, G; Jenni, R

    2003-03-15

    A Simmentaler x Braunvieh calf had been anorexic during its first 36 hours of life, had a loud heart murmur and was suspected to have pneumonia. In the light of the results of radiographic and echocardiographic examinations, right heart catheterisation and angiography, a diagnosis of persistent truncus arteriosus and patent foramen ovale was made. The diagnosis was confirmed on postmortem examination.

  2. 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

  3. Predictors of recurrent stroke after percutaneous closure of patent foramen ovale

    DEFF Research Database (Denmark)

    Rudolph, Volker; Augustin, Jahan; Hofmann, Thomas;

    2014-01-01

    AIMS: Closure of patent foramen ovale following presumed paradoxical embolic stroke remains controversial. The answer to the question as to whether cardiovascular risk factors (CVRF) impact on the recurrence of stroke in patients who have undergone PFO closure remains elusive so far. We aimed to ...

  4. 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.)

  5. 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)

  6. Comparison of medical treatments in cryptogenic stroke patients with patent foramen ovale: A randomized clinical trial

    Directory of Open Access Journals (Sweden)

    Abdolhamid Shariat

    2013-01-01

    Full Text Available Background: This randomized clinical trial compared rates of stroke or transient ischemic attack recurrence or death in patients with cryptogenic stroke and patent foramen ovale (PFO who received medical treatment with aspirin or warfarin. Materials and Methods : Forty-four Iranian patients with cryptogenic stroke and patent foramen ovale participated in this randomized, single-blind trial between July 2007 and June 2010. All patients underwent transesophageal echocardiography and contrast-transcranial Doppler sonography to confirm the presence of patent foramen ovale. The patients were randomly assigned to receive aspirin or warfarin and were followed for 18 months for the recurrence of ischemic events or death. The principal investigator was blind to the group assignment. This trial is registered under number IRCT138805192323N1. Results: Five (11.4% patients had a stroke, 2 (4.5% had a transient ischemic attack and 2 (4.5% died. There was no difference in the rate of ischemic events or death between the aspirin- and warfarin-treated groups (hazard ratio: 0.45; 95% CI: 0.1-1.8; P = 0.259. Conclusion: There was no difference in ischemic event recurrence, death rates or side-effects between patients with cryptogenic stroke and patent foramen ovale who were treated with aspirin vs. warfarin.

  7. 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.

  8. 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

  9. 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.

  10. Energy of auroral electrons and Z mode generation

    Science.gov (United States)

    Krauss-Varban, D.; Wong, H. K.

    1990-01-01

    The present consideration of Z-mode radiation generation, in light of observational results indicating that the O mode and second-harmonic X-mode emissions can prevail over the X-mode fundamental radiation when suprathermal electron energy is low, gives attention to whether the thermal effect on the Z-mode dispersion can be equally important, and whether the Z-mode can compete for the available free-energy source. It is found that, under suitable circumstances, the growth rate of the Z-mode can be substantial even for low suprathermal auroral electron energies. Growth is generally maximized for propagation perpendicular to the magnetic field.

  11. 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

  12. 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

  13. 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...

  14. 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.

  15. Giant aneurysm of the atrial septum associated with premature closure of foramen ovale

    Directory of Open Access Journals (Sweden)

    Romaguera Rita L

    2005-08-01

    Full Text Available Abstract Premature closure or restriction of foramen ovale (PCFO is a rare congenital anomaly that can lead to a wide spectrum of cardiac malformations. This spectrum of secondary malformations appears to depend on the gestational timing of closure of the foramen ovale and to the degree of restriction. Earlier in the gestation, closure of the foramen has been associated with severe hypoplasia of the left ventricle whereas later closure has been associated with right heart failure and rarely with the formation of an aneurysm of the atrial septum. We describe the case of a 1 day old infant in whom PCFO resulted in severe right heart failure in addition to the formation of a giant atrial septal aneurysm.

  16. Efficient heat-transfer surfaces assembled from partially finned flat-oval tubes

    Science.gov (United States)

    Pis'mennyi, E. N.

    2011-04-01

    The state of finned convective heat-transfer surfaces and prospects for using them in power engineering and industry are briefly reviewed. The characteristics of a heat-recovery economizer made of partially finned flat-oval tubes are presented by way of comparing them with design versions employing known types of finned tubes, and the results gained from its operation downstream of a PTVM-30M boiler are given.

  17. 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...

  18. 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 ...

  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. Infection of Amblyomma ovale by Rickettsia sp. strain Atlantic rainforest, Colombia.

    Science.gov (United States)

    Londoño, Andrés F; Díaz, Francisco J; Valbuena, Gustavo; Gazi, Michal; Labruna, Marcelo B; Hidalgo, Marylin; Mattar, Salim; Contreras, Verónica; Rodas, Juan D

    2014-10-01

    Our goal was to understand rickettsial spotted fevers' circulation in areas of previous outbreaks reported from 2006 to 2008 in Colombia. We herein present molecular identification and isolation of Rickettsia sp. Atlantic rainforest strain from Amblyomma ovale ticks, a strain shown to be pathogenic to humans. Infected ticks were found on dogs and a rodent in Antioquia and Córdoba Provinces. This is the first report of this rickettsia outside Brazil, which expands its known range considerably.

  1. Studies of the auroral ionosphere with the MITHRAS

    Science.gov (United States)

    Foster, J. C.

    1986-06-01

    The extensive MITHRAS radar data set was the object of extensive analyses of the processes and characteristics of the auroral latitude ionosphere and thermosphere: (1) High-Latitude Electrodynamics: Ionospheric response to substorms at widely separated local times was investigated. (2) Ionospheric Plasma Transport: The effects of plasma convection on the formation of the midlatitude trough were studied utilizing the wide spatial field of view of the Millstone radar. (3) Convection Snapshots: Simultaneous data from spaced instruments were combined to produce snapshots of the polar and auroral convection pattern. (4) Comparisons with Models. (5) Data Bases Studies and Empirical Models: The extensive data set which resulted from the MITHRAS experimental program was incorporated into a multi-instrument, common format data base. (6) Azimuth Scan Experiments: Analysis of the complex data during MITHRAS azimuth scanning experiments resulted in the capability of mapping the convection electric field within the extended field of the radar. (7) Thermosphere and Exosphere: The diurnal variation of exospheric temperature over 30 degrees of latitude around Millstone Hill has been investigated using MITHRAS elevation scan data.

  2. 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.

  3. 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.

  4. 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.

  5. ISOLATION OF HEPATIC OVAL CELLS FROM DIFFERENT MODEL RATS INCLUDING DIABETIC RATS

    Institute of Scientific and Technical Information of China (English)

    LU Ying-li; YE Ting-ting; XIA Fang-zhen; WANG Ning-jian; YANG Hua; CHEN Yi

    2009-01-01

    Objective To acquire oval cells (progenitor stem cells) from adult rat liver of different models including diabetic rats. Methods Thirty Sprague-Dawley (SD) rats were divided into 5 groups randomly: control, 2-acetylaminofluorene (2-AAF), 2-AAF+partial hepatectomy (PH), 2-AAF+carbon tetrachloride (CCl4), and diabetic groups. As two-step collagenase perfusion protocol of Seglen, oval cells were isolated by Percoll density gradient centrifugation. Thy1.1 positive cells were sorted by flow cytometry, and then cultured in Dulbeccos minimum Eagles medium (DMEM). Immunofluorescence staining was applied to labelling Thy1.1. Results Different rates of Thy1.1 positive oval cells were found in different rat model groups: 0.5% in 2-AAF, 0.3% in 2-hAAF+PH, 0.2% in 2-AAF+CCl4 , 0.1% in diabetic, and 0.0% in control. Isolated cells adhered to plate with fusiform or polygon as epithelial cells. Conclusion Progenitor stem cells exist in injured liver tissue including those from diabetic rats.

  6. 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.

  7. Inhibition of Notch signaling affects hepatic oval cell response in rat model of 2AAF-PH

    Directory of Open Access Journals (Sweden)

    Darwiche H

    2011-09-01

    Full Text Available Houda Darwiche, Seh-Hoon Oh, Nicole C Steiger-Luther, Jennifer M Williams, Dana G Pintilie, Thomas D Shupe, Bryon E PetersenDepartment of Pathology, Immunology, and Laboratory Medicine, Program in Stem Cell Biology and Regenerative Medicine, College of Medicine, University of Florida, Gainesville, FL, USABackground and aims: Activation of the oval cell compartment occurs in the liver when hepatocytes are functionally compromised and/or unable to divide. Our goal was to investigate the systemic signals responsible for determining the efficiency of oval cell-mediated liver regeneration, focusing on the Notch signaling cascade.Methods: The established oval cell induction protocol of 2-acetylaminofluorine (2-AAF implantation followed by 70% surgical resection of the liver (partial hepatectomy, PH was employed in a rat model. This oval cell induction model was further combined with injections of a γ-secretase inhibitor (GSI XX to examine the effects of Notch inhibition on oval cell-aided regeneration of the liver.Results: Notch signaling was found to be upregulated at the peak of oval cell induction during 2AAF-PH alone. Treatment with GSI XX led to interruption of the Notch signal, as shown by a decrease in expression of Hes1. While there was a robust oval cell response seen at day 11 post-PH, there was a measurable delay in differentiation when Notch was inhibited. This was confirmed morphologically as well as by immunohistochemistry for the oval cell markers, α-fetoprotein, OV-6, and CK19. The hepatocytes seen at day 22 demonstrated an enhanced hepatocellular mitoinhibition index (p21Waf1/Ki67, suggestive of dysregulated proliferation and cell cycle progression. Moreover, these hepatocytes exhibited decreased expression of hepatocyte functional markers, such as cytochrome P450 and glucose-6-phosphatase-α.Conclusion: Taken together, these results identify the Notch signaling pathway as a potent regulator of differentiation and proliferation in

  8. Simultaneous ground- and satellite-based observation of MF/HF auroral radio emissions

    Science.gov (United States)

    Sato, Yuka; Kumamoto, Atsushi; Katoh, Yuto; Shinbori, Atsuki; Kadokura, Akira; Ogawa, Yasunobu

    2016-05-01

    We report on the first simultaneous measurements of medium-high frequency (MF/HF) auroral radio emissions (above 1 MHz) by ground- and satellite-based instruments. Observational data were obtained by the ground-based passive receivers in Iceland and Svalbard, and by the Plasma Waves and Sounder experiment (PWS) mounted on the Akebono satellite. We observed two simultaneous appearance events, during which the frequencies of the auroral roar and MF bursts detected at ground level were different from those of the terrestrial hectometric radiation (THR) observed by the Akebono satellite passing over the ground-based stations. This frequency difference confirms that auroral roar and THR are generated at different altitudes across the F peak. We did not observe any simultaneous observations that indicated an identical generation region of auroral roar and THR. In most cases, MF/HF auroral radio emissions were observed only by the ground-based detector, or by the satellite-based detector, even when the satellite was passing directly over the ground-based stations. A higher detection rate was observed from space than from ground level. This can primarily be explained in terms of the idea that the Akebono satellite can detect THR emissions coming from a wider region, and because a considerable portion of auroral radio emissions generated in the bottomside F region are masked by ionospheric absorption and screening in the D/E regions associated with ionization which results from auroral electrons and solar UV radiation.

  9. 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.

  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. 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

  14. 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

  15. Whistler-Langmuir oscillitons and their relation to auroral hiss

    Directory of Open Access Journals (Sweden)

    K. Sauer

    2011-10-01

    Full Text Available A new type of oscilliton (soliton with superimposed spatial oscillations is described which arises in plasmas if the electron cyclotron frequency Ωe is larger than the electron plasma frequency ωe, which is a typical situation for auroral regions in planetary magnetospheres. Both high-frequency modes of concern, the Langmuir and the whistler wave, are completely decoupled if they propagate parallel to the magnetic field. However, for oblique propagation two mixed modes are created with longitudinal and transverse electric field components. The lower mode (in the literature commonly called the whistler mode, e.g. Gurnett et al., 1983 has whistler wave characteristics at small wave numbers and asymptotically transforms into the Langmuir mode. As a consequence of the coupling between these two modes, with different phase velocity dependence, a maximum in phase velocity appears at finite wave number. The occurrence of such a particular point where phase and group velocity coincide creates the condition for the existence of a new type of oscillating nonlinear stationary structure, which we call the whistler-Langmuir (WL oscilliton. After determining, by means of stationary dispersion theory, the parameter regime in which WL oscillitons exist, their spatial profiles are calculated within the framework of cold (non-relativistic fluid theory. Particle-in-cell (PIC simulations are used to demonstrate the formation of WL oscillitons which seem to play an important role in understanding electron beam-excited plasma radiation that is observed as auroral hiss in planetary magnetospheres far away from the source region.

  16. AKR breakup and auroral particle acceleration at substorm onset

    Science.gov (United States)

    Morioka, A.; Miyoshi, Y.; Tsuchiya, F.; Misawa, H.; Yumoto, K.; Parks, G. K.; Anderson, R. R.; Menietti, J. D.; Donovan, E. F.; Honary, F.; Spanswick, E.

    2008-09-01

    The dynamical behavior of auroral kilometric radiation (AKR) is investigated in connection with auroral particle acceleration at substorm onsets using high-time-resolution wave spectrograms provided by Polar/PWI electric field observations. AKR develops explosively at altitudes above a preexisting low-altitude AKR source at substorm onsets. This "AKR breakup" suggests an abrupt formation of a new field-aligned acceleration region above the preexisting acceleration region. The formation of the new acceleration region is completed in a very short time (amplitude increases 10,000 times in 30 seconds), suggesting that the explosive development is confined to a localized region. AKR breakups are usually preceded (1-3 minutes) by the appearance and/or gradual enhancement of the low-altitude AKR. This means that the explosive formation of the high-altitude electric field takes place in the course of the growing low-altitude acceleration. The development of the low-altitude acceleration region is thus a necessary condition for the ignition of the high-altitude bursty acceleration. The dH/dt component from a search-coil magnetometer at ground shows that a few minutes prior to substorm onsets, the quasi-DC component begins a negative excursion that is nearly synchronized with the start of the gradual enhancement of the low-altitude AKR, indicating a precursor-like behavior for the substorm. This negative variation of dH/dt suggests an exponentially increasing ionospheric current induced by the upward field-aligned current. At substorm onsets, the decrease in the quasi-DC variation of dH/dt further accelerates, indicating a sudden reinforcement of the field-aligned current.

  17. 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.

  18. 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)

  19. 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

  20. 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)

  1. 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

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

    Science.gov (United States)

    Willis, D. M.; Armstrong, G. M.; Ault, C. E.; Stephenson, F. R.

    2005-03-01

    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. European telescopic

  3. Plasma physics on auroral field lines - The formation of ion conic distributions

    Science.gov (United States)

    Ashour-Abdalla, M.; Okuda, H.

    1983-01-01

    The formation of the conical distribution function and the acceleration of ions on aurora field lines are considered. Ion cyclotron waves were assumed to be excited by drifting electrons associated with the return current in the auroral zone. A theoretical analysis of ion cyclotron waves is given, and a simulation model is described. Simulation results are presented. The heating of ions and the evolution of ion cyclotron waves on auroral field lines and in the magnetosphere are discussed.

  4. 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...

  5. [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

  6. 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

  7. 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

  8. 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.

  9. 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...

  10. 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...

  11. [Isolated Pulmonary Valve Endocarditis in a Patient with Aortic Regurgitation and Patent Foramen Ovale;Report of a Case].

    Science.gov (United States)

    Doi, Toshio; Gyoten, Takayuki; Sakata, Kimimasa; Nagura, Saori; Yamashita, Akio; Fukahara, Kazuaki; Kotoh, Keiju; Yoshimura, Naoki

    2016-07-01

    Isolated pulmonary valve endocarditis is an extremely rare clinical condition. Here, we report a case of pulmonary valve endocarditis caused by methicillin-resistant Staphylococcus aureus (MRSA). An 84-year-old man with a history of aortic regurgitation and patent foramen ovale was admitted to our hospital due to fever of unknown origin for 4 weeks' duration. MRSA was detected in his blood cultures. Transthoracic echocardiography demonstrated a mobile vegetation attached to the pulmonary valve, moderate to severe aortic regurgitation, and patent foramen ovale with left-to-right shunt. After 30-days' treatment with vancomycin, gentamicin and rifampicin, he defervesced and blood cultures became negative. At surgery, a large vegetation was still attached to the pulmonary valve, but the leaflets remained with minimum damage. Aortic valve replacement, direct closure of the patent foramen ovale, and simple resection of the vegetation were performed. The postoperative course was uneventful. PMID:27365067

  12. 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 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-1,4-dihydro......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...... 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....

  13. 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.

  14. Oval cell response is attenuated by depletion of liver resident macrophages in the 2-AAF/partial hepatectomy rat.

    Directory of Open Access Journals (Sweden)

    Shuai Xiang

    Full Text Available BACKGROUND/AIMS: Macrophages are known to play an important role in hepatocyte mediated liver regeneration by secreting inflammatory mediators. However, there is little information available on the role of resident macrophages in oval cell mediated liver regeneration. In the present study we aimed to investigate the role of macrophages in oval cell expansion induced by 2-acetylaminofluorene/partial hepatectomy (2-AAF/PH in rats. METHODOLOGY/PRINCIPAL FINDINGS: We depleted macrophages in the liver of 2-AAF/PH treated rats by injecting liposome encapsulated clodronate 48 hours before PH. Regeneration of remnant liver mass, as well as proliferation and differentiation of oval cells were measured. We found that macrophage-depleted rats suffered higher mortality and liver transaminase levels. We also showed that depletion of macrophages yielded a significant decrease of EPCAM and PCK positive oval cells in immunohistochemical stained liver sections 9 days after PH. Meanwhile, oval cell differentiation was also attenuated as a result of macrophage depletion, as large foci of small basophilic hepatocytes were observed by day 9 following hepatectomy in control rats whereas they were almost absent in macrophage depleted rats. Accordingly, real-time polymerase chain reaction analysis showed lower expression of albumin mRNA in macrophage depleted livers. Then we assessed whether macrophage depletion may affect hepatic production of stimulating cytokines for liver regeneration. We showed that macrophage-depletion significantly inhibited hepatic expression of tumor necrosis factor-α and interleukin-6, along with a lack of signal transducer and activator of transcription 3 phosphorylation during the early period following hepatectomy. CONCLUSIONS: These data indicate that macrophages play an important role in oval cell mediated liver regeneration in the 2-AAF/PH model.

  15. Reformed Solitary Kinetic Alfvén Waves due to Dissipations and Auroral Electron Acceleration

    Institute of Scientific and Technical Information of China (English)

    WU De-Jin; CHAO Jih-Kwin; LEE Luo-Chuan; FENG Xue-Shang

    2001-01-01

    The physical nature of the auroral electron acceleration has been an outstanding problem in space physics for decades.Some recent observations from the auroral orbit satellites,FREJA and FAST,showed that large amplitude solitary kinetic Alfvén waves (SKAWs) are a common electromagnetic active phenomenon in the auroral magnetosphere. In a Iow-ββ/2 (i.e.,β/2 < me/mi < 1) plasma,the drift velocity of electrons relative to ions within SKAWs is much larger than thermal velocities of both electrons and ions.This leads to instabilities and causes dissipations of SKAWs.In the present work,based on the analogy of classical particle motion in a potential well,it is shown that a shock-like structure can be formed from SKAWs if dissipation effects are included.The reformed SKAWs with a shock-like structure have a local density jump and a net field-aligned electric potential drop of order of mev2A/e over a characteristic width of several )e.As a consequence,the reformed SKAWs can efficiently accelerate electrons field-aligned to the order of the local Alfvén velocity.In particular,we argue that this electron acceleration mechanism by reformed SKAWs can play an important role in the auroral electron acceleration problem.The result shows that not only the location of acceleration regions predicted by this model is well consistent with the observed auroral electron acceleration region of I 2 RE above the auroral ionosphere,but also the accelerated electrons from this region can obtain an energy of several keV and carry a field-aligned current of several/A/m2 which are comparable to the observations of auroral electrons.

  16. 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

  17. Mouse hepatic oval cells require Met-dependent PI3K to impair TGF-β-induced oxidative stress and apoptosis.

    Directory of Open Access Journals (Sweden)

    Adoración Martínez-Palacián

    Full Text Available We have previously shown that oval cells harboring a genetically inactivated Met tyrosine kinase (Met(-/- oval cells are more sensitive to TGF-β-induced apoptosis than cells expressing a functional Met (Met(flx/flx, demonstrating that the HGF/Met axis plays a pivotal role in oval cell survival. Here, we have examined the mechanism behind this effect and have found that TGF-β induced a mitochondria-dependent apoptotic cell death in Met(flx/flx and Met(-/- oval cells, associated with a marked increase in levels of the BH3-only proteins Bim and Bmf. Bmf plays a key role during TGF-β-mediated apoptosis since knocking down of BMF significantly diminished the apoptotic response in Met(-/- oval cells. TGF-β also induced oxidative stress accompanied by NADPH oxidase 4 (Nox4 mRNA up-regulation and decreased protein levels of antioxidant enzymes. Antioxidants inhibit both TGF-β-induced caspase 3 activity and Bmf up-regulation, revealing an oxidative stress-dependent Bmf regulation by TGF-β. Notably, oxidative stress-related events were strongly amplified in Met(-/- oval cells, emphasizing the critical role of Met in promoting survival. Pharmacological inhibition of PI3K did impair HGF-driven protection from TGF-β-induced apoptosis and increased sensitivity of Met(flx/flx oval cells to TGF-ß by enhancing oxidative stress, reaching apoptotic indices similar to those obtained in Met(-/- oval cells. Interestingly, both PI3K inhibition and/or knockdown itself resulted in caspase-3 activation and loss of viability in Met(flx/flx oval cells, whereas no effect was observed in Met(-/- oval cells. Altogether, results presented here provide solid evidences that both paracrine and autocrine HGF/Met signaling requires PI3K to promote mouse hepatic oval cell survival against TGF-β-induced oxidative stress and apoptosis.

  18. Generation of Z mode radiation by diffuse auroral electron precipitation

    Science.gov (United States)

    Dusenbery, P. B.; Lyons, L. R.

    1985-01-01

    The generation of Z mode waves by diffuse auroral electron precipitation is investigated assuming that a loss cone exists in the upgoing portion of the distribution due to electron interactions with the atmosphere. The waves are generated at frequencies above, but very near, the local electron cyclotron frequency omega(e) and at wave normal angles larger than 90 deg. In agreement with Hewitt et al. (1983), the group velocity is directed downward in regions where the ratio of the upper hybrid frequency omega(pe) to Omega(e) is less than 0.5, so that Z mode waves excited above a satellite propagate toward it and away from the upper hybrid resonance. Z mode waves are excited in a frequency band between Omega(e) and about 1.02 Omega(e), and with maximum growth rates of about 0.001 Omega(e). The amplification length is about 100 km, which allows Z mode waves to grow to the intensities observed by high-altitude satellites.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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).

  4. 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...

  5. 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

  6. Precipitating Electron Population Inversion from Auroral Optical Data during the MICA Rocket Launch

    Science.gov (United States)

    Ahrns, J.; Hampton, D. L.; Stenbaek-Nielsen, H.; Michell, R. G.; Samara, M.; Powell, S.; Lynch, K. A.; Fernandes, P. A.; Lessard, M.

    2012-12-01

    The MICA (Magnetosphere-Ionosphere Coupling in the Alfvèn Resonator) sounding rocket was launched from Poker Flat, AK on Feb 19, 2012, into a series of discrete auroral arcs immediately following auroral breakup. We operated a set of ground-based optical imagers in support of the launch which captured the event, including more than an hour of auroral activity in the eventual rocket trajectory prior to launch at a variety of temporal (~1 second cadence to video frame rate) and spatial (all-sky to sub-kilometer) resolutions and in several spectral emission lines. Our imagers were located at Poker Flat, Fort Yukon, and Venetie AK (the last of which viewed the auroral conjugate of the rocket at magnetic zenith with sub-kilometer resolution) which allows a 3-dimensional reconstruction of certain auroral features from the optical data. We use this data, along with an electron transport model, to estimate the precipitating electron population and its effect on the background plasma to characterize the energy input prior to and during the rocket flight.

  7. Simultaneous ground-satellite observations of meso-scale auroral arc undulations

    Science.gov (United States)

    Motoba, T.; Hosokawa, K.; Ogawa, Y.; Sato, N.; Kadokura, A.; Milan, S. E.; Lester, M.

    2012-06-01

    We present simultaneous ground-based and in situ measurements of a train of meso-scale (about 100-300 km) auroral arc undulations, occurring in the postmidnight sector (˜1 MLT) between 0040 UT and 0054 UT on September 21, 2009. The undulations appeared at the auroral poleward boundary, and then moved eastward with a speed of 0.9-2.2 km s-1. Dynamic behaviors of the associated meso-scale ionospheric plasma flows and current systems were also detected with the ground-based magnetometer and radar measurements within the all-sky camera field-of-view. During the interval of interest, simultaneous Cluster observations in the central near tail region (11-14 RE down tail) were available, and especially the ionospheric footprint of Cluster 2 (CL2) was close to the optical auroral forms. CL2 observed strong fluctuations in the in situ magnetic field with amplitude of 5-10 nT whenever a bright arc area, and its trailing adjacent area, of the auroral undulations passed its ionospheric footprint. Such in situ magnetic field changes at CL2 could be considered as a manifestation of localized upward and downward field-aligned current sheets moving eastward at the central near-Earth tail boundary, linked to the meso-scale auroral undulation structures.

  8. 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.

  9. Migraine and patent foramen ovale: exploring the association and a possible treatment option.

    Science.gov (United States)

    Hasan, Muhammed Yaser

    2008-08-01

    Migraine is a very common type of headache. With a prevalence of 10-12%, migraine ranks 19th among diseases causing worldwide morbidity. Number of studies have shown a high prevalence of patent foramen ovale (PFO) in patients with migraine, especially migraine with aura. The right to left shunting of blood in a PFO could serve as a conduit for chemicals that would exert a trigger effect on hyper excitable neurons leading to the development of migraine. Furthermore patients with PFO and migraine also show a marked improvement in their symptoms after percutaneous closure of the PFO. This review is a close look at this association and also explores whether subsequent closure of the shunt can be looked upon as a viable treatment option.

  10. 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)

  11. 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.

  12. Patent foramen ovale in trigeminal autonomic cephalalgias and hemicrania continua: a non-specific pathophysiological occurrence?

    Science.gov (United States)

    Amaral, Vanise; Freitas, Gabriel R de; Rodrigues, Bruno C B; Christoph, Daniel de H; Pinho, Carlos A de; Góes, Cristiana de Faria P; Vincent, Maurice B

    2010-08-01

    Patent foramen ovale (PFO), a relatively common abnormality in adults, has been associated with migraine. Few studies also linked PFO with cluster headache (CH). To verify whether right-to-left shunt (RLS) is related to headaches other than migraine and CH, we used transcranial Doppler following microbubbles injection to detect shunts in 24 CH, 7 paroxysmal hemicrania (PH), one SUNCT, two hemicrania continua (HC) patients; and 34 matched controls. RLS was significantly more frequent in CH than in controls (54% vs. 25%, p=0.03), particularly above the age of 50. In the HC+PH+SUNCT group, RLS was found in 6 patients and in 2 controls (p=0.08). Smoking as well as the Epworth Sleepiness Scale correlated significantly with CH, smoking being more frequent in patients with RLS. PFO may be non-specifically related to trigeminal autonomic cephalalgias and HC. The headache phenotype in PFO patients probably depends on individual susceptibility to circulating trigger factors.

  13. 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

  14. Physiological Responses during Cycling With Oval Chainrings (Q-Ring and Circular Chainrings

    Directory of Open Access Journals (Sweden)

    Alfredo Cordova

    2014-06-01

    Full Text Available The aim of this study was to compare the physiological responses of cyclists using round (C-ring or oval (Q-ring chainrings during an incremental test until exhaustion. Following a randomized design, fourteen male elite cyclists [age (mean ± SD: 21.1 ± 2.1 yr; VO2max: 78.5 ± 5.3 mL·kg-1min-1] performed two incremental maximal tests separated by 48 h (one with C-rings, the other with Q-rings. Starting at 100 W, the workload was increased by 25 W every 3 min until volitional exhaustion. Maximal heart rate, power output and oxygen consumption were compared. Blood lactate was monitored throughout the test. After the incremental test, 4 intermittent 20-s maximal sprints with a 60-s recovery period in between were performed. Maximal isometric voluntary contractions were performed at rest and immediately after each 20-s maximal sprint, and the force and EMG RMS amplitude were recorded from the vastus medialis and vastus lateralis muscles. For the incremental exercise test, no significant differences were found in the maximal power output (P=0.12, oxygen consumption (P=0.39, and heart rate (P=0.32 between Q-rings and C-rings. Throughout the incremental test, lactate levels were comparable when using both the C-rings and Q-rings (P=0.47. During the short sprints, power output was 2.5–6.5% greater for Q-rings than for C-rings (P=0.22. The decline in EMG RMS amplitude observed during the incremental tests was comparable for Q-rings and C-rings (0.42. These findings indicate that the oval chainring design, presented here as “Q-rings”, did not significantly influence the physiological response to an incremental exercise test as compared to a conventional chainring.

  15. 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.

  16. 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.

  17. EGFR is dispensable for c-Met-mediated proliferation and survival activities in mouse adult liver oval cells.

    Science.gov (United States)

    Martínez-Palacián, A; del Castillo, G; Herrera, B; Fernández, M; Roncero, C; Fabregat, I; Sánchez, A

    2012-02-01

    Liver progenitor cells rise as potential critical players in hepatic regeneration but also carcinogenesis. It is therefore mandatory to define the signals controlling their activation and expansion. Recently, by using a novel in vitro model of oval cell lines expressing a mutant tyrosine kinase-inactive form of c-Met we demonstrated that autocrine c-Met signalling plays an essential role in promoting oval cell survival. Here, we investigated the significance of the epidermal growth factor receptor (EGFR) signalling in oval cell proliferation and survival, as well as a potential functional crosstalk between the c-Met and the EGFR pathways. We found an autocrine activation of the EGFR-triggered pathway in Met(flx/flx) and Met(-/-) oval cells as judged by constitutive expression of the EGFR ligands, transforming growth factor-alpha (TGF-α) and heparin-binding EGF like growth factor (HB-EGF), and activation of EGFR. On the other hand, treatment with AG1478, a specific inhibitor of EGFR, effectively blocked endogenous and EGF-induced proliferation, while increased serum withdrawal and transforming growth factor-beta (TGF-β)-induced apoptosis. These results suggest that constitutively activated EGFR might promote oval cell proliferation and survival. We found that hepatocyte growth factor (HGF) does not transactivate EGFR nor EGF transactivates c-Met. Furthermore, treatment with AG1478 or EGFR gene silencing did not interfere with HGF-mediated activation of target signals, such as protein kinase B (AKT/PKB), and extracellular signal-regulated kinases 1/2 (ERK 1/2), nor did it have any effect on HGF-induced proliferative and antiapoptotic activities in Met(flx/flx) cells, showing that HGF does not require EGFR activation to mediate such responses. EGF induced proliferation and survival equally in Met(flx/flx) and Met(-/-) oval cells, proving that EGFR signalling does not depend on c-Met tyrosine kinase activity. Together, our results provide strong evidence that in

  18. Jovian longitudinal asymmetry in Io-related and Europa-related auroral hot spots

    Science.gov (United States)

    Dessler, A. J.; Chamberlain, J. W.

    1979-01-01

    Auroral emissions generated by the Jovian moons Io and Europa, originating at the foot of the magnetic flux tubes of the satellites, may be largely limited to longitudes where the planet's ionospheric conductivity is enhanced. The enhanced conductivity is produced by trapped energetic electrons that drift into the Jovian atmosphere in regions where the planet's magnetic field is anomalously weak. The most active auroral hot-spot emissions lie in a sector of the northern hemisphere defined by decametric radio emission. Weaker auroral hot spots are found in the southern hemisphere along a magnetic conjugate trace. The brightness and the longitude of the Jovian hot spots predicted in this paper are in agreement with observations reported by Atreya et al. (1977).

  19. 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)

  20. 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

  1. 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.

  2. 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.

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

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    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.

  4. 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

  5. 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.

  6. 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

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

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    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

  8. Analogue model studies of induction effects at auroral latitudes

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    A. Viljanen

    Full Text Available In addition to field observations and numerical models, geomagnetic induction effects can be studied by scaled analogue model experiments. We present here results of analogue model studies of the auroral electrojet with an Earth model simulating the Arctic Ocean and inland conductivity structures in northern Fennoscandia. The main elements of the analogue model used were salt water simulating the host rock, an aluminium plate corresponding to the ocean and graphite pieces producing the inland highly conducting anomalies. The electrojet was a time-harmonic line current flowing at a (simulated height of 100 km above northern Fennoscandia. The period simulated was 9 min.

    The analogue model results confirmed the well-known rapid increase of the vertical field when the coast is approached from the continent. The increase of the horizontal field due to induced ocean currents was demonstrated above the ocean, as well as the essentially negligible effect of these currents on the horizontal field on the continent.

    The behaviour of the magnetic field is explained with a simple two-dimensional thin-sheet model. The range, or the adjustment distance, of the ocean effect inland was found to be some hundreds of kilometers, which also agrees with earlier results of the Siebert-Kertz separation of IMAGE magnetometer data. The modelled inland anomalies evidently had too large conductivities, but on the other hand, their influence decayed on scales of only some tens of kilometers.

    Analogue model results, thin-sheet calculations, and field observations show that the induction effect on the horizontal magnetic field Bx near the electrojet is negligible. On the other hand, the vertical component Bz is clearly affected by induced currents in the ocean. Evidence of this is the shift of the zero point of Bz 0-1° southwards

  9. 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.

  10. Stepwise tailward retreat of magnetic reconnection: THEMIS observations of an auroral substorm

    Science.gov (United States)

    Ieda, A.; Nishimura, Y.; Miyashita, Y.; Angelopoulos, V.; Runov, A.; Nagai, T.; Frey, H. U.; Fairfield, D. H.; Slavin, J. A.; Vanhamäki, H.; Uchino, H.; Fujii, R.; Miyoshi, Y.; Machida, S.

    2016-05-01

    Auroral stepwise poleward expansions were clarified by investigating a multiple-onset substorm that occurred on 27 February 2009. Five successive auroral brightenings were identified in all-sky images, occurring at approximately 10 min intervals. The first brightening was a faint precursor. The second brightening had a wide longitude; thus, it represented the Akasofu substorm onset. Other brightenings expanded poleward; thus, they were interpreted to be auroral breakups. These breakups occurred stepwise; that is, later breakups were initiated at higher latitudes. Corresponding reconnection signatures were studied using Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite observations between 8 and 24 RE down the magnetotail. The Akasofu substorm onset was not accompanied by a clear reconnection signature in the tail. In contrast, the three subsequent auroral breakups occurred simultaneously (within a few minutes) with three successive fast flows at 24 RE; thus, these were interpreted to be associated with impulsive reconnection episodes. These three fast flows consisted of a tailward flow and two subsequent earthward flows. The flow reversal at the second breakup indicated that a tailward retreat of the near-Earth reconnection site occurred during the substorm expansion phase. In addition, the earthward flow at the third breakup was consistent with the classic tailward retreat near the end of the expansion phase; therefore, the tailward retreat is likely to have occurred in a stepwise manner. We interpreted the stepwise characteristics of the tailward retreat and poleward expansion to be potentially associated by a stepwise magnetic flux pileup.

  11. Observations of Auroral Ionopheric Response Effects As Seen By the MICA Sounding Rocket

    Science.gov (United States)

    Lynch, K. A.; Horak, P.; Fernandes, P. A.; Zettergren, M. D.; Hampton, D. L.; Conde, M.; Hysell, D. L.; Miceli, R. J.; Powell, S.; Lessard, M.; Moen, J. I.; Michell, R.; Samara, M.; Nicolls, M. J.

    2014-12-01

    The auroral sounding rocket mission MICA provides an observational case study of nightside auroral ionospheric conductivity and field structuring, and the relationship of this structure to small-scale downward (return) currents. A large-scale current sheet is observed within an auroral arc, with a scale size comparable to that of the arc. Fine-scale return current structures are seen poleward of the visible arc, with scale sizes comparable to the structuring seen at the boundary of the visible arc. Interpretation of the field signatures as indicators of curl B and div E requires careful consideration of the arc geometry and the obliqueness of the measurement trajectory. Ground imaging data and collocated PFISR observations provide context for the in situ observations. The in situ observations starkly illustrate the inability of the radar to capture the small-scale structuring involved in the ionospheric feedback as indicated by the in situ observations. Upgoing Poynting flux and downward currents in the return current region have scale sizes of kilometers or less in the perpendicular-to-B direction, compared to a PFISR resolution of tens of km (limited by beam spacing for our experiment.) We present comparisons of the observed field-aligned current strengths to terms of the current continuity equation involving gradients of the Pedersen conductivity and the divergence of E, and discuss ionospheric sourcing of return currents. We compare the observations to the calculations of an ionospheric electrostatic model, and discuss the requirements for capturing the ionospheric responses to auroral drivers.

  12. Jovian longitudinal asymmetry in Io-related and Europa-related auroral hot spots

    Energy Technology Data Exchange (ETDEWEB)

    Dessler, A.J.; Chamberlain, J.W.

    1979-06-15

    Jupiter's internal magnetic field is markedly non-dipolar. We propose that Io- or Europa-generated auroral emissions (originating at the foot of either Io's or Europa's magnetic flux tube) are largely restricted to longitudes where Jupiter's ionospheric conductivity is enhanced. Trapped, energetic electrons that drift into Jupiter's atmosphere, in regions where the Jovian magnetic field is anomalously weak, produce the increased conductivity. The longitude range of enchanced auroral hot-spot emissions is thus restricted to an active sector that is determined from dekametric radio emission to lie in the northern hemisphere in the Jovian System III (1965) longitude range of 205/sup 0/ +- 30/sup 0/. Relatively weaker auroral hot spots should occur in the southern hemisphere along the mgnetic conjugate trace covering the longitude range of 215/sup 0/ +- 55/sup 0/. At other longitudes, the brightness of the hot spot should decrease by at least one order of magnitude. These results, with respect to both brightness and longitude, are in accord with the observations of Jovian auroral hot spots reported by Atreya et al. We show that the northern hemisphere foot of either Io's or Europa's magnetic flux tube was in the preferred longitude range (the active sector) at the time of each observation.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  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. Intrahepatic transplantation of hepatic oval cells for fulminant hepatic failure in rats

    Institute of Scientific and Technical Information of China (English)

    Chen-Xuan Wu; Qi Zou; Zheng-Yan Zhu; Ying-Tang Gao; Yi-Jun Wang

    2009-01-01

    AIM:To evaluate the effect of intrahepatic transplantation of hepatic oval cells (HOC) on fulminant hepatic failure (FHF) in rats. METHODS:HOC obtained from rats were labeled wi th green fluocescent protein (GFP) or 5, 6- carboxyfluorescein diacetate succinmidyl ester (CFDASE). Cell fluorescence was observed under fluorescent microscope at 6, 24, 48 and 72 h after labeling. CFDASE labeled HOC (5 × 106 cells each rat) were injected into livers of rats with FHF induced by D-galactosamine. Serum albumin (ALB), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin (TBil) levels were measured at different time points. Liver function of rats was examined on days 3, 7, 14 and 21 after HOC transplantation. RESULTS:The positive rate of GFP and CFDA-SE labeled HOC was 10% and 90%, respectively, with no significant change in cell viabilities. The survival rate was higher in HOC transplantation group than in control group, especially 48 (9/15 vs 6/15) and 72 h (9/15 vs 4/15) after HOC transplantation. The serum ALT, AST and TBil levels were decreased while the serum Alb level was increased after HOC transplantation. Fluorescence became faded and diffused in liver tissues, suggesting that proliferation and differentiation occur in transplanted HOC. CONCLUSION:CFDA-SE is superior to GFP in labeling HOC, although fluorescence intensity is decreased progressively with cell division. HOC transplantation can improve the liver function and increase the survival rate of recipients.

  19. 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

  20. Stent placement for palliation of cor triatriatum dexter in a dog with suspected patent foramen ovale.

    Science.gov (United States)

    Barncord, Kristin; Stauthammer, Christopher; Moen, Sean L; Hanson, Melissa; Gruenstein, Daniel H

    2016-03-01

    An 11 month old spayed, female dog presented with exercise intolerance and cyanosis upon exertion. Echocardiography revealed an imperforate cor triatriatum dexter with mild tricuspid valve dysplasia, an underfilled right ventricle and significant right to left shunting across a presumptive patent foramen ovale. Balloon dilation of the abnormal atrial membrane was initially successful in creating a communication between the right atrial chambers, but stenosis of the original perforation and persistent clinical signs prompted a second intervention. A balloon expandable biliary stent was placed across the abnormal partition, improving caudal venous return to the right ventricle and reducing the right to left shunt. Three months after stent placement, resting oxygen saturation had normalized. Six months after stent placement, exercise tolerance had improved and exertional cyanosis had resolved. Long term follow up will be necessary to assess for remodeling of the right ventricle with improved venous return. Stent placement can be considered as a palliative treatment option for cor triatriatum dexter, especially for stenosis post-balloon dilation. PMID:26777393

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. Prevalence of patent foramen ovale in ischemic stroke in Italy: the SISIFO study.

    Science.gov (United States)

    Consoli, Domenico; Paciaroni, Maurizio; Aguggia, Marco; Melis, Maurizio; Malferrari, Giovanni; Vidale, Simone; Cerrato, Paolo; Sacco, Simona; Gandolfo, Carlo; Bovi, Paolo; Serrati, Carlo; Del Sette, Massimo; Cavallini, Anna; Diomedi, Marina; Postorino, Paolo; Ricci, Stefano

    2014-06-01

    Patent foramen ovale (PFO) is a common congenital anatomical defect in the general population with a mean prevalence of 20 %. Transcranial Doppler sonography and echocardiography, both with infusion of agitated saline as an echo contrast, have been introduced for the diagnosis of PFO. Transesophageal echocardiography is considered the gold standard. Several studies have suggested an association between cryptogenetic stroke and PFO, but the role of this condition as a risk factor for stroke is still debated. The aims of this prospective multicentre study are the evaluation of PFO prevalence in the whole ischemic stroke population and the identification of a stroke recurrence profile risk in patients with PFO. All consecutive patients admitted for acute ischemic stroke and with a confirmed diagnosis at discharge are eligible cases for the study. Demographic and vascular risk factors are registered. Clinical severity is summarized by the National Institute of Health stroke scale. Echocardiographic and transcranial studies are performed in each patient to detect the presence of PFO. Prevalence of PFO will be calculated with 95 % CIs. Univariate analysis will be performed to detect the correlation of PFO with different registered factors and multivariable analysis with PFO as independent variable. The present study should contribute to better identify the role of PFO in ischemic stroke risk and recurrence-related events. Qualifying findings of the study are represented by the high number of enrolled patients, the prospective methodology of the study and the presence of secondary instrumental endpoints.

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

    Energy Technology Data Exchange (ETDEWEB)

    Boutet, Claire, E-mail: claire.boutet@chu-st-etienne.fr [Department of Radiology, University Hospital of Saint-Etienne (France); Thrombosis Research Group EA 3065, Jean Monnet University, Saint-Etienne (France); Rouffiange-Leclair, Laure, E-mail: laurerouffiange@hotmail.com [Department of Radiology, University Hospital of Saint-Etienne (France); Garnier, Pierre, E-mail: pierre.garnier@chu-st-etienne.fr [Thrombosis Research Group EA 3065, Jean Monnet University, Saint-Etienne (France); Department of Neurology, University Hospital of Saint-Etienne (France); Quenet, Sara, E-mail: sara.quenet@chu-st-etienne.fr [Thrombosis Research Group EA 3065, Jean Monnet University, Saint-Etienne (France); Delsart, Daphné, E-mail: daphne.delsart@hotmail.fr [Thrombosis Research Group EA 3065, Jean Monnet University, Saint-Etienne (France); Department of Therapeutic Medicine, CHU Saint-Etienne, Hôpital Nord, Saint-Etienne (France); Inserm, CIE3, F-42055 Saint-Etienne (France); Varvat, Jérôme, E-mail: jvarvat@9online.fr [Thrombosis Research Group EA 3065, Jean Monnet University, Saint-Etienne (France); Department of Neurology, University Hospital of Saint-Etienne (France); Epinat, Magali, E-mail: magali.epinat@chu-st-etienne.fr [Thrombosis Research Group EA 3065, Jean Monnet University, Saint-Etienne (France); Department of Neurology, University Hospital of Saint-Etienne (France); Schneider, Fabien, E-mail: fabien.schneider@univ-st-etienne.fr [Department of Radiology, University Hospital of Saint-Etienne (France); Thrombosis Research Group EA 3065, Jean Monnet University, Saint-Etienne (France); Antoine, Jean-Christophe, E-mail: j.christophe.antoine@chu-st-etienne.fr [Department of Neurology, University Hospital of Saint-Etienne (France); Lyon Neuroscience Research Center, INSERM U1028 – CNRS UMR5292 (France); EA 4338, Jean Monnet University, Saint-Etienne (France); and others

    2014-05-15

    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.

  8. Evidence that Patent Foramen Ovale is not a Risk Factor for Cerebral Ischemia in the Elderly

    Science.gov (United States)

    Jones, Elizabeth F.; Calafiore, Paul; Donnan, Geoffrey A.; Tonkin, Andrew M.

    1994-01-01

    Patent foramen ovale (PFO) may be a risk factor for ischemic stroke in young patients. The aim of this study was to assess the importance of PFO in subjects with a wider age range using patient-control methodology. Transesophageal contrast echocardiography and carotid imaging were performed in 220 consecutive patients with cerebral ischemia (mean age 66 +/- 13 years) and in 202 community-based control subjects (mean age 64 +/- 11 years). Of patients with stroke, 35 (16%) had PFO compared with 31 control subjects (15%) (p = 0.98). Analysis of PFO prevalence by age did not show a significant difference between patients and control subjects in the age groups or equal to 70 years (12% vs 17%; p = 0.43). However, the group aged 450 years was relatively small (26 cases, 19 controls). No significant difference in PFO prevalence was detected between patients with cryptogenic stroke (20%), noncryptogenic stroke (14%), and control subjects (15%). These results suggest that PFO is not a risk factor for cerebral ischemia in subjects aged >50 years, which would have major implications for the investigation and management of stroke patients in this age group. Longitudinal studies are now required to assess the incidence of stroke in symptom free patients with PFO.

  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. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. Nightside auroral zone and polar cap ion outflow as a function of substorm size and phase

    Science.gov (United States)

    Wilson, G. R.; Ober, D. M.; Germany, G. A.; Lund, E. J.

    2004-02-01

    Because the high latitude ionosphere is an important source of plasma for the magnetosphere under active conditions, we have undertaken a study of the way ion outflow from the nightside auroral zone and polar cap respond to substorm activity. We have combined data from the Ultraviolet Imager (UVI) on Polar with ion upflow measurements from the TEAMS instrument on the FAST spacecraft to construct a picture of ion upflow from these regions as a function of substorm size and as a function of time relative to substorm onset. We use data taken during solar minimum in the northern hemisphere between December 1996 and February 1997. We find that the total nightside auroral zone ion outflow rate (averaged over substorm phase) depends on the size of the substorm, increasing by about a factor of 10 for both O+ and H+ from the smallest to the largest substorms in our study. The combined outflow rate from both the polar cap and the nightside auroral zone goes up by a factor of 7 for both ions for the same change in conditions. Regardless of storm size, the nightside auroral zone outflow rate increases by about a factor of 2 after onset, reaching its peak level after about 20 min. These results indicate that the change in the nightside auroral zone ion outflow rate that accompanies substorm onset is not as significant as the change from low to high magnetic activity. As a consequence, the prompt increase in the near earth plasma sheet energy density of O+ and H+ ions that accompanies onset [, 1996] is likely due to local energization of ions already present rather than to the sudden arrival and energization of fresh ionospheric plasma.

  16. 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.

  17. 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 ...

  18. 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.

  19. Numerical optimization of flow uniformity inside an under body- oval substrate to improve emissions of IC engines

    Directory of Open Access Journals (Sweden)

    Om Ariara Guhan C.P.

    2016-07-01

    Full Text Available Oval substrates are widely used in automobiles to reduce the exhaust emissions in Diesel oxidation Catalyst of CI engine. Because of constraints in space and packaging Oval substrate is preferred rather than round substrate. Obtaining the flow uniformity is very challenging in oval substrate comparing with round substrate. In this present work attempts are made to optimize the inlet cone design to achieve the optimal flow uniformity with the help of CATIA V5 which is 3D design tool and CFX which is 3D CFD tool. Initially length of inlet cone and mass flow rate of exhaust stream are analysed to understand the effects of flow uniformity and pressure drop. Then short straight cones and angled cones are designed. Angled cones have been designed by two methodologies. First methodology is rotating flow inlet plane along the substrate in shorter or longer axis. Second method is shifting the flow inlet plane along the longer axis. Large improvement in flow uniformity is observed when the flow inlet plane is shifted along the direction of longer axis by 10, 20 and 30 mm away from geometrical centre. When the inlet plane is rotated again based on 30 mm shifted geometry, significant improvement at rotation angle of 20° is observed. The flow uniformity is optimum when second shift is performed based on second rotation. This present work shows that for an oval substrate flow, uniformity index can be optimized when inlet cone is angled by rotation of flow inlet plane along axis of substrate.

  20. 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...

  1. 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.)

  2. Human hepatocyte growth factor (hHGF-modified hepatic oval cells improve liver transplant survival.

    Directory of Open Access Journals (Sweden)

    Zhu Li

    Full Text Available Despite progress in the field of immunosuppression, acute rejection is still a common postoperative complication following liver transplantation. This study aims to investigate the capacity of the human hepatocyte growth factor (hHGF in modifying hepatic oval cells (HOCs administered simultaneously with orthotopic liver transplantation as a means of improving graft survival. HOCs were activated and isolated using a modified 2-acetylaminofluorene/partial hepatectomy (2-AAF/PH model in male Lewis rats. A HOC line stably expressing the HGF gene was established following stable transfection of the pBLAST2-hHGF plasmid. Our results demonstrated that hHGF-modified HOCs could efficiently differentiate into hepatocytes and bile duct epithelial cells in vitro. Administration of HOCs at the time of liver transplantation induced a wider distribution of SRY-positive donor cells in liver tissues. Administration of hHGF-HOC at the time of transplantation remarkably prolonged the median survival time and improved liver function for recipients compared to these parameters in the other treatment groups (P<0.05. Moreover, hHGF-HOC administration at the time of liver transplantation significantly suppressed elevation of interleukin-2 (IL-2, tumor necrosis factor-α (TNF-α and interferon-γ (IFN-γ levels while increasing the production of IL-10 and TGF-β1 (P<0.05. HOC or hHGF-HOC administration promoted cell proliferation, reduced cell apoptosis, and decreased liver allograft rejection rates. Furthermore, hHGF-modified HOCs more efficiently reduced acute allograft rejection (P<0.05 versus HOC transplantation only. Our results indicate that the combination of hHGF-modified HOCs with liver transplantation decreased host anti-graft immune responses resulting in a reduction of allograft rejection rates and prolonging graft survival in recipient rats. This suggests that HOC-based cell transplantation therapies can be developed as a means of treating severe liver

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. Characteristics of Poker Flat Incoherent Scatter Radar (PFISR) naturally enhanced ion-acoustic lines (NEIALs) in relation to auroral forms

    OpenAIRE

    Michell, R. G.; T. Grydeland; Samara, M.

    2014-01-01

    Naturally enhanced ion-acoustic lines (NEIALs) have been observed with the Poker Flat Incoherent Scatter Radar (PFISR) ever since it began operating in 2006. The nearly continuous operation of PFISR since then has led to a large number of NEIAL observations from there, where common-volume, high-resolution auroral imaging data are available. We aim to systematically distinguish the different types of auroral forms that are associated with different NEIAL features, including s...

  8. 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(+).

  9. Simulation of double layers in a model auroral circuit with nonlinear impedance

    Science.gov (United States)

    Smith, R. A.

    1986-01-01

    A reduced circuit description of the U-shaped potential structure of a discrete auroral arc, consisting of the flank transmission line plus parallel-electric-field region, is used to provide the boundary condition for one-dimensional simulations of the double-layer evolution. The model yields asymptotic scalings of the double-layer potential, as a function of an anomalous transport coefficient alpha and of the perpendicular length scale l(a) of the arc. The arc potential phi(DL) scales approximately linearly with alpha, and for alpha fixed phi (DL) about l(a) to the z power. Using parameters appropriate to the auroral zone acceleration region, potentials of phi (DPL) 10 kV scale to projected ionospheric dimensions of about 1 km, with power flows of the order of magnitude of substorm dissipation rates.

  10. Investigation of Io's Auroral Hiss Emissions Due To Its Motion in Jupiter's Magnetosphere

    CERN Document Server

    Moghimi, M H

    2011-01-01

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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. "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.

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

    Science.gov (United States)

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

    1982-01-01

    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.

  20. Right-hand polarized 4fce auroral roar emissions: 2. Nonlinear generation theory

    Science.gov (United States)

    Yoon, P. H.; LaBelle, J.; Weatherwax, A. T.

    2016-08-01

    Auroral roar emissions are commonly interpreted as Z (or upper hybrid) mode naturally excited by precipitating auroral electrons. Subsequent conversion to escaping radiation makes it possible for these emissions to be detected on the ground. Most emissions are detected as having left-hand (L) circular (or ordinary O) polarization, but the companion paper presents a systematic experimental study on the rare occurrence of the right-hand polarized, or equivalently, extraordinary (X) mode 4fce emission. A similar observation was reported earlier by Sato et al. (2015). The suggested emission mechanism is the nonlinear coalescence of two upper hybrid roars at 2fce. The present paper formulates a detailed theory for such an emission mechanism.

  1. Observations of the auroral hectometric radio emission onboard the INTERBALL-1 satellite

    Science.gov (United States)

    Kuril'Chik, V. N.

    2007-06-01

    The results of five-year (1995 2000) continuous observations of the auroral radio emission (ARE) in the hectometric wavelength range on the high-apogee INTERBALL-1 satellite are presented. Short intense bursts of the auroral hectometric radio emission (AHR) were observed at frequencies of 1463 and 1501 kHz. The bursts were observed predominantly at times when the terrestrial magnetosphere was undisturbed (in the quiet Sun period), and their number decreased rapidly with increasing solar activity. The bursts demonstrated seasonal dependence in the Northern and Southern hemispheres (dominating in the autumn-winter period). Their appearance probably depends on the observation time (UT). A qualitative explanation of the AHR peculiarities is given.

  2. 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

  3. 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

  4. 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...

  5. 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%.

  6. 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...

  7. 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.

  8. The cyclotron maser theory of AKR and Z-mode radiation. [Auroral Kilometric Radiation

    Science.gov (United States)

    Wu, C. S.

    1985-01-01

    The cyclotron maser mechanism which may be responsible for the generation of auroral kilometric radiation and Z-mode radiation is discussed. Emphasis is placed on the basic concepts of the cyclotron maser theory, particularly the relativistic effect of the cyclotron resonance condition. Recent development of the theory is reviewed. Finally, the results of a computer simulation study which helps to understand the nonlinear saturation of the maser instability are reported.

  9. 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...

  10. 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

  11. Optical and radar analysis of auroral curls at high spatial resolution

    Science.gov (United States)

    Dahlgren, Hanna; Kaila, Kari; Ivchenko, Nickolay; Lanchester, Betty; Whiter, Daniel; Marklund, Göran; Aikio, Anita

    Auroral arcs can develop small-scale distortions known as vortex streets or curls. Optical ground-based observations of this phenomenon have indicated that curls are often associated with shear flows. For a comprehensive analysis of the temporal and spatial characteristics associated with the formation and evolution of curls, high resolution optical measurements are required. We report here on an event study of an arc evolving into curls and associated with counter-streaming structures, observed on 23 November 2006 by ground-based optical instrumentation and measured by the European Incoherent Scatter Radar (EISCAT) located outside Tromso, Norway. The optical Instrumentation consisted of three, narrow field-of-view (3 deg x 3 deg) imagers (Auroral Structure and Kinetics), each equipped with different passband filters, together with a white light video camera (FOV: 45 deg x 60 deg, 25 Hz) providing the large-scale context of the event. The temporal evolution of the smallest structures was recorded at a time resolution of 20 Hz. Shear velocities between the center and the edge of the arc are investigated, and the origin and evolution of the observed small-scale auroral features are discussed in the light of existing theories.

  12. 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.

  13. Some features of auroral electric fields as seen in 2D numerical simulations

    Science.gov (United States)

    Thiemann, H.; Singh, N.; Schunk, R. W.

    1984-01-01

    Results of 2D plasma simulations are presented and related to auroral observations. The formation of V-shaped potentials is studied with a 2 1/2 dimensional electrostatic particle-in-cell code for a magnetized plasma. It is shown that amplitudes for perpendicular electric fields are larger than for parallel electric fields, and for Te less than 100 eV, the amplitudes are comparable to the electric fields associated with the electrostatic shocks observed from the S3-3 satellite. The excitation of electrostatic ion-cyclotron EIC waves which occurs in the region below the parallel potential drop is discussed. In auroral plasmas EIC waves are observed above the V-shaped double layers in association with ion beams and field-aligned currents. The results also show that oppositely directed electric fields in the center and at the edges of the simulation region produce oppositely directed currents. Precipitating auroral ions in association with electron inverted-V events are seen by the DMSP-F6 satellite.

  14. Using spectral characteristics to interpret auroral imaging in the 731.9 nm O+ line

    Directory of Open Access Journals (Sweden)

    A. Strømme

    2008-07-01

    Full Text Available Simultaneous observations were made of dynamic aurora during substorm activity on 26 January 2006 with three high spatial and temporal resolution instruments: the ASK (Auroral Structure and Kinetics instrument, SIF (Spectrographic Imaging Facility and ESR (EISCAT Svalbard Radar, all located on Svalbard (78° N, 16.2° E. One of the narrow field of view ASK cameras is designed to detect O+ ion emission at 731.9 nm. From the spectrographic data we have been able to determine the amount of contaminating N2 and OH emission detected in the same filter. This is of great importance to further studies using the ASK instrument, when the O+ ion emission will be used to detect flows and afterglows in active aurora. The ratio of O+ to N2 emission is dependent on the energy spectra of electron precipitation, and was found to be related to changes in the morphology of the small-scale aurora. The ESR measured height profiles of electron densities, which allowed estimates to be made of the energy spectrum of the precipitation during the events studied with optical data from ASK and SIF. It was found that the higher energy precipitation corresponded to discrete and dynamic features, including curls, and low energy precipitation corresponded to auroral signatures that were dominated by rays. The evolution of these changes on time scales of seconds is of importance to theories of auroral acceleration mechanisms.

  15. 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.

  16. Average and worst-case specifications of precipitating auroral electron environment

    Science.gov (United States)

    Hardy, D. A.; Burke, W. J.; Gussenhoven, M. S.; Holeman, E.; Yeh, H. C.

    1985-01-01

    The precipitation electrons in the auroral environment are highly variable in their energy and intensity in both space and time. As such they are a source of potential hazard to the operation of the Space Shuttle and other large spacecraft operating in polar orbit. In order to assess these hazards both the average and extreme states of the precipitating electrons must be determined. Work aimed at such a specification is presented. First results of a global study of the average characteristics are presented. In this study the high latitude region was divided into spatial elements in magnetic local time and corrected geomagnetic latitude. The average electron spectrum was then determined in each spatial element for seven different levels of activity as measured by K sub p using an extremely large data set of auroral observations. Second a case study of an extreme auroral electron environment is presented, in which the electrons are accelerated through field aligned potential as high as 30,000 volts and in which the spacecraft is seen to charge negatively to a potential approaching .5 kilovolts.

  17. 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)

  18. Atrial Septal Aneurysm and Patent Foramen Ovale as Risk Factors for Cryptogenic Stroke in Patients Less Than 55 Years of Age: A Study using Transesophageal Echocardiography

    Science.gov (United States)

    Cabanes, L.; Mas, J. L.; Cohen, A.; Amarenco, P.; Cabanes, P. A.; Oubary, P.; Chedru, F.; Guerin, F.; Bousser, M. G.; deRecondo, J.

    1993-01-01

    Background and Purpose: An association between atrial septal aneurysm and embolic events has been suggested. Atrial septal aneurysm has been shown to be associated with patent foramen ovale and,.in some reports, with mitral valve prolapse. These two latter cardiac disorder; have been identified as potential risk factors for ischemic stroke. The aim of this prospective study was to assess the role of atrial septal aneurysm as an independent risk factor for stroke, especially for cryptogenic stroke. Methods: We studied the prevalence of atrial septal aneurysm, patent foramen ovale, and mitral valve prolapse in 100 consecutive patients aneurysm and patent foramen ovale relied on transesophageal echocardiography with a contrast study and that of mitral valve prolapse, on two-dimensional transthoracic echocardiography. Results: Stepwise logistic regression analysis showed that atrial septal aneurysm (odds ratio, 4.3; 95% confidence interval, 1.3 to 14.6; P=.01) and patent foramen ovale (odds ratio, 3.9; 95% confidence interval, 1.5 to 10; P=.003) but not mitral valve prolapse were significantly associated with the diagnosis of cryptogenic stroke. The stroke odds of a patient with both atrial septal aneurysm and patent foramen ovale were 33.3 times (95% confidence interval, 4.1 to 270) the stroke odds of a patient with neither of these cardiac disorders. For a patient with atrial septal aneurysm of >lo-mm excursion, the stroke odds were approximately 8 times the stroke odds of a patient with atrial septal aneurysm of aneurysm and patent foramen ovale are both significantly associated with cryptogenic stroke and that their association has a marked synergistic effect. Atrial septal aneurysms of >lo-mm excursion are associated with a higher risk of stroke. (Stroke. 1993;24:1865-1873.) KEY WORDS aneurysm echocardiography foramen ovale, patent mitral valve prolapse o young adults

  19. 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.

  20. 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...

  1. 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).

  2. Effect of Ovality on Maximum External Pressure of Helically Coiled Steam Generator Tubes with a Rectangular Wear

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Dong In; Lim, Eun Mo; Huh, Nam Su [Seoul National Univ. of Science and Technology, Seoul (Korea, Republic of); Choi, Shin Beom; Yu, Je Yong; Kim, Ji Ho; Choi, Suhn [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-10-15

    A structural integrity of steam generator tubes of nuclear power plants is one of crucial parameters for safe operation of nuclear power plants. Thus, many studies have been made to provide engineering methods to assess integrity of defective tubes of commercial nuclear power plants considering its operating environments and defect characteristics. As described above, the geometric and operating conditions of steam generator tubes in integral reactor are significantly different from those of commercial reactor. Therefore, the structural integrity assessment of defective tubes of integral reactor taking into account its own operating conditions and geometric characteristics, i. e., external pressure and helically coiled shape, should be made to demonstrate compliance with the current design criteria. Also, ovality is very specific characteristics of the helically coiled tube because it is occurred during the coiling processes. The wear, occurring from FIV (Flow Induced Vibration) and so on, is main degradation of steam generator tube. In the present study, maximum external pressure of helically coiled steam generator tube with wear is predicted based on the detailed 3-dimensional finite element analysis. As for shape of wear defect, the rectangular shape is considered. In particular, the effect of ovality on the maximum external pressure of helically coiled tubes with rectangular shaped wear is investigated. In the present work, the maximum external pressure of helically coiled steam generator tube with rectangular shaped wear is investigated via detailed 3-D FE analyses. In order to cover a practical range of geometries for defective tube, the variables affecting the maximum external pressure were systematically varied. In particular, the effect of tube ovality on the maximum external pressure is evaluated. It is expected that the present results can be used as a technical backgrounds for establishing a practical structural integrity assessment guideline of

  3. SIMULATION OF 3-D DEFORMATION AND MATERIAL FLOW DURING ROLL FORGING PROCESS USING SYSTEM OF OVAL-ROUND GROOVE

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Basing on the analysis of the traits of the roll forging process, a system-model of computer simulation has been established. Three-dimensional rigid-plastic FEM has been used for the simulation of the deformation process in the oval and round pass rolling, including the entering, rolling, and separating stages. The analysis was conducted using the Deform-3D ver. 5.0 code.The important information concerned with the deformation area characteristic, material fiow, and velocity field has been presented. Otherwise, the location of the neutral plane in the deformation area was shown clearly.

  4. 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

  5. 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

  6. Substorm and Magnetosphere Characteristic Scales Inferred from the SuperMAG Auroral Electrojet Indices

    Science.gov (United States)

    Newell, P.; Gjerloev, J.

    2012-04-01

    A generalization of the traditional 12-station auroral electrojet index, AE, to include more than 100 magnetometer stations, SME, is an excellent predictor of global auroral power, even at high cadence (1-min). We use this index, and a data base of more than 53,000 substorms derived from it, covering 1980-2009, to investigate time and energy scales in the magnetosphere, during substorms and otherwise. We find, contrary to common opinion, that substorms do not have a preferred recurrence rate, but instead have two distinct dynamic regimes, each following a power law. The number of substorms recurring after a time Δt, N(Δt), varies as Δt -1.19 for short times (3 hr). Other evidence also shows these distinct regimes for the magnetosphere, including a break in the power law spectra for SME at about 3 h. The time between two consecutive substorms is only weakly correlated (r=0.18 for isolated and r=0.06 for recurrent) with the time until the next, suggesting quasi-periodicity is not common. However substorms do have a preferred size, with the typical peak SME magnitude reaching 400-600 nT, but with a mean of 656 nT, corresponding to a bit less than 40 GW auroral power. More surprisingly, another characteristic scale exists in the magnetosphere, namely a peak in the SME distribution around 61 nT, corresponding to about 5 GW precipitating auroral power. The dominant form of auroral precipitation is diffuse aurora, thus these values are properties of the magnetotail thermal electron distribution. The characteristic 5 GW value specifically represents a preferred minimum below which the magnetotail rarely drops. The magnetotail experiences continuous loss by precipitation, so the existence of a preferred minimum implies driving which rarely disappears altogether. Finally, the distribution of SME values across all times, in accordance with earlier work on AE, is best fit by the sum of two distributions, each normal in log(SME). The lower distribution (with a 40% weighting

  7. 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

  8. 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.

  9. 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

  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. 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

  12. Diameters and form of skull base foramen ovale measured by three-dimensional spiral CT thin-slice scan in healthy adults

    Institute of Scientific and Technical Information of China (English)

    Xiaohua Chen; Fengxian Deng; Shuhang Wei; Tingsong Fang

    2006-01-01

    BACKGROUND: The accurate measurements of various data of the bone diameters of foramen ovale of living person can change the methods of puncturing trigeminal gasserian ganglion via foramen ovale for treating trifacial neuralgia from the experience of puncture operator only to puncture by taking the objective data of measurement as the evidence, which is good for improving the accuracy of puncturing trigeminal ganglion and reducing side effects.OBJECTiVE: To observe the forms of foramen ovales in healthy adults displayed by volume rendering and multi-planar reconstruction after three-dimensional spiral CT thin-slice scan of skull base, and measure the longitudinal diameter and transverse diameter.DESTGN: A repetitive observation and measurement.SETTINGS: Department of Neurosurgery and Department of Medical Imaging, Foshan Hospital of Traditional Chinese Medicine.PARTICTPANTS: Fifty healthy adults (100 sides), who were examined with three-dimensional spiral CT scan,were randomly selected from the Department of Medical Imaging, Foshan Hospital of Traditional Chinese Medicine from January 2005 to January 2006, including 26 males and 24 females, aged 25-68 years with an average of 48 years old. They were all informed and agreed with the examination.METHODS: The subjects were examined with the Philips 16-slice spiral CT-Mx 8000 IDT CT apparatus (Philips Company, Holland), the scanning ranged from 2 cm below the canthomeatal line to the level of suprasellar cistern. The width of collimator was 0.75 mm, pitch was 0.663; tube current was 350 mA, voltage was 120 kV,resolution was 512×512 matrix; slice thickness of reconstruction was 1 mm, and interval was 0.5 mm. After the three-dimensional spiral CT thin-slice scan of skull base, the image post-processing techniques including volume rendering and multi-planar reconstruction were applied to observe the forms of foramen ovales, and measure the size, longitudinal diameter and transverse diameter of the foramen ovales. The

  13. 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.

  14. 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.

  15. 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。

  16. 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.

  17. Pupil-sparing complete third nerve palsy from cryptogenic midbrain stroke in an otherwise-healthy young adult with patent foramen ovale

    Directory of Open Access Journals (Sweden)

    Arif O Khan

    2012-01-01

    Full Text Available Although pupil-sparing in acute unilateral complete third nerve palsy is often a sign of ischemic nerve injury, it is not specific for injury outside of the midbrain. This report documents acute pupil-sparing complete third nerve palsy in an otherwise healthy young adult with patent foramen ovale and associated atrial dilatation who suffered cryptogenic focal midbrain stroke, presumably from a paradoxical embolism. The patent foramen ovale was surgically closed. Over the next several months neurological recovery was complete except for diplopia and relatively comitant hypotropia, which responded well to conventional strabismus surgery.

  18. 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.

  19. Observations of the upper frequency cutoffs of the auroral kilometric radiation

    Directory of Open Access Journals (Sweden)

    J. Hanasz

    Full Text Available Intense auroral kilometric radiation (AKR is being frequently observed with POLRAD from the Auroral Probe (Interball-2. Observations of the abrupt upper frequency cutoffs (UFCs in the spectra of AKR are reported. The UFCs can be observed at a frequency range from 300 to 700 kHz, corresponding to AKR generation altitudes from approximately 4800 to 2100 km, and are distributed in magnetic local time (MLT hours similarly to the AKR events, with a maximum at 1 h MLT. The observed frequency extent of the UFCs is ≤12 kHz, and is often determined by the instrumental resolution (4 kHz. It is suggested that the UFC may be associated with an abrupt switching on of the generation mechanism, when the electron density becomes sufficiently low inside a plasma depletion at an altitude where the ratio of fpe/fce crosses some threshold value. The steepness of the UFCs can imply a non-linear process of generation. The estimated distance of the e-folding field aligned wave amplification is between 3 and 8 km. The UFCs are sometimes, though very seldom (<10%, accompanied by narrow band (less than 4 kHz "ridges" of radiation observed at the cutoff frequency. They are smoothly drifting in frequncy for several minutes. The power density of radiation in the "ridge" can be up to 2 orders of magnitude stronger than in the accompanying wide band emission of AKR. The "ridge" at UFC can imply either energy concentration at the source bottom, or focusing, if specific conditions for the escape of the radiation are assumed.

    Key words. Magnetospheric physics (auroral phenomena; plasma waves and instabilities · Radio science (magnetospheric physics

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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...

  6. Changes in Jupiter’s Great Red Spot (1979-2006) and Oval BA (2000-2006)

    Science.gov (United States)

    Shetty, Sushil; Marcus, Philip S.

    2010-11-01

    We analyze velocity fields of the Great Red Spot (GRS) and Oval BA that were previously extracted from Cassini, Galileo, and Hubble Space Telescope images (Asay-Davis, X.S., Marcus, P.S., Wong, M., de Pater, I. [2009]. Icarus 203, 164-188). Our analyses use reduced-parameter models in which the GRS, Oval BA, and surrounding zonal (east-west) flows are assumed to have piece-wise-constant potential vorticity (PV), but with finite-sized transition regions between the pieces of constant PV rather than sharp steps. The shapes of the regions of constant PV are computed such that the flow is a steady, equilibrium solution of the 2D quasigeostrophic equations when viewed in a frame translating uniformly in the east-west direction. All parameter values of the models, including the magnitudes of the PV, areas of the regions with constant PV, locations of the transition regions, widths of the transition regions, and the value of the Rossby deformation radius, are found with a genetic algorithm such that the velocity produced by the equilibrium solution is a "best-fit" to the observed velocity fields. A Monte Carlo method is used to estimate the uncertainties in the best-fit parameter values. The best-fit results show that there were significant changes (greater than the uncertainties) in the PV of the GRS between Galileo in 1996 and Hubble in 2006. In particular, the shape of the PV anomaly of the GRS became rounder, and the area of the PV anomaly of the GRS decreased by 18%, although the magnitudes of PV in the anomaly remained constant. In contrast, neither the area nor the magnitude of the PV anomaly of the Oval BA changed from 2000, when its cloud cover was white, to 2006, when its cloud cover was red. The best-fit results also show that the areas of the PV anomalies of the GRS and of the Oval BA are smaller than the areas of their corresponding cloud covers at all times. Using the best-fit values of the Rossby deformation radius, we show that the Brunt

  7. Scala tympani drill-out technique for oval window atresia with malformed facial nerve:A report of three cases

    Institute of Scientific and Technical Information of China (English)

    Yang Liu a; Feng Yang b

    2015-01-01

    Objective:To report a scala tympani drill-out technique for managing malformed facial nerve covering the entire oval window (OW). Methods:Data from three cases with OW atresia, malformed stapes and abnormal facial nerve courses were reported, in which a scala tympani drill-out technique was employed with a TORP between the tympanic membrane and scala tympani fenestration for hearing reconstruction. Results: Air conduction hearing improved in two of the three cases following surgery. In the third case, there was no improvement in air conduction hearing following a canal wall up mastoidectomy and tympanoplasty. There were no vertigo, tinnitus or sensorineural hearing loss in the three cases. Conclusion:The scala tympani drill-out technique, which is basically fenestration at the initial part of the basal turn, provides a choice in hearing reconstruction when the OW is completely covered by abarrently coursed facial nerve.

  8. 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

  9. Hemodynamic consequences of a restrictive ductus arteriosus and foramen ovale in fetal transposition of the great arteries.

    Science.gov (United States)

    Talemal, L; Donofrio, M T

    2016-09-16

    D-transposition of the great arteries (D-TGA) is the most commonly diagnosed cyanotic congenital heart disease presenting in the neonatal period. The survival after an arterial switch operation, with freedom from adverse cardiovascular events, has been reported to be as high as 93% at 25 years. However, despite excellent surgical outcomes, there continues to be significant preoperative morbidity and potential mortality due to compromise in the delivery room from foramen ovale closure requiring urgent balloon atrial septostomy for stabilization in the first minutes of life. The prenatal diagnosis of D-TGA using fetal echocardiography has aided in the perinatal management and delivery planning of these infants, lowering preoperative morbidity and mortality and preventing delivery room compromise. Fetuses with D-TGA have more highly oxygenated blood supplying the pulmonary arteries and ductus arteriosus which likely results in ductal constriction and increased pulmonary blood flow. This may be the cause of foramen ovale restriction or closure in-utero, which then increases the risk for postnatal compromise at delivery. Theories regarding the cause of the abnormal pulmonary vasculature that may be seen in D-TGA, including aorto-pulmonary collateral formation, have been proposed but to our knowledge, observation of the ultrasound findings throughout mid and late gestation describing the progression of the abnormal fetal physiology have not been previously described. We present a case of D-TGA in which serial assessment using fetal echocardiography enabled observation of the in-utero progression of disease, predicting postnatal compromise and facilitating the planning of life-saving specialized delivery room care and intervention. PMID:27589547

  10. Generation of auroral kilometric and Z mode radiation by the cyclotron maser mechanism

    Science.gov (United States)

    Omidi, N.; Gurnett, D. A.; Wu, C. S.

    1984-01-01

    The relativistic Doppler-shifted cyclotron resonance condition for EM wave interactions with a plasma defines an ellipse in velocity space when the product of the index of refraction and cosine of the wave normal angle is less than or equal to unity, and defines a partial ellipse when the product is greater than unity. It is also noted that waves with frequencies greater than the gyrofrequency can only resonate with particles moving in the same direction along the magnetic field, while waves with lower frequencies than these resonate with particles moving in both directions along the magnetic field. It is found, in the case of auroral kilometric radiation, that both the upgoing and the downgoing electrons are unstable and can give rise to this radiation's growth. The magnitudes of the growth rates for both the upgoing and downgoing auroral kilometric radiation are comparable, and indicate that the path lengths needed to account for the observed intensities of this radiation are of the order of a few hundred km, which is probably too large. Growth rate calculations for the Z mode radiation show that, for wave frequencies just below the gyrofrequency and wave normal angles at or near 90 deg, the electron distribution is unstable and the growth rates are large enough to account for the observed intensities.

  11. 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.

  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. An Ad-hoc Satellite Network to Measure Filamentary Current Structures in the Auroral Zone

    Science.gov (United States)

    Nabong, C.; Fritz, T. A.; Semeter, J. L.

    2014-12-01

    An ad-hoc cubesat-based satellite network project known as ANDESITE is under development at Boston University. It aims to develop a dense constellation of easy-to-use, rapidly-deployable low-cost wireless sensor nodes in space. The objectives of the project are threefold: 1) Demonstrate viability of satellite based sensor networks by deploying an 8-node miniature sensor network to study the filamentation of the field aligned currents in the auroral zones of the Earth's magnetosphere. 2) Test the scalability of proposed protocols, including localization techniques, tracking, data aggregation, and routing, for a 3 dimensional wireless sensor network using a "flock" of nodes. 3) Construct a 6U Cube-sat running the Android OS as an integrated constellation manager, data mule and sensor node deplorer. This small network of sensor nodes will resolve current densities at different spatial resolutions in the near-Earth magnetosphere using measurements from magnetometers with 1-nT sensitivities and 0.2 nT/√Hz self-noise. Mapping of these currents will provide new constraints for models of auroral particle acceleration, wave-particle interactions, ionospheric destabilization, and other kinetic processes operating in the low-beta plasma of the near Earth magnetosphere.

  14. Alaskan Auroral All-Sky Images on the World Wide Web

    Science.gov (United States)

    Stenbaek-Nielsen, H. C.

    1997-01-01

    In response to a 1995 NASA SPDS announcement of support for preservation and distribution of important data sets online, the Geophysical Institute, University of Alaska Fairbanks, Alaska, proposed to provide World Wide Web access to the Poker Flat Auroral All-sky Camera images in real time. The Poker auroral all-sky camera is located in the Davis Science Operation Center at Poker Flat Rocket Range about 30 miles north-east of Fairbanks, Alaska, and is connected, through a microwave link, with the Geophysical Institute where we maintain the data base linked to the Web. To protect the low light-level all-sky TV camera from damage due to excessive light, we only operate during the winter season when the moon is down. The camera and data acquisition is now fully computer controlled. Digital images are transmitted each minute to the Web linked data base where the data are available in a number of different presentations: (1) Individual JPEG compressed images (1 minute resolution); (2) Time lapse MPEG movie of the stored images; and (3) A meridional plot of the entire night activity.

  15. Zakharov simulations of beam-induced turbulence in the auroral ionosphere

    Science.gov (United States)

    Akbari, H.; Guio, P.; Hirsch, M. A.; Semeter, J. L.

    2016-05-01

    Recent detections of strong incoherent scatter radar echoes from the auroral F region, which have been explained as the signature of naturally produced Langmuir turbulence, have motivated us to revisit the topic of beam-generated Langmuir turbulence via simulation. Results from one-dimensional Zakharov simulations are used to study the interaction of ionospheric electron beams with the background plasma at the F region peak. A broad range of beam parameters extending by more than 2 orders of magnitude in average energy and electron number density is considered. A range of wave interaction processes, from a single parametric decay, to a cascade of parametric decays, to formation of stationary density cavities in the condensate region, and to direct collapse at the initial stages of turbulence, is observed as we increase the input energy to the system. The effect of suprathermal electrons, produced by collisional interactions of auroral electrons with the neutral atmosphere, on the dynamics of Langmuir turbulence is also investigated. It is seen that the enhanced Landau damping introduced by the suprathermal electrons significantly weakens the turbulence and truncates the cascade of parametric decays.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Studies of the auroral ionosphere with the MITHRAS. Final report, October 1982-October 1985

    Energy Technology Data Exchange (ETDEWEB)

    Foster, J.C.

    1986-06-26

    The extensive MITHRAS radar data set was the object of extensive analyses the processes and characteristics of the auroral-latitude ionosphere and thermosphere: 1) High-Latitude Electrodynamics: Ionospheric response to substorms at widely separated local times was investigated. 2) Ionospheric Plasma Transport: The effects of plasma convection on the formation of the midlatitude trough were studied utilizing the wide spatial field of view of the Millstone radar. 3) Convection Snapshots: Simultaneous data from spaced instruments were combined to produce 'snapshots' of the polar and auroral convection pattern. 4) Comparisons with Models: 5) Data Bases Studies and Empirical Models: The extensive data set which resulted from the MITHRAS experimental program was incorporated into a multi-instrument, common format data base. 6) Azimuth Scan Experiments: Analysis of the complex data during MITHRAS azimuth scanning experiments resulted in the capability of mapping the convection electric field within the extended field of the radar. 7) Thermosphere and Exosphere: The diurnal variation of exospheric temperature over 30 degrees of latitude around Millstone Hill was investigated using MITHRAS elevation scan data.

  1. 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

  2. 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.

  3. 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...

  4. 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

  5. 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.

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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...

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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.

  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. Auroral ionospheric F region density cavity formation and evolution: MICA campaign results

    Science.gov (United States)

    Zettergren, M.; Lynch, K.; Hampton, D.; Nicolls, M.; Wright, B.; Conde, M.; Moen, J.; Lessard, M.; Miceli, R.; Powell, S.

    2014-04-01

    Auroral ionospheric F region density depletions observed by PFISR (Poker Flat Incoherent Scatter Radar) during the MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) sounding rocket campaign are critically examined alongside complementary numerical simulations. Particular processes of interest include cavity formation due to intense frictional heating and Pedersen drifts, evolution in the presence of structured precipitation, and refilling due to impact ionization and downflows. Our analysis uses an ionospheric fluid model which solves conservation of mass, momentum, and energy equations for all major ionospheric species. These fluid equations are coupled to an electrostatic current continuity equation to self-consistently describe auroral electric fields. Energetic electron precipitation inputs for the model are specified by inverting optical data, and electric field boundary conditions are obtained from direct PFISR measurements. Thus, the model is driven in as realistic a manner as possible. Both incoherent scatter radar (ISR) data and simulations indicate that the conversion of the F region plasma to molecular ions and subsequent recombination is the dominant process contributing to the formation of the observed cavities, all of which occur in conjunction with electric fields exceeding ˜90 mV/m. Furthermore, the cavities often persist several minutes past the point when the frictional heating stops. Impact ionization and field-aligned plasma flows modulate the cavity depth in a significant way but are of secondary importance to the molecular generation process. Informal comparisons of the ISR density and temperature fits to the model verify that the simulations reproduce most of the observed cavity features to a reasonable level of detail.

  20. 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.

  1. 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.

  2. Auroral ion acceleration from lower hybrid solitary structures: A summary of sounding rocket observations

    Science.gov (United States)

    Lynch, K. A.; Arnoldy, R. L.; Kintner, P. M.; Schuck, P.; Bonnell, J. W.; Coffey, V.

    In this paper we present a review of sounding rocket observations of the ion acceleration seen in nightside auroral zone lower hybrid solitary structures. Observations from Topaz3, Amicist, and Phaze2 are presented on various spatial scales, including the two-point measurements of the Amicist mission. From this collection of observations we will demonstrate the following characteristics of transverse acceleration of ions (TAI) in lower hybrid solitary structures (LHSS). The ion acceleration process is narrowly confined to 90° pitch angle, in spatially confined regions of up to a few hundred meters across B. The acceleration process does not affect the thermal core of the ambient distribution and does not directly create a measurable effect on the ambient ion population outside the LHSS themselves. This precludes observation with these data of any nonlinear feedback between the ion acceleration and the existence or evolution of the density irregularities on which these LHSS events grow. Within the LHSS region the acceleration process creates a high-energy tail beginning at a few times the thermal ion speed. The ion acceleration events are closely associated with localized wave events. Accelerated ions bursts are also seen without a concurrent observation of a localized wave event, for two possible reasons. In some cases, the pitch angles of the accelerated tail ions are elevated above perpendicular; that is, the acceleration occurred below the observer and the mirror force has begun to act upon the distribution, moving it upward from the source. In other cases, the accelerated ion structure is spatially larger than the wave event structure, and the observation catches only the ion event. The occurrence rate of these ion acceleration events is related to the ambient environment in two ways: its altitude dependence can be modeled with the parameter B2/ne, and it is highest in regions of intense VLF activity. The cumulative ion outflow from these LHSS TAI is

  3. 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

  4. 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).

  5. 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.

  6. 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

  7. 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

  8. 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)

  9. 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.

  10. 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.

  11. 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.

  12. Dopamine decreases NMDA currents in the oval bed nucleus of the stria terminalis of cocaine self-administering rats☆

    Science.gov (United States)

    Krawczyk, Michal; deBacker, Julian; Mason, Xenos; Jones, Andrea A.; Dumont, Éric C.

    2014-01-01

    Dopamine (DA) and N-methyl-D-aspartate receptors (NMDARs) contribute in the neural processes underlying drug-driven behaviors. DA is a potent modulator of NMDAR, but few studies have investigated the functional interaction between DA and NMDAR in the context of substance abuse. We combined the rat model of cocaine self-administration with brain slice electrophysiology to study DA modulation of NMDA currents in the oval bed nucleus of the stria terminalis (ovBNST), a dense DA terminal field involved in maintenance of cocaine self-administration amongst other drug related behaviors. Long-Evans rats self-administered intravenous cocaine (0.75 mg/kg/injection) on a progressive ratio (PR) schedule of reinforcement for 15 days and whole-cell patch-clamp recordings were done on the 16th day. DA reduced NMDA currents in brain-slices from cocaine self-administering rats, but not in those of drug-naïve and sucrose self-administering, or when cocaine exposure was passive (yoked), revealing a mechanism unique to voluntary cocaine intake. DA reduced NMDA currents by activating G-protein-coupled D1- and D2-like receptors that converged on phospholipase C and protein phosphatases. Accordingly, our study reveals a mechanism that may contribute to dysfunctional synaptic plasticity associated with drug-driven behaviors during acute withdrawal. PMID:24472317

  13. An unusual case of infective endocarditis: extension of a tricuspid valve vegetation into the left atrium through a patent foramen ovale.

    Science.gov (United States)

    Johri, Amer M; Kovacs, Katherine A; Kafka, Henryk

    2009-07-01

    Tricuspid valve endocarditis frequently occurs in the setting of intravenous drug use. A case of tricuspid valve endocarditis in a 37-year-old woman with a history of intravenous cocaine use is described. Transthoracic echocardiography showed extension of the tricuspid valve mass through a patent foramen ovale and into the left atrium. One week after intravenous antibiotic treatment, the mass no longer traversed the patent foramen ovale, and only two smaller tricuspid valve vegetations remained. The present case demonstrates the value of performing a complete and thorough transthoracic echocardiography to visualize and evaluate both the right- and left-sided consequences of infective endocarditis in intravenous drug users. It also serves as a useful reminder to physicians caring for such patients that right sided endocarditis can have important left-sided complications.

  14. 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

  15. 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...

  16. 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...

  17. Case report: Renal infarction by paradoxical embolism through the patent foramen ovale as an unusual cause of post-operative abdominal pain after sleeve gastrectomy

    Directory of Open Access Journals (Sweden)

    Oleksandr Khoma, Dr

    2016-01-01

    Full Text Available 50-year-old female presented with abdominal pain 9 days post sleeve gastrectomy and was found to have acute renal infarction caused by paradoxical emboli through patent foramen ovale (PFO as a cause of the renal infarction. Renal infarctions caused by paradoxical embolism are rare and have not been previously reported following surgery, bariatric surgery in particular. This report describes presentation, work up and management of a patient with renal infarct following bariatric surgery.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Generation of Alfven-ion cyclotron waves on auroral field lines in the presence of heavy ions

    Science.gov (United States)

    Lysak, R. L.; Temerin, M. A.

    1983-01-01

    Observation of electromagnetic waves in the low-altitude auroral zone at frequencies between the proton and helium gyrofrequencies suggests that Alfven-ion cyclotron waves modified by the presence of helium ions are being excited. Estimates of the growth rates for this mode indicate that the auroral electron beam can provide the free energy for the instability. The effect of the heavy ions is to decrease the group velocity of the waves, leading to larger convective growth. Theoretical wave spectra are computed in the local approximation, which assumes that the gradient scale lengths in density and magnetic field are constant over the ray paths. Narrow banded spectral peaks similar to observations may be produced when the thickness of the electron beam is small (200 m at 3000 km altitude). Narrow beams also limit growth of whistler mode waves, which compete for the free energy of the electron beam.

  4. 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.

  5. 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

  6. 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...

  7. 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.

  8. 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...

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. Interferometric radar observations of filamented structures due to plasma instabilities and their relation to dynamic auroral rays

    Directory of Open Access Journals (Sweden)

    T. Grydeland

    2004-04-01

    Full Text Available Several explanations have been proposed for Naturally Enhanced ion-acoustic Echoes observed at mid- and high-latitude Incoherent Scatter observatories. A decisive measure for distinguishing between these explanations is whether or not simultaneously observed up- and down-shifted enhancement occur simultaneously, or if they are the result of temporal and/or spatial averaging.

    The EISCAT Svalbard Radar has two antennas in the same radar system, which can be used as an interferometer when pointed parallel. In observations from 17 January 2002, between 06:46:10 and 06:46:30 UT, we used this possibility, in combination with direct sampling of the received signals, to yield measurements of "naturally enhanced ion-acoustic echoes" with sufficiently high resolution to resolve such averaging, if any. For the first time, radar interferometry has been employed to estimate the sizes of coherent structures. The observations were coordinated with an image intensified video camera with a narrow field of view. Together, this forms the initial study on the causal relationships between enhanced echoes and fine structure in the auroral activity on sub-kilometer, sub-second scales.

    The results confirm that the enhanced echoes originate from very localised regions (~300m perpendicular to the magnetic field at 500km altitude with varying range distribution, and with high time variability (≈200ms. The corresponding increase in scattering cross section, up to 50dB above incoherent scattering, eliminates theoretical explanations based on marginal stability. The simultaneously observed up- and down-shifted enhanced shoulders, when caused by sufficiently narrow structures to be detected by the interferometer technique, originate predominantly from the same volume. These results have significant impact on theories attempting to explain the enhancements, in particular it is found that the ion

  16. Upper atmospheric effects of the hf active auroral research program ionospheric research instrument (HAARP IRI)

    Energy Technology Data Exchange (ETDEWEB)

    Eccles, V.; Armstrong, R.

    1993-05-01

    The earth's ozone layer occurs in the stratosphere, primarily between 10 and 30 miles altitude. The amount of ozone, O3, present is the result of a balance between production and destruction processes. Experiments have shown that natural processes such as auroras create molecules that destroy O. One family of such molecules is called odd nitrogen of which nitric oxide (NO) is an example. Because the HAARP (HF Active Auroral Research Program) facility is designed to mimic and investigate certain natural processes, a study of possible effects of HAARP on the ozone layer was conducted. The study used a detailed model of the thermal and chemical effects of the high power HF beam, which interacts with free electrons in the upper atmosphere above 50 miles altitude. It was found only a small fraction of the beam energy goes into the production of odd nitrogen molecules, whereas odd nitrogen is efficiently produced by auroras. Since the total energy emitted by HAARP in the year is some 200,000 times less than the energy deposited in the upper atmosphere by auroras, the study demonstrates that HAARP HF beam experiments will cause no measurable depletion of the earth's ozone layer.... Ozone, Ozone depletion, Ozone layer, Odd nitrogen, Nitric oxide, HAARP Emitter characteristics.

  17. Numerical study of the auroral particle transport in the polar upper atmosphere

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Starting from the Boltzmann equation and with some reasonable assumptions, a one-dimensional transport equation of charged energetic particles is derived by taking account of major interactions with neutral species in the upper atmosphere, including the processes of elastic scattering, the excitation, the ionization and the secondary electron production. The transport equation is numerically solved, for a simplified atmosphere consisting only of nitrogen molecules (N2), to obtain the variations of incident electron fluxes as a function of altitude, energy and pitch angle. The model results can describe fairly the transport characteristics of pre-cipitating auroral electron spectra in the polar upper atmosphere; meanwhile the N2 ionization rates calculated from the modeled differential flux spectra also exhibit good agreements with existing empirical models in terms of several key parameters. Taking the energy flux spectra of precipitating electrons observed by FAST satellite flying over EISCAT site on May 15, 1997 as model inputs, the model-calculated ionization rate profile of neutral atmosphere consists reasonably with that recon-structed from electron density measurements by the radar.

  18. Climatology of the Ionospheric Scintillations over the Auroral and Cusp European Regions

    Science.gov (United States)

    Spogli, L.; Alfonsi, L.; de Franceschi, G.; Romano, V.; Aquino, M.; Dodson, A.

    2009-04-01

    Under perturbed conditions coming from the outer space, the ionosphere may become highly turbulent and small scale (from centimeters to meters) irregularities, typically enhancements or depletions of the electron density embedded in the ambient ionosphere, can form causing diffraction effects on the satellites signals passing through them. Such effect can abruptly corrupt the performance of the positioning systems affecting, in turn, the awareness and safety of the modern devices. In this paper we analyze data of ionospheric scintillation in the latitudinal range 57°- 88° N during the period October, November and December 2003 as a first step to develop a "scintillation climatology" over the Northern Europe. The behavior of the scintillation occurrence as function of the magnetic local time and of the corrected magnetic latitude is investigated to characterize the scintillation conditions. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Institute of Engineering Surveying and Space Geodesy (IESSG) of the University of Nottingham manage the same kind of GISTM (GPS Ionospheric Scintillation and TEC monitor) receivers over the European middle and high latitude regions. The results here shown and obtained merging observations from three GISTM, highlight also the possibility to investigate the dynamics of irregularities causing scintillation by combining the information coming from auroral to cusp latitudes. The findings, even if at a very preliminary stage, are here presented also in the frame of possible Space Weather implications.

  19. Auroral ion acoustic wave enhancement observed with a radar interferometer system

    Science.gov (United States)

    Schlatter, N. M.; Belyey, V.; Gustavsson, B.; Ivchenko, N.; Whiter, D.; Dahlgren, H.; Tuttle, S.; Grydeland, T.

    2015-07-01

    Measurements of naturally enhanced ion acoustic line (NEIAL) echoes obtained with a five-antenna interferometric imaging radar system are presented. The observations were conducted with the European Incoherent SCATter (EISCAT) radar on Svalbard and the EISCAT Aperture Synthesis Imaging receivers (EASI) installed at the radar site. Four baselines of the interferometer are used in the analysis. Based on the coherence estimates derived from the measurements, we show that the enhanced backscattering region is of limited extent in the plane perpendicular to the geomagnetic field. Previously it has been argued that the enhanced backscatter region is limited in size; however, here the first unambiguous observations are presented. The size of the enhanced backscatter region is determined to be less than 900 × 500 m, and at times less than 160 m in the direction of the longest antenna separation, assuming the scattering region to have a Gaussian scattering cross section in the plane perpendicular to the geomagnetic field. Using aperture synthesis imaging methods volumetric images of the NEIAL echo are obtained showing the enhanced backscattering region to be aligned with the geomagnetic field. Although optical auroral emissions are observed outside the radar look direction, our observations are consistent with the NEIAL echo occurring on field lines with particle precipitation.

  20. Right-hand polarized 4fce auroral roar emissions: 1. Observations

    Science.gov (United States)

    LaBelle, J.; Chen, Y.

    2016-08-01

    A receiving system installed at Sondrestrom, Greenland, was used to monitor all detectable auroral radio emissions at the fourth harmonic of the electron cyclotron frequency (called 4fce roar emissions) between May 2015 and March 2016. Of 88 events detected, 86 occurred during daylit conditions and were left-hand polarized. Two occurred during darkness conditions and were right-hand polarized. The left-hand and right-hand polarized events had entirely different frequency distributions. One of the right-hand polarized 4fce emissions occurred at the same time as and at exactly twice the frequency of a second harmonic emission (2fce roar). The occurrence rate of 4fce emissions during premidnight hours under daylit conditions at Sondrestrom is 5%, comparable to previously reported occurrence rates of 2fce roar in darkness conditions at optimum latitudes of occurrence, but the occurrence rate of 4fce emissions during dark conditions is much lower, suggesting that if the right-hand polarized events arise from coalescence of 2fce waves, only for a small fraction of nighttime 2fce roar emissions does such a process yield 4fce emissions detectable at ground level.

  1. Negative ions in the auroral mesosphere during a PCA event around sunset

    Directory of Open Access Journals (Sweden)

    C. F. del Pozo

    Full Text Available This is a study of the negative ion chemistry in the mesosphere above Tromsø using a number of EISCAT observations of high energy proton precipitation events during the last solar maximum, and in particular around sunset on 23 October, 1989. In these conditions it is possible to look at the relative importance of the various photodetachment and photodissociation processes controlling the concentration of negative ions. The data analysed are from several UHF GEN11 determinations of the ion-plasma ACF together with the pseudo zero-lag estimate of the `raw' electron density, at heights between 55 km and 85 km, at less than 1 km resolution. The power profiles from the UHF are combined with the 55-ion Sodankylä model to obtain consistent estimates of the electron density, the negative ion concentrations, and the average ion mass with height. The neutral concentrations and ion temperature are given by the MSIS90 model. These parameters are then used to compare the calculated widths of the ion-line with the GEN11 determinations. The ion-line spectrum gives information on the effects of negative ions below 70 km where they are dominant; the spectral width is almost a direct measure of the relative abundance of negative ions.

    Key words. Ionosphere (auroral ionosphere; ion chemistry and composition; particle precipitation.

  2. Non-magnetic aspect sensitive auroral echoes from the lower E region observed at 50 MHz

    Directory of Open Access Journals (Sweden)

    R. Rüster

    Full Text Available Backscatter from E-region irregularities was observed at aspect angles close to 90° (almost parallel to the direction of the magnetic field using the ALOMAR SOUSY radar at Andoya/Norway. Strong electric fields and increased E-region electron temperatures simultaneously measured with the incoherent scatter facility EISCAT proved that the Farley-Buneman plasma instability was excited. In addition, strong particle precipitation was present as inferred from EISCAT electron densities indicating that the gradient drift instability may have been active, too. Backscatter at such large aspect angles was not expected and has not been observed before. The characteristics of the observed echoes, however, are in many aspects completely different from usual auroral radar results: the Doppler velocities are only of the order of 10 m/s, the half-width of the spectra is around 5 m/s, the echoes originate at altitudes well below 100 km, and they seem to be not aspect-sensitive with respect to the magnetic field direction. We, therefore, conclude that the corresponding irregularities are not caused by the mentioned instabilities and that other mechanism have to be invoked.

    Key words. Ionosphere (plasma waves and instabilities; ionosphere irregularities; particle precipitaion · Meteorology and atmospheric dynamics (middle atmosphere dynamics

  3. First Terrestrial Soft X-Ray Auroral Observation by the Chandra X-Ray Observatory

    Science.gov (United States)

    Bhardwaj, Anil; Gladstone, G. Randall; Elsner, Ronald F.; Oestgaard, Nikolai; Waite, J. Hunter, Jr.; Cravens, Thomas E.; Chang, Shen-Wu; Majeed, Tariq; Metzger, Albert E.

    2007-01-01

    Northern auroral regions of Earth were imaged with energetic photons in the 0.1-10keV range using the High-Resolution Camera (HRC-I) aboard the Chandra X-ray Observatory at 10 epochs (each approx.20 min duration) between mid- December 2003 and mid-April 2004. These observations aimed at searching for Earth's soft (X-ray aurora in a comparative study with Jupiter's X-ray aurora, where a pulsating X-ray "hot-spot" has been previously observed by Chandra. The first Chandra soft X-ray observations of Earth's aurora show that it is highly variable 0ntense arcs, multiple arcs, diffuse patches, at times absent). In at least one of the observations an isolated blob of emission is observed near the expected cusp location. A fortuitous overflight of DMSP satellite F13 provided SSJ/4 energetic particle measurements above a bright arc seen by Chandra on 24 January 2004, 20:01-20:22 UT. A model of the emissions expected strongly suggests that the observed soft X-ray signal is bremsstrahlung and characteristic K-shell line emissions of nitrogen and oxygen in the atmosphere produced by electrons.

  4. Magnetic Storm Effects in the Auroral Ionosphere Observed with EISCAT Radar -Two Case Studies

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Storm-time changes of main plasma parameters in the auroral ionosphere are analyzed for two intense storms occurring on May 15, 1997 and Sept. 25, 1998, with emphasis on their relationship to the solar wind dynamic pressure and the IMF Bz component. Strong hard particle precipitation occurred in the initial phase for both storma,associated with high solar wind dynamical pressure. During the recovery phase of the storms, some strong particle precipitation was neither concerned with high solar wind pressure nor southward IMF Bz. Severe negative storm effects depicted by electron density depletion appeared in theF-region during the main and recovery phase of both storms, caused by intensive electric field-related strong Joule/frictional heating when IMF was largely southward. The ion temperature behaved similarly in E- and F-region, but the electron temperature did quite different, with a strong increase in the lower E-region relating to plasma instability excited by strong electric field and a slight decrease in the F-region probably concerning with a cooling process. The field-aligned ion velocity was high and apparently anticorrelated with the northward component of the ion convection velocity.

  5. The MITHRAS: A program of simultaneous radar observations of the high-latitude auroral zone

    Science.gov (United States)

    Delabeaujardiere, O.; Baron, M. J.; Wickwar, V. B.; Senior, C.; Evans, J. V.

    1982-11-01

    An intensive campaign of coordinated incoherent-scatter radar experiments took place in 1981-1982. It was planned to take advantage of the short period during which three incoherent-scatter radars could probe the auroral zone simultaneously. The three incoherent-scatter radars that participated in the MITHRAS experiments were Chatanika, Millstone-Hill, and EISCAT. Collaborative studies were undertaken using data from the DE spacecraft and the stare radar. There were three main types of MITHRAS experiments, each with a different scientific purpose. MITHRAS 1 was aimed at large latitudinal coverage of F-region drifts, electron-densities and temperatures. MITHRAS 2 was designed for very good height and time resolution. MITHRAS 3 was intermediate between the other two modes. It provided both E- and F-region coverage over several degrees in latitude. Under the MITHRAS project, substantial changes and additions were made to the software and hardware systems at Millstone and Chatanika. Thirty-three MITHRAS experiments were performed. Most of the data have been reduced. The analysis and interpretation of the date are well underway.

  6. Tests of Sunspot Number Sequences: 2. Using Geomagnetic and Auroral Data

    CERN Document Server

    Lockwood, Mike; Barnard, Luke A; Scott, Chris J; Usoskin, Ilya G; Nevanlinna, Heikki

    2016-01-01

    We compare four sunspot-number data sequences against geomagnetic and terrestrial auroral observations. The comparisons are made for the original SIDC composite of Wolf-Zurich-International sunspot number [$R_{ISNv1}$], the group sunspot number [$R_{G}$] by Hoyt and Schatten (Solar Phys., 1998), the new "backbone" group sunspot number [$R_{BB}$] by Svalgaard and Schatten (Solar Phys., 2016), and the "corrected" sunspot number [$R_{C}$] by Lockwood at al. (J.G.R., 2014). Each sunspot number is fitted with terrestrial observations, or parameters derived from terrestrial observations to be linearly proportional to sunspot number, over a 30-year calibration interval of 1982-2012. The fits are then used to compute test sequences, which extend further back in time and which are compared to $R_{ISNv1}$, $R_{G}$, $R_{BB}$, and $R_{C}$. To study the long-term trends, comparisons are made using averages over whole solar cycles (minimum-to-minimum). The test variations are generated in four ways: i) using the IDV(1d) an...

  7. Inhomogeneities of plasma density and electric field as sources of electrostatic turbulence in the auroral region

    Energy Technology Data Exchange (ETDEWEB)

    Ilyasov, Askar A., E-mail: asjosik@mail.ru [Space Research Institute of the Russian Academy of Science, Moscow 117997 (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region 141700 (Russian Federation); Chernyshov, Alexander A., E-mail: achernyshov@iki.rssi.ru; Mogilevsky, Mikhail M., E-mail: mogilevsky@romance.iki.rssi.ru [Space Research Institute of the Russian Academy of Science, Moscow 117997 (Russian Federation); Golovchanskaya, Irina V., E-mail: golovchanskaya@pgia.ru; Kozelov, Boris V., E-mail: boris.kozelov@gmail.com [Polar Geophysical Institute of the Russian Academy of Science, Apatity, Murmansk region 184209 (Russian Federation)

    2015-03-15

    Inhomogeneities of plasma density and non-uniform electric fields are compared as possible sources of a sort of electrostatic ion cyclotron waves that can be identified with broadband extremely low frequency electrostatic turbulence in the topside auroral ionosphere. Such waves are excited by inhomogeneous energy-density-driven instability. To gain a deeper insight in generation of these waves, computational modeling is performed with various plasma parameters. It is demonstrated that inhomogeneities of plasma density can give rise to this instability even in the absence of electric fields. By using both satellite-observed and model spatial distributions of plasma density and electric field in our modeling, we show that specific details of the spatial distributions are of minor importance for the wave generation. The solutions of the nonlocal inhomogeneous energy-density-driven dispersion relation are investigated for various ion-to-electron temperature ratios and directions of wave propagation. The relevance of the solutions to the observed spectra of broadband extremely low frequency emissions is shown.

  8. Branches of electrostatic turbulence inside solitary plasma structures in the auroral ionosphere

    Energy Technology Data Exchange (ETDEWEB)

    Golovchanskaya, Irina V.; Kozelov, Boris V. [Polar Geophysical Institute, Apatity 184209 (Russian Federation); Chernyshov, Alexander A.; Mogilevsky, Mikhail M. [Space research Institute, Moscow 117997 (Russian Federation); Ilyasov, Askar A. [Moscow Institute of Physics and Technology, Moscow 141700 (Russian Federation); Space research Institute, Moscow 117997 (Russian Federation)

    2014-08-15

    The excitation of electrostatic turbulence inside space-observed solitary structures is a central topic of this exposition. Three representative solitary structures observed in the topside auroral ionosphere as large-amplitude nonlinear signatures in the electric field and magnetic-field-aligned current on the transverse scales of ∼10{sup 2}–10{sup 3} m are evaluated by the theories of electrostatic wave generation in inhomogeneous background configurations. A quantitative analysis shows that the structures are, in general, effective in destabilizing the inhomogeneous energy-density-driven (IEDD) waves, as well as of the ion acoustic waves modified by a shear in the parallel drift of ions. It is demonstrated that the dominating branch of the electrostatic turbulence is determined by the interplay of various driving sources inside a particular solitary structure. The sources do not generally act in unison, so that their common effect may be inhibiting for excitation of electrostatic waves of a certain type. In the presence of large magnetic-field-aligned current, which is not correlated to the inhomogeneous electric field inside the structure, the ion-acoustic branch becomes dominating. In other cases, the IEDD instability is more central.

  9. 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.

  10. [Stroke. are there any difference between patients with or without patent foramen ovale in left atrial appendage systolic function?].

    Science.gov (United States)

    Contreras, Alejandro E; Perrote, Federico; Concari, Ignacio; Brenna, Eduardo J; Lucero, Cecilia

    2012-01-01

    Introducción: El objetivo del presente trabajo fue comparar la función sistólica de la orejuela de la aurícula izquierda (OAI) en un grupo de pacientes con y sin foramen oval permeable (FOP) quienes sufrieron eventos cerebrovasculares isquémicos. Material y métodos: Entre septiembre de 2010 y octubre de 2011, 17 pacientes fueron enviados para la realización de un ecocardiograma transesofágico (ETE) por haber sufrido un accidente cerebrovascular (ACV). Se definió FOP al pasaje de al menos una burbuja a través del septum interauricular con test de burbujas. Se comparó la velocidad sistólica en la orejuela entre los pacientes con y sin FOP y con un grupo control. Resultados: Fueron 8 mujeres y 9 hombres, con una edad media de 54,1 ± 19,5 años. Todos los pacientes habían sufrido un evento cerebrovascular isquémico, el 41,2% habían tenido ACV, el 52,9% crisis isquémica transitoria y el 5,9% amaurosis fugaz. En la evaluación con ETE, el 11,8% tuvo aneurisma del septum interauricular y el 35,3% FOP. La velocidad sistólica media de la OAI fue 66,3 ± 20,3 cm/seg. No hubo diferencia en la velocidad sistólica de la OAI entre pacientes con o sin FOP (67,5 ± 11,8 cm/seg vs 65,7 ± 24,3 cm/seg respectivamente, p= 0,87). El grupo control compuesto por 8 pacientes, 5 mujeres y 3 hombres, con una edad media de 39,5 ± 18 años, tuvo una velocidad sistólica de la OAI de 77,6 ± 28,9 cm/seg, sin diferencias significativas con los pacientes isquémicos. Conclusión: No hubo diferencias en la función sistólica de la OAI entre pacientes con y sin FOP con eventos cerebrovasculares isquemicos.

  11. 2例输入性卵形疟的实验室检测%Laboratory Detection on Two Cases with Imported Plasmodium ovale Infection

    Institute of Scientific and Technical Information of China (English)

    周瑞敏; 张红卫; 邓艳; 钱丹; 刘颖; 陈伟奇; 颜秋叶; 苏云普; 赵旭东

    2013-01-01

    Objective To compare the laboratory tests of the imported Plasmodium ovale infection and analyse the genetic character. Methods After Giemsa staining and microscopy, CareStartTM rapid detection and nested PCR were used to detect two cases with P. ovale infection returning from Congo (Brazzaville) in Henan Province. Sequencing was performed after PCR amplification using the 18S rRNA genus-specific primers. Their genetic characteristics were analyzed and the sequence homology analysis was performed in the NCBI. Results The two cases were confirmed as P. ovale infection by morphological examination microscopically. Amplified bands were produced by 18S rRNA nested PCR, which was the same with P. ovale in size, whereas the results of CareStart? rapid detection test were all negative. A sequence of 906 bp in length was obtained by sequencing their 18S rRNA genes in which GC accounted for 35.4%, and the sequence showed 99% homology to the corresponding part of the known P. ovale 18S rRNA gene (GenBank accession No. AB182492). Conclusion Both the nested PCR and microscopy confirm the infection of P. ovale. A negative result of CareStartTM rapid detection can not ruled out the Plasmodium infection.%目的 比较输入性卵形疟实验室检测方法,分析他们的基因特征.方法 分别用吉氏染色镜检、CareStartTM疟疾快速诊断试剂盒和巢式PCR等3种方法.对2例河南省自刚果(布)务工归来的输入性卵形疟病例进行检测,并比较检测结果.对2例外周血中疟原虫的18S rRNA基因进行测序、基因特征和同源性分析.结果 2例患者均通过吉氏染色镜检观察到典型的卵形疟原虫形态,巢氏PCR均扩增出与卵形疟预期一致的特异性条带,但CareStartTM疟疾快速诊断试剂盒检测结果均为阴性.对2例外周血中疟原虫的18S rRNA基因测序,获得一条长度均为906 bp的序列,GC含量为35.4%,与已知卵形疟18S rRNA的基因序列(GenBank登录号为AB182492)同源性为99

  12. Hint of star exoplanet interaction by modelling the stellar auroral radio emission of the M8.5 dwarf TVLM 513-46546

    CERN Document Server

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

    2016-01-01

    The stellar auroral radio emission has been recognized in some early-type magnetic stars and in many ultra-cool dwarfs. The typical features are the highly polarized pulses explained in terms of Electron Cyclotron Maser emission mechanism. The A0 type star CU Virginis is the prototype of the stars showing this coherent emission; the repeatability and stability of its auroral radio emission allow us to well study this elusive phenomenon. Taking advantage of the CU Vir insights, we built a 3D-model able to reproduce the timing and pulse profile of the auroral radio emission from a dipolar magnetosphere. This model can be applied to stars with an overall symmetric magnetic field topology and showing auroral radio emission, like the ultra-cool dwarfs. In this paper, we simulate the cyclic circularly-polarized pulses of the ultra-cool dwarf TVLM 513-46546, observed with the VLA at 4.88 and 8.44 GHz on May 2006. The auroral radio emission originates in polar rings located at different elevations as a function of th...

  13. 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)

  14. 山东省2例输入性卵形疟病例报告%Two cases report of the imported ovale malaria in Shandong Province

    Institute of Scientific and Technical Information of China (English)

    肖婷; 于振华; 李继民; 李登俊; 马巧荣; 付婷霞; 魏庆宽; 魏艳彬; 刘凡; 李瑾; 黄炳成; 王用斌; 张本光; 尹昆; 孔庆安

    2012-01-01

    本文报告了2例国外输入卵形疟病例.两患者均为非洲几内亚务工返乡人员,回国后数月因发热、乏力而就医.入院血膜镜检见多期卵形疟疟原虫,环状体较粗大,大滋养体期、配子体期颗粒较粗;受染红细胞明显变形,呈多种不规则形状,具备卵形疟原虫特点.PCR基因产物约800 bp,与卵形疟相符.对两患者应用蒿甲醚肌注和伯氨喹口服规范治疗,分别于7d、10 d痊愈出院.%This paper reported two ovale malaria cases who were imported from abroad. They both had worked in E-quatorial Guinea, and they had received our medical treatment due to the fatigued fever after they returned to China few months later. Many stages of ovale malaria protozoa, thick ring forms, thick granulas in big trophozoite stage and game-tophyte stage were found in blood test. The infected RBC were obviously disfigured, showed irregular shape, and the PCR results of gene diagnosis in two cases were 800 bp fragment size, all being ovals malaria characteristics. The patients received standard treatment with artemetheri intramuscularly and Primaquine orally, and finally they both were cured and discharged after seven and ten days respectively.

  15. 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

  16. The Auroral Spatial Structures Probe: magnetic and electric field measurements during an active aurora at fine spatial and temporal scales

    Science.gov (United States)

    Martineau, R. J.; Pratt, J.; Swenson, C.

    2015-12-01

    The Auroral Spatial Structures Probe was a rocket campaign that launched from Poker Flat on January 28, 2015 at 10:41:01 UTC to make multi-point vector observations of the magnetic and electric fields during an active aurora. With 6 instrumented payloads deployed from the rocket in addition to the main payload, each payload making simultaneous measurements of the magnetic and electric fields, the goals of this mission are to resolve the temporal-spatial ambiguity concerning the structures of the electric and magnetic fields during an active auroral event. The vector nature of these measurements requires an accurate knowledge of attitude throughout the flight. Each payload was equipped with gyroscopes to obtain a post-processed attitude solution after the flight. While the main payload's inertial sensors functioned well, the spin axis gyroscope on the subpayloads saturated due to a design flaw. To obtain the attitude and render the vector measurements useful, a least-squares based approach to estimate the attitude history of the payloads was devised using the magnetic and electric field measurements. Once the attitude solution was applied the temporal structures seen in the magnetic and electric fields while flying through the auroral arc are strongly correlated between payloads. We present the new attitude history estimation approach and discuss its strengths and weaknesses compared to traditional attitude methods. We also present preliminary findings from the magnetic and electric field instruments.The Auroral Spatial Structures Probe was a rocket campaign that launched from Poker Flat on January 28, 2015 at 10:41:01 UTC to make multi-point vector observations of the magnetic and electric fields during an active aurora. With 6 instrumented payloads deployed from the rocket in addition to the main payload, each payload making simultaneous measurements of the magnetic and electric fields, the goals of this mission are to resolve the temporal-spatial ambiguity

  17. Stellar wind-magnetosphere interaction at exoplanets: computations of auroral radio powers

    Science.gov (United States)

    Nichols, J. D.; Milan, S. E.

    2016-09-01

    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 available incident Poynting flux, such that the magnetic Radiometric Bode's Law (RBL) presents a substantial overestimation of the radio powers for hot Jupiters. Our radio powers for hot Jupiters are ˜5-1300 TW for hot Jupiters with field strengths of 0.1-10 BJ orbiting a Sun-like star, while we find that competing effects yield essentially identical powers for hot Jupiters orbiting a young Sun-like star. However, in particular, for planets with weaker magnetic fields, our powers are higher at larger orbital distances than given by the RBL, and there are many configurations of planet that are expected to be detectable using SKA.

  18. Equivalent currents associated with morning-sector geomagnetic Pc5 pulsations during auroral substorms

    Science.gov (United States)

    Kauristie, K.; Uspensky, M. V.; Kleimenova, N. G.; Kozyreva, O. V.; Van De Kamp, M. M. J. L.; Dubyagin, S. V.; Massetti, S.

    2016-04-01

    Space and time variations of equivalent currents during morning-sector Pc5 pulsations (T ˜ 2-8 min) on 2 days (18 January and 19 February 2008) are studied in the context of substorm activity with THEMIS and MIRACLE ground-based instruments and THEMIS P3, P5, and P2 probes. These instruments covered the 22:00-07:00 magnetic local time during the analyzed events. In these cases abrupt changes in the Pc5 amplitudes, intensifications and/or weakenings, were recorded some minutes after auroral breakups in the midnight sector. We analyze three examples of Pc5 changes with the goal to resolve whether substorm activity can have an effect on Pc5 amplitude or not. In two cases (on 19 February) the most likely explanation for Pc5 amplitude changes comes from the solar wind (changes in the sign of interplanetary magnetic field Bz). In the third case (on 18 January) equivalent current patterns in the morning sector show an antisunward-propagating vortex which replaced the Pc5-related smaller vortices and consequently the pulsations weakened. We associate the large vortex with a field-aligned current system due to a sudden, although small, drop in solar wind pressure (from 1 to 0.2 nPa). However, the potential impact of midnight substorm activity cannot be totally excluded in this case, because enhanced fluxes of electrons with high enough energies (˜ 280 keV) to reach the region of Pc5 within the observed delay were observed by THEMIS P2 at longitudes between the midnight and morning-sector instrumentation.

  19. On the collocation between dayside auroral activity and coherent HF radar backscatter

    Directory of Open Access Journals (Sweden)

    J. Moen

    Full Text Available The 2D morphology of coherent HF radar and optical cusp aurora has been studied for conditions of predominantly southward IMF conditions, which favours low-latitude boundary layer reconnection. Despite the variability in shape of radar cusp Doppler spectra, the spectral width criterion of > 220 m s–1 proves to be a robust cusp discriminator. For extended periods of well-developed radar backscatter echoes, the equatorward boundary of the > 220 m s–1 spectral width enhancement lines up remarkably well with the equatorward boundary of the optical cusp aurora. The spectral width boundary is however poorly determined during development and fading of radar cusp backscatter. Closer inspection of radar Doppler profile characteristics suggests that a combination of spectral width and shape may advance boundary layer identification by HF radar. For the two December days studied the onset of radar cusp backscatter occurred within pre-existing 630.0 nm cusp auroral activity and appear to be initiated by sunrise, i.e. favourable radio wave propagation conditions had to develop. Better methods are put forward for analysing optical data, and for physical interpretation of HF radar data, and for combining these data, as applied to detection, tracking, and better understanding of dayside aurora. The broader motivation of this work is to develop wider use by the scientific community, of results of these techniques, to accelerate understanding of dynamic high-latitude boundary-processes. The contributions in this work are: (1 improved techniques of analysis of observational data, yielding meaningfully enhanced accuracy for deduced cusp locations; (2 a correspondingly more pronounced validation of correlation of boundary locations derived from the observational data set; and (3 a firmer physical rationale as to why the good correlation observed should theoretically be expected.

    Key words: Ionosphere (ionospheric

  20. Two types of ion energy dispersions observed in the nightside auroral regions during geomagnetically disturbed periods

    Science.gov (United States)

    Hirahara, M.; Mukai, T.; Nagai, T.; Kaya, N.; Hayakawa, H.; Fukunishi, H.

    1996-04-01

    The Akebono satellite has observed two types of energy dispersion signatures of discrete ion precipitation event in the nightside auroral regions during active geomagnetic conditions. The charged particle experiments and electric and magnetic field detectors on board Akebono provide us with essential clues to characterize the source regions and acceleration and/or injection processes associated with these two types of ion signatures. The magnetic field data obtained simultaneously by the geosynchronous GOES 6 and 7 satellites and the ground magnetograms are useful to examine their relationships with geomagnetic activity. Mass composition data and pitch angle distributions show that different sources and processes should be attributed to two types (Types I and II) of energy dispersion phenomena. Type I consists of multiple bouncing ion clusters constituted by H+. These H+ clusters tend to be detected at the expansion phase of substorms and have characteristic multiple energy-dispersed signatures. Type II consists of O+ energy dispersion(s), which is often observed at the recovery phase. It is reasonable to consider that the H+ clusters of Type I are accelerated by dipolarization at the equator, are injected in the field-aligned direction, and bounce on closed field lines after the substorm onset. We interpret these multiple energy dispersion events as mainly due to the time-of-flight (TOF) effect, although the convection may influence the energy-dispersed traces. Based of the TOF model, we estimate the source distance to be 20-30 RE along the field lines. On the other hand, the O+ energy dispersion of Type II is a consequence of reprecipitation of terrestrial ions ejected as an upward flowing ion (UFI) beam from the upper ionosphere by a parallel electrostatic potential difference. The O+ energy dispersion is induced by the E×B drift during the field-aligned transport from the source region to the observation point.

  1. Combined optical, EISCAT and magnetic observations of the omega bands/Ps6 pulsations and an auroral torch in the late morning hours: a case study

    Directory of Open Access Journals (Sweden)

    V. Safargaleev

    2005-07-01

    Full Text Available We present here the results of multi-instrument observations of auroral torch and Ps6 magnetic pulsations, which are assumed to be the magnetic signature of the spatially periodic optical auroras known as omega bands. Data from TV and ASC cameras in Barentsburg and Ny Ålesund, EISCAT radars in Longyearbyen and Tromsø, as well as IMAGE network were used in this study. The auroral phenomenon which was considered differed from that previously discussed, as it occurred both in an unusual place (high latitudes and at an unusual time (late morning hours. We show that this might occur due to specific conditions in the interplanetary medium, causing the appropriate deformation of the magnetosphere. In such a case, the IMF turned out to be an additional factor in driving the regime of Ps6/omega bands, namely, only by acting together could a substorm onset in the night sector and Bz variations result in their generation. Since the presumable source of Ps6/omega bands does not co-locate with convection reversal boundaries, we suggest the interpretation of the phenomena in the frame of the interchange instability instead of the Kelvin-Helmholtz instability that is widely discussed in the literature in connection with omega auroras. Some numerical characteristics of the auroral torch were obtained. We also emphasize to the dark hole in the background luminosity and the short-lived azimuthally-restricted auroral arc, since their appearance could initiate the auroral torch development.

    Keywords. Magnetospheric physics (Auroral phenomena; Plasma convection; Solar wind-magnetosphere interaction

  2. Temporal evolution of pump beam self-focusing at the High-Frequency Active Auroral Research Program

    OpenAIRE

    Kosch, Mike J.; Pedersen, T.; Mishin, E.; Starks, M; Gerken-Kendall, E.; D. Sentman; Oyama, S.; Watkins, B.

    2007-01-01

    On 4 February 2005 the High-Frequency Active Auroral Research Program (HAARP) facility was operated at 2.85 MHz to produce artificial optical emissions in the ionosphere while passing through the second electron gyroharmonic. All-sky optical recordings were performed with 15 s integration, alternating between 557.7 and 630 nm. We report the first optical observations showing the temporal evolution of large-scale pump wave self-focusing in the magnetic zenith, observed in the 557.7 nm images. ...

  3. Crowd-sourcing, Communicating, and Improving Auroral Science at the Speed of Social Media through Aurorasaurus.org

    Science.gov (United States)

    Patel, K.; MacDonald, E.; Case, N.; Hall, M.; Clayton, J.; Heavner, M.; Tapia, A.; Lalone, N.; McCloat, S.

    2015-12-01

    On March 17, 2015, a geomagnetic storm—the largest of the solar cycle to date— hit Earth and gave many sky watchers around the world a beautiful auroral display. People made thousands of aurora-related tweets and direct reports to Aurorasaurus.org, an interdisciplinary citizen science project that tracks auroras worldwide in real-time through social media and the project's apps and website. Through Aurorasaurus, researchers are converting these crowdsourced observations into valuable data points to help improve models of where aurora can be seen. In this presentation, we will highlight how the team communicates with the public during these global, sporadic events to help drive and retain participation for Aurorasaurus. We will highlight some of the co-produced scientific results and increased media interest following this event. Aurorasaurus uses mobile apps, blogging, and a volunteer scientist network to reach out to aurora enthusiasts to engage in the project. Real-time tweets are voted on by other users to verify their accuracy and are pinned on a map located on aurorasaurus.org to help show the instantaneous, global auroral visibility. Since the project launched in October 2014, hundreds of users have documented the two largest geomagnetic storms of this solar cycle. In some cases, like for the St. Patrick's Day storm, users even reported seeing aurora in areas different than aurora models suggested. Online analytics indicate these events drive users to our page and many also share images with various interest groups on social media. While citizen scientists provide observations, Aurorasaurus gives back by providing tools to help the public see and understand the aurora. When people verify auroral sightings in a specific area, the project sends out alerts to nearby users of possible auroral visibility. Aurorasaurus team members around the world also help the public understand the intricacies of space weather and aurora science through blog articles

  4. Influence of inhomogeneities of the plasma density and electric field on the generation of electrostatic noise in the auroral zone

    Energy Technology Data Exchange (ETDEWEB)

    Chernyshov, A. A., E-mail: achernyshov@iki.rssi.ru; Ilyasov, A. A., E-mail: asjosik@mail.ru; Mogilevskii, M. M., E-mail: mogilevsky@romance.iki.rssi.ru [Russian Academy of Sciences, Space Research Institute (Russian Federation); Golovchanskaya, I. V., E-mail: golovchanskaya@pgia.ru; Kozelov, B. V., E-mail: boris.kozelov@gmail.com [Russian Academy of Sciences, Polar Geophysical Institute (Russian Federation)

    2015-03-15

    In order to study instabilities caused by inhomogeneities of the electric field and plasma density in the auroral zone, numerical algorithms are developed and numerical simulations are performed for different conditions in the background plasma. To this end, a nonlocal dispersion relation for a given type of wave is analyzed. It is shown that the dispersion relation has unstable solutions in a wide range of frequencies and wavenumbers. These solutions manifest themselves in satellite observations as a broadband spectrum of electrostatic perturbations. Two mechanisms of broadband noise generation related to the gradients of the density and electric field are compared.

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

    Directory of Open Access Journals (Sweden)

    M. M. Echim

    2008-05-01

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

  6. Detection of patent foramen ovale by transcranial Doppler%经颅多普勒诊断卵圆孔未闭

    Institute of Scientific and Technical Information of China (English)

    赵世君; 李月春; 王宝军

    2009-01-01

    So far, the method of detection of patent foramen ovale (PFO) by transcranial Doppler (TCD) has had two decades of history. Standardization in contrast-enhanced transcranial Doppler US procedures for cardiac right-to-left shunt detection was proposed in the Venice Consensus Paper in 1999, and some questions were raised at the same time. Over the past 10 years, the researchers have conducted a more in depth study on the method. This article reviews the related research progress.%经颅多普勒(trmscranial Doppler,TCD)诊断卵圆孔未闭(patent foramen ovale, PFO)的方法至今已有20年历史.1999年威尼斯会议规定了此方法的标准化步骤,同时也提出了一些问题.近10年来,研究者对该方法进行了更加深入的研究,文章对相关研究进展做了综述.

  7. Primer reporte de un caso importado de Malaria por Plasmodium ovale curtisi en Paraguay, confirmado por diagnóstico molecular

    Directory of Open Access Journals (Sweden)

    Florencia del Puerto

    2015-04-01

    Full Text Available En países donde el Plasmodium ovale no es común, los microscopistas tienden a identificarlo de manera errónea como Plasmodium vivax. En este trabajo reportamos la identificación de la especie P. ovale curtisi por el método de PCR múltiple semianidada (SnM-PCR y la secuenciación de la subunidad pequeña del gen del ARN 18S, en un paciente paraguayo de 44 años de edad que vino en el 2.013 de Guinea Ecuatorial, África Occidental, a quien se le diagnosticó una infección por P. vivax por microscopía convencional. El empleo de métodos moleculares para la identificación de casos importados de infección con especies del género Plasmodium es uno de los objetivos principales en el control y la prevención de la malaria en Paraguay, teniendo en cuenta que el país se encuentra en fase de pre-eliminación de la enfermedad.

  8. The Influence of the Punched Delta Wings on Flow Pattern and Heat Transfer Characteristic in a Fin-and-Oval-Tube Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Amnart Boonloi

    2015-01-01

    Full Text Available 3D numerical investigations are performed to study the heat transfer, friction factor, and thermal performance of a fin-and-oval heat exchanger with punched delta wings for a range of 500 ≤ Re ≤ 2500 (based on the hydraulic diameter. The influences of the punched angles, 20°, 30°, and 45°, flow directions, wing tips pointing downstream and upstream, and pitch ratios, 2, 3, 4, 5, and 6, are investigated. The results show that the use of the punched delta wings in the fin-and-oval-tube heat exchanger leads to an enhancement in the heat transfer and friction loss as compared to the plain fin for all cases (Nu/Nu0 and f/f0 higher than 1. The enhancements of the heat transfer and friction factor are around 1.01–1.22 and 1.37–2.65 times higher than the base case, respectively. The punched delta wings create the vortex flows through the test section that helps enhance the strength of the impinging flow on the tube walls. The impingement of the fluid flow is an important key to augment the heat transfer rate and thermal performance in the heat exchanger.

  9. Letter to the EditorOn the use of the sunspot number for the estimation of past solar and upper atmosphere conditions from historical and modern auroral observations

    Directory of Open Access Journals (Sweden)

    J. M Vaquero

    2005-07-01

    Full Text Available In this short contribution the use of different sunspot numbers for the estimation of past solar and upper atmosphere conditions from historical and modern auroral observations realised by Schröder et al. (2004 is analysed. Moreover, some comments are made on the relationships between mean annual visual observations of the auroras at middle latitudes of Europe and the mean annual sunspot number during 1780–1829. Keywords. Atmospheric composition and structure (Airglow and aurora – Magnetospheric physics (Auroral phenomena, solar wind-magnetosphere interactions – History of geophysics (Solar-planetary relationship

  10. Wave and Particle Interactions in the High and Low-Altitude Auroral Region During Rising Solar Activity

    Science.gov (United States)

    Gurnett, Donald A.; Menietti, J. D.

    2003-01-01

    The project has resulted in four separate investigations, which are each in various stages of publication in the refereed scientific journals. The first investigation was of the generation of electrostatic electron cyclotron waves observed by the Polar spacecraft throughout the auroral regions, dayside cusp, and polar magnetosphere. We have since discovered that these waves are also present within the magnetopause and magnetosheath, which is one of the topics of a second study, entitled: 'Polar observations of plasma waves in and near the dayside magnetopause/magnetosheath.' A third study of plasma waves focussed on kilometric continuum (KC) emission. This work is reported in a paper entitled 'Near-source and Remote Observations of Kilometric Continuum Radiation From Multi-spacecraft Observations'.The final investigation of this program concerns the possible transverse heating of auroral ions by impulsive wave structures. We summarize that substantial transverse ion heating has already occurred at lower altitudes. Abstracts of the above four studies are included in the Appendix to this final report.

  11. Tomography-like retrieval of auroral volume emission ratios for the 31 January 2008 Hotel Payload 2 event

    Science.gov (United States)

    Enell, C.-F.; Gustavsson, B.; Brändström, B. U. E.; Sergienko, T. I.; Verronen, P. T.; Rydesäter, P.; Sandahl, I.

    2012-01-01

    Quantitative tomography-like volume estimates of the N2+(1N) emission at 427.8 nm, the O(1S) emission at 557.7 nm and the O(1D) emission at 630.0 nm can be retrieved from data from the Auroral Large Imaging System (ALIS) remote-controlled spectral imagers operated at field stations in northern Sweden and Norway. This paper presents a case study of a quiet auroral arc passing over the common volume of the imagers in the evening of 31 January 2008, before the launch of the Hotel Payload 2 (HotPay 2) rocket from Andøya Rocket Range. The reconstructed spectroscopic ratios at the lower altitudes close to the mesopause region can be used as indicators of the NO and O profiles, as the atomic oxygen O(1S) and O(1D) states are excited partly through chemical reactions. The profiles of the ratios of the volume emission rates ɛ557.7 and ɛ427.8 observed by ALIS over northern Norway show nothing unambiguously unusual within the accuracy of the calibration and retrieval, whereas HotPay 2 indicated subsidence of lower thermospheric air, with higher NO concentrations. This is consistent with observations of NO and CO by satellite instruments, which indicate subsidence in vortex filaments only in the NW as seen from the Scandinavian mainland.

  12. Tomography-like retrieval of auroral volume emission ratios for the 31 January 2008 Hotel Payload 2 event

    Directory of Open Access Journals (Sweden)

    C.-F. Enell

    2012-01-01

    Full Text Available Quantitative tomography-like volume estimates of the N2+(1N emission at 427.8 nm, the O(1S emission at 557.7 nm and the O(1D emission at 630.0 nm can be retrieved from data from the Auroral Large Imaging System (ALIS remote-controlled spectral imagers operated at field stations in northern Sweden and Norway. This paper presents a case study of a quiet auroral arc passing over the common volume of the imagers in the evening of 31 January 2008, before the launch of the Hotel Payload 2 (HotPay 2 rocket from Andøya Rocket Range. The reconstructed spectroscopic ratios at the lower altitudes close to the mesopause region can be used as indicators of the NO and O profiles, as the atomic oxygen O(1S and O(1D states are excited partly through chemical reactions. The profiles of the ratios of the volume emission rates ε557.7 and ε427.8 observed by ALIS over northern Norway show nothing unambiguously unusual within the accuracy of the calibration and retrieval, whereas HotPay 2 indicated subsidence of lower thermospheric air, with higher NO concentrations. This is consistent with observations of NO and CO by satellite instruments, which indicate subsidence in vortex filaments only in the NW as seen from the Scandinavian mainland.

  13. Auroral radio emission from late L and T dwarfs: A new constraint on dynamo theory in the substellar regime

    CERN Document Server

    Kao, Melodie M; Pineda, J Sebastian; Escala, Ivanna; Burgasser, Adam; Bourke, Stephen; Stevenson, David

    2015-01-01

    We have observed 6 late-L and T dwarfs with the Karl G. Jansky Very Large Array (VLA) to investigate the presence of highly circularly polarized radio emission, associated with large-scale auroral currents. Previous surveys encompassing ~60 L6 or later targets in this spectral range have yielded only one detection. Our sample includes the previously detected T6.5 dwarf 2MASS 10475385+2124234 as well as 5 new targets selected for the presence of H-alpha emission or optical/infrared photometric variability, which are possible manifestations of auroral activity. We detect 2MASS 10475385+2124234, as well as 4 of the 5 targets in our biased sample, including the strong IR variable SIMP J01365662+0933473 and bright H-alpha emitter 2MASS 12373919+6526148, reinforcing the possibility that activity at these disparate wavelengths is related. The radio emission frequency corresponds to a precise determination of the lower-bound magnetic field strength near the surface of each dwarf and this new sample provides robust co...

  14. The location of the open-closed magnetic field line boundary in the dawn sector auroral ionosphere

    Directory of Open Access Journals (Sweden)

    J. A. Wild

    2004-11-01

    Full Text Available As a measure of the degree of coupling between the solar wind-magnetosphere-ionosphere systems, the rate at which the size of the polar cap (the region corresponding to ionospheric termini of open magnetic flux tubes varies is of prime importance. However, a reliable technique by which the extent of the polar cap might be routinely monitored has yet to be developed. Current techniques provide particularly ambiguous indications of the polar cap boundary in the dawn sector. We present a case study of space- and ground-based observations of the dawn-sector auroral zone and attempt to determine the location of the polar cap boundary using multi-wavelength observations of the ultraviolet aurora (made by the IMAGE FUV imager, precipitating particle measurements (recorded by the FAST, DMSP, and Cluster 1 and 3 satellites, and SuperDARN HF radar observations of the ionospheric Doppler spectral width boundary. We conclude that in the dawn sector, during the interval presented, neither the poleward edge of the wideband auroral UV emission (140-180nm nor the Doppler spectral width boundary were trustworthy indicators of the polar cap boundary location, while narrow band UV emissions in the range 130-140nm appear to be much more reliable.

  15. Electrostatic solitary structures in presence of non-thermal electrons and a warm electron beam on the auroral field lines

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S. V. [Indian Institute of Geomagnetism, Navi Mumbai (India); School of Physics, University of Kwazulu-Natal, Durban (South Africa); Lakhina, G. S. [Indian Institute of Geomagnetism, Navi Mumbai (India); Bharuthram, R. [University of the Western Cape, Bellville (South Africa); Pillay, S. R. [School of Physics, University of Kwazulu-Natal, Durban (South Africa)

    2011-12-15

    Electrostatic solitary waves (ESWs) have been observed by satellites in the auroral region of the Earth's magnetosphere. These ESWs are found to be having both positive and negative electrostatic potentials. Using the Sagdeeev psuedo-potential technique, arbitrary amplitude electron-acoustic solitary waves/double layers are studied in an unmagnetized plasma consisting of non-thermally distributed hot electrons, fluid cold electrons, a warm electron beam, and ions. The inertia of the warm electrons, and not the beam speed, is essential for the existence of positive potential solitary structures. Existence domains for positive as well as negative potential electrostatic solitons/double layers are obtained. For the typical auroral region parameters, the electric field amplitude of the negative potential solitons is found to be in the range {approx}(3-30) mV/m and {approx}(5-80) mV/m for the positive potential solitons. For the negative potential solitons/double layers, the amplitudes are higher when their widths are smaller. On the other hand, the amplitude of the positive potential structures increase with their widths.

  16. Auroral Radio Emission from Late L and T Dwarfs: A New Constraint on Dynamo Theory in the Substellar Regime

    Science.gov (United States)

    Kao, Melodie M.; Hallinan, Gregg; Pineda, J. Sebastian; Escala, Ivanna; Burgasser, Adam; Bourke, Stephen; Stevenson, David

    2016-02-01

    We have observed six late L and T dwarfs with the Karl G. Jansky Very Large Array (VLA) to investigate the presence of highly circularly polarized radio emission, associated with large-scale auroral currents. Previous surveys encompassing ∼60 L6 or later targets have yielded only one detection. Our sample includes the previously detected T6.5 dwarf 2MASS 10475385+2124234, as well as five new targets selected for the presence of Hα emission and/or optical infrared photometric variability, which are possible manifestations of auroral activity. We detect 2MASS 10475385+2124234, as well as four of the five targets in our biased sample, including the strong IR-variable source SIMP J01365662+0933473 and bright Hα emitter 2MASS 12373919+6526148, reinforcing the possibility that activity at these disparate wavelengths is related. The radio emission frequency corresponds to a precise determination of the lower-bound magnetic field strength near the surface of each dwarf, and this new sample provides robust constraints on dynamo theory in the low-mass brown dwarf regime. Magnetic fields ≳ 2.5 kG are confirmed for five of six targets. Our results provide tentative evidence that the dynamo operating in this mass regime may be inconsistent with predicted values from a recently proposed model. Further observations at higher radio frequencies are essential for verifying this assertion.

  17. Tests of Sunspot Number Sequences: 2. Using Geomagnetic and Auroral Data

    Science.gov (United States)

    Lockwood, M.; Owens, M. J.; Barnard, L.; Scott, C. J.; Usoskin, I. G.; Nevanlinna, H.

    2016-06-01

    We compare four sunspot-number data sequences against geomagnetic and terrestrial auroral observations. The comparisons are made for the original Solar Influences Data Center (SIDC) composite of Wolf/Zürich/International sunspot number [ R_{ISNv1}], the group sunspot number [ RG] by Hoyt and Schatten (Solar Phys. 181, 491, 1998), the new "backbone" group sunspot number [ R_{BB}] by Svalgaard and Schatten (Solar Phys., DOI 10.1007/s11207-015-0815-8, 2016), and the "corrected" sunspot number [ RC] by Lockwood, Owens, and Barnard (J. Geophys. Res. 119, 5172, 2014a). Each sunspot number is fitted with terrestrial observations, or parameters derived from terrestrial observations to be linearly proportional to sunspot number, over a 30-year calibration interval of 1982 - 2012. The fits are then used to compute test sequences, which extend further back in time and which are compared to R_{ISNv1}, RG, R_{BB}, and RC. To study the long-term trends, comparisons are made using averages over whole solar cycles (minimum-to-minimum). The test variations are generated in four ways: i) using the IDV(1d) and IDV geomagnetic indices (for 1845 - 2013) fitted over the calibration interval using the various sunspot numbers and the phase of the solar cycle; ii) from the open solar flux (OSF) generated for 1845 - 2013 from four pairings of geomagnetic indices by Lockwood et al. (Ann. Geophys. 32, 383, 2014a) and analysed using the OSF continuity model of Solanki, Schüssler, and Fligge (Nature, 408, 445, 2000), which employs a constant fractional OSF loss rate; iii) the same OSF data analysed using the OSF continuity model of Owens and Lockwood (J. Geophys. Res. 117, A04102, 2012), in which the fractional loss rate varies with the tilt of the heliospheric current sheet and hence with the phase of the solar cycle; iv) the occurrence frequency of low-latitude aurora for 1780 - 1980 from the survey of Legrand and Simon (Ann. Geophys. 5, 161, 1987). For all cases, R_{BB} exceeds the test

  18. On the relationship between auroral absorption, electrojet currents and plasma convection

    Directory of Open Access Journals (Sweden)

    A. C. Kellerman

    2009-02-01

    Full Text Available In this study, the relationship between auroral absorption, electrojet currents, and ionospheric plasma convection velocity is investigated using a series of new methods where temporal correlations are calculated and analysed for different events and MLT sectors. We employ cosmic noise absorption (CNA observations obtained by the Imaging Riometer for Ionospheric Studies (IRIS system in Kilpisjärvi, Finland, plasma convection measurements by the European Incoherent Scatter (EISCAT radar, and estimates of the electrojet currents derived from the Tromsø magnetometer data. The IRIS absorption and EISCAT plasma convection measurements are used as a proxy for the particle precipitation component of the Hall conductance and ionospheric electric field, respectively. It is shown that the electrojet currents are affected by both enhanced conductance and electric field but with the relative importance of these two factors varying with magnetic local time (MLT. The correlation between the current and electric field (absorption is the highest at 12:00–15:00 MLT (00:00–03:00 MLT. It is demonstrated that the electric-field-dominant region is asymmetric with respect to magnetic-noon-midnight meridian extending from 09:00 to 21:00 MLT. This may be related to the recently reported absence of mirror-symmetry between the effects of positive and negative IMF By on the high-latitude plasma convection pattern. The conductivity-dominant region is somewhat wider than previously thought extending from 21:00 to 09:00 MLT with correlation slowly declining from midnight towards the morning, which is interpreted as being in part due to high-energy electron clouds gradually depleting and drifting from midnight towards the morning sector. The conductivity-dominant region is further investigated using the extensive IRIS riometer and Tromsø magnetometer datasets with results showing a distinct seasonal dependence. The region of high current

  19. Dynamics of ionosphere disturbances along the Eastern-Asian meridian from auroral to equatorial latitudes

    Science.gov (United States)

    Pirog, Olga; Zherebtsov, Gelii; Kurkin, Vladimir; Shi, J. K.; Wang, Xiao

    The research results of ionosphere variation in the Eastern-Asian sector observed at the decay and minimum of solar activity (SA) in the period 2004-2007 during geomagnetic disturbances are presented. Data from ionospheric stations located within the latitude-longitude sector (20-70N, 90-160E), oblique-incidence sounding on the radio paths Magadan-Irkutsk and No-rilsk -Irkutsk and results of total electron content (TEC) measurements at the network of GPS ground-based receivers are used to analyze the variations in ionospheric parameters. Data of zenith photometers are applied to investigate the disturbances of atmospheric emissions. Four groups of anomalous ionospheric disturbances observed during the low solar activity are re-vealed: falls of electron density in the evening hour connected with the formation of equatorial wall of MIT, large-scale ionospheric disturbances, wavelike disturbances with the period of two days, and sharp short-term fluctuations in the electron density more intensive at the middle latitudes during the storm main phase. It was also found that often there was no direct con-nection between ionospheric disturbances and geomagnetic activity during moderate magnetic storms in solar minimum. Observed disturbances can be induced by the joint action of a few factors: the increase in electric field of magnetospheric convection, the generation of AGWs in the auroral zone and their propagation southwestward, and the disturbed neutral winds generated by the large-scale storm-induced thermospheric circulation in addition to TADs as-sociated with winds. The reason for occurrence of the wavelike disturbance with the periods from two till seven days can be the planetary atmospheric waves. The numerical model for ionosphere-plasmasphere coupling was used to interpret the certain of observed data. It is ob-tained that use of empirical models of electron precipitation, magnetospheric convection and thermospheric parameters with the correction by the observed

  20. Plasma flows, Birkeland currents and auroral forms in relation to the Svalgaard-Mansurov effect

    Directory of Open Access Journals (Sweden)

    P. E. Sandholt

    2012-05-01

    Full Text Available The traditional explanation of the polar cap magnetic deflections, referred to as the Svalgaard-Mansurov effect, is in terms of currents associated with ionospheric flow resulting from the release of magnetic tension on newly open magnetic field lines. In this study, we aim at an updated description of the sources of the Svalgaard-Mansurov effect based on recent observations of configurations of plasma flow channels, Birkeland current systems and aurorae in the magnetosphere-ionosphere system. Central to our description is the distinction between two different flow channels (FC 1 and FC 2 corresponding to two consecutive stages in the evolution of open field lines in Dungey cell convection, with FC 1 on newly open, and FC 2 on old open, field lines. Flow channel FC 1 is the result of ionospheric Pedersen current closure of Birkeland currents flowing along newly open field lines. During intervals of nonzero interplanetary magnetic field By component FC 1 is observed on either side of noon and it is accompanied by poleward moving auroral forms (PMAFs/prenoon and PMAFs/postnoon. In such cases the next convection stage, in the form of flow channel FC 2 on the periphery of the polar cap, is particularly important for establishing an IMF By-related convection asymmetry along the dawn-dusk meridian, which is a central element causing the Svalgaard-Mansurov effect. FC 2 flows are excited by the ionospheric Pedersen current closure of the northernmost pair of Birkeland currents in the four-sheet current system, which is coupled to the tail magnetopause and flank low-latitude boundary layer. This study is based on a review of recent statistical and event studies of central parameters relating to the magnetosphere-ionosphere current systems mentioned above. Temporal-spatial structure in the current systems is obtained by ground-satellite conjunction studies. On this point we emphasize the important information derived

  1. The dynamics and relationships of precipitation, temperature and convection boundaries in the dayside auroral ionosphere

    Directory of Open Access Journals (Sweden)

    J. Moen

    2004-06-01

    Full Text Available A continuous band of high ion temperature, which persisted for about 8h and zigzagged north-south across more than five degrees in latitude in the dayside (07:00-15:00MLT auroral ionosphere, was observed by the EISCAT VHF radar on 23 November 1999. Latitudinal gradients in the temperature of the F-region electron and ion gases (Te and Ti, respectively have been compared with concurrent observations of particle precipitation and field-perpendicular convection by DMSP satellites, in order to reveal a physical explanation for the persistent band of high Ti, and to test the potential role of Ti and Te gradients as possible markers for the open-closed field line boundary. The north/south movement of the equatorward Ti boundary was found to be consistent with the contraction/expansion of the polar cap due to an unbalanced dayside and nightside reconnection. Sporadic intensifications in Ti, recurring on ~10-min time scales, indicate that frictional heating was modulated by time-varying reconnection, and the band of high Ti was located on open flux. However, the equatorward Ti boundary was not found to be a close proxy of the open-closed boundary. The closest definable proxy of the open-closed boundary is the magnetosheath electron edge observed by DMSP. Although Te appears to be sensitive to magnetosheath electron fluxes, it is not found to be a suitable parameter for routine tracking of the open-closed boundary, as it involves case dependent analysis of the thermal balance. Finally, we have documented a region of newly-opened sunward convecting flux. This region is situated between the convection reversal boundary and the magnetosheath electron edge defining the open-closed boundary. This is consistent with a delay of several minutes between the arrival of the first (super-Alfvénic magnetosheath electrons and the response in the ionospheric

  2. Origin of type-2 thermal-ion upflows in the auroral ionosphere

    Directory of Open Access Journals (Sweden)

    L. M. Kagan

    2005-01-01

    Full Text Available The origin of thermal ion outflows exceeding 1km/s in the high-latitude F-region has been a subject of considerable debate. For cases with strong convection electric fields, the "evaporation" of the ions due to frictional heating below 400-500km has been shown to provide some satisfactory answers. By contrast, in the more frequent subclass of outflow events observed over auroral arcs, called type-2, there is no observational evidence for ion frictional heating. Instead, an electron temperature increase of up to 6000° K is observed over the outflow region. In this case, field-aligned electric fields have long been suspected to be involved, but this explanation did not seem to agree with expectations from the ion momentum balance. In the present work we provide a consistent scenario for the type-2 ion upflows based on our case study of an event that occurred on 20 February 1990. We introduce, for the first time, the electron energy balance in the analysis. We couple this equation with the ion momentum balance to study the salient features of the observations and conclude that type-2 ion outflows and the accompanying electron heating events are indeed consistent with the existence of a field-aligned electric field. However, for our explanation to work, we have to require that an allowance be made for electron scattering by high frequency turbulence. This turbulence could be generated at first by the very fast response of the electrons themselves to a newly imposed electric field that would be partly aligned with the geomagnetic field. The high frequencies of the waves would make it impossible for the ions to react to the waves. We have found the electron collision frequency associated with scattering from the waves to be rather modest, i.e. comparable to the ambient electron-ion collision frequency. The field-aligned electric field inferred from the observations is likewise of the same order of magnitude as the normal ambipolar field, at least for

  3. Dependence of the high-latitude plasma irregularities on the auroral activity indices: a case study of 17 March 2015 geomagnetic storm

    Science.gov (United States)

    Cherniak, Iurii; Zakharenkova, Irina

    2015-09-01

    The magnetosphere substorm plays a crucial role in the solar wind energy dissipation into the ionosphere. We report on the intensity of the high-latitude ionospheric irregularities during one of the largest storms of the current solar cycle—the St. Patrick's Day storm of 17 March 2015. The database of more than 2500 ground-based Global Positioning System (GPS) receivers was used to estimate the irregularities occurrence and dynamics over the auroral region of the Northern Hemisphere. We analyze the dependence of the GPS-detected ionospheric irregularities on the auroral activity. The development and intensity of the high-latitude irregularities during this geomagnetic storm reveal a high correlation with the auroral hemispheric power and auroral electrojet indices (0.84 and 0.79, respectively). Besides the ionospheric irregularities caused by particle precipitation inside the polar cap region, evidences of other irregularities related to the storm enhanced density (SED), formed at mid-latitudes and its further transportation in the form of tongue of ionization (TOI) towards and across the polar cap, are presented. We highlight the importance accounting contribution of ionospheric irregularities not directly related with particle precipitation in overall irregularities distribution and intensity.

  4. 端粒酶在大鼠肝卵圆细胞中表达的意义%Expression and its significance of telomerase in rat hepatic oval cells

    Institute of Scientific and Technical Information of China (English)

    张伟; 陈孝平; 项帅; 张峰; 董汉华; 张磊; 陈琳; 张万广

    2009-01-01

    目的 检测大鼠肝卵圆细胞端粒酶活性,探讨端粒酶表达与卵圆细胞增殖分化的关系.方法 采用2-AAF/PH模型诱导大鼠卵圆细胞增殖,改良的胶原酶灌注结合密度梯度离心法分离,用细胞免疫荧光和电镜鉴定卵圆细胞.采用免疫组织化学、RT-PCR、荧光定量PCR等方法检测卵圆细胞端粒酶的表达,组间比较采用t检验分析其意义.结果 采用2-AAF/PH模型成功诱导大鼠卵圆细胞增殖.分离的卵圆细胞核大,卵圆形,胞质少,呈铺路石样生长.电镜发现细胞核质比大,胞质内细胞器少且发育不成熟.细胞免疫荧光结果表达OV-6、AFP、CK-19、albumin、c-kit.端粒酶逆转录酶(TERT)表达在门静脉周围增殖的卵圆细胞核内,随着卵圆细胞逐渐向肝细胞方向分化,TERT阳性细胞数逐渐减少.大鼠正常肝组织TERT mRNA表达水平最高,为LE-6卵圆细胞的2.27倍;分离的卵圆细胞TERT mRNA表达水平为LE.6卵圆细胞的1.26倍;采用2μg和4μg细胞提取物分析细胞的端粒酶活性,随着LE-6卵圆细胞传代次数的增加,由24代传至40代,端粒酶活性由△A=1.05、1.15降低到△A=0.25、0.45(t=17.74,12.38,P<0.05).结论 卵圆细胞具有端粒酶活性,端粒酶可能是卵圆细胞维持其增殖能力和多分化潜能的一个必要条件.%Objcctive To detect the telomerase activity in rat hepatic oval cells, and to explore the relationship between telomerase expression and the proliferation and differentiation of oval cells. Methods The 2-acetamidofluorene/partial bepatectomy (2-AAF/PH) rat model was used to induce the proliferation of oval cells. Oval cells were isolated by modified collagenase perfusion and gradient centrifugation. Electron microscope exami-nation and immunofluorescence were adopted to identify oval cells. Immunohistochemistry, RT-PCR and fluores-cence quantitative PCR were used to detect the expression of telomerase in oval cells. All the data collected were analyzed by

  5. Transformation and intensification of tornado-like flow in a narrow channel during elongation of an oval dimple with constant area

    Science.gov (United States)

    Isaev, S. A.; Leontiev, A. I.; Gul'tsova, M. E.; Popov, I. A.

    2015-06-01

    Reynolds averaged Navier-Stokes equations closed using the Menter shear-stress-transfer model have been numerically solved on multiblock intersecting structured grids of various scales. The obtained solution has been used to analyze the separated flow past an elongated oval dimple oriented at 45± on the wall of a narrow plane-parallel channel and to study transformation of the flow with increasing dimple aspect ratio at constant depth and spot area. It is established that, at a dimple width below one-third of the equivalent dimple diameter, intensification of the generated helical vortices observed when the transverse flow velocity exceeds 80% of the average mass flow velocity is accompanied by decrease in the level of hydraulic losses below that in an otherwise identical channel with an equivalent spherical dimple.

  6. Decipherment of the Inscription on the Duke Bin Xu Oval Container%(互巾火)公盨铭文考释

    Institute of Scientific and Technical Information of China (English)

    冯时

    2003-01-01

    A bronze vessel of the mid Western Zhou period, called Duke Bin xu oval container, has recently been brought into the collection of Beijing Baoli Museum of Art. It bears an inscription consisting of 98 characters in ten lines, which states Great Yu's regulation of rivers and watercourses and moral education in the Western Zhou period. The historical statements are mostly corresponding to textural records and suggest that ancient Chinese historiography became a considerable system in the mid Western Zhou Dynasty. They have important value to the study of the history of ancient China and the ideological history of the pre-Qin period. The present paper makes a decipherment of the inscription and a preliminary study of the problems it concerns.

  7. Heat transfer and pressure drop performances of twisted oval tubes%扭曲椭圆管管内传热与压降性能的研究

    Institute of Scientific and Technical Information of China (English)

    朱冬生; 谭祥辉; 曾力丁

    2013-01-01

    通过建立扭曲椭圆管单管传热与压降性能测试平台,利用光滑圆管,对测试平台测试结果的准确性进行了验证,同时对扭曲椭圆管的传热以及压降性能进行了实验测试,以测试结果为基础,验证了数值计算模型的准确性.对不同几何尺寸的扭曲椭圆管单管传热与压力性能进行了数值计算,分析了换热管几何参数对传热与压降性能的影响,结果显示:扭曲椭圆管传热性能随着扭曲椭圆管长短轴比A/B的增大而增大,随着扭曲椭圆管扭距S的减小而增大.同时以数值计算结果为基础,拟合得到了8×103< Re<4×104,11.49< S/dh<19.84,1.65 <A/B <3.11范围内的传热因子以及摩擦系数计算通用准则关系式.为扭曲椭圆管换热器在工程实际中的应用提供了数据基础.%An experimental system for testing the heat transfer and pressure drop performances of twisted oval tube was established,and its reliability was verified with a smooth round tube. Then,the heat transfer and pressure drop performances of a twisted oval tube were tested with the system. Based on the experimental result, the turbulent model and grid system for numerically studying the heat transfer and pressure drop performances of twisted tubes were confirmed. The performances of twisted oval tubes with different geometrical parameters were obtained numerically. The influences of geometrical parameters such as axis ratio A/B and twist pitch S on the performances of the tubes were also analyzed. The experimental result shows that the testing system and the data reduction method are reliable. The numerical result shows that the bigger the A/B is,the higher the heat transfer factor and friction factor are, the smaller the 5 is, and the higher the heat transfer factor and friction factor are. The correlations for calculating the heat transfer factor and friction coefficient in the range of 8 × 103 < Re < 4 × 104 ,11.49 < S/dh < 19.84,1.65

  8. Postoperative rescue closure of patent foramen ovale in the clinical setting of acute hypoxemic respiratory failure and stroke following coronary artery bypass surgery

    Directory of Open Access Journals (Sweden)

    José L Díaz-Gómez

    2015-01-01

    Full Text Available We describe a case of intraoperative diagnosis and successful deferred percutaneous closure of a patent foramen ovale (PFO in the clinical setting of acute refractory hypoxemic respiratory failure and new-onset ischemic stroke in an elderly patient after coronary artery bypass graft. Perioperative morbidity (i.e. severe hypoxemia, worsening right ventricular dysfunction, and embolic stroke that is potentially related to intraoperatively diagnosed PFO during cardiac surgery can complicate management in the Intensive Care Unit and perhaps affect the patient′s outcome. Although the PFO closure can be challenging in the clinical setting of hypoxemic respiratory failure and stroke following cardiac surgery, it can be a reasonable perioperative option.

  9. Research progress of twisted oval tube heat exchanger and its application%扭曲椭圆管换热器技术进展及其应用

    Institute of Scientific and Technical Information of China (English)

    谭祥辉; 朱冬生; 张立振; 曾力丁; 成取林

    2012-01-01

    The characteristics and heat transfer enhancement mechanism of twisted tube heat exchanger were introduced. The analysis of tube-side and shell-side flow field of the heat exchanger was summarized. The methods and conclusions of these studies were discussed. And from the view of designing and manufacturing, the correlations for calculating the heat transfer and pressure drop performances of the heat exchanger were presented. According to the current investigation progress, the cases about the application of twisted oval tube condenser in a chemical factory were introduced in the work. The result shows that the twisted oval tube condenser performs better than the traditional baffle heat exchanger,and it can be widely used in the field of chemical industry.%介绍了扭曲管换热器的结构特点、强化传热机理,总结了关于扭曲管换热器管程以及壳程流场的分析,同时介绍了相关分析方法和研究成果,同时从换热器设计制造的角度,对目前已有的扭曲管换热器管程、壳程传热计算公式进行了总结和分析,在扭曲椭圆管换热器目前研究状况的基础上,介绍了某厂采用扭曲椭圆管凝汽器的运行效果,结果表明:在一定情况下,扭曲管换热器的冷凝换热效果同样优于传统的折流板换热器,具有很好的推广应用前景.

  10. Activation of canonical Wnt signaling pathway promotes proliferation and self-renewal of rat hepatic oval cell line WB-F344 in vitro

    Institute of Scientific and Technical Information of China (English)

    Ying Zhang; Xin-Min Li; Fu-Kui Zhang; Bao-En Wang

    2008-01-01

    AIM:To investigate the effect of activation of canonical Wnt signaling pathway on the proliferation and differentiation of hepatic oval cells in vitro.METHODS:WB-F344 cells were treated with recombinant Wnt3a (20,40,80,160,200 ng/mL) in serum-free medium for 24 h.Cell proliferation was measured by Brdu incorporation analysis; untreated WB-F344 cells were taken as controls.After treatment with Wnt3a (160 ng/mL) for 24 h,subcellular localization and protein expression of β-catenin in WB-F344 cells treated and untreated with Wnt3a were examined by immunofluorescence staining and Western blot analysis.CyclinD1 mRNA expression was determined by semi-quantitative reverse-transcript polymerase chain reaction (RT-PCR).The mRNA levels of some phenotypic markers (AFP,CK-19,ALB) and two hepatic nuclear factors (HNF-4,HNF-d) were measured by RT-PCR.Expressions of CK-19 and AFP protein were detected by Western blot analysis.RESULTS:Wnt3a promoted proliferation of WB-F344 cells.Stimulation of WB-F344 cells with recombinant Wnt3a resulted in accumulation of the transcriptional activator β-catenin,together with its translocation into the nuclei,and up-regulated typical Wnt target gene CyclinD1.After 3 d of Wnt3a treatment in the absence of serum,WB-F344 cells retained their bipotential to express several specific phenotypic markers of hepatocytes and cholangiocytes,such as AFP and CK-19,following activation of the canonical Wnt signaling pathway.CONCLUSION:The canonical Wnt signaling pathway promotes proliferation and self-renewal of rat hepatic oval cells.

  11. Mobile 3 D Laser Scanning System in Shield Tunnel Segment Ovality Detection%移动式三维激光扫描系统在盾构隧道管片椭圆度检测中的应用

    Institute of Scientific and Technical Information of China (English)

    张华

    2015-01-01

    Several common methods of metro shield tunnel segment ovality detection are compared and basic princi -ples and internal and external workflow of Ovality detection based on mobile 3 D laser scanning system are analyzed by taking GRP5000 for example.The actual project shows that the ovality detection method based on mobile 3D laser scan-ning system has advantages in metro shield tunnel segment ovality detection .%介绍对比了几种常用的地铁盾构隧道管片椭圆度检测方法,并在此基础上以GRP5000系统为例分析了基于移动式三维激光扫描系统的椭圆度检测的基本原理及内外业工作流程。通过实际项目检验,表明基于移动式三维激光扫描系统的地铁盾构隧道管片椭圆度检测方法具有优势。

  12. Modeling of Mutiscale Electromagnetic Magnetosphere-Ionosphere Interactions near Discrete Auroral Arcs Observed by the MICA Sounding Rocket

    Science.gov (United States)

    Streltsov, A. V.; Lynch, K. A.; Fernandes, P. A.; Miceli, R.; Hampton, D. L.; Michell, R. G.; Samara, M.

    2012-12-01

    The MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) sounding rocket was launched from Poker Flat on February 19, 2012. The rocket was aimed into the system of discrete auroral arcs and during its flight it detected small-scale electromagnetic disturbances with characteristic features of dispersive Alfvén waves. We report results from numerical modeling of these observations. Our simulations are based on a two-fluid MHD model describing multi-scale interactions between magnetic field-aligned currents carried by shear Alfven waves and the ionosphere. The results from our simulations suggest that the small-scale electromagnetic structures measured by MICA indeed can be interpreted as dispersive Alfvén waves generated by the active ionospheric response (ionopspheric feedback instability) inside the large-scale downward magnetic field-aligned current interacting with the ionosphere.

  13. Intensification of dayside diffuse auroral precipitation: contribution of dayside Whistler-mode chorus waves in realistic magnetic fields

    Directory of Open Access Journals (Sweden)

    R. Shi

    2012-09-01

    Full Text Available Compared to the recently improved understanding of nightside diffuse aurora, the mechanism(s responsible for dayside diffuse aurora remains poorly understood. While dayside chorus has been thought as a potential major contributor to dayside diffuse auroral precipitation, quantitative analyses of the role of chorus wave scattering have not been carefully performed. In this study we investigate a dayside diffuse auroral intensification event observed by the Chinese Arctic Yellow River Station (YRS all-sky imagers (ASI on 7 January 2005 and capture a substantial increase in diffuse auroral intensity at the 557.7 nm wavelength that occurred over almost the entire ASI field-of-view near 09:24 UT, i.e., ~12:24 MLT. Computation of bounce-averaged resonant scattering rates by dayside chorus emissions using realistic magnetic field models demonstrates that dayside chorus scattering can produce intense precipitation losses of plasma sheet electrons on timescales of hours (even approaching the strong diffusion limit over a broad range of both energy and pitch angle, specifically, from ~1 keV to 50 keV with equatorial pitch angles from the loss cone to up to ~85° depending on electron energy. Subsequent estimate of loss cone filling index indicates that the loss cone can be substantially filled, due to dayside chorus driven pitch angle scattering, at a rate of ≥0.8 for electrons from ~500 eV to 50 keV that exactly covers the precipitating electrons for the excitation of green-line diffuse aurora. Estimate of electron precipitation flux at different energy levels, based on loss cone filling index profile and typical dayside electron distribution observed by THEMIS spacecraft under similar conditions, gives a total precipitation electron energy flux of the order of 0.1 erg cm−2 s−1 with ~1 keV characteristic energy (especially when using T01s, which can be very likely to cause intense green-line diffuse aurora activity on the

  14. On the formation and origin of substorm growth phase/onset auroral arcs inferred from conjugate space-ground observations

    Science.gov (United States)

    Motoba, T.; Ohtani, S.; Anderson, B. J.; Korth, H.; Mitchell, D. G.; Lanzerotti, L. J.; Shiokawa, K.; Connors, M. G.; Kletzing, C.; Reeves, G. D.

    2015-12-01

    Magnetotail processes and structures related to substorm growth phase/onset auroral arcs remain poorly understood mostly due to the lack of adequate observations. In this study we make a comparison between ground-based optical measurements of the premidnight growth phase/onset arcs at subauroral latitudes and magnetically conjugate measurements made by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) at ~780 km in altitude and by the Van Allen Probe-B spacecraft crossing L values of ~5.0-5.6 in the premidnight inner tail region. The conjugate observations offer a unique opportunity to examine the detailed features of the arc location relative to large-scale Birkeland currents and of the magnetospheric counterpart. The observations strongly suggest that the premidnight arc is connected to highly localized pressure gradients embedded in the near-tail R2 source region via a local upward FAC.

  15. 3D model of small-scale density cavities in the auroral magnetosphere with field-aligned current

    Science.gov (United States)

    Bespalov, P. A.; Misonova, V. G.; Savina, O. N.

    2016-09-01

    We propose a 3D model of small-scale density cavities stimulated by an auroral field-aligned current and an oscillating field-aligned current of kinetic Alfvén waves. It is shown that when the field-aligned current increases so that the electron drift velocity exceeds a value of the order of the electron thermal velocity, the plasma becomes unstable to the formation of cavities with low density and strong electric field. The condition of instability is associated with the value of the background magnetic field. In the case of a relatively weak magnetic field (where the electron gyro-radius is greater than the ion acoustic wavelength), the current instability can lead to the formation of one-dimensional cavities along the magnetic field. In the case of a stronger magnetic field (where the ion acoustic wavelength is greater than the electron gyro-radius, but still is less than the ion gyro-radius), the instability can lead to the formation of 3D density cavities. In this case, the spatial scales of the cavity, both along and across the background magnetic field, can be comparable, and at the earlier stage of the cavity formation they are of the order of the ion acoustic wavelength. Rarefactions of the cavity density are accompanied by an increase in the electric field and are limited by the pressure of bipolar electric fields that occur within them. The estimates of typical density cavity characteristics and the results of numerical solutions agree with known experimental data: small-scale structures with a sufficiently strong electric field are observed in the auroral regions with strong field-aligned current.

  16. Characteristics of solar wind control on Jovian UV auroral activity deciphered by long-term Hisaki EXCEED observations: Evidence of preconditioning of the magnetosphere?

    Science.gov (United States)

    Kita, Hajime; Kimura, Tomoki; Tao, Chihiro; Tsuchiya, Fuminori; Misawa, Hiroaki; Sakanoi, Takeshi; Kasaba, Yasumasa; Murakami, Go; Yoshioka, Kazuo; Yamazaki, Atsushi; Yoshikawa, Ichiro; Fujimoto, Masaki

    2016-07-01

    While the Jovian magnetosphere is known to have the internal source for its activity, it is reported to be under the influence of the solar wind as well. Here we report the statistical relationship between the total power of the Jovian ultraviolet aurora and the solar wind properties found from long-term monitoring by the spectrometer EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) on board the Hisaki satellite. Superposed epoch analysis indicates that auroral total power increases when an enhanced solar wind dynamic pressure hits the magnetosphere. Furthermore, the auroral total power shows a positive correlation with the duration of a quiescent interval of the solar wind that is present before a rise in the dynamic pressure, more than with the amplitude of dynamic pressure increase. These statistical characteristics define the next step to unveil the physical mechanism of the solar wind control on the Jovian magnetospheric dynamics.

  17. Plasma structure within poleward-moving cusp/cleft auroral transients: EISCAT Svalbard radar observations and an explanation in terms of large local time extent of events

    Directory of Open Access Journals (Sweden)

    M. Lockwood

    Full Text Available We report high-resolution observations of the southward-IMF cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter Svalbard radar (ESR, and compare them with observations of dayside auroral luminosity, as seen at a wavelength of 630 nm by a meridian scanning photometer at Ny Ålesund, and of plasma flows, as seen by the CUTLASS (co-operative UK twin location auroral sounding system Finland HF radar. The optical data reveal a series of poleward-moving transient red-line (630 nm enhancements, events that have been associated with bursts in the rate of magnetopause reconnection generating new open flux. The combined observations at this time have strong similarities to predictions of the effects of soft electron precipitation modulated by pulsed reconnection, as made by Davis and Lockwood (1996; however, the effects of rapid zonal flow in the ionosphere, caused by the magnetic curvature force on the newly opened field lines, are found to be a significant additional factor. In particular, it is shown how enhanced plasma loss rates induced by the rapid convection can explain two outstanding anomalies of the 630 nm transients, namely how minima in luminosity form between the poleward-moving events and how events can re-brighten as they move poleward. The observations show how cusp/cleft aurora and transient poleward-moving auroral forms appear in the ESR data and the conditions which cause enhanced 630 nm emission in the transients: they are an important first step in enabling the ESR to identify these features away from the winter solstice when supporting auroral observations are not available.

    Key words: Ionosphere (polar ionosphere - Magnetospheric physics (magnetopause; cusp and boundary layers; solar wind-magnetosphere interactions

  18. Bilateral thalamic stroke due to occlusion of the artery of Percheron in a patient with patent foramen ovale: a case report

    Directory of Open Access Journals (Sweden)

    López-Serna Raúl

    2009-09-01

    Full Text Available Abstract Introduction Bilateral thalamic infarcts are rare presentations of stroke. They are the result of a complex combination of risk factors and a predisposing vessel distribution. The artery of Percheron, characterized by a single arterial trunk that irrigates both paramedian thalamic regions, can be occluded as a result of embolic diseases leading to bilateral paramedian thalamic infarcts. Clinical and image findings of this uncommon form of posterior circulation infarct are presented along with their anatomic and pathophysiologic correlates. Case presentation A 27-year-old Mexican man with no relevant medical history was admitted to hospital after he was found deeply stuporous. On admission, an urgent neuroimaging protocol for stroke, including magnetic resonance imaging and magnetic resonance imaging angiography, was performed. The scans revealed symmetric bilateral hyperintense paramedian thalamic lesions consistent with acute ischemic events. The posterior circulation was patent including the tip of the basilar artery and both posterior cerebral arteries, making the case compatible with occlusion of the artery of Percheron. Further evaluation with an aim to define the etiology revealed a patent foramen ovale as the cause of embolism. Conclusion Bilateral thalamic infarcts are unusual presentations of posterior circulation stroke; once they are diagnosed by an adequate neuroimaging protocol, a further evaluation to define the cause is necessary. Cardioembolism should always be considered in relatively young patients. A complete evaluation should be conducted by an interdisciplinary team including neurologists, cardiologists and neurosurgeons.

  19. Safety and efficacy of device closure for patent foramen ovale for secondary prevention of neurological events: Comprehensive systematic review and meta-analysis of randomized controlled trials

    International Nuclear Information System (INIS)

    Background: Controversy persists regarding the management of patients with cryptogenic stroke and patent foramen ovale (PFO). We performed a meta-analysis of randomized controlled trials comparing PFO closure with medical therapy. Methods and Results: A prospective protocol was developed and registered using the following data sources: PubMed, Cochrane Register of Controlled Trials, conference proceedings, and Internet-based resources of clinical trials. Primary analyses were performed using the intention-to-treat method. Three randomized trials comparing percutaneous PFO closure vs. medical therapy for secondary prevention of embolic neurological events formed the data set. Baseline characteristics were similar. During long-term follow-up, the pooled incidence of the primary endpoint (composite of stroke, death, or fatal stroke) was 3.4% in the PFO closure arm and 4.8% in the medical therapy group [risk-reduction (RR) 0.7 (0.48–1.06); p = 0.09]. The incidence of recurrent neurological events (secondary endpoint) was 1.7% for PFO closure and 2.7% for medical therapy [RR 0.66 (0.35–1.24), p = 0.19]. There was no difference in terms of death or adverse events between the two groups. Conclusions: While this meta-analysis of randomized clinical trials demonstrated no statistical significance in comparison to medical therapy, there was a trend towards overall improvement in outcomes in the PFO closure group

  20. Síndrome platipnea-ortodeoxia por foramen oval permeable, aneurisma del septum interauricular y parálisis del hemidiafragma derecho Platypnea-orthodeoxia syndrome, atrial septal aneurysm and right hemidiaphragmatic elevation with a right-to-left shunt through a patent foramen ovale

    OpenAIRE

    Osvaldo D. López Gastón; Oscar Calnevaro; Claudio Gallego; Jorge Bluguermann; David Barbieri; Miguel Granja; Diego Mc Loughlin; Eduardo Malvino

    2005-01-01

    El síndrome platipnea-ortodeoxia (SPO) está caracterizado por disnea e hipoxemia en posición erecta que mejoran con el decúbito supino. Se presenta un paciente de 75 años sin antecedentes remarcables, con cuadro de disnea de 7 días de evolución. La radiografía y tomografía de tórax mostraron una elevación del hemidiafragma derecho (confirmándose su parálisis por radioscopia) sin alteraciones en el parénquima pulmonar y mediastino. El ecocardiograma contrastado evidenció un foramen oval permea...