Sample records for ionospheric plasma convection

  1. Hemispheric Effects in Ionospheric Plasma Convection and Irregularity Occurrence

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Baker, J. B. H.; Bristow, W. A.; Shepherd, S. G.; Kunduri, B.; Cousins, E. D. P.

    2014-12-01

    Extensive statistical studies have demonstrated the extent of asymmetries between the hemispheres in terms of the global pattern of plasma convection in the high-latitude ionosphere. However, relatively little is known about the asymmetries that arise on meso and smaller spatial scales or in the course of reconfiguration of the global convection following changes in IMF or substorm onsets. Moreover the correspondence between the hemispheres in space weather effects such as the occurrence of ionospheric plasma irregularities is almost unexplored. Some of the challenges in conducting such studies are traceable to more limited observational capabilities in the southern hemisphere. New capabilities have recently been achieved with the expansion of the SuperDARN radar network such that simultaneous and quasi-conjugate coverage is sometimes possible from midlatitudes to the polar cap. We review findings on the asymmetric aspects of high-latitude convection and press further to consider evidence of correspondence and asymmetry in convection when varying in time and across the equatorward auroral and midlatitude regions where conjugacy should obtain more reliably. We also discuss evidence of correlation between the hemispheres in terms of the occurrence of small-scale irregularities as a space weather phenomenon of practical importance.

  2. Strong interplanetary magnetic field By-related plasma convection in the ionosphere and cusp field-aligned currents under northward

    E-print Network

    California at Berkeley, University of

    Strong interplanetary magnetic field By-related plasma convection in the ionosphere and cusp field and the assimilative mapping of ionospheric electrodynamics (AMIE) model during a prolonged interval with large procedure provides a reasonably good description of plasma circulations in the ionosphere during

  3. New SuperDARN Radar Capabilities for Observing Ionospheric Plasma Convection and ITM Coupling in the Mid-Latitude Ionosphere

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Baker, J. B.; Greenwald, R. A.; Clausen, L. B.; Shepherd, S. G.; Bristow, W. A.; Talaat, E. R.; Barnes, R. J.

    2010-12-01

    Within the past year the first pair of SuperDARN radars funded under the NSF MSI program has become operational at a site near Hays, Kansas. The fields of view of the co-located radars are oriented to provide common-volume observations with two existing radars in Virginia (Wallops, Blackstone) and two MSI radars under construction in Oregon (Christmas Valley). The emerging mid-latitude radar chain will complement the existing SuperDARN coverage at polar cap and auroral latitudes within North America. The mid-latitude radars observe the expansion of auroral effects during disturbed periods, subauroral polarization streams, and small-scale ionospheric irregularities on the nightside that open a window on the plasma drifts and electric fields of the quiet-time subauroral ionosphere. They also measure neutral winds at mesospheric heights and the propagation of ionospheric disturbances due to the passage of atmospheric gravity waves. The new radar capabilities provide unprecedented views of ITM processes in the subauroral ionosphere with applications to studies of ionospheric electric fields, ion-neutral coupling, atmospheric tides and planetary waves, ionospheric plasma structuring and plasma instability. In this talk we describe the new capabilities and the potential for providing large-scale context for related ITM measurements over North America. We present the first high-resolution two-dimensional maps of ionospheric plasma convection at mid-latitudes as generated from common-volume observations with the Hays and Blackstone radars.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  5. Ionospheric convection associated with discrete levels of particle precipitation

    Microsoft Academic Search

    J. C. Foster; J.M. Holt; R. G. Musgrove; D. S. Evans

    1986-01-01

    A precipitation index is described which quantifies the intensity and spatial extent of high-latitude particle precipitation based on observations made along individual satellite passes. By sorting plasma-convection data according to this index, average patterns of the ionospheric convection electric field were derived from a data set consisting of five years' observations by the Millstone Hill radar. Reference to the instantaneous

  6. Convective cell generation by kinetic Alfven wave turbulence in the auroral ionosphere

    SciTech Connect

    Zhao, J. S.; Wu, D. J. [Purple Mountain Observatory, Chinese Academy of Sciences 210008, Nanjing (China); Yu, M. Y. [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Institute for Theoretical Physics I, Ruhr University, D-44780 Bochum (Germany); Lu, J. Y. [National Center for Space Weather, China Meteorology Administration 100081, Beijing (China)

    2012-06-15

    Modulation of convective cells by kinetic Alfven wave (KAW) turbulence is investigated. The interaction is governed by a nonlinear dispersion relation for the convective cells. It is shown that KAW turbulence is disrupted by excitation of the large-scale convective motion through a resonant instability. Application of the results to the auroral ionosphere shows that cross-scale coupling of the KAW turbulence and convective cells plays an important role in the evolution of ionospheric plasma turbulence.

  7. Ionospheric convection patterns observed during periods of steady magnetospheric convection

    NASA Astrophysics Data System (ADS)

    Hughes, J. M.; Bristow, W. A.

    2002-12-01

    We present a study of ionospheric convection patterns observed by the Super Dual Auroral Radar Network (SuperDARN) during two recent steady magnetospheric convection (SMC) events. Our analyses foucus on the region near the Harang discontinuity (HD) and show, in contrast to prevous SMC studies, that the HD is not an uncommon feature during SMC events. Although often observed during these events, the HD appears less extended than during a typical substorm growth phase and often forms at relatively high geomagnetic latitudes.

  8. SuperDARN observations of ionospheric convection and magnetospheric reconnection

    NASA Astrophysics Data System (ADS)

    Watanabe, Masakazu

    It is well known that the major driver of ionospheric convection is a sequence of reconnection in the magnetosphere that starts between the interplanetary magnetic field (IMF) and the geomagnetic field. One goal of the Super Dual Auroral Radar Network (SuperDARN) project is to assess the reconnection processes remotely from the measured global convection pattern. If one knows all the modes of reconnection that can occur in the magnetosphere and their ionospheric consequences, one can inversely determine the modes of reconnection from the observed ionospheric convection pattern. For this purpose, we have developed a catalogue of reconnection modes that can occur under steady-state IMF conditions and modeled the plasma flow that each reconnection mode stimulates in the ionosphere. This reconnection catalogue is applicable to any orientation of the IMF except when the IMF is parallel to the Earth's dipole axis. In general, there are sixteen types of reconnection. Usually, for given IMF conditions, only eight types occur, depending on the orientation of the IMF. In this presentation we show the modeling results and SuperDARN observations for the cases (1) when the dawn-dusk component of the IMF is dominant and (2) when the IMF is due northward but with significant dipole tilt. For each case, comparison of model predictions with observations shows good agreement. This study revealed some unfamiliar convection patterns that have caught but little attention of researchers. They include "exchange" cells and "split" crescent cells for IMF BY -dominated periods, and winter hemisphere "reciprocal" cells for due northward IMF with significant dipole tilt. In the presentation we focus on such convection patterns that are relatively new to the space science community.

  9. Ionospheric plasma cloud dynamics

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Measurements of the thermospheric neutral wind and ionospheric drift made at Eglin AFB, Florida and Kwajalein Atoll are discussed. The neutral wind measurements at Eglin had little variation over a period of four years for moderate magnetic activity (Kp 4); the ionospheric drifts are small. Evidence is presented that indicates that increased magnetic activity has a significant effect on the neutral wind magnitude and direction at this midlatitude station. The neutral wind at dusk near the equator is generally small although in one case out of seven it was significantly larger. It is described how observations of large barium releases can be used to infer the degree of electrodynamic coupling of ion clouds to the background ionosphere. Evidence is presented that indicates that large barium releases are coupled to the conjugate ionosphere at midlatitudes.

  10. Convection surrounding mesoscale ionospheric flow channels

    NASA Astrophysics Data System (ADS)

    Rinne, Y.; Moen, J.; Baker, J. B. H.; Carlson, H. C.

    2011-05-01

    We evaluate data from the European Incoherent Scatter (EISCAT) Svalbard radar (ESR) and Defense Meteorological Satellite Program (DMSP) spacecraft coupled with data from the Super Dual Auroral Radar Network (SuperDARN) polar cap convection patterns in order to study how the ionospheric convection evolves around a sequence of transient, mesoscale flow channel events in the duskside of the cusp inflow region. On a northwestward convection background for the interplanetary magnetic field (IMF) BY positive and BZ negative, a sequence of three eastward flow channels formed over the course of 1 hour in response to three sharp IMF rotations to IMF BY negative and IMF BZ positive. The first and third channels, due to IMF BY negative periods of ˜13 min and >30 min, respectively, develop in a similar manner: they span the entire ESR field of view and widen poleward with increasing time elapsed since their first appearance until the IMF rotates back. The convection patterns are consistent with the line-of-sight data from the ESR and DMSP within a 10 min adaption time. The flow lines form a twin-vortex flow, with the observed channel being the twin vortices' center flow. The fitting algorithm was pushed to its limits in terms of spatial resolution in this study. During portions of the channel events, the suggested twin-cell flow is not in agreement with our physical interpretation of the flow channels being reconnection events because cell closure is suggested across an anticipated nonreconnecting open-closed boundary. For these segments, we present simulated patterns which have been arrived at by a combination of looking at the raw data and examining the fitted convection patterns.

  11. Model of the high-latitude ionospheric convection pattern

    Microsoft Academic Search

    R. A. Heelis; J. K. Lowell; R. W. Spiro

    1982-01-01

    Mathematical expressions have been constructed that allow the large-scale global convection characteristics of the high-latitude ionosphere to be reproduced. The model contains no discontinuities in the ion convection velocity and as such should be useful in F region chemical models. The number of variables in the model allow such features as the dayside throat and the Harang discontinuity to be

  12. Plasma Temperatures in the Ionosphere of Saturn

    Microsoft Academic Search

    Luke Moore; M. Galand; M. Mendillo; I. Müller-Wodarg

    2007-01-01

    Using a one-dimensional version of the Saturn Thermosphere Ionosphere Model (STIM), we perform calculations of the ion and electron temperatures in the ionosphere of Saturn. There are no direct measurements of plasma temperatures in Saturn's atmosphere published to date, but they are often estimated from the topside plasma scale heights of radio occultation measurements of electron density. Based on Pioneer,

  13. Formation of magnetospheric plasma population regimes coupled with the dynamo process in the convection system

    Microsoft Academic Search

    T. Tanaka

    2003-01-01

    Based on the magnetosphere-ionosphere (M-I) coupling scheme, convection as a compound system is considered including the generation of plasma population regimes in the magnetosphere. In these considerations, primary elements that must be set to a self-consistent configuration are convection flows in the magnetosphere and the ionosphere, field-aligned current (FAC) systems, ionospheric currents, energy conversion processes, and plasma population regimes. The

  14. Ionospheric anomalous disturbance during the tropospheric strong convective weather

    NASA Astrophysics Data System (ADS)

    Cang, Zhongya; Cheng, Guangguang; Cheng, Guosheng

    2015-07-01

    Based on TBB data from Chinese FY-2 geostationary satellite, NCEP Reanalysis data and GPS-TEC data provided by IGS, by using sliding mean method, ionospheric anomalous disturbance during a typical convective weather was investigated. Results show that this severe convective weather was caused by a high-altitude cold eddy and a strong squall line. The ionospheric total electron content increased abnormally when convection occurred. The maximum increase of tested point was more than 6 TECU mainly at 8-12 UT of the day, and the peak time of the day lagged about 2 h than usual. Ionospheric anomalous region reached about 20 longitudes and 10 latitudes, and anomalous center was on the west side of the convective cloud, which may be related to the topographic effect of the Tibetan Plateau. Series of Case Studies further determine that convective weather can influence the ionospheric state. Furthermore, tropospheric vertical velocity was also analyzed to discuss the possible mechanisms of troposphere-ionosphere coupling.

  15. Ionospheric Conductance During Substorms and Steady Magnetospheric Convection Events (SMCs)

    NASA Astrophysics Data System (ADS)

    DeJong, A. D.; Ridley, A. J.; Bell, J. M.

    2014-12-01

    We will investigate the differences in ionospheric conductance derived from empirical models and simulated by self-consistent ionosphere-thermosphere models, during both substorms and steady magnetospheric convection events. The Global Ionosphere-Thermosphere Model (GITM) will self-consistently calculate the integrated electron content and ionospheric conductance using different energy deposition models and data--such as Ovation, AMIE, and auroral images. We will calculate the average auroral energy deposition and auroral energy flux, using images from the ultraviolet imager (UVI) onboard the Polar spacecraft. From these images, we will use the Robinson empirical formula to calculate the conductance during these different events. We will investigate the similarities and differences in the ionospheric conductance derived from the different methods and derived different event types.

  16. Radar Observations of Interhemispheric Ionospheric Convection Morphology Associated with Magnetotail Dynamics

    NASA Astrophysics Data System (ADS)

    Grocott, A.

    2014-12-01

    We discuss radar observations of the high-latitude ionospheric convection, in both the northern and southern hemispheres, in terms of the interplanetary magnetic field (IMF) orientation, prevailing geomagnetic conditions, and their associated timescales. Plasma velocity measurements, obtained by the Super Dual Auroral Radar Network (SuperDARN), have been used to derive patterns of the ionospheric electric potential in which interhemispheric asymmetries in the associated large-scale convection morphology are identified. In addition to the expected IMF BY-related asymmetries between the dusk and dawn convection cells, which tend to display the opposite sense in the two hemispheres, we find asymmetries related to magnetotail dynamics that exhibit a more complex behaviour. We attribute this to differences in the timescales required for the development of IMF-related asymmetries, and those associated with internal magnetospheric processes. We consider how the interplay between the magnetospheric regions involved determines the overall morphology of the system.

  17. Role of Ionospheric Plasmas in Earth's Magnetotail

    NASA Technical Reports Server (NTRS)

    Moore, Thomas E.

    2007-01-01

    This tutorial will summarize observations and theories indicating a prominent role of ionospheric plasma in the Earth's magnetotail. At the Global scale, I will argue that it is ionospheric plasma momentum and dynamic pressure that are responsible for the production of plasmoids, through the action of a transient near-Earth neutral or X-line, which serves to release excessive plasma pressure from the magnetotail field. Ionospheric plasma gains the momentum and energy to produce plasmoids and their related effects through its interaction with the solar wind, beginning at the dayside reconnection region and extending across the polar caps through the magnetotail lobes. This distant neutral line can be depicted as a feature much like that found in cometary magnetospheres, where disconnection limits the amount of IMF hung up on the cometary coma. On the other hand, the near-Earth neutral one can be seen as a feature unique to planets with an intrinsic magnetic field and internal source of plasma, the heating of which produces pressures too large to be restrained. Ionospheric plasmas also have other more local roles to play in the magnetotail. The circulation influences the composition of the plasma sheet, and the resultant wave environment, giving rise to reduced wave propagation speeds. Important heavy ion cyclotron resonances, and enhanced finite gyro-radius effects including non-adiabatic particle acceleration. At minimum, the presence of ionospheric plasma must influence the rate of reconnection via its enhanced mass density. Other non-MHD effects of ionospheric plasma presence are likely to be important but need much more investigation to be well understood. The MMS mission is designed to penetrate the subtle diffusion region physics that is involved, and its ability to observe ionospheric plasma involvement in reconnection will contribute significantly toward that goal.

  18. Plasma jet effects on the ionospheric plasma

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Arnoldy, R. L.; Cahill, L. J.; Kintner, P. M.

    1983-01-01

    Heavy ion beams were injected into the ionospheric plasma (experiments ARCS 1 and ARCS 2). In ARCS 1, operation of a 25eV argon ion source, mounted on a plasma diagnostic payload, produced an accelerated electron population; broadband electric field turbulence; large, spin synchronized electric field perturbations; and depletions of thermal ions. In ARCS 2, the ion source was deployed upward along the local magnetic field direction away from the diagnostic payload, and observed effects are contained within several meters of the ion source. However, enhanced wave levels near the LHR frequency are observed at distances up to 1 km, as are the injected ions themselves. A measurement of the dominant wavelength of the enhanced waves is consistent with an inference based upon the accelerated electron population seen in ARCS 1. This electron population is not evident during ARCS 2.

  19. The ionospheric signature of transient dayside reconnection and the associated pulsed convection return ow

    E-print Network

    Boyer, Edmond

    The ionospheric signature of transient dayside reconnection and the associated pulsed convection to investigate the excitation of convection in the dayside high-latitude ionosphere in response to transient-propagating backscatter features at the expected location of the ionospheric footprint of the cusp region, which have

  20. Plasma Waves in an Inhomogeneous Ionosphere Carl Caleman

    E-print Network

    Plasma Waves in an Inhomogeneous Ionosphere Carl Caleman 8th April 2003 #12;Abstract The inhomogeneity of space plasma is the cause of interesting physical phenomena. The plasma in our ionosphere waves reaches the ionosphere, interacts with the local plasma there, and are reflected back again one

  1. Plasma conductivity for Comet Halley ionosphere

    NASA Astrophysics Data System (ADS)

    Buti, B.; Eviatar, A.

    1989-01-01

    Observational as well as semitheoretical magnetic field profiles have been used to derive self-consistently the plasma conductivity profiles for the ionosphere of Comet Halley. The characteristic diffusion length for the field, according to the present model, is about 28 km; this is in very good agreement with the Giotto spacecraft observations. It is shown that ideal MHD as well as constant conductivity models are not appropriate for the study of dynamical structure of the Halley's ionosphere.

  2. The ionospheres and plasma tails of comets

    NASA Technical Reports Server (NTRS)

    Mendis, D. A.; Ip, W.-H.

    1977-01-01

    The paper reviews the current state of knowledge about cometary plasma (type I) tails and ionospheres. Observational statistics for type I tails are examined along with spectroscopic observations of plasma tails, identified ion species in such tails, and the morphology of cometary plasma tails and ionospheres. Evidence for a strong interaction between comets and the solar wind is evaluated on the basis of observations of plasma-tail orientations, large accelerations of tail structures, and correlations between disturbances in type I tails and solar-wind or geomagnetic disturbances. The use of comets as solar-wind probes is discussed, the nature of comet-solar-wind interactions is investigated, and ionization sources for cometary gases are considered. Hydrodynamic models of comet-solar-wind interaction are summarized, and the structure and ion chemistry of cometary ionospheres are studied. Observations suggesting that significant magnetic fields are associated with comets are briefly reviewed and interpreted.

  3. Model of the high-latitude ionospheric convection pattern

    SciTech Connect

    Heelis, R.A.; Lowell, J.K.; Spiro, R.W.

    1982-08-01

    Mathematical expressions have been constructed that allow the large-scale global convection characteristics of the high-latitude ionosphere to be reproduced. The model contains no discontinuities in the ion convection velocity and as such should be useful in F region chemical models. The number of variables in the model allow such features as the dayside throat and the Harang discontinuity to be modeled. The applicability of the model to magnetospheric physics is limited by the exclusion of large-magnitude small-scale flow features associated with discrete arcs and by the inability of the model to produce separate flow cells at the same local time.

  4. A model of the high-latitude ionospheric convection pattern

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.; Lowell, J. K.; Spiro, R. W.

    1982-01-01

    Mathematical expressions have been constructed that allow the large-scale global convection characteristics of the high-latitude ionosphere to be reproduced. The model contains no discontinuities in the ion convection velocity and as such should be useful in F region chemical models. The number of variables in the model allow such features as the dayside throat and the Harang discontinuity to be modeled. The applicability of the model to magnetospheric physics is limited by the exclusion of large-magnitude small-scale flow features associated with discrete arcs and by the inability of the model to produce separate flow cells at the same local time.

  5. Formation of Striations in Ionospheric Plasma Clouds

    Microsoft Academic Search

    Lewis M. Linson; Joseph B. Workman

    1970-01-01

    It is suggested that a low-frequency 'gradient drift' instability may be important for the formation of striations in barium ion clouds released in the ionosphere above the E layer. The theory predicts that the trailing edge (with respect to the neutrals) of the plasma cloud will be unstable while the leading edge is stable, in qualitative agreement with observations. The

  6. Interhemispheric asymmetry of the high-latitude ionospheric convection pattern

    NASA Technical Reports Server (NTRS)

    Lu, G.; Richmond, A. D.; Emery, B. A.; Reiff, P. H.; Beaujardiere, O. De LA; Rich, F. J.; Denig, W. F.; Kroehl, H. W.; Lyons, L. R.; Ruohoiemi, J. M.

    1994-01-01

    The assimilative mapping of ionospheric electrodynamics technique has been used to derive the large-scale high-latitude ionospheric convection patterns simultaneously in both northern and southern hemispheres during the period of January 27 to 29, 1992. When the interplanetary magnetic field (IMF) B(sub z) component is negative, the convection patterns in the southern hemisphere are basically the mirror images of those in the northern hemisphere. The total cross-polar cap potential drops in the two hemispheres are similar. When B(sub z) is positive and absolute value of B(sub y) greater than B(sub z), the convection configurations are mainly determined by B(sub y) and they may appear as normal 'two-cell' patterns in both hemispheres much as one would expect under southward IMF conditions. However, there is a significant difference in the cross-polar-cap potential drop between the two hemispheres, with the potential drop in the southern (summer) hemisphere over 50% larger than that in the northern (winter) hemisphere. As the ratio of absolute value of B(sub y)/B(sub z) decreases (less than one), the convection configuration in the two hemispheres may be significantly different, with reverse convection in the southern hemisphere and weak but disturbed convection in the northern hemisphere. By comparing the convection patterns with the corresponding spectrograms of precipitating particles, we interpret the convection patterns in terms of the concept of merging cells, lobe cells, and viscous cells. Estimates of the ' merging cell' potential drops, that is, the potential ascribed to the opening of the dayside field lines, are usually comparable between the two hemispheres, as they should be. The 'lobe cell' provides a potential between 8.5 and 26 kV and can differ greatly between hemispheres, as predicted. Lobe cells can be significant even for southward IMF, if absolute value of B(sub y) greater than the absolute value of B(sub z). To estimate the potential drop of the 'viscous cells,' we assume that the low-latitude boundary layer is on closed field lines. We find that this potential drop varies from case to case, with a typical value of 10 kV. If the source of these cells is truly a viscous interaction at the flank of the magnetopause, the process is likely spatially and temporally varying rather than steady state.

  7. The magnetosphere ionosphere system from the perspective of plasma circulation: A tutorial

    NASA Astrophysics Data System (ADS)

    Lotko, W.

    2007-03-01

    This tutorial review examines the role of O+ in the dynamics of magnetosphere ionosphere coupling. The life cycle of an O+ plasma element is considered as it circulates from the mid- to high-latitude ionosphere. Energization and diversion of the convecting plasma element into outflows involves Alfvénic turbulence at the low-altitude base of the cusp and plasmasheet boundary layer and in downward-current “pressure cookers.” Observational evidence indicating that O+ dominates the plasmasheet and ring current during extreme storm intervals is reviewed. The impacts of an O+-enriched plasma on solar wind magnetosphere ionosphere coupling are considered at both the micro and global scales. A synthesis of results from observation, theory and simulations suggests that the presence of O+ in the magnetosphere is both a disruptive and a moderating agent in maintaining the balance between dayside and nightside magnetic merging.

  8. Explosive plasma releases in the earth's ionosphere

    NASA Technical Reports Server (NTRS)

    Kintner, P. M.

    1982-01-01

    The Trigger and Buaro experiments and the University of Alaska's radial shaped charge experiment, which were conducted to actively probe the ionosphere with expanding plasmas are described. Emphasis is on the Trigger experiment, which has a Cs release with spherical geometry. Transient events occurring after Cs detonation include the production of a 200 mV/m electric field pulse, and the precipitation of energetic electrons. Future applications are also discussed, and include in situ measurements of the radial shaped experiment from a mother-daughter payload.

  9. Theory of convective saturation of Langmuir waves during ionospheric modification of a barium cloud

    NASA Astrophysics Data System (ADS)

    Goldman, M. V.; Newman, D. L.; Drake, R. Paul; Afeyan, Bedros B.

    1997-12-01

    In recent experiments (Djuth, F. T., Sulzer, M. P., Elder, J. H. and Groves, K. M. (1995) Journal of Geophysical Research, 100, 17,347), a parametric decay instability was excited by an ordinary-wave HF pump during an ionospheric chemical release from a rocket over Arecibo, PR, which created an artificial `barium ionosphere,' with peak plasma frequency above the pump frequency, and a density gradient with a (short) 5 km scale length. Simultaneous incoherent scattering measurements revealed a strong initial asymmetry in the amplitudes of almost vertically upgoing versus downgoing measured plasma waves. We can account for this asymmetry in terms of linear convective saturation of parametrically unstable plasma waves propagating over a range of altitudes along geometric optics ray paths. Qualitative features of the frequency spectrum of the measured downgoing wave are in agreement with this model, although the theoretically predicted spectrum is narrower than observed. The observed altitude localization of the enhanced spectrum to a few range cells is consistent with the theory.

  10. Interplanetary magnetic field effects on high latitude ionospheric convection

    NASA Technical Reports Server (NTRS)

    Heelis, R. A.

    1985-01-01

    Relations between the electric field and the electric current in the ionosphere can be established on the basis of a system of mathematical and physical equations provided by the equations of current continuity and Ohm's law. For this reason, much of the synthesis of electric field and plasma velocity data in the F-region is made with the aid of similar data sets derived from field-aligned current and horizontal current measurements. During the past decade, the development of a self-consistent picture of the distribution and behavior of these measurements has proceeded almost in parallel. The present paper is concerned with the picture as it applies to the electric field and plasma drift velocity and its dependence on the interplanetary magnetic field. Attention is given to the southward interplanetary magnetic field and the northward interplanetary magnetic field.

  11. Interaction of the Saturnian Magnetospheric Plasma with Titan's Ionosphere: Formation of a Ionopause

    Microsoft Academic Search

    H. Backes; F. M. Neubauer

    2001-01-01

    The interaction of Titan with the ambient plasma has many faces since the determining parameters (ionospheric composition and ambient plasma properties) vary substantially in time. The main ionization source for Titan's ionosphere is the solar EUV radiation. Thus, the nightside ionosphere differs completely from the dayside ionosphere. The magnetospheric plasma in the plasma mantle is highly variable in time. Apart

  12. Characteristics of ionospheric convection and field-aligned current in the dayside cusp region

    NASA Technical Reports Server (NTRS)

    Lu, G.; Lyons, L. R.; Reiff, P. H.; Denig, W. F.; Beaujardiere, O. De LA; Kroehl, H. W.; Newell, P. T.; Rich, F. J.; Opgenoorth, H.; Persson, M. A. L.

    1995-01-01

    The assimilative mapping of ionospheric electrodynamics (AMIE) technique has been used to estimate global distributions of high-latitude ionospheric convection and field-aligned current by combining data obtained nearly simultaneously both from ground and from space. Therefore, unlike the statistical patterns, the 'snapshot' distributions derived by AMIE allow us to examine in more detail the distinctions between field-aligned current systems associated with separate magnetospheric processes, especially in the dayside cusp region. By comparing the field-aligned current and ionospheric convection patterns with the corresponding spectrograms of precipitating particles, the following signatures have been identified: (1) For the three cases studied, which all had an IMF with negative y and z components, the cusp precipitation was encountered by the DMSP satellites in the postnoon sector in the northern hemisphere and in the prenoon sector in the southern hemisphere. The equatorward part of the cusp in both hemispheres is in the sunward flow region and marks the beginning of the flow rotation from sunward to antisunward. (2) The pair of field-aligned currents near local noon, i.e., the cusp/mantle currents, are coincident with the cusp or mantle particle precipitation. In distinction, the field-aligned currents on the dawnside and duskside, i.e., the normal region 1 currents, are usually associated with the plasma sheet particle precipitation. Thus the cusp/mantle currents are generated on open field lines and the region 1 currents mainly on closed field lines. (3) Topologically, the cusp/mantle currents appear as an expansion of the region 1 currents from the dawnside and duskside and they overlap near local noon. When B(sub y) is negative, in the northern hemisphere the downward field-aligned current is located poleward of the upward current; whereas in the southern hemisphere the upward current is located poleward of the downward current. (4) Under the assumption of quasi-steady state reconnection, the location of the separatrix in the ionosphere is estimated and the reconnection velocity is calculated to be between 400 and 550 m/s. The dayside separatrix lies equatorward of the dayside convection throat in the two cases examined.

  13. Ionospheric physics

    SciTech Connect

    Sojka, J.J. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

    1991-01-01

    Advances in all areas of ionospheric research are reviewed for the 1987-1990 time period. Consideration is given to the equatorial ionosphere, the midlatitude ionosphere and plasmasphere, the auroral ionosphere, the polar ionosphere and polar wind, ionospheric electrodynamic inputs, plasma waves and irregularities, active experiments, ionospheric forecasting, and coupling the ionosphere with other regions.

  14. Intense spreading of radar echoes from ionospheric plasmas

    E-print Network

    Dorfman, Seth E

    2005-01-01

    On December 25, 2004, a large-scale ionospheric plasma bubble was observed over Arecibo Observatory in Puerto Rico, inducing significant range spreading on ionograms. This phenomena may be explained by means of the E x B ...

  15. Rocket vehicle targeting for the PLACES ionospheric plasma test series

    NASA Astrophysics Data System (ADS)

    Rollstin, L. R.

    1984-02-01

    The PLACES (Position Location And Communication Effects Simulations) test program, conducted in December 1980 at Eglin Gulf Test Range, involved a series of ionospheric releases of barium/barium-nitrate vapor. The Defense Nuclear Agency sponsored program investigated effects of a structured ionospheric plasma (similar to that produced by a high-altitude nuclear explosion) on satellite navigation systems and provided in situ measurement of plasma structure. Terrier-Tomahawk rocket systems boosted the barium payloads, beacon payloads (plasma occultation experiment), and probe payloads (plasma in situ measurement). Drifting plasma tracking procedures, beacon- and probe-vehicle targeting procedures, and vehicle flight test results are presented.

  16. Post substorm convection and auroral arc currents determined from multiple ionospheric, magnetic, and electric field observations

    SciTech Connect

    Walker, J.K.; Koehler, J.A.; Creutzberg, F.; McNamara, A.G.; Jones, A.V.; Whalen, B.A.

    1981-11-01

    Field, particle, and optical observations from rocket-borne probes, magnetic data from a meridian chain of stations, and data from three scanning photometers were used for analyses of auroral current systems during the recovery phase of a substorm. The rockets were launced southeastward over several discrete arcs from Ft. Churchill, Canada, in January 15, 1972. Current models were determined independently from the magnetic field observations and from the electric field and ionospheric observations. The electric fields were measured by a rocket-borne electrostatic analyzer while the ionospheric model was determined from plasma probe measurements and also calculated from the energetic particle observations. Broad westward current systems were encountered on the initial and final segments of the trajectory and were determined from Ohm's law and compared with those calculated from magnetic observations obtained along the rocket trajectory and from the meridian chain of stations. Auroral arc currents under the apogee segment of the trajectory were calculated from the electric field observations and a model ionosphere and were eastward. Field-aligned currents were estimated from the divergence of the meridian current and added to these electrojets. The model was iterated to obtain a reasonable fit to both the ground-based and the rocket-borne observations. A very active region poleward of the arcs was much more structured than that indicated from the analysis of the ground-based magnetic data. It consisted of both eastward and westward currents, which may have been remnants of the substorm. Intense field-aligned currents flowed inward on the poleward edge of the electrojets and outward near the arcs, at the Harange discontinuity, and between the electrojets. These field-aligned currents appeared to be located at the boundaries of cells that contained the convection, active remnant region, and auroral arc current systems.

  17. Evolution of Ionospheric Convection during a Double Transpolar Arc Phenomenon on February 11, 1999

    NASA Technical Reports Server (NTRS)

    Narita, Y.; Maezawa, K.; Spann, J. F.; Parks, G. K.; Marklund, G. T.; Kullen, A.; Ivchenko, N.; Greenwald, R. A.; Sato, N.; Yamagishi, H.; Six, N. Frank (Technical Monitor)

    2002-01-01

    An evolution of ionospheric convection was studied for a double transpolar arc phenomenon on February 11, 1999. While one transpolar arc split from the auroral oval in the morning sector and drifted duskward, another arc appeared in the evening sector. The convection was investigated with three velocity data sets: E B drift velocities from the ASTRID-2 satellite; Ion Driftmeter data from the DMSP satellites; and Doppler-shift data from the Super-DARN radars. We inferred convection cells from these data sets and found that the number of convection cells changed from three to four as the dominance of IMF changed from a negative By to a positive Bz. Our result suggests that the ionospheric convection that has been so far discussed for various conditions of IMF may be applied even to the cases accompanied by transpolar arcs.

  18. Plasma temperatures in Saturn's ionosphere Luke Moore,1

    E-print Network

    Mendillo, Michael

    Plasma temperatures in Saturn's ionosphere Luke Moore,1 Marina Galand,2 Ingo Mueller-Wodarg,2 Roger the height of peak electron density, while they can reach 500 K during the day at the topside. Plasma scale of Saturn have been used to estimate plasma temperature as a comparison. Such an estimate agrees well

  19. On the control of magnetospheric convection by the spatial distribution of ionospheric conductivities

    Microsoft Academic Search

    Catherine Senior; Michel Blanc

    1984-01-01

    Using the linear approximation of the motions of the magnetospheric ring current inner edge, a self-consistent, semianalytical model is developed of its coupling to the ionosphere via field-aligned currents, its reaction to an externally imposed dawn-to-dusk potential drop across the magnetospheric cavity, and its effect on the shielding of convection electric field from midlatitudes. The spatial distribution of ionospheric conductivities

  20. Plasma turbulence in the equatorial ionospheric F region

    Microsoft Academic Search

    Rickey Dale McDaniel

    1998-01-01

    Equatorial spread F is a spectacular phenomenon in which the equatorial region ionosphere is reshaped after sunset. The plasma instabilities responsible for equatorial spread F are fascinating since they occur on time scales ranging from seconds to hours and length scales from centimeters to tens of kilometers. The plasma irregularities that occur in the F region also influence the performance

  1. Ionospheric Plasma Bubbles observed at 29 degree south

    Microsoft Academic Search

    H. O. Goulart; E. A. Grellmann; C. M. Wrasse; K. Makita; H. Takahashi; N. J. Schuch

    2006-01-01

    Ionospheric plasma bubbles have been observed by airglow OI6300 imaging technique at the Southern Space Observatory San Martino da Serra 29 S 54 W Brazil since 2004 The bubbles plasma depletion along the magnetic field line are frequently observed in a period from September to March during the southern spring equinox to autumn equinox seasons The frequency of occurrence avarege

  2. Superposed epoch analysis of the ionospheric convection evolution during substorms: IMF BY dependence

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Milan, S. E.; Yeoman, T. K.; Sato, N.; Yukimatu, A. S.; Wild, J. A.

    2010-10-01

    We present superposed epoch analyses of the average ionospheric convection response in the northern and southern hemispheres to magnetospheric substorms occurring under different orientations of the interplanetary magnetic field (IMF). Observations of the ionospheric convection were provided by the Super Dual Auroral Radar Network (SuperDARN) and substorms were identified using the Far Ultraviolet (FUV) instrument on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft. We find that during the substorm growth phase the expected IMF BY-dependent dawn-dusk asymmetry is observed over the entire convection pattern, but that during the expansion phase this asymmetry is retained only in the polar cap and dayside auroral zone. In the nightside auroral zone the convection is reordered according to the local substorm electrodynamics with any remaining dusk-dawn asymmetry being more closely related to the magnetic local time of substorm onset, itself only weakly governed by IMF BY. Owing to the preponderance of substorms occurring just prior to magnetic midnight, the substorm-asymmetry tends to be an azimuthal extension of the dusk convection cell across the midnight sector, a manifestation of the so-called “Harang discontinuity.” This results in the northern (southern) hemisphere nightside auroral convection during substorms generally resembling the expected pattern for negative (positive) IMF BY. When the preexisting convection pattern in the northern (southern) hemisphere is driven by positive (negative) IMF BY, the nightside auroral convection changes markedly over the course of the substorm to establish this same “Harang” configuration.

  3. Ionospheric convection and currents in the midnight sector on November 8, 1979

    SciTech Connect

    Foster, J.C.; Doupnik, J.R.; Stiles, G.S.

    1981-04-01

    Chatanika Radar observations of ionospheric convection velocities spanning auroral latitudes (58/sup 0/-75/sup 0/..lambda..), and contours of electrostatic potential derived from them, are described for a period of moderately strong geomagnetic activity in the midnight sector. Digitized H component magnetograms and contours of magnetic perturbation, ..delta..H, derived from them are presented in order to compare the convection pattern and radar-deduced currents with the observed ground response to auroral electrojets. In spite of midnight sector substorm activity, the convection pattern maintains a two cell character. The latitude of greatest negative potential in the evening sector, determined from the radar data, accurately denotes the position of the Harang discontinuity in the ionospheric currents.

  4. Coupled Magnetotail-Ionosphere Asymmetries from Ionospheric Hall Conduction

    NASA Astrophysics Data System (ADS)

    Lotko, W.; Smith, R. H.; Zhang, B.; Ouellette, J.; Brambles, O.; Lyon, J.; Wiltberger, M. J.

    2014-12-01

    Fast convective transport in the plasma sheet is more prevalent in the premidnight (dusk) sector relative to postmidnight. Ionospheric convection exhibits related asymmetries - more flux typically circulates in the dusk cell than in the dawn cell, and the nightside convection pattern is rotated clockwise when viewed over the North Pole. We show, using global simulations of the solar wind-magnetosphere-ionosphere interaction, that the electrodynamic interaction between Earth's magnetosphere and ionosphere produces asymmetries resembling observed distributions in plasmasheet flows and ionospheric convection (Figure, center panel). The primary causal agent in the simulations is a meridional gradient in ionospheric Hall conductance which, through Cowling polarization, regulates the distributions of i) electrical currents flowing within and between the ionosphere and magnetotail and ii) the nightside reconnection rate and resulting dawn-dusk distribution of plasma sheet fast flows. The asymmetry disappears in the simulation when the Hall conductance is taken to be uniform (left panel), and it reverses when the conductance is artificially depleted at auroral latitudes (right panel). The coupling between meridional currents and electric fields in the ionosphere and axial currents and electric fields in the plasmasheet is demonstrated by a simple model for non-ideal coupling of field-aligned currents flowing between the plasma sheet and the region of enhanced ionospheric conductance straddling the nightside convection throat.

  5. Evolution of high latitude ionospheric convection associated with substorms: Multiple radar observations

    NASA Astrophysics Data System (ADS)

    Zou, Shasha

    The work presented in this dissertation concerns evolution of the high latitude ionospheric convection and the relevant current systems associated with substorms, with emphasize on these features near the nightside Harang reversal region. Three different types of radars, including the Super Dual Auroral Radar Network (SuperDARN) coherent-scatter radars, the new advanced modular incoherent-scatter radar at Poker Flat (PFISR), and the Sondrestrom incoherent-scatter radar (ISR), have been utilized. Observations from those radars, together with those from complementary instruments, including satellites and other ground-based instruments, have revealed fundamental new understand of the ionospheric electrodynamic properties associated with substorms. By using the SuperDARN and the PFISR radars, we found that the auroral activity at substorm onset is located in the center of the Harang reversal, which represents a key region in the magnetospheric and ionospheric convection and is part of the Region 2 system. We have also shown that nightside convection flows exhibit repeatable, distinct variations at different locations relative to the substorm-related auroral activity. Taking advantage of the simultaneous flow and ionization measurements from PFISR, a current closure relation has been found between the Region 2 and the substorm field-aligned current systems. These observations demonstrate a strong coupling between the Region 2 system and the substorm dynamics. This study sheds new light on the substorm-related magnetosphere-ionosphere coupling and contributes to the building of a holistic picture of the substorm dynamics. The third radar has been used to study the dayside ionospheric convection response to the external soar wind and IMF driving and its role in substorm dynamics. The results have been applied to study substorm triggering and in the future could be used to study the relation between the external driving and the formation of the Harang reversal.

  6. Contribution of low-energy ionospheric protons to the plasma sheet

    NASA Technical Reports Server (NTRS)

    Delcourt, D. C.; Moore, T. E.; Chappell, C. R.

    1994-01-01

    The magnetospheric transport of low-energy ionospheric ions is examined by means of three-dimensional particle codes. Emphasis is placed on the behavior of polar wind and cleft originating protons. It is demonstrated that, via nonadiabatic motion inside the neutral sheet, these ions can significantly contribute to the populations of the plasma sheet. The importance of this contribution is found to depend critically upon the dynamics of particles originating from the highest latitudes, as these possibly have access to the distant tail. Hence it is shown that polar wind H(+) expelled into the magnetosphere at very low energies (in the electron volt range) preferentially feed the plasma sheet during quiet times, experiencing accelerations up to several kiloelectron volts upon return into the inner magnetosphere. In contrast, during disturbed times, the intensifying magnetospheric convection confines this population to low L shells where it travels in a nearly adiabatic manner. As for the protons originating from the cleft fountain, the simulations reveal that they can be transported up to the vicinity of the distant neutral line in the nightside sector. Via interaction with the neutral sheet, these ionospheric ions are rapidly raised to the characteristic plasma sheet energy range. The density levels contributed by these populations are quite substantial when compared to those measured in situ. These simulations establish an active role of low-energy ionospheric ions in the overall magnetospheric dynamics.

  7. Observations of ionospheric convection from the Wallops SuperDARN radar at middle latitudes

    NASA Astrophysics Data System (ADS)

    Baker, J. B. H.; Greenwald, R. A.; Ruohoniemi, J. M.; Oksavik, K.; Gjerloev, J. W.; Paxton, L. J.; Hairston, M. R.

    2007-01-01

    During geomagnetic storms the ability of the Super Dual Auroral Radar Network (SuperDARN) to measure ionospheric convection becomes limited when the radars suffer from absorption and the auroral disturbance expands equatorward of the radar sites. To overcome these shortcomings, it was decided to construct a SuperDARN radar at middle latitudes on the grounds of the NASA Wallops Flight Facility. This paper presents the first comprehensive analysis of Doppler measurements from the Wallops radar, which commenced operations in May 2005. Wallops measurements are compared with the Goose Bay radar during the onset of a geomagnetic storm on 31 August 2005: Goose Bay measured the onset of geomagnetic activity at high latitude while Wallops monitored the expansion of convection to middle latitudes. Average convection patterns binned by the Kp geomagnetic index are also presented. During weak-moderate geomagnetic activity (Kp ? 3) the Wallops radar observes ionospheric irregularities between 50° and 60° magnetic latitude drifting westward across much of the nightside. When these measurements are incorporated into the calculation of an average SuperDARN convection pattern, the streamlines of polar cap outflow on the nightside become kinked in a manner reminiscent of the Harang discontinuity. This morphology arises quite naturally when the two-cell convection at high latitudes merges with the prevailing westward convection at middle latitudes. During increased geomagnetic activity (Kp ? 3), Wallops is able to measure the expansion of auroral electric fields to middle latitudes and the average SuperDARN cross-polar cap potential is increased by 25%.

  8. Ionospheric Plasma Bubbles observed at 29 degree south

    NASA Astrophysics Data System (ADS)

    Goulart, H. O.; Grellmann, E. A.; Wrasse, C. M.; Makita, K.; Takahashi, H.; Schuch, N. J.

    Ionospheric plasma bubbles have been observed by airglow OI6300 imaging technique at the Southern Space Observatory San Martino da Serra 29 S 54 W Brazil since 2004 The bubbles plasma depletion along the magnetic field line are frequently observed in a period from September to March during the southern spring equinox to autumn equinox seasons The frequency of occurrence avarege of eight bobbles for the period and its seasonal dependency are presented and compared to the observations of other locations

  9. Magnetospheric convection and the high latitude F2 ionosphere. [in the polar regions

    NASA Technical Reports Server (NTRS)

    Knudsen, W. C.

    1973-01-01

    Behavior of the polar ionospheric F-layer as it is convected through the cleft, over the polar cap, and through the night side F-layer trough zone was investigated. Passage through the cleft adds of the order of 200,000 ions/cu cm in the vicinity of the F 2 peak and redistributes the ionization above approximately 400 km altitude to conform with an increased electron temperature. The F-layer is also raised of the order of 20 km in altitude by the convection electric field. In the night soft electron precipitation zone, the layer is lowered in altitude by the convection electric field, and then decays, primarily by chemical recombination, as it convects equatorward and around the dawn side of the earth. In the absence of ionization sources, decay by factors of the order of 100 to 1000 occur prior to entry into the sunlit hemisphere, thus forming the F-layer night trough.

  10. Multi-Resolution Assimilative Analysis of High-Latitude Ionospheric Convection in both Hemispheres

    NASA Astrophysics Data System (ADS)

    Thomas, Z. M.; Matsuo, T.; Nychka, D. W.; Cousins, E. D. P.; Wiltberger, M. J.

    2014-12-01

    Assimilative techniques for obtaining complete maps of ionospheric electric potential (and related parameters) from sparse radar and satellite observations greatly facilitates studies of magnetosphere/ionosphere coupling. While there is much scientific interest in studying interhemispheric asymmetry in ionospheric convection at both large and small scales, current mapping procedures rely on spherical harmonic expansion techniques, which produce inherently large-scale analyses. Due to the global nature of the spherical harmonics, such techniques are also subject to various instabilities arising from sparsity/error in the observations which can introduce non-physical patterns in the inferred convection. We present a novel technique for spatial mapping of ionospheric electric potential via a multi-resolution basis function expansion procedure, making use of compactly supported radial basis functions which are flexibly located over geodesic grids; the coefficients are modeled via a Markov random field construction. The technique is applied to radar observations from the Super Dual Auroral Radar Network (SuperDARN), whereupon careful comparison of interhemispheric differences in mapped potential is made at various scales.

  11. Application of nonlinear methods to the study of ionospheric plasma

    NASA Astrophysics Data System (ADS)

    Chernyshov, A. A.; Mogilevsky, M. M.; Kozelov, B. V.

    2015-01-01

    Most of the processes taking place in the auroral region of Earth's ionosphere are reflected in a variety of dynamic forms of the aurora borealis. In order to study these processes it is necessary to consider temporary and spatial variations of the characteristics of ionospheric plasma. Most traditional methods of classical physics are applicable mainly for stationary or quasi-stationary phenomena, but dynamic regimes, transients, fluctuations, selfsimilar scaling could be considered using the methods of nonlinear dynamics. Special interest is the development of the methods for describing the spatial structure and the temporal dynamics of auroral ionosphere based on the ideas of percolation theory and fractal geometry. The fractal characteristics (the Hausdorff fractal dimension and the index of connectivity) of Hall and Pedersen conductivities are used to the description of fractal patterns in the ionosphere. To obtain the self-consistent estimates of the parameters the Hausdorff fractal dimension and the index of connectivity in the auroral zone, an additional relation describing universal behavior of the fractal geometry of percolation at the critical threshold is applied. Also, it is shown that Tsallis statistics can be used to study auroral ionosphere

  12. Impact of the dipole tilt angle on the ionospheric plasma in the outer plasmasphere

    NASA Astrophysics Data System (ADS)

    Marchaudon, Aurelie; Blelly, Pierre-Louis

    2015-04-01

    We have developed a new interhemispheric 16-moment based ionosphere model. This model describes the field-aligned transport of the multi-species ionospheric plasma (6 ions) from one hemisphere to the other, taking into account source processes at low altitudes (photoionization, chemistry) and coupling with suprathermal electrons. We simulate the convection and corotation transport of closed flux tubes in the outer plasmasphere for tilted/eccentric dipolar magnetic field configuration. We ran the model in solstice and equinox conditions and for two plasmapause boundary conditions: one corresponding to standard conditions with a stagnation point at 4.5 Earth radii (RE) and 15h Magnetic Local Time (MLT) and one corresponding to very quiet conditions with a stagnation point at 6 RE and 15h MLT. For each season/stagnation simulation, the model is run for 30 days before the equinox/solstice date in order to eliminate the transients. The goal is to study the combined effect of the tilt of the magnetic field and the rotation axis on the field-aligned dynamics and overall equilibrium of the subauroral ionosphere. In the classical representation of the plasmasphere, the ionosphere only depends on angular MLT sector. We will show that due to the tilt effect, this view is erroneous and no real dynamic equilibrium is reached, in particular close to the stagnation point where we can observe large day-to-day variations in the ionospheric parameters. Finally, we will present the temperatures anisotropy development along the flux tube for different positions of the stagnation point.

  13. Jovian ionospheric conductivity and magnetospheric plasma outflow - Voyager 1

    NASA Astrophysics Data System (ADS)

    Hairston, M. R.; Hill, T. W.

    1985-10-01

    Using magnetic field and plasma data from the Voyager 1 inbound encounter, the authors have derived local values for the mass outflow rate and the radial bulk velocity in the dayside Jovian magnetosphere, and for the height-integrated Pedersen conductivity of the Jovian ionosphere. These values, accurate within a factor of 2, are compatible with previous order-of-magnitude estimates of these quantities. The results suggest that the shape of the plasma sheet is more complicated than previously suspected. A search for evidence of enhanced plasma outflow in the active sector was inconclusive.

  14. Plasma motion in the Venus ionosphere: Transition to supersonic flow

    SciTech Connect

    Whitten, R.C.; Barnes, A. (NASA Ames Research Center, Moffet Field, CA (USA)); McCormick, P.T. (Santa Clara Univ., CA (USA))

    1991-07-01

    A remarkable feature of the ionosphere of Venus is the presence of nightward supersonic flows at high altitude near the terminator. In general the steady flow of an ideal gas admits a subsonic-supersonic transition only in the presence of special conditions, such as a convergence of the flow followed by divergence, or external forces. In this paper, the authors show that the relatively high pressure dayside plasma wells up slowly, and at high altitude it is accelerated horizontally through a relatively constricted region near the terminator toward the low-density nightside. In effect, the plasma flows through a nozzle that is first converging, then diverging, permitting the transition to supersonic flow. Analysis of results from previously published models of the plasma flow in the upper ionosphere of Venus shows how such a nozzle is formed. The model plasma does indeed accelerate to supersonic speeds, reaching sonic speed just behind the terminator. The computed speeds prove to be close to those observed by the Pioneer Venus orbiter, and the ion transport rates are sufficient to produce and maintain the nightside ionosphere.

  15. Interplanetary magnetic field By and auroral conductance effects on high-latitude ionospheric convection patterns

    NASA Astrophysics Data System (ADS)

    Tanaka, T.

    2001-11-01

    The dependence of the ionospheric electric potential (convection) on the interplanetary magnetic field (IMF) and the ionospheric conductivity is investigated to understand the generation of convection patterns in the framework of the solar wind-magnetosphere-ionosphere (S-M-I) coupling scheme and the merging concept. A numerical magnetohydrodynamic (MHD) simulation is adopted for the study of the present problem. To achieve a high resolution in the ionosphere, the MHD calculation employs the finite volume (FV) total-variation diminishing (TVD) scheme with an unstructured grid system. The two-cell convection patterns reproduced from simulation are shown for several cases under the southward IMF condition during the growth-phase interval. In the investigation of these results, special attention is paid to the analysis of mirror symmetry in the convection patterns with respect to the IMF By. On the dayside in the Northern Hemisphere, IMF By- (By+) generates flow deflection on newly opened field lines toward the dusk (dawn) without a severe violation of the mirror symmetry. While the mirror symmetry of the convection pattern is maintained even on the nightside when the ionospheric conductivity is uniform, it is not maintained on the nightside when the ionospheric conductivity is nonuniform. A realistic ionospheric conductivity modifies the convection pattern in the Northern (Southern) Hemisphere so as to emphasize distinctive features seen for IMF By+ (By-) under a uniform conductivity, and the reproduced convection patterns coincide with the observation quite well including fine signatures on the nightside, both for IMF By- and By+. Because of the nonuniform conductivity, cell centers of convection are shifted to the earlier magnetic local times, and the antisunward flow in the northern polar cap is nearly aligned with noon-midnight meridian for IMF By-, while the flow in the northern polar cap has a significant inclination from prenoon to premidnight for IMF By+. These convection patterns can be understood by considering the effect due to the Hall current closure of the region-1 field-aligned current. The analysis for the dependence of nightside convection on IMF By and ionospheric conductivity shows that the Harang discontinuity is attributed partially to the structure of magnetospheric driver but mainly to the effect of nonuniform auroral conductivity. As a consequence, it is more adequate to say that convection patterns are more or less caused by the synthesized effect of more than one process rather than a single elementary process. Reproduced convection patterns in this paper show a particular coincidence with satellite observations summarized by adopting the pattern-recognition-based approach.

  16. Electron densities in the upper ionosphere of Mars from the excitation of electron plasma oscillations

    E-print Network

    Gurnett, Donald A.

    Electron densities in the upper ionosphere of Mars from the excitation of electron plasma to remote radio sounding of the ionosphere of Mars, the MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) instrument on the Mars Express spacecraft is also able to measure the in situ electron

  17. The character of drift spreading of artificial plasma clouds in the middle-latitude ionosphere

    Microsoft Academic Search

    N. Blaunstein

    1996-01-01

    Nonlinear equations describing the evolution of plasma clouds with real initial sizes, along and across the geomagnetic field B, which drift in the ionosphere in the presence of an ambient electric field and a neutral wind have been solved and analysed. An ionospheric model close to the real conditions of the middle-latitude ionosphere is introduced, taking into account the altitude

  18. How Solar Wind-Magnetosphere-Ionosphere Coupling Differentiates Magnetospheric Convection Modes

    NASA Astrophysics Data System (ADS)

    Lotko, W.; Brambles, O.; Ouellette, J.; Zhang, B.; Lyon, J.; Wiltberger, M. J.; Merkin, V. G.

    2012-12-01

    Magnetosphere-ionosphere (MI) coupling is mediated by fluxes of charged-particles and electromagnetic energy flowing between the magnetosphere and ionosphere. Synchronous MI coupling occurs when these fluxes rapidly transit between the two regions relative to the time scale for substorm-induced changes in convection. Latent MI coupling occurs when fluxes stimulated by dynamical changes in one region (e.g., ionospheric outflows) are slow to reach and affect the other region (e.g., the plasmasheet). With continual strong solar wind / interplanetary magnetic field (SW/IMF) driving, latent coupling has the capacity to produce relaxation oscillations of the coupled system. Fast flux exchanges are mediated by electrons and Alfvén waves; slow exchanges are mediated by ion flows, principally O+. With this background, the following scenario for the role of MI coupling in producing different magnetospheric convection modes is considered, with the concepts illustrated by global simulations. The steady magnetospheric convection (SMC) mode occurs for the SW/IMF driving conditions reported in statistical studies, e.g. DeJong et al. (2009). Global simulations indicate that the mean conditions inducing SMC do not stimulate sufficient low-altitude activity to sustain the intense ionospheric outflows that produce large changes in the nightside plasmasheet and reconnection rate. For the SMC mode, MI coupling is thus mediated mainly by flows of electrons and Poynting fluxes between the two regions. Substorms (and more strongly driven proto-SMC events) deposit substantial electromagnetic and particle energy in the ionosphere and low-altitude magnetosphere. If the energy deposition is sufficient to power intense fluxes of heavy ion outflows, the pressure of the outflowing-come-plasmasheet ions will eventually inflate and stretch the nightside plasmasheet and modify the nightside reconnection rate. Several modes of response are then possible depending on the persistence of SW/IMF driving. The causative substorm is "isolated" if the SW/IMF driving that produced it is not subsequently maintained, i.e., the driving fails to increase the magnetic flux in the polar cap. This class includes impulsively triggered substorms, some of which might otherwise continue as an SMC state. Whether the isolated substorm is preceded and/or followed by an SMC state or irregular activity depends on the variability of SW/IMF driving. A quasi-periodic sequence of substorms follows the initiating substorm when energy transfer to the magnetosphere by strong, persistent and quasi-steady SW/IMF driving maintains a superfluent outflow flux from the nightside ionosphere, while continuing to add lobe magnetic flux. These distinctions are illustrated by global simulations of interplanetary SI and CME events, together with numerical experiments based on controlled SW/IMF conditions.

  19. Are plasma depletions in Saturn's ionosphere a signature of time-dependent water input?

    E-print Network

    Mendillo, Michael

    Are plasma depletions in Saturn's ionosphere a signature of time- dependent water input? Luke Moore the presence of numerous ``ionospheric holes'', or plasma depletions, in Saturn's upper atmosphere that cannot the observed plasma depletions. The required influxes present a target to assess for the possible sources

  20. Ionospheric and Solar Plasmas in Geospace Storms

    Microsoft Academic Search

    T. E. Moore; M. H. Fok; D. C. Delcourt; J. A. Fedder; M. W. Liemohn; S. P. Slinker

    2004-01-01

    We consider the formation of ring current plasmas in the inner magnetosphere in moderately active conditions that precondition the plasma sheet and ring current-like region for full fledged geospace storms. We seek to better understand recent IMAGE energetic neutral atom observations of the ring current, showing that proton injection is relatively smooth and continuous, while O+ injection is episodic in

  1. Radio pumping of ionospheric plasma with orbital angular momentum.

    PubMed

    Leyser, T B; Norin, L; McCarrick, M; Pedersen, T R; Gustavsson, B

    2009-02-13

    Experimental results are presented of pumping ionospheric plasma with a radio wave carrying orbital angular momentum (OAM), using the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. Optical emissions from the pumped plasma turbulence exhibit the characteristic ring-shaped morphology when the pump beam carries OAM. Features of stimulated electromagnetic emissions (SEE) that are attributed to cascading Langmuir turbulence are well developed for a regular beam but are significantly weaker for a ring-shaped OAM beam in which case upper hybrid turbulence dominates the SEE. PMID:19257597

  2. Plasma convection and line-tying

    SciTech Connect

    Fornaca, S.

    1983-03-01

    The directed motion of a low-..beta.. plasma across a toroidal magnetic field is examined as the degree of electrical contact between the plasma and a conducting end wall (line-tying) is varied in a controlled manner. Experimentally, little difference is found between the motion of a completely isolated plasma and that of a plasma in contact with a wall that does not emit electrons. As the degree of line-tying is increased by making the end wall electron-emitting, the cross-field convection of the plasma is increasingly suppressed. Beyond a critical emission current density, no further suppression is observed. When the system is in the surface-line-tying configuration, the suppression of the directed cross-field motion is accompanied by a large increase in the radial transport of plasma.

  3. Final Progress Report for Ionospheric Dusty Plasma In the Laboratory [Smokey Plasma

    SciTech Connect

    Robertson, Scott [Professor

    2010-09-28

    “Ionospheric Dusty Plasma in the Laboratory” is a research project with the purpose of finding and reproducing the characteristics of plasma in the polar mesosphere that is unusually cold (down to 140 K) and contains nanometer-sized dust particles. This final progress report summarizes results from four years of effort that include a final year with a no-cost extension.

  4. Computer Simulation of Convective Plasma Cells

    E-print Network

    Carboni, Rodrigo

    2015-01-01

    Computer simulations of plasmas are relevant nowadays, because it helps us understand physical processes taking place in the sun and other stellar objects. We developed a program called PCell which is intended for displaying the evolution of the magnetic field in a 2D convective plasma cell with perfect conducting walls for different stationary plasma velocity fields. Applications of this program are presented. This software works interactively with the mouse and the users can create their own movies in MPEG format. The programs were written in Fortran and C. There are two versions of the program (GNUPLOT and OpenGL). GNUPLOT and OpenGL are used to display the simulation.

  5. Is Jupiter's ionosphere a significant plasma source for its magnetosphere?

    NASA Astrophysics Data System (ADS)

    Nagy, A. F.; Barakat, A. R.; Schunk, R. W.

    1986-01-01

    A semikinetic model was used to study the steady state, collisionless, polar wind outflow from the Jovian polar caps. H+ escape fluxes and energies were calculated for a range of conditions, including several values of the ambient electron temperature, different hot electron populations, and both with and without the effects of the centrifugal force. The calculations indicate that if hot electron populations exist over the Jovian polar caps, as they do on earth, polar wind escape fluxes of the order of 108cm-2s-1 are possible. When integrated over the polar cap area, escape fluxes of this order of magnitude imply an ionospheric source strength of 2×1028ions/s, which is comparable to the present estimate of the total magnetospheric plasma source population. Therefore, the ionosphere may play an important role in populating the Jovian magnetosphere, specifically the "hidden", low energy, light ion component of the population.

  6. Is Jupiter's ionosphere a significant plasma source for its magnetosphere?

    NASA Technical Reports Server (NTRS)

    Nagy, A. F.; Barakat, A. R.; Schunk, R. W.

    1986-01-01

    A semikinetic model was used to study the steady state, collisionless, polar wind outflow from the Jovian polar caps. H(+)-escape fluxes and energies were calculated for a range of conditions, including several values of the ambient electron temperature, different hot electron populations, and both with and without the effects of the centrifugal force. The calculations indicate that if hot electron populations exist over the Jovian polar caps, as they do on earth, polar wind escape fluxes of the order of 10 to the 8th per sq cm s are possible. When integrated over the polar cap area, escape fluxes of this order of magnitude imply an ionospheric source strength of 2 x 10 to the 28th ions/s, which is comparable to the present estimate of the total magnetospheric plasma source population. Therefore, the ionosphere may play an important role in populating the Jovian magnetosphere, specifically the hidden, low energy, light ion component of the population.

  7. Stimulated plasma waves in the ionosphere

    Microsoft Academic Search

    Robert F. Benson

    1977-01-01

    observed above ( (at the maximum frequency of the Bernstein modes) and the (Dn resonances observed below ( (called the diffuse resonances). Most of the resonances can be interpreted in terms of the reception of longitudinal plasma waves stimulated by the sounder pulse. In some cases these waves, which travel with low group velocity (of the order of the electron

  8. Artificial plasma jet in the ionosphere

    NASA Astrophysics Data System (ADS)

    Haerendel, G.; Sagdeev, R. Z.

    The dynamics of an artificially injected plasma beam in the near-earth space are analyzed in terms of the beam structure, its propagation across the magnetic field, and the resulting wave phenomena (Porcupine Project, flight 4, March 31, 1979). Out of the four ejectable canisters attached to the main payload, two were instrumented by the U.S., one by the USSR (the Xenon plasma beam experiment), and one by West Germany (carrying a barium ion jet experiment). The propagation of the plasma seems to occur in three stages, with high-frequency broad-band oscillations mainly localized in the 'core' of the jet, while low-frequency oscillations were spatially separated from it. The generation region of LF oscillations was found to be much wider than the jet core. As a result of the interaction between the plasma beam and the ambient medium a heating of electrons, up to energies of about 20 eV, associated with LF noise was observed. The behavior of high-energy ions and the observed HF wave phenomena need further analysis.

  9. Study plasma interactions in the auroral ionosphere

    NASA Technical Reports Server (NTRS)

    Anderson, H. R.; Wolf, R. A.

    1983-01-01

    Analyzed data from rocket flight, 29.007UE is presented. In a discrete electron arc the measured upward moving electrons are well accounted for by secondaries produced in collisional scattering of the measured downcoming electrons. No collective mechanisms need to invoke. The low energy downcoming electrons are accounted for by thermal plasma accelerated through a potential drop of a few kV that specularly reflects upward-moving lower energy electrons. No low altitude collective effects need to invoke in the arc. Simultaneous measurements of electric field by double probes on 29.007 and the Chatanika Radar allow one to infer that there are upward drifting ions above the discrete electron arc, and there is a westward neutral wind in the discrete arc. Two rocket payloads were built to investigate plasma effects in the pulsating aurora.

  10. Connections between large-scale transport to the inner magnetosphere from the distant plasma sheet, region 2 coupling to the ionosphere, and substorm and storm dynamics (Invited)

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Wang, C.; Zou, S.; Gkioulidou, M.; Nishimura, Y.; Shi, Y.; Kim, H.; Xing, X.; Nicolls, M. J.; Heinselman, C. J.

    2009-12-01

    Studies using a variety of ground-based and spacecraft observations, as well as the Rice Convection Model, have taught us much about the connection between plasma sheet transport and particle distributions within the inner plasma sheet. These studies have shown that plasma moves earthward (equatorward in the ionosphere) after enhancements in convection to reach the near-Earth plasma sheet, leading to the enhancements in plasma sheet pressure that are responsible for the growth phase of substorms and the partial ring current. The highest inner plasma sheet pressures likely occur in the subauroral polarization streams (SAPS) region of the evening-side convection cell, lying equatorward of the Harang reversal. Both the Harang reversal and SAPS are manifestations of the region 2 (R2) electrodynamical coupling, so that transport to the near-Earth plasma sheet is strongly influenced by the R2 magnetosphere-ionosphere coupling. Modeling results show that this transport, together with the concurrent R2 coupling, is also strongly dependent on the plasma distributions that enter the plasma sheet. However, the entering plasma distribution is expected to have substantial spatial and temporal structure, which should impart substantial spatial structure and time dependencies to the inner plasma sheet particle distributions. In addition, very recent analyses indicate that the temporal variations of the particle distribution entering the plasma sheet, and the ensuing transport of new particle distributions within the plasma sheet, is fundamental to understanding the substorm expansion phase. Taken together, the above results indicate that an important understanding of inner magnetosphere particle distributions and their dynamics, as well as of major geomagnetic disturbances, is likely to come from integrated studies of plasma sheet particle entry, particle transport, and electrodynamical coupling to the ionosphere.

  11. Case Study of the Evolution of Global Ionospheric Convection during Substorms

    NASA Astrophysics Data System (ADS)

    Hashimoto, K. K.; Lyons, L.; Kikuchi, T.

    2004-12-01

    Evolution of global ionospheric convection is investigated for a substorm event on February 2, 2002 with unusually good SuperDARN radar echo coverage. Global magnetometer chains from the polar cap to the dip-equator show the development of the DP2 electric field during the growth phase, which followed a sudden southward turning of the IMF. Three DP2 reductions were observed during the 90 min substorm growth phase, the first two of which were followed by further DP2 enhancement. Electron precipitation measured by the IMAGE FUV/SI13 at 16-17 MLT at 70-75 degrees magnetic latitudes was coherent with these changes of DP2, and the dusk-side proton precipitation measured by the IMAGE FUV/SI12 showed more gradual changes reflecting the overall DP2 changes. The DP2 convection changes were seen clearly in the SuperDARN data. Prior to the second two convection reductions, but not prior to the first, flow shear of the Harang discontinuity was observed to develop in the post-midnight sector. The Harang discontinuity shifted equatorward from 75 to 68 degrees magnetic latitudes as the growth phase developed. The second and the third reductions in convection led to the pseudo break-up and the expansion phase onset, respectively, both of which initiated within the Harang flow-shear region and were associated with large weakening of the Harang flow shear. Our results suggest that both auroral activity on the night-side and auroral precipitation on the afternoon-to-dusk region are strongly controlled by global convection, that reduction in convection leads to substorm expansion or pseudo break-up only under the condition of a well-developed Harang flow shear, and that an enhancement of convection prior to full expansion-phase development leads to termination of the expansion phase (i.e. a pseudo breakup) and reformation of the Harang shear.

  12. On Plasma Instabilities in the Polar Cap Ionosphere

    NASA Astrophysics Data System (ADS)

    Oksavik, K.; Moen, J. I.; Van Der Meeren, C.; Lester, M.

    2012-12-01

    Plasma instabilities in the polar ionosphere cause the otherwise uniform plasma to develop inhomogeneous magnetic field-aligned structures over scale sizes from tens of km to meters. Radio waves propagating through these irregularities will experience strong scintillation, which disrupts VHF, UHF and GNSS navigation systems. At longer wavelengths (HF and VHF) the same plasma irregularities will also backscatter radio waves. In this presentation we describe efforts that are currently ongoing at Svalbard to study both the cause and effect of these irregularities. We present data from EISCAT, SuperDARN, ground-based optics, and in-situ sounding rockets. We also present initial results from a new receiver network that we are installing around Svalbard to monitor the impact on GNSS navigation systems.

  13. Transverse ion heating in multicomponent plasmas. [in ionosphere

    NASA Technical Reports Server (NTRS)

    Ashour-Abdalla, M.; Okuda, H.; Kim, S. Y.

    1987-01-01

    A new mechanism is proposed for plasma modes which can occur only in a multicomponent plasma and not in pure electron-ion plasma. The addition of ions creates a new instability near the ion-ion hybrid mode whose frequency is adequate for the wave to interact with oxygen ions. To study heating of ions (such as ionospheric oxygen ions) in presence of auroral electrons, several numerical simulations were carried out using a one-dimensional electrostatic code in a magnetic field. It was found that in the presence of electrons drifting along auroral field lines into the ionosphere, the ion-ion hybrid mode can be driven unstable when the electron drift speed is too small to excite the lower hybrid instability. Since the ion-ion mode has a smaller frequency than that of the lower hybrid waves, it can couple to the heavy ions, resulting in a substantial heating of heavy ions; on the other hand, because of their frequencies, the lower hybrid waves can accelerate only light ion species.

  14. Effects of finite plasma pressure on centrifugally driven convection in Saturn's inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Liu, X.; Hill, T. W.

    2012-07-01

    We have previously shown simulation results for centrifugally driven plasma convection in Saturn's inner magnetosphere (2 < L < 12) using the Rice Convection Model, including a continuously active distributed plasma source, and the effects of the Coriolis force and the pickup current. These simulations result in a quasi-steady state, in which fast, narrow inflow channels alternate with slower, wider outflow channels, consistent with Cassini Plasma Spectrometer observations. These previous simulations, however, did not include the plasma pressure. We investigate here the effects of finite plasma pressure and the associated gradient-curvature drift current by giving the cold plasma a finite temperature. Our simulations confirm the theoretical expectation that a finite plasma pressure produces a force in the positive radial direction, the same direction as the centrifugal force, and acts as an additional driver of plasma convection. Our simulations also confirm that the radial velocities can be reduced (to keep them within observational constraints) by increasing the assumed ionospheric Pedersen conductance (also within observational constraints).

  15. Equinoctial asymmetry of ionospheric vertical plasma drifts and its effect on F-region plasma density

    Microsoft Academic Search

    Zhipeng Ren; Weixing Wan; Libo Liu; Yiding Chen; Huijun Le

    2011-01-01

    The equinoctial asymmetry of the ionospheric vertical E × B plasma drift velocity (V$\\\\perp$) in the equatorial F region is investigated based on observations from ROCSAT-1 during 1999 to 2004. It is found that the observed asymmetry exhibits obvious local time dependence with three noticeable features. First, in the Eastern Hemisphere during the interval between 0900 and 1300 LT, V$\\\\perp$

  16. Using Plasma Convection to Observe Global Electric Fields in the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Jahn, J.; Samara, M.; Henderson, M. G.; Thomsen, M. F.; Denton, M.; Fok, M.

    2005-12-01

    Solar wind driven large scale electric fields play an important role in the dynamics of the plasmasphere, the storm-time ring current, and the plasma sheet access to the inner magnetosphere. Local in situ measurements of the electric field provide a detailed yet highly localized picture. Global field maps, often derived by mapping out ionospheric measurements or models, may only inadequately predict or completely miss important field structures like SAPS. Medium to low energy plasma measurements (below a few keV) can be used to help bridge the gap between existing measurement and modeling techniques. We are presenting results from medium energy ENA imaging combined with in situ plasma measurements from the magnetosphere, ionosphere, and the solar wind as well as ground based ionospheric observations. We show that both in terms of spatial distribution and intensity ENA measurements show a remarkable sensitivity to the global electric field structure. We discuss two distinct sets of observations: (1) the sunward motion of the inner edge of the plasma sheet in response to periods of enhanced convection, (2) the long-term correlation between Kp and plasma content of the inner magnetosphere (predominantly plasma sheet material) derived from ENA measurements. We show that ENA observations are very sensitive to the global electric field and its changes, both in the sense of capturing the global plasma dynamics and in the sense of measuring the total amount of plasma delivered into the inner magnetosphere. The key to observing these effects lies in concentrating on particle energies low enough (below a few keV) such that the plasma motion is controlled by electric rather than magnetic fields.

  17. Studies of conjugate plasma convection in the vicinity of the Harang discontinuity

    NASA Technical Reports Server (NTRS)

    Dudeney, J. R.; Rodger, A. S.; Pinnock, M.; Ruohoniemi, J. M.; Baker, K. B.

    1991-01-01

    This paper presents two case studies of the large-scale nightside ionospheric plasma convection observed in the two polar regions utilizing HF backscatter radars. The times at which the nightside flow reversal (the Harang discontinuity) occurs is seen to differ by several hours between the two study periods and between the two hemispheres. Flow reversal appeared simply to be shifted to later magnetic times in the Southern Hemisphere, while the evening westward flow was disrupted by the occurrence of eastward flow ahead of the Harang discontinuity in the Northern Hemisphere.

  18. Interaction of Precipitating Electrons with Ionospheric Plasma: Acceleration of Ionospheric Electrons

    Microsoft Academic Search

    V. L. Galinsky; S. K. Ride; V. I. Shevchenko

    1997-01-01

    The tail heating of the ionospheric electrons due to Landau resonant interaction with lower hybrid waves in the auroral ionosphere is studied. The waves are excited due to so-called fan instability based on an anomalous Doppler resonance of waves with precipitating electrons^1. A hybrid method of incomplete numerical simulations in concert with the spectral method are used to investigate the

  19. Direct evidence of double-slope power spectra in the high-latitude ionospheric plasma

    NASA Astrophysics Data System (ADS)

    Spicher, A.; Miloch, W. J.; Moen, J. I.

    2014-03-01

    We report direct observations of the double-slope power spectra for plasma irregularities in the F layer of the polar ionosphere. The investigation of cusp irregularities ICI-2 sounding rocket, which was launched into the polar cusp ionosphere, intersected enhanced plasma density regions with decameter-scale irregularities. Density measurements at unprecedented high resolution with multi-Needle Langmuir Probes allowed for a detailed study of the plasma irregularities down to kinetic scales. Spectral analysis reveals double-slope power spectra for regions of enhanced fluctuations associated mainly with density gradients, with the steepening of the spectra occurring close to the oxygen gyrofrequency. These findings are further supported with the first results from the ICI-3 rocket, which flew through regions with strong precipitation and velocity shears. Previously, double-slope spectra have been observed in the equatorial ionosphere. The present work gives a direct evidence that the double-slope power spectra can be common in the high-latitude ionosphere.

  20. The response of plasma density to breaking inertial gravity wave in the lower regions1 of ionosphere2

    E-print Network

    Tang, Wenbo

    of ionosphere2 Wenbo Tang1, a) and Alex Mahalov1, b) 3 School of Mathematical & Statistical Sciences, Arizona. This model is developed based on a previous ionospheric model that examines the transport patterns of plasma Lagrangian analyses, we show the mixing patterns of the ionospheric responses and the formation

  1. Substorm-time ionospheric trough dynamics: Its evolution and relationship with FACs and convection flows

    NASA Astrophysics Data System (ADS)

    Zou, S.; Moldwin, M.; Lyons, L. R.; Nicolls, M. J.; Coster, A. J.

    2011-12-01

    Dynamics of the ionospheric mid-latitude and high-latitude troughs during substorms are investigated using multiple instruments, including GPS TEC and PFISR, with focus on the evolution of the troughs and their relationship with field-aligned currents (FACs) and convection flows. We describe the evolution of the mid-latitude trough during substorms. Its poleward wall shifts equatorward rapidly after substorm onset due to enhanced energetic electron precipitation. The mid-latitude trough narrows or even disappears during the expansion phase and can reappear during the recovery phase as auroral activity retreats poleward. This study demonstrates the potential of GPS TEC in detecting substorm related auroral activity and energetic particle precipitation on a regular basis. In addition, we find that the high-latitude trough can occur right after substorm onset east of the Harang reversal and that it can last for more than an hour. The termination of the high-latitude trough is usually associated with intrusion of auroral forms and accompanied by intensification of negative H perturbations. It has been a puzzle for a long time why high-latitude troughs predominantly occur just east of the Harang reversal in the post-midnight sector. We suggest that the high-latitude trough is associated with the formation of downward FACs of the substorm current system, which usually occur just east of the Harang reversal. We further discuss the effects of substorm related convection pattern, structured FACs, and precipitating particle species on creating the complex electron density variations in the subauroral and auroral regions.

  2. Line tying and cross-field plasma convection

    Microsoft Academic Search

    S. W. Fornaca

    1980-01-01

    The effects of line tying on the curvature-driven convection of plasma across magnetic field lines in open ended confinement systems were investigated. Line tying is defined as the electrical contact between the plasma and a conducting end wall. On the basis of existing theoretical models of the line tying process, the motion of the plasma in terms of measurable parameters

  3. New Forms of Convection in Galaxy Cluster Plasmas

    E-print Network

    Wurtele, Jonathan

    New Forms of Convection in Galaxy Cluster Plasmas (i.e., how do galaxy clusters boil?) Eliot · Motions slow & adiabatic: pressure equil, s ~ const gravity high s background fluid convectively unstable low entropy (s) #12;Cluster Entropy Profiles Schwarzschild criterion clusters are stable Radius (Rvir

  4. The response of plasma density to breaking inertial gravity wave in the lower regions of ionosphere

    SciTech Connect

    Tang, Wenbo, E-mail: Wenbo.Tang@asu.edu; Mahalov, Alex, E-mail: Alex.Mahalov@asu.edu [School of Mathematical and Statistical Sciences, Arizona State University, Tempe, Arizona 85287 (United States)] [School of Mathematical and Statistical Sciences, Arizona State University, Tempe, Arizona 85287 (United States)

    2014-04-15

    We present a three-dimensional numerical study for the E and lower F region ionosphere coupled with the neutral atmosphere dynamics. This model is developed based on a previous ionospheric model that examines the transport patterns of plasma density given a prescribed neutral atmospheric flow. Inclusion of neutral dynamics in the model allows us to examine the charge-neutral interactions over the full evolution cycle of an inertial gravity wave when the background flow spins up from rest, saturates and eventually breaks. Using Lagrangian analyses, we show the mixing patterns of the ionospheric responses and the formation of ionospheric layers. The corresponding plasma density in this flow develops complex wave structures and small-scale patches during the gravity wave breaking event.

  5. A climatological assessment of ionospheric travelling convection vortices using an automatic detection algorithm

    NASA Astrophysics Data System (ADS)

    Kotsiaros, S.; Stolle, C.; Friis-Christensen, E. A.; Matzka, J.

    2013-12-01

    Analysis of geomagnetic variometer data from the Greenland magnetometer array shows signatures of localized ionospheric travelling convection vortices (TCVs), which are commonly believed to be generated by compression or decompression of the magnetopause by changes in the solar wind dynamic pressure, flux transfer events, or magnetospheric Kelvin-Helmholtz instabilities. We present an algorithm for automatic detection of TCVs in Greenland magnetic data which is based on the short-time-average through long-time-average trigger (STA/LTA), an algorithm broadly used in weak-motion seismology. Results of their climatological assessment of their occurrence properties are discussed. In this paper, three years of magnetometer data, from 2010 to 2013, collected at twelve stations at the West coast of Greenland are analysed and TCV events are classified with respect to their intensity, duration and time of occurrence. Subsequently, they are correlated with values of the interplanetary magnetic field (IMF), solar wind velocity and geomagnetic indices. The results indicate that TCVs occur usually around magnetic local noon with a typical duration of approximately 15 to 30 minutes. TCV detection is clearly facilitated during times of low geomagnetic background activity.

  6. Phenomena associated with complex (dusty) plasmas in the ionosphere during high-speed meteor showers

    SciTech Connect

    Kopnin, S. I. [Institute for Dynamics of Geospheres, RAS, Moscow 119334 (Russian Federation); Popel, S. I. [Institute for Dynamics of Geospheres, RAS, Moscow 119334 (Russian Federation); Space Research Institute, RAS, Moscow 117997 (Russian Federation); Yu, M. Y. [Department of Physics, Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027, China and Institute for Theoretical Physics I, Ruhr University, D-44780 Bochum (Germany)

    2009-06-15

    Formation of dusty plasmas in the Earth's ionosphere at 80-120 km altitudes during high-speed meteor showers and its detectable manifestations are discussed. Emphasis is given to ground-based observations such as detection of low-frequency (<50 Hz) ionospheric radio noise, ground-based observations of infrasonic waves, and amplification of the intensity of green radiation at 557.7 nm from a layer at the 110-120 km altitude in the lower ionosphere. The physical processes responsible for these manifestations are considered.

  7. Ionospheric convection response to slow, strong variations in a Northward interplanetary magnetic field: A case study for January 14, 1988

    NASA Technical Reports Server (NTRS)

    Knipp, D. J.; Emery, B. A.; Richmond, A. D.; Crooker, N. U.; Hairston, M. R.; Cumnock, J. A.; Denig, W. F.; Rich, F. J.; De La Beaujardiere, O.; Ruohoniemi, J. M.

    1993-01-01

    We analyze ionospheric convection patterns over the polar regions during the passage of an interplanetary magnetic cloud on January 14, 1988, when the interplanetary magnetic field (IMF) rotated slowly in direction and had a large amplitude. Using the assimilative mapping of ionospheric electrodynamics (AMIE) procedure, we combine simultaneous observations of ionspheric drifts and magnetic perturbations from many different instruments into consistent patterns of high-latitude electrodynamics, focusing on the period of northward IMF. By combining satellite data with ground-based observations, we have generated one of the most comprehensive data sets yet assembled and used it to produce convection maps for both hemispheres. We present evidence that a lobe convection cell was embedded within normal merging convection during a period when the IMF B(sub y) and B(sub z) components were large and positive. As the IMF became predominantly northward, a strong reversed convection pattern (afternoon-to-morning potential drop of around 100 kV) appeared in the southern (summer) polar cap, while convection in the northern (winter) hemisphere became weak and disordered with a dawn-to-dust potential drop of the order of 30 kV. These patterns persisted for about 3 hours, until the IMF rotated significantly toward the west. We interpret this behavior in terms of a recently proposed merging model for northward IMF under solstice conditions, for which lobe field lines from the hemisphere tilted toward the Sun (summer hemisphere) drape over the dayside magnetosphere, producing reverse convection in the summer hemisphere and impeding direct contact between the solar wind and field lines connected to the winter polar cap. The positive IMF B(sub x) component present at this time could have contributed to the observed hemispheric asymmetry. Reverse convection in the summer hemisphere broke down rapidly after the ratio absolute value of B(sub y)/B(sub z) exceeded unity, while convection in the winter hemisphere strengthened. A dominant dawn-to-dusk potential drop was established in both hemispheres when the magnitude of B(sub y) exceeded that of B(sub z) with potential drops of the order of 100 kV, even while B(sub z) remained northward. The latter transition to southward B(sub z) produced a gradual intensification of the convection, but a greater qualitative change occurred at the transition through absolute value of B(sub y)/B(sub z) = 1 than at at the transition through B(sub z) = 0. The various convection patterns we derive under northward IMF conditions illustrate all possibilities previously discussed in the literature: nearly single-cell and multicell, distorted and symmetric, ordered and unordered, and sunward and antisunward.

  8. Changes of the electron concentration profile during local heating of the ionospheric plasma

    Microsoft Academic Search

    Nathan Blaunstein

    1996-01-01

    Using numerical simulation of a non-stationary problem of thermodiffusion and diffusive spreading of the electron component of the dense cold ionospheric plasma, the processes of formation and relaxation of strong disturbances of the electron temperature and concentration in the E- and F-regions of the middle-latitude ionosphere are examined, taking into account the altitudinal distribution of the electron transport coefficients. The

  9. Mid-latitude F-region ionosphere plasma stability in the presence of photoelectrons

    NASA Astrophysics Data System (ADS)

    Ivanov, V. B.; Trukhan, A. A.; Khazanov, G. V.

    1982-03-01

    Stability of the dayside ionospheric plasma containing photoelectrons relative to the excitation of its own potential oscillations is studied. It is assumed that the plasma thermal electrons have the equilibrium distribution while the photoelectrons possess a complex nonmonotonic energy spectrum. The plasma oscillation increments, which take into account a collision damping in the ionospheric F-region, have been analyzed numerically. Our results show that the F-region is stable and disagrees with the results and conclusions of Blomberg (1975). A discussion is given where the disagreement originates.

  10. On the generation of enhanced sunward convection and transpolar aurora in the high-latitude ionosphere by magnetic merging

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Baker, J. B. H.; Petrinec, S. M.; Wang, H.; Rich, F. J.; Kuznetsova, M.; Dunlop, M. W.; RèMe, H.; Greenwald, R. A.; Frey, H. U.; Lühr, H.; Ergun, R. E.; Balogh, A.; Carlson, C. W.

    2005-11-01

    The IMAGE Wideband Imaging Camera (WIC) instrument observed the duskside development of an oval-aligned transpolar auroral arc (TPA) in the Northern Hemisphere (NH) on 16 December 2001 during strong IMF ?B? ˜ 18 nT and a generally steady ˜56° clock angle (positive IMF By and Bz). Observational evidence suggests that the dayside part of the duskside TPA formed due to quasi-continuous merging between the IMF and the lobe magnetic field tailward of the cusp while the nightside part is associated with the Harang discontinuity. The low-altitude CHAMP satellite confirms an upward northward IMF Bz (NBZ) field-aligned current (FAC) over the dayside TPA while associating a downward NBZ current with the region of diminished WIC emissions in between the auroral oval and the TPA. DMSP F14 suggests that the dayside region of the downward NBZ current coincides with precipitating magnetosheath-like ions of reversed energy-latitude dispersion consistent with high-latitude reconnection. SuperDARN observes enhanced ionospheric sunward flows generally centered between the oppositely directed NBZ currents. We associate these flows with a clockwise lobe convection vortex and the dayside part of the TPA. The nightside TPA, however, is related to stagnant or antisunward flow and the upward FAC region of the Harang discontinuity. Cluster observations confirm the simultaneous presence of rotational discontinuities across the duskside magnetopause with changes in the magnetosheath plasma velocity that indicate an active merging region poleward of Cluster. A global MHD simulation generates sunward flow between a pair of opposite FACs on either side of a lobe reconnection site near (X, Y, Z)GSM = (-4.7, 5.4, 10.2) RE thus conforming with Cluster and SuperDARN expectations. The sense of these FACs agrees with the low-altitude NBZ observations.

  11. 3D Global MHD Simulation of the Saturn Magnetospheric Plasma Interaction with Titan's Ionosphere

    Microsoft Academic Search

    Yingjuan Ma; A. F. Nagy; T. E. Cravens; G. Toth; F. J. Crary; A. J. Coates; M. K. Dougherty

    2006-01-01

    The interaction between Titan's ionosphere and its surrounding plasma is simulated using our 3D multi-species MHD model.We compare the simulation results with the observations obtained during the T9 flyby, using the upstream plasma parameters measured during the flyby. The Hall term (JXB) is also included in the model to investigate the ion gyro-radii effect.

  12. Excitation of the lower oblique resonance by an artificial plasma jet in the ionosphere

    NASA Astrophysics Data System (ADS)

    Thiel, J.; Storey, L. R. O.; Bauer, O. H.; Jones, D.

    1984-04-01

    Aboard the Porcupine rockets, bursts of noise were detected in the electron whistler range during the operation of a xenon plasma gun on a package ejected from the main payload. These observations can be interpreted in terms of excitation of the lower oblique resonance by instabilities associated with the motion of the xenon ion beam through the ionospheric plasma.

  13. Whistler wave-induced ionospheric plasma turbulence: Source mechanisms and remote sensing

    NASA Astrophysics Data System (ADS)

    Pradipta, R.; Rooker, L. A.; Whitehurst, L. N.; Lee, M. C.; Ross, L. M.; Sulzer, M. P.; Gonzalez, S.; Tepley, C.; Aponte, N.; See, B. Z.; Hu, K. P.

    2013-10-01

    We report a series of experiments conducted at Arecibo Observatory in the past, aimed at the investigation of 40.75 kHz whistler wave interactions with ionospheric plasmas and the inner radiation belts at L=1.35. The whistler waves are launched from a Naval transmitter (code-named NAU) operating in Aguadilla, Puerto Rico at the frequency and power of 40.75 kHz and 100 kW, respectively. Arecibo radar, CADI, and optical instruments were used to monitor the background ionospheric conditions and detect the induced ionospheric plasma effects. Four-wave interaction processes produced by whistler waves in the ionosphere can excite lower hybrid waves, which can accelerate ionospheric electrons. Furthermore, whistler waves propagating into the magnetosphere can trigger precipitation of energetic electrons from the radiation belts. Radar and optical measurements can distinguish wave-wave and wave-particle interaction processes occurring at different altitudes. Electron acceleration by different mechanisms can be verified from the radar measurements of plasma lines. To facilitate the coupling of NAU-launched 40.75 kHz whistler waves into the ionosphere, we can rely on naturally occurring spread F irregularities to serve as ionospheric ducts. We can also use HF wave-created ducts/artificial waveguides, as demonstrated in our earlier Arecibo experiments and recent Gakona experiments at HAARP. The newly constructed Arecibo HF heater will be employed in our future experiments, which can extend the study of whistler wave interactions with the ionosphere and the magnetosphere/radiation belts as well as the whistler wave conjugate propagation between Arecibo and Puerto Madryn, Argentina.

  14. Observations of nightside auroral plasma upflows in the F-region and topside ionosphere

    NASA Astrophysics Data System (ADS)

    Foster, C.; Lester, M.

    1996-12-01

    Observations from the special UK EISCAT program UFIS are presented. UFIS is a joint UHF-VHF experiment, designed to make simultaneous measurements of enhanced vertical plasma flows in the F-region and topside ionospheres. Three distinct intervals of upward ion flow were observed. During the first event, upward ion fluxes in excess of 1013 m-2 s-1 were detected, with vertical ion velocities reaching 300 m s-1 at 800 km. The upflow was associated with the passage of an auroral arc through the radar field of view. In the F-region, an enhanced and sheared convection electric field on the leading edge of the arc resulted in heating of the ions, whilst at higher altitudes, above the precipitation region, strongly enhanced electron temperatures were observed; such features are commonly associated with the generation of plasma upflows. These observations demonstrate some of the acceleration mechanisms which can exist within the small-scale structure of an auroral arc. A later upflow event was associated with enhanced electron temperatures and only a moderate convection electric field, with no indication of significantly elevated ion tem- peratures. There was again some evidence of F-region particle precipitation at the time of the upflow, which exhibited vertical ion velocities of similar magnitude to the earlier upflow, suggesting that the behaviour of the electrons might be the dominant factor in this type of event. A third upflow was detected at altitudes above the observing range of the UHF radar, but which was evident in the VHF data from 600 km upwards. Smaller vertical velocities were observed in this event, which was apparently uncorrelated with any features observed at lower altitudes. Limitations imposed by the experimental conditions inhibit the interpretation of this event, although the upflow was again likely related to topside plasma heating. Acknowledgements. We would like to thank the director and staff of EISCAT for the data used in this study. EISCAT is supported by the scientific research councils of Finland, France, Germany, Norway, Sweden and the UK. We would like to express our special thanks to A. P. van Eyken and U. P. Løvhaug for their cooperation and assistance in running the IPS campaigns and to W. P. Wilkinson for discussions on fast-stream/slow-stream interaction regions. Two of us (ARB and PJM) are supported by PPARC. Topical Editor D. Alcaydé thanks J. F. Mckenzie and M. Pick for their help in evaluating this paper.--> Correspondence to: A. R. Breen-->

  15. Convective Instability of a Plasma Slab in a Magnetic Field

    Microsoft Academic Search

    Bhimsen K Shivamoggi; Mahinder S Uberoi

    1983-01-01

    Convective instability of a plasma slab (contained between two metal walls) subject to a longitudinal applied magnetic field is considered. The method of solution is akin to the variational method introduced by Chandrasekhar in 1961. It is found that the plasma is stable for wave-numbers less than a certain value kc.

  16. Convective instability of a plasma slab in a magnetic field

    Microsoft Academic Search

    B. K. Shivamoggi; M. S. Uberoi; Mahinder; S. Uberoi

    1980-01-01

    Convective instability of a plasma slab (contained between two metal walls) subject to a longitudinal external magnetic field is studied. The results show that (1) increase in the ionization rate Z causes a reduction in the stability of the plasma; (2) the instability persists in the limit k approaching 0.

  17. Region 2 field-aligned currents and earthward penetration of the electron and ion plasma sheet obtained from RCM simulations with a modified Dungey magnetic field solver, and comparison with observations in ionosphere and magnetosphere

    NASA Astrophysics Data System (ADS)

    Gkioulidou, M.; Wang, C.; Lyons, L. R.

    2011-12-01

    Ionospheric conductivity and field aligned currents (FAC) are two of the most important factors that control the magnetosphere - ionosphere (M-I) coupling. The relative location between conductivity and FAC strongly affect the spatial distribution of convection electric field, including the Harang reversal and Sub-Auroral Polarization Streams that are crucial to development of substorms and storms. The night-side conductivity strongly depends on electron precipitation, and thus the electron plasma sheet and precipitation rate. On the other hand, Region 2 (R2) FAC are associated with pressure gradients in the near-Earth magnetosphere built up by plasma sheet ions. To understand this aspect of M-I coupling, we have run simulations with the Rice Convection Model (RCM), integrated with a modified Dungey magnetic field solver for equatorial force balance, to investigate the earthward penetration of plasma sheet protons and electrons of different energies into the near-Earth magnetosphere under weak and enhanced convection. We have investigated in our simulations how different precipitation rate affects the relative locations of conductivity and FAC and the resulting M-I coupling. We evaluate these simulation results by comparing the plasma sheet ions and electrons and their relative earthward edges with in situ THEMIS statistical results, and by comparing the simulated precipitating electron energy fluxes, different ion and electron equatorward precipitation boundaries, as well as their locations relative to R2 FAC in ionosphere, with previous published statistical DMSP studies [Newell et al., 2009; Ohtani et al., 2010].

  18. Formation of the Harang reversal and its dependence on plasma sheet conditions: Rice convection model simulations

    NASA Astrophysics Data System (ADS)

    Gkioulidou, Matina; Wang, Chih-Ping; Lyons, Larry R.; Wolf, Richard A.

    2009-07-01

    The goal of this paper is to understand the formation of the Harang reversal and its association with the region 2 field-aligned current (FAC) system, which couples the plasma sheet transport to the ionosphere. We have run simulations with the Rice convection model (RCM) using the Tsyganenko 96 magnetic field model and realistic plasma sheet particle boundary conditions on the basis of Geotail observations. Our results show that the existence of an overlap in magnetic local time (MLT) of the region 2 upward and downward FAC is necessary for the formation of the Harang reversal. In the overlap region the downward FAC, which is located at lower latitudes, is associated with low-energy ions that penetrate closer to Earth toward the dawn side, while the upward FAC, which is located at higher latitudes, is associated with high-energy ions. Under the same enhanced convection we compare the Harang reversal resulting from a hotter and more tenuous plasma sheet with the one resulting from a colder and denser plasma sheet. For the former case the shielding of the convection electric field is less efficient than for the latter case, allowing low-energy protons to penetrate further earthward, resulting in a Harang reversal that extends to lower latitudes, expands wider in MLT, and is located further equatorward than the upward FAC peak and the conductivity peak. The return flows of the Harang reversal in the hot and tenuous case are located in a low conductivity region. This leads to an enhancement of these westward flows, resulting in subauroral polarization streams (SAPS).

  19. Correlation between the global occurrences of ionospheric irregularities and deep atmospheric convective clouds in the intertropical convergence zone (ITCZ)

    NASA Astrophysics Data System (ADS)

    Su, Shin-Yi; Wu, Chung Lung; Liu, Chao Han

    2014-12-01

    To study the seeding mechanism of ionospheric irregularity occurrences, a correlation study has been carried out between the global monthly/latitudinal (m/l) distributions of irregularity occurrences and the deep atmospheric convective clouds in the intertropical convergence zone (ITCZ) indicated by the outgoing longwave radiation (OLR) measurements. Seven longitude sectors - the African, Indian, West Pacific, Central Pacific, East Pacific, South American, and Atlantic sectors - are selected to study the correlations between the two distributions. The results indicate that good correlations exist only in the South American sector and to some extent in the African sector. For the other five sectors, no correlations are found in the m/l distributions between the irregularities and OLRs. This implies that the gravity wave induced in the ITCZ cannot be the sole seeding agent for the Rayleigh-Taylor (RT) instability in the global irregularity occurrences every season. We suspect that the post-sunset ionospheric electrodynamic perturbations could be the prevailing seeds for the RT instability globally year long. Together with the favorable post-sunset ionospheric condition, the global m/l distributions of irregularity occurrences could be adequately explained.

  20. Plasma convection and line-tying

    Microsoft Academic Search

    S. Fornaca

    1983-01-01

    The directed motion of a low-? plasma across a toroidal magnetic field is examined as the degree of electrical contact between the plasma and a conducting end wall (line-tying) is varied in a controlled manner. Experimentally, little difference is found between the motion of a completely isolated plasma and that of a plasma in contact with a wall that does

  1. Yosemite Conference on Ionospheric Plasma in the Magnetosphere: Sources, Mechanisms and Consequences, meeting report

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Burch, J. L.; Klumpar, D. M.; Moore, T. E.; Waite, J. H., Jr.

    1987-01-01

    The sixth biennial Yosemite topical conference and the first as a Chapman Conference was held on February 3 to 6, 1986. Due to the recent changes in our perception of the dynamics of the ionospheric/magnetospheric system, it was deemed timely to bring researchers together to discuss and contrast the relative importance of solar versus terrestrial sources of magnetospheric plasma. Although the solar wind was once thought to dominate the supply of plasma in the Earth's magnetosphere, it is now thought that the Earth's ionosphere is a significant contributor. Polar wind and other large volume outflows of plasma have been seen at relatively high altitudes over the polar cap and are now being correlated with outflows found in the magnetotail. The auroral ion fountain and cleft ion fountain are examples of ionospheric sources of plasma in the magnetosphere, observed by the Dynamics Explorer 1 (DE 1) spacecraft. The conference was organized into six sessions: four consisting of prepared oral presentations, one poster session, and one session for open forum discussion. The first three oral sessions dealt separately with the three major topics of the conference, i.e., the sources, mechanisms, and consequences of ionospheric plasma in the magnetosphere. A special session of invited oral presentations was held to discuss extraterrestrial ionospheric/magnetospheric plasma processes. The poster session was extended over two evenings during which presenters discussed their papers on a one-on-one basis. The last session of the conferences was reserved for open discussions of those topics or ideas considered most interesting or controversial.

  2. Numerical simulation of the plasma thermal disturbances during ionospheric modification experiments at the SURA heating facility

    NASA Astrophysics Data System (ADS)

    Belov, Alexey; Huba, J. D.

    indent=1cm We present the results of numerical simulation of the near-Earth plasma disturbances produced by resonant heating of the ionospheric F-region by high-power HF radio emission from the SURA facility. The computational model is based on the modified version of the SAMI2 code (release 1.00). The model input parameters are appropriated to the conditions of the SURA-DEMETER experiment. In this work, we study the spatial structure and temporal characteristics of stimulated large-scale disturbances of the electron number density and temperature. It is shown that the stimulated disturbances are observed throughout the ionosphere. Disturbances are recorded both in the region below the pump wave reflection level and in the outer ionosphere (up to 3000 km). At the DEMETER altitude, an increase in the ion number density is stipulated by the oxygen ions O (+) , whereas the number density of lighter H (+) ions decreases. A typical time of the formation of large-scale plasma density disturbances in the outer ionosphere is 2-3 min. After the heater is turned off, the disturbances relaxation time is approximately 30 min. The simulation results are important for planning future promising experiments on the formation of ionospheric artificial density ducts. This work was supported by the Russian Foundation for Basic Research (project No. 12-02-00747-a), and the Government of the Russian Federation (contract No. 14.B25.31.0008).

  3. Some necessary conditions for a critical velocity interaction between the ionospheric plasma and a xenon cloud

    Microsoft Academic Search

    I. Axnas

    1980-01-01

    The condition for an experiment to study the critical ionization velocity effect in the interaction between a xenon cloud, released from a satellite, and the ionospheric plasma are investigated. The model used is based on the assumption that there exists an effective process that transfers the energy that is available in the relative motion to the electrons. Some necessary conditions

  4. Some necessary parameters for a critical velocity interaction between the ionospheric plasma and a Xenon cloud

    Microsoft Academic Search

    I. Axnaes

    1979-01-01

    The conditions for an experiment to study the critical ionization velocity effect in the interaction between a Xenon cloud, released from a satellite, and the ionospheric plasma, are investigated. The model used is based on the assumption that there exists an effective process that transfers the energy, that is available in the relative motion, to the electrons. Some necessary conditions

  5. A PLASMA INSTABILITY RESULTING IN FIELD-ALIGNED IRREGULARITIES IN THE IONOSPHERE

    Microsoft Academic Search

    D. T. Farley; D. T. Jr

    1963-01-01

    A theory of the two-stream ion wave instability in a plasma is developed ; that takes into account both the effect of collisions of the ions and electrons ; with neutral particles and the presence of a uniform magnetic field. Applying ; the results to the ionosphere, it is found that irregularities of ionization ; density should arise spontaneously in

  6. Yearly variations of global plasma densities in the topside ionosphere at middle and low latitudes

    Microsoft Academic Search

    Libo Liu; Biqiang Zhao; Weixing Wan; S. Venkartraman; Man-Lian Zhang; X. Yue

    2007-01-01

    In this paper, the 10-year (1996-2005) measurements of total ion density (N i ) from the Defense Meteorological Satellite Program (DMSP) spacecraft at 0930 and 2130 LT have been analyzed to investigate the yearly variations of global plasma densities in the topside ionosphere at magnetic latitudes from 60°S to 60°N. Results indicate that there are strong yearly variations in the

  7. Evolution of a stratified plasma structure induced by local heating of the ionosphere

    Microsoft Academic Search

    N. Blaunstein

    1997-01-01

    A three-dimensional non-stationary problem of striated plasma density structure formation and relaxation during and after thermal heating of the F-layer of the ionosphere by powerful radio waves is investigated both numerically and analytically. A theoretical analysis is carried out, taking account of quasi-regular gradients of the concentration of the background plasma, ambient geophysical factors, as well as the altitudinal dependence

  8. A model of ionospheric image structure underneath a braking, cross-field plasma jet

    NASA Technical Reports Server (NTRS)

    Jacobson, Abram R.; Simons, David J.; Nalesso, Gianfranco

    1987-01-01

    A plasma jetting across the geomagnetic field above the ionosphere tends to brake by ohmic dissipation of Pedersen currents. The braking can affect the ionosphere underneath if the associated Pedersen drifts are intense and prolonged enough to cause cumulative image structuring. Here, such image structuring is studied for the parameter regime of forthcoming releases from the Combined Release and Radiation Effects Satellite, involving photoionization of kilograms of barium vapor moving at orbital velocity. The resultant structuring in the upper E-region offers possible diagnostic telltales of the braking process.

  9. Global ionospheric weather

    SciTech Connect

    Decker, D.T.; Doherty, P.H.

    1994-02-28

    In the last year, the authors have studied several issues that are critical for understanding ionospheric weather. Work on global F-region modeling has consisted of testing the Phillips Laboratory Global Theoretical Ionosphere Model. Comparisons with both data and other theoretical models have been successfully conducted and are ongoing. GPS observations, as well as data analysis, are also ongoing. Data have been collected for a study on the limitations in making absolute ionospheric measurements using GPS. Another study on ionospheric variability is the first of its kind using GPS data. The observed seasonal total electron content behavior is consistent with that determined from the Faraday rotation technique. Work on the FAA's Phase 1 Wide Area Differential GPS (WADGPS) Satellite Navigation Testbed Experiment also continues. Initial results indicate that stations using operational WADGPS should be located no greater than 430 km apart. Work comparing the authors electron-proton-H atom model to both observations and other models has been generally successful. They have successfully modeled the creation of high-latitude large-scale plasma structures using two separate mechanisms (time-varying global convection and meso-scale convection events).

  10. Stormtime coupling of the ring current, plasmasphere, and topside ionosphere: Electromagnetic and plasma disturbances

    NASA Astrophysics Data System (ADS)

    Mishin, E. V.; Burke, W. J.

    2005-07-01

    We compare plasma and field disturbances observed in the ring current/plasmasphere overlap region and in the conjugate ionosphere during the magnetic storm of 5 June 1991. Data come from the Combined Release and Radiation Effects Satellite (CRRES) flying in a geostationary transfer orbit and three satellites of the Defense Meteorological Satellite Program (DMSP) series in Sun-synchronous polar orbits. In the region between ring current nose structures and the electron plasma sheet, CRRES detected wave-like features in local electric and magnetic fields, embedded in structured cold plasmas. Mapped to the ionosphere, these fields should reflect structuring within subauroral plasma streams (SAPS). Indeed, during the period of interest, DMSP F8, F9, and F10 satellites observed highly structured SAPS in the evening ionosphere at topside altitudes. They were collocated with precipitating ring current ions, enhanced fluxes of suprathermal electrons and ions, elevated electron temperatures, and irregular plasma density troughs. Overall, these events are similar to electromagnetic structures observed by DMSP satellites within SAPS during recent geomagnetic storms (Mishin et al., 2003, 2004). Their features can be explained in terms of Alfvén and fast magnetosonic perturbations. We developed a scenario for the formation of elevated electron temperatures at the equatorward side of the SAPS. It includes a lower-hybrid drift instability driven by diamagnetic currents, consistent with strong lower- and upper-hybrid plasma wave activity and intense fluxes of the low-energy electrons and ions near the ring current's inner edge.

  11. Global Observations of Equatorial Ionospheric Plasma Drift Speeds

    Microsoft Academic Search

    T. J. Immel; H. U. Frey; S. B. Mende; E. Sagawa

    Abstract Space-based measurements,from an imager aboard the high-apogee NASA-IMAGE satellite allows for global-scale observations of nightside ionospheric densities and structure. Such a view cannot be provided by imagers in near earth orbit or based on the ground. The IMAGE Spectroscopic Imager (SI) isolates the Far-ultraviolet (FUV) O I 135.6-nm emission which is produced,through radiative recombination,of O,. These observations clearly show

  12. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 98, NO. All, PAGES 19,273-19,292, NOVEMBER 1, 1993 IonosphericConvectionResponse Slow,StrongVariationsin a Northward

    E-print Network

    Lockwood, Mike

    IonosphericConvectionResponse Slow,StrongVariationsin a Northward Interplanetary Magnetic Field' A Case- sphericelectrodynamics(AMIE) procedure,wecombinesimultaneousobservationsofionospheric drifts and magnetic perturbations[Richmondand Kamide, 1988; Richmond,1992] to the data from theseinstru- Department of Physics,U.S. Air Force

  13. Titan's Topside Ionospheric Composition: Cassini Plasma Spectrometer Ion Mass spectrometer Measurements

    NASA Astrophysics Data System (ADS)

    Sittler, E. C., Jr.; Hartle, R. E.; Ali, A.; Cooper, J. F.; Lipatov, A. S.; Simpson, D. G.; Sarantos, M.; Chornay, D. J.

    2014-12-01

    In [1] the first quantitative evidence of ionospheric outflows (r > 10,000 km) coming from Titan was given using the Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS) data for the T9 flyby. Later in [2] similar outflows were shown for T63 and T75. In [3] evidence for ionospheric outflows for T15 was given and [4] showed evidence of outflows for T41. Normally, the CAPS IMS cannot be used to measure Titan's relatively dense ionosphere because the IMS has high sensitivity to measure the more tenuous plasmas of Saturn's magnetosphere and its detectors will experience count rates beyond their maximum allowed rates, therefore the IMS is configured not to measure the ionospheric plasma. But, whenever there are high altitude Titan wake flybys the ion densities are low enough so the CAPS IMS can measure these ionospheric outflows and their corresponding composition characteristic of the topside ionosphere (i.e., composition freezes in above the exobase) using its unique compositional capabilities. For example, the IMS can distinguish against specific ion types such as hydrocarbon, nitrile and water group ions due fragmentation of molecular ions within the instrument (i.e., incident ions strikes ultra-thin carbon foils at 14.6 kV or higher with exiting fragments such C+,0,-, N+,0, O+,0,-1). The other ionospheric instruments only measure the ion mass-per-charge (M/Q), while the CAPS IMS measures both the ion M/Q and its fragments. Specific attention will be given to such ions as NH4+, N+, O+, CH4+, C2H5+, HCNH+ and C3H7+. These results may impose important constraints upon Titan's ionospheric water group, hydrocarbon and nitrile ion chemistry. Are NH4+ ions present as indicated by INMS at 1100 km altitude and/or water group ions? Our work has concentrated on the T15 flyby. Estimates of the NH4+, N+ and O+ abundances presently have upper values < 20% of the total ion density with actual abundances and their uncertainties to be given. [1] Sittler, E.C. Jr., et al., (2010), Planet. Space Sci., 58, 327-350. [2] Coates, A.J., et al., (2012), J. Geophys. Res., 117, A05324, doi:10.1029/2012JA017595. [3] Sillanpää et al., (2011), J. Geophys. Res., 116, A07223, doi:10.1029/2011JA016443. [4] Sittler, E. C., Jr., et al., (2013), Fall AGU Abstract P53C-1880, San Francisco, CA.

  14. Application of the coded long-pulse technique to plasma line studies of the ionosphere

    NASA Technical Reports Server (NTRS)

    Djuth, Frank T.; Sulzer, Michael P.; Elder, John H.

    1994-01-01

    Recently, the coded long-pulse radar technique was tested at Arecibo Observatory, Puerto Rico using photoelectron-enhanced plasma lines in the daytime ionosphere. The technique immediately proved to be a powerful diagnostic tool for studying natural ionospheric phenomena. Our initial observations indicate that extremely accurate measurements of absolute electron density (0.01 to 0.03% error bars) can be achieved with an altitude resolution of 150 m and a temporal resolution of approx. 2 s. In addition, the technique provides information about electron density structure within a 150-m altitude cell and yields parameters from which the energy spectrum of suprathermal electrons (equal to or greater than 5 eV) can be deduced. Our earliest measurements are used to illustrate applications of the coded long-pulse technique to several aeronomic/ionsospheric areas of current interest. These include studies of neutral wave motions in the lower thermosphere, measurements of ion composition in the F(sub 1) region/upper ionosphere, and investigations of electron-gas thermal balance and photoelectron energy loss processes. The technique can be utilized to examine irregularity formation in the F region, probe electron acceleration processes in ionospheric modification experiments, verify the magnetic field dependence of Langmuir wave damping, and more generally test higher order corrections suggested for the Langmuir dispersion relation. It is anticipated that the latter tests will facilitate measurements of ionospheric currents.

  15. Dust Acoustic Solitons in the Dusty Plasma of the Earth's Ionosphere

    SciTech Connect

    Kopnin, S.I.; Kosarev, I.N.; Popel, S.I. [Institute of Geosphere Dynamics, Russian Academy of Sciences, Leninskii pr. 38-1, Moscow, 119334 (Russian Federation); Yu, M.Y. [Institute for Theoretical Physics I, Ruhr University Bochum, D-44780 Bochum (Germany)

    2005-03-15

    Stratified structures that are observed at heights of 80-95 km in the lower part of the Earth's ionosphere are known as noctilucent clouds and polar mesosphere summer echoes. These structures are thought to be associated with the presence of vast amounts of charged dust or aerosols. The layers in the lower ionosphere where there are substantial amounts of dust are called the dusty ionosphere. The dust grains can carry a positive or a negative charge, depending on their constituent materials. As a rule, the grains are ice crystals, which may contain metallic inclusions. A grain with a sufficiently large metallic content can acquire a positive charge. Crystals of pure ice are charged negatively. The distribution of the dust grains over their charges has a profound impact on the ionizational and other properties of dust structures in the dusty ionosphere. In the present paper, a study is made of the effect of the sign of the dust charge on the properties of dust acoustic solitons propagating in the dusty ionosphere. It is shown that, when the dust charge is positive, dust acoustic solitons correspond to a hill in the electron density and a well in the ion density. When the dust is charged negatively, the situation is opposite. These differences in the properties of dust acoustic solitons can be used to diagnose the plasmas of noctilucent clouds and polar mesosphere summer echoes.

  16. Plasma waves observed at low altitudes in the tenuous Venus nightside ionosphere

    NASA Technical Reports Server (NTRS)

    Strangeway, R. J.; Russell, C. T.; Ho, C. M.; Brace, L. H.

    1993-01-01

    The Pioneer Venus (PV) Orbiter Electric Field Detector (OEFD) measured many plasma wave bursts throughout the low altitude ionosphere during the final entry phase of the spacecraft. Apart from 100 Hz bursts observed at very low altitudes (approx. 130 km), the bursts fall into two classes. The first of these is a wideband signal that is observed in regions of low magnetic field, but average densities, in comparison to the prevailing ionospheric condition. This wideband signal is not observed in the 30 kHz channel of the OEFD, but is resricted to the 5.4 kHz channel and lower. Since these bursts are observed with roughly constant burst rate above 160 km altitude, we attribute them to ion acoustic mode waves generated by precipitating solar wind electrons. The second type of signal is restricted to 100 Hz only, and is observed in the regions of low electron beta, consistent with whistler-mode waves. These waves could be generated by lightning in the Venus atmosphere if the vertical component of the magnetic field greater than 3.6 nT. Because the ionosphere is very different during the entry phase, compared to the ionosphere as observed early in the Pioneer Venus mission, any conclusions regarding the source of the plasma waves detected during entry phase cannot be applied directly to the earlier observations.

  17. Probing the ionosphere with rockets and radio waves: Studies of plasma waves and instabilities in the upper atmosphere

    Microsoft Academic Search

    P. A. Bernhardt

    2011-01-01

    The ionosphere is a low temperature (0.1 eV) and low-beta plasma layer that surrounds the Earth and affects a wide range of radio systems that involve communications, navigation, and radar. The unmodified ionosphere is in an equilibrium state defined by the balance of production, transport and loss of plasma subject to variations in solar irradiation and other natural effects. Artificial

  18. Radar probing of ionospheric plasmas precisely confirms linear kinetic plasma theory (Hannes Alfvén Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Farley, Donald

    2010-05-01

    In 1958 W. E. Gordon first suggested that huge radars could probe the ionosphere via scattering from independent electrons, even though the radar cross section of a single electron is only 10-28 m2. This suggestion quickly led to the construction of two enormous radars in the early 1960s, one near Lima, Peru, and one near Arecibo, Puerto Rico. It soon became apparent that the theory of this scatter was more complicated than originally envisaged by Gordon. Although the new theory was more complicated, it was much richer: by measuring the detailed shape of the Doppler frequency spectrum (or alternatively the signal autocorrelation function, the ACF), a radar researcher could determine many, if not most, of the parameters of interest of the plasma. There is now a substantial network of major radar facilities scattered from the magnetic equator (Peru) to the high arctic latitudes (Svalbard and Resolute Bay), all doing important ionospheric research. The history of what is now called Incoherent Scatter (even though it is not truly incoherent) is fascinating, and I will touch on a few highlights. The sophisticated radar and data processing techniques that have been developed are also impressive. In this talk, however, I want to focus mainly on the details of the theory and on how the radar observations have confirmed the predictions of classical linear plasma kinetic theory to an amazingly high degree of precision, far higher than has any other technique that I am aware of. The theory can be, and has been, developed from two very different points of view. One starts with 'dressed particles,' or Coulomb 'clouds' around ions and electrons moving with a Maxwellian velocity distribution; the second starts by considering all the charged particles to be made up of a spectrum of density plane waves and then invokes a generalized version of the Nyquist Noise Theorem to calculate the thermal amplitudes of the waves. Both approaches give exactly the same results, results that allow us to predict exactly the scattered power and Doppler spectrum for any given set of plasma parameters (e.g., electron and ion temperatures, ionic composition, mean drifts and currents, the geomagnetic field, and particle collisions). So far, these predictions have not failed, although in recent years we have had to resort to numerical simulations to do a proper calculation of electron Coulomb collisions when the radar beam is pointed very nearly perpendicular to the magnetic field. This is because no analytic way has yet been found to properly apply the Fokker-Planck Coulomb collision model to the scattering process. Of course the theory predicts the spectrum, given all the plasma parameters, when what we really want to do in ionospheric research is the inverse, namely find the parameters, given the radar data. This inverse process can be quite difficult to do optimally if there are too many unknown parameters. Statistical inverse theory can require enormous computing power, but progress is being made.

  19. Real-time tracking and targeting computations and rocket vehicle aeroballistics for the PLACES ionospheric plasma test series

    NASA Astrophysics Data System (ADS)

    Rollstin, L. R.

    The PLACES (Position Location And Communication Effects Simulations) test program, conducted in December 1980 at Eglin Gulf Test Range, involved a series of ionospheric releases of barium/barium-nitrate vapor. The Defense Nuclear Agency sponsored program investigated effects of a structured ionospheric plasma (similar to that produced by a high-altitude nuclear explosion) on satellite navigation systems and provided in situ measurement of plasma structure. Terrier-Tomahawk rocket systems boosted the barium payloads, beacon payloads (plasma occultation experiment), and probe payloads (plasma in situ measurement). Drifting plasma tracking procedures, beacon- and probe-vehicle targeting procedures, and vehicle flight test results are presented.

  20. Propagation of Alfvén surface waves along the ionospheric plasma slab with the effect of gravity

    NASA Astrophysics Data System (ADS)

    Rathinavelu, G. D.; Sivaraman, M.

    2012-02-01

    Ionospheric regions connecting the neutral gas atmosphere have been considered to be an incompressible plasma slab surrounded by incompressible plasma on one side and neutral gas on the other side. The effect of gravity on Alfvén surface waves in the slab geometry is studied. As a special case, the propagation of ASW along the plasma-neutral gas interface is also discussed. The existence of two modes of surface waves has been identified and their characteristic behaviour affected by the gravity has been discussed.

  1. Linking Plasma Conditions in the Magnetosphere with Ionospheric Signatures

    NASA Technical Reports Server (NTRS)

    Rastaetter, Lutz; Kozyra, Janet; Kuznetsova, Maria M.; Berrios, David H.

    2012-01-01

    Modeling of the full magnetosphere, ring current and ionosphere system has become an indispensable tool in analyzing the series of events that occur during geomagnetic storms. The CCMC has a full model suite available for the magnetosphere, together with visualization tools that allow a user to perform a large variety of analyses. The January, 21, 2005 storm was a moderate-size storm that has been found to feature a large penetration electric field and unusually large polar caps (low-latitude precipitation patterns) that are otherwise found in super storms. Based on simulations runs at CCMC we can outline the likely causes of this behavior. Using visualization tools available to the online user we compare results from different magnetosphere models and present connections found between features in the magnetosphere and the ionosphere that are connected magnetically. The range of magnetic mappings found with different models can be compared with statistical models (Tsyganenko) and the model's fidelity can be verified with observations from low earth orbiting satellites such as DMSP and TIMED.

  2. Space weather. Ionospheric control of magnetotail reconnection.

    PubMed

    Lotko, William; Smith, Ryan H; Zhang, Binzheng; Ouellette, Jeremy E; Brambles, Oliver J; Lyon, John G

    2014-07-11

    Observed distributions of high-speed plasma flows at distances of 10 to 30 Earth radii (R(E)) in Earth's magnetotail neutral sheet are highly skewed toward the premidnight sector. The flows are a product of the magnetic reconnection process that converts magnetic energy stored in the magnetotail into plasma kinetic and thermal energy. We show, using global numerical simulations, that the electrodynamic interaction between Earth's magnetosphere and ionosphere produces an asymmetry consistent with observed distributions in nightside reconnection and plasmasheet flows and in accompanying ionospheric convection. The primary causal agent is the meridional gradient in the ionospheric Hall conductance which, through the Cowling effect, regulates the distribution of electrical currents flowing within and between the ionosphere and magnetotail. PMID:25013068

  3. Morphology of the postsunset vortex in the equatorial ionospheric plasma drift

    NASA Astrophysics Data System (ADS)

    Lee, Woo Kyoung; Kil, Hyosub; Kwak, Young-Sil; Paxton, Larry J.

    2015-01-01

    postsunset vortex in the equatorial ionosphere exhibits clockwise plasma motions after sunset in longitude (time) and altitude coordinates when the equatorial ionosphere is viewed looking northward. We describe the typical morphology of the postsunset vortex using incoherent scatter radar observations at Jicamarca in Peru during the previous solar maximum (2000-2002). A pronounced vortical plasma motion appears around 1700 LT along with the onset of the prereversal enhancement (PRE). The center of this vortex is located near an altitude of 270 km. A smaller-scale vortex also appears about 0.5 ~ 1 h later at higher altitudes. However, the morphology and occurrence time of this small vortex depend on the characteristics of the coherent backscatter region. We find that the earlier vortex is the major feature of the postsunset vortices because it is repeatable, associated with the PRE, and independent to the occurrence of the coherent backscatter region.

  4. Numerical researches of large-scale plasma currents in the top ionosphere and magnetosphere

    Microsoft Academic Search

    E. L. Stupitsky; N. E. Lavrinenko; A. Yu. Repin; A. S. Kholodov

    2006-01-01

    For an explanation of results and forecasting of experiments in the top ionosphere and magnetosphere with use of plasma jets and powerful explosions physical models and three-dimensional numerical algorithm on basis of MHD approximation are developed In the algorithm a new updating of a grid-characteristic method of 2-3 order of approximation with splitting on spatial variable and physical processes is

  5. Results from the SEEP active space plasma experiment - Effects on the ionosphere

    Microsoft Academic Search

    W. L. Imhof; E. E. Gaines; H. D. Voss; J. B. Reagan; D. W. Datlowe; J. Mobilia; R. A. Helliwell; J. Katsufrakis; R. G. Joiner

    1985-01-01

    An active satellite-ground coordinated space plasma experiment was conducted from May to December, 1982, in which electrons were precipitated from the radiation belts into the ionosphere by the controlled injection of VLF signals from ground-based transmitters. The results confirm the hypothesis that electrons can be precipitated from the radiation belts by ground-based VLF transmitters, and they provide information relating to

  6. Yearly variations of global plasma densities in the topside ionosphere at middle and low latitudes

    Microsoft Academic Search

    Libo Liu; Biqiang Zhao; Weixing Wan; S. Venkartraman; Man-Lian Zhang; X. Yue

    2007-01-01

    In this paper, the 10-year (1996–2005) measurements of total ion density (Ni) from the Defense Meteorological Satellite Program (DMSP) spacecraft at 0930 and 2130 LT have been analyzed to investigate the yearly variations of global plasma densities in the topside ionosphere at magnetic latitudes from 60°S to 60°N. Results indicate that there are strong yearly variations in the DMSP Ni

  7. Plasma convection at high latitudes using the EISCAT VHF and ESR incoherent scatter radars

    E-print Network

    Boyer, Edmond

    Plasma convection at high latitudes using the EISCAT VHF and ESR incoherent scatter radars J. M allows several important tests to be made on the determination of convection patterns from incoherent volume results from the two radars are compared. The plasma convection velocities determined

  8. Enhancement of EM-Ionosphere interaction through Plasma Lens and Frequency Chirping

    NASA Astrophysics Data System (ADS)

    Pau, J.; Wong, A. Y.; Rosenthal, G.; Koziar, K. E.; Stone, K.

    2002-11-01

    During ionospheric modification, both satellite beacons and sky maps from digital ionosonde measurements have detected large-density perturbation. This perturbation reaches a maximum when the incident HF matches the plasma frequency on the density plateau (or at f_oF2 layer). Experiments and theories are presented which describe how a plasma lens can be created at a lower altitude by pre-conditioning the ionosphere at a lower altitude; the lowering of plasma density at the center of the heated region causes a change in the index of refraction, thereby forming an equivalent ionospheric lens^1. Unlike earlier results obtained at Arecibo Observatory^2 using water molecules injected by a rocket, our concept is simpler and can be repeated many times. Another enhancement of interaction comes from the chirping of the heating frequency such that all the waves converge at the resonant layer at a particular time^3. Work supported by SDSU. ^1 A.Y. Wong, Proceedings of Ionsopheric Interactions Workshop, Santa Fe, NM, April, 2002. ^2 M. Sulzer, private communication. ^3 S. Cowley and E. Valeo, private communication.

  9. Effects of plasma sheet condition on the evolution of shielding and the Harang reversal under weak convection: RCM simulations

    NASA Astrophysics Data System (ADS)

    Gkioulidou, M.; Lyons, L. R.; Wang, C.; Wolf, R. A.

    2007-12-01

    Shielding of the convection electric field and the Harang reversal associated with the region 2 field-aligned current system are fundamental manifestations of the large-scale plasma transport within the tail plasma sheet and the electrodynamic coupling of this transport to the ionosphere. However, how their formation and evolution is affected by the plasma sheet density and temperature is not well understood. We have used the RCM with Tsyganenko 96 magnetic field model to investigate this effect of plasma sheet conditions under weak convection. We have found that the existence of an overlap in local time of Region 2 upward and downward field aligned currents is necessary for the formation of the Harang reversal. The downward field aligned current in this overlap region is associated with electrons and low energy ions, while the upward field aligned current is associated with high-energy ions. Higher plasma sheet pressure can cause quicker shielding of the penetration electric field. If the time scale of the shielding is much shorter than the drift time scale of the low energy particles, these low energy particles cannot penetrate earthward enough to cause the overlap, thus preventing formation of the Harang reversal. Under the same plasma sheet pressure, higher auroral conductance can result in slower shielding. Higher plasma temperature enhances the upward field-aligned currents in the overlap region, therefore leading to a stronger Harang reversal. Currently we are running the simulation under different strengths of convection and with more realistic MLT dependent boundary conditions based on the Geotail observations.

  10. Titan's plasma environment and ionosphere during the T85/T42/T32 magnetosheath encounters (Invited)

    NASA Astrophysics Data System (ADS)

    Edberg, N. J.; Andrews, D. J.; Shebanits, O.; Agren, K.; Wahlund, J.; Opgenoorth, H. J.; Garnier, P.; Roussos, E.; Cravens, T.; Badman, S. V.; Modolo, R.; Bertucci, C.; Dougherty, M. K.

    2013-12-01

    During the T85 flyby we observe the highest electron number densities ever reported from the ionosphere of Titan as measured by RPWS/LP. The measured density reached 4310 cm-3, which is at least 500 cm-3 higher than ever observed before, and at least 50 % above the average density for similar solar zenith angles. The peak of the ionospheric density is not reached on this flyby, making the maximum measured density a lower limit. Furthermore, we observe that Titan was located in the magnetosheath of Saturn for at least 2 h 45 min before the actual flyby. This long-term exposure to magnetosheath plasma and crossings of the magnetopause and bow shock might be the reason why the peak ionospheric electron density during T85 rise to the maximum recorded. We propose that enhanced fluxes of solar wind protons precipitating and causing particle impact ionoisation is the physical explanation for the extreme densities during T85. Measurements by RPWS/LP indicate from several flybys (T83-T91) that the electron density in the peak region of Titan's ionosphere (950-1100 km) has increased by about 15-30% during the last 2 years. Furthermore, the peak ionospheric density is found at lower altitudes, though the flyby geometry often affords only the inference of an upper-limit. The increase is most likely a response to the rising toward a new solar max with increasing EUV flux. Still, T85 stands out in terms of extreme densities. We compare the ionospheric structure and plasma environment of Titan during the T85 flyby to that of the previous T32/T42 magnetosheath encounter. T32 showed no apparent increased density in the peak region but that flyby occurred during the solar minimum era and close to the terminator plane of Titan. T42 on the other hand showed high electron densities despite the solar minimum conditions, but occurred at low solar zenith angles, where the ionospheric density normally is higher compared to high solar zenith angles. Orbital geometry and Cassini MAG measurements during the T85 magentosheath encounter.

  11. Magnetosphere-ionosphere interactions: Near Earth manifestations of the plasma universe

    NASA Technical Reports Server (NTRS)

    Faelthammar, Carl-Gunne

    1986-01-01

    As the universe consists almost entirely of plasma, the understanding of astrophysical phenomena must depend critically on the understanding of how matter behaves in the plasma state. In situ observations in the near Earth cosmical plasma offer an excellent opportunity of gaining such understanding. The near Earth cosmical plasma not only covers vast ranges of density and temperature, but is the site of a rich variety of complex plasma physical processes which are activated as a results of the interactions between the magnetosphere and the ionosphere. The geomagnetic field connects the ionosphere, tied by friction to the Earth, and the magnetosphere, dynamically coupled to the solar wind. This causes an exchange of energy an momentum between the two regions. The exchange is executed by magnetic-field-aligned electric currents, the so-called Birkeland currents. Both directly and indirectly (through instabilities and particle acceleration) these also lead to an exchange of plasma, which is selective and therefore causes chemical separation. Another essential aspect of the coupling is the role of electric fields, especially magnetic field aligned (parallel) electric fields, which have important consequences both for the dynamics of the coupling and, especially, for energization of charged particles.

  12. A method to derive maps of ionospheric conductances, currents, and convection from the Swarm multisatellite mission

    NASA Astrophysics Data System (ADS)

    Amm, O.; Vanhamäki, H.; Kauristie, K.; Stolle, C.; Christiansen, F.; Haagmans, R.; Masson, A.; Taylor, M. G. G. T.; Floberghagen, R.; Escoubet, C. P.

    2015-04-01

    The European Space Agency (ESA) Swarm spacecraft mission is the first multisatellite ionospheric mission with two low-orbiting spacecraft that are flying in parallel at a distance of ~100-140 km, thus allowing derivation of spatial gradients of ionospheric parameters not only along the orbits but also in the direction perpendicular to them. A third satellite with a higher orbit regularly crosses the paths of the lower spacecraft. Using the Swarm magnetic and electric field instruments, we present a novel technique that allows derivation of two-dimensional (2-D) maps of ionospheric conductances, currents, and electric field in the area between the trajectories of the two lower spacecraft, and even to some extent outside of it. This technique is based on Spherical Elementary Current Systems. We present test cases of modeled situations from which we calculate virtual Swarm data and show that the technique is able to reconstruct the model electric field, horizontal currents, and conductances with a very good accuracy. Larger errors arise for the reconstruction of the 2-D field-aligned currents (FAC), especially in the area outside of the spacecraft orbits. However, even in this case the general pattern of FAC is recovered, and the magnitudes are valid in an integrated sense. Finally, using an MHD model run, we show how our technique allows estimation of the ionosphere-magnetosphere coupling parameter K, if conjugate observations of the magnetospheric magnetic and electric field are available. In the case of a magnetospheric multisatellite mission (e.g., the ESA Cluster mission) several K estimates at nearby points can be generated.

  13. Topside Ionosphere Plasma Bubbles Seen in He+ Density: Results and Problems

    NASA Astrophysics Data System (ADS)

    Sidorova, Larisa; Filippov, Sergey

    He (+) density depletions, considered as fossil equatorial plasma bubble signatures, were involved in this study. They are usually detected in the topside ionosphere (approx. 1000 km) deeply inside the plasmasphere (L=1.3-3). a) The question about an opportunity to detect the topside plasma bubbles of equatorial origin in their separate plasma component (He (+) ) is investigated. There are the indications [Sidorova, ASR, 2004, 2007; Sidorova and Filippov, JASTP, 2012] that there is genetic connection between the He (+) density depletions and the equatorial plasma bubbles. For validation of this idea the characteristic times of the main photochemical and electro-dynamical processes, in which the plasma bubbles and their minor ion component (He (+) ) are involved, have been calculated and compared. The model estimations, obtained in SAMIS3 (3D model of equatorial spread F) and kindly presented by J. Huba (USA), are also used for the investigation. It was revealed that the plasma bubbles, reaching the “ceiling” heights, can exist within 2-3 days and that there is principal opportunity to observe them in the separate plasma component (He (+) ). (b) The longitudinal statistics of the He (+) density depletions (P), calculated for all seasons and both hemispheres (20-50(°) INVLAT), were obtained. It was revealed that the most of the P plots have “wave-like” structure with well-defining four peaks. The peaks are the most pronounced in the NH during March equinox/December solstice and in the SH during March equinox/June solstice. Similar wave number 4 longitudinal structure has recently been found in the low-latitude ionosphere density distribution [Immel et al., GRL, 2006; England et al., GRL, 2006; Jin et al., JGR, 2008]. It is assumed that the longitudinal plasma density variations appear due to the modulated vertical ?×? drift. It is supposed that solar thermal tides excited in the troposphere induce zonal perturbation electric fields, which are added to the background F-region dynamo field, modulating the ionosphere fountain process. If the hypothesis about an equatorial origin of He (+) density depletions is true, we can suppose that such 4-peaked structure projected to the topside ionosphere are reflected in their longitudinal statistics. Perhaps this idea can be very useful for explanation of the obtained results. The results of this pioneer study suggest new investigation questions, based mainly on data lacking.

  14. Ionosphere/thermosphere heating determined from dynamic magnetosphere-ionosphere/thermosphere coupling

    NASA Astrophysics Data System (ADS)

    Tu, Jiannan; Song, Paul; Vasyli?nas, Vytenis M.

    2011-09-01

    Ionosphere/thermosphere heating driven by magnetospheric convection is investigated through a three-fluid inductive (including Faraday's law) approach to describing magnetosphere-ionosphere/thermosphere coupling, for a 1-D stratified ionosphere/thermosphere in this initial study. It is shown that the response of the ionosphere/thermosphere and thus the heating is dynamic and height-dependent. The heating is essentially frictional in nature rather than Joule heating as commonly assumed. The heating rate reaches a quasi-steady state after about 25 Alfvén travel times. During the dynamic period, the heating can be enhanced and displays peaks at multiple times due to wave reflections. The dynamic heating rate can be more than twice greater than the quasi-steady state value. The heating is strongest in the E-layer but the heating rate per unit mass is concentrated around the F-layer peak height. This implies a potential mechanism of driving O+ upflow from O+ rich F-layer. It is shown that the ionosphere/thermosphere heating caused by the magnetosphere-ionosphere coupling can be simply evaluated through the relative velocity between the plasma and neutrals without invoking field-aligned currents, ionospheric conductance, and electric field. The present study provides understanding of the dynamic magnetosphere-ionosphere/thermosphere coupling from the ionospheric/thermospheric view in addition to magnetospheric perspectives.

  15. Plasma bubbles and irregularities in the equatorial ionosphere

    Microsoft Academic Search

    J. P. McClure; W.B. Hanson; J. H. Hoffman

    1977-01-01

    Using the Atmosphere Explorer satellite AE-C, we observe large-scale (10- to >200-km) irregular biteouts of up to three orders of magnitude in the ion concentration N⁠in the nighttime equatorial F region associated with small-scale inhomogeneities in Nâ. Similar phenomena were reported by Hanson and Sanatani but without the more complete plasma diagnostics present on AE. Simultaneous plasma velocity observations

  16. Plasma Instability Growth Rates in the F-Region Cusp Ionosphere

    NASA Astrophysics Data System (ADS)

    Moen, J. I.; Daabakk, Y.; Oksavik, K.; Clausen, L.; Bekkeng, T. A.; Abe, T.; Saito, Y.; Baddeley, L. J.; Lorentzen, D. A.; Sigernes, F.; Yeoman, T. K.

    2014-12-01

    There are at least two different micro-instability processes that applies to the F-region cusp/polar cap ionosphere. These are the Gradient Drift Instability (GDI) and the Kelvin Helmholtz Instability (KHI). Due to space weather effects on radio communication and satellite signals it is of practical interest to assess the relative importance of these two instability modes and to quantify their growth rates. The Investigation of Cusp Irregularities (ICI) rocket program has been developed to investigate these plasma instabilities and formation scintillation irregularities. High resolution measurements are critical to get realistic quantities on the growth rates. The results achieved so far demonstrates that cusp ionosphere precipitation can give rise to km scale plasma structures on which grow rates are down to a few tens of seconds compared to earlier measures of ten minutes based on ground observations. This has to do with the spatial resolution required for these measurements. Growth rates for the KHI instability is found to be of the same order, which is consistent with growth rates calculated from the EISCAT Svalbard Radar. I.e. both instability modes can be highly efficient in the cusp ionosphere.

  17. HF Propagation Effects Caused by an Artificial Plasma Cloud in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Joshi, D. R.; Groves, K. M.; McNeil, W. J.; Caton, R. G.; Parris, R. T.; Pedersen, T. R.; Cannon, P. S.; Angling, M. J.; Jackson-Booth, N. K.

    2014-12-01

    In a campaign carried out by the NASA sounding rocket team, the Air Force Research Laboratory (AFRL) launched two sounding rockets in the Kwajalein Atoll, Marshall Islands, in May 2013 known as the Metal Oxide Space Cloud (MOSC) experiment to study the interactions of artificial ionization and the background plasma and measure the effects on high frequency (HF) radio wave propagation. The rockets released samarium metal vapor in the lower F-region of the ionosphere that ionized forming a plasma cloud that persisted for tens of minutes to hours in the post-sunset period. Data from the experiments has been analyzed to understand the impacts of the artificial ionization on HF radio wave propagation. Swept frequency HF links transiting the artificial ionization region were employed to produce oblique ionograms that clearly showed the effects of the samarium cloud. Ray tracing has been used to successfully model the effects of the ionized cloud. Comparisons between observations and modeled results will be presented, including model output using the International Reference Ionosphere (IRI), the Parameterized Ionospheric Model (PIM) and PIM constrained by electron density profiles measured with the ALTAIR radar at Kwajalein. Observations and modeling confirm that the cloud acted as a divergent lens refracting energy away from direct propagation paths and scattering energy at large angles relative to the initial propagation direction. The results confirm that even small amounts of ionized material injected in the upper atmosphere can result in significant changes to the natural propagation environment.

  18. Processes in complex (dusty) plasmas in the midlatitude ionosphere during high-speed meteor showers

    NASA Astrophysics Data System (ADS)

    Popel, S. I.; Kopnin, S. I.

    2007-08-01

    The emission low-frequency lines in the frequency range of 12 to 60 Hz recorded [1] against the radio-frequency noise background during high-speed (the speed of entry into the atmosphere is about 70 km/s) meteor showers (Perseids, Orionids, Leonids, and Gemenids) are shown to serve as an evidence of the existence of complex (dusty) plasmas in the midlatitude ionosphere. The mechanism for generating the radio-frequency noises in the frequency range of 12 to 60 Hz is shown to be as follows. During Perseid, Orionid, Gemenid, and Leonid meteor showers, the meteors are ablated at altitudes of 70-130 km, depending on their sizes and initial velocities. The result of ablation is the production of supersaturated vapors of such metals as sodium, calcium, magnesium, etc., which then condense into nanometer-to-micrometer-sized secondary (dust) grains of cosmic origin. The grains can acquire an electric charge because of the action of unbalanced electron and ion currents and because of the photoelectric effect resulting from solar light. As an electromagnetic wave propagates in a complex (dusty) plasma in the ionosphere, the modulational interaction [2] excites low-frequency electrostatic waves at characteristic frequencies close to those of the dust acoustic waves, with the result that electromagnetic waves may become modulated. It is the low-frequency component of the wave modulated against the ionospheric noise background that is recorded at the Earth's surface. Our theoretical results are shown to agree well with the data on ionospheric plasma noise observed during meteor showers. We show also that along with the low-frequency component of modulated electromagnetic waves, the lines of infrasonic waves generated in the meteoric precipitation regions should be recorded as well. The infrasonic waves are generated by the dust acoustic waves interacting with neutrals. We determine the conditions for generation of both linear and nonlinear infrasonic waves by the dust acoustic waves, study their propagation in the atmosphere, determine the intensity of the infrasonic waves generated in the ionosphere by the dust acoustic waves during Perseid, Orionid, Gemenid and Leonid meteor showers, and find frequency ranges where they can compete with the infrasonic waves from other sources. References [1] S.I. Musatenko, Yu.S. Musatenko, E.V. Kurochka, et al., 4-th Ukrainian Conf. Space Research (Kiev, 2004), p. 96. [2] S.V. Vladimirov, V.N. Tsytovich, S.I. Popel, and F.Kh. Khakimov, Modulational Interactions in Plasmas (Kluwer Academic Publishers, Dordrecht, 1995), 544 pages.

  19. TARANIS: a Tool to investigate Potential Links Between Sprites and Ionospheric and Magnetospheric Plasmas

    NASA Astrophysics Data System (ADS)

    Francois, L.; Elisabeth, B.; TARANIS Team

    2004-12-01

    TARANIS (Tool for the Analysis of RAdiations from lightNIngs and Sprites) is a CNES microsatellite project which will be in phase A in 2005. The main scientific objective is to compare observations of sprites and other optical emissions (blue jets, halos, elves,etc.) with observations of terrestrial gamma and X ray flashes, electromagnetic and electrostatic emissions, and energetic electrons, in order to investigate physical mechanisms allowing impulsive transfers of energy between the neutral atmosphere and the ionospheric and magnetospheric plasmas. The main questions to be addressed for a satellite mission are presented. They include : the triggering factor of the optical emissions, the quasi electrostatic field above thunderstorms, the modification of the electrodynamics of the ionosphere, the detection and the modeling of energetic runaways electron beams, the associated electromagnetic and electrostatic emissions, the presence of the generated electron beams within the magnetosphere and more specifically within the radiation belts. The adequation of the scientific payload to the scientific objectives is discussed.

  20. Plasma Waves Observed at Low Altitudes in the Tenuous Venus Nightside Ionosphere

    NASA Technical Reports Server (NTRS)

    Strangeway, R. J.; Russell, C. T.; Ho, C. M.; Brace, L. H.

    1993-01-01

    The Pioneer Venus Orbiter Electric Field Detector (OEFD) measured many plasma wave bursts throughout the low altitude ionosphere during the final entry phase of the spacecraft. Apart from 100 Hz bursts observed at very low altitudes (approx. 130 km), the bursts fall into two classes. The first of these is a wideband signal that is observed in regions of low magnetic field, but average densities, in comparison to the prevailing ionospheric condition. This wideband signal is not observed in the 30 kHz channel of the OEFD, but is restricted to the 5.4 kHz channel and lower. Since these bursts are observed with roughly constant burst rate above 160 km altitude, we attribute them to ion acoustic mode waves generated by precipitating solar wind electrons. The second type of signal is restricted to 100 Hz only, and is observed in regions of low electron beta, consistent with whistler-mode waves. These waves could be generated by lightning in the Venus atmosphere if the vertical component of the magnetic field greater than 3.6 nT. Unfortunately, the spacecraft spin axis is mainly horizontal, and only that component of magnetic field can be measured. Alternatively, the 100 Hz bursts could be generated locally through gradient drift instabilities, provided the ambient magnetic field is horizontal. Because the ionosphere is very different during the entry phase, compared to the ionosphere as observed early in the Pioneer Venus mission, any conclusions regarding the source of the plasma waves detected during entry phase cannot be applied directly to the earlier observations.

  1. Variation of the cold plasma density structure above the polar ionosphere associated with geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Kitamura, N.; Shinbori, A.; Nishimura, Y.; Ono, T.; Iizima, M.; Kumamoto, A.; Yamada, M.; Watanabe, S.; Abe, T.

    2007-12-01

    Plasma outflow from the polar ionosphere into the magnetosphere is one of the most important processes in the magnetosphere-ionosphere coupling in the polar region. Recent satellite observations have clarified that plasma outflow takes an important role for plasma transport into the magnetosphere, abrupt changes of the ring current ion composition, and the disappearance of the auroral acceleration region during geomagnetic storms. In the present study, we analyzed the electron density data observed by the Akebono satellite in an altitude range from 300 to 10500 km, in order to clarify the formation process of the plasma density enhancement above the polar ionosphere. The electron density along the satellite path was derived using the upper-hybrid resonance (UHR) frequency and maximum frequency of whistler-mode waves observed by the PWS instrument onboard the Akebono satellite with the time resolution of 2 seconds. In the present data analysis, we used the electron density data from March, 1989 to July, 1990 for statistical analyses. First, we investigate the statistically averaged density distributions during the quiet time in summer, equinox, and winter seasons. The data are sorted by day and night in magnetic local time, 5 degrees in invariant latitude and 100 km in altitude. The logarithmically averaged data in each bin are fitted by using the non-linear least square fitting method in altitude direction, using the equation of sum of the exponential and power law functions. Then, the fitted profiles are interpolated in ILAT direction by exponential functions. Finally, we obtain electron density distribution on the meridian plane. From comparing these distributions, it is identified that electron density in summer is 5 to 50 times larger than that in winter below 5000 km altitude in the polar cap and auroral zone. Next, we perform case studies for the geomagnetic storm events which occurred on June 6, June 9, 1989 and March 30, 1990. In these events, enhancements of the plasma density are identified in the entire polar cap being associated with the period of storm main phase. In June 7, the electron density enhanced up to 100 times larger than the quiet-time level. In March 30, the SMS instrument onboard the Akebono satellite observed upward flow of oxygen ions, in the electron density enhancement region. These results indicate that a large amount of the ionospheric plasma flows upward to at least about 10000 km in the polar magnetosphere during geomagnetic storms.

  2. Diffusion spreading of middle-latitude ionospheric plasma irregularities

    Microsoft Academic Search

    Nathan Blaunstein

    1995-01-01

    In contrast to the way that the spreading of irregularities in a plasma is usually considered, the diffusion spreading of irregularities stretched along the geomagnetic field B is examined using a three-dimensional rigorous numerical model of quasi-neutral diffusion in the presence of a magnetic field, in conjunction with the actual height variations of the diffusion and conductivity tensors in the

  3. A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far-ultraviolet spacecraft observations

    Microsoft Academic Search

    S. H. Park; S. L. England; T. J. Immel; H. U. Frey; S. B. Mende

    2007-01-01

    The Far-Ultraviolet Imager (IMAGE-FUV) on board the NASA IMAGE satellite has been used to observe plasma depletions in the nightside equatorial ionosphere. Observations from periods around spacecraft apogee, during which equatorial regions are visible for several hours, have allowed the velocity of these plasma depletions to be determined. A new method for determining the velocity of these depletions using an

  4. Modeling Ionospheric Convection During a Major Geomagnetic Storm on October 22-23, 1981

    NASA Technical Reports Server (NTRS)

    Moses, J. J.; Slavin, J. A.; Aggson, T. L.; Heelis, R. A.; Winningham, J. D.

    1994-01-01

    Following the passage of an interplanetary shock at approximately 0500 UT, a major geomagnetic storm developed on October 22-23, 1981. Numerous auroral substorms occurred during this storm leading to an AE index greater than 1000 nT. We have used the expanding/contracting polar cap (ECPC) model (Moses et al., 1989) and data from the Dynamics Explorer 2 spacecraft to study the ionospheric electric fields for 12 consecutive traversals of the polar regions. The ECPC model can determine the voltage drops across the dayside merging and nightside reconnection gaps. We determined the relationship of the AL index (i.e., the intensity of the westward electrojet) to the nightside reconnection potential drop. An excellent linear correlation was found between the nightside reconnection gap voltage drop and the AL index. These results show that the solar wind strongly drives the magnetosphere-ionosphere system throughout the geomagnetic storm. A substantial level of dayside merging seems to occur throughout the event. Nightside reconnection varies from satellite pass to satellite pass and within the substorm recovery phase. We find that tail reconnection is an important feature of the recovery phase of substorms.

  5. On the equatorial transport of Saturn's ionosphere as driven by a dust-ring current system

    NASA Technical Reports Server (NTRS)

    Ip, W.-H.; Mendis, D. A.

    1983-01-01

    The diurnal modulation of the dust ring current of Saturn's D-ring causes field-aligned Birkeland currents to flow near the dawn and dusk terminators and close across the midlatitude ionosphere. One consequence of this current system is the establishment of a global convection pattern in the equatorial outer ionosphere. Outward motion of the dayside ionospheric plasma as well as the corresponding absorption effect of the inner ring system might be one physical cause of the depletion of the ionospheric content of Saturn.

  6. Intermediate-scale plasma irregularities in the polar ionosphere inferred from GPS radio occultation

    NASA Astrophysics Data System (ADS)

    Shume, E. B.; Komjathy, A.; Langley, R. B.; Verkhoglyadova, O.; Butala, M. D.; Mannucci, A. J.

    2015-02-01

    We report intermediate-scale plasma irregularities in the polar ionosphere inferred from high-resolution radio occultation (RO) measurements using GPS (Global Positioning System) to CASSIOPE (CAScade Smallsat and IOnospheric Polar Explorer) satellite radio links. The high inclination of CASSIOPE and the high rate of signal reception by the GPS Attitude, Positioning, and Profiling RO receiver on CASSIOPE enable a high-resolution investigation of the dynamics of the polar ionosphere with unprecedented detail. Intermediate-scale, scintillation-producing irregularities, which correspond to 1 to 40 km scales, were inferred by applying multiscale spectral analysis on the RO phase measurements. Using our multiscale spectral analysis approach and satellite data (Polar Operational Environmental Satellites and Defense Meteorological Satellite Program), we discovered that the irregularity scales and phase scintillations have distinct features in the auroral oval and polar cap. We found that large length scales and more intense phase scintillations are prevalent in the auroral oval compared to the polar cap implying that the irregularity scales and phase scintillation characteristics are a function of the solar wind and magnetospheric forcings.

  7. A global analysis of the electrodynamic interactions between a space station and the ionospheric plasma environment

    NASA Technical Reports Server (NTRS)

    Wang, J.; Hastings, D. E.

    1991-01-01

    A general analysis of the electrodynamic interactions between a space station with two biased platforms and the ionospheric plasma is presented. This problem can be separated into a far-field problem, concerned with the electromagnetic interference surrounding the entire space station, and a near-field problem, concentrated on the interactions in the vicinity of the biased platforms. The far-field problem is solved by application of plasma fluid theory. The space station will generate a radiation field composed mainly of the Alfven waves. This far-field radiation depends on the details of the near-field current collection. Computer particle simulations were performed in the near-field of the biased platform to study the plasma flow field, the sheath structure and the current collection. Approximate analytical solutions to the near-field are also obtained. The far-field and near-field solutions are coupled to provide a global description of the electrodynamic interactions.

  8. UCB current detector experiment on Swedish auroral payloads. [ionospheric current and plasma flow measurements

    NASA Technical Reports Server (NTRS)

    Mozer, F.

    1974-01-01

    A split Langmuir probe has been developed to make in situ measurements of ionospheric current density and plasma bulk flow. The probe consists of two conducting elements that are separated by a thin insulator that shield each other over a 2 pi solid angle, and that are simultaneously swept from negative to positive with respect to the plasma. By measuring the current to each plate and the difference current between plates, information is obtained on the plasma's current density, bulk flow, electron temperature, and density. The instrument was successfully flown twice on sounding rockets into auroral events. Measurement data indicate that the total auroral current configuration is composed of several alternating east and west electrojets associated with several alternating up and down Birkeland currents.

  9. Response of High Latitude Birkeland Currents and Ionospheric Convection to Transitions in Solar Wind Forcing

    NASA Astrophysics Data System (ADS)

    Anderson, B. J.; Korth, H.; Merkin, V. G.; Barnes, R. J.; Ruohoniemi, J. M.

    2014-12-01

    Recent results from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) indicate that at least some transitions from northward to southward IMF produce a specific sequence in the development of large-scale Birkeland currents. First, a set of Region 1 and Region 2 currents forms on the dayside restricted to within a few hours of noon. After about 40 minutes, currents strongly intensify on the nightside, first near midnight local time associated with substorm onset, and then progressively further toward the dayside via dawn and dusk. Only after an hour or more after the transition to stronger solar wind forcing, is the complete Region 1, Region 2 current system developed. The results imply that the initial response to a transition from weak to strong forcing is convection into the polar cap and lobes without strong return convection to the dayside from the nightside magnetosphere. Return convection from the nightside begins with substorm onset and progresses to the dayside. This analysis is extended by examining a large number of transitions from prolonged auroral quiescence, associated with northward IMF, to southward IMF and the development of large-scale Region 1/Region 2 Birkeland currents, to assess whether the above progression holds in general. In addition, transition events to particularly intense driving, for example, associated with shocks are examined to assess how this ordering of events may be changed for onsets of particularly intense solar wind forcing.

  10. Suprathermal plasma analyzer for the measurement of low-energy electron distribution in the ionosphere

    SciTech Connect

    Shimoyama, M.; Yau, A. W. [Department of Physics and Astronomy, University of Calgary, Calgary T2N1N4 (Canada); Oyama, K.-I. [Plasma and Space Science Center, National Cheng Kung University, Tainan 701, Taiwan (China); Abe, T. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa 252-5210 (Japan)

    2011-07-15

    It is commonly believed that an energy transfer from thermal to suprathermal electrons (ionosphere. However, observation of electron energy spectrum in this energy range is quite limited because of technical difficulties of measurement. We have developed an instrument to measure electron energy distribution from thermal to suprathermal energy continuously with high-energy resolution of about 0.15 eV. The measurement principle is based on the combination of a retarding potential analyzer with a channel electron multiplier (CEM) and the Druyvesteyn method, which derives energy distribution from the current-voltage characteristics. The capability of detecting plasma space potential enables absolute calibration of electron energy. The instrument with a small vacuum pump, which is required for the CEM to work in low-vacuum region, was first successfully tested by a sounding rocket S-310-37 in the ionospheric E region. The instrument is expected to provide new opportunities to measure energy distribution of thermal and non-thermal electrons in low-density plasma, where a Langmuir probe cannot measure electron temperature because of low plasma density.

  11. Suprathermal plasma analyzer for the measurement of low-energy electron distribution in the ionosphere.

    PubMed

    Shimoyama, M; Oyama, K-I; Abe, T; Yau, A W

    2011-07-01

    It is commonly believed that an energy transfer from thermal to suprathermal electrons (ionosphere. However, observation of electron energy spectrum in this energy range is quite limited because of technical difficulties of measurement. We have developed an instrument to measure electron energy distribution from thermal to suprathermal energy continuously with high-energy resolution of about 0.15 eV. The measurement principle is based on the combination of a retarding potential analyzer with a channel electron multiplier (CEM) and the Druyvesteyn method, which derives energy distribution from the current-voltage characteristics. The capability of detecting plasma space potential enables absolute calibration of electron energy. The instrument with a small vacuum pump, which is required for the CEM to work in low-vacuum region, was first successfully tested by a sounding rocket S-310-37 in the ionospheric E region. The instrument is expected to provide new opportunities to measure energy distribution of thermal and non-thermal electrons in low-density plasma, where a Langmuir probe cannot measure electron temperature because of low plasma density. PMID:21806205

  12. Transport of thermal-energy ionospheric oxygen (O+) ions between the ionosphere and the plasma sheet and ring current at quiet times preceding magnetic storms

    NASA Astrophysics Data System (ADS)

    Yau, Andrew W.; Howarth, Andrew; Peterson, W. K.; Abe, Takumi

    2012-07-01

    The presence of energetic O+ ions in the ring current at the onset of a magnetic storm prompts the question of the possible role of “in-transit” ionospheric O+ ions between the ionosphere and the plasma sheet and ring current in the quiet periods immediately preceding the main phase of a magnetic storm. Thermal-energy O+ ions are often observed in the quiet time high-altitude (>7000 km) polar ionosphere on Akebono, at temperatures of ˜0.2-0.3 eV and flow velocities of a few km/s. In this paper, we use single-particle trajectory simulation to study the transport of these ions in the periods preceding a number of large magnetic storms (Dst < -100 nT). Our simulation shows that due to centrifugal ion acceleration at higher altitudes (above ˜3 RE altitude), about 10-20% of polar wind and other low-energy O+ ions reaches the plasma sheet during such periods; the actual percentage is a factor of ˜3 larger in the dusk sector on average compared with the dawn sector and dependent on the IMF and the O+ ion temperature. This provides a low but non-negligible flux of O+ ions between the ionosphere and the plasma sheet and ring current, which is believed to constitute a significant “in-transit” oxygen ion population over a period of a few (˜4) hours preceding a magnetic storm. Such a population could explain the presence of energetic O+ ions at the onset of the main phase of the storm, when the heavy ions could potentially modify the evolution of the ring current.

  13. Recent observations of beam plasma interactions in the ionosphere and a comparison with laboratory studies of the beam plasma discharge

    NASA Technical Reports Server (NTRS)

    Bernstein, W.; Kellogg, P. J.; Monson, S. J.; Holzworth, R. H.; Whalen, B. A.

    1982-01-01

    Experimental results from an electron beam injection rocket flight (27:010 AE) launched into an active aurora are summarized. The rocket carried an accelerator which injected programmed electron beams of less than 100 ma at 2 and 4 kV into the ionospheric plasma over the altitude range 120-240 km. A major objective of the experiment was the study of beam-plasma interactions and the possible identification of the ignition of the beam-plasma discharge (BPD) which had been intensively studied in the laboratory. A qualitative assessment of the data indicates that BPD ignition was produced by both 10 ma and Im beams at 2 and 4 kV. Many of the observed characteristics are similar to the BPD characteristics observed in the laboratory.

  14. Collisional\\/resonance absorption in cold\\/warm magnetized plasmas of the F-region high-latitude ionosphere

    Microsoft Academic Search

    N. A. Gondarenko; S. L. Ossakow; P. A. Bernhardt

    2009-01-01

    The collisional\\/resonance absorption due to linear mode conversion of electromagnetic waves into electrostatic\\/plasma waves is studied in cold\\/warm magnetized plasmas relevant to the F-region of the high-latitude ionosphere. The absorption coefficient is calculated numerically using a full-wave model for high-frequency waves incident normally\\/obliquely to the direction of inhomogeneity. The absorption coefficient of collisional cold plasmas is found to be independent

  15. Development of beam-plasma instability during the injection a low-energy electron beam into the ionospheric plasma

    SciTech Connect

    Baranets, N. V.; Sobolev, Ya. P. [Russian Academy of Sciences, Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (Russian Federation); Ciobanu, M. [Institute for Gravitation and Space Sciences (Romania); Vojta, J.; Smilauer, J. [Academy of Sciences of the Czech Republic, Institute of Atmospheric Physics (Czech Republic); Klos, Z.; Rothkaehl, H.; Kiraga, A. [Polish Academy of Sciences, Space Research Center (Poland); Kudela, K.; Matisin, J. [Slovak Academy of Sciences, Institute of Experimental Physics (Slovakia); Afonin, V. V. [Russian Academy of Sciences, Space Research Institute (Russian Federation); Ryabov, B. S.; Isaev, N. V. [Russian Academy of Sciences, Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation (Russian Federation)

    2007-12-15

    Results are presented from an active experiment on the injection of charged particle beams into the ionospheric plasma. The experiment was carried out in 1992 onboard the Intercosmos-25 satellite and the Magion-3 daughter satellite (APEX). A specific feature of this experiment was that both the ion and electron beams were injected upward, in the same direction along the magnetic field. The most interesting results are the excitation of HF and VLF-LF waves and the generation of fast charged particle flows, which were recorded on both satellites.

  16. Ionospheric irregularities

    Microsoft Academic Search

    B.G. Fejer; M. C. Kelley

    1980-01-01

    Extensive experimental and theoretical research has been performed in the last decade to study ionospheric irregularities. These studies have shown that plasma instabilities play a major role in the generation of the irregularities. In this work we describe in detail the recent experimental studies of the E and F region irregularities and also the extensive work on plasma instability theories

  17. Effects of finite plasma pressure on centrifugally driven convection in Saturn's magnetosphere

    NASA Astrophysics Data System (ADS)

    Liu, X.; Hill, T. W.

    2011-12-01

    We have previously shown simulation results for centrifugally driven plasma convection in Saturn's inner magnetosphere, using the Rice Convection Model, including a continuously active distributed plasma source, and effects of the Coriolis force and the pickup current. These simulations result in a quasi-steady state, in which fast, narrow inflow channels alternate with slower, wider outflow channels, consistent with Cassini Plasma Spectrometer observations. Comparison of different plasma source models indicates that the inner plasma source distribution is a key element in determining the plasma convection pattern. Previous simulations, however, did not include the effects of finite plasma pressure and the associated gradient-curvature drift. We will investigate here the effects of finite plasma pressure and gradient-curvature drift by giving the cold plasma a finite temperature. We will also add a source of hot tenuous plasma at the outer simulation boundary in an attempt to simulate the injection/dispersion events observed by Cassini.

  18. A simulation study on the impact of altitudinal dependent vertical plasma drift on the equatorial ionosphere in the evening

    NASA Astrophysics Data System (ADS)

    Qian, Cheng; Lei, Jiuhou; Wang, Wenbin

    2015-04-01

    We carry out a simulation study on the impact of altitudinal dependent plasma drift on the equatorial ionosphere in the evening, under geomagnetically quiet conditions. Our study used the vertical plasma drift velocity data measured by an incoherent scatter radar at Jicamarca (11.95°S, 76.87°W). The data covered the local sunset period on 15 and 16 November 2004. The plasma drift had significant altitudinal variations in the vertical component, which is perpendicular to the magnetic field. We employed SAMI2 (SAMI2 is another model of the ionosphere) to evaluate the effect of the altitude-dependent ion drift on the equatorial ionosphere. Three types of plasma drift velocity inputs were used in our simulations. The first input is calculated from an empirical model, the second is a height-averaged drift obtained from the observed drift velocity, and the third one corresponds to the observed altitudinal dependent drift data. A strong equatorial ionization anomaly occurred in the results of all numerical experiments. Additional layers (F3 layers) in electron densities over the equatorial F region and "arch" latitudinal structures extending to lower middle latitudes were seen in the simulations driven by the observed altitudinal dependent drift. We further show that neutral winds do not have a significant effect on the simulated F3 layers. The results of our numerical experiments suggest that the simulated additional ionospheric layers and arch structures are associated with the altitudinal gradients in the vertical plasma drift velocity.

  19. Numerical modeling of the global changes to the thermosphere and ionosphere from the dissipation of gravity waves from deep convection

    NASA Astrophysics Data System (ADS)

    Vadas, S. L.; Liu, H.-L.; Lieberman, R. S.

    2014-09-01

    During the minimum of solar cycles 23-24, the Sun was extremely quiet; however, tropospheric deep convection was strong and active. In this paper, we model the gravity waves (GWs) excited by deep convective plumes globally during 15-27 June in 2009 and in 2000 (previous solar maximum). We ray trace the GWs into the thermosphere and calculate the body force/heatings which result where they dissipate. We input these force/heatings into a global dynamical model and study the neutral and plasma changes that result. The body forces induce horizontal wind (uH') and temperature (T') perturbations, while the heatings primarily induce T'. We find that the forces create much larger T' than the heatings. uH' consists of clockwise and counterclockwise circulations and "jet"-like winds that are highly correlated with deep convection, with |uH'|˜50-200m/s. uH' and T' are much larger during 2009 than 2000. uH' decreases slightly (significantly) with altitude from z˜150 to 400 km during 2009 (2000). T' perturbations at z=350km primarily propagate westward at ˜460 m/s, consistent with migrating tides. It was found that planetary-scale diurnal and semidiurnal tides are generated in situ in the thermosphere, with amplitudes ˜10-40m/s at z=250 km. The largest-amplitude in situ tides are DW1, D0, DW2, SW2, SW3, and SW5. Smaller-amplitude in situ tides are S0, SE2, and SW3. Total electron content (TEC') perturbations of 1-2.5 (2-3.5) total electron content units (TECU, where 1 TECU = 1016 el m-2) during 2009 (2000) are created in the upper atmosphere above nearby regions of deep tropical convection. For a given local time (LT), there are 2 to 3 TEC' peaks in longitude around the Earth.

  20. Determination of local plasma densities with the MARSIS radar: Asymmetries in the high?altitude Martian ionosphere

    NASA Astrophysics Data System (ADS)

    Andrews, D. J.; Opgenoorth, H. J.; Edberg, N. J. T.; André, M.; Fränz, M.; Dubinin, E.; Duru, F.; Morgan, D.; Witasse, O.

    2013-10-01

    We present a novel method for the automatic retrieval of local plasma density measurements from the Mars advanced radar for subsurface and ionospheric sounding (MARSIS) active ionospheric sounder (AIS) instrument. The resulting large data set is then used to study the configuration of the Martian ionosphere at altitudes above ˜300 km. An empirical calibration routine is used, which relates the local plasma density to the measured intensity of multiple harmonics of the local plasma frequency oscillation, excited in the plasma surrounding the antenna in response to the transmission of ionospheric sounding pulses. Enhanced accuracy is achieved in higher?density (ne>150 cm-3) plasmas, when MARSIS AIS is able to directly measure the fundamental frequency of the local plasma oscillation. To demonstrate the usefulness of this data set, the derived plasma densities are binned by altitude and solar zenith angle in regions over weak (|Bc|<20 nT) and strong (|Bc|>20 nT) crustal magnetic fields, and we find clear and consistent evidence for a significant asymmetry between these two regions. We show that within the ˜300-1200 km altitude range sampled, the median plasma density is substantially higher on the dayside in regions of relatively stronger crustal fields than under equivalent illuminations in regions of relatively weaker crustal fields. Conversely, on the nightside, median plasma densities are found to be higher in regions of relatively weaker crustal fields. We suggest that the observed asymmetry arises as a result of the modulation of the efficiency of plasma transport processes by the irregular crustal fields and the generally horizontal draped interplanetary magnetic field.

  1. Asymmetric Ionospheric Outflow Observed at the Dayside Magnetopause

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Zhang, H.; Zong, Q.; Sibeck, D. G.; Wang, Y.; Glassmeier, K. H.; Reme, H.

    2014-12-01

    An important source of the terrestrial magnetospheric plasma is cold plasma from the polar ionosphere. The ionospheric ion outflows have been rarely observed at the dayside magnetopause. We investigate the source and the behaviors of the cold ions observed by the Cluster spacecraft measurements. The pitch angle distributions (0°-75°) of the cold ions observed by both C1 and C3 at the dayside magnetopause indicate that these cold ions are ionospheric outflows coming from the southern hemisphere. The cold ions (< 200 eV) fluxes are modulated by the ULF wave electric field. The cold ions move perpendicular to the magnetic field due to the enhanced convection electric field when they are close to the magnetic reconnection region. Two different populations (possibly H+ and He+) were observed in the magnetosphere. Our results suggest that the ionospheric outflows can be transported to the dayside magnetopause and may play an important role in the dynamics of this region.

  2. Theory and Observations of Plasma Waves Excited Space Shuttle OMS Burns in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.; Pfaff, R. F.; Schuck, P. W.; Hunton, D. E.; Hairston, M. R.

    2010-12-01

    Measurements of artificial plasma turbulence were obtained during two Shuttle Exhaust Ionospheric Turbulence Experiments (SEITE) conducted during the flights of the Space Shuttle (STS-127 and STS-129). Based on computer modeling at the NRL PPD and Laboratory for Computational Physics & Fluid Dynamics (LCP), two dedicated burns of the Space Shuttle Orbital Maneuver Subsystem (OMS) engines were scheduled to produce 200 to 240 kg exhaust clouds that passed over the Air Force Research Laboratory (AFRL) Communications, Navigation, and Outage Forecast System (C/NOFS) satellite. This operation required the coordination by the DoD Space Test Program (STP), the NASA Flight Dynamics Officer (FDO), the C/NOFS payload operations, and the C/NOFS instrument principal investigators. The first SEITE mission used exhaust from a 12 Second OMS burn to deposit 1 Giga-Joules of energy into the upper atmosphere at a range of 230 km from C/NOFS. The burn was timed so C/NOFS could fly though the center of the exhaust cloud at a range of 87 km above the orbit of the Space Shuttle. The first SEITE experiment is important because is provided plume detection by ionospheric plasma and electric field probes for direct sampling of irregularities that can scatter radar signals. Three types of waves were detected by C/NOFS during and after the first SEITE burn. With the ignition and termination of the pair of OMS engines, whistler mode signals were recorded at C/NOFS. Six seconds after ignition, a large amplitude electromagnetic pulse reached the satellite. This has been identified as a fast magnetosonic wave propagating across magnetic field lines to reach the electric field (VEFI) sensors on the satellite. Thirty seconds after the burn, the exhaust cloud reach C/NOFS and engulfed the satellite providing very strong electric field turbulence along with enhancements in electron and ion densities. Kinetic modeling has been used to track the electric field turbulence to an unstable velocity distribution produced after the supersonic exhaust molecules charge exchanged with ambient oxygen ions. Based on the success of the first SEITE mission, a second dedicated burn of the OMS engine was scheduled to intercept the C/NOFS satellite, this time at an initial range of 430 km. The trajectory of this exhaust cloud was not centered on the satellite so the turbulent edge was sampled by the C/NOFS instruments. The electromagnetic pulse and the in situ plasma turbulence was recorded during the second SEITE experiment. A comparison of the data from the two OMS burns shows that a wide range of plasma waves are consistently produced with rocket engines are fired in the ionosphere.

  3. Simulations and observations of plasma depletion, ion composition, and airglow emissions in two auroral ionospheric depletion experiments

    NASA Technical Reports Server (NTRS)

    Yau, A. W.; Whalen, B. A.; Harris, F. R.; Gattinger, R. L.; Pongratz, M. B.

    1985-01-01

    Observations of plasma depletion, ion composition modification, and airglow emissions in the Waterhole experiments are presented. The detailed ion chemistry and airglow emission processes related to the ionospheric hole formation in the experiment are examined, and observations are compared with computer simulation results. The latter indicate that the overall depletion rates in different parts of the depletion region are governed by different parameters.

  4. Properties of convective cells generated in magnetized toroidal plasmas

    SciTech Connect

    Theiler, C.; Loizu, J.; Furno, I.; Fasoli, A.; Ricci, P. [Centre de Recherches en Physique des Plasmas-Ecole Polytechnique Federale de Lausanne (EPFL), Association EURATOM-Confederation Suisse, CH-1015 Lausanne (Switzerland)

    2012-08-15

    Convective cells for turbulence control, generated by means of biased electrodes, are investigated in the simple magnetized toroidal plasmas of TORPEX. A two-dimensional array of 24 electrodes is installed on a metal limiter to test different biasing schemes. This allows influencing significantly both radial and vertical blob velocities. It is shown that these changes agree quantitatively with the flows deduced from the time averaged potential perturbations induced by the biasing. Detailed measurements along and across the magnetic field provide a rather clear picture of the effect of biasing on time averaged profiles. The biased electrodes produce perturbations of the plasma potential and density profiles that are fairly uniform along the magnetic field. Background flows influence the location where potential variations are induced. The magnitude of the achievable potential variations in the plasma is strongly limited by cross-field currents and saturates at large bias voltages once the electrodes draw electron saturation current. A quantitative discussion on the origin of cross-field currents is presented, considering contributions related with diamagnetic drifts, ion inertia, collisions with neutrals, and viscosity.

  5. Plasma flux and gravity waves in the midlatitude ionosphere during the solar eclipse of 20 May 2012

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Wu, Chen; Huang, Xueqin; Zhao, Zhengyu; Zhong, Dingkun; Qi, Hao; Huang, Liang; Qiao, Lei; Wang, Jin

    2015-04-01

    The solar eclipse effects on the ionosphere are very complex. Except for the ionization decay due to the decrease of the photochemical process, the couplings of matter and energy between the ionosphere and the regions above and below will introduce much more disturbances. Five ionosondes in the Northeast Asia were used to record the midlatitude ionospheric responses to the solar eclipse of 20 May 2012. The latitude dependence of the eclipse lag was studied first. The foF2 response to the eclipse became slower with increased latitude. The response of the ionosphere at the different latitudes with the same eclipse obscuration differed from each other greatly. The plasma flux from the protonsphere was possibly produced by the rapid temperature drop in the lunar shadow to make up the ionization loss. The greater downward plasma flux was generated at higher latitude with larger dip angle and delayed the ionospheric response later. The waves in the foEs and the plasma frequency at the fixed height in the F layer are studied by the time period analytic method. The gravity waves of 43-51 min center period during and after the solar eclipse were found over Jeju and I-Cheon. The northward group velocity component of the gravity waves was estimated as ~108.7 m/s. The vertical group velocities between 100 and 150 km height over the two stations were calculated as ~5 and ~4.3 m/s upward respectively, indicating that the eclipse-induced gravity waves propagated from below the ionosphere.

  6. The Skylab barium plasma injection experiments. I - Convection observations

    NASA Technical Reports Server (NTRS)

    Wescott, E. M.; Stenbaek-Nielsen, H. C.; Davis, T. N.; Peek, H. M.

    1976-01-01

    Two barium-plasma injection experiments were carried out during magnetically active periods in conjunction with the Skylab 3 mission. The high-explosive shaped charges were launched near dawn on November 27 and December 4, 1973, UT. In both cases, the AE index was near 400 gammas, and extensive pulsating auroras covered the sky. The first experiment, Skylab Alpha, occurred in the waning phase of a 1000-gamma substorm, and the second, Skylab Beta, occurred in the expansive phase of an 800-gamma substorm. In both, the convection was generally magnetically eastward, with 100-km-level electric fields near 40 mV/m. However, in the Alpha experiment the observed orientation of the barium flux tube fit theoretical field lines having no parallel current, but the Beta flux-tube orientation indicated a substantial upward parallel sheet current.

  7. Decay of 3-m-scale ionospheric irregularities associated with a plasma bubble observed with the Equatorial Atmosphere Radar

    Microsoft Academic Search

    Susumu Saito; Shoichiro Fukao; Mamoru Yamamoto; Yuichi Otsuka; Takashi Maruyama

    2008-01-01

    We investigated the decay processes of 3-m-scale ionospheric irregularities associated with plasma bubbles by multi-instrument observations. The observations were made using the Equatorial Atmosphere Radar (EAR), a 630-nm airglow imager, and ionosondes. The EAR's electronic beam steering capability allowed us to see the temporal evolution of 3-m-scale irregularities associated with plasma bubbles in two-dimensional views. Around midnight on 28 and

  8. The thresholds of ionospheric plasma instabilities pumped by high-frequency radio waves at EISCAT

    NASA Astrophysics Data System (ADS)

    Bryers, C. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.

    2013-11-01

    We test the existing theories regarding the thresholds for the parametric decay instability (PDI), the oscillating two-steam instability (OTSI), and the thermal parametric instability (TPI) using the European Incoherent Scatter (EISCAT) facility's ionospheric heater. In these processes, the pump wave can couple to various electrostatic waves in the F layer ionosphere, which can be observed using the EISCAT UHF radar (PDI and OTSI) or by HF radar (TPI). On 19 October 2012, the heater power was stepped from ˜0.5 MW to ˜100 MW effective radiated power in seven steps using a 1 min on, 1 min off cycle. We use an electric field model, taking into account D region absorption, to compare theory with our observations. In all three cases, we find good agreement. In addition, the growth of striations formed during the TPI causes anomalous absorption of the heater wave, which we observe as decreased UHF ion line and plasma line backscatter power. We show evidence that heating for a prolonged period of time reduces the UHF ion line intensity throughout the experiment.

  9. The 10 sheath-accelerated electrons and ions. [atmospheric models of plasma sheaths and ionospheric electron density

    NASA Technical Reports Server (NTRS)

    Shawhan, S. D.

    1975-01-01

    A model is presented that suggests that plasma sheaths form between the ionospheric plasma moving with Io and the ambient plasma corotating with Jupiter. Potentials across these sheaths could be as high as 580 kV which is the motional emf across Io's ionosphere. Electrons and ions can be accelerated across these sheaths. The sheaths may exist at the top of the Io ionosphere with characteristic thicknesses of 1/4 kilometers. The model is consistent with the Pioneer observations of 0.15 MeV electrons at the inner edge of Io's L-shell and the enhanced number density of low-energy protons at the outer edge. Ion sputtering of the Io surface is discussed and may explain the presence of atomic hydrogen and sodium in the vicinity of Io. Also these accelerated particles may be important to the formation of the Io ionosphere. High electron flux which may lead to decametric radio emissions, Jovian atmospheric heating and optical and X-ray emissions is also discussed.

  10. Initial ionospheric observations made by the new Resolute incoherent scatter radar and comparison to solar wind IMF

    NASA Astrophysics Data System (ADS)

    Bahcivan, Hasan; Tsunoda, Roland; Nicolls, Michael; Heinselman, Craig

    2010-08-01

    The first Resolute incoherent scatter radar observations of the polar ionospheric F region show the fine control of the ionospheric plasma density and flow (electric field) by the solar wind interplanetary magnetic field (IMF). A summary of 8 days of observations is presented and 10 IMF Bz southward turning events during this period are analyzed in terms of the time delay of plasma density enhancements and ionospheric convection intensification with respect to the timing of Bz southward turning. We find that Ne enhancements are strongly tied to strong ($\\gtrsim$5 nT) IMF Bz southward turnings; arrive 25-75 mins (depending on MLT) after the IMF pulse arrives at the bowshock nose; last as long as Bz stays southward; contain as small as ˜25 km horizontal substructures; are altitudinally smooth, a characteristic of a solar produced plasma. The most predictable response of ionospheric convection is anti-sunward flow intensification on average ˜25 mins after Bz southward change.

  11. Ionospheric electron-content measurements during the second space-plasma negative-ion experiment (SPINEX-2)

    NASA Technical Reports Server (NTRS)

    Fulford, J. A.; Macdougall, J. W.; Forsyth, P. A.; Mendillo, M.; Bernhardt, P. A.

    1987-01-01

    The second space-plasma negative-ion experiment (SPINEX-2), a chemical-release active experiment to investigate negative-ion effects in the ionospheric F region, is described by Mendillo et al. (1982). This paper describes the electron-content measurements in somewhat more detail than would be appropriate there. The circumstances of the experiment, particularly the use of a vehicle with a very high spin rate, presented some unusual challenges during interpretation of the electron-content data. These are described. The resulting profiles show clearly that the chemical release caused a very significant 'hole' in the ionosphere. Under certain fairly realistic assumptions, the actual number of free electrons removed from the region of the peak of the ionospheric F layer is estimated to be about 4 x 10 to the 25th. The same assumptions lead to a simple radial distribution of the depleted region about the rocket trajectory in the neighborhood of the release.

  12. Investigation of the plasma bubble and blob connection in the low latitude ionosphere

    NASA Astrophysics Data System (ADS)

    Oh, S. J.; Kil, H.; Miller, E. S.

    2014-12-01

    The creation mechanism of plasma bubbles in the low latitude ionosphere is still under debate. Model simulations showed the creation of blobs off the magnetic equator as a consequence of the generation of bubbles. A recent study showed the co-existence of bubbles and blobs and supported the model simulation results. However, the frequent detection of blobs far beyond the bubble apex height and during solar minimum is difficult to explain by the bubble-blob connection hypothesis. In this study, we investigate the causal relationship between bubbles and blobs by analyzing the coincident C/NOFS and radar observations. The optical observations from space by the DMSP/SSUSI will also be used to identify the existence of bubbles at the time of the blob detection.

  13. Comparison of NeQuick, PIM, and TSM model results for the topside ionospheric plasma scale and transition heights

    NASA Astrophysics Data System (ADS)

    Stankov, S. M.; Marinov, P.; Kutiev, I.

    The topside ionospheric scale height (Ts) and the O+ H+ transition height (Th) are key ionospheric characteristics that are of special interest when studying and modelling the plasma composition and dynamics. Recently, a new Topside Sounder Model (TSM) has been developed which provides the Ts and Th quantities together with the ratio between them, Ts/Th. The database for this model has been built upon thousands of Ts and Th values deduced from electron density profiles retrieved from topside sounding measurements. For validation purposes, it would be interesting to compare calculations of the ionospheric scale/transition heights from TSM with corresponding calculations from two other well-known models the NeQuick Model (NeQ) and the Parameterized Ionospheric Model (PIM). For the purpose, electron density profiles have been computed with both the NeQuick and PIM models over suitable grids of input parameters such as month, local time, geomagnetic latitude, solar activity, and in the altitude range between 200 and 2000 km. The topside ionospheric scale height and the O+ H+ transition height values have been extracted from each profile in the same manner as previously done for the TSM development database. Finally, the Ts and Th values deduced from the NeQuick and PIM profiles have been compared with the respective values provided by the TSM. Results of this comparison are analysed and suggestions are put forward for further improving the models in question. TSM applications are discussed as well.

  14. Chirped dissipative ion-cyclotron solitons in the Earth's low-altitude ionospheric plasma with two ion species

    SciTech Connect

    Kovaleva, I. Kh. [Russian Academy of Sciences, Institute of Geosphere Dynamics (Russian Federation)] [Russian Academy of Sciences, Institute of Geosphere Dynamics (Russian Federation)

    2013-03-15

    Conditions for the excitation of small-scale nonlinear ion-cyclotron gradient-drift dissipative structures in cold ionospheric plasma are considered. The solution for the wave electric field in this structure in the form of a chirped soliton satisfying the equation of the Ginzburg-Landau type is derived in the electrostatic approach. The dissipative structure as a whole represents the chirped soliton accompanied by the comoving quasineutral plasma hump. The possibility of the excitation of two modes of this type (the high- and low-frequency ones) in plasma containing light and heavy ion impurities is considered. The role of electromagnetic corrections and the possible contribution introduced by these structures to the transport processes in the ionosphere are discussed.

  15. Mechanisms of Ionospheric Mass Ejection

    NASA Technical Reports Server (NTRS)

    Moore, Thomas Earle; Khazanov, George V.; Hannah, Mei-Ching; Glocer, Alex

    2010-01-01

    Ionospheric outflows are directly responsive to solar wind disturbances, particularly in the dayside auroral cusp or cleft regions. Inputs of both electromagnetic energy (Poynting flux) and kinetic energy (particle precipitation) are closely correlated with these outflows. We assess the importance of processes thought to drive ionospheric outflows. These begin with the diffuse effects of photoionization and thermal equilibrium of the ionospheric topside, enhancing Jeans' escape, with ambipolar diffusion and acceleration. Auroral outflows begin with dayside reconnexion and resultant field-aligned currents and driven convection. These produce plasmaspheric plumes, collisional heating and wave-particle interactions, centrifugal acceleration, and auroral acceleration by parallel electric fields, including enhanced ambipolar fields from electron heating by precipitation particles. Solar wind energy dissipation is concentrated by the geomagnetic field into auroral regions with an amplification factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Internal plasmas thus enable electromagnetic driving via coupling to the plasma and neutral gas. We assess the importance of each of these processes in terms of local escape flux production as well as global outflow, and suggest methods for their implementation within multi-species global simulation codes. We conclude by assessing outstanding obstacles to this objective.

  16. Mechanisms of Ionospheric Mass Escape

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Khazanov, G. V.

    2010-01-01

    The dependence of ionospheric O+ escape flux on electromagnetic energy flux and electron precipitation into the ionosphere is derived for a hypothetical ambipolar pick-up process, powered the relative motion of plasmas and neutral upper atmosphere, and by electron precipitation, at heights where the ions are magnetized but influenced by photo-ionization, collisions with gas atoms, ambipolar and centrifugal acceleration. Ion pick-up by the convection electric field produces "ring-beam" or toroidal velocity distributions, as inferred from direct plasma measurements, from observations of the associated waves, and from the spectra of incoherent radar echoes. Ring-beams are unstable to plasma wave growth, resulting in rapid relaxation via transverse velocity diffusion, into transversely accelerated ion populations. Ion escape is substantially facilitated by the ambipolar potential, but is only weakly affected by centrifugal acceleration. If, as cited simulations suggest, ion ring beams relax into non-thermal velocity distributions with characteristic speed equal to the local ion-neutral flow speed, a generalized "Jeans escape" calculation shows that the escape flux of ionospheric O+ increases with Poynting flux and with precipitating electron density in rough agreement with observations.

  17. The flow of plasma in the solar terrestrial environment

    NASA Technical Reports Server (NTRS)

    Schunk, R. W.; Birmingham, T. J.

    1992-01-01

    The scientific goals of the program are outlined, and some of the papers submitted for publication within the last six months are briefly highlighted. Some of the topics covered include ionosphere-magnetosphere coupling, polar cap arcs, polar wind, convection vortices, ionosphere-plasmasphere coupling, and the validity of macroscopic plasma flow models.

  18. Global circulation and temperature structure of thermosphere with high-latitude plasma convection

    Microsoft Academic Search

    R. G. Roble; R. E. Dickinson; E. C. Ridley

    1982-01-01

    The thermospheric general circulation model of the NCAR is used in an examination of the effect of magnetospheric convection in modifying the diurnal neutral gas temperature distribution and circulation of the thermosphere during equinox conditions. Differences in temperature structure and circulation are illustrated by numerical experiments for the cases due to solar heating, solar heating plus plasma convection with coincident

  19. Ionospheric climatology over Brazil: Zonal plasma velocities from experimental observations and theoretical validations

    NASA Astrophysics Data System (ADS)

    Sobral, José

    We present model calculations and experimental estimations of the zonal drift velocities over Brazil. The latter ones are derived from plasma bubbles signatures on OI6300 ? airglow images A obtained at the conjugate stations Boa Vista - BV (Geogr. 2.8N, 60.7W, dip angle: 22.0N ) and Campo Grande - CG (Geogr. 20.5S, 54.7W, dip angle: 22.32S) during the Conjugate Points Experiment COPEX carried out in Brazil between October and November 2002. Simultaneous velocities as derived by VHF and GPS techniques are also presented and compared. The theoretical ambient plasma zonal velocities were calculated using the formulations by Haerendel et al. (1992) and Eccles (1998) for which the input parameters were based on the available empirical models for zonal electric field (Scherliess and Fejer, 1999), horizontal winds (HWM- 1993), neutral constituents (MSIS-1990) and ionospheric parameters (IRI-2001). The model results show reasonable correlation coefficients between observed and predicted values. However relatively large discrepancies of magnitudes are found between them.

  20. Radial convection of finite ion temperature, high amplitude plasma blobs

    NASA Astrophysics Data System (ADS)

    Wiesenberger, M.; Madsen, J.; Kendl, A.

    2014-09-01

    We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width, and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very well described by the ratio of the ion gyroradius to the characteristic gradient scale length of the blob. We compare the global gyrofluid model with a partly linearized local model. For low ion temperatures, we find that simulations of the global model show more coherent blobs with an increased cross-field transport compared to blobs simulated with the local model. The maximal blob amplitude is significantly higher in the global simulations than in the local ones. When the ion temperature is comparable to the electron temperature, global blob simulations show a reduced blob coherence and a decreased cross-field transport in comparison with local blob simulations.

  1. Radial convection of finite ion temperature, high amplitude plasma blobs

    SciTech Connect

    Wiesenberger, M., E-mail: Matthias.Wiesenberger@uibk.ac.at; Kendl, A. [Institute for Ion Physics and Applied Physics, Association EURATOM-ÖAW, University of Innsbruck, A-6020 Innsbruck (Austria); Madsen, J. [Association EURATOM-DTU, Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby (Denmark)

    2014-09-15

    We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width, and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very well described by the ratio of the ion gyroradius to the characteristic gradient scale length of the blob. We compare the global gyrofluid model with a partly linearized local model. For low ion temperatures, we find that simulations of the global model show more coherent blobs with an increased cross-field transport compared to blobs simulated with the local model. The maximal blob amplitude is significantly higher in the global simulations than in the local ones. When the ion temperature is comparable to the electron temperature, global blob simulations show a reduced blob coherence and a decreased cross-field transport in comparison with local blob simulations.

  2. Study of plasma natural convection induced by electron beam in atmosphere [

    SciTech Connect

    Deng, Yongfeng, E-mail: yfdeng@mail.dlut.edu.cn; Han, Xianwei [Shaanxi Power Machine Design and Research Institute, Xi'an 710100 (China); Tan, Yonghua [Academy of Aerospace Propulsion Technology, Xi'an 710100 (China)

    2014-06-15

    Using high-energy electron beams to ionize air is an effective way to produce a large-size plasma in the atmosphere. In particular, with a steady-state high power generator, some unique phenomena can be achieved, including natural convection of the plasma. The characteristics of this convection are studied both experimentally and numerically. The results show that an asymmetrical temperature field develops with magnitudes that vary from 295?K to 389?K at a pressure of 100?Torr. Natural convection is greatly enhanced under 760?Torr. Nevertheless, plasma transport is negligible in this convection flow field and only the plasma core tends to move upward. Parameter analysis is performed to discern influencing factors on this phenomenon. The beam current, reflecting the Rayleigh number Ra effect, correlates with convection intensity, which indicates that energy deposition is the underlying key factor in determining such convections. Finally, natural convection is concluded to be an intrinsic property of the electron beam when focused into dense air, and can be achieved by carefully adjusting equipment operations parameters.

  3. Magnetosheath-ionospheric plasma interactions in the cusp/cleft. 1: Observations of modulated injections and upwelling ion fluxes

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Menietti, J. D.; Peterson, W. K.; Burch, J. L.; Waite, J. H., Jr.; Giles, B.

    1993-01-01

    In situ observations of the cusp/cleft are important as they allow a direct investigation of coupling solar wind energy to the ionosphere, plus they provide an opportunity for the remote sensing of the magnetopause. High time resolution observations from Dynamic Explorer 1 are used to investigate these processes. It is shown that in the spacecraft frame the injection is modulated or pulsating with a period of approximately 18-30 s with the injection duration possibly being as short as 6 s. This modulation indicates that there may be fast time scale and/or short scale length processes modulating the injection of the magnetosheath plasma across the magnetopause. In addition, the pulsating injection is seen to modulate the outflow of upwelling ionospheric ions to the magnetosphere. These upwelling ions are seen prior to the magnetosheath ion injection and therefore are not directly created by the injection. During the injection itself, the intensity of the upwelling ions is seen to dramatically decrease but their average energy increases. At end of the magnetosheath injections, the intensity of the upwelling ion flux is seen to increase to levels comparable to levels prior to the magnetosheath injection. On two occasions during the encounter, the particle fluxes are sufficiently high that enhanced downward flows of perpendicularly heated ions, of presumably ionospheric origin, are observed in association with a reduction in the intensity of the upwelling ions. These observations are probably the first detection of downward conics and suggest that there is momentum transfer between the magnetosheath and ionospheric ions. This momentum transfer eventually leads to an enhanced outflow of heated ionospheric plasma where their energy has been raised from a few tens of eV to a few hundred eV.

  4. Large plasma pressure perturbations and radial convective transport in a tokamak

    Microsoft Academic Search

    KRASHENINNIKOV Sergei; RYUTOV Dmitri; YU Guanghui

    2004-01-01

    Strongly localized plasma structures with large pressure inhomogeneities (such as plasma blobs in the scrape-off-layer (SOL)\\/shadow regions, pellet clouds, ELMs) observed in the tokamaks, stellarators and linear plasma devices. Experimental studies of these phenomena reveal striking similarities including more convective rather than diffusive radial plasma transport. We suggest that rather simple models can describe many essentials of blobs, ELMs, and

  5. Ionospheric storm time dynamics as seen by GPS tomography and in situ spacecraft observations

    NASA Astrophysics Data System (ADS)

    Pokhotelov, D.; Mitchell, C. N.; Spencer, P. S. J.; Hairston, M. R.; Heelis, R. A.

    2008-03-01

    During major geomagnetic storms anomalous enhancements of the ionospheric density are seen at high and middle latitudes. A number of physical mechanisms have been invoked to explain these storm time density anomalies including an expansion of high-latitude electric plasma convection to midlatitudes, thermospheric neutral winds, and changes in the ionospheric composition. However, it remains unclear which mechanism plays the dominant role in the formation of storm time density anomalies, partly because of insufficient coverage of the measurements of global electric convection and thermospheric winds at midlatitudes. This paper describes a novel technique for extracting the storm time E × B convection boundary from in situ measurements of plasma bulk motion obtained by LEO DMSP satellites. The convection boundary estimated from the DMSP data during major magnetic storm of 20 November 2003 has been compared with the global distributions of the ionospheric plasma deduced from characteristics of GPS signals acquired by a ground-based network of GPS receivers. The tomographic inversion of GPS data using a three-dimensional time-dependent inversion technique reveals the spatial and temporal evolution of the storm time density anomaly. Comparison between the tomographic reconstructions of the ionospheric plasma distributions and in situ DMSP measurements of plasma bulk motion suggests that the convective flow expanded low enough in latitude to encompass, in part, the formation of the midlatitude TEC anomaly. Some features of the TEC dynamics observed during the 20 November 2003 storm, however, suggest that mechanisms other than the expanded ionospheric convection (such as thermospheric neutral winds) are also involved in the formation of the midlatitude anomaly.

  6. Plasma convection induced by toroidal asymmetries of the divertor plates and gas puffing

    Microsoft Academic Search

    R. H. Cohen; D. D. Ryutov

    1997-01-01

    In the open field line region of the scrape-off layer (SOL), the plasma potential is to a considerable degree determined by the boundary conditions on the divertor plates. The idea is explored here that, by making the divertor plates slightly `wavy' in the toroidal direction, toroidally varying potentials can be produced throughout the SOL and thereby convective plasma motion induced.

  7. Modeling the transition of the inner plasma sheet from weak to enhanced convection

    Microsoft Academic Search

    Chih-Ping Wang; Larry R. Lyons; Margaret W. Chen; Frank R. Toffoletto

    2004-01-01

    We seek to determine whether the adiabatic plasma transport and energization resulting from electric and magnetic drift can quantitatively account for the plasma sheet under weak and enhanced convection observed by Geotail presented in the companion paper [Wang et al., 2004]. We use a modified Magnetospheric Specification Model to simulate the dynamics and distributions of protons originating from the deep

  8. Fundamental Features of Solar Wind-Magnetosphere-Ionosphere Coupling Revealed by High-Latitude Incoherent-Scatter Radars

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Zou, S.; Heinselman, C.; Nico, M.; McCready, M.

    2007-12-01

    Important features of solar wind-magnetosphere-ionosphere coupling can be observed within the ionosphere, where accessibility to ground-based observation allows decoupling of space-time ambiguities that are inherent to spacecraft observations. Incoherent-scatter radars (ISRs) make an important contribution to these ground- based observations by being able to reliably measure plasma flows and electron densities over areas of the ionosphere. These radars have provided critical measurements of the strength and changes of dayside convection imparted to the magnetosphere-ionosphere system by the interplanetary plasma and its changes, as well as of the transfer of polar cap flows to closed field lines that is associated with nightside reconnection. ISR measurement of the nightside flow transfer, complemented by SuperDARN radar observations, provided the first evidence of localized bursts of strongly enhanced nightside convection that lead to auroral poleward boundary intensifications, which are now known to be a major and frequently occurring disturbance of the magnetosphere- ionosphere system. With the recent addition of the ISR at Poker Flat, Alaska, we now have the capability of observing the detailed evolution of electric fields and auroral induced ionization within the nightside auroral oval, which is the ionospheric mapping of the tail plasma sheet. The energy-dependent magnetic drift of plasma sheet ions leads to a divergence of particles, and thus also of cross-tail current. This current divergence leads to the Region 2 field-aligned system and to major changes in magnetosphere-ionosphere convection, which are associated with shielding, formation of the Harang reversal, and are critical to the development of substorms and the stormtime ring current. By combining Poker Flat observations with higher latitude ISR observations, we have implemented a program to observe the Region 2 evolution in response to changes in polar cap convection and initial results show the promise of yielding much new understanding of the evolution of the Region 2 system and its effects on convection

  9. Mapping High-Latitude Ionospheric Current System Based on Ground Magnetometers and Other Data Sets

    NASA Astrophysics Data System (ADS)

    Lu, G.

    2014-12-01

    Because the ionosphere and magnetosphere are intrinsically coupled along magnetic field lines, the polar ionosphere provides a viewing screen for the large-scale electrodynamics of the magnetosphere. Distributions of ionospheric convection, electric currents, and auroral precipitation are determined by several magnetospheric processes, such as the location and rate of magnetic reconnection along the magnetopause and in the magnetotail, and the energization and precipitation of magnetospheric plasmas. This paper demonstrates the utility of the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure in obtaining global, large-scale distributions of ionospheric horizontal currents as well as the associated field-aligned currents based on ground magnetometers, together with various space and other ground based observations. In particular, we will investigate the current system associated with the Harang Discontinuity.

  10. Convection-driven delivery of plasma sheet material to the inner magnetosphere.

    NASA Astrophysics Data System (ADS)

    Denton, M. H.; Thomsen, M. F.; Lavraud, B.; Skoug, R. M.; Henderson, M. G.; Funsten, H. O.; Jahn, J.; Pollock, C. J.; Weygand, J.

    2005-12-01

    We present data from the MENA instrument onboard the IMAGE satellite taken during a period of enhanced convection on 26 June 2001. During the interval, MENA observes energetic neutral atoms (ENAs) in the magnetotail and an Earthwards-propagating enhancement in their flux, at the same time as the convection strength increases (as measured by the Kp and MBI indices). Data from the magnetospheric plasma analyser (MPA) instrument onboard satellites in geosynchronous orbit indicate that enhanced ion and electron fluxes at plasma sheet energies (~1-45 keV) are detected at the same time as enhanced ENA flux are observed at the satellite location. We interpret the results as a convection-driven delivery of plasma sheet material, the ENA signature of which we observe with IMAGE/MENA. We use the rate of the propagation of the ENA enhancement to infer the speed of the plasma sheet delivery to the inner magnetosphere.

  11. Inductive-dynamic magnetosphere-ionosphere coupling via MHD waves

    NASA Astrophysics Data System (ADS)

    Tu, Jiannan; Song, Paul; Vasyli?nas, Vytenis M.

    2014-01-01

    In the present study, we investigate magnetosphere-ionosphere/thermosphere (M-IT) coupling via MHD waves by numerically solving time-dependent continuity, momentum, and energy equations for ions and neutrals, together with Maxwell's equations (Ampère's and Faraday's laws) and with photochemistry included. This inductive-dynamic approach we use is fundamentally different from those in previous magnetosphere-ionosphere (M-I) coupling models: all MHD wave modes are retained, and energy and momentum exchange between waves and plasma are incorporated into the governing equations, allowing a self-consistent examination of dynamic M-I coupling. Simulations, using an implicit numerical scheme, of the 1-D ionosphere/thermosphere system responding to an imposed convection velocity at the top boundary are presented to show how magnetosphere and ionosphere are coupled through Alfvén waves during the transient stage when the IT system changes from one quasi steady state to another. Wave reflection from the low-altitude ionosphere plays an essential role, causing overshoots and oscillations of ionospheric perturbations, and the dynamical Hall effect is an inherent aspect of the M-I coupling. The simulations demonstrate that the ionosphere/thermosphere responds to magnetospheric driving forces as a damped oscillator.

  12. Equatorial plasma bubbles in the ionosphere over Eritrea: occurrence and drift speed

    NASA Astrophysics Data System (ADS)

    Wiens, R. H.; Ledvina, B. M.; Kintner, P. M.; Afewerki, M.; Mulugheta, Z.

    2006-07-01

    An all-sky imager was installed in Asmara, Eritrea (15.4° N, 38.9° E, 7° N dip) and used to monitor the OI 630-nm nightglow. Nine months of data were studied between September 2001 and May 2002, a time including the recent maximum in the solar activity cycle. Equatorial plasma bubbles (EPBs) were recorded on 63% of nights with adequate viewing conditions. The station location within view of the equatorial ionization anomaly and with a magnetic declination near zero makes it an excellent test case for comparison with satellite studies of the seasonal variation of EPBs with longitude. The imager was accompanied by two Cornell GPS scintillation monitors, and the amplitude scintillation data are compared to the all-sky data. GPS scintillations indicate the beginning of EPBs, but die out sooner in the post-midnight period than the larger scale EPBs. Both phenomena exhibit clear occurrence maxima around the equinoxes. Ionospheric zonal drift speeds have been deduced from EPB and GPS scintillation pattern movement. Average near-midnight EPB drift speeds are between 100 and 120 m/s most months, with the GPS scintillation speeds being about the same. A winter drift speed maximum is evident in both EPB and GPS scintillation monthly means.

  13. Simulations and observations of plasma depletion, ion composition, and airglow emissions in two auroral ionospheric depletion experiments

    SciTech Connect

    Yau, A.W.; Whalen, B.A.; Harris, F.R.; Gattinger, R.L.; Pongratz, M.B.; Bernhardt, P.A.

    1985-09-01

    In an ionospheric depletion experiment where chemically reactive vapors such as H/sub 2/O and CO/sub 2/ are injected into the O/sup +/ dominant F region to accelerate the plasma recombination rate and to reduce the plasma density, the ion composition in the depleted region is modified, and photometric emissions are produced. We compare in situ ion composition, density, and photometric measurements from two ionospheric depletion experiments with predictions from chemical modeling. The two injections, Waterhole I and III, were part of an auroral perturbation experiment and occurred in different ambient conditions. In both injections a core region of greater than fivefold plasma depletion was observed over roughly-equal5-km diameter within seconds of the injection, surrounded by an outer region of less drastic and slower depletion. In Waterhole I the plasma density was depleted tenfold over a 30-km diamter region after 2 min. The ambient O/sup +/ density was drastically reduced, and the molecular O/sup +//sub 2/ abundance was enhanced fivehold in the depletion region. OH airglow emission associated with the depletion was observed with a peak emission intensity of roughly-equal1 kR. In Waterhole III the ambient density was a decade lower, and the plasma depletion was less drastic, being twofold over 30 km after 2 min. The airglow emissions were also much less intense and below measurement sensitivity (30 R for the OH 306.4-nm emission; 50 R for the 630.0-nm emission).

  14. A multi-instrument case study of high-latitude ionospheric GNSS scintillation due to drifting plasma irregularities

    NASA Astrophysics Data System (ADS)

    van der Meeren, C.; Oksavik, K.; Moen, J. I.; Romano, V.

    2013-12-01

    For this study, GPS receiver scintillation and Total Electron Content (TEC) data from high-latitude locations on Svalbard have been combined with several other data sets, including the EISCAT Svalbard Radar (ESR) and allsky cameras, to perform a multi-instrument case study of high-latitude GPS ionospheric scintillations in relation to drifting plasma irregularities at night over Svalbard on 31 October 2011. Scintillations are rapid amplitude and phase fluctuations of electromagnetic signals. GNSS-based systems may be disturbed by ionospheric plasma irregularities and structures such as plasma patches (areas of enhanced electron density in the polar cap) and plasma gradients. When the GNSS radio signals propagate through such areas, in particular gradients, the signals experience scintillations that at best increases positioning errors and at worst may break the receiver's signal lock, potentially resulting in the GNSS receiver losing track of its position. Due to the importance of many GNSS applications, it is desirable to study the scintillation environment to understand the limitations of the GNSS systems. We find scintillation mainly localised to plasma gradients, with predominantly phase scintillation at the leading edge of patches and both phase and amplitude scintillation at the trailing edge. A single edge may also contain different scintillation types at different locations.

  15. Large plasma pressure perturbations and radial convective transport in a tokamak

    SciTech Connect

    Krasheninnikov, S; Ryutov, D; Yu, G

    2004-02-04

    Strongly localized plasma structures with large pressure inhomogeneities (such as plasma blobs in the scrape-off-layer (SOL)/shadow regions, pellet clouds, ELMs) observed in the tokamaks, stellarators and linear plasma devices. Experimental studies of these phenomena reveal striking similarities including more convective rather than diffusive radial plasma transport. We suggest that rather simple models can describe many essentials of blobs, ELMs, and pellet clouds dynamics. The main ingredient of these models is the effective plasma gravity caused by magnetic curvature, centrifugal or friction forces effects. As a result, the equations governing plasma transport in such localized structures appear to be rather similar to that used to describe nonlinear evolution of thermal convection in the Boussinesq approximation (directly related to the Rayleigh-Taylor instability).

  16. Equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Rastogi, R. G.

    1990-12-01

    The development of research in E and F regions of the ionosphere in India since about 1950 is briefly described. The various geomagnetic factors controlling the F region at low latitudes during quiet, disturbed days, on different ages of the moon are described. The equatorial electrojet current, its association with general Sq currents, geomagnetic disturbance and solar disturbance are shown due to changes of the electric fields at the equator. The phenomenon of spread-F at low latitudes is shown to be associated with the regeneration of equatorial plasma fountain during the post sunset hours similar to the daytime plasma fountain associated with equatorial ionization anomaly. The narrow belt of ionosphere, the magnetic equator, is shown to be very sensitive to electric field of local origin or even to electric field generated at the magnetopause due to the interaction of the solar wind on the earth's magnetosphere.

  17. A New Paradigm for Ionosphere-Thermosphere-Mesosphere Physics

    NASA Astrophysics Data System (ADS)

    Fuller-Rowell, Tim

    2015-04-01

    The ionosphere-thermosphere-mesosphere system is predominantly a neutral atmosphere domain with a fairly small fraction, less than 1%, that is ionized, similar in some ways to the chromosphere. Neutral dynamics and composition therefore play an important role in influencing and controlling the ionospheric plasma density and creating structure. Neutral thermospheric dynamics is driven from both above and below. Absorption of solar extreme ultraviolet radiation drives a global circulation, and magnetosphere/ionosphere plasma convection can accelerate neutral winds in excess of 1 km/s through collisions, and raise gas temperature by hundreds of degrees Kelvin by frictional dissipation. During extreme events these solar and magnetospheric sources dominate the ITM system, and understanding the plethora of physical processes that ensue has been the focus for more than 50 years. However, the bulk of solar energy reaching Earth penetrates well into the lower atmosphere and to the surface. Even if only a small fraction of this large energy reservoir can reach above 100 km it can have a significant impact on the ITM system and its variability. The main dynamic coupling and transfer of energy from below is largely through atmospheric waves, particularly tides (waves with harmonics of the 24 hour solar day), and gravity waves from the multitude of sources in the lower atmosphere. We now appreciate that dynamical changes and warmings in the stratosphere from changes in planetary wave activity can lead to a 50% change in electron content in the ionosphere, and which can actually be forecast days in advance. Tropospheric convection over continental landmass imprints a longitude structure on the ionosphere. Convective adjustment, extreme weather, wind shear, airflow over mountains, are some of the many sources of gravity waves activity that can grow in amplitude as they propagate into the thermosphere where they modulate and tilt the ionosphere. The ITM system is dynamic and variable even during apparently quiescent times, and understanding this new range of physical processes has created a new paradigm.

  18. Ionospheric response to the corotating interaction region-driven geomagnetic storm of October 2002

    NASA Astrophysics Data System (ADS)

    Pokhotelov, D.; Mitchell, C. N.; Jayachandran, P. T.; MacDougall, J. W.; Denton, M. H.

    2009-12-01

    Unlike the geomagnetic storms produced by coronal mass ejections (CMEs), the storms generated by corotating interaction regions (CIRs) are not manifested by dramatic enhancements of the ring current. The CIR-driven storms are however capable of producing other phenomena typical for the magnetic storms such as relativistic particle acceleration, enhanced magnetospheric convection and ionospheric heating. This paper examines ionospheric plasma anomalies produced by a CIR-driven storm in the middle- and high-latitude ionosphere with a specific focus on the polar cap region. The moderate magnetic storm which took place on 14-17 October 2002 has been used as an example of the CIR-driven event. Four-dimensional tomographic reconstructions of the ionospheric plasma density using measurements of the total electron content along ray paths of GPS signals allow us to reveal the large-scale structure of storm-induced ionospheric anomalies. The tomographic reconstructions are compared with the data obtained by digital ionosonde located at Eureka station near the geomagnetic north pole. The morphology and dynamics of the observed ionospheric anomalies is compared qualitatively to the ionospheric anomalies produced by major CME-driven storms. It is demonstrated that the CIR-driven storm of October 2002 was able to produce ionospheric anomalies comparable to those produced by CME-driven storms of much greater Dst magnitude. This study represents an important step in linking the tomographic GPS reconstructions with the data from ground-based network of digital ionosondes.

  19. Parametric Instabilities and Ionospheric Modification

    Microsoft Academic Search

    F. W. Perkins; C. Oberman; E. J. Valeo

    1974-01-01

    Parametric instabilities, excited in the ionosphere by high-power HF transmitters with a frequency below the maximum ionospheric plasma frequency, produce nonlinear energy absorption and enhanced scattering of electromagnetic radiation, which has been detected by the Arecibo Thomson scatter radar. This paper reviews and extends both the linear and nonlinear saturation theory of parametric instabilities within the ionospheric context. The new

  20. Geophysical plasmas and atmospheric modeling

    NASA Astrophysics Data System (ADS)

    Hyman, E.; Chaturvedi, P.; Chen, J.; Drake, J.; Ganguli, G.

    1985-03-01

    Contents: Collisionless Tearing Instability in a Non-Mexwellian Neutral Sheet: An Integro-Differential Formulation; Nonlocal Effects on the Convective Properties of the Electrostatic Current-Driven Ion-Cyclotron Instability; Two Dimensional Nonlocal Formalism for Electrostatic Waves in the Magnetosphere; The Role of Nonlocalities in Magnetosphere-Ionosphere Coupling Processes; O(+) Acceleration Due to Resistive Momentum Transfer in the Auroral Field Line Plasma; Behavior of Ionized Plasma in the High Latitude Topside Ionosphere; Stabilization of the Collisional Current-Driven Ion Cyclotron Instability; Production and Control of Ion Cyclotron Instabilities in the High Latitude Ionosphere by High Power Radio Waves; Effects of Finite Current Channel Width on the Current Convective Instability; Ionospheric Turbulence: Interchange Instabilitiies and Chaotic Fluid Behavior; Estimating Spectral Indices from Transforms of Discrete Representations of Density Functions; Projections of Plasma Structures and Their Spectra; The Role of Finite Parallel Length on the Stability of Barium Clouds; Finite Temperature Stabilization of the Gradient Drift Instability in Barium Clouds; Finite Temperature Effects on the Evolution of Ionospheric Barium Clouds in the Presence of a Conducting Background Ionosphere I. A High Altitude Incompressible Background Ionosphere; and A Three Dimensional Model of the Summer Monsoon.

  1. Radio tomographic imaging of the northern high-latitude ionosphere on a wide geographic scale

    NASA Astrophysics Data System (ADS)

    Kersley, L.; Pryse, S. E.; Denton, M. H.; Bust, G.; Fremouw, E.; Secan, J.; Jakowski, N.; Bailey, G. J.

    2005-10-01

    Several chains of receivers, measuring total electron content (TEC) during passes of satellites in the U.S. Navy Ionospheric Measuring System (NIMS), are operated at northern high latitudes by members of the International Ionospheric Tomography Community (IITC). Results are presented here of nearly simultaneous latitude-altitude images of the ionosphere over Scandinavia, Greenland, and Alaska, generated from IITC data obtained on 20 September 2001 and interpreted in the context of an IMF-dependent convection model. The images are compared with output from a coupled thermosphere-ionosphere-plasmasphere model and also with maps of high-latitude TEC generated from GPS measurements. With Bz and By both weakly negative, the images and map reveal plasma features of a two-cell convection pattern rotated slightly to earlier local magnetic times. The tomographic images provide details of map features such as a tongue of ionization created by solar EUV radiation on the dayside and entrained by convection into the polar cap from the western Russian sector. Combining latitude versus altitude tomographic images generated in different longitudinal sectors from polar-orbiting beacon satellites such as those of NIMS with TEC maps from GPS offers an emerging opportunity for polar aeronomic studies, especially if further related to synoptic convection measurements. The results also demonstrate the potential role of wide-scale radio tomography in the verification of ionospheric models.

  2. Convective Velocity Reversal Caused by Turbulence Transition in Tokamak Plasma

    NASA Astrophysics Data System (ADS)

    Zhong, W. L.; Zou, X. L.; Bourdelle, C.; Song, S. D.; Artaud, J. F.; Aniel, T.; Duan, X. R.

    2013-12-01

    Particle transport has been studied in the Tore Supra tokamak by using modulated ion cyclotron resonance heating to generate perturbations of density and temperature. For the first time, a reversal of the particle convective velocity and a strong increase in the turbulent particle flux have been clearly observed. When the mixed critical gradient ?c=R/LT+4(R /Ln)=22 is exceeded, the particle flux increases sharply and the convective velocity reverses from inward to outward. These observations are in agreement with quasilinear, gyrokinetic calculations. The critical gradient corresponds to a transition from an instability driven by the ion temperature gradient to the onset of another instability caused by trapped electrons.

  3. Ionospheric Alfvén resonator revisited: Feedback instability

    Microsoft Academic Search

    Oleg A. Pokhotelov; V. Khruschev; M. Parrot; S. Senchenkov; V. P. Pavlenko

    2001-01-01

    The theory of ionospheric Alfvén resonator (IAR) and IAR feedback instability is reconsidered. Using a simplified model of the topside ionosphere, we have reanalyzed the physical properties of the IAR interaction with magnetospheric convective flow. It is found that in the absence of the convective flow the IAR eigenmodes exhibit a strong damping due to the leakage of the wave

  4. A Multispacecraft/Instrument Case Study of the Relationship Between the Solar Wind and Ionospheric Plasma Outflow

    NASA Technical Reports Server (NTRS)

    Craven, Paul D.; Chandler, M. O.; Moore, T. E.; Mozer, F.; Russell, C. T.

    2001-01-01

    The study of the relationship between the solar wind and ionospheric plasma outflows is fundamental to understanding the solar- terrestrial relationship. A multi-spacecraft/instrument case study has been carried out to address this relationship. On 11-26-00 the Polar spacecraft made a pass through the southern cleft region near perigee where the Thermal Ion Dynamics Experiment (TIDE) instrument observed a classic Cleft Ion Fountain/upwelling ion signature. These observations followed several pressure pulses from the solar wind as evidenced by observations from the Magnetic Field Instrument (MFI) on the WIND spacecraft. Several interesting electric field features were observed by the Electric Field Instrument (EFI) as Polar appeared to pass through a narrow region of strong currents into a region with significant oscillations at a large range of frequencies. In addition, coincident with the TIDE observations of ion outflow, the low-energy edge of the characteristic V-shape of cusp ion injections was also observed. During this same time frame the Cluster spacecrafts crossed the magnetopause in the dusk sector and observed the electric field signatures associated with this region on all three satellites. This event is addressed in detail to further detail cleft ion fountain source characteristics, to add additional data regarding the hypothesis that solar wind pressure pulses are a trigger for cleft outflow, and to investigate possible interactions among waves, ionospheric plasma, and cusp injected plasma.

  5. Scintillations, plasma drifts, and neutral winds in the equatorial ionosphere after sunset

    NASA Astrophysics Data System (ADS)

    Basu, S.; Kudeki, E.; Basu, Su.; Valladares, C. E.; Weber, E. J.; Zengingonul, H. P.; Bhattacharyya, S.; Sheehan, R.; Meriwether, J. W.; Biondi, M. A.; Kuenzler, H.; Espinoza, J.

    1996-12-01

    An equatorial campaign was conducted during September 25 to October 7, 1994, to investigate the neutral and plasma dynamics in the equatorial ionosphere after sunset in relation to the day-to-day variability of the occurrence of equatorial spread F (ESF). The campaign was organized under the auspices of National Science Foundation's Multi-Instrumented Studies of the Equatorial Thermosphere Aeronomy program (MISETA), which included the Jicamarca radar, spaced-antenna satellite scintillation, digisonde, all-sky imager, and Fabry-Perot interferometer (FPI) measurements near the magnetic equator in Peru. During a part of the period, September 27 to October 3, the Geophysics Directorate of Phillips Laboratory performed measurements away from the magnetic equator at Aguaverde, Chile (magnetic latitude: 11°S) located 800 km to the east of the Jicamarca meridian using geostationary and GPS satellite scintillation, digisonde and all-sky imager systems. The incoherent scatter radar results indicate that the postsunset enhancement of upward plasma drift, even though of the order of only 20ms-1 during the solar minimum period, is a necessary condition for the generation of ESF. In view of the extreme difficulty of determining the neutral wind speed during the early evening hours by the FPI due to low airglow intensity, it was not possible to unequivocally associate the observed postsunset enhancements with strong eastward neutral winds. However, considering a few observations contiguous to the campaign period, it appears that such a causal relationship may exist. The scintillation drift measurements in Peru and Chile indicated that the zonal irregularity drift was smaller away from the magnetic equator implying a variation of neutral wind with latitude. This is reproduced in the altitude variation of zonal drift observed by the Jicamarca radar. During a magnetic storm, scintillation measurements indicated that eastward drifts near the magnetic equator are accompanied by westward drifts near the anomaly peak which is consistent with the effects of a disturbance dynamo. The campaign results indicate that in order to resolve the variability of ESF, a careful probing of neutral dynamics as a function of latitude needs to be undertaken during the postsunset period.

  6. On the cause of X-line formation in the near-Earth plasma sheet: Results of adiabatic convection of plasma-sheet plasma

    NASA Astrophysics Data System (ADS)

    Erickson, G. M.

    Self-consistent, static-equilibrium solutions are presented for two-dimensional magnetospheric-magnetic-field configurations with isotropic thermal pressure. These solutions include a dipole field and are not restricted to the asymptotic theory. Adiabatic convection of plasma sheet flux tubes is modeled as a series of static-equilibrium solutions in which flux tubes conserve their PV? as they convect, which resulted in time dependent magnetospheric configurations. Specifically it is found that a deep minimum in the equatorial Bz develops in the inner plasma sheet, thereby causing the magneticfield configuration to become more stretched and tail-like in time. These results suggest X-line formation in the inner plasma sheet as a consequence of lossless, adiabatic convection of plasma sheet flux tubes.

  7. Reduction of Raman scattering in a plasma to convective levels using induced spatial incoherence

    SciTech Connect

    Obenschain, S.P.; Pawley, C.J.; Mostovych, A.N.; Stamper, J.A.; Gardner, J.H.; Schmitt, A.J.; Bodner, S.E.

    1989-02-13

    We present measurements of the Raman backscatter produced by laser-plasma interaction where the laser focal profile was smoothed by induced spatial incoherence (ISI). The Raman backscatter with the ISI beam is much smaller than that with an ordinary beam. The onset of Raman backscattering with ISI followed the predictions of a convective gain model to within 30% in intensity.

  8. Formation of the Harang reversal and its dependence on plasma sheet conditions: Rice convection model simulations

    E-print Network

    Lyons, Larry

    Formation of the Harang reversal and its dependence on plasma sheet conditions: Rice convection of this paper is to understand the formation of the Harang reversal and its association with the region 2 field for the formation of the Harang reversal. In the overlap region the downward FAC, which is located at lower

  9. A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far-ultraviolet spacecraft observations

    NASA Astrophysics Data System (ADS)

    Park, S. H.; England, S. L.; Immel, T. J.; Frey, H. U.; Mende, S. B.

    2007-11-01

    The Far-Ultraviolet Imager (IMAGE-FUV) on board the NASA IMAGE satellite has been used to observe plasma depletions in the nightside equatorial ionosphere. Observations from periods around spacecraft apogee, during which equatorial regions are visible for several hours, have allowed the velocity of these plasma depletions to be determined. A new method for determining the velocity of these depletions using an image analysis technique, Tracking Of Airglow Depletions (TOAD), has been developed. TOAD allows the objective identification and tracking of depletions. The automation of this process has also allowed for the tracking of a greater number of depletions than previously achieved without requiring any human input, which shows that TOAD is suitable for use with large data sets and for future routine monitoring of the ionosphere from space. Furthermore, this automation allows the drift velocities of each bubble to be determined as a function of magnetic latitude, which will give us the capability of retrieving geophysically important parameters such as the electric field, which are believed to vary rapidly with magnetic latitude.

  10. Ionospheric plasma turbulence over region of 2006 Iran, 2005 Lake Tanganyika and 2010 New Britain Region earthquakes.

    NASA Astrophysics Data System (ADS)

    Kosciesza, Malgorzata; Blecki, Jan; Wronowski, Roman; Parrot, Michel

    2013-04-01

    We report the results of the observation of ELF plasma turbulence registered by DEMETER satellite in the ionosphere over epicenter region of three earthquakes. First one took place on 2nd of February 2005 in Lake Tanganyika Region with magnitude 6.9. Second was earthquake with magnitude 6.1 in Iran on 31st March 2006. The last one took place on 4th of August 2010 in New Britain Region with magnitude 7.0. Obtained results we compare with data gathered during corresponding time and region with quiet seismic conditions. To study this turbulent processes we apply Fourier, wavelet, bispectral analysis and statistical description with use of kurtosis and skewness of the electric field fluctuations. These registrations are correlated with the plasma parameters measured onboard DEMETER satellite and with geomagnetic indices.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  12. Generation of mesoscale convective structures in tokamak edge plasma

    SciTech Connect

    Krasheninnikov, S. I.; Smolyakov, A. I. [University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093 (United States); University of Saskatchewan, 116 Science Place, Saskatoon, Saskatchewan S7N 5E2 (Canada)

    2007-10-15

    It is shown that the interplay of the interchange drive and nonlinear effects of Reynolds stress and inverse cascade of drift wave turbulence select a range of plasma parameters (plasma pressure), for which mesoscale perturbations of a certain transverse length scale become unstable. It is suggested that the blob formation is a result of these mesoscale instabilities.

  13. Effects of ionospheric conductance in high-latitude phenomena

    NASA Astrophysics Data System (ADS)

    Benkevitch, Leonid

    In this thesis, the relationship between several high-latitude phenomena and the ionospheric conductance in both hemispheres is studied theoretically and experimentally. Theoretically, the high-latitude electrodynamics is studied by considering currents in the magnetosphere-ionosphere system resulting from the ionospheric sheet current redistribution between the conjugate ionospheres. It is shown that strong flow between the conjugate ionospheres, the interhemispheric currents (IHC), can be set up if the conductance distribution is asymmetric in the conjugate ionospheric regions. Such conditions are typical for solstices owing to the differences in the solar illumination. Analytical and numerical modeling shows that IHCs can appear in the regions of strong conductance gradient, more specifically around the solar terminator line, and that the intensity of the IHCs can be comparable to the intensity of the well known Region 1/Region 2 currents. The effect of IHC excitation on observable magnetic perturbations on the ground is investigated. It is shown that in the vicinity of the solar terminator line, the pattern of magnetic perturbation can be such that an apparent equivalent current vortex can be detected. In addition, strong conductance gradients are shown to affect significantly the quality of the ionospheric plasma flow estimates from the ground-based magnetometer data. Experimentally, the effect of the nightside ionospheric conductance on occurrence of substorms, global storm sudden commencement and radar auroras is investigated. To characterize substorm occurrence, new parameters, the derivatives of the classical AE and AO indices, are introduced. It is shown that the seasonal and diurnal variations of these parameters are controlled by the total nightside ionospheric conductance in the conjugate regions. The substorm onsets preferentially occur at low levels of the total conductance, which is consistent with the idea of the substorm triggering through the magnetosphere-ionosphere feedback instability. It is hypothesized that the total conductance affects the global storm onsets as well. To check this idea, the 33-year sudden storm commencement (SSC) data are considered. The semiannual, annual, semidiurnal, and diurnal variations in the SSC occurrence rate are found to be significant and these components exhibit a strong relationship with the total conductance of the high-latitude ionospheres. Finally, the SuperDARN midnight echo occurrence is shown to correlate, for some radars, with the total conductance minima and presumably with electric field maxima, which is consistent with general expectation that the F-region irregularities occur preferentially during times of enhanced electric fields. The gradients of the high-latitude conductance can also lead to significant errors in the plasma convection estimates from the ground-based magnetometers, and to investigate this effect a statistical assessment of the difference between the true plasma convection (SuperDARN) and the magnetometer-inferred equivalent convection direction is performed. The largest differences are found for the transition region between the dark and sunlit ionospheres and in the midnight sector where strong conductance gradients are expected due to particle precipitation. Consideration of regular conductance gradients due to solar illumination improves the agreement between the radar and magnetometer data. Finally, an attempt is made to demonstrate the effects of conductance upon the properties of traveling convection vortices (TCVs). Joint SuperDARN and magnetometer data reveal that there is resemblance between the magnetometer and radar inferred TCV images on a scale of thousands of kilometers. However, on a smaller scale of hundreds of kilometers, significant differences are observed.

  14. Divertor E X B Plasma Convection in DIII-D

    SciTech Connect

    Boedo, J.A.; Schaffer, M.J.; Maingi, M.; Lasnier, C.J.; Watkins, J.G.

    1999-07-01

    Extensive two-dimensional measurements of plasma potential in the DIII-D tokamak divertor region are reported for standard (ion VB{sub T} drift toward divertor X-point) and reversed B{sub T} directions; for low (L) and high (H) confinement modes; and for partially detached divertor mode. The data are consistent with recent computational modeling identifying E x B{sub T} circulation, due to potentials sustained by plasma gradients, as the main cause of divertor plasma sensitivity to B{sub T} direction.

  15. Convection in galaxy-cluster plasmas driven by active galactic nuclei and cosmic-ray buoyancy

    E-print Network

    Benjamin D. G. Chandran

    2004-12-20

    Turbulent heating may play an important role in galaxy-cluster plasmas, but if turbulent heating is to balance radiative cooling in a quasi-steady state, some mechanism must set the turbulent velocity to the required value. This paper explores one possible regulating mechanism associated with an active galactic nucleus at cluster center. A steady-state model for the intracluster medium is presented in which radiative cooling is balanced by a combination of turbulent heating and thermal conduction. The turbulence is generated by convection driven by the buoyancy of cosmic rays produced by a central radio source. The cosmic-ray luminosity is powered by the accretion of intracluster plasma onto a central black hole. The model makes the rather extreme assumption that the cosmic rays and thermal plasma are completely mixed. Although the intracluster medium is convectively unstable near cluster center in the model solutions, the specific entropy of the thermal plasma still increases outwards because of the cosmic-ray modification to the stability criterion. The model provides a self-consistent calculation of the turbulent velocity as a function of position, but fails to reproduce the steep central density profiles observed in clusters. The principal difficulty is that in order for the fully mixed intracluster medium to become convectively unstable, the cosmic-ray pressure must become comparable to or greater than the thermal pressure within the convective region. The large cosmic-ray pressure gradient then provides much of the support against gravity, reducing the thermal pressure gradient near cluster center and decreasing the central plasma density gradient. A more realistic AGN-feedback model of intracluster turbulence in which relativistic and thermal plasmas are only partially mixed may have greater success.

  16. Occurrence probability and amplitude of equatorial ionospheric irregularities associated with plasma bubbles during low and moderate solar activities (2008-2012)

    NASA Astrophysics Data System (ADS)

    Huang, Chao-Song; La Beaujardiere, O.; Roddy, P. A.; Hunton, D. E.; Liu, J. Y.; Chen, S. P.

    2014-02-01

    We present a statistical analysis of the occurrence probability of equatorial spread F irregularities measured by the Communication/Navigation Outage Forecasting System satellite during 2008-2012. We use different criteria (plasma density perturbations, ?N, and relative density perturbations, ?N/N0) to identify the occurrence of ionospheric irregularities. The purpose of this study is to determine whether the occurrence probability of irregularities is the same for different criteria, whether the patterns of irregularity occurrence vary with solar activity and with local time, and how the patterns of irregularity occurrence are correlated with ionospheric scintillation. It is found that the occurrence probability of irregularities and its variation with local time are significantly different when different identification criteria are used. The occurrence probability based on plasma density perturbations is high in the evening sector and becomes much lower after midnight. In contrast, the occurrence probability based on relative density perturbations is low in the evening sector but becomes very high after midnight in the June solstice. We have also compared the occurrence of ionospheric irregularities with scintillation. The occurrence pattern of the S4 index and its variation with local time are in good agreement with the irregularity occurrence based on plasma density perturbations but are significantly different from those based on relative density perturbations. This study reveals that the occurrence pattern of equatorial ionospheric irregularities varies with local time and that only the occurrence probability of irregularities based on plasma density perturbations is consistent with the occurrence of scintillation at all local times.

  17. A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far-ultraviolet spacecraft observations: initial results

    Microsoft Academic Search

    S. L. England; T. J. Immel; S. H. Park; H. U. Frey; S. B. Mende

    2007-01-01

    The Far-Ultraviolet Imager (IMAGE-FUV) on-board the NASA IMAGE satellite has been used to observe plasma depletions in the nightside equatorial ionosphere. Observations from periods around spacecraft apogee, during which equatorial regions are visible for several hours, have allowed the velocity of these plasma depletions to be determined. A new method for determining the velocity of these depletions using an image

  18. Pre-Storm Ionospheric Oxygen Ions between the Ionosphere and the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Yau, A. W.; Howarth, A.; Peterson, W. K.; Abe, T.

    2012-04-01

    The prompt appearance of energetic O+ ions in the ring current in the growth phase of a magnetic storm raises the interesting question of the possible role of O+ ions between the ionosphere and the plasma sheet and ring current immediately preceding the main phase of a magnetic storm. We examine oxygen ion transport from the high-altitude polar ionosphere in the quiet-time periods immediately preceding a series of five large magnetic storms (Dst < -100 nT) in Solar Cycle 23, using single-particle trajectory simulations in conjunction with Akebono ion measurements and related IMF and convection electric field data. Observed low-energy O+ ions on Akebono in the quiet-time high-altitude auroral and polar cap ionosphere (7000 km) are found to have temperatures of about 0.2-0.3 eV and flow velocities of a few km/s, and a portion of the ions undergo centrifugal acceleration at higher altitudes (above about 3 Earth radii (altitude)), resulting in a low but non-negligible O+ ion flux between the ionosphere and the plasma sheet and ring current that is dependent on IMF as well as Kp: up 30% of the observed low-energy O+ ions reach the plasma sheet, and more of the ions reach the dusk than dawn, corresponding to an O+ mass source rate of ~ 0.14 kg/s and a "plasma sheet filling time" of ~6.7 hr near solar maximum, assuming a plasma sheet oxygen density of 0.1 per cc.

  19. Magnetospheric Convection The large-scale flow of rarefied plasma in the Earth's magnetosphere "is quite analogous to

    E-print Network

    Michigan, University of

    Magnetospheric Convection The large-scale flow of rarefied plasma in the Earth's magnetosphere "is of geomagnetic field lines in the crossed E and B fields. By analogy with the thermal convection in a non-conductive fluid B/t = × (v × B), which means that the magnetic field is tied (frozen-in) to the corresponding

  20. HF ray propagation in the presence of resonance heated ionospheric plasmas

    Microsoft Academic Search

    E. Sonnenschein; N. Blaunstein; D. Censor

    1998-01-01

    The process of formation and further evolution of strong electron concentration inhomogeneities in the F-layer of the ionosphere created by the field of a powerful radio wave is investigated. Numerical simulations are employed to obtain the associated ray propagation trajectories which determine communication properties under such circumstances. The simulations involve the formulas obtained for the problem of one-dimensional non-stationary thermo-diffusion

  1. Statistics of 1-m wavelength plasma irregularities and convection in the auroral E region

    SciTech Connect

    Waldock, J.A.; Jones, T.B.; Nielsen, E.

    1985-08-01

    Data from the Sweden and Britain Radar Auroral Experiment have been utilized in a statistical study of auroral backscatter due to 1-m-scale plasma irregularities and of plasma convection in the auroral E layer. An examination of approximately 15,000 hours of backscatter amplitude data indicates that (1) the strongest backscatter is invariably associated with the main electrojets, between 1300-1900 UT and 2300-0300 UT, (2) only weak backscatter occurs in the vicinity of the convection reversals, particularly in the morning sector, and (3) the backscatter intensity can exhibit an aspect angle attenuation of between 0 and 10 dB/deg depending on the absolute intensity measured. Average convection patterns obtained from approximately 1400 hours of two-station measurements reveal a well-defined two-cell structure for all magnetic conditions. As magnetic activity increases the Harang discontinuity moves toward earlier local times, the flow speed increases and the morning convection cell expands relative to the evening cell. 32 references.

  2. Radiative divertor plasmas with convection in DIII-D

    NASA Astrophysics Data System (ADS)

    Leonard, A. W.; Porter, G. D.; Wood, R. D.; Allen, S. L.; Boedo, J.; Brooks, N. H.; Evans, T. E.; Fenstermacher, M. E.; Hill, D. N.; Isler, R. C.; Lasnier, C. J.; Lehmer, R. D.; Mahdavi, M. A.; Maingi, R.; Moyer, R. A.; Petrie, T. W.; Schaffer, M. J.; Wade, M. R.; Watkins, J. G.; West, W. P.; Whyte, D. G.

    1998-05-01

    The radiation of divertor heat flux on DIII-D [J. Luxon et al., in Proceedings of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1987), p. 159] is shown to greatly exceed the limits imposed by assumptions of energy transport dominated by electron thermal conduction parallel to the magnetic field. Approximately 90% of the power flowing into the divertor is dissipated through low-Z radiation and plasma recombination. The dissipation is made possible by an extended region of low electron temperature in the divertor. A one-dimensional analysis of the parallel heat flux finds that the electron temperature profile is incompatible with conduction-dominated parallel transport. Plasma flow at up to the ion acoustic speed, produced by upstream ionization, can account for the parallel heat flux. Modeling with the two-dimensional fluid code UEDGE [T. Rognlien, J. L. Milovich, M. E. Rensink, and G. D. Porter, J. Nucl. Mater. 196-198, 347 (1992)] has reproduced many of the observed experimental features.

  3. Topside ionosphere bubbles, seen as He+ density depletions: connection with ESF, vertical plasma drift, thermosphere wind and solar activity

    NASA Astrophysics Data System (ADS)

    Sidorova, Larissa

    He+ density depletions, considered as originating from equatorial plasma bubbles (PB), or as possible fossil bubble signatures, were involved in this study. He+ density depletions were observed during a high solar activity (1978-79, F10.7 200) at the topside ionosphere altitudes deeply inside the plasmasphere (L 1.3-3) (Karpachev and Sidorova, ASR, 2002; Sidorova, ASR, 2004, 2007). It is suggested that the equatorial F region irregularities, their post sunset development, evolution, and decay processes are controlled by the sunset electrodynamics of the equatorial region. The He+ density depletion peculiarities were considered in connection with equatorial F-spread (ESF) and vertical plasma drift. The depletion values as function of local time (evening-night hours) were compared with the vertical plasma drift velocity variations, obtained for the same periods (1978-79, F10.7 200; AE-E, IS radar, Jicamarca). Striking similarity in development dynamics was revealed for the different seasons. The monthly mean PB occurrence probability, plotted in local time versus month, was compared with the similar plots for global ESF occurrence probability, derived from ISS-b data (1978-79). Good seasonal correlation (R=0.6) was obtained. Moreover, the comparison of the regional maps, derived from ground-based ionograms, obtained over Brazilian regions (Abdu et al., ASR, 2000) for period with the similar solar activity (1980-81, F10.7 230), shows very well correlation (R=0.67). It is also suggested, that the PBs, produced by Rayleigh-Taylor (R-T) instability at the bottomside of ionosphere and transported up to the topside ionosphere/plasmasphere, could be strong affected by meridional wind during a generation due to inhibiting the growth of R-T instability and flux tube integrated conductivity. For better understanding competing/complementary roles of thermospheric winds in the development of PBs, seen as He+ density depletions, the evaluation of the possible influence of the thermosphere meridional winds was done. The diurnal PB statistics, averaged for the periods around the solstices and equinoxes, was compared with the model velocity variations of the meridional thermosphere wind. The wind model calculation was taken from (Maruyama, JGR, 1996). The best amplitude correlation was found for the longitudes of 270-360° (Brazilia, Atlantic regions), where declination angle is near 20?. It was obtained that the topside PBs, seen as He+ density depletions, are strong enough affected by meridional wind. The modulation effect has a seasonal dependence and the best correlation in equinox (R=0.87). He+ density depletion occurrence in dependence on solar activity was also under consideration. It was revealed that there are many cases of the He+ density depletions in solar maxima on the OGO-4 (1968, 20th cycle), OGO-6 (1969, 20th cycle) and DE-2 (1981, 21th cycle) data. It was concluded that the topside PBs, seen as He+ density depletions, are rather typical phenomena for the topside ionosphere for high solar activity epoch. The possible reasons of topside PB occurrence as function of solar activity are discussed.

  4. Planetary waves in rotating ionosphere

    SciTech Connect

    Khantadze, A. G.; Jandieri, V. G. [Tbilisi State University (Georgia); Jandieri, G. V. [Georgian Technical University (Georgia)

    2008-06-15

    The problem of propagation of ultralong planetary waves in the Earth's upper atmosphere is considered. A new exact solution to the MHD equations for the ionosphere is obtained in spherical coordinates with allowance for the geomagnetic field and Earth's rotation. A general dispersion relation is derived for planetary waves in the ionospheric E and F regions, and the characteristic features of their propagation in a weakly ionized ionospheric plasma are discussed.

  5. Plasma Density and Electro-Magnetic Field Perturbations Hf-Induced in the Outer Ionosphere: Review of Experimental Results

    NASA Astrophysics Data System (ADS)

    Frolov, Vladimir; Rauch, Jean-Louis; Parrot, Michel; Rapoport, Victor; Shorokhova, Elena

    In the report we consider features of plasma density and electro-magnetic field perturbations induced in the Earth’s outer ionosphere by modification of F _{2} region by O-mode powerful HF radio waves radiated by the SURA heating facility. Experiments presented were carried out in 2005 - 2010. Plasma density perturbations were detected at altitudes of about of 700 km by instruments onboard the French DEMETER satellite when it intersected the disturbed magnetic flux tube. The formation of artificial HF-induced plasma density ducts in the outer ionosphere is a central discovery, which was made during the SURA-DEMETER experiments [1,2]. Analysis of experimental data available makes it possible to formulate ducts features and point out the conditions under which the formation of such ducts takes place. 1. Under night conditions ducts are characterized by the increased plasma density in the range from 20% to 80% relatively to its background value. As this takes place, the excess in the plasma ion component is due to O (+) ions dominating at altitudes of about 700 km, whereas the densities of lower mass H (+) and He ({+) } ions typically decrease by a percentage amount that is much more the relative increase in the density of O (+) ions. The duct formation was never observed under daytime conditions. According to [3] the HF-induced ducts were observed by ionosphere pumping in morning and evening hours but in these cases their intensity was no more than a few percentages. 2. The size of the ducts along the satellite orbits is of about 80 - 100 km. It is a reason why such ducts can be observed only if the minimal distance between the satellite and the center of the heated flux tube is less than 50 km. 3. The formation of ducts is observed only if the effective radiated power is more than 40 MW. For the SURA facility, to heat the ionosphere at higher efficiency due to the “magnetic-zenith effect”, the HF beam is often inclined by 12 - 16(°) southward. 4. The pump wave frequency should be no less than 0.5 - 0.7 MHz below the F _{2} layer critical frequency f _{0F2}. In the opposed case the penetration of the radiated power behind the F _{2} ionospheric layer can take place [4]. 5. Strong variations of the electron temperature are observed inside the ducts, at the same time the ion temperature is unchanged. 6. A feature of the ducts is the presence of strong electro-magnetic field fluctuations in a frequency range from a few Hz to tens of kHz [1,5]. 7. It was revealed that the formation of the ducts in the outer ionosphere can stimulate the precipitation of energetic electrons with E ? 100 keV from the Earth’s radiation belts [6]. The work was supported by RFBR grants (## 12-05-00312, 13-02-12074, 13-02-12241) and by the scientific program “Geophysics”. References: 1. Rapoport V.O., V.L. Frolov, G.P. Komrakov, et al. // Radiophysics and Quantum Electronics, 2007. Vol. 50(8), p. 645. 2. Frolov V.L., V.O. Rapoport, G.P. Komrakov, et. al. // JETP Letters, 2008. Vol. 88, No. 12, p. 790. 3. Frolov V.L., I.A. Bolotin, V.O. Rapoport, et. al. // XXIV All-Russian conference “Radio Wave Propagation”. Irkutsk, 2014 (submitted for publication). 4. Frolov V.L., N.A. Mityakov, E.A. Shorokhova, M. Parrot. // Radiophysics and Quantum Electronics, 2013. Vol. 56(6), p. 325. 5. Rapoport V.O., V.L. Frolov, S.V. Polyakov, et al. // J. Geophys. Res., 2010. Vol. 115, A10322, doi:10.1029/2010JA015484. 6. Markov G.A., A.S. Belov, V.L. Frolov, et al. // JETPh, 2010. Vol. 138, No. 6(12), p. 1037.

  6. Last studies of artificial airglow emission of ionospheric plasma at the "Sura" facility

    NASA Astrophysics Data System (ADS)

    Nasyrov, Igor; Grach, Savely; Albert, Nasyrov; Rustam, Gumerov; Vladimir, Klimenko

    Experimental results of September 2007 on artificial airglow emission at 557.7 nm [green line, the radiation of atomic oxygen level O(1 S), the excitation threshold 4.17 eV, radiation lifetime 0.7 s)] and 630 nm [red line, the radiation of atomic oxygen level O(1 D), the excitation threshold 1.96.17 eV, radiation lifetime ˜ 100 s)] during HF pumping of the ionosphere with specially designed HF pulsing sequence are reported. Ionospheric radio pumping was performed at the "Sura" radio facility situated near Nizhny Novgorod, Russia. The airglow measurements were handled by the CCD camera S1C/079FP(FU) and the newly developed mobile photometric instrument (MFI) of Kazan university (Nasyrov et al., 2007). During several "Sura" runs enhancements of the 557.7 nm airglow intensity caused by 25 ms-long pulses of pump wave were with an interpulse period 3 s were observed after the pump wave switch from continuous pumping to low duty cycle pulse radiation. The enhancements achieve the maximum (˜ +5% above the background) at ˜ 0, 6 s after the pump pulse. Then a signal intensity decreases and achieves a minimum (˜ -7% below the background) at 1.6-1.7 s after the pump pulse. In ˜ 2-2.3 s ater the pulse the airglow intensity recovers to the background level. The work is supported by RFBR (Grant No 06-02-17334). Nasyrov, I.A., Gumerov, R.I., Nasyrov, A.M., Grach, S.M.: Mobile photometric instrument for studies of ionospheric airglow emission caused by anthropogenous disturbances. VII International Suzdal URSI Symposium (ISS-07), Abstracts, p.36, 2007.

  7. Plasma convection in the vicinity of the geosynchronous orbit.

    NASA Technical Reports Server (NTRS)

    Mcilwain, C. E.

    1972-01-01

    An analytic function respresenting the quiet time magnetospheric electric field has been constructed with which it is possible to compute complete particle trajectories in a fraction of a second. The function was determined by a trial-and-error procedure such that it provides reasonable explanations for the characteristics of the plasma observed by the geosynchronous satellite ATS 5. It is believed that the model field is usefully accurate within the region of 5 to 7 earth radii on the dawn side of the magnetosphere and 5 to 10 earth radii on the dusk side. At a fixed distance of 6.7 earth radii the model field peaks at a value of 1.2 mV/m near local midnight and is at a minimum of 0.04 mV/m near 1900 LT.

  8. Temperature structure of plasma bubbles in the low latitude ionosphere around 600 km altitude

    Microsoft Academic Search

    K.-I. Oyama; K. Schlegel; S. Watanabe

    1988-01-01

    The electron temperature inside plasma bubbles at a height of 600 km was first measured by means of Japan's seventh scientific satellite Hinotori which is an equator orbiting satellite with an inclination of 31 deg. During the period between June 1981 and February 1982, 724 plasma bubbles were detected and studied. The electron temperature inside the plasma bubbles is either

  9. Ionospheres of the terrestrial planets

    Microsoft Academic Search

    R. W. Schunk; A. F. Nagy

    1980-01-01

    The theory and observations relating to the ionospheres of the terrestrial planets Venus, the earth and Mars are reviewed. Emphasis is placed on comparing the basic differences and similarities between the planetary ionospheres. The review covers the plasma and electric-magnetic field environments that surround the planets, the theory leading to the creation and transport of ionization in the ionspheres, the

  10. CRRES and DMSP Observations of Wave and Plasma Disturbances Associated with the Stormtime Ring Current in the Plasmasphere and Topside Ionosphere

    Microsoft Academic Search

    E. V. Mishin; W. J. Burke

    2004-01-01

    We report on wave and plasma disturbances observed by Combined Release and Radiation Effects (CRRES) and Defense Meteorological Satellite Program (DMSP) satellites during the magnetic storm of June 5, 1991 in the region of ring current\\/plasmasphere overlap and the conjugate topside ionosphere During three ring current nose encounters near L = 2.4, the plasmasphere was highly-structured. A rich variety of

  11. Stimulated Electromagnetic Emission Indicator of Glow Plasma Discharges from Ionospheric HF Wave Transmissions with HAARP

    NASA Astrophysics Data System (ADS)

    Bernhardt, P. A.; Scales, W.; Briczinski, S. J.; Fu, H.; Mahmoudian, A.; Samimi, A.

    2012-12-01

    High power radio waves resonantly interact with to accelerate electrons for production of artificial aurora and plasma clouds. These plasma clouds are formed when the HF frequency is tuned near a harmonic of the electron cyclotron frequency. At a narrow band resonance, large electrostatic fields are produced below the F-layer and the neutral atmosphere breaks down with a glow plasma discharge. The conditions for this resonance are given by matching the pump wave frequency and wave-number with the sum of daughter frequencies and wave-numbers for several plasma modes. The most likely plasma mode that accelerates the electrons is the electron Bernstein wave in conjunction with an ion acoustic wave. Both upper hybrid and whistler mode waves are also possible sources of electron acceleration. To determine the plasma process for electron acceleration, stimulated electromagnetic emissions are measured using ground receivers in a north-south chain from the HAARP site. Recent observations have shown that broad band spectral lines downshifted from the HF pump frequency are observed when artificial plasma clouds are formed. For HF transmissions are the 2nd, 3rd, and 4th gyro harmonic, the downshifted indicators are found 500 Hz, 20 kHz, and 140 kHz, respectively, from the pump frequency. This Indicator Mode (IM) anticipates that a plasma layer will be formed before it is recorded with an ionosonde or optical imager.

  12. Ionospheric plasma resonances - Time durations vs latitude, altitude, and fn/fh.

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    1972-01-01

    The variation of resonant time duration with latitude, altitude, and fn/fh has been determined for the plasma resonances observed by Alouette I and Alouette II at the electron plasma frequency fn, the electron cyclotron frequency fh, the upper hybrid frequency ft, and the harmonics n-fh where n = 2,3

  13. Intermittent convective transport carried by propagating electromagnetic filamentary structures in nonuniformly magnetized plasma

    NASA Astrophysics Data System (ADS)

    Xu, G. S.; Naulin, V.; Fundamenski, W.; Rasmussen, J. Juul; Nielsen, A. H.; Wan, B. N.

    2010-02-01

    Drift-Alfvén vortex filaments associated with electromagnetic turbulence were recently identified in reversed field pinch devices. Similar propagating filamentary structures were observed in the Earth magnetosheath, magnetospheric cusp and Saturn's magnetosheath by spacecrafts. The characteristics of these structures closely resemble those of the so-called mesoscale coherent structures, prevailing in fusion plasmas, known as "blobs" and "edge localized mode filaments" in the boundary region, and propagating avalanchelike events in the core region. In this paper the fundamental dynamics of drift-Alfvén vortex filaments in a nonuniformly and strongly magnetized plasma are revisited. We systemize the Lagrangian-invariant-based method. Six Lagrangian invariants are employed to describe structure motion and the resultant convective transport, namely, magnetic flux, background magnetic energy, specific entropy, total energy, magnetic momentum, and angular momentum. The perpendicular vortex motions and the kinetic shear Alfvén waves are coupled through the parallel current and Ampere's law, leading to field line bending. On the timescale of interchange motion ??, a thermal expansion force in the direction of curvature radius of the magnetic field overcomes the resultant force of magnetic tension and push plasma filament to accelerate in the direction of curvature radius resulting from plasma inertial response, reacted to satisfy quasineutrality. During this process the internal energy stored in the background pressure gradient is converted into the kinetic energy of convective motion and the magnetic energy of field line bending through reversible pressure-volume work as a result of the plasma compressibility in an inhomogeneous magnetic field. On the timescale of parallel acoustic response ?????, part of the filament's energy is transferred into the kinetic energy of parallel flow. On the dissipation timescale ?d???, the kinetic energy and magnetic energy are eventually dissipated, which is accompanied by entropy production, and in this process the structure loses its coherence, but it has already traveled a distance in the radial direction. In this way the propagating filamentary structures induce intermittent convective transports of particles, heat, and momentum across the magnetic field. It is suggested that the phenomena of profile consistency, or resilience, and the underlying anomalous pinch effects of particles, heat, and momentum in the fusion plasmas can be interpreted in terms of the ballistic motion of these solitary electromagnetic filamentary structures.

  14. Intermittent convective transport carried by propagating electromagnetic filamentary structures in nonuniformly magnetized plasma

    SciTech Connect

    Xu, G. S. [Euratom-UKAEA, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Naulin, V.; Rasmussen, J. Juul; Nielsen, A. H. [Association Euratom-Risoe DTU, DK-4000 Roskilde (Denmark); Fundamenski, W. [Euratom-UKAEA, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Wan, B. N. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2010-02-15

    Drift-Alfven vortex filaments associated with electromagnetic turbulence were recently identified in reversed field pinch devices. Similar propagating filamentary structures were observed in the Earth magnetosheath, magnetospheric cusp and Saturn's magnetosheath by spacecrafts. The characteristics of these structures closely resemble those of the so-called mesoscale coherent structures, prevailing in fusion plasmas, known as 'blobs' and 'edge localized mode filaments' in the boundary region, and propagating avalanchelike events in the core region. In this paper the fundamental dynamics of drift-Alfven vortex filaments in a nonuniformly and strongly magnetized plasma are revisited. We systemize the Lagrangian-invariant-based method. Six Lagrangian invariants are employed to describe structure motion and the resultant convective transport, namely, magnetic flux, background magnetic energy, specific entropy, total energy, magnetic momentum, and angular momentum. The perpendicular vortex motions and the kinetic shear Alfven waves are coupled through the parallel current and Ampere's law, leading to field line bending. On the timescale of interchange motion tau{sub perpendicular}, a thermal expansion force in the direction of curvature radius of the magnetic field overcomes the resultant force of magnetic tension and push plasma filament to accelerate in the direction of curvature radius resulting from plasma inertial response, reacted to satisfy quasineutrality. During this process the internal energy stored in the background pressure gradient is converted into the kinetic energy of convective motion and the magnetic energy of field line bending through reversible pressure-volume work as a result of the plasma compressibility in an inhomogeneous magnetic field. On the timescale of parallel acoustic response tau{sub ||}>>tau{sub perpendicular}, part of the filament's energy is transferred into the kinetic energy of parallel flow. On the dissipation timescale tau{sub d}>>tau{sub perpendicular}, the kinetic energy and magnetic energy are eventually dissipated, which is accompanied by entropy production, and in this process the structure loses its coherence, but it has already traveled a distance in the radial direction. In this way the propagating filamentary structures induce intermittent convective transports of particles, heat, and momentum across the magnetic field. It is suggested that the phenomena of profile consistency, or resilience, and the underlying anomalous pinch effects of particles, heat, and momentum in the fusion plasmas can be interpreted in terms of the ballistic motion of these solitary electromagnetic filamentary structures.

  15. Magnetospheric signatures of ionospheric density cavities observed by Cluster

    NASA Astrophysics Data System (ADS)

    Russell, A. J. B.; Karlsson, T.; Wright, A. N.

    2015-03-01

    We present Cluster measurements of large amplitude electric fields correlated with intense downward field-aligned currents, observed during a nightside crossing of the auroral zone. The data are reproduced by a simple model of magnetosphere-ionosphere coupling which, under different conditions, can also produce a divergent electric field signature in the downward current region, or correlation between the electric and perturbed magnetic fields. We conclude that strong electric field associated with intense downward field-aligned current, such as this observation, is a signature of ionospheric plasma depletion caused by the downward current. It is also shown that the electric field in the downward current region correlates with downward current density if a background field is present, e.g., due to magnetospheric convection.

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

    SciTech Connect

    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.

  17. Comment on 'Mapping the dayside ionosphere to the magnetosphere according to particle precipitation characteristics' by Newell and Meng

    NASA Technical Reports Server (NTRS)

    Lockwood, M.; Smith, M. F.

    1993-01-01

    Newell and Meng (1992) present maps of the occurrence probability of various classifications of particle precipitation as seen in the dayside topside ionosphere. It is argued that these are maps of the magnetospheric regions, a contention with which their critics disagree. The latter conclude that, because of convection, any one population of particles seen at low altitudes will have originated from a wide variety of locations, and particle characteristics cannot be mapped back to those in the magnetosphere without detailed knowledge of both the convection and magnetic field. Steplike boundaries between the regions will arise from nonsteady-state conditions and cannot be envisaged as steady-state magnetospheric boundaries between two plasma populations. In their reply Newell and Meng contend that convection does not move plasma from the LLBL into the cusp. Most of the LLBL plasma comes from the magnetosheath, so the direction of plasma transfer is in the other direction.

  18. Plasma flow reversals at the dayside magnetopause and the origin of asymmetric polar cap convection

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Thomsen, M. F.; Bame, S. J.; Elphic, R. C.; Russell, C. T.

    1990-01-01

    Events observed in a fast plasma experiment, where the y-component of the plasma flow within the low latitude boundary layer and magnetopause current layer was oppositely directed to that in the adjacent magnetosheath, are examined. The observations are shown to be qualitatively and quantitatively consistent with previous observations of accelerated flows at the magnetopause and with models of magnetic reconnection, with reconnection occurring at low latitudes near the GSE XY plane, independently of the magnitude or the sign of the y-component ot the local magnetosheath magnetic field. Local magnetic shears at the magnetopause for these events (in 60-180 deg range) and the fact that these events occur at low latitudes do not support the antiparallel merging hypothesis. The observations of B(y)-dependent flow reversals demonstrate how the asymmetric polar cap convection and related phenomena, such as the Svalgaard-Mansurov effect, originate in magnetic reconnection at the dayside magnetopause.

  19. Solar zenith angle dependence of the plasma density and temperatures in the polar ionosphere and magnetosphere during geomagnetically quiet periods at solar maximum

    NASA Astrophysics Data System (ADS)

    Kitamura, Naritoshi; Terada, Naoki; Ogawa, Yasunobu; Nishimura, Yukitoshi; Ono, Takayuki; Shinbori, Atsuki; Kumamoto, Atsushi

    The electron density in the polar region is one of the most important parameters in under-standing the acceleration mechanisms of outflowing ions and plasma supply from the ionosphere toward the magnetosphere. However, the lack of observations above the polar ionosphere, es-pecially in an altitude range of 1000-4000 km, has made it difficult to clarify how strongly the solar radiation influences the electron density in the polar magnetosphere and ion accel-eration between the polar ionosphere and magnetosphere. In order to quantitatively evaluate the contribution of solar radiation to the electron density in the polar topside ionosphere and magnetosphere, we have investigated the solar zenith angle (SZA) dependence of the electron density profile in the polar cap during geomagnetically quiet periods. The electron density data used in the present study are obtained from 63 months of plasma wave observations by the Akebono satellite in an altitude range of 500-10,500 km, where observations have been limited, at solar maximum (monthly-averaged F10.7 larger than 170). Electron density profiles at low altitudes are well fitted by quasi-hydrostatic equilibrium functions, while those at higher altitudes are well described by power law functions. In the quasi-hydrostatic equilibrium func-tions, we used a constant temperature, and altitude dependence of the gravitational force and magnetic field strength are taken into account. A clear transition of the density profile is identified at about 2000 km altitude above an SZA of about 110 degrees. The largest variation in the fitted electron density with SZA is identified at 2100 km altitude, where the electron density varies by a factor of 88 from 1.25*104 cm-3 at an SZA of 50 degrees to 1.43*102 cm-3 at an SZA of 130 degrees in the polar cap. Above 5800 km altitude, the variation in the fitted electron density is limited within a factor of 20. The electron density and scale height decrease drastically with increasing SZA in an SZA range of 90-120 degrees. The sum of the ion and electron temperatures estimated from the scale height at an SZA of 120 degrees (3600 K) is less than half of that at an SZA of 90 degrees (8200 K). Furthermore, in order to compare the change in the ionospheric plasma temperature with that obtained by the Akebono satellite, we have investigated the SZA dependence of the electron and ion temperatures in the topside ionosphere using 19 months of data derived from EISCAT Svalbard Radar (ESR), located at an invariant latitude of 75.2 degrees, in an altitude range of 300-1100 km during geomagnetically quiet periods at solar maximum. The electron (ion) temperature above about 300 (600) km altitude decreases most drastically with increasing SZA in an SZA range of 80-110 degrees, which is near the terminator in the ionosphere. Although the SZA range of the drastic temperature change was about 10 degrees lower than that derived by the Akebono data, the drastic decrease in the ionospheric temperatures strongly suggests the dominant role of heating and photo-ionization processes by solar radiation in determining the electron density up to about 2000 km in the polar cap during geomagnetically quiet peri-ods, while the ionospheric control of the electron density gradually diminishes with increasing altitude above about 2000 km altitude.

  20. Global Ionosphere Radio Observatory

    NASA Astrophysics Data System (ADS)

    Galkin, I. A.; Reinisch, B. W.; Huang, X. A.

    2014-12-01

    The Global Ionosphere Radio Observatory (GIRO) comprises a network of ground-based high-frequency vertical sounding sensors, ionosondes, with instrument installations in 27 countries and a central Lowell GIRO Data Center (LGDC) for data acquisition and assimilation, including 46 real-time data streams as of August 2014. The LGDC implemented a suite of technologies for post-processing, modeling, analysis, and dissemination of the acquired and derived data products, including: (1) IRI-based Real-time Assimilative Model, "IRTAM", that builds and publishes every 15-minutes an updated "global weather" map of the peak density and height in the ionosphere, as well as a map of deviations from the classic IRI climate; (2) Global Assimilative Model of Bottomside Ionosphere Timelines (GAMBIT) Database and Explorer holding 15 years worth of IRTAM computed maps at 15 minute cadence;. (3) 17+ million ionograms and matching ionogram-derived records of URSI-standard ionospheric characteristics and vertical profiles of electron density; (4) 10+ million records of the Doppler Skymaps showing spatial distributions over the GIRO locations and plasma drifts; (5) Data and software for Traveling Ionospheric Disturbance (TID) diagnostics; and (6) HR2006 ray tracing software mated to the "realistic" IRTAM ionosphere. In cooperation with the URSI Ionosonde Network Advisory Group (INAG), the LGDC promotes cooperative agreements with the ionosonde observatories of the world to accept and process real-time data of HF radio monitoring of the ionosphere, and to promote a variety of investigations that benefit from the global-scale, prompt, detailed, and accurate descriptions of the ionospheric variability.

  1. A simple axisymmetric model of magnetosphere-ionosphere coupling currents in Jupiter's polar ionosphere

    Microsoft Academic Search

    S. W. H. Cowley; I. I. Alexeev; E. S. Belenkaya; E. J. Bunce; C. E. Cottis; V. V. Kalegaev; J. D. Nichols; R. Prangé; F. J. Wilson

    2005-01-01

    We propose a simple illustrative axisymmetric model of the plasma flow and currents in Jupiter's polar ionosphere which are due both to internal magnetospheric plasma processes and the solar wind interaction. The plasma flow in the model is specified using a combination of observations, previous modeling, and theory, and the ionospheric and field-aligned currents are then calculated. With increasing latitude,

  2. Numerical simulation of plasma transport in Saturn's inner magnetosphere using the Rice Convection Model

    NASA Astrophysics Data System (ADS)

    Liu, X.; Hill, T. W.; Wolf, R. A.; Sazykin, S.; Spiro, R. W.; Wu, H.

    2010-12-01

    We use the Rice Convection Model to simulate plasma transport in Saturn's inner magnetosphere, 2 < L < 12, where L = equatorial distance in planetary radii. By incorporating a continuously active distributed plasma source derived from neutral cloud modeling, the simulation shows alternating longitudinal sectors ("fingers") of inflow and outflow. Their initial development confirms the retarding effects of the Coriolis force and the pickup current. In their further nonlinear development, the inflow fingers become much narrower in longitude than the outflow ones, which may explain a previously unexplained feature of the Cassini Plasma Spectrometer (CAPS) observations. Our analysis confirms that the narrower inflowing fingers have much larger radial speeds than the broader outflowing sectors. We analyze the corotation lag and find that in the innermost region (L < 5) the pickup current is the major driver of the corotation lag, but in the more distant region (L > 5) both the pickup current and the Coriolis acceleration contribute significantly to the corotation lag. We compare our simulation results with observational results from CAPS data. For the radial flow component, the simulation results fit observations reasonably well. In the azimuthal component, there are significant differences in the magnitude and radial structure of the corotation lag, which may provide guidance for future refinement of the plasma source model.

  3. Plasma-density modification by means of pulsed-beam CIV in the ionosphere

    Microsoft Academic Search

    S. T. Lai; W. J. McNeil; E. Murad

    1991-01-01

    Alfvens critical ionization velocity (CIV) discharge gives rise to rapid increase in electron density. The existence of CIV has been proven in the laboratory. If CIV occurs in space, there would be important consequences. Not only would electromagnetic wave propagation be affected by the enhanced plasma density, but there would also be important implications in spacecraft contamination. In attempts to

  4. Plasma density modifications by means of pulsed beam CIV in the ionosphere

    Microsoft Academic Search

    Shu T. Lai; William J. McNeil; Edmond Murad

    1990-01-01

    Alven's critical ionization velocity (CIV) discharge gives rise to rapid increase in electron density. The existence of CIV has been proven in the laboratory. If CIV occurs in space, there would be important consequences. Not only would electromagnetic wave propagation be affected by the enhanced plasma density, but there would also be important implications in spacecraft contamination. In attempts to

  5. Generalized fluid model of plasma outflow processes in the topside ionosphere

    Microsoft Academic Search

    Supriya B. Ganguli; Peter J. Palmadesso

    1988-01-01

    A generalized fluid model with anomalous transport coefficients, described by Ganguli and Palmadesso (1987) is used to investigate the classical and anomalous transport properties of a multifluid plasma in the presence of auroral field aligned return currents. The model includes the macroscopic effects of the electrostatic ion cyclotron (EIC) instability (perpendicular ion heating) and of an EIC-related anomalous resistivity mechanism

  6. Radar interferometry: A new technique for studying plasma turbulence in the ionosphere

    Microsoft Academic Search

    D.T. Farley; H.M. Ierkic; B.G. Fejer

    1981-01-01

    A new radar interferometer technique has been developed and used successfully at the Jicamarca Radio Observatory in Peru to study the strong nighttime plasma turbulence in the equatorial electrojet. The technique represents a major step forward in radar probing of turbulent irregularities such as (but not limited to) those in the electrojet. In many situations it provides far more information

  7. Global aspects of solar wind ionosphere interactions

    Microsoft Academic Search

    T. E. Moore; M.-C. Fok; D. C. Delcourt; S. P. Slinker; J. A. Fedder

    2007-01-01

    Recent observations have quantified the auroral wind O+ outflow in response to magnetospheric inputs to the ionosphere, notably Poynting energy flux and precipitating electron density. For moderate to high activity periods, ionospheric O+ is observed to become a significant or dominant component of plasma pressure in the inner plasma sheet and ring current regions. Using a global circulation model of

  8. Ionospheric variations at the time of the M8.8 Chile earthquake and statistical analysis of plasma parameters recorded by DEMETER

    NASA Astrophysics Data System (ADS)

    Parrot, M.

    2010-12-01

    DEMETER is a low orbiting satellite (650 km) which is operating more than six years to study ionospheric perturbations in relation with the seismic activity. It records wave and plasma parameters all around the Earth (except in the auroral zones) at two different local times (10.30 and 22.30 LT). This paper will present observations performed during the M8.8 Chile earthquake on February 27, 2010. They show a perturbation of the ionospheric density at the satellite altitude a few days before the quake. Publication of these results was not accepted in GRL despite the uniqueness of this observation. To reject the paper, an anonymous referee said that many other parameters can fluctuate before the quake including the stock market. It is true, but our parameter is not the London or the New York stock market; it is a physical parameter which is measured in close proximity to the earthquake. It is a parameter which characterizes the environment above the future epicentre. The physical mechanism which induces these perturbations is not yet known (there are several hypotheses) but it is know that it exists a fair weather electric field between the bottom of the ionosphere and the ground. Whatever is the mechanism, if there is a change on the ground it will be registered in the ionosphere. But it is also known that the ionosphere is highly variable and that perturbations could come from other sources (solar activity, AGW, TID, plasma dynamics, large meteorological phenomena…). Then the paper will show a new statistical analysis performed on the plasma parameters during night time. An algorithm has been implemented to detect crests and troughs in the data before earthquakes. The earthquakes have been classified depending on their magnitude, depth, and location (land, below the sea, close to a coast). Due to the orbit, DEMETER returns above the same area every day (once during day time, once during night time) but not at the same distance of a given epicentre. Then, for each earthquake, data have been checked until 15 days before the shock when the distance between the trace of the orbit and the epicentre is less than 1500 km. The results of the statistical analysis are presented as function of various parameters. A comparison is done with two other data bases where, on one hand, the location of the epicentres has been randomly modified, and on the other hand, the longitude of the epicentres has been shifted.

  9. Radar soundings of the ionosphere of Mars.

    PubMed

    Gurnett, D A; Kirchner, D L; Huff, R L; Morgan, D D; Persoon, A M; Averkamp, T F; Duru, F; Nielsen, E; Safaeinili, A; Plaut, J J; Picardi, G

    2005-12-23

    We report the first radar soundings of the ionosphere of Mars with the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on board the orbiting Mars Express spacecraft. Several types of ionospheric echoes are observed, ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes. The oblique echoes are believed to arise mainly from ionospheric structures associated with the complex crustal magnetic fields of Mars. Echoes at the electron plasma frequency and the cyclotron period also provide measurements of the local electron density and magnetic field strength. PMID:16319123

  10. Mesospheric gravity waves and ionospheric plasma bubbles observed during the COPEX campaign

    NASA Astrophysics Data System (ADS)

    Paulino, I.; Takahashi, H.; Medeiros, A. F.; Wrasse, C. M.; Buriti, R. A.; Sobral, J. H. A.; Gobbi, D.

    2011-07-01

    During the Conjugate Point Experiment (COPEX) campaign performed at Boa Vista (2.80?N;60.70?W, dip angle21.7?N) from October to December 2002, 15 medium-scale gravity waves in the OHNIR airglow images were observed. Using a Keogram image analysis, we estimate their parameters. Most of the waves propagate to Northwest, indicating that their main sources are Southeast of Boa Vista. Quasi-simultaneous plasma bubble activities in the OI 630 nm images were observed in seven cases. The distances between the bubble depletions have a linear relationship with the wavelengths of the gravity waves observed in the mesosphere, which suggests a direct contribution of the mesospheric medium-scale gravity waves in seeding the equatorial plasma bubbles.

  11. A case study of plasma structure in the dusk sector associated with enhanced magnetospheric convection

    NASA Technical Reports Server (NTRS)

    Carpenter, D. L.; Smith, A. J.; Giles, B. L.; Chappell, C. R.; Decreau, P. M. E.

    1992-01-01

    Consideration is given to a case study based on a combination of ground whistler and satellite measurements of thermal plasma density which provides additional evidence that the abrupt western edge of the bulge region of the magnetosphere, reported earlier from whistlers, is a real phenomenon. The present data and previous MHD modeling work suggest that this distinctive feature develops during periods of steady or declining substorm activity, when dense plasma previously carried sunward under the influence of enhanced convection activity begins to rotate with the earth at angular velocities that decrease with increasing L value and becomes spirallike in form. Whistler data are used to identify a narrow dense plasma feature, separated from the main plasmasphere and extending sunward into the late afternoon sector at L values near the outer observed limits of the main plasmasphere and extending sunward into the edge of the main bulge, found by both whistler stations to be at about 1800 MLT, appeared to be quasi-stationary in sun-earth coordinates during the prevailing conditions of gradually declining geomagnetic agitation.

  12. Coordinated ESR-Reimei observations of the cusp ionosphere

    NASA Astrophysics Data System (ADS)

    Pitout, F.; Ogawa, Y.; Ebihara, Y.; Asamura, K.; Hirahara, M.; Seki, K.

    2010-12-01

    The polar cusp, being the region where the magnetosheath plasma has a direct access to the magnetosphere and the polar ionosphere, is an interesting region to study, not only to understand how the coupling between the solar wind and the magnetosphere works, but also because at its footprint, interesting ionospheric phenomena occur: complex local electrodynamics, particle heating and outflow, etc. To study those phenomena, we have selected a few Reimei satellite overflights of the EISCAT Svalbard Radar (ESR) in the cusp region. These conjunctions allow us to directly compare precipitating magnetosheath particles and their effects on the dayside polar ionosphere. We present preliminary results of two of those conjunctions. The first case is characterized by an unusually strong zonal convection speed measured by the ESR at 08:25 UT on September 28, 2007. This strong plasma flow is believed to increase the ion temperature through frictional heating with the neutrals and drive ion outflow. However, we do not allays see very high ion temperature in our case, suggesting that Joule heating is not the unique source of ion outflow. In the second case around 08:11 UT on October 18, 2007, the conjunction occurs when the ESR is at the equatorward boundary of the cusp. Yet, the soft-electron precipitation is rather weak and as well as the electron temperature measured by the ESR. An interesting feature is that the particle sensor onboard Reimei observes a discontinuous cusp that we explain by the changes in the IMF orientation (given by Themis).

  13. Theory Issues for Induced Plasma Convection Experiments in the Divertor of the MAST Spherical Tokamak

    SciTech Connect

    Cohen, R H; Fielding, S; Helander, P; Ryutov, D D

    2001-09-05

    This paper surveys theory issues associated with inducing convective cells through divertor tile biasing in a tokamak to broaden the scrape-off layer (SOL). The theory is applied to the Mega-Ampere Spherical Tokamak (MAST), where such experiments are planned in the near future. Criteria are presented for achieving strong broadening and for exciting shear-flow turbulence in the SOL; these criteria are shown to be attainable in practice. It is also shown that the magnetic shear present in the vicinity of the X-point is likely to confine the potential perturbations to the divertor region below the X-point, leaving the part of the SOL that is in direct contact with the core plasma intact. The current created by the biasing and the associated heating power are found to be modest.

  14. A modelling study of the latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum

    NASA Astrophysics Data System (ADS)

    Bailey, G. J.; Denton, M. H.; Heelis, R. A.; Venkatraman, S.

    2000-11-01

    Latitudinal variations in the nighttime plasma temperatures of the equatorial topside ionosphere during northern winter at solar maximum have been examined by using values modelled by SUPIM (Sheffield University Plasmasphere Ionosphere Model) and observations made by the DMSP F10 satellite at 21.00 LT near 800 km altitude. The modelled values confirm that the crests observed near 15° latitude in the winter hemisphere are due to adiabatic heating and the troughs observed near the magnetic equator are due to adiabatic cooling as plasma is transported along the magnetic field lines from the summer hemisphere to the winter hemisphere. The modelled values also confirm that the interhemispheric plasma transport needed to produce the required adiabatic heating/cooling can be induced by F-region neutral winds. It is shown that the longitudinal variations in the observed troughs and crests arise mainly from the longitudinal variations in the magnetic meridional wind. At longitudes where the magnetic declination angle is positive the eastward geographic zonal wind combines with the northward (summer hemisphere to winter hemisphere) geographic meridional wind to enhance the northward magnetic meridional wind. This leads to deeper troughs and enhanced crests. At longitudes where the magnetic declination angle is negative the eastward geographic zonal wind opposes the northward geographic meridional wind and the trough depth and crest values are reduced. The characteristic features of the troughs and crests depend, in a complicated manner, on the field-aligned flow of plasma, thermal conduction, and inter-gas heat transfer. At the latitudes of the troughs/crests, the low/high plasma temperatures lead to increased/decreased plasma concentrations.

  15. Comparison of topside electron density computed by ionospheric models and plasma density observed by DMSP satellites

    NASA Astrophysics Data System (ADS)

    Migoya-Orue, Y. O.; Radicella, S. M.; Nava, B.

    2013-11-01

    Electron density obtained by IRI (topside options NeQuick and IRI-Corr) and NeQuick models in their standard versions have been compared with plasma density values measured by F13 and F15 DMSP satellites for years of different solar activities. A statistical study of the differences between modeled and experimental data has been carried out to investigate each model performance.In general, the models present a similar behavior. Nevertheless it has been found that the IRI-Corr topside option of IRI overestimates electron density at high latitudes and this trend increases with the solar activity.A few examples of representative half-orbit passes are given to illustrate the differences found.

  16. Sounding rockets explore the ionosphere

    SciTech Connect

    Mendillo, M. (Boston Univ., MA (USA))

    1990-08-01

    It is suggested that small, expendable, solid-fuel rockets used to explore ionospheric plasma can offer insight into all the processes and complexities common to space plasma. NASA's sounding rocket program for ionospheric research focuses on the flight of instruments to measure parameters governing the natural state of the ionosphere. Parameters include input functions, such as photons, particles, and composition of the neutral atmosphere; resultant structures, such as electron and ion densities, temperatures and drifts; and emerging signals such as photons and electric and magnetic fields. Systematic study of the aurora is also conducted by these rockets, allowing sampling at relatively high spatial and temporal rates as well as investigation of parameters, such as energetic particle fluxes, not accessible to ground based systems. Recent active experiments in the ionosphere are discussed, and future sounding rocket missions are cited.

  17. Waves generated in the vicinity of an argon plasma gun in the ionosphere

    NASA Technical Reports Server (NTRS)

    Cahill, L. J., Jr.; Arnoldy, R. L.; Lysak, R. L.; Peria, W.; Lynch, K. A.

    1993-01-01

    Wave and particle observations were made in the close vicinity of an argon plasma gun carned to over 600 km altitude on a sounding rocket. The gun was carned on a subpayload, separated from the main payload early in the flight. Twelve-second argon ion ejections were energized alternately with a peak energy of 100 or 200 eV. They produced waves, with multiple harmonics, in the range of ion cyclotron waves, 10 to 1000 Hz at rocket altitudes. Many of these waves could not be identified as corresponding to the cyclotron frequencies of any of the ions, argon or ambient, known to be present. In addition, the wave frequencies were observed to rise and fall and to change abruptly during a 12-s gun operation. The wave amplitudes, near a few hundred Hertz, were of the order of O. 1 V/m. Some of the waves may be ion-ion hybrid waves. Changes in ion populations were observed at the main payload and at the subpayload during gun operations. A gun-related, field-aligned, electron population also appeared.

  18. Ionospheric Potential Variation from Temperature Change over the Continents

    Microsoft Academic Search

    Ralph Markson

    ABSTRACT Since global thunderstorm activity and electrified deep convective shower clouds maintain the current flow in the global circuit and ionospheric potential (Vi), and convection is driven by temperature differences, the variation of Vi should be a measure of the variation of global temperature, or at least global temperature at tropical and equatorial latitudes where most deep convection occurs. An

  19. RCM-E simulation of bimodal transport in the plasma sheet

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Wolf, Richard A.; Toffoletto, Frank R.; Sazykin, Stanislav; Wang, Chih-Ping

    2014-03-01

    Plasma sheet transport is bimodal, consisting of both large-scale adiabatic convection and intermittent bursty flows in both earthward and tailward directions. We present two comparison simulations with the Rice Convection Model—Equilibrium (RCM-E) to investigate how those high-speed flows affect the average configuration of the magnetosphere and its coupling to the ionosphere. One simulation represents pure large-scale slow-flow convection with time-independent boundary conditions; in addition to the background convection, the other simulation randomly imposes bubbles and blobs through the tailward boundary to a degree consistent with observed statistical properties of flows. Our results show that the bursty flows can significantly alter the magnetic and entropy profiles in the plasma sheet as well as the field-aligned current distributions in the ionosphere, bringing them into much better agreement with average observations.

  20. CRRES and DMSP Observations of Wave and Plasma Disturbances Associated with the Stormtime Ring Current in the Plasmasphere and Topside Ionosphere

    NASA Astrophysics Data System (ADS)

    Mishin, E. V.; Burke, W. J.

    2004-12-01

    We report on wave and plasma disturbances observed by Combined Release and Radiation Effects (CRRES) and Defense Meteorological Satellite Program (DMSP) satellites during the magnetic storm of June 5, 1991 in the region of ring current/plasmasphere overlap and the conjugate topside ionosphere During three ring current nose encounters near L = 2.4, the plasmasphere was highly-structured. A rich variety of wave phenomena were observed simultaneous with enhanced fluxes of low-energy (< ˜ 1 keV) electrons and ions, indicating the wave heating/acceleration source. Earthward of the plasma sheet boundary, which was near L = 5.5, wave-like structures in the dawn-to-dusk electric field with spatial wave-lengths from about 300 to 1000 km and magnitudes of ~1-3 mV/m were apparent. Mapped to ionospheric altitudes, these fields should produce broad irregular SAPS with average sunward velocities ~ 1 km/s. At about the same time DMSP F8, F9, and F10 indeed observed highly-structured SAPS in the topside ionosphere coincident with precipitating ring current ions, enhanced fluxes of suprathermal electrons and ions, elevated electron temperatures, and deep highly-irregular density troughs. Overall, these events represent the so-called strong wave-SAPS phenomenon [Mishin et al., JGR (2003), 108, 1309, 10.1029/2002JA009793]. Their importance for Space Weather is indicated by strong GPS phase and amplitude scintillations observed over the continental US [Basu et al., JGR, 106, 30389, 2001; Ledvina et al., GRL, 29, 10.1029/2002GL014770] coincident with similar events.

  1. Thermospheric Wind Impacts on Ionospheric Upflow and Outflow

    NASA Astrophysics Data System (ADS)

    Burleigh, M.; Zettergren, M. D.

    2014-12-01

    Significant amounts of thermal ionospheric plasma can be transported to high altitudes in response to magnetospheric and atmospheric forcing. Soft electron precipitation serves as a heat source for the ambient F-region ionospheric electrons, which enhances the ambipolar electric field and induces upflowing ions. Frictional heating of ions from fast convection through the neutral atmosphere creates pressure-driven ion upflows. Finally, large neutral winds along the geomagnetic field may effectively lift or lower the F-region density peak. At regions above where ion upflows are typically initiated, transverse ion acceleration is thought to give upflowing ions sufficient energy to escape to the magnetosphere. This study examines how low-altitude upflow processes affect ion outflow, focusing particularly on the impacts of neutral winds. A new multi-fluid ionospheric model, which solves conservation equations for mass, momentum, and parallel and perpendicular energy is developed for this study. These fluid equations are solved for all species relevant to the E, F, and topside ionospheric regions and the system is closed through an electrostatic treatment of the auroral currents. This model is driven by the specification of field-aligned currents and a resonant transverse heating term. The model therefore encapsulates the basic ionospheric upflow processes and provides a simple way to approximate the effects of transverse heating and ion outflow. Using this model, individual species responses to electron precipitation, frictional heating, neutral winds, and transverse heating are examined to determine the effects of these low-altitude upflow processes on ion outflow. Results suggest that upflows, including those induced by neutral winds, can have a significant impact on the types and amounts of outflowing ions.

  2. A method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far-ultraviolet spacecraft observations: initial results

    NASA Astrophysics Data System (ADS)

    England, S. L.; Immel, T. J.; Park, S. H.; Frey, H. U.; Mende, S. B.

    2007-12-01

    The Far-Ultraviolet Imager (IMAGE-FUV) on-board the NASA IMAGE satellite has been used to observe plasma depletions in the nightside equatorial ionosphere. Observations from periods around spacecraft apogee, during which equatorial regions are visible for several hours, have allowed the velocity of these plasma depletions to be determined. A new method for determining the velocity of these depletions using an image analysis technique, Tracking Of Airglow Depletions (TOAD), has been developed. TOAD allows the objective identification and tracking of depletions. The automation of this process has also allowed for the tracking of a greater number of depletions than previously achieved without requiring any human input, which shows that TOAD is suitable for use with large data sets and for future routine monitoring of the ionosphere from space. Furthermore, this allows the drift velocities of each depletion to be determined as a function of magnetic latitude as well as local time. Previous ground-based airglow observations from a small number of locations have indicated that the drift velocities of depletions may vary rapidly with magnetic latitude. Here we shall present the first results from TOAD of this shear in drift velocities from our global sample of depletion drift velocities.

  3. Solar zenith angle dependence of the plasma density and temperature in the polar ionosphere and magnetosphere during geomagnetically quiet periods at solar maximum

    NASA Astrophysics Data System (ADS)

    Kitamura, N.; Terada, N.; Ogawa, Y.; Ono, T.; Nishimura, Y.; Shinbori, A.; Kumamoto, A.

    2010-12-01

    Plasma density and temperature in the polar region are important parameters for acceleration of outflowing thermal energy ions (the so-called polar wind). In order to quantitatively evaluate the contribution of solar radiation to the electron density in the polar topside ionosphere and magnetosphere, we have investigated the solar zenith angle (SZA) dependence of the electron density profile in the polar cap during geomagnetically quiet periods. The electron density data used in the present study were obtained from 63 months of plasma wave observations by the Akebono satellite in an altitude range of 500-10,500 km at solar maximum (monthly-averaged F10.7 larger than 170). Electron density profiles at low altitudes were found to be well fitted by quasi-hydrostatic equilibrium functions, while those at higher altitudes were well described by power law functions. In the quasi-hydrostatic equilibrium functions, we used a constant temperature, and altitude dependence of the gravitational force and magnetic field strength were taken into account. A clear transition of the density profile is identified at about 2000 km altitude above an SZA of about 110 degrees. The largest variation in the fitted electron density with SZA is identified at 2100 km altitude, where the electron density varies by a factor of 88 from 1.25 × 10^4 cm^-3 at an SZA of 50 degrees to 1.43 × 10^2 cm^-3 at an SZA of 130 degrees in the polar cap. Above 5800 km altitude, the variation in the fitted electron density is limited within a factor of 20. The electron density and scale height decrease drastically with increasing SZA in an SZA range of 90-120 degrees. The sum of the ion and electron temperatures estimated from the scale height at an SZA of 120 degrees (3600 K) is less than half of that at an SZA of 90 degrees (8200 K). Furthermore, in order to compare the change in the ionospheric plasma temperature with that obtained by the Akebono satellite, we have investigated the SZA dependence of the electron and ion temperatures in the topside ionosphere using 19 months of data derived from EISCAT Svalbard Radar (ESR), located at an invariant latitude of 75.2 degrees, in an altitude range of 300-1100 km during geomagnetically quiet periods at solar maximum. The electron (ion) temperature above about 300 (600) km altitude decreases most drastically with increasing SZA in an SZA range of 80-110 degrees, which is near the terminator in the ionosphere. The drastic decrease in the ionospheric temperatures strongly suggests the dominant role of heating and photo-ionization processes by solar radiation in determining the electron density up to about 2000 km in the polar cap during geomagnetically quiet periods, while the ionospheric control of the electron density diminishes gradually with increasing altitude above about 2000 km altitude.

  4. Ionospheric research

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Data from research on ionospheric D, E, and F, regions are reported. Wave propagation, mass spectrometer measurements, and atmospheric reactions of HO2 with NO and NO2 and NH2 with NO and O2 are summarized.

  5. Ionosphere research

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A report is presented on on-going research projects in ionospheric studies. The topics discussed are planetary atmospheres, E and F region, D region, mass spectrometer measurements, direct measurements and atmospheric reactions.

  6. Statistical patterns of high-latitude convection obtained from Goose Bay HF radar observations

    Microsoft Academic Search

    J. M. Ruohoniemi; R. A. Greenwald

    1996-01-01

    We have derived patterns that describe the statistical interplanetary magnetic field (IMF) dependencies of ionospheric convection in the high-latitude region of the northern hemisphere. The observations of plasma motion were made with the HF coherent backscatter radar located at Goose Bay, Labrador, over the period September 1987 to June 1993. The area covered by the measurements extended poleward of 65øA

  7. Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere

    SciTech Connect

    Liu Yu; Cao Jinxiang; Wang Jian; Zheng Zhe; Xu Liang; Du Yinchang [CAS Key Laboratory of Basic Plasma Physics, Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2012-09-15

    A new approach for investigating ionosphere chemical depletion in the laboratory is introduced. Air glow discharge plasma closely resembling the ionosphere in both composition and chemical reactions is used as the artificially created ionosphere. The ionospheric depletion experiment is accomplished by releasing chemicals such as SF{sub 6}, CCl{sub 2}F{sub 2}, and CO{sub 2} into the model discharge. The evolution of the electron density is investigated by varying the plasma pressure and input power. It is found that the negative ion (SF{sub 6}{sup -}, CCl{sub 2}F{sub 2}{sup -}) intermediary species provide larger reduction of the electron density than the positive ion (CO{sub 2}{sup +}) intermediary species. The negative ion intermediary species are also more efficient in producing ionospheric holes because of their fast reaction rates. Airglow enhancement attributed to SF{sub 6} and CO{sub 2} releases agrees well with the published data. Compared to the traditional methods, the new scheme is simpler to use, both in the release of chemicals and in the electron density measurements. It is therefore more efficient for investigating the release of chemicals in the ionosphere.

  8. Response of ionosphere and thermosphere during radial interplanetary magnetic field

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Luehr, Hermann; Shue, Jihong

    2014-05-01

    The configurations of ionosphere and thermosphere have been investigated by using high-resolution measurements of CHAMP satellite. During the period IMF By and Bz components are weak and Bx keeps pointing to the Earth for almost 10 hours. The geomagnetic indices Dst is about -40 nT and AE about 100 nT on average during the interest period. The CPCP (cross polar cap potential) output by AMIE and calculated from DMSP observations have average values of 15-20 kV. Obvious hemispheric differences are shown in the configurations of FACs on the dayside and nightside. In the south pole FACs diminish in intensity with magnitudes below 0.25 µA/m2, the plasma convection retains its quiet time two cell flow pattern, and the air density is quiet low. However, there are obvious activities in the north cusp FACs. One pair of FACs emerges in the north cusp region, which shows opposite polarities to DPY FACs. The new type of currents is accompanied by sunward plasma flow channels. These ionospheric features might be manifestations of the magnetic reconnection processes occurring in the north magnetospheric flanks. The enhanced ionospheric current systems have deposited large amount of energies into the thermosphere, causing enhanced air densities in the cusp region, which subsequently propagate equatorward both on the dayside and nightside. Although the radial IMF is considered as geomagnetic quiet condition, the present study has demonstrated for the first time there are prevailing energy inputs from the magnetosphere to both the ionosphere and thermosphere in the polar cusp region.

  9. Traveling ionospheric disturbances and their relations to storm-enhanced density features and plasma density irregularities in the local evening and nighttime hours of the Halloween superstorms of 29–31 October 2003

    Microsoft Academic Search

    Ildiko Horvath; Brian C. Lovell

    2010-01-01

    This study focuses on the local evening or nighttime hours of the Halloween superstorms. Its database, containing multi-instrument Defense Meteorological Satellite Program data plus ionosonde and magnetometer data, allowed us to investigate the various plasma density features developed and the impact of traveling ionospheric disturbances (TIDs), drift perturbations, and South Atlantic Magnetic Anomaly (SAMA) effects on them. We identified the

  10. Momentum coupling in ionospheric critical ionization velocity experiments

    Microsoft Academic Search

    N. Brenning; O. Bolin

    1993-01-01

    The critical ionization velocity (CIV) effect is a process that can rapidly ionize a neutral gas which moves through a magnetized plasma. In ionospheric injection experiments, the neutral gas component is released at high velocity with respect to the ionosphere from a rocket or a satellite. Efficient momentum coupling between the injected cloud and the ambient ionosphere is achieved by

  11. Effect of Precipitating Electrons on Ring Current Energy Content, Ionospheric Conductance, and Thermospheric Properties

    NASA Astrophysics Data System (ADS)

    Chen, M.; Lemon, C. L.; Walterscheid, R. L.; Yoo, B.; Hecht, J. H.; Shprits, Y.; Orlova, K.; Schulz, M.; Evans, J. S.

    2014-12-01

    We investigate how scattering of electrons by waves in the plasma sheet and plasmasphere affects precipitating energy flux distributions during magnetic storms, how the precipitating electrons modify the ionospheric Hall and Pederson conductivity and electric potential, how these processes feedback on magnetospheric particle transport and redistribute the ring current, and how the ionization and energy deposition of precipitating electrons affects thermospheric winds and temperature. Our main approach is to couple simulation models: (1) the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere, (2) the B3c transport model for electron-proton-hydrogen atom aurora in the ionosphere, and (3) the Thermosphere-Ionsphere-Electrodynamics General Circulation Model (TIEGCM) of the ionosphere and thermosphere. Realistic descriptions of electron pitch-angle diffusion by whistler chorus in the plasma sheet/magnetotail and hiss in the plasmasphere are included in the RCM-E. We use parameterized rates of electron pitch-angle scattering with whistler chorus of Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time. To study how the precipitating electron energy flux distributions affect ionospheric conductivity and ionospheric electric potential patterns, we have performed a one-way coupling of the RCM-E and ionospheric B3c model. The simulated precipitating electron flux distributions are used to specify the energy flux and particle heating due to precipitating auroral electrons for TIEGCM simulations of the neutral atmosphere. We simulate a storm event and compare simulated quantities with in situ observations.

  12. Microwave heating of the lower ionosphere

    NASA Technical Reports Server (NTRS)

    Meltz, G.; Nighan, W. L.

    1980-01-01

    Changes in the properties of the lower ionosphere due to ohmic heating of the plasma by the solar power satellite (SPS) microwave power beam are considered. The development of a predictive model of the underdense interaction of an electromagnetic beam and the lower ionosphere is described. The extent to which the Platteville and Arecibo experiments simulate SPS conditions is considered.

  13. Modeling longitudinal variations the low latitude ionosphere

    Microsoft Academic Search

    S. L. England; T. J. Immel; J. D. Huba; S. B. Mende

    2006-01-01

    A new large-scale longitudinal structure has recently been discovered in the equatorial ionosphere. The peak plasma density and separation of the two bands of the post-sunset equatorial ionospheric anomaly (EIA) observed by the FUV instruments onboard the NASA IMAGE and TIMED satellites were found to vary significantly, with maxima in 4 sectors around the planet during equinox. It has been

  14. Formation and evolution of the ionospheric plasma density shoulder and its relationship to the superfountain effects investigated during the 6 November 2001 great storm

    NASA Astrophysics Data System (ADS)

    Horvath, Ildiko; Lovell, Brian C.

    2008-12-01

    This study investigates the 6 November 2001 great storm's impact on the topside ionosphere utilizing data from the onboard TOPEX/Poseidon-NASA altimeter, Defense Meteorological Satellite Program-Special Sensor Ions, Electrons and Scintillation instruments and ACE interplanetary observatory. A set of field-aligned profiles demonstrate the storm evolution, caused by the precursor and promptly penetrating interplanetary eastward electric (E) fields, and strong equatorward winds reducing chemical loss, during the long-duration negative BZ events. At daytime-evening, the forward fountain experienced repeated strengthening, as the net eastward E field suddenly increased. The resultant symmetrical equatorial anomaly exhibited a continuous increase, while the energy inputs at both auroral regions were similar. In both hemispheres, by progressing poleward, a midlatitude shoulder exhibiting increased plasma densities, a plasma-density dropoff (steep gradient) and a plasma depletion appeared. These features were maintained while the reverse fountain operated. At the dropoff, elevated temperatures indicated the plasmapause. Consequently, the plasma depletion was the signature of plasmaspheric erosion. In each hemisphere, an isolated plasma flow, supplying the minimum plasma, was detected at the shoulder. Plasmaspheric compression, due to the enhanced E fields, could trigger this plasma flow. Exhibiting strong longitudinal variation at evening-nighttime, the shoulder increased 306% over the southeastern Pacific, where the nighttime Weddell Sea Anomaly (WSA) appeared before the storm. There, the shoulder indicated the storm-enhanced equatorward section of the quiet time WSA. Owing to the substantial equatorward plasmapause movement, a larger poleward section of the quiet time WSA eroded away, leaving a large depletion behind. This study reports first these (northern, southern) plasma flows and dramatic storm effects on a nighttime WSA.

  15. Cross-B convection of artificially created, negative-ion clouds and plasma depressions - Low-speed flow

    NASA Technical Reports Server (NTRS)

    Bernhardt, Paul A.

    1988-01-01

    A negative-ion, positive-ion plasma produced by the release of an electron attachment chemical into the F region becomes electrically polarized by collisions with neutrals moving across magnetic field lines. The resulting electric field causes E x B drift of the two ion species and the residual electrons. The cross-field flow of the modified ionosphere is computed using a two-dimensional numerical simulation which includes electron attachment and mutual neutralization chemistry, self-consistent electric fields, and three-species plasma transport. The velocity of the plasma is initially in the direction of the neutral wind because the negative-ion cloud is a Pedersen conductivity enhancement. As the positive and negative ions react, the Pedersen conductivity becomes depressed below the ambient value and the velocity of the plasma reverses direction. A plasma hole remains after the positive and negative ions have mutually neutralized. The E x B gradient drift instability produces irregularities on the upwind edge of the hole.

  16. On the Symmetry of Ionospheric Polar Cap Patch Exits Around Magnetic Midnight

    NASA Astrophysics Data System (ADS)

    Moen, J. I.; Hosokawa, K.; Gulbrandsen, N.; Clausen, L.

    2014-12-01

    We present continuous observations of polar cap patches exiting the polar cap ionosphere into the night time auoral oval. Satellite images of the auroral oval and all-sky camera observations of 630.0 nm airglow patches superimposed onto SuperDARN convection maps, reveals a detailed picture on how patches exiting the polar cap and return to the dayside at night, on both the dusk convection cell and the dawn convection cell. We also present eight years of statistics demonstrating that the MLT distribution of patch exits are marginally affected by the IMF BY polarity 3-4 hours around midnight. Synthesizing our observations with previous results there are two, possibly related, explanations to why patches populate both convection cells almost symmetrically. i) Intake of patch material occur on both convection cells for both IMF BY polarities. ii) According to the patch formation model by Lockwood and Carlson et al. [1992] the excitation of flow associated with transient dayside reconnection produces cigar-shaped patches stretching across both the morning and the evening convection cells. Applying the dynamic polar cap flow model by Cowley and Lockwood [1992], we suggest that dawn-dusk elongated patches may be torn apart at night when they are grabbed by transient tail reconnection. The associated twin cell flow disturbance expanding from the reconnection region will divert plasma towards dawn and dusk. This may explain the observed exits on both convection cells.

  17. Empirical models for the plasma convection at high latitudes from Millstone Hill observations

    SciTech Connect

    Holt, J.M.; Wand, R.H.; Evans, J.V.; Oliver, W.L.

    1987-01-01

    Since 1978, radar observations of F region electric fields within the region 55/sup 0/<..lambda..<75/sup 0/ have been made from Millstone Hill (42.6/sup 0/N, 71.5/sup 0/W). Average convection patterns have been calculated from the ion drift data gathered in 109 of these experiments conducted between January 1978 and August 1981. Most of the experiments lasted between 24 and 48 hours, and over 3,700,000 values of the line-of-sight velocity were determined and included in the averages. The observed velocities were sorted into ''bins'' of 1/2-hour intervals of magnetic local time and 2/sup 0/ intervals of apex latitude. Each of these cells had been viewed by the radar over a wide range of aspect angles in the course of the 109 experiments, allowing the average vector velocity to be determined. The data were separated further into three levels of Kp, according to whether the interplanetary magnetic field (IMF) was ''toward'' or ''away'' from the sun, and by season. The average patterns are discussed and compared with earlier models based on satellite and incoherent scatter data. There is an expansion and intensification of the pattern with Kp for all seasons and IMF orientations. The polar cap entry and exit points of the plasma, the center of the cells, and the polar cap boundary all depend on the IMF. The Harang discontinuity, which can be seen clearly on individual days, is largely lost in the averages.

  18. Physical Processes for Driving Ionospheric Outflows in Global Simulations

    NASA Technical Reports Server (NTRS)

    Moore, Thomas Earle; Strangeway, Robert J.

    2009-01-01

    We review and assess the importance of processes thought to drive ionospheric outflows, linking them as appropriate to the solar wind and interplanetary magnetic field, and to the spatial and temporal distribution of their magnetospheric internal responses. These begin with the diffuse effects of photoionization and thermal equilibrium of the ionospheric topside, enhancing Jeans' escape, with ambipolar diffusion and acceleration. Auroral outflows begin with dayside reconnexion and resultant field-aligned currents and driven convection. These produce plasmaspheric plumes, collisional heating and wave-particle interactions, centrifugal acceleration, and auroral acceleration by parallel electric fields, including enhanced ambipolar fields from electron heating by precipitating particles. Observations and simulations show that solar wind energy dissipation into the atmosphere is concentrated by the geomagnetic field into auroral regions with an amplification factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Internal plasmas thus enable electromagnetic driving via coupling to the plasma, neutral gas and by extension, the entire body " We assess the Importance of each of these processes in terms of local escape flux production as well as global outflow, and suggest methods for their implementation within multispecies global simulation codes. We complete 'he survey with an assessment of outstanding obstacles to this objective.

  19. Solar zenith angle dependence of plasma density and temperature in the polar cap ionosphere and low-altitude magnetosphere during geomagnetically quiet periods at solar maximum

    NASA Astrophysics Data System (ADS)

    Kitamura, N.; Ogawa, Y.; Nishimura, Y.; Terada, N.; Ono, T.; Shinbori, A.; Kumamoto, A.; Truhlik, V.; Smilauer, J.

    2011-08-01

    We constructed an empirical model of the electron density profile with solar zenith angle (SZA) dependence in the polar cap during geomagnetically quiet periods using 63 months of Akebono satellite observations at solar maximum. The electron density profile exhibits a transition at ˜2000 km altitude only under dark conditions. The electron density and scale height at low altitudes change drastically, by factors of 25 (at 2300 km altitude) and 2.0, respectively, as the SZA increases from 90° to 120°. The SZA dependence of the ion and electron temperatures is also investigated statistically on the basis of data obtained by the Intercosmos satellites and European Incoherent Scatter (EISCAT) Svalbard radar (ESR). A drastic change in the electron temperature occurs near the terminator, similarly to that in the electron density profile obtained by the Akebono satellite. The sum of the ion and electron temperatures obtained by the ESR (˜6500 K at ˜1050 km altitude under sunlit conditions and ˜3000 K at ˜750 km altitude under dark conditions) agrees well with the scale height at low altitudes obtained from the Akebono observations, assuming that the temperature is constant and that O+ ions are dominant. Comparisons between the present statistical results (SZA dependence of the electron density and ion and electron temperatures) and modeling studies of the polar wind indicate that the plasma density profile (especially of the O+ ion density) in the polar cap is strongly controlled by solar radiation onto the ionosphere by changing ion and electron temperatures in the ionosphere during geomagnetically quiet periods.

  20. Attenuation of radio signals by the ionosphere of Mars: Theoretical development and application to MARSIS observations

    Microsoft Academic Search

    Paul Withers

    2011-01-01

    We investigate the ionospheric conditions required to explain Mars Express Mars Advanced Radar for Subsurface and Ionosphere Sounding topside radar sounder observations of ionospheric attenuation in excess of 13 dB at 5 MHz during solar energetic particle events. We develop theoretical expressions for the attenuation caused by a layer of ionospheric plasma in cases of high, intermediate, and low radio

  1. Earth Planets Space, 64, 113120, 2012 Upper ionosphere of Mars is not axially symmetrical

    E-print Network

    Gurnett, Donald A.

    Earth Planets Space, 64, 113­120, 2012 Upper ionosphere of Mars is not axially symmetrical E ionosphere (h 400 km) is strongly azimuthally asymmetrical. There are several factors, e.g., the crustal to formation of ionospheric swells and valleys. It is shown that expansion of the ionospheric plasma along

  2. Plasma and electromagnetic effects in the ionosphere related to the dynamics of charged aerosols in the lower atmosphere

    Microsoft Academic Search

    V. M. Sorokin

    2007-01-01

    The paper presents a physical model of the electrodynamic effect on the ionosphere of natural and artificial processes that\\u000a occur in the near-Earth atmospheric layer and are accompanied by the transfer of charged aerosols in the atmosphere. These\\u000a processes include the preparation of earthquakes and typhoons, dust storms, and nuclear accidents. The model is based experimentally\\u000a on satellite and ground-based

  3. Modulation of polar patches in the high-latitude nightside ionosphere by substorm activity

    NASA Astrophysics Data System (ADS)

    Wood, A. G.; Pryse, S. E.; Moen, J.

    2009-04-01

    Results are presented from a multi-instrument study showing the influence of geomagnetic substorm activity on the spatial distribution of the high-latitude ionospheric plasma. Incoherent scatter radar and radio tomography measurements were used to directly observe the remnants of polar patches in the nightside ionosphere and to investigate their characteristics. The patches occurred under conditions of IMF Bz negative and IMF By negative. They were attributed to dayside photoionisation transported by the high-latitude convection pattern across the polar cap and into the nighttime European sector. The patches on the nightside were separated by some 5° latitude during substorm expansion, but this was reduced to some 2° when the activity had subsided. The different patch separations resulted from the expansion and contraction of the high-latitude plasma convection pattern on the nightside in response to the substorm activity. The patches of larger separation occurred in the antisunward cross-polar flow as it entered the nightside sector. Those of smaller separation were also in antisunward flow, but close to the equatorward edge of the convection pattern, in the slower, diverging flow at the Harang discontinuity. A patch repetition time of some 10 to 30 min was estimated depending on the phase of the substorm.

  4. Topside Ionospheric Sounder for CubeSats

    NASA Astrophysics Data System (ADS)

    Swenson, C.; Pratt, J.; Fish, C. S.; Winkler, C.; Pilinski, M.; Azeem, I.; Crowley, G.; Jeppesen, M.; Martineau, R.

    2014-12-01

    This presentation will outline the design of a Topside Ionospheric Sounder (TIS) for CubeSats. In the same way that an ionosonde measures the ionospheric profile from the ground, a Topside Sounder measures the ionospheric profile from a location above the F-region peak. The TIS will address the need for increased space situational awareness and environmental monitoring by estimating electron density profiles in the topside of the ionosphere. The TIS will measure topside electron density profiles for plasma frequencies ranging from 0.89 MHz to 28.4 MHz below the satellite altitude. The precision of the measurement will be 5% or 10,000 p/cm^3. The TIS average power consumption will be below 10 W and a mass of less than 10 kg, so it is appropriate for a 6U Cubesat (or multiple of that size). The sounder will operate via a transmitted frequency sweep across the desired plasma frequencies which, upon reception, can be differenced to determine range and density information of the topside ionosphere. The velocity of the spacecraft necessitates careful balancing of range resolution and frequency knowledge requirements as well as novel processing techniques to correctly associate the return signal with the correct plasma frequency. TIS is being designed to provide a low cost, low mass spacecraft that can provide accurate topside profiles of the ionospheric electron density in order to further understanding of ionospheric structure and dynamic processes in the ionosphere.

  5. Reconnection driven lobe convection: Interball tail probe observations and global simulations

    NASA Astrophysics Data System (ADS)

    Raeder, J.; Vaisberg, O.; Smirnov, V.; Avanov, L.

    2000-07-01

    We present Interball Tail Probe observations from the high latitude mid-tail magnetopause which provide evidence of reconnection between the interplanetary magnetic field (IMF) and lobe field lines during a 6 h interval of stable northward and dawnward IMF on October 19, 1995. Results from a global magnetohydrodynamic simulation for this interval compare well with the Interball observations. With the simulations, we provide an extended global view of this event which gives us insight into the reconnection and convection dynamics of the magnetosphere. We find that reconnection occurs in a region of limited spatial extent near the terminator and where the IMF and the lobe field are anti-parallel. Reconnected IMF field lines drape over the dayside magnetosphere, convect along the flanks into the nightside, and enter the magnetotail through a small entry window that is located in the flank opposite to the reconnection site. Ionospheric convection is consistent with previous observations under similar IMF conditions and exhibits a two cell pattern with a dominant lobe cell over the pole. The magnetic mapping between the ionosphere and the lobe boundary is characterized by two singularities: the narrow entry window in the tail maps to a 6 h wide section of the ionospheric lobe cell. A singular mapping line cuts the lobe cell open and maps to almost the entire tail magnetopause. By this singularity the magnetosphere avoids having a stagnation point, i.e., the lobe cell center maps to a tailward convecting field line. The existence of singularities in the magnetic mapping between the ionosphere and the tail has important implications for the study of tail-ionosphere coupling via empirical magnetic field models. Because the lobe-IMF reconnection cuts away old lobe flux and replaces it with flux tubes of magnetosheath origin, solar wind plasma enters the lobes in a process that is similar to the one that operates during southward IMF.

  6. Global Circulation and Temperature Structure of Thermosphere With High-Latitude Plasma Convection

    Microsoft Academic Search

    R. G. Roble; R. E. Dickinson; E. C. Ridley

    1982-01-01

    Tliis paper examines the effect of magnetospheric convection in modifying the diurnal neutral gas temperature distribution and circulation of the thermosphere for equinox conditions, using NCAR's thermospheric general circulation model. Numerical experiments are presented to illustrate the differences in temperature structure and circulation due to (1) solar heating alone, (2) solar heating plus i31asma convection with coincident geographic and geomagnetic

  7. Investigation of localized 2D convection mapping based on artificially generated Swarm ion drift data

    NASA Astrophysics Data System (ADS)

    Fiori, R. A. D.; Boteler, D. H.; Koustov, A. V.; Knudsen, D.; Burchill, J. K.

    2014-07-01

    Ionospheric plasma flow is an indicator of the interconnection between the solar wind, interplanetary magnetic field (IMF), and Earth’s magnetosphere. Ionospheric convection has been mapped in the past using either a widespread data set for instantaneous convection mapping over a short time period or data from an instrument measuring convection in a spatially confined region over a long time period for the purpose of building a statistically averaged convection pattern. This study explores convection mapping using a spherical cap harmonic analysis (SCHA) technique within a localized spherical cap based on data that will be available from the Swarm three-satellite constellation. Convection is mapped in the vicinity of hypothetical Swarm satellite tracks where it is adequately constrained by data. By using statistical models to emulate Swarm measurements, we demonstrate that such mapping can be successful based on data from the Swarm A and Swarm B satellites. Convection is divided into well constrained and poorly constrained subsets to determine parameters characterizing goodness-of-fit based on known quantities. Using the subset of well constrained maps, it is determined that convection is best mapped for a spherical cap having an angular radius of ?c=10°. The difference between the maximum mapped convection and the maximum velocity measured along the satellite track (?v) is introduced to evaluate goodness-of-fit. For the examples presented in this paper, we show that a threshold value of ?v=281 m/s successfully differentiates between well and poorly constrained maps 77.6% of the time. It is shown that convection can be represented over a larger region through the use of multiple spherical caps.

  8. Low- and mid-latitude ionospheric electric fields during the January 1984 GISMOS campaign

    NASA Technical Reports Server (NTRS)

    Fejer, B. G.; Kelley, M. C.; Senior, C.; De La Beaujardiere, O.; Lepping, R.

    1990-01-01

    The electrical coupling between the high-, middle-, and low-latitude ionospheres during January 17-19, 1984 is examined, using interplanetary and high-latitude magnetic field data together with F region plasma drift measurements from the EISCAT, Sondre Stromfjord, Millstone Hill, Saint-Santin, Arecibo, and Jicamarca incoherent scatter radars. The penetration both the zonal and meridional electric field components of high-latitude origin into the low-latitude and the equatorial ionospheres are studied. The observations in the postmidnight sector are used to compare the longitudinal variations of the zonal perturbation electric field with predictions made from global convection models. The results show that the meridional electric field perturbations are considerably more attenuated with decreasing latitude than the zonal fluctuations. It is concluded that variations in the meridional electric field at low latitudes are largely due to dynamo effects.

  9. HF Radar for Long-Range Monitoring of Ionospheric Irregularities in the Equatorial Region

    NASA Astrophysics Data System (ADS)

    Pedersen, T. R.; Parris, R. T.; Dao, E. V.

    2014-12-01

    Ionospheric instabilities associated with plasma bubbles in the equatorial region are one of the major space weather impacts, creating scintillation that affects satellite communications and navigation as well as spread-F and propagation effects on lower frequency systems. Coherent scatter radars can be used to detect the presence of irregularities at a scale size corresponding to half the wavelength of the radar when the raypaths are perpendicular to the magnetic field. A number of vertical incidence radars operating in the VHF range near the magnetic equator use this effect to map out vertical irregularity structure in bubbles, while at high latitudes in both the northern and more recently southern hemisphere, HF radars in the SuperDARN network have successfully used refraction along near-horizontal paths to reach perpendicularity with the near-vertical magnetic field and map out ionospheric convection and irregularity structure over fields of view thousands of km across. In the equatorial region, perpendicularity can be obtained anywhere within a near-vertical plane even without refraction, although refraction can be used to achieve long ranges after one or more reflections from the earth's surface and bottomside ionosphere. This potentially provides a means of detecting and monitoring equatorial plasma bubbles over the oceans from long ranges using a small number of ground-based sites. We discuss the possible echoes that could be detected by such a system, the likely propagation modes and characteristics, and means of obtaining and utilizing elevation angle information to correctly locate distant plasma bubbles.

  10. A snapshot of the polar ionosphere. [satellite observation of F layer and topside

    NASA Technical Reports Server (NTRS)

    Whitteker, J. H.; Brace, L. H.; Maier, E. J.; Burrows, J. R.; Dodson, W. H.; Winningham, J. D.

    1976-01-01

    This paper presents a picture of the north polar F layer and topside ionosphere obtained primarily from three satellites (Alouette 2, ISIS 1, ISIS 2) that passed over the region within a time interval of about 50 min on a magnetically quiet day. The horizontal distribution of electron densities at the peak of the F layer is found to be similar to synoptic results from the IGY. Energetic-particle and ionospheric-plasma data are also presented, and the F-layer data are discussed in terms of these measurements as well as in terms of electric-field and neutral N2 density measurements made by other satellites on other occasions. The major feature observed is a tongue of F-region ionization extending from the dayside across the polar cap, which is accounted for by antisunward drift due to magnetospheric convection. In the F layer and topside ionosphere, the main effect of auroral precipitation appears to be heating and expansion of the topside. A region of low F-layer density appears on the morning side of the polar cap, which may be due to convection and possibly also to enhanced N2 densities.

  11. Effects of ionospheric oxygen on magnetospheric structure and dynamics

    NASA Astrophysics Data System (ADS)

    Garcia-Sage, Katherine

    During geomagnetically active times, ionospheric O + can contribute a significant fraction of the magnetospheric mass and energy densities. The global response of Earth's magnetosphere to the presence of ionospheric oxygen is still largely unknown and impossible to examine fully with in situ, single point satellite measurements. Global magnetohydrodynamic (MHD) models provide a picture of this large-scale response to ionospheric outflow. The goal of this dissertation is to examine the behavior and effects of outflowing oxygen in a multi-fluid MHD model by determining (1) how O+ outflow from different regions of the ionosphere contributes to plasma sheet populations and (2) the effect of these oxygen populations on convection and global magnetospheric structure. I implement two empirical outflow models at the inner boundary of the recently-developed Multi-Fluid Lyon-Fedder-Mobarry MHD code and examine the response of the model to various outflow conditions. A model based on data from the Akebono spacecraft (Ebihara et al., 2006) provides a low-energy polar and auroral region outflow, whereas a model based on data from the FAST spacecraft (Strangeway et al., 2005) provides higher-energy outflow confined to the auroral regions. Using the Akebono model outflow, I show that both centrifugal acceleration and pressure gradients accelerate thermal O+ along the magnetic field into the plasma sheet and downtail into the solar wind. I examine O+ and H + plasma sheet populations for different outflow and solar wind conditions. To account for observed densities, nightside outflows must be augmented by polar wind, cusp outflows, or both. O+ outflow in general, and nightside outflow in particular, loads the plasma sheet with O +, inflating the plasma sheet, increasing the width of the tail and distance to the tail x-line, and reducing cross polar cap potential (CPCP). These effects are shown to relate to the width of the magnetosheath, indicating that the reduction in CPCP may be due to changes in the bow shock and magnetosheath that divert the solar wind around the magnetosphere. Finally, I show that during a realistic substorm simulation, the timing and strength of substorms are changed by a global O+ outflow.

  12. Disturbance Effects Seen in the Midlatitude Ionosphere with SuperDARN

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Baker, J. B. H.; Bristow, W. A.; Shepherd, S. G.; Miller, E. S.

    2014-12-01

    With the construction of the first midlatitude SuperDARN radar at NASA Wallops Flight Facility in 2005 it quickly became apparent that much activity can be observed in the midlatitude ionosphere even outside of large storm intervals. Over the last five years a chain of SuperDARN radars has been deployed at midlatitudes under the NSF Mid-Sized Infrastructure program that extends across the western hemisphere as far as east Asia. The new radars are providing unprecedented large-scale views of disturbance effects such as the storm-time expansion of auroral flows, subauroral polarization streams (SAPS), and travelling ionospheric disturbances (TIDs). When combined with large-scale mapping of GPS/TEC it is possible to observe directly the generation of plasma structures such as storm-enhanced density features (SEDs), tongues of ionization (TOIs), and polar cap patches, and to understand their dependence on the dynamic convection pattern reaching to the mid-latitude region. One unexpected result is the observation of backscatter from irregularities distributed throughout the quiet-time nightside subauroral ionosphere. This phenomenon gives us views of electric fields that are conjugate to the inner magnetosphere and also reveals the occurrence of large transients in the quiet-time subauroral electric fields. In this talk we summarize over the effects identified to date and discuss the insights gained in understanding the disturbed midlatitude ionosphere.

  13. Comparisons of DC Electric Field Measurements in the Ionosphere and Inner Magnetosphere Using Measurements from the SuperDARN Radars and the Van Allen Probes EFW Instrument

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J.; Kunduri, B.; Wygant, J. R.; Thaller, S. A.; Baker, J. B.; de Larquier, S.; Erickson, P. J.; Foster, J. C.; Clausen, L.; Wilder, F. D.; Shepherd, S. G.; Bristow, W. A.

    2013-12-01

    The SuperDARN radars cover large geographical regions in both hemispheres and provide excellent opportunities for making measurements of ionospheric convection in magnetically connected regions. The ionospheric footpoints of the Van Allen Probes when traced along magnetic field lines often fall into the fields-of-view of the new mid-latitude radars. The most favorable conjunctions take place on the nightside in the North American sector when the radars commonly observe subauroral plasma drifts that are conjugate to the plasma boundary layer. The ionospheric electric fields exhibit structure and variability over wide ranges of spatial and temporal scales. The ground-based observations can be compared with measurements of dc electric fields at the positions of the Van Allen Probes spacecraft using data from the Electric Fields and Waves (EFW) instrument for insight into the coupling between the magnetosphere and ionosphere and the dependencies on scale lengths. In this talk we report on a survey of conjunctive periods and describe the extent to which the dc electric fields are found to be conjugate between the inner magnetosphere and ionosphere. We discuss the implications of apparent non conjugacy in terms of coupling across various scale lengths, uncertainties in the field line mapping, and the effects of possible field-aligned potential drops.

  14. Plasmapause Convects to the Magnetopause During Halloween Solar Storm

    NSDL National Science Digital Library

    Tom Bridgman

    2004-12-15

    The plasmasphere is a region of ionospheric plasma which co-rotates with the Earth, carried by the magnetic field lines. The plasmapause marks the outer boundary of this region. This colder plasma is more easily moved by the electric fields created by strong solar storms. In the Halloween 2003 event, these fields convected some of the cold plasma out to the magnetopause (grey, semi-transparent surface) and reduced the size of the cold plasma region near the Earth. For this visualization, the 3-dimensional structure was constructed from the equatorial profile of the plasmapause (as measured by IMAGE-EUV data) by extending the region along field lines of a simple dipole field.

  15. Global aspects of solar wind–ionosphere interactions

    Microsoft Academic Search

    T. E. Moore; M.-C. Fok; D. C. Delcourt; S. P. Slinker; J. A. Fedder

    2007-01-01

    Recent observations have quantified the auroral wind O+ outflow in response to magnetospheric inputs to the ionosphere, notably Poynting energy flux and precipitating electron density. For moderate to high activity periods, ionospheric O+ is observed to become a significant or dominant component of plasma pressure in the inner plasma sheet and ring current regions. Using a global circulation model of

  16. Ionospheric wave spectrum measurements

    NASA Technical Reports Server (NTRS)

    Harker, K. J.; Ilic, D. B.; Crawford, F. W.

    1979-01-01

    The local spectrum S(k, omega) of either potential or electron-density fluctuations can be used to determine macroscopic-plasma characteristics such as the local density and temperature, transport coefficients, and drift current. This local spectrum can be determined by measuring the cross-power spectrum. The paper examines the practicality of using the cross-power spectrum analyzer on the Space Shuttle to measure ionospheric parameters. Particular attention is given to investigating the integration time required to measure the cross-power spectral density to a desired accuracy.

  17. Results of the first statistical study of pioneer Venus orbiter plasma observations in the distant Venus tail: Evidence for a hemispheric asymmetry in the pickup of ionospheric ions

    SciTech Connect

    Intriligator, D.S. (Carmel Research Center, Santa Monica, CA (USA))

    1989-02-01

    Pioneer Venus Orbiter plasma and magnetometer observations from the first nine tail seasons of crossings of the Venus wake are used to study ion pickup in the far wake of an unmagnetized object embedded in the solar wind. This first statistical study treats all of the plasma spectra containing pickup ions in the vicinity of the Venus tail. The author finds a hemispheric asymmetry in the pickup of ionospheric ions, with approximately four times more O{sup +} events observed in the northern magnetic hemisphere (where Z{double prime} > O), i.e., the induced electric field points outward, (away from the ionopause boundary) than in the southern (Z{double prime} < O) magnetic hemisphere. Out of a total of 167 large O{sup +} events, 125, or 75%, occurred in the northern hemisphere when position is calculated in terms of Venus radii and 129 or 77% occurred in the northern hemisphere when position is expressed in gyroradii. This hemisphere asymmetry in ion pickup is consistent with the prediction of the Cloutier et al. (1974) mass loading model for Venusian ions above the ionopause boundary.

  18. Connections between plasma sheet transport, Region 2 currents, and entropy changes associated with convection, steady magnetospheric convection periods, and substorms

    NASA Astrophysics Data System (ADS)

    Lyons, Larry R.; Wang, Chih-Ping; Gkioulidou, Matina; Zou, Shasha

    2009-09-01

    Here we describe how energy-dependent magnetic drift in the presence of a pressure gradient in the direction of the drift leads to a divergence of perpendicular particle flux, and that this violates conservation of flux tube particle content. We address how, within the plasma sheet, this divergence of particle flux should be expected to lead simultaneously to the divergence of perpendicular current that drives the Region 2 (R2) current system and to significant violation of entropy conservation. The modeling results of Wang et al. (2004b) show that the above violation of entropy conservation due to magnetic drift, when taken together with magnetic field stretching, offers a resolution to the pressure crises question. On the basis of our argument that the same energy-dependent magnetic drift effect leads to the perpendicular divergence that drives the R2 field-aligned current system and the violation of entropy conservation, we suggest that the existence of the R2 current system can by itself be viewed as a signature of violation of entropy conservation. Finally, we propose that observational evidence suggests that an enhanced rate of entropy reduction and R2 currents resulting from particle divergence within the vicinity of the Harang reversal may be a critical aspect of the substorm expansion phase.

  19. Ionospheric redistribution during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Immel, T. J.; Mannucci, A. J.

    2013-12-01

    The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dst<-100 nT) sets, we find variation in storm strength that corresponds closely to the TEC variation but follows it by 3-6h. For this and other reasons detailed in this report, we conclude that the UT-dependent peak in storm time TEC is likely not related to the magnitude of external storm time forcing but more likely attributable to phenomena such as the low magnetic field in the South American region. The large Dst variation suggests a possible system-level effect of the observed variation in ionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow.

  20. Ionospheric redistribution during geomagnetic storms

    PubMed Central

    Immel, T J; Mannucci, A J

    2013-01-01

    [1]The abundance of plasma in the daytime ionosphere is often seen to grow greatly during geomagnetic storms. Recent reports suggest that the magnitude of the plasma density enhancement depends on the UT of storm onset. This possibility is investigated over a 7year period using global maps of ionospheric total electron content (TEC) produced at the Jet Propulsion Laboratory. The analysis confirms that the American sector exhibits, on average, larger storm time enhancement in ionospheric plasma content, up to 50% in the afternoon middle-latitude region and 30% in the vicinity of the high-latitude auroral cusp, with largest effect in the Southern Hemisphere. We investigate whether this effect is related to the magnitude of the causative magnetic storms. Using the same advanced Dst index employed to sort the TEC maps into quiet and active (Dstionospheric storm response on the measured strength of the terrestrial ring current, possibly connected through UT-dependent modulation of ion outflow.

  1. The source of the longitudinal asymmetry in the ionospheric tidal structure

    Microsoft Academic Search

    H. Kil; Y.-S. Kwak; S.-J. Oh; E. R. Talaat; L. J. Paxton; Y. Zhang

    2011-01-01

    The vertical plasma drift induces the ionospheric longitudinal asymmetryThe asymmetry is explained by the wave-4 and wave-3 structure phase differenceWave-3 structure is the dominant structure in the ionosphere

  2. Ionospheric modification by rocket effluents. Final report

    SciTech Connect

    Bernhardt, P.A.; Price, K.M.; da Rosa, A.V.

    1980-06-01

    This report describes experimental and theoretical studies related to ionospheric disturbances produced by rocket exhaust vapors. The purpose of our research was to estimate the ionospheric effects of the rocket launches which will be required to place the Satellite Power System (SPS) in operation. During the past year, we have developed computational tools for numerical simulation of ionospheric changes produced by the injection of rocket exhaust vapors. The theoretical work has dealt with (1) the limitations imposed by condensation phenomena in rocket exhaust; (2) complete modeling of the ionospheric depletion process including neutral gas dynamics, plasma physics, chemistry and thermal processes; and (3) the influence of the modified ionosphere on radio wave propagation. We are also reporting on electron content measurements made during the launch of HEAO-C on Sept. 20, 1979. We conclude by suggesting future experiments and areas for future research.

  3. 3D multispecies MHD studies of the interaction of the ionospheres of unmagnetized solar system bodies with the solar wind or magnetospheric plasma flows

    Microsoft Academic Search

    Yifan Liu

    2000-01-01

    We used 3D multi-species MHD models to study the solar wind interaction with the ionosphere of Mars and the magnetospheric interaction with the ionospheres of Europa and Titan. Mars, Europa and Titan are all considered to be non-magnetized bodies with an atmosphere. Therefore, the global scale solar wind\\/magnetospheric interactions with these solar system bodies are with the ionosphere\\/atmosphere systems directly.

  4. Electron and Ion Acceleration in the Unstable Auroral Ionosphere C. C. Chaston1,, J. W. Bonnell1

    E-print Network

    California at Berkeley, University of

    Electron and Ion Acceleration in the Unstable Auroral Ionosphere C. C. Chaston1,Ã, J. W. Bonnell1 the ionosphere to secondary Alfve´ n waves via the well known ionospheric feedback instability. From spacecraft observations by others. 1. Introduction Observations of plasmas above the auroral ionosphere invariably contain

  5. Some Timescales and Time Lags in the Magnetosphere-Ionosphere System

    NASA Astrophysics Data System (ADS)

    Borovsky, J. E.; Denton, M. H.

    2012-12-01

    To understand a complicated system like the solar-wind-driven magnetosphere, an assessment of characteristic timescales and the identification of operational time lags could be of use. Several (but not all) of these timescales are discussed. One dramatic internal timescale of the magnetosphere is the substorm-recurrence period of ~3 hours. Two other important timescales are the Goertz-Shan-Smith timescales for the penetration of electric fields from the solar wind to the dayside and nightside polar ionosphere; these timescales will lead to various time lags between the solar-wind electric field and various geomagnetic indices. An important operational time lag is the several-hour timescale for solar-wind plasma to enter the magnetosphere and be convected from the nightside, around the dipole, to the dayside. One more timescale will be considered: the timescale for the plasmaspheric drainage plume to form and convect to the dayside magnetopause where it can interfere with reconnection at the magnetopause.

  6. Large plasma density enhancements occurring in the northern polar region during the 6 April 2000 superstorm

    NASA Astrophysics Data System (ADS)

    Horvath, Ildiko; Lovell, Brian C.

    2014-06-01

    We focus on the ionospheric response of northern high-latitude region to the 6 April 2000 superstorm and aim to investigate how the storm-enhanced density (SED) plume plasma became distributed in the regions of auroral zone and polar cap plus to study the resultant ionospheric features and their development. Multi-instrument observational results combined with model-generated, two-cell convection maps permitted identifying the high-density plasma's origin and the underlying plasma transportation processes. Results show the plasma density feature of polar cap enhancement (PCE; ~600 × 103 i+/cm3) appearing for 7 h during the main phase and characterized by increases reaching up to 6 times of the quiet time values. Meanwhile, strong westward convections (~17,500 m/s) created low plasma densities in a wider region of the dusk cell. Oppositely, small (~750 m/s) but rigorous westward drifts drove the SED plume plasma through the auroral zone, wherein plasma densities doubled. As the SED plume plasma traveled along the convection streamlines and entered the polar cap, a continuous enhancement of the tongue of ionization (TOI) developed under steady convection conditions. However, convection changes caused slow convections and flow stagnations and thus segmented the TOI feature by locally depleting the plasma in the affected regions of the auroral zone and polar cap. From the strong correspondence of polar cap potential drop and subauroral polarization stream (SAPS), we conclude that the SAPS E-field strength remained strong, and under its prolonged influence, the SED plume provided a continuous supply of downward flowing high-density plasma for the development and maintenance of PCEs.

  7. The current status of the ionospheric observations in NICT

    NASA Astrophysics Data System (ADS)

    Nagatsuma, Tsutomu; Murata, Ken T.; Tsugawa, Takuya; Kato, Hisao; Ishibashi, Hiromitsu

    2012-07-01

    In Japan, NICT (National Institute of Information and Communications Technology) is in charge of space weather forecasting services as a Regional Warning Center of International Space Environment Service (ISES). Also, we have been operating WDC for Ionosphere since 1957. With help of geospace environment data exchanging among the international cooperation, NICT routinely operates daily space weather forecast service to provide information on nowcasts and forecasts of solar flare, geomagnetic disturbances, solar proton event, and radio-wave propagation conditions in the ionosphere. To monitor the ionospheric condition over Japan, we have been operating domestic ionosonde network We have four station, Wakkanai, Kokubunji, Yamagawa, Okinawa. Also we have an ionospheric observatory in Syowa Station, Antarctica. Also, we are operating south-east Asia low-latitute ionospheric network (SEALION). This is for the purpose of monitoring and forecasting equatorial ionospheric disturbances, especially plasma bubbles. In the present talk, we will introduce our current activities and future perspective of the ionospheric observations in NICT.

  8. Electron temperature and heat flow in the nightside Venus ionosphere

    NASA Technical Reports Server (NTRS)

    Hoegy, W. R.; Brace, L. H.; Theis, R. F.; Mayr, H. G.

    1980-01-01

    A steady-state two-dimensional heat balance model is used to analyze the night side Venusian ionospheric electron temperatures given by the Pioneer Venus orbiter electron temperature probe. The energy calculation includes the solar EUV heating at the terminator, electron cooling to ions and neutrals, and heat conduction within the ionospheric plasma. An optimum magnetic field is derived by solving for the heat flux directions which force energy conservation while constrained by the observed temperatures within the range of 80-170 deg solar zenith angle and 160-170 km. The heat flux vectors indicate a magnetic field that connects the lower night side ionosphere to the day side ionosphere, and connects the upper ionosphere to the ionosheath. The lower ionosphere is heated through conduction of heat from the dayside, and the upper ionosphere is heated by the solar wind in the ionosheath with heat flowing downward and from the nightside to the day side.

  9. Space weather phenomena in the equatorial ionosphere

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Archana

    2013-03-01

    Our increasing dependence on space-based technological systems requires that we understand the factors that determine "space weather", which affects the operation of satellites as well as space-based communication and navigation systems. The latter are particularly vulnerable to conditions in the dip equatorial ionosphere where geometry of the geomagnetic field creates conditions for the growth of certain plasma instabilities, which produce sub-kilometer scale structure in the ionospheric plasma that are capable of scattering VHF and higher frequency radio waves. The phenomenon of the equatorial plasma bubble (EPB) that occurs in the postsunset equatorial and low latitude ionosphere is therefore an important component of space weather in this region. Forecasting of this space weather phenomenon involves not only the identification of ambient conditions responsible for the day-to-day variation in its occurrence and spatial structure during magnetically quiet periods but also understanding the influence of solar variability on these conditions. This paper discusses briefly our present understanding of the role played by certain parameters of the equatorial ionosphere in the development of EPBs and the influence of solar activity on the equatorial ionosphere, in the context of its role in the generation of ionospheric irregularities that may be detrimental to the operation of space-based communication and navigation systems.

  10. Forecast of ionospheric disturbances using a high-resolution atmosphere-ionosphere coupled model

    NASA Astrophysics Data System (ADS)

    Shinagawa, Hiroyuki; Miyoshi, Yasunobu; Fujiwara, Hitoshi; Yokoyama, Tatsuhiro; Jin, Hidekatsu

    Space weather forecasts are about to enter a stage incorporating numerical forecasts based on realistic numerical simulation, in addition to conventional methods used by forecasters to make predictions based on observational data and experience. At the National Institute of Information and Communications Technology (NICT) of Japan, we have developed an atmosphere-ionosphere coupled model, which includes the whole neutral atmosphere and the ionosphere. The model is called GAIA (Ground-to-topside model of Atmosphere and Ionosphere for Aeronomy). The present version has spatial resolution of about 1 degree in horizontal direction. In addition, we are also developing a high-resolution regional ionospheric model, which has a horizontal resolution of about 10 km.We plan to combine GAIA and the regional model to reproduce mesoscale ionospheric phenomena, such as plasma bubbles and SED (storm enhanced density). The model will be a useful tool for space weather forecast. We will report previous results, and a plan for the new model.

  11. Substorm effects observed in the auroral plasma

    NASA Technical Reports Server (NTRS)

    Burch, J. L.; Fields, S. A.; Heelis, R. A.

    1976-01-01

    The effects of substorm temporal development on high-latitude particle precipitation and ionospheric convection patterns near midnight were studied with the aid of data from Atmosphere Explorer C. During quiet periods generally Maxwellian electron precipitation is observed from the central plasma sheet, which is completely contained within the sunward flow region. As substorms grow and begin to recover, a strong sunward flow appears within the high latitude ionospheric electron trough, equatorward of the central plasma sheet electron precipitation. Intense inverted-V electron structures consistent with strong electrostatic acceleration appear near the Harang discontinuity and extend poleward to the polar cap boundary. Then the trough flow weakens, the Harang discontinuity becomes a gradual reversal, and the electron inverted-V precipitation becomes localized at the polar cap boundary.

  12. Assessing the Relative Impact of Distinct Ionospheric Outflow Populations on Geospace Dynamics using Multi-Fluid Global MHD simulations

    NASA Astrophysics Data System (ADS)

    Brambles, O.; Lotko, W.; Ouellette, J.; Zhang, B.; Lyon, J.; Wiltberger, M. J.

    2014-12-01

    Satellite observations and numerical modeling studies have demonstrated that ionospheric ion outflows of different species, source locations and energies populate and interact with distinct regions of the magnetosphere, and therefore can have profoundly different impacts on the coupled solar wind-magnetosphere-ionosphere (SWMI) system. In previous modeling studies, multi-fluid global simulations of the SWMI interaction typically use one fluid to model the solar wind and a second fluid to represent the outflowing ions. These studies are limited as they are incapable of tracking multiple, distinct ionosphere-sourced ion populations. Either significant ion populations and their influence must be excluded from the simulation or multiple ion populations must be combined into a single fluid. In this study, a multi-fluid adaption of the Lyon-Fedder-Mobarry (MFLFM) model that is capable of including numerous separate fluids is used to: (1) evaluate how different outflowing ion populations propagate in the magnetosphere and enter the tail, (2) determine their resulting magnetospheric distribution, and (3) calculate their relative impacts on SWMI coupling. The outflow flux for each population is regulated using causally driven models based on empirical data. These models include specifications for transversely accelerated O+ originating from the cusp and nightside auroral region, H+ polar wind outflow and the plasmasphere. The outflow distributions and hemispheric outflow flux resulting from these models, and their resulting composition in the magnetosphere are validated using satellite data. The effects of each individual ion source on dayside reconnection, electrodynamic magnetosphere-ionosphere coupling and magnetotail processes are evaluated. Among other effects, we find that ionospheric ions that are entrained directly into the warm plasma cloak are more effective at reducing the dayside reconnection potential than ions that are transported further downtail and are convected Earthwards in the plasma sheet.

  13. Convective transport of highly plasma protein bound drugs facilitates direct penetration into deep tissues after topical application

    PubMed Central

    Dancik, Yuri; Anissimov, Yuri G; Jepps, Owen G; Roberts, Michael S

    2012-01-01

    AIMS To relate the varying dermal, subcutaneous and muscle microdialysate concentrations found in man after topical application to the nature of the drug applied and to the underlying physiology. METHODS We developed a physiologically based pharmacokinetic model in which transport to deeper tissues was determined by tissue diffusion, blood, lymphatic and intersitial flow transport and drug properties. The model was applied to interpret published human microdialysis data, estimated in vitro dermal diffusion and protein binding affinity of drugs that have been previously applied topically in vivo and measured in deep cutaneous tissues over time. RESULTS Deeper tissue microdialysis concentrations for various drugs in vivo vary widely. Here, we show that carriage by the blood to the deeper tissues below topical application sites facilitates the transport of highly plasma protein bound drugs that penetrate the skin, leading to rapid and significant concentrations in those tissues. Hence, the fractional concentration for the highly plasma protein bound diclofenac in deeper tissues is 0.79 times that in a probe 4.5 mm below a superficial probe whereas the corresponding fractional concentration for the poorly protein bound nicotine is 0.02. Their corresponding estimated in vivo lag times for appearance of the drugs in the deeper probes were 1.1 min for diclofenac and 30 min for nicotine. CONCLUSIONS Poorly plasma protein bound drugs are mainly transported to deeper tissues after topical application by tissue diffusion whereas the transport of highly plasma protein bound drugs is additionally facilitated by convective blood, lymphatic and interstitial transport to deep tissues. PMID:21999217

  14. Penetration electric fields and global ionospheric disturbances during super magnetic storms

    Microsoft Academic Search

    C. Huang; J. Foster; A. Coster; P. Erickson; W. Rideout; L. Goncharenko; M. Colerico

    2006-01-01

    Magnetic storms represent the largest disturbances in the magnetosphere and ionosphere The interplanetary magnetic field IMF is generally southward during the main phase of magnetic storms and the interplanetary electric field can penetrate to the low-latitude ionosphere for many hours without decay Penetration electric fields play a very important role in the storm-time redistribution of the global ionospheric plasma We

  15. Ion upow and downow at the topside ionosphere observed by the EISCAT VHF radar

    E-print Network

    Boyer, Edmond

    Ion up¯ow and down¯ow at the topside ionosphere observed by the EISCAT VHF radar M. Endo1 , R to stop increasing at some KP level. Key words: Ionosphere (particle acceleration; plasma waves ¯ow from the polar ionosphere to the magnetosphere (Axford, 1968). Des- sler and Michel (1996), Bauer

  16. Mapping electron density in the ionosphere: a principal component MCMC algorithm

    E-print Network

    Budd, Chris

    Mapping electron density in the ionosphere: a principal component MCMC algorithm Eman Khorsheed are known as the ionosphere, a plasma of free electrons and positively charged atomic ions. The electron density of the ionosphere varies considerably with time of day, season, geographical location and the sun

  17. Dynamical and magnetic field time constants for Titan's ionosphere: Empirical estimates and comparisons with Venus

    E-print Network

    California at Berkeley, University of

    Dynamical and magnetic field time constants for Titan's ionosphere: Empirical estimates August 2010. [1] Plasma in Titan's ionosphere flows in response to forcing from thermal pressure to the ionospheric dynamics by using data from Cassini instruments to estimate pressures, flow speeds, and time

  18. Correlation of Alfven wave Poynting flux in the plasma sheet at 47 RE with ionospheric electron energy flux

    E-print Network

    California at Berkeley, University of

    energy flux A. Keiling,1 J. R. Wygant,1 C. Cattell,1 W. Peria,2 G. Parks,2 M. Temerin,3 F. S. Mozer,3 C to the nominal plasma sheet. Previous studies of electric fields, using ISEE 1/2 [Mozer, 1981; Cattell et al that the fields do not only map like quasi-static electric fields, as shown by previous studies [Mozer, 1981

  19. The ionospheric focused heating experiment

    SciTech Connect

    Bernhardt, P.A.; Siefring, C.L.; Rodriguez, P. [Naval Research Lab., Washington, DC (United States)] [and others] [Naval Research Lab., Washington, DC (United States); and others

    1995-09-01

    The Ionospheric Focused Heating rocket was launched on May 30, 1992. The sounding rocket carried an instrument and chemical payload along a trajectory that crossed the intersection of the beams from the 430-MHz incoherent scatter radar and the 5.1-MHz high-power radio wave facility near Arecibo. The release of 30 kg of CF{sub 3}Br into the F region at 285 km altitude produced an ionospheric hole that acted like a convergent lens to focus the HF transmission. The power density inside the radio beam was raised by 12 dB immediately after the release. A wide range of new processes were recorded by in situ and ground-based instruments. Measurements by instruments flying through the modified ionosphere show small-scale microcavities (< 1 m) and downshifted electron plasma (Langmuir) waves inside the artificial cavity, electron density spikes at the edge of the cavity, and Langmuir waves coincident with ion gyroradius (4 m) cavities near the radio wave reflection altitude. The Arecibo incoherent scatter radar showed 20 dB or greater enhancements in ion acoustic and Langmuir wave turbulence after the 5.1-MHz radio beam was focused by the artificial lens. Enhancements in airglow from chemical reactions and, possibly, electron acceleration were recorded with optical instruments. The Ionospheric Focused Heating experiment verified some of the preflight predictions and demonstrated the value of active experiments that combine high-power radio waves with chemical releases. 30 refs., 14 figs., 1 tab.

  20. LIFDAR: A Diagnostic Tool for the Ionosphere

    NASA Astrophysics Data System (ADS)

    Kia, O. E.; Rodgers, C. T.; Batholomew, J. L.

    2011-12-01

    ITT Corporation proposes a novel system to measure and monitor the ion species within the Earth's ionosphere called Laser Induced Fluorescence Detection and Ranging (LIFDAR). Unlike current ionosphere measurements that detect electrons and magnetic field, LIFDAR remotely measures the major contributing ion species to the electron plasma. The LIFDAR dataset has the added capability to demonstrate stratification and classification of the layers of the ionosphere to ultimately give a true tomographic view. We propose a proof of concept study using existing atmospheric LIDAR sensors combined with a mountaintop observatory for a single ion species that is prevalent in all layers of the atmosphere. We envision the LIFDAR concept will enable verification, validation, and exploration of the physics of the magneto-hydrodynamic models used in ionosphere forecasting community. The LIFDAR dataset will provide the necessary ion and electron density data for the system wide data gap. To begin a proof of concept, we present the science justification of the LIFDAR system based on the model photon budget. This analysis is based on the fluorescence of ionized oxygen within the ionosphere versus altitude. We use existing model abundance data of the ionosphere during normal and perturbed states. We propagate the photon uncertainties from the laser source through the atmosphere to the plasma and back to the collecting optics and detector. We calculate the expected photon budget to determine signal to noise estimates based on the targeted altitude and detection efficiency. Finally, we use these results to derive a LIFDAR observation strategy compatible with operational parameters.

  1. Lithosphere-Atmosphere-Ionosphere coupling. Main principles and practical validation

    Microsoft Academic Search

    S. Pulinets; D. Ouzounov; L. Doda

    2006-01-01

    The satellite technology (remote sensing, ionospheric plasma measurements, GPS TEC) provided opportunity to clarify the physics of the processes chain, occurring during the earthquake process and which we name Lithosphere-Atmosphere-Ionosphere (LAI) coupling. The LAI model created recently, permitted to unite different groups of scientists working in different areas by the common physical mechanism which is able to explain geochemical, atmospheric,

  2. Effects of the low-latitude ionospheric boundary condition on the global magnetosphere

    Microsoft Academic Search

    V. G. Merkin; J. G. Lyon

    2010-01-01

    In common treatment of magnetosphere-ionosphere coupling at high latitudes, the ionosphere is represented by a thin conducting spherical shell, which closes field-aligned currents generated in the magnetosphere. In this approach, the current continuity yields a Poisson equation for the electrostatic potential associated with the ionospheric convection pattern. Solution of the Poisson equation then provides a means of self-consistently describing magnetospheric

  3. Radio frequency scattering from a heated ionospheric volume. I - VHF\\/UHF field-aligned and plasma-line backscatter measurements

    Microsoft Academic Search

    J. Minkoff; P. Kugelman; I. Weissman

    1974-01-01

    It is observed that an ionospheric volume in the F layer subjected to high power HF illumination becomes an effective scattering medium for radio signals in the VHF\\/UHF frequency range. The experimental results are representative of a field-aligned scattering geometry for which the first such observations of VHF\\/UHF scattering from a heated ionospheric volume are presented. Two distinct scattering modes

  4. Studying the dynamics of magnetosphere-ionosphere (M-I) coupling by imaging the plasma density structures of the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Yizengaw, E.; Moldwin, M.

    The global density structure of the inner magnetosphere can be monitored using a combination of techniques that use ground- and space-based Global Positioning System GPS receivers Low-Earth-Orbit LEO satellites equipped with dual-band GPS receivers and the dramatically growing ground-based GPS receiver network offer an excellent opportunity for remote sensing and monitoring of the ionospheric and plasmaspheric density structure using GPS total electron content TEC tomographic reconstruction This allows us to clearly quantify magnetosphere-ionosphere M-I coupling dynamics which includes the long-standing conjecture that the mid-latitude trough and plasmapause are on the same field line This has been demonstrated globally for the first time using combination of data from IMAGE EUV images and ground- and space-based GPS receivers The two dimensional tomographic image of the ionosphere and plasmasphere provides a new ability to image the flux tube structure of ionospheric ion outflows tracking flux tube structure up to 3 17Re 20 200 km altitude for the first time Traditionally ion outflow has been detected by using a single satellite cut over the field line at a certain altitude however the tomographic reconstruction approach can reveal the entire picture of the field aligned ion outflow emanating from the cusp region This indicates that tomographic reconstruction techniques have the ability to detect narrow ionospheric ion outflows between the ionosphere and magnetosphere

  5. Effects of Gravity Waves on the Thermosphere/Ionosphere system simulated by an atmosphere-ionosphere coupled Model

    NASA Astrophysics Data System (ADS)

    Miyoshi, Y.; Jin, H.; Fujiwara, H.; Shinagawa, H.

    2013-12-01

    Behaviors of gravity waves in the thermosphere ionosphere are studied by using a whole atmosphere-ionosphere coupled model (GAIA), in which a whole atmosphere general circulation model (GCM), an ionosphere model and an electrodynamics model are integrated. The whole atmosphere GCM contains the region from the ground surface to the upper thermosphere, so that we can simulate excitation of gravity waves in the lower atmosphere and their upward propagation to the thermosphere. We have recently developed an atmosphere-ionosphere coupled model with high horizontal resolution (about 1 degree longitude by 1degree latitude). In this study, we would like to present a preliminary result obtained by the GAIA simulation. Using this coupled model, we investigate the upward propagation of gravity waves from the lower atmosphere to the thermosphere and its impact on ionospheric variability. In particular, we focus our attention on the relation between the convective activity in the troposphere and the thermosphere/ionosphere variability. Our simulation result indicates that gravity waves with a larger horizontal phase velocity (larger vertical wavelength) can penetrate into the thermosphere and affect the general circulation of the upper atmosphere. The longitudinal distribution of the gravity wave activity in low latitudes of the thermosphere is closely related to the cumulus convective activity in the tropics. The impact of the thermospheric gravity wave on the ionosphere is also discussed.

  6. Ionospheric Correction Using Tomography

    E-print Network

    Stanford University

    Ionospheric Correction Using Tomography Andrew J. Hansen Todd Walter Per Enge Stanford University to the ight crew within six seconds. The ionosphere is the foremost impedi- ment to satisfying for estimat- ing the ionosphere in real-time. Previous research has established a connection between

  7. Photochemistry of planetary ionospheres

    NASA Technical Reports Server (NTRS)

    Nagy, Andrew F.

    1987-01-01

    The dominant photochemical reactions taking place in the ionospheres of Venus, Saturn, and Comet P/Halley are presented. It is shown that the differences in the ionospheres of these celestial bodies result from the different chemistry, energetics, and dynamics of the respective atmospheres. The role of photochemistry in the formation of the individual ionospheres is discussed.

  8. Frequency characteristics of the action of powerful radio-frequency radiation on the ionospheric F layer

    SciTech Connect

    Erukhimov, L.M.; Ivanov, V.A.; Mityakov, N.A.; Uryadov, V.P.; Frolov, V.A.; Shumaev, V.V.

    1988-03-01

    The results of an investigation of the effect of artificial ionospheric nonuniformities on the characteristics of LFM signals with vertical and oblique sounding of the ionosphere are presented. A classification of the effects observed on ionograms from vertical and oblique-sounding LFM ionosonde, owing to the effect of artificial nonuniformities of different scale, is given. It was found that powerful beams of radio waves have a characteristic effect on the ionospheric plasma under conditions when moving ionospheric disturbances appear.

  9. The plasma sheet PV5/3 and nV and associated particle and energy transport for different convection strengths and AE levels

    NASA Astrophysics Data System (ADS)

    Wang, C.; Lyons, L. R.; Wolf, R. A.; Nagai, T.; Weygand, J. M.; Lui, A.

    2008-12-01

    The spatial variations of PV5/3 and nV, where P is total plasma pressure, n is number density, and V is the flux tube volume per unit magnetic flux, are crucial to understanding the large-scale plasma transport and its associated energy transfer in the plasma sheet. We have used 10 years of Geotail data and a formula for estimating V to investigate statistically the equatorial distributions of ion PV5/3 and nV in the nightside plasma sheet between r = 10 to 30 RE. We have examined the distributions under three different conditions according to the cross polar-cap potential drop and AE index: (1) weak convection and low geomagnetic activity, (2) enhanced convection and low geomagnetic activity, and (3) enhanced convection and high geomagnetic activity. The overall nV is seen to decrease significantly with increasing convection or activity, but the overall PV5/3 remains similar. The decrease of nV can be seen when convection increases during the same low activity, suggesting that a decrease of source particles, likely the cold particles from the flanks, may play an important role. We compared the variations of PV5/3 and nV along drift paths with the physical bases of ideal MHD and the Rice Convection Model (RCM). We found that PV5/3 drops significantly earthward along the estimated electric drift paths near midnight, indicating that it is far from the assumption d(PV5/3)/dt = 0 used in ideal MHD. Examination of PkV5/3 and the electric and magnetic drift paths of different energy invariants, where Pk is the partial pressure of a specific energy invariant, shows that the strong duskward drift of the above thermal-energy particles due to the magnetic drift, together with there being significantly fewer higher-energy particles from the dawn flank than from the tail, result in the strong earthward decrease of PV5/3. We also found that PkV5/3 does not change significantly along the electric and magnetic drift paths of particles with energies above the thermal-energy, indicating d(PkV5/3)/dt = 0 used in the RCM is a good approximation for the pressure-bearing plasma sheet ions. These comparisons show that the RCM physics can better account for large-scale plasma sheet thermodynamics.

  10. TOMOGRAPHY OF PLASMA FLOWS IN THE UPPER SOLAR CONVECTION ZONE USING TIME-DISTANCE INVERSION COMBINING RIDGE AND PHASE-SPEED FILTERING

    SciTech Connect

    Svanda, Michal, E-mail: michal@astronomie.cz [Astronomical Institute, Academy of Sciences of the Czech Republic (v. v. i.), Fricova 298, CZ-25165 Ondrejov (Czech Republic); Astronomical Institute, Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-18000 Prague 8 (Czech Republic)

    2013-09-20

    The consistency of time-distance inversions for horizontal components of the plasma flow on supergranular scales in the upper solar convection zone is checked by comparing the results derived using two k-{omega} filtering procedures-ridge filtering and phase-speed filtering-commonly used in time-distance helioseismology. I show that both approaches result in similar flow estimates when finite-frequency sensitivity kernels are used. I further demonstrate that the performance of the inversion improves (in terms of a simultaneously better averaging kernel and a lower noise level) when the two approaches are combined together in one inversion. Using the combined inversion, I invert for horizontal flows in the upper 10 Mm of the solar convection zone. The flows connected with supergranulation seem to be coherent only for the top {approx}5 Mm; deeper down there is a hint of change of the convection scales toward structures larger than supergranules.

  11. By-controlled convection and field-aligned currents near midnight auroral oval for northward interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Taguchi, S.; Sugiura, M.; Iyemori, T.; Winningham, J. D.; Slavin, J. A.

    1994-01-01

    Using the Dynamics Explorer (DE) 2 magnetic and electric field and plasma data, B(sub y)- controlled convection and field-aligned currents in the midnight sector for northward interplanetary magnetic field (IMF) are examined. The results of an analysis of the electric field data show that when IMF is stable and when its magnitude is large, a coherent B(sub y)-controlled convection exists near the midnight auroral oval in the ionosphere having adequate conductivities. When B(sub y) is negative, the convection consists of a westward (eastward) plasma flow at the lower latitudes and an eastward (westward) plasma flow at the higher latitudes in the midnight sector in the northern (southern) ionosphere. When B(sub y) is positive, the flow directions are reversed. The distribution of the field-aligned currents associated with the B(sub y)-controlled convection, in most cases, shows a three-sheet structure. In accordance with the convection the directions of the three sheets are dependent on the sign of B(sub y). The location of disappearance of the precipitating intense electrons having energies of a few keV is close to the convection reversal surface. However, the more detailed relationship between the electron precipitation boundary and the convection reversal surface depends on the case. In some cases the precipitating electrons extend beyond the convection reversal surface, and in others the poleward boundary terminates at a latitude lower than the reversal surface. Previous studies suggest that the poleward boundary of the electrons having energies of a few keV is not necessarily coincident with an open/closed bounary. Thus the open/closed boundary may be at a latitude higher than the poleward boundary of the electron precipitation, or it may be at a latitude lower than the poleward boundary of the electron precipitation. We discuss relationships between the open/closed boundary and the convection reversal surface. When as a possible choice we adopt a view that the open/closed boundary agrees with the convection reversal surface, we can explain qualitatively the configuration of the B(sub y)-controlled convection on the open and close field line regions by proposing a mapping modified in accordance with IMF B(sub y).

  12. The hot plasma environment and floating potentials of an electron-beam-emitting rocket in the ionosphere

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.; Winckler, J. R.

    1981-01-01

    The plasma environment surrounding the Echo III accelerator payload is examined with an extensive array of particle sensors. Suprathermal electrons are produced isotropically around the payload during the gun firings and decay away in approximately 32 ms. The largest directional intensities of this component are observed at the higher altitudes. Quick echo electrons are also observed to produce suprathermal electrons when they encounter the payload. The hot electrons surrounding the accelerator payload during gun injections bring sufficient charge to the payload to neutralize it provided the loss of charge by secondary production on the payload skin is small. Since the hot population exists for tens of milliseconds after the gun turnoff, it results in driving the payload up to 4 volts negative during this time. Quick echo electrons creating suprathermal electrons around the payload also drive the payload to a few volts negative.

  13. Topside high latitude ionospheric structures

    NASA Astrophysics Data System (ADS)

    Rothkaehl, Hanna; Przepióka, Dorota; Matyjasik, Barbara

    2015-04-01

    The radiations belts region can play a major role in the near Earth environment. Despite the fact that the analysis of properties of Earth electromagnetic environment has had a long history, the topics related to deeply understanding waves particles interaction in radiation belts region and in connecting ionosperic region are still not sufficiently understood. Particularly it seems that description of energy transfer in the ionosphere-magnetosphere coupling processes, can be a major task to solve in near future. By help the wave and plasma diagnostics located on board of past low orbiting satellites operated Demeter satellite and new RELEC mission the description of selected physical processes occurred in auroral region of topside ionosphere are reported. The aim of this presentation is to show the response of ionospheric plasma to the energetic particle fluxes coming from radiation belts region and describe the complex coupling processes of radiation belts region and low altitude near Earth radiation environment. The presented analysis can be very useful for constricting new operation models incorporated in Space Weather program.

  14. Convective Cell Formation in a Levitated Dipole Plasma Science and Fusion Center

    E-print Network

    to be superconducting and it would be magnetically levitated within the vacuum chamber. Since a large flux expansion that is levitated within a relatively large vacuum chamber. An initial test of this concept is embodied] is that in a plasma, stable modes will be excited by thermal fluctuations which, even in the absence of equilibrium

  15. Intermittent convective transport carried by propagating electromagnetic filamentary structures in nonuniformly magnetized plasma

    Microsoft Academic Search

    G. S. Xu; V. Naulin; W. Fundamenski; J. Juul Rasmussen; A. H. Nielsen; B. N. Wan

    2010-01-01

    Drift-Alfvén vortex filaments associated with electromagnetic turbulence were recently identified in reversed field pinch devices. Similar propagating filamentary structures were observed in the Earth magnetosheath, magnetospheric cusp and Saturn's magnetosheath by spacecrafts. The characteristics of these structures closely resemble those of the so-called mesoscale coherent structures, prevailing in fusion plasmas, known as ``blobs'' and ``edge localized mode filaments'' in the

  16. Emission of whistler waves from an ionospheric tether

    E-print Network

    Takiguchi, Yu

    2009-01-01

    In this thesis, we analyze how electromagnetic waves propagate in ionosphere around the earth which is magnetized plasma. We calculate the electromagnetic wave field made by a dipole antenna at an arbitrary observation ...

  17. Role of Mesoscale Convection in the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Sazykin, S. Y.; Wolf, R.; Yang, J.; Toffoletto, F.; Spiro, R. W.

    2014-12-01

    Transport through the Earth's plasma sheet and inner magnetosphere is a combination of global-scale convection and mesoscale processes such as flux-tube interchange associated with propagation of bursty bulk flows and dipolarization fronts. It is now clear that mesoscale processes play a significant role in plasma sheet transport on closed magnetic field lines; however, it is not clear if they play a dominant role. In this paper, we will describe initial steps in attempting quantitative modeling of flux-tube interchange processes using a high-resolution version of the Rice Convection Model (RCM) that includes effects of inertial drifts. In our approach, we make three simplifying assumptions: (i) the communication between the equatorial plane and ionosphere occurs either instantaneously or with a given time lag, (ii) the pressure is isotropic and therefore constant along field lines, and (iii) for purposes of calculating the effect of inertia, all of a flux tube's mass is assumed to be concentrated in the equatorial plane. We will present idealized numerical simulations of a depleted flux tube propagation in the magnetosphere and its particle signature as well as auroral consequences. We will also describe the sensitivity of the results to the assumptions made in the inclusion of the inertia effects. Finally, we address the minimum required spatial resolution needed to include the physics of flux-tube interchange processes while describing the global magnetospheric convection on closed field lines.

  18. The plasma environment of Uranus

    NASA Technical Reports Server (NTRS)

    Belcher, J. W.; Mcnutt, R. L., Jr.; Richardson, J. D.; Selesnick, R. S.; Sittler, E. C., Jr.; Bagenal, F.

    1991-01-01

    An overview of the observational results on the plasma environment at Uranus is given, and the implications of these observations for magnetospheric physics at Uranus are discussed. During the Voyager 2 encounter with Uranus, an extended magnetosphere filled with a tenuous plasma was detected. This low-energy plasma was found to consist of protons and electrons, with no significant heavy ion contribution, and with a density in the regions sampled by the spacecraft of at most three electrons per cubic centimeter. The plasma electrons and ions exhibit both a thermal component (with temperatures of tens of eV) and a hot component (with temperatures of a few keV). The thermal ion component is observed both inside and outside an L-shell value near 5, whereas the hot ion and electron component is excluded from the region inside of that L-shell. The source of the thermal component of the plasma is either the planetary ionosphere or the neutral hydrogen corona surrounding Uranus, whereas the hot component is convected in from the magnetotail, with probably an ionospheric source.

  19. Plasma irregularities in the duskside subauroral ionosphere as observed with midlatitude SuperDARN radar in Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Hosokawa, K.; Nishitani, N.

    2010-08-01

    We revealed the spatial distribution of HF radar echoes in the subauroral region by conducting a statistical analysis of scattering occurrence from the midlatitude Super Dual Auroral Radar Network (SuperDARN) radar in Hokkaido, Japan. Consequently, Dusk Scatter Event (DUSE) was identified as a most prominent backscatter target in these latitudes. Past studies have intended to associate an appearance of DUSE with the density gradient at the poleward or sunward edges of the midlatitude trough. However, exact spatial collocation between the source region of DUSE and the midlatitude trough has not been revealed because the SuperDARN radars in the auroral region could not observe the whole part of DUSE due to a limitation of the field-of-view coverage. Thus, it has been unclear which of the density gradients associated with the midlatitude trough is responsible for generating DUSE. The data from the Hokkaido radar enabled us to estimate the lower-latitude boundary of DUSE as around 59° in AACGM magnetic latitude. In addition, by adding the data from the King Salmon radar in Alaska we derived a complete statistical distribution of DUSE. The latitudinal extent of DUSE is about 9° from 59° to 68°, which is approximately 1000 km. The statistical distribution of DUSE was compared with the model of the midlatitude trough. As a result, the source region of DUSE is closely colocated with the minimum of the trough, which suggests that the electron density gradient at the sunward edge of the trough is responsible for DUSE. This means that the location of the duskside sunward edge (i.e., local time extent) of the midlatitude trough can be monitored by using an appearance of DUSE as a proxy. The current statistical analysis also suggests that we can derive a spatial distribution of HF radar echoes from the midlatitudes to high latitudes by combining the data from the Hokkaido and King Salmon radars located in the Far Eastern area, which would be a very powerful diagnostic tool for investigating the global distribution of plasma irregularities.

  20. Convective Raman amplification of light pulses causing kinetic inflation in inertial fusion plasmas

    SciTech Connect

    Ellis, I. N. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); University of California, Los Angeles, California 90095 (United States); Strozzi, D. J.; Williams, E. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Winjum, B. J.; Tsung, F. S.; Mori, W. B.; Fahlen, J. E. [University of California, Los Angeles, California 90095 (United States); Grismayer, T. [University of California, Los Angeles, California 90095 (United States); Grupo de Lasers e Plasmas, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal)

    2012-11-15

    We perform 1D particle-in-cell (PIC) simulations using OSIRIS, which model a short-duration ({approx}500{omega}{sub 0}{sup -1} FWHM) scattered light seed pulse in the presence of a constant counter-propagating pump laser with an intensity far below the absolute instability threshold. The seed undergoes linear convective Raman amplification and dominates over fluctuations due to particle discreteness. Our simulation results are in good agreement with results from a coupled-mode solver when we take into account special relativity and the use of finite size PIC simulation particles. We present linear gain spectra including both effects. Extending the PIC simulations past when the seed exits the simulation domain reveals bursts of large-amplitude scattering in many cases, which does not occur in simulations without the seed pulse. These bursts can have amplitudes several times greater than the amplified seed pulse, and we demonstrate that this large-amplitude scattering is the result of kinetic inflation by examining trapped particle orbits. This large-amplitude scattering is caused by the seed modifying the distribution function earlier in the simulation. We perform some simulations with longer duration seeds, which lead to parts of the seeds undergoing kinetic inflation and reaching amplitudes several times more than the steady-state linear theory results. Simulations with continuous seeds demonstrate that the onset of inflation depends on seed wavelength and incident intensity, and we observe oscillations in the reflectivity at a frequency equal to the difference between the seed frequency and the frequency at which the inflationary stimulated Raman scattering grows.

  1. Pre-onset auroral signatures and subsequent development of substorm auroras: a development of ionospheric loop currents at the onset latitudes

    NASA Astrophysics Data System (ADS)

    Saka, O.; Hayashi, K.; Thomsen, M.

    2014-08-01

    Substorm auroras observed on 17 January 1994 were localized within the field of view of an all-sky imager installed at Dawson City (DWS, 65.7° ILAT). In association with the enhancement of the anti-sunward convection in the polar cap and the ion flux enhancement in 1-6 keV at geosynchronous altitudes, a wave-like structure propagating equatorward to the onset latitudes with a high wave number in azimuth (m ~ 76, T ~ 120 s) was observed 30 min prior to the activation in the equatorward latitudes. The activation of the auroras in the equatorward latitudes and the subsequent poleward expansion lasted for approximately 6 min until a diffuse aurora formed. The auroras in the last 6 min were isolated and localized within the field of view of DWS, from 400 km west to 400 km east, and accompanied the magnetic pulse at the optical station. The magnetic pulse is interpreted by the propagating ionospheric current loop with a size comparable to the isolated auroras (~ 1000 km). We conclude that the wave-like structures in the pre-onset interval relate to the intrusion of the plasma-sheet plasmas from the tail by the convection. The plasmas from the tail eventually developed the ionospheric loop currents at the onset latitudes, in association with the triggering of the bead-like rippling of auroras and subsequent breaking out from the onset latitudes.

  2. The Harang discontinuity in auroral belt ionospheric currents.

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.

    1972-01-01

    Discussion of the nature of a discontinuity in the ionospheric current of the auroral belt whose existence was suggested by Harang in 1946. Convection characteristics, time variability, and current continuity in the auroral belt are considered in a context of observations and arguments supporting the reality of Harang's discontinuity.

  3. Multi-instrument observations of plasma features in the Arctic ionosphere during the main phase of a geomagnetic storm in December 2006

    NASA Astrophysics Data System (ADS)

    Wu, Ye-wen; Liu, Rui-yuan; Zhang, Bei-chen; Wu, Zhen-sen; Hu, Hong-qiao; Zhang, Shun-rong; Zhang, Qing-he; Liu, Jun-ming; Honary, F.

    2013-12-01

    Arctic ionospheric variations during the main phase of a magnetic storm on 14-15 December, 2006 were investigated to characterize the high energy particle precipitation caused effects, based on multi-instrument observations. These include electron density observations provided by the Global Positioning System (GPS) total electron content (TEC) measurements, European Incoherent Scatter (EISCAT) radar, the radio occultation (RO) from both the CHAMP satellite and the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellite, as well as the ionospheric absorption of cosmic radio noise measured by the Imaging Riometer for Ionospheric Studies (IRIS) at Kilpisjärvi in the northern Finland (69.05°N, 20.79°E). Significant increases in the electron density for these different observations were found in the Arctic ionosphere during the main phase of the magnetic storm. These increase occurred in Scandinavian, Northwest part of Russia and Svalbard (SNRS) region, primarily at an altitude of about 110 km. These results are first reported for the SNRS region, and our study contributes to a more complete description of this space weather event during 14-15 December, 2006. Our observations also provide direct evidence that the stormtime E-layer electron density enhancement (e.g., the sporadic E) can form a nearly dominant portion in the observed TEC increase. These increases were accompanied by the ionospheric absorption enhancement at the altitude of about 90 km. The Y-component of magnetic field to the south of SNRS decreased, indicating strong upward field aligned electric current in the Arctic ionosphere. These features are interpreted as the effect of the high energy electron precipitation during the magnetic storm, which is caused by the sub-storm reflected on AL index and the measurements of IMAGE (International Monitor for Auroral Geomagnetic Effects) chain. The average energy of the precipitation electrons reached to about 10 keV and the boundary of the high energy electron precipitation was also found to move poleward with a speed of about 800 m/s.

  4. Magnetosphere-Ionosphere Coupling Processes in the Ionospheric Trough Region During Substorms

    NASA Astrophysics Data System (ADS)

    Zou, S.; Moldwin, M.; Nicolls, M. J.; Ridley, A. J.; Coster, A. J.; Yizengaw, E.; Lyons, L. R.; Donovan, E.

    2013-12-01

    The ionospheric troughs are regions of remarkable electron density depression at the subauroral and auroral latitudes, and are categorized into the mid-latitude trough or high-latitude trough, depending on their relative location to the auroral oval. Substorms are one fundamental element of geomagnetic activity, during which structured field-aligned currents (FACs) and convection flows develop in the subauroral and auroral ionosphere. The auroral/trough region is expected to experience severe electron density variations during substorms. Accurate specification of the trough dynamics during substorms and understanding its relationship with the structured FACs and convection flows are of important practical purpose, including providing observational foundations for assessing the attendant impact on navigation and communication. In addition, troughs are important since they map to magnetospheric boundaries allowing the remote sensing of magnetosphere-ionosphere coupling processes. In this talk, we discuss the dynamics of the mid-latitude and high-latitude troughs during substorms based on multi-instrument observations. Using GPS total electron content (TEC) data, we characterize the location and width of the mid-latitude trough through the substorm lifecycle and compare them with existing trough empirical models. Using a combination of incoherent scattering radar (ISR), GPS TEC, auroral imager and a data assimilative model, we investigate the relationship between the high-latitude trough and FACs as well as convection flows. The high-latitude trough is found to be collocated with a counter-clockwise convection flow vortex east of the Harang reversal region, and downward FACs as part of the substorm current system are suggested to be responsible for the high-latitude trough formation. In addition, complex ionospheric electron temperature within the high-latitude trough is found, i.e., increase in the E region while decrease in the F region. We discuss possible processes responsible for this complex temperature change, such as ion composition change and/or presence of downward FACs.

  5. Observations of the artificially injected Porcupine xenon ion beam in the ionosphere

    Microsoft Academic Search

    B. Haeusler; R. A. Treumann; O. H. Bauer; G. Haerendel; R. Bush; C. W. Carlson; B. Theile; M. C. Kelley; V. S. Dokukin; Yu. Ya. Ruzhin

    1986-01-01

    Results are given of ion beam injection experiments performed in the auroral ionosphere in connection with the German Sounding Rocket Project Porcupine. A heavy (xenon) ion beam was injected into the collisionless ionospheric plasma approximately perpendicular to the ambient magnetic field at altitudes from 190 km to about 450 km. The beam propagates nearly undistorted across the plasma because it

  6. Ionospheric Instabilities and Shock Capturing Algorithms

    NASA Technical Reports Server (NTRS)

    Zalesak, Steven T.

    1998-01-01

    We describe the basic physics of the gradient-drift instability and the collisional Rayleigh-Taylor instability, the two plasma instabilities which dominate the production of small-scale structure in the earth's ionosphere. We then focus our attention on the nonlinear evolution of these instabilities for two particular cases: 1) the recursive bifurcation and "freezing" of artificial ion clouds released in the ionosphere; and 2) equatorial spread F. Finally, we discuss the numerical challenges faced in attempting to numerically simulate these instabilities, and the role played by shock-capturing algorithms therein.

  7. Global Ionospheric and Thermospheric Response to the April 2010 Geomagnetic Storm

    NASA Astrophysics Data System (ADS)

    Lu, G.; Haeusler, K.; Hagan, M. E.; Doornbos, E.; Bruinsma, S.; Forbes, J. M.; Zhang, X.; Ober, D. M.; Korth, H.; Anderson, B. J.; Ribeiro, A.; Ruohoniemi, J.

    2013-12-01

    We present a detailed case study of the 5 April 2010 geomagnetic storm. The event was prompted by a fast-moving coronal mass ejection from the Sun. Despite being a rather moderate storm with a minimum Dst value only around -70 nT, the event showcases some important yet complex ionospheric and thermospheric characteristics that are typically seen during major storms, including plasma density perturbations by penetration electric fields, strong equatorward neutral wind surges, and the development of westward disturbance dynamo winds. These storm-related features are examined in light of the NCAR Thermosphere-Ionosphere-Mesosphere Electrodynamic General Circulation Model (TIMEGCM) simulations. To replicate magnetospheric forcing during the event, time-dependent global patterns of ionospheric plasma convection and auroral energy dissipation obtained from the AMIE procedure were used to drive the TIMEGCM. AMIE synthesizes various data sets from both space- and ground-based instruments, including DMSP, AMPERE, and SuperDARN. This study was also motivated by the unprecedented thermospheric observations available from the GOCE, CHAMP, and GRACE satellites, which were operating at average altitudes of 270, 300, and 470 km, and covering local time sectors at 6:20-18:20 LT, 12:00-24:00 LT, and 8:30-20:30 LT, respectively. The emphasis of the paper is placed on the inter-comparison of the simulation results with satellite and other ground-based measurements in order to unveil the physical processes responsible for the observed latitudinal and longitudinal/local-time variations from high latitudes to the equatorial regions.

  8. Plasma Interactions in Titan's Ionosphere

    E-print Network

    Richard, Matthew

    2013-05-31

    proven to reproduce accurate profiles of ion production and temperature, ion production profiles will be generated using solar photons and magnetospheric electron fluxes for four canonical cases detailed in the work of Rymer et al. [2009] and a globally...

  9. Solar wind interaction with the ionosphere of Venus inferred from radio scintillation measurements

    SciTech Connect

    Woo, R.; Sjogren, W.L.; Kliore, A.J. (California Institute of Technology, Pasadena (USA)); Luhmann, J.G. (Univ. of California, Los Angeles (USA)); Brace, L.H. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

    1989-02-01

    This paper presents the first S-band (2.3 GHz) radio scintillations observed in the ionosphere of Venus and discovered when the Pioneer Venus Orbiter spacecraft traversed the ionosphere of Venus. In situ plasma measurements as well as propagation calculations confirm that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. While these topside plasma irregularities have not been studied before, simultaneous magnetic field measurements presented here reveal that they are associated with the penetration of large-scale magnetic fields in the ionosphere. Previous studies based on extensive magnetic field measurements have shown that the presence of large-scale magnetic fields occurs in the subsolar region when the solar wind dynamic pressure exceeds the ionospheric plasma pressure. As with the large-scale magnetic fields, the disturbed plasma and resulting scintillations are therefore a manifestation of high-dynamic solar wind interaction with the ionosphere. Since the scintillations only occur in the subsolar region of Venus, the global morphology of ionospheric scintillations at Venus is different from that of the terrestrial ionosphere, where scintillations are observed in both polar and equatorial regions, with peaks occurring during nighttime. This difference apparently stems from the fact that Venus is not a magnetic planet. The authors also demonstrate that the disturbed plasma produced by the high-dynamic solar wind interaction can be remotely sensed by scintillations during radio occultation measurements, that is, when the spacecraft is outside the ionosphere.

  10. GPS and ionospheric scintillations

    Microsoft Academic Search

    P. M. Kintner; B. M. Ledvina; E. R. de Paula

    2007-01-01

    Ionospheric scintillations are one of the earliest known effects of space weather. Caused by ionization density irregularities, scintillating signals change phase unexpectedly and vary rapidly in amplitude. GPS signals are vulnerable to ionospheric irregularities and scintillate with amplitude variations exceeding 20 dB. GPS is a weak signal system and scintillations can interrupt or degrade GPS receiver operation. For individual signals,

  11. Dispersive ionospheric Alfvén resonator

    Microsoft Academic Search

    Oleg A. Pokhotelov; D. Pokhotelov; A. Streltsov; V. Khruschev; M. Parrot

    2000-01-01

    A new model of the ionospheric Alfvén resonator (IAR) including the effect of wave frequency dispersion is presented. It is shown that the shear Alfvén waves in the IAR are coupled to the compressional mode through the boundary conditions at the ionosphere. This coupling results in the appearance of the Hall dispersion and subsequent shift of the IAR frequency spectrum.

  12. Characteristics of High Latitude Ionosphere Scintillations

    NASA Astrophysics Data System (ADS)

    Morton, Y.

    2012-12-01

    As we enter a new solar maximum period, global navigation satellite systems (GNSS) receivers, especially the ones operating in high latitude and equatorial regions, are facing an increasing threat from ionosphere scintillations. The increased solar activities, however, also offer a great opportunity to collect scintillation data to characterize scintillation signal parameters and ionosphere irregularities. While there are numerous GPS receivers deployed around the globe to monitor ionosphere scintillations, most of them are commercial receivers whose signal processing mechanisms are not designed to operate under ionosphere scintillation. As a result, they may distort scintillation signal parameters or lose lock of satellite signals under strong scintillations. Since 2008, we have established and continuously improved a unique GNSS receiver array at HAARP, Alaska. The array contains high ends commercial receivers and custom RF front ends which can be automatically triggered to collect high quality GPS and GLONASS satellite signals during controlled heating experiments and natural scintillation events. Custom designed receiver signal tracking algorithms aim to preserve true scintillation signatures are used to process the raw RF samples. Signal strength, carrier phase, and relative TEC measurements generated by the receiver array since its inception have been analyzed to characterize high latitude scintillation phenomena. Daily, seasonal, and solar events dependency of scintillation occurrence, spectral contents of scintillation activities, and plasma drifts derived from these measurements will be presented. These interesting results demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations and natural disturbances.

  13. Electrostatic potential in the auroral ionosphere derived from Chatanika radar observations

    SciTech Connect

    Foster, J.C.; Banks, P.M.; Doupnik, J.R.

    1982-09-01

    A technique is described for determining the latitudinal variation of the electrostatic potential associated with the ionospheric convection electric fields. Using the north-south electric field component derived from radar convection velocity experiments, the integral of Exd1 is taken northward along the magnetic meridian, starting at low latitudes. The radar data consiste of up to 40 independent measurements of plasma convection spanning 15/sup 0/ of invariant latitude centered on Chatanika, Alaska (65 /sup 0/..lambda..), with half-hour temporal resolution. It has been found that (1) the electric field contributions to the potential at and below 60 /sup 0/..lambda.. are small under most circumstances and (2) the latitudinal variation of the potential is smooth and regular, permitting the potentials to be contoured across local time. It is found from the experiments that the potential often varies uniformly over 10 /sup 0/ latitude at dawn and dusk. Electric fields of 50 mV/m are common. It is also noted that the latitude of the greatest negative potential in the premidnight sector coincides with the Harang discontinuity in ionspheric currents. The potentials calculated from the measured plasma drifts exhibit a regular local time variation. Equipotential contours derived from the latitude-local time potential field obtained with the long-duration radar experiments, while not providing a snapshot of the instantaneous pattern, elucidate the large-scale diurnal variation of the electrostatic potential at auroral latitudes. From such contours it is found that a two-cell convection pattern with varying degrees of asymmetry is consistently present at auroral latitudes, that a cross-polar cap potential drop of 70--120 kV is present in moderately disturbed conditions, and that substorms perturb the potential pattern at all local times.

  14. Dayside convection and auroral morphology during an interval of northward interplanetary magnetic eld

    E-print Network

    Boyer, Edmond

    Dayside convection and auroral morphology during an interval of northward interplanetary magnetic and ionospheric convection during an interval when the interplanetary magnetic ®eld (IMF) had predominantly radar. For an interval of IMF By 0 nT, these convection ¯ow measurements suggest the presence

  15. Energetic particle precipitation into the high-latitude ionosphere and the auroral electrojets. 3. Characteristics of electron precipitation into the morning-sector auroral oval

    SciTech Connect

    Rostoker, G.; Kamide, Y.; Winningham, J.D.

    1985-08-01

    Data from the University of Alberta meridian line of magnetometers are utilized to define the poleward and equatorward borders of the westward electrojet in the morning sector. Soft-particle spectrometer data from the Isis 2 polar orbiting satellite are organized in the framework of the westward electrojet for cases where the satellite orbital path took it close to the meridian line of magnetometers. The results suggest that the Harang discontinuity does not signify any significant asymmetry in convection drift paths in the magnetosphere and that asymmetries noted in ionospheric current flow and auroral luminosity are due solely to asymmetries in the energies to which electrons may be accelerated in the morning compared to the evening sector. A model of plasma convective flow in the magnetosphere is presented which is consistent with the observations reported in this paper.

  16. Studying the Space Weather Features of the High-Latitude Ionosphere by Using a Physics-Based Data Assimilation Model and Observational Data from Ground Magnetometer Arrays

    NASA Astrophysics Data System (ADS)

    Zhu, L.; Schunk, R. W.; Scherliess, L.; Sojka, J. J.; Eccles, J. V.

    2011-12-01

    The high-latitude ionosphere is a very dynamic region in the solar-terrestrial environment. Frequent disturbances in the region can adversely affect numerous military and civilian technologies. Accurate specifications and forecasts of the high-latitude electrodynamic and plasma structures have fundamental space weather importance for enabling mitigation of adverse effects. Presently, most of the space-weather models use limited observations and/or indices to define a set of empirical drivers for physical models to move forward in time. Since the empirical drivers have a "climatological" nature and there are significant physical inconsistencies among various empirical drivers due to independent statistical analysis of different observational data, the specifications of high-latitude space environment from these space weather models cannot truthfully reflect the weather features. In fact, unrealistic small- and large-scale structures could be produced in the specifications and forecasts from these models. We developed a data assimilation model for the high-latitude ionospheric plasma dynamics and electrodynamics to overcome these hurdles. With a set of physical models and an ensemble Kalman filter, the data assimilation model can determine the self-consistent structures of the high-latitude convection electric field, ionospheric conductivity, and the key drivers associated with these quantities by ingesting data from multiple observations. These ingested data include the magnetic perturbation from the ground-based magnetometers in the high-latitude regions, magnetic measurements of IRIDIUM satellites, SuperDARN line-of-sight velocity, and in-situ drift velocity measured by DMSP satellites. As a result, the assimilation model can capture the small- and large-scale plasma structures and sharp electrodynamic boundaries, thus, can provide a more accurate picture of the high-latitude space weather. In this presentation, we will first briefly describe the data-assimilation model of high-latitude electrodynamics and its strengths over the other space-weather models. Then we will present the space weather features produced by the model for quiet and storm periods constrained by the data from ground magnetometer arrays. This will demonstrate the dynamic variability of the high-latitude ionosphere. Finally, we will present high-resolution ionospheric modeling results of the time-evolution and spatial features of the high-latitude plasma structures to further demonstrate the model's capability in producing the space weather features in the high-latitude ionosphere. These results will illuminate the importance of real-time data availability and data assimilation models for accurate specification and forecasting of space weather.

  17. Evidence of Medium Scale (~50 km) Undulations Observed at Sunset in the Equatorial Ionosphere by Electric Field and Plasma Density Probes on the C/NOFS Satellite Below the F-Peak in Conjunction with Larger Scale (~500 km) Depletions

    NASA Astrophysics Data System (ADS)

    Pfaff, R. F., Jr.; Freudenreich, H. T.; Klenzing, J.; Liebrecht, M. C.

    2014-12-01

    Electric field and plasma density observations gathered on the C/NOFS satellite are presented in cases where the ionosphere F-peak has been elevated above the satellite perigee of 400 km near sunset. During these passes, data from the electric field and plasma density probes on the satellite frequently show evidence of "medium scale" (40-80 km) undulations in conjunction with, yet distinct from, series of periodic, larger scale (200-800 km) density depletions. The observations suggest that a second category of wavelike variations of the bottomside plasma density may be important for the subsequent development of the larger scale density depletions and their associated "spread-F" irregularities. The electric fields associated with the medium scale undulations are typically a few mV/m with density variations of a few percent in which upwards E x B drifts are associated with their depletions. The undulations are observed both before and after local sunset and are typically observed, in the satellite frame as it journeys from west to east, prior to the onset of the larger scale depletions. We present examples of these medium scale undulations and discuss their implications for driving the larger scale depletions, possibly in a manner similar to that discussed by Hysell and Kudeki [2004], Kudeki et al. [2007], and others.

  18. Bubble phenomenon in the topside ionosphere

    NASA Astrophysics Data System (ADS)

    Sidorova, L.

    There are the indications that plasma bubbles produced by Rayleigh-Taylor instability at the bottomside of ionosphere could rise up to the topside ionosphere and plasmasphere Maryama and Matuura 1984 using ISS-b satellite data high solar activity period 1978-79 have seen the plasma bubbles in Ne density over equator at 1100 km altitudes in 46 cases in 1700 passes That is sim 3 only However there is distinctly another picture in He density depletions subtroughs According to ISS-b data He density subtroughs occur in the topside ionosphere over equatorial and low-latitudinal regions L sim 1 3-3 in 11 of the cases Karpachev Sidorova 2002 Sidorova 2004 The detailed statistical study of the He density subtrough peculiarities was done The subtrough depth depletion value as function of local time evening--night hours was compared with the vertical plasma drift velocity variations obtained for the same periods from AE-E satellite and IS radar Jicamarca data Striking similarity in development dynamics was revealed for the different seasons It was noted also that the He density subtroughs are mostly observed in the evening-night sector 18-05 LT from October till May It was like to the peculiarities of the equatorial spread-F ESF usually associated with plasma bubble The monthly mean He density subtrough occurrence probability plotted in local time versus month was compared with the similar plots for ESF occurrence probability derived by Abdu and colleagues 2000 from

  19. Preliminary results of modification of the ionospheric plasma by high-power radio emission from the Sura facility as observed on board the Russian Segment of the International Space Station

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Vladimir; Ruzhin, Yu. Ya.; Karabadzhak, G. F.; Plastinin, Yu. A.; Khmelinin, B. A.; Frolov, V. L.; Komrakov, G. P.

    Considered are the results of the experiment on modification of the ionosphere by high-power radio emission from the Sura heating facility carried out on October 2, 2007 at 18:40 UT. The modification effects were observed on board the Russian Segment of the International Space Station (RS ISS). The mid-latitude (56.13N, 46.1E) heating facility Sura makes it possible to carry out plasma investigations in the ionosphere outside the highly dynamic auroral zone. In the experiment under discussion, the facility was working during 20 min in the mode of periodic heating (meander with a period of 2 min) at the frequency of 4.30 MHz. The effective emission power was 10 MW. The modulation frequency was 80 mHz, which was close to the frequency of natural Alfven oscillations of plasma in the magnetic flux tube resting on the heated spot in the ionosphere. The RS ISS observations with an optical TV camera have provided more than 1000 images of a bright local glow, which appeared within the field of view of the camera as the Space Station was passing over the location of the Sura facility. The least distance from the ISS to Sura was about 600 km. The brightness of the glow reached tens of kilorayleighs. The glow region appeared Northeast of the heating facility (150-200 km) and was moving East in the image plane. This picture was observed against the quiet background luminosity of the emission layer and auroral oval both before and after the passage over the Sura region. The glow disappeared when the heating stopped. The analysis of helio-geophysical conditions did not reveal any significant anomalies during the experiment. According to the INTERMAGNET network data, the planetary index of magnetic activity did not exceed 3, the auroral oval was quiet, noticeable variations in the solar wind and interplanetary magnetic field were absent (data from GOES, SOHO, etc.) A low power of the heating emission and high intensity of the glow observed suggest that the glow wasn't due directly to heating, but rather might be caused by the particle precipitation stimulated by the heating effects, such as modification of the integral conductance in the spot of the ionospheric plasma over the heating zone, which forms the base of the magnetic flux tube (and the standing wave node) and whose natural Alfven oscillations have a period close to the modulation period of the heating emission. The Alfven oscillations in the magnetic tube could be intensified during the experiment by a short (less than 1 min) and weak (amplitude of about 2 nT) pulse in the planetary geomagnetic field that occurred at 18:47:30 UT.

  20. Magnetopause Reconnection Rate and Cold Plasma: A Study using SuperDARN

    NASA Astrophysics Data System (ADS)

    Lester, M.; Imber, S. M.; Milan, S. E.; Denton, M. H.; Borovsky, J. E.

    2009-12-01

    There is evidence that cold plasma associated with cold dense plasma plumes from the plasmasphere can decrease the reconnection rate at the magnetopause as the cold plasma convects towards the magnetopause. This is a system level problem as the rate at which flux is reconnected determines the flux content of the polar cap and hence the tail lobes, and could be important for controlling subsequent night time magnetospheric dynamics. Further the cold plasma from the plasmasphere has to reach the magnetopause and this happens as a consequence of the dynamics of the magnetosphere. This paper reports a study using SuperDARN of the convection flows in the ionosphere which are generated by the reconnection at the magnetopause and therefore are a direct measure of the reconnection rate. Northern hemisphere SuperDARN data are used in this study and we concentrate on intervals when there is data coverage in the local time sector 0900 to 1500 MLT. This ensures that we have complete flow measurements in that sector. Cold plasma density are taken from LANL measurements and have been sued in earlier studies of the impact of cold plasma on the reconnection rates. Initial results indicate a smaller impact on the ionospheric measurements than on the magnetic indices as in the earlier study.

  1. Solar activity dependence of the topside ionosphere at low latitudes

    Microsoft Academic Search

    Yiding Chen; Libo Liu; Weixing Wan; Xinan Yue; Shin-Yi Su

    2009-01-01

    We investigated the solar activity dependence of the topside ionosphere with ROCSAT-1 observations. The distribution of the plasma density at 600 km altitude shows features with considerable local time, season, and solar activity differences. In the daytime, plasma density peaks around the dip equator. This peak is more distinct in equinoxes and weaker in May–July, and it enhances with solar

  2. Observations of self-focusing electromagnetic waves in the ionosphere

    Microsoft Academic Search

    L.M. Duncan; R. A. Behnke

    1978-01-01

    Self-focusing of high-frequency electromagnetic radiation is observed to produce large-scale plasma striations in the ionosphere. Development of a new observational technique has allowed the first detailed study of the instability scale sizes and associated plasma movement. Experimental results are shown to support the theory of wave self-focusing through differential electron heating.

  3. Experimental evidence of electromagnetic pollution of ionosphere

    NASA Astrophysics Data System (ADS)

    Pronenko, Vira; Korepanov, Valery; Dudkin, Denis

    The Earth’s ionosphere responds to external perturbations originated mainly in the Sun, which is the primary driver of the space weather (SW). But solar activity influences on the ionosphere and the Earth's atmosphere (i.e., the energy transfer in the direction of the Sun-magnetosphere-ionosphere-atmosphere-surface of the Earth), though important, is not a unique factor affecting its state - there is also a significant impact of the powerful natural and anthropogenic processes, which occur on the Earth’s surface and propagating in opposite direction along the Earth’s surface-atmosphere-ionosphere-magnetosphere chain. Numerous experimental data confirm that the powerful sources and consumers of electrical energy (radio transmitters, power plants, power lines and industrial objects) cause different ionospheric phenomena, for example, changes of the electromagnetic (EM) field and plasma in the ionosphere, and affect on the state of the Earth atmosphere. Anthropogenic EM effects in the ionosphere are already observed by the scientific satellites and the consequences of their impact on the ionosphere are not currently known. Therefore, it is very important and urgent task to conduct the statistically significant research of the ionospheric parameters variations due to the influence of the powerful man-made factors, primarily owing to substantial increase of the EM energy production. Naturally, the satellite monitoring of the ionosphere and magnetosphere in the frequency range from tens of hertz to tens of MHz with wide ground support offers the best opportunity to observe the EM energy release, both in the global and local scales. Parasitic EM radiation from the power supply lines, when entering the ionosphere-magnetosphere system, might have an impact on the electron population in the radiation belt. Its interaction with trapped particles will change their energy and pitch angles; as a result particle precipitations might occur. Observations of EM emission by multiple low orbiting satellites have confirmed a significant increase in their intensity over the populated areas of Europe and Asia. Recently, there are many experimental evidences of the existence of power line harmonic radiation (PLHR) in the ionosphere. Their spectra consist of succession of 50 (60) Hz harmonics which is accompanied by a set of lines separated by 50 (60) or 100 (120) Hz - the central frequency of which is shifted to high frequency. These lines cover rather wide band - according to the available experimental data, their central frequencies are observed from ~1.5 - 3 kHz up to 15 kHz, and recently the main mains frequencies are also observed. The examples of power line harmonic radiation, which were detected by “Sich-1M”, “Chibis-M” and “Demeter” satellites, have been presented and discussed. The available experimental data, as well as theoretical estimations, allow us with a high degree of certainty to say that the permanent satellite monitoring of the ionospheric and magnetospheric anthropogenic EM perturbations is necessary for: a) objective assessment and prediction of the space weather conditions; b) evaluation of the daily or seasonal changes in the level of energy consumption; c) construction of a map for estimation of near space EM pollution. This study is partially supported by SSAU contract N 4-03/13.

  4. Artificial periodic irregularities in the lower ionosphere, atmospheric waves and sporadic E-layer

    Microsoft Academic Search

    Nataliya V. Bakhmetieva; M. N. Egerev; A. V. Tolmacheva; V. D. Vyakhirev

    2010-01-01

    The long-term researches have shown that artificial periodic irregularities (API) created in the ionosphere plasma are a good means for the ionosphere diagnostics. In the report we present the new applications of the API technique for experimental studies of the lower ionosphere, atmospheric waves and sporadic E-layers. The applications are based on the new so-called two-frequency method of the API

  5. Substorm Onset by Plasma Sheet Divergence

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Wang, C.; Nagai, T.

    2003-12-01

    It is necessary to understand current wedge formation in order to understand the cause of the substorm expansion phase. Geotail spacecraft observations have shown that the inner-plasma-sheet cross-tail current reduction within the current wedge results from a process that leads to a reduction in equatorial plasma pressure and a substantial reduction in flux tube ion content. We use the single-species continuity equation for plasma sheet particles to identify a plausible cause of these plasma reductions. We find that a convection reduction, which follows a growth phase period of enhanced convection, should cause a divergence of plasma sheet particles driven by diamagnetic drift that leads to flux tube content reduction. Such reduction in flux tube content is longitudinally localized to the pre-midnight to midnight region where the current wedge has been observed to initially form and must initiate within the region of the equatorial mapping of the Harang discontinuity, consistent with ionospheric observations of substorm onset. We also find that the reduction in flux tube content should initially develop slowly, and then develop more rapidly as the current wedge forms. This is consistent with observations which show that expansion phase aurora, and thus also the current wedge, develops slowly for a few minutes before brightening rapidly, and it is as required if plasma sheet divergence driven by diamagnetic drift leads to current wedge formation and initiation of the substorm expansion phase.

  6. Survey of the ionospheric disturbances related with large seismic events in multi-satellite ionospheric observations

    NASA Astrophysics Data System (ADS)

    Ryu, K.; Chae, J.; Lee, E.; Kil, H.

    2013-12-01

    We survey the ionospheric disturbances in the plasma and electro-magnetic wave measurements during the simultaneous observation period of DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions), CHAMP (CHAllenging Minisatellite Payload) and DMSP(Defense Meteorological Satellite Program) missions. The multi-satellite observation around three large earthquakes that occurred between 2004 and 2005 were investigated. The observational evidences of the earth-quake precursory phenomena and the recent progress of physical modeling of the ionospheric disturbances caused by the coupling of the stressed rock, Earth surface charges, atmosphere, and ionosphere system are reviewed. Then, we focus on identifying the precursory disturbances from the well-studied plasma disturbances in the ionosphere, which are known to originate from various physical mechanism other than the seismic activities. Electron density/temperature, ion density/temperature, and electro-magnetic field/wave data measured by various instruments equipped in the satellites were analyzed in finding specific examples of anomaly caused by large seismic activities. Finally, the possibility of forecasting or predicting large earthquakes using the plasma measurements of LEO (low earth orbit) satellites will be discussed.

  7. The upper ionospheres of Jupiter and Saturn

    NASA Technical Reports Server (NTRS)

    Majeed, Tariq; Mcconnell, John C.

    1991-01-01

    The electron-density profiles of Jupiter's and Saturn's ionospheres are modeled with a 1D chemical diffusive model incorporating measured parameters of the neutral atmospheric structure. The Voyager RSS ion-density data are modeled by accounting for ion chemistry, the H3(+) recombination-rate coefficient, and H2O chemistry. Electron-density peaks for both ionospheres are 900-1000 km lower in the model than the measured values, and the role of vibrational excitation of H2 is discussed in converting H(+) to H2(+) and H3(+). Vertical ion flow is also considered which can maintain the plasma peaks under the conditions of electrical fields or horizontal neutral winds. An assumed influx of H2O molecules of a specific quantity is theorized to reproduce the measured values on Saturn when combined with a vertical plasma drift.

  8. Application of ionospheric topside-sounding results to magnetospheric physics and astrophysics

    Microsoft Academic Search

    Robert F. Benson; Vladimir A. Osherovich

    2004-01-01

    A brief review is presented to illustrate how the knowledge and experience gained from investigations of ionospheric topside-sounder ionograms has benefited scientific research beyond the ionosphere. In particular, to the interpretation of (1) natural radio emissions from space plasmas, (2) sounder-stimulated echoes and plasma emissions, and plasma diagnostics in planetary magnetospheres and (3) X-ray spectra of disks around neutron stars

  9. Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation)

    NASA Technical Reports Server (NTRS)

    Tan, A.

    1990-01-01

    The geomagnetic control of the Earth's atmosphere is well understood. In the F-region and the topside ionosphere, non-electrical forces transport plasma along the magnetic field lines only. In consequence, the worldwide distribution of ionization is strongly dependent on the dip angle. For example, the equatorial anomaly is roughly symmetrical about the dipole equator rather than the geographic. The same appears to be the case in the Jovian ionosphere (Mahajan, 1981). The influence of the magnetic field of Jupiter on its ionization pattern is one of several outstanding topics which need to be studied. Tan (1986) investigated the formation of the equatorial anomaly in the Jovian ionosphere under a centered dipole model. Tan (1988) further studied the effect of the tilt of the Jovian dipole. The results were in broad agreement with those of a diffusive equilibrium model (Tan and Wu, 1981). An off-centered dipole model is constructed and its effects on the ionization pattern are investigated.

  10. Tsunami Ionospheric warning and Ionospheric seismology

    NASA Astrophysics Data System (ADS)

    Lognonne, Philippe; Rolland, Lucie; Rakoto, Virgile; Coisson, Pierdavide; Occhipinti, Giovanni; Larmat, Carene; Walwer, Damien; Astafyeva, Elvira; Hebert, Helene; Okal, Emile; Makela, Jonathan

    2014-05-01

    The last decade demonstrated that seismic waves and tsunamis are coupled to the ionosphere. Observations of Total Electron Content (TEC) and airglow perturbations of unique quality and amplitude were made during the Tohoku, 2011 giant Japan quake, and observations of much lower tsunamis down to a few cm in sea uplift are now routinely done, including for the Kuril 2006, Samoa 2009, Chili 2010, Haida Gwai 2012 tsunamis. This new branch of seismology is now mature enough to tackle the new challenge associated to the inversion of these data, with either the goal to provide from these data maps or profile of the earth surface vertical displacement (and therefore crucial information for tsunami warning system) or inversion, with ground and ionospheric data set, of the various parameters (atmospheric sound speed, viscosity, collision frequencies) controlling the coupling between the surface, lower atmosphere and the ionosphere. We first present the state of the art in the modeling of the tsunami-atmospheric coupling, including in terms of slight perturbation in the tsunami phase and group velocity and dependance of the coupling strength with local time, ocean depth and season. We then show the confrontation of modelled signals with observations. For tsunami, this is made with the different type of measurement having proven ionospheric tsunami detection over the last 5 years (ground and space GPS, Airglow), while we focus on GPS and GOCE observation for seismic waves. These observation systems allowed to track the propagation of the signal from the ground (with GPS and seismometers) to the neutral atmosphere (with infrasound sensors and GOCE drag measurement) to the ionosphere (with GPS TEC and airglow among other ionospheric sounding techniques). Modelling with different techniques (normal modes, spectral element methods, finite differences) are used and shown. While the fits of the waveform are generally very good, we analyse the differences and draw direction of future studies and improvements, enabling the integration of lateral variations of the solid earth, bathymetry or atmosphere, finite model sources, non-linearity of the waves and better attenuation and coupling processes. All these effects are revealed by phase or amplitude discrepancies in selected observations. We then present goals and first results of source inversions, with a focus on estimations of the sea level uplift location and amplitude, either by using GPS networks close from the epicentre or, for tsunamis, GPS of the Hawaii Islands.

  11. Inertial currents in isotropic plasma

    NASA Technical Reports Server (NTRS)

    Heinemann, M.; Erickson, G. M.; Pontius, D. H., Jr.

    1994-01-01

    The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasmas, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, MHD plasma. Solutions are developed by taking the MHD limit ot two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

  12. Sputnik 1 and the First Satellite Ionospheric Experiment

    NASA Astrophysics Data System (ADS)

    Sinelnikov, Vyacheslav; Kuznetsov, Vladimir; Alpert, Svetlana

    The world's first scientific space experiment was carried out in 1957 during the flight of the first Artificial Earth Satellite (AES) - Sputnik 1. It was an ionospheric experiment performed at IZMIRAN under the direction of Prof. Ya.L.Alpert (1911-2010). The sunrise and sunset variations in the AES radio signal were recorded in order to determine the distribution of electron density in the topside ionosphere (above the maximum). The experiment demonstrated the capabilities of the satellite radio beacon method, which is now very important and widely used for studying the ionosphere. Our report submitted to the COSPAR General Assembly in Russia describes the history and results of that experiment, as well as some other contributions by Ya.L.Alpert to ionospheric research. Yakov L.Alpert was one of the most famous and influential radiophysicists of his time, the author of many fundamental studies and of a number of classic books on the theory of propagation of electromagnetic waves, interaction of artificial bodies with ionospheric plasmas, ionospheric radio scattering, and the use of satellite radio beacon methods for studying the ionosphere.

  13. Yakov Alpert: Sputnik-1 and the first satellite ionospheric experiment

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. D.; Sinelnikov, V. M.; Alpert, S. N.

    2015-06-01

    The world first scientific space experiment was carried out in 1957 during the flight of the First Artificial Earth Satellite (AES) - Sputnik-1. It was an ionospheric experiment performed at IZMIRAN under the direction of Prof. Ya.L. Alpert (1911-2010). The sunrise and sunset variations in the AES radio signal were recorded to determine the distribution of electron density in the topside ionosphere (above the maximum). The experiment demonstrated the capabilities of the satellite radio beacon method, which is now very important and widely used for studying the ionosphere. The paper describes the history and results of that experiment as well as the contribution of Ya.L. Alpert to ionospheric research. Ya.L. Alpert was one of the most famous and influential radiophysicists, the author of many fundamental studies and a number of classic books on the theory of propagation of electromagnetic waves, interaction of artificial bodies with ionospheric plasma, ionospheric radio scattering, and the use of satellite radio beacon methods for studying the ionosphere. We give in the paper some extracts from Ya.L. Alpert's research notes. They include the history of the publication of the results from recordings of the Sputnik-1 transmitter signals, and described the method of data analysis. The first scientific publication based on Sputnik-1 data is given in the abbreviated summary. At the end of the paper there is an outline of Ya.L. Alpert's scientific biography.

  14. Low-latitude ionosphere dynamics as deduced from meridional ionosonde chain: Ionospheric ceiling

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Uemoto, Junpei; Tsugawa, Takuya; Supnithi, Pornchai; Ishii, Mamoru; Komolmis, Tharadol

    Interest in the equatorial anomaly in the ionosphere has been focused mostly on f_oF_2, and not much attention was paid to h_mF_2 except for the time rate of change of it in connection with the vertical plasma drift velocity. There have been few climatological studies on h_mF_2 variations associated with development of the equatorial anomaly. In this paper, we revisit the equatorial anomaly in terms of height variations. For this purpose, we analyzed scaled ionogram parameters from three stations located along the magnetic meridian that is a primary component of Southeast Asia low-latitude ionospheric network (SEALION); one at the magnetic equator and the others at conjugate off-equatorial latitudes near 10 degrees magnetic latitude. The daytime h_mF_2 was investigated for each season during the solar minimum period, 2006-2007 and 2009. The peak height increased for approximately 3 hr after sunrise at all locations, as expected from the daytime upward E×B drift. The apparent upward drift ceased before noon at the magnetic equator, while the layer continued to increase at the off-equatorial latitudes, reaching altitudes higher than the equatorial height around noon. The noon time restricted layer height at the magnetic equator did not depend much on the season, while the maximum peak height at the off-equatorial latitudes largely varied with season. The daytime specific limiting height of the equatorial ionosphere was termed ionospheric ceiling. Numerical modeling using the SAMI2 code reproduced the features of the ionospheric ceiling quite well. Dynamic parameters provided by the SAMI2 modeling were investigated and it was shown that the ionospheric ceiling is another aspect of the fountain effect, in which increased diffusion of plasma at higher altitudes has a leading role.

  15. Structure of the ionospheric disturbances about planetary entry probes

    NASA Technical Reports Server (NTRS)

    Weil, H.; Jew, H.; Samir, U.

    1973-01-01

    Local ionospheric disturbances which would be created by a planetary entry probe are investigated. Competing theories of spacecraft-ambient plasma interactions are used to estimate computationally the perturbations of the plasma, particularly the structure of the near wake behind planetary entry vehicles. The results have bearing on the location and operation of plasma diagnostic instrumentation aboard planetary entry vehicles. Recent estimates of Mars ionospheric properties plus vehicle dimensions and speeds similar to those of the Viking Mars Lander are used to define the parameters essential to the theory. Smaller entry bodies are also considered. Comparisons are made of the results based on the different theories for a given assumed planetary atmosphere, and also with the perturbations a similar vehicle would generate in the earth's ionosphere.

  16. Convection in Neptune's magnetosphere

    NASA Technical Reports Server (NTRS)

    Hill, T. W.; Dessler, A. J.

    1990-01-01

    It is assumed that nonthermal escape from Triton's atmosphere produces a co-orbiting torus of unionized gas (presumably nitrogen and hydrogen) that subsequently becomes ionized by electron impact to populate a partial Triton plasma torus analogous to the Io plasma torus in Jupiter's magnetosphere. Centrifugal and magnetic-mirror forces confine the ions to a plasma sheet located between the magnetic and centrifugal equators. The ionization rate, and hence the torus ion concentration, is strongly peaked at the two points (approximately 180 deg apart in longitude) at which Triton's orbit intersects the plasma equator. During the course of Neptune's rotation these intersection points trace out two arcs roughly 75 deg in longitudinal extent, which we take to be the configuration of the resulting (partial) plasma torus. The implied partial ring currents produce a quadrupolar (four-cell) convection system that provides rapid outward transport of plasma from the arcs. Ring-current shielding, however, prevents this convection system from penetrating very far inside the plasma-arc distance. It is suggested that this convection/shielding process accounts for the radial confinement of trapped particles (150 keV or greater) within L = 14.3 as observed by the Voyager LECP instrument.

  17. Electrodynamics of solar wind-magnetosphere-ionosphere interactions

    NASA Technical Reports Server (NTRS)

    Kan, Joseph R.; Akasofu, Syun-Ichi

    1989-01-01

    The paper presents a coherent picture of fundamental physical processes in three basic elements of the solar-wind/magnetosphere/ionosphere coupling system: (1) the field-aligned potential structure which leads to the formation of auroral arcs, (2) the magnetosphere-ionosphere coupling which leads to the onset of magnetospheric substorms, and (3) the solar-wind/magnetosphere dynamo which supplies the power driving various magnetospheric processes. Process (1) is forced into existence by the loss-cone constriction effect when the upward field-aligned current density exceeds the loss-cone thermal flux limit. Substorm onset occurs when the ionosphere responds fully to the enhanced magnetospheric convection driven by the solar wind. Energy is transferred from the solar wind to the magnetosphere by a dynamo process, primarily on open field lines.

  18. New techniques in ionospheric sounding and studies

    NASA Astrophysics Data System (ADS)

    Reinisch, B. W.

    An overview is given of new techniques in ionospheric sounding and studies. Rapid progress in the integrated circuit market has led to new advanced techniques in the remote probing of the ionosphere with HF radio waves. The classical ionosonde which measured virtual height as a function of frequency has been expanded into a geophysical research tool by measuring all the observables contained in the electromagnetic signals reflected from the ionosphere: amplitude, phase, Doppler, incidence angle, and polarization. A receiving antenna array and high-speed digital processing provide the desired spatial and temporal resolution. The current emphasis is on the on-line and off-line post-processing of the multiparameter ionogram data to extract the geophysically important ionospheric characteristics: the vertical electron density profiles, horizontal gradients (tilts and waves), plasma drift, the mid-latitude F-region trough, and auroral and equatorial spread F. Digital ionosondes deployed in the polar cap and the auroral zone have helped to obtain a better understanding of some of the high latitude features, and measurements of the equatorial spread F show the development and motion of the F-region bubbles. HF coherent radar techniques which measure the velocity of irregularities with scale sizes of one half the radio wavelength have been used mainly in the northern auroral zone.

  19. Response of topside ionosphere to man-made electromagnetic emissions

    NASA Astrophysics Data System (ADS)

    Slominska, Ewa; Rothkaehl, Hanna; Slominski, Jan

    Investigation of electromagnetic measurements in the VLF range, obtained by DEMETER satellite revealed that terrestrial navigational stations are clearly "visible" in the ionosphere. Statistical studies were performed in the frequency range between 10kHz and 20kHz for one component of electric and magnetic field. We used data collected with ICE and IMSC in-struments placed on-board DEMETER. Global maps of man-made emissions show significant ionospheric response. This first satellite from the CNES MYRIADE micro-satellite series was launched on a polar orbit in June 2004 and provides permanent in-situ observations of ionospheric plasma parameters at the altitude of 700 km. As there are now more than five years of operational data a statistical study on both, the bulk ionospheric parameters and electromagnetic emissions, is possible. Since, statistical analysis have shown how easily are detectable man-made signals in the ionosphere, it has implied further studies on other plasma parameters. Using Langmuir probe experiment ISL ("Instrument Sonde de Langmuir") we develop global maps for electron temperature and density. Data are represented in geographic coordinates and averaged over one-month period. We present comparison analysis, that give the statistical background for further studies of noises occurring in the upper layers of ionosphere.

  20. The Flow of Plasma in the Solar-Terrestrial Environment

    NASA Technical Reports Server (NTRS)

    Schunk, Robert W.; Sojka, Jan J.; Barakat, Abdallah R.; Demars, Howard G.; Zhu, Lie

    2005-01-01

    The overall goal of our NASA theory research is to trace the flow of mass, momentum, and energy through the magnetosphere-ionosphere-atmosphere system taking into account the coupling, time delays, and feedback mechanisms that are characteristic of the system. Our approach is to model the magnetosphere-ionosphere-atmosphere (M-I-A) system in a self-consistent quantitative manner using unique global models that allow us to study the coupling between the different regions on a range of spatial and temporal scales. The uniqueness of our global models stems from their high spatial and temporal resolutions, the physical processes included, and the numerical techniques employed. Currently, we have time-dependent global models of the ionosphere, thermosphere, polar wind, plasmasphere, and electrodynamics. It is now becoming clear that a significant fraction of the flow of mass, momentum, and energy in the M-I-A system occurs on relatively small spatial scales. Therefore, an important aspect of our NASA Theory program concerns the effect that mesoscale (100-l000 km) density structures have on the macroscopic flows in the ionosphere, thermosphere, and polar wind. The structures can be created either by structured magnetospheric inputs (i.e., structured electric field, precipitation, or Birkeland current patterns) or by time variations of these inputs due to geomagnetic storms and substorms. Some of the mesoscale structures of interest include sun-aligned polar cap arcs, propagating plasma patches, traveling convection vortices, subauroral ion drift (SAID) channels, gravity waves, and the polar hole.

  1. A physical mechanism of positive ionospheric storms at low latitudes and midlatitudes

    Microsoft Academic Search

    N. Balan; K. Shiokawa; Y. Otsuka; T. Kikuchi; D. Vijaya Lekshmi; S. Kawamura; M. Yamamoto; G. J. Bailey

    2010-01-01

    A physical mechanism of the positive ionospheric storms at low latitudes and midlatitudes is presented through multi-instrument observations, theoretical modeling, and basic principles. According to the mechanism, an equatorward neutral wind is required to produce positive ionospheric storms. The mechanical effects of the wind (1) reduce (or stop) the downward diffusion of plasma along the geomagnetic field lines, (2) raise

  2. Titan's ionosphere: Model comparisons with Cassini Ta data T. E. Cravens,1

    E-print Network

    California at Berkeley, University of

    Titan's ionosphere: Model comparisons with Cassini Ta data T. E. Cravens,1 I. P. Robertson,1 J 2005. [1] On October 26, 2004, during its first encounter with Titan (Ta), the Cassini Orbiter moved of the main part of Titan's ionosphere were made by the Langmuir probe on the Cassini Radio and Plasma Wave

  3. Seasonal Variations in the Partition of Energy Imparted to Escaping Ionospheric Ions

    Microsoft Academic Search

    W. Peterson; H. Collin; A. W. Yau

    2001-01-01

    The aurora is powered by a downward flux of electromagnetic energy that also heats the ionosphere, generates many kinds of plasma waves, as well as accelerates electrons and ions. The amount of the incoming energy that is transferred into the kinetic energy of escaping ionospheric ions is relatively small. Energy is transferred to ions in two ways: Perpendicular to the

  4. Modeling of Ionospheric Responses to the Solar Flux Change Based on Millstone Hill Incoherent Scatter Radar

    Microsoft Academic Search

    S. Zhang; J. M. Holt

    2002-01-01

    In order to develop ionospheric empirical models of electron density Ne, plasma temperatures (Te and Ti) and ion drifts based on Millstone Hill incoherent scatter radar observations, we investigate an important issue of ionospheric responses to the solar flux changes that have to be quantitatively represented. The representation is associated with selecting a mathematical function where a suitable solar flux

  5. Global characterization of the equatorial ionospheric anomaly with data from the global ultraviolet imager

    Microsoft Academic Search

    Sidney B. Henderson II

    2006-01-01

    The Equatorial Anomaly (EA) is host to the highest ionospheric densities in the Earth's atmosphere. Disturbances within the EA result in plasma density depletions and large density gradients. In this dissertation we present a method for measuring EA morphology using nighttime 135.6 nm radiance observed by the Global Ultraviolet Imager (GUVI) on-board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED)

  6. New aspects in the annual variation of the ionosphere observed by the MU radar

    Microsoft Academic Search

    N. Balan; Y. Otsuka; S. Fukao

    1997-01-01

    Annual variations of the daytime ionosphere studied with the MU radar during a full solar cycle show equinoctial asymmetry in density, temperature, and plasma velocity. The electron density (Ne) in the bottomside ionosphere is slightly greater in September equinox compared to March equinox, which arises from the asymmetry in thermospheric composition. At higher altitudes, the asymmetry in Ne reverses and

  7. LONGITUDINAL VARIATION OF THE ANNUAL AND HEMISPHERIC ASYMMETRIES OF THE LOW-MIDDLE LATITUDE IONOSPHERE

    Microsoft Academic Search

    Y. Kwak; H. Kil; S. Oh; W. Lee; J. M. Forbes; K. Cho

    2009-01-01

    The longitudinal variation of the annual and hemispheric asymmetries in the low-middle latitude ionosphere at the altitude of 400 km during solar cycle 23 is examined by analyzing the F-region plasma density observations from the CHAMP satellite. The longitudinal variability of the ionospheric asymmetries has not yet been investigated on the global scale by using satellite data. In addition to

  8. New aspects in the annual variation of the ionosphere observed by the MU Radar

    Microsoft Academic Search

    N. Balan; Y. Otsuka; S. Fukao

    1997-01-01

    Annual variations of the daytime ionosphere studied with the MU radar during a full solar cycle show equinoctial asymmetry in density, temperature, and plasma velocity. The electron density (Ne) in the bottomside ionosphere is slightly greater in September equinox compared to March equinox, which arises from the asymmetry in thermospheric composition. At higher altitudes, the asymmetry in Ne reverses and

  9. Vlasov Simulations of Ionospheric Heating Near Upper HybridResonance

    NASA Astrophysics Data System (ADS)

    Najmi, A. C.; Eliasson, B. E.; Shao, X.; Milikh, G. M.; Papadopoulos, K.

    2014-12-01

    It is well-known that high-frequency (HF) heating of the ionosphere can excite field- aligneddensity striations (FAS) in the ionospheric plasma. Furthermore, in the neighborhood of variousresonances, the pump wave can undergo parametric instabilities to produce a variety of electrostaticand electromagnetic waves. We have used a Vlasov simulation with 1-spatial dimension, 2-velocitydimensions, and 2-components of fields, to study the effects of ionospheric heating when the pumpfrequency is in the vicinity of the upper hybrid resonance, employing parameterscurrently available at ionospheric heaters such as HAARP. We have found that by seeding theplasma with a FAS of width ~20% of the simulation domain, ~10% depletion, and byapplying a spatially uniform HF dipole pump electric field, the pump wave gives rise to a broadspectrum of density fluctuations as well as to upper hybrid and lower hybrid oscillating electricfields. We also observe collisionless bulk-heating of the electrons that varies non-linearly with theamplitude of the pump field.

  10. Ionospheric magnetic fields and currents at Venus and Mars.

    NASA Astrophysics Data System (ADS)

    Dubinin, Eduard; Fraenz, Markus; Zhang, TieLong; Woch, Joachim; Wei, Yong

    2014-05-01

    Venus Express spacecraft have provided us a wealth of in-situ observations of characteristics of induced magnetospheres of Venus at low altitudes during solar minimum conditions. At such conditions large-scale magnetic fields are observed deeply in the ionospheres (magnetized ionospheres). The arising magnetic field pattern occurs strongly asymmetrical. For example, in the ionosphere pointed in the direction opposite to the direction of the motional electric field in solar wind, the cross-flow component of the magnetic field changes sign. Asymmetry in the fields significantly modifies a plasma transport to the night side. We have found similar features at Mars while analyzing the magnetic field measurements made by Mars Global Surveyor. The VEX and MGS observations again raise a long-standing question about the origin of these fields in the magnetized ionospheres of Venus and Mars. The problem is intimately related to the issue of electric current system and their closure. We discuss different scenarios of the field origin.

  11. Cold Ion Escape from the Martian Ionosphere

    NASA Astrophysics Data System (ADS)

    Fränz, Markus; Dubinin, Eduard; Andrews, David; Nilsson, Hans; Fedorov, Andrei

    2014-05-01

    It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. The ion sensor IMA of this experiment has in principle a low-energy cut-off at 10eV but in negative spacecraft charging cold ions are lifted into the range of measurement but the field of view is restricted to about 4x360 deg. In a recent paper Nilsson et al. (Earth Planets Space, 64, 135, 2012) tried to use the method of long-time averaged distribution functions to overcome these constraints. In this paper we first use the same method to show that we get results consistent with this when using ASPERA-3 observations only. But then we can show that these results are inconsistent with observations of the local plasma density by the MARSIS radar instrument on board Mars Express. We demonstrate that the method of averaged distribution function can deliver the mean flow speed of the plasma but the low-energy cut-off does usually not allow to reconstruct the density. We then combine measurements of the cold ion flow speed with the plasma density observations of MARSIS to derive the cold ion flux. In an analysis of the combined nightside datasets we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of about 0.5 Martian radii the flux settles at a constant value which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

  12. Mars ionospheric response to solar wind variability

    NASA Astrophysics Data System (ADS)

    Opgenoorth, H. J.; Andrews, D. J.; Fränz, M.; Lester, M.; Edberg, N. J. T.; Morgan, D.; Duru, F.; Witasse, O.; Williams, A. O.

    2013-10-01

    planets with induced magnetospheres, the coupling between the ionosphere, the weak draped magnetosphere, and the solar wind is very direct in comparison to Earth. The weak induced magnetosphere itself is created by the prevailing Solar wind conditions and therefore in its shape and strength dynamically depending on it. In early 2010, Mars was located behind Earth in the Solar wind; thus, we can use coordinated data from multiple near-Earth spacecraft (Stereo, Wind) to evaluate what kind of Solar wind disturbances have passed by Earth and might consecutively hit Mars, and when. We employ plasma data from the ESA Mars-Express mission, the ASPERA-3 particle instrument, and the MARSIS Active Ionospheric Sounder (AIS) to investigate, for a number of isolated events in March and April 2010, how the ionosphere and the induced magnetosphere at Mars develop and decay in response to Solar wind variability in the magnetic field, density, and velocity. In a dedicated campaign mode, we use frequent long-duration MARSIS AIS operations for several consecutive orbits, to monitor for the first time the long-term development of the Martian plasma environment during solar wind disturbances. We find that the magnetosphere and ionosphere of Mars can become considerably compressed by solar wind dynamic pressure variations, which usually are also associated with changes in the magnetic draping of the interplanetary magnetic field around the planet. These are typically associated with corotating interaction regions and coronal mass ejections, and can last for several days. During such episodes of compression, we see signatures of increased plasma transport over the terminator and enhanced ion outflow from the upper atmosphere.

  13. International Reference Ionosphere 2010

    NASA Astrophysics Data System (ADS)

    Bilitza, D.; Reinisch, B. W.; McKinnell, L. A.

    2010-12-01

    The International Reference Ionosphere (IRI) is an international project sponsored by the Committee on Space research (COSPAR) and the International Union of Radio Science (URSI) that has as its goal the development and improvement of a data-based model of ionospheric densities, temperatures, and velocities using all available and reliable data sources for these ionospheric parameters. The model is widely recognized as the international standard for the specification of ionospheric parameters and recently was accepted by the International Standardization Organization (ISO) as Technical Specification TS 16457. This presentation will discuss the new version of the model, IRI-2010, which includes several important improvements and additions. The electron and ion densities in the lower ionosphere were significantly improved by using a large volume of ionosonde data as well as photochemical considerations. As an additional parameter IRI-2010 includes the transition height from molecular to cluster ions. At the F2 peak Neural Network based models for the peak density and the propagation factor M3000F2, which is related to the F2 peak height, are introduced as new options. For high latitudes the model will benefit from the introduction of auroral oval boundaries and their variation with magnetic activity. Regarding the electron temperature, IRI-2010 now models variations with solar activity.

  14. The morphology of the dayside ionospheric trough and the nightside stagnation region: a coupled study

    NASA Astrophysics Data System (ADS)

    Balthazor, R. L.; Denton, M. H.; Pryse, E.; Kersley, L.; Walker, I. K.; Moffett, R. J.

    2001-12-01

    The Aberystwyth tomographic imaging experiment and the Sheffield Coupled Thermosphere-Ionosphere-Plasmasphere model (SCTIP) have been used to investigate the dayside ionospheric trough at high latitude under different geomagnetic conditions. Previous work has suggested that the latitude of the trough minimum and the structure of the poleward wall is dependent on the electron precipitation, whereas the formation of the trough itself is dependent on the convection of flux tubes. We further discuss the roles of flux tube convection and the nightside stagnation region in the formation of both the dayside and nightside troughs, and the role of partially depleted flux tubes in the observed equatorward structuring of the trough region.

  15. Topside equatorial ionospheric density, temperature, and composition under equinox, low solar flux conditions

    NASA Astrophysics Data System (ADS)

    Hysell, D. L.; Milla, M. A.; Rodrigues, F. S.; Varney, R. H.; Huba, J. D.

    2015-05-01

    We present observations of the topside ionosphere made at the Jicamarca Radio Observatory in March and September 2013, made using a full-profile analysis approach. Recent updates to the methodology employed at Jicamarca are also described. Measurements of plasma number density, electron and ion temperatures, and hydrogen and helium ion fractions up to 1500 km altitude are presented for 3 days in March and September. The main features of the observations include a sawtooth-like diurnal variation in ht, the transition height where the O+ ion fraction falls to 50%, the appearance of weak He+ layers just below ht, and a dramatic increase in plasma temperature at dawn followed by a sharp temperature depression around local noon. These features are consistent from day to day and between March and September. Coupled Ion Neutral Dynamics Investigation data from the Communication Navigation Outage Forecast System satellite are used to help validate the March Jicamarca data. The SAMI2-PE model was able to recover many of the features of the topside observations, including the morphology of the plasma density profiles and the light-ion composition. The model, forced using convection speeds and meridional thermospheric winds based on climatological averages, did not reproduce the extreme temperature changes in the topside between sunrise and noon. Some possible causes of the discrepancies are discussed.

  16. The equatorial ionosphere over Brazilian region from ground based and satellite data

    NASA Astrophysics Data System (ADS)

    Batista, Inez S.; Abdu, Mangalathayil Ali; Vogel Ely, Claudia

    The equatorial ionosphere is characterized by various phenomena such as the instability pro-cesses that originate the equatorial electrojet, the equatorial ionization anomaly and the iono-spheric irregularities and plasma bubbles that can cause severe interference in the trans-ionospheric propagation of electromagnetic waves. Over the Brazilian region a set of ground based diagnose equipments has being providing data for more than three decades, that allowed a fairly good understanding of the climatology and of the main characteristics and peculiarities of the ionospheric phenomena over the region. Recent satellite missions, such as the Formosat 3/COSMIC, have provided a significant database that can be explored to give a more com-plete picture of the equatorial ionosphere. In this work we discuss the importance of these two datasets for the ionospheric studies over the equatorial region and present some results for the Brazilian region.

  17. Control of the topside Martian ionosphere by crustal magnetic fields

    NASA Astrophysics Data System (ADS)

    Andrews, D. J.; Edberg, N. J. T.; Eriksson, A. I.; Gurnett, D. A.; Morgan, D.; N?mec, F.; Opgenoorth, H. J.

    2015-04-01

    We present observations from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument onboard Mars Express of the thermal electron plasma density of the Martian ionosphere and investigate the extent to which it is influenced by the presence of Mars's remnant crustal magnetic fields. We use locally measured electron densities, derived when MARSIS is operating in active ionospheric sounding (AIS) mode, covering an altitude range from ˜300 km to ˜1200 km. We compare these measured densities to an empirical model of the dayside ionospheric plasma density in this diffusive transport-dominated regime. We show that small spatial-scale departures from the averaged values are strongly correlated with the pattern of the crustal fields. Persistently elevated densities are seen in regions of relatively stronger crustal fields across the whole altitude range. Comparing these results with measurements of the (scalar) magnetic field also obtained by MARSIS/AIS, we characterize the dayside strength of the draped magnetic fields in the same regions. Finally, we provide a revised empirical model of the plasma density in the Martian ionosphere, including parameterizations for both the crustal field-dominated and draping-dominated regimes.

  18. Nightside Ionospheric Electrodynamics Associated with Substorms: Multi Instrument Observations

    NASA Astrophysics Data System (ADS)

    Zou, S.; Lyons, L. R.; Nicolls, M. J.; Heinselman, C. J.; Mende, S. B.

    2009-05-01

    Poker Flat Incoherent Scatter Radar (PFISR), as a next-generation ISR with phased-array antenna system, can measure multiple ionospheric parameters with unprecedented temporal resolution and thus enables us to study rapidly evolving ionospheric processes, such as those associated with substorms. In this paper, we present observations from PFISR and complimentary ground-based magnetometers and THEMIS all-sky imaging array for substorm events and discuss the evolution of the nightside ionospheric convection as well as the current closing system, with particular emphasis on those near the Harang reversal region. Distinct but persistent features are found west of, within, and east of the onset region. By synthesizing observations from these three categories, as well as those from the SuperDARN radars and the IMAGE satellite, a 2-D picture of the evolution of ionospheric substorm electrodynamics has been established, which reveals features of an important relationship between the Region 2 and the substorm current systems. We believe these new observations can contribute to a better understanding of the magnetosphere-ionosphere coupling process during substorms and shed light on the underlying magnetospheric dynamics.

  19. Response of the Ionosphere-Plasmasphere System to Periodic Forcing

    NASA Astrophysics Data System (ADS)

    Pedatella, Nicholas M.

    The role of different mechanisms for generating periodic variability in the ionosphere and plasmasphere is studied in this dissertation. The impact of vertically propagating waves of lower atmospheric origin on introducing periodic spatial and temporal variability in the ionosphere and plasmasphere is first investigated. This is comprised of several different aspects. Initial focus is on the seasonal, local time, and altitude dependence of longitude variations due to nonmigrating tides in the F-region and topside ionosphere/plasmasphere using a combination of observations and numerical models. This is facilitated by the development of a new method for mitigating the effect of multipath on low-Earth orbit (LEO) satellite Global Positioning System (GPS) observations. The impact of large-scale changes in tropospheric convection due to the El-Nino Southern Oscillation on the ionosphere is also explored observationally. The influence of nonmigrating tides on the global ionosphere is revealed through study of the longitude variations in the solar quiet current system. Periodic temporal variability in the ionosphere due to planetary waves originating in the lower atmosphere is also investigated. The response of the global ionosphere to the quasi-16 day planetary wave is first presented. This is followed by observational evidence demonstrating that the nonlinear interaction between planetary waves and tides is the primary mechanism responsible for low-latitude ionospheric variability during sudden stratospheric warmings. Periodic temporal variability in the ionosphere and plasmasphere of solar origin is also studied. During the declining phase of solar cycle 23, near-Earth geospace was routinely disturbed due to high-speed solar wind streams emanating from solar coronal holes. The nature of the coronal holes was such that the Earth's upper atmosphere exhibited periodic behavior due to recurrent geomagnetic activity. A study of the latitude and local time response of the ionosphere to recurrent geomagnetic activity is performed herein. A method for estimating the location of the plasmapause from LEO GPS observations is also developed and applied to study periodic oscillations in the plasmapause.

  20. On the study of artificial ionospheric turbulence by means of stimulated electromagnetic emission

    SciTech Connect

    Frolov, V.L.; Boiko, G.N.; Metelev, S.A. [Scientific-Research Radio-Physics Institute, Nizhny Novgorod (Russian Federation)

    1995-01-01

    Results of measurements of the characteristics of stimulated electromagnetic emission induced in ionospheric plasma by pulsed high-power radio waves (diagnostic emission) presented. The dependences of the properties of diagnostic emission on the parameters of the diagnostic wave, ionospheric conditions, and the level of development of artificial ionospheric turbulence are determined, and criteria are given for selection of optimal diagnostic conditions for ionospheric-plasma sounding. Results of experiments on the sounding of artificial ionospheric turbulence by means of diagnostic emission are provided. It is established that with transition from daytime to evening conditions, the characteristic times of emission decay are sharply increased. This is attributed to an increase in the natural perturbation of the F-region.

  1. Superposed epoch analysis of dense plasma access to geosynchronous orbit

    NASA Astrophysics Data System (ADS)

    Lavraud, B.; Denton, M. H.; Thomsen, M. F.; Borovsky, J. E.; Friedel, R. H. W.

    2005-10-01

    We report on the occurrence of dense plasma access to geosynchronous orbit. We performed a superposed epoch analysis of 1464 events of dense (>2 cm 3 at onset) plasma observed by the MPA instruments on board the Los Alamos satellites, for the period 1990 2002. The results allow us to study the temporal evolution of various plasma parameters as a function of local time. We show that dense plasma access to geosynchronous orbit mostly occurs near local midnight. This dense plasma population is shown to be freshly injected from the mid-tail region, colder than the typical plasma sheet and composed of a relatively small O+ component. This population is thus probably the result of a cold, dense plasma sheet (CDPS) injection from the mid-tail region. Cold and dense ion populations are also observed on the dawnside of geosynchronous orbit at a similar epoch time. However, we demonstrate that this latter population is not the result of the dawnward transport of the population detected near midnight. The properties of this ion population may arise from the contribution of both ionospheric upflows and precipitating plasma sheet material. The correlation of an enhanced Kp index with the arrival of the CDPS at geosynchronous orbit shows that the inward transport of this population is allowed by an enhanced magnetospheric convection. Surprisingly, this dense plasma does not, in general, lead to a stronger Dst (ring current strength) within the 12 h following the CDPS injection. It is noted, however, that the superposed Kp index returns to relatively low values soon after the arrival of the CDPS. This may suggest that the dense plasma is, given the average of the 1464 events of this study, only transiting through geosynchronous orbit without accessing the inner regions and, therefore, does not contribute to the ring current. Keywords. Magnetospheric physics (Plasma convection; Plasma sheet) Space plasma physics (Transport processes)

  2. Topside sounders as mobile ionospheric heaters

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    2006-01-01

    There is evidence that satellite-borne RF sounders can act as mobile ionospheric heaters in addition to performing topside sounding. The main objective of topside sounding is to use sounder-generated electromagnetic (em) waves to obtain ionospheric topside vertical electron-density (N(sub e) profiles. These profiles are obtained from mathematical inversions of the frequency vs. delay-time ionospheric reflection traces. In addition to these em reflection traces, a number of narrowband intense signals are observed starting at zero delay times after the transmitted pulses. Some of these signals, termed plasma resonances, appear at characteristic frequencies of the ambient medium such as at the electron cyclotron frequency f(sub ce), the harmonics nf(sub ce), the electron plasma frequency f(sub pe) and the upper-hybrid frequency f(sub uh), where (f(sub uh))(exp 2) = (f(sub ce))(exp 2) + (f(sub pe))(exp 2) . These signals have been attributed to the oblique echoes of sounder-generated electrostatic (es) waves. These resonances provide accurate in situ f(sub pe) and f(sub ce) values which, in turn, lead to accurate N(sub e) and [B] values where B is the ambient magnetic field. Resonances are also observed between the nf(sub ce) harmonics both above and below f(sub uh). The former, known as the Qn plasma resonances, are mainly attributed to the matching of the wave group velocity of sounder-generated (Bernstein-mode) es waves to the satellite velocity. The frequency spectrum of these waves in the magnetosphere can be used to detect non-Maxwellian electron velocity-distributions. In addition, these resonances also exhibit components that appear to be the result of plasma emissions stimulated by the sounder pulses. The plasma resonances observed between the nf(sub ce) harmonics and below f(sub uh), known as the Dn plasma resonances, are entirely attributed to such sounder-stimulated plasma emissions. There are other sounder-stimulated plasma phenomena that also fall into this category, e.g., ion affects on electron-resonant phenomena, proton-cyclotron echoes and N(sub e) field-aligned irregularities (FAI). Some of these phenomena are more pronounced when f(sub pe)/f(sub ce) approx. = n where n is an integer significantly greater than one. The observations suggest that the sounder-stimulated plasma phenomena are stimulated, or enhanced, on a time scale much less than one second. The purpose of this presentation is to review the above topics with particular emphasis on the sounder-stimulated plasma phenomena.

  3. The Ptolemaic Approach to Ionospheric Electrodynamics

    NASA Astrophysics Data System (ADS)

    Vasyliunas, V. M.

    2010-12-01

    The conventional treatment of ionospheric electrodynamics (as expounded in standard textbooks and tutorial publications) consists of a set of equations, plus verbal descriptions of the physical processes supposedly represented by the equations. Key assumptions underlying the equations are: electric field equal to the gradient of a potential, electric current driven by an Ohm's law (with both electric-field and neutral-wind terms), continuity of current then giving a second-order elliptic differential equation for calculating the potential; as a separate assumption, ion and electron bulk flows are determined by ExB drifts plus collision effects. The verbal descriptions are in several respects inconsistent with the equations; furthermore, both the descriptions and the equations are not compatible with the more rigorous physical understanding derived from the complete plasma and Maxwell's equations. The conventional ionospheric equations are applicable under restricted conditions, corresponding to a quasi-steady-state equilibrium limit, and are thus intrinsically incapable of answering questions about causal relations or dynamic developments. Within their limited range of applicability, however, the equations are in most cases adequate to explain the observations, despite the deficient treatment of plasma physics. (A historical precedent that comes to mind is that of astronomical theory at the time of Copernicus and for some decades afterwards, when the Ptolemaic scheme could explain the observations at least as well if not better than the Copernican. Some of the verbal descriptions in conventional ionospheric electrodynamics might be considered Ptolemaic also in the more literal sense of being formulated exclusively in terms of a fixed Earth.) I review the principal differences between the two approaches, point out some questions where the conventional ionospheric theory does not provide unambiguous answers even within its range of validity (e.g., topside and bottomside boundary conditions on electrodynamics), and illustrate with some simple examples of how a neutral-wind dynamo really develops.

  4. Solar control of the Martian Ionosphere as Detected by MARSIS Active Ionospheric Sounder

    NASA Astrophysics Data System (ADS)

    Morgan, D. D.; Gurnett, D. A.; Kirchner, D. L.; Fox, J. L.; Nielsen, E.; Plaut, J. J.; Picardi, G.

    2007-12-01

    The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS), aboard the ESA spacecraft Mars Express, was deployed 17 June 2005 and commissioned in July 2005. MARSIS includes an Active Ionospheric Sounding (AIS) mode, which targets the topside ionosphere of Mars. Between August 2005 and July 2007, the spacecraft performed approximately 2500 orbits. From these orbits we have selected for analysis some 30,000 ionograms, about one-half of which were acceptable for inversion to an electron density profile. We bin these data by various quantities and plot the peak plasma densities and their corresponding altitudes from each bin as a function of solar zenith angle. Each plot can then be fit to a Chapman model to determine characteristic values of the subsolar plasma density peak, subsolar density peak altitude, and neutral scale height for that bin. The results from each bin can then be plotted as a function of the binned quantity to infer trends in the martian ionosphere. We detect an increase in electron density in the martian ionosphere with solar activity as indexed by F10.7 flux and XUV flux from SORCE XPS, both corrected for the changing distance of Mars from the Sun. We see an average change of about 6% in the subsolar peak electron density and a 6 km increase in the subsolar peak density altitude during periods when we can infer the presence of solar energetic particles from MARSIS AIS surface reflection data. We also see variation in the Chapman parameters due to seasonal and areodetic variation. In particular, at high latitudes near the summer solstice in both northern and southern hemispheres, we note an increase in the neutral scale height and decrease in the electron density peak altitude.

  5. Solitons and ionospheric heating

    NASA Technical Reports Server (NTRS)

    Weatherall, J. C.; Goldman, M. V.; Sheerin, J. P.; Nicholson, D. R.; Payne, G. L.; Hansen, P. J.

    1982-01-01

    It is noted that for parameters characterizing the Platteville ionospheric heating facility, the Langmuir wave evolution at the exact reflection point of the heater wave involves an oscillating two-stream instability followed by a collisionally damped three-dimensional soliton collapse. The result gives an alternative explanation for certain experimental observations.

  6. The ionospheric disturbance dynamo

    Microsoft Academic Search

    M. Blanc; A. D. Richmond

    1980-01-01

    The purpose of the present work is to develop a theory of the ionospheric disturbance dynamo and to examine, on the basis of theoretically predicted features, its relevance to the understanding of certain observations. A longitudinally symmetric, time-dependent numerical model of the thermospheric disturbance winds driven by an auroral heating event and the associated electric fields and currents derived for

  7. Thermospheric wind and electromagnetic drift influence on the night-time ionosphere-plasmasphere interaction

    Microsoft Academic Search

    Maria Knyazeva; Alexander Namgaladze; Oleg Martynenko

    2010-01-01

    The ionosphere-plasmasphere interaction at the night side had been modeled by using the global numerical Upper Atmosphere Model (UAM). The global distributions of the electron density and the geomagnetic field-aligned plasma fluxes have been calculated with and without taking into account the thermospheric wind induced field-aligned ion transport and the electromagnetic drift of the plasma. The initial ionosphere and plasmasphere

  8. Momentum, Heat, and Neutral Mass Transport in Convective Atmospheric Pressure Plasma-Liquid Systems and Implications for Aqueous Targets

    E-print Network

    Lindsay, Alexander; Slikboer, Elmar; Shannon, Steven; Graves, David

    2015-01-01

    There is a growing interest in the study of plasma-liquid interactions with application to biomedicine, chemical disinfection, agriculture, and other fields. This work models the momentum, heat, and neutral species mass transfer between gas and aqueous phases in the context of a streamer discharge; the qualitative conclusions are generally applicable to plasma-liquid systems. The problem domain is discretized using the finite element method. The most interesting and relevant model result for application purposes is the steep gradients in reactive species at the interface. At the center of where the reactive gas stream impinges on the water surface, the aqueous concentrations of OH and ONOOH decrease by roughly 9 and 4 orders of magnitude respectively within 50 $\\mu$m of the interface. Recognizing the limited penetration of reactive plasma species into the aqueous phase is critical to discussions about the therapeutic mechanisms for direct plasma treatment of biological solutions. Other interesting results fro...

  9. A Model of Callisto's Ionosphere

    NASA Astrophysics Data System (ADS)

    Hartkorn, O. A.; Saur, J.; Bloecker, A.; Strobel, D. F.; Simon, S.

    2014-12-01

    We develop a model of the ionosphere of Jupiter's moon Callisto, where we assume a stationary balance between sources and sinks of electrons and electron energy. Hence, effects of electron transport and electron energy transport are neglected. At Callisto, the production of electrons and electron energy is basically driven by photoionization, which is implemented using the EUVAC model for solar activity. Dissociative recombination is the main electron loss process, whereas electron energy loss is further driven by dissociation, electron impact ionization as well as vibrational and rotational excitations of neutral atmospheric particles. All these effects are incorporated within our model by considering the associated cross sections. The neutral atmosphere is assumed to be stationary and consists of molecular oxygen with a column density of 3 to 4 x 1020 m-2 (e.g. Kliore et al. (2002), Liang et al. (2005)). Our results can be compared to radio occultation observations of four Galileo spacecraft flybys reported by Kliore et al. (2002), which shows that this simple model can explain the general pattern of the observational data. Indeed, our results indicate that the detection of enhanced electron densities is very sensitive to the exact position of the tangential point of the radio occultation method. Our model shows that photoionization produces a strong asymmetry of the electron density distribution between day and night-side of the moon. Further, model results for the electron energy allow for an estimation of the day glow of Callisto's atmosphere. This can be compared to HST observations (Strobel et al. (2002)) in order to evaluate the density of the neutral oxygen atmosphere. Future studies imply the modeling of the modification of the ionospheric structure through interaction with upstreaming jovian magnetospheric plasma.

  10. Broadband meter-wavelength observations of ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Fallows, R. A.; Coles, W. A.; McKay-Bukowski, D.; Vierinen, J.; Virtanen, I. I.; Postila, M.; Ulich, Th.; Enell, C.-F.; Kero, A.; Iinatti, T.; Lehtinen, M.; Orispää, M.; Raita, T.; Roininen, L.; Turunen, E.; Brentjens, M.; Ebbendorf, N.; Gerbers, M.; Grit, T.; Gruppen, P.; Meulman, H.; Norden, M. J.; de Reijer, J.-P.; Schoenmakers, A.; Stuurwold, K.

    2014-12-01

    Intensity scintillations of cosmic radio sources are used to study astrophysical plasmas like the ionosphere, the solar wind, and the interstellar medium. Normally, these observations are relatively narrow band. With Low-Frequency Array (LOFAR) technology at the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) station in northern Finland we have observed scintillations over a three-octave bandwidth. "Parabolic arcs," which were discovered in interstellar scintillations of pulsars, can provide precise estimates of the distance and velocity of the scattering plasma. Here we report the first observations of such arcs in the ionosphere and the first broadband observations of arcs anywhere, raising hopes that study of the phenomenon may similarly improve the analysis of ionospheric scintillations. These observations were made of the strong natural radio source Cygnus-A and covered the entire 30-250 MHz band of KAIRA. Well-defined parabolic arcs were seen early in the observations, before transit, and disappeared after transit although scintillations continued to be obvious during the entire observation. We show that this can be attributed to the structure of Cygnus-A. Initial results from modeling these scintillation arcs are consistent with simultaneous ionospheric soundings taken with other instruments and indicate that scattering is most likely to be associated more with the topside ionosphere than the F region peak altitude. Further modeling and possible extension to interferometric observations, using international LOFAR stations, are discussed.

  11. Response of topside ionosphere to man-made electromagnetic emissions

    NASA Astrophysics Data System (ADS)

    Slominska, Ewa; Rothkaehl, Hanna; Slominski, Jan; Wiktorowicz, Grzegorz

    2010-05-01

    Investigation of electromagnetic measurements in the VLF range, obtained by DEMETER satellite revealed that terrestrial navigational stations are clearly "visible" in the ionosphere. Statistical studies were performed in the frequency range between 10kHz and 20kHz for one component of electric and magnetic field. We used data collected with ICE and IMSC instruments placed on-board DEMETER. This first satellite from the CNES MYRIADE micro-satellite series was launched on a polar orbit in June 2004 and provides permanent in-situ observations of ionospheric plasma parameters at the altitude of ~700 km. As there are now more than five years of operational data a statistical study on both, the bulk ionospheric parameters and electromagnetic emissions, is possible. Since, statistical analysis have shown how easily are detectable man-made signals in the ionosphere, it has implied further studies on other plasma parameters. Using Langmuir probe experiment ISL ("Instrument Sonde de Langmuir") we develop global maps for electron temperature and density. Data are represented in geographic coordinates and averaged over one-month period. We present comparison analysis, that give the statistical background for further studies of noises occurring in the upper layers of ionosphere.

  12. Upper limits to the nightside ionosphere of Mars

    NASA Astrophysics Data System (ADS)

    Fox, J. L.; Brannon, J. F.; Porter, H. S.

    1993-07-01

    The nightside ionosphere of Mars could be produced by electron precipitation or by plasma transport from the dayside, by analogy to the Venus, but few measurements are available. We report here model calculations of upper limits to the nightside ion densities on Mars that would be produced by both mechanisms. For the auroral model, we have adopted the downward traveling portions of the electron spectra measured by the HARP instrument on the Soviet Phobos spacecraft in the Martian plasma sheet and in the magnetotail lobes. For the plasma transport case, we have imposed on a model of the nightside thermosphere, downward fluxes of O(+), C(+), N(+), NO(+) and O2(+) that are near the maximum upward fluxes that can be sustained by the dayside ionosphere. The computed electron density peaks are in the range (1.3 - 1.9) x 10 exp 4/cu cm at altitudes of 159 to 179 kin. The major ion for all the models is O2(+), but significant differences in the composition of the minor ions are found for the ionospheres produced by auroral precipitation and by plasma transport. The calculations reported here provide a guide to the data that should be acquired during a future aeronomy mission to Mars, in order to determine the sources of the nightside ionosphere.

  13. Viscous Forces in Velocity Boundary Layers around Planetary Ionospheres.

    PubMed

    Pérez-De-Tejada

    1999-11-01

    A discussion is presented to examine the role of viscous forces in the transport of solar wind momentum to the ionospheric plasma of weakly magnetized planets (Venus and Mars). Observational data are used to make a comparison of the Reynolds and Maxwell stresses that are operative in the interaction of the solar wind with local plasma (planetary ionospheres). Measurements show the presence of a velocity boundary layer formed around the flanks of the ionosphere where the shocked solar wind has reached super-Alfvénic speeds. It is found that the Reynolds stresses in the solar wind at that region can be larger than the Maxwell stresses and thus are necessary in the local acceleration of the ionospheric plasma. From an order-of-magnitude calculation of the Reynolds stresses, it is possible to derive values of the kinematic viscosity and the Reynolds number that are suitable to the gyrotropic motion of the solar wind particles across the boundary layer. The value of the kinematic viscosity is comparable to those inferred from studies of the transport of solar wind momentum to the earth's magnetosphere and thus suggest a common property of the solar wind around planetary obstacles. Similar conditions could also be applicable to velocity boundary layers formed in other plasma interaction problems in astrophysics. PMID:10511515

  14. Upper limits to the nightside ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Fox, J. L.; Brannon, J. F.; Porter, H. S.

    1993-01-01

    The nightside ionosphere of Mars could be produced by electron precipitation or by plasma transport from the dayside, by analogy to the Venus, but few measurements are available. We report here model calculations of upper limits to the nightside ion densities on Mars that would be produced by both mechanisms. For the auroral model, we have adopted the downward traveling portions of the electron spectra measured by the HARP instrument on the Soviet Phobos spacecraft in the Martian plasma sheet and in the magnetotail lobes. For the plasma transport case, we have imposed on a model of the nightside thermosphere, downward fluxes of O(+), C(+), N(+), NO(+) and O2(+) that are near the maximum upward fluxes that can be sustained by the dayside ionosphere. The computed electron density peaks are in the range (1.3 - 1.9) x 10 exp 4/cu cm at altitudes of 159 to 179 kin. The major ion for all the models is O2(+), but significant differences in the composition of the minor ions are found for the ionospheres produced by auroral precipitation and by plasma transport. The calculations reported here provide a guide to the data that should be acquired during a future aeronomy mission to Mars, in order to determine the sources of the nightside ionosphere.

  15. F-region Magnetospheric ULF Generation by Modulated Ionospheric Heating

    NASA Astrophysics Data System (ADS)

    Papadopoulos, K.; Tesfaye, B.; Shroff, H.; Shao, X.; Milikh, G.; Chang, C.; Wallace, T.; Inan, U.; Piddyachiy, D.

    2007-12-01

    Current modulation of D/E region ionospheric currents at ULF frequencies results in generation of Shear Alfven Waves injected upwards and guided by the magnetic field lines towards the conjugate ionosphere. Under particular ionospheric conditions frequencies in the PC1 range (.2-6Hz) are reflected by the gradient in the Alfven velocity above the F-region resulting in the well-known Ionospheric Alfven Resonator (IAR) structure. Ground detection of ULF waves due to current modulation on the ground is thus limited to the vicinity of the heated spot since at these frequencies the coupling to the earth ionosphere waveguide is evanescent. Propagation of ULF waves at significant lateral distances requires generation of magnetosonic waves since they are the only mode that propagates isotropically and can thus couple efficiently in the Alfvenic duct. In this paper we present a completely new mechanism to generate magnetosonic waves by modulated ionospheric heating that does not require the presence of electrojet currents. The process relies in anomalous electron heating near the F-region peak by preferably using O-mode upper hybrid heating modulated at ULF Pc-1 frequencies. The modulation in the electron pressure drives a Bxgrad(p) oscillatory current. The resultant field aligned magnetic moment generates predominantly magnetosonic waves that are injected laterally into the Alfvenic duct and can also detected above the F-peak by over-flying satellites over distances larger than spanned by the field lines connecting to heated area. In addition to the concept and analytic results the paper will present simulations results using the ZEUS-MP MHD. Non-uniform grids are used to adapt to non-uniform ionospheric plasma density and thin layer of heating source. The effective heating region is placed at about 200-300 km in altitude (F-layer ionosphere). The modulated heating source is modeled as a source with perturbed density, temperature and magnetic field and it transmits modulated-HF electromagnetic waves into a stable ionosphere. Ratios of perturbed magnetic field and density to their background values are extracted from simulations. Different radiation patterns from different polarization component of magnetic field perturbation are investigated. Effects of different profiles of non-uniform ionospheric plasma density on ULF wave propagation are also studied through simulation. Preliminary experimental evidence of the process will also be presented. This work was sponsored by ONR MURI Grant 5-28828

  16. SuperDARN observations of the Harang discontinuity during steady magnetospheric convection

    Microsoft Academic Search

    J. M. Hughes; W. A. Bristow

    2003-01-01

    We present a study of ionospheric convection patterns observed by the Super Dual Auroral Radar Network (SuperDARN) during two recent steady magnetospheric convection (SMC) events. Our analyses focus on the region near the electrically defined Harang discontinuity (HDE) and indicate, for the first time, that the HDE is often present during SMC events. In comparison with observations made during a

  17. Lobe cell convection and field-aligned currents poleward of the region 1 current system

    E-print Network

    Eriksson, Stefan

    Lobe cell convection and field-aligned currents poleward of the region 1 current system S. Eriksson presented in support of lobe cell convection from an ionospheric perspective this far from the noon sector evidence for six large-scale field-aligned currents (FACs) rather than the usual system of four FACs

  18. Modeling Convection

    NSDL National Science Digital Library

    Amanda Schulz

    2004-09-01

    Typically, teachers use simple models that employ differences in temperature and density to help students visualize convection. However, most of these models are incomplete or merely hint at (instead of model) convective circulation. In order to make the use of models more effective, the authors developed an alternative system that uses a simple, low-cost apparatus that not only maintains dynamic convective circulation, but also illustrates two adjacent cells that teaches students about Earth's processes.

  19. A new concept of plasma motion and planetary magenetic field for Venus

    NASA Astrophysics Data System (ADS)

    Knudsen, W. C.; Banks, P. M.; Miller, K. L.

    1982-07-01

    It is shown that the magnetohydrodynamic conditions of the Venus ionosphere near the terminator favor convection of a magnetic field rather than diffusion. Consequently, any planetary magnetic field which Venus may possess will be strongly affected by the global antisunward flow of the ionosphere which has been revealed by the Pioneer-Venus retarding potential analyzer. The magnetic flux from an internal magnetic field will accumulate in the night hemisphere. Details of the structure and dynamics of such accumulations depend on particular details of the magnetic field source and the time-dependent plasma flow pattern, but a simple interpretation of observational data yields a magnetic dipole moment of 7 x 10 to the 20th cu cm directed along the planet spin vector.

  20. Chemistry in the Thermosphere and Ionosphere.

    ERIC Educational Resources Information Center

    Roble, Raymond G.

    1986-01-01

    An informative review which summarizes information about chemical reactions in the thermosphere and ionosphere. Topics include thermal structure, ultraviolet radiation, ionospheric photochemistry, thermospheric photochemistry, chemical heating, thermospheric circulation, auroral processes and ionospheric interactions. Provides suggested followup…

  1. A Campaign to Study Equatorial Ionospheric Phenomena over Guam

    NASA Astrophysics Data System (ADS)

    Habash Krause, L.; Balthazor, R.; Dearborn, M.; Enloe, L.; Lawrence, T.; McHarg, M.; Petrash, D.; Reinisch, B. W.; Stuart, T.

    2007-05-01

    With the development of a series of ground-based and space-based experiments, the United States Air Force Academy (USAFA) is in the process of planning a campaign to investigate the relationship between equatorial ionospheric plasma dynamics and a variety of space weather effects, including: 1) ionospheric plasma turbulence in the F region, and 2) scintillation of radio signals at low latitudes. A Digisonde Portable Sounder DPS-4 will operate from the island of Guam (with a magnetic latitude of 5.6° N) and will provide measurements of ionospheric total electron content (TEC), vertical drifts of the bulk ionospheric plasma, and electron density profiles. Additionally, a dual-frequency GPS TEC/scintillation monitor will be located along the Guam magnetic meridian at a magnetic latitude of approximately 15° N. In campaign mode, we will combine these ground-based observations with those collected from space during USAFA's FalconSAT-3 and FalconSAT-5 low-earth orbit satellite missions, the first of which is scheduled to be active over a period of several months beginning in the 2007 calendar year. The satellite experiments are designed to characterize in situ irregularities in plasma density, and include measurements of bulk ion density and temperature, minority-to- majority ion mixing ratios, small scale (10 cm to 1 m) plasma turbulence, and ion distribution spectra in energy with sufficient resolution for observations of non-thermalized distributions that may be associated with velocity- space instabilities. Specific targets of investigation include: a) a comparison of plasma turbulence observed on- orbit with spread F on ionograms as measured with the Digisonde, b) a correlation between the vertical lifting of the ionospheric layer over Guam and the onset of radio scintillation activity along the Guam meridian at 15° N magnetic latitude, and c) a correlation between on-orbit turbulence and ionospheric scintillation at 15° N magnetic latitude. These relationships may provide further clues into understanding the trigger mechanisms responsible for instigating disturbances in the ionospheric plasma, thus resulting in a turbulent radio propagation medium that may cause outages of radio based communication and navigation systems.

  2. Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation). Annual report No. 2

    Microsoft Academic Search

    1990-01-01

    The geomagnetic control of the Earth's atmosphere is well understood. In the F-region and the topside ionosphere, non-electrical forces transport plasma along the magnetic field lines only. In consequence, the worldwide distribution of ionization is strongly dependent on the dip angle. For example, the equatorial anomaly is roughly symmetrical about the dipole equator rather than the geographic. The same appears

  3. Ionospheric correction of space radar data

    E-print Network

    Hapgood, Mike

    2009-01-01

    Radar is a critical tool for maintaining knowledge of the many ob-jects in low Earth orbit and thus for maintaining confidence that societies around the world are secure against a variety of space-based threats. It is therefore important to raise awareness that LEO objects are embedded in the envelope of relatively dense plasma that co-rotates with the Earth (ionosphere-plasmasphere system) and thus accurate tracking must cor-rect for the group delay and refraction caused by that system. This paper seeks to promote that awareness by reviewing those effects and high-lighting key issues: the need to customise correction to the altitude of the tracked object and prevailing space weather conditions, that ionospheric correction may be particularly important as an object approaches re-entry. The paper outlines research approaches that should lead to better techniques for ionospheric correction and shows how these might be pur-sued in the context of the EURIPOS initiative.

  4. Impact of geomagnetic storm on fine and global structures of the ionosphere

    NASA Astrophysics Data System (ADS)

    Przepiorka, D.; Gromadzki, M.; Grzesiak, M.; Slominska, E.; Rothkaehl, H.; Space Plasma Group

    2011-12-01

    We have analyzed Demeter micro-satellite data, in particular from ISL, IAP and ICE experiments to study 3 magnetic storm events on January 2005: 7-8, 17-19 and 21-22. The most direct impact on ionosphere is situated at auroral zone but it also affects the dynamics of the ionosphere-thermosphere system at lower latitudes. In effect one can observe changes in the plasma parameters on the global scale. In this study we have analyzed plasma processes related to magnetic storm events and their impact on large scale ionospheric structures such as ionospheric trough. The aim of this study was to establish relation between large scale plasma inhomogeneities and small scale processes. We have produced diurnal global maps for electron density and temperature, ion temperature and ion concentrations. We also analyzed dynamics of the electric field distribution at ULF, ELF, VLF frequency ranges.

  5. Wave generation and transformation in the ionosphere possibly caused by seismic effects

    NASA Astrophysics Data System (ADS)

    Meister, Claudia-Veronika; Hoffmann, Dieter H. H.

    2015-04-01

    The dielectric model of waves in the Earth's ionosphere presented at the EGU General Assembly 2014 is further developed and applied to electromagnetic phenomena in seismoactive regions. The dielectric model consists of the magnetohydrodynamic system of equations describing the partially-ionized stratified convecting ionosphere and of the system of Maxwell equations. While in 2014, a new wave model was presented which takes the atmospheric stratification better into account in the Maxwell equations, now improved mathematical solutions for the dispersion relation of the excited waves are obtained. Especially, the influence of neutral gas winds is considered. Applications are performed for Alfvén and magnetohydrodynamic waves, as well as for the transformation of seismic infrasound waves into electromagnetic ionospheric ones. Expressions for ionospheric heating at different altitudes are derived and numerically analysed.

  6. Theory of radar detection of solitons during ionospheric heating

    NASA Technical Reports Server (NTRS)

    Sheerin, J. P.; Nicholson, D. R.

    1983-01-01

    RF modifiers at some existing ionospheric-heating facilities are found to be sufficiently intense for the production of (collapsing) solitons. The detection of these solitons using Thomson radar is considered, and the problem of an electromagnetic wave scattering off a collection of collapsing solitons is treated. The cross section for the process is found to be relatively large, and an intense plasma-line backscatter is predicted. An explanation of the phenomenon of 'plasma-line overshoot' is suggested.

  7. Vertical ionospheric sounding measurements

    Microsoft Academic Search

    W. F. Utlaut; T. N. Gautier

    1964-01-01

    This report presents data on the ionospheric perturbations resulting from the five 1962 high-altitude nuclear detonations, Star Fish, Check Mate, Blue Gill, King Fish, and Tight Rope, as obtained with sweep-frequency vertical-incidence ionosondes operated at the Islands of Maui, Tern (French Frigate Shoals), Midway, Wake (Star Fish only), Canton, Tutuila (American Samoa), and Tongatapu. The ionosondes at Midway and Tongataupu

  8. Variability of the ionosphere

    Microsoft Academic Search

    Jeffrey M. Forbes; Scott E. Palo; Xiaoli Zhang

    2000-01-01

    Hourly foF2 data from over 100 ionosonde stations during 1967–89 are examined to quantify F-region ionospheric variability, and to assess to what degree the observed variability may be attributed to various sources, i.e., solar ionizing flux, meteorological influences, and changing solar wind conditions. Our findings are as follows. Under quiet geomagnetic conditions (Kp<1), the 1-? (? is the standard deviation)

  9. Variability of the ionosphere

    Microsoft Academic Search

    J. M. Forbes; S. E. Palo; X. Zhang

    2000-01-01

    Hourly foF2 data from over 100 ionosonde stations during 1967-89 are examined to quantify F-region ionospheric variability, and to assess to what degree the observed variability may be attributed to various sources, i.e., solar ionizing flux, meteorological influences, and changing solar wind conditions. Our findings are as follows. Under quiet geomagnetic conditions (Kp<1), the \\/1-sigma (\\/sigma is the standard deviation)

  10. Investigation of electrical currents in the auroral ionosphere

    NASA Technical Reports Server (NTRS)

    Arnoldy, R. L.

    1978-01-01

    Two papers are presented on the investigation of electrical currents in the auroral ionosphere: (1) The Relationship Between Field-Aligned Current Carried by Suprathermal Electrons, and the Auroral Arc; and (2) Ionospheric Electrical Currents in the Late Evening Plasma Flow Reversal. In the first paper (1), data from four auroral sounding rockets, which directly measured field-aligned currents with partical detectors, are presented. In the second paper (2), data are presented for an instrumented sounding rocket that was launched from Andoya, Norway in January 1977, in the late evening auroral oval.

  11. Natural hazards monitoring and forecast using the GNSS and other technologies of the ionosphere monitoring

    NASA Astrophysics Data System (ADS)

    Pulinets, S. A.; Davidenko, D.

    2013-12-01

    It is well established now that Atmosphere-Ionosphere Coupling is provided through the local changes of the Global Electric Circuit parameters. Main agent - is column conductivity, modulated mainly at the altitudes of the Global Boundary Layer. We demonstrate the ionospheric effects for different types of natural hazards including volcano eruptions, dusty storms from Western Africa, ionospheric effects from tropical hurricanes, multiple earthquakes. We consider the important role of air ionization from natural (natural ground radioactivity and galactic cosmic rays) and artificial sources (nuclear weapon tests in atmosphere and underground, nuclear power stations and other nuclear enterprises emergencies). We rise also important question that such effects of the ionosphere variability are not taken into account by any ionospheric model and their correct recognition is important not only from the point of view the disasters monitoring but for navigation itself because the magnitude of the ionospheric effects sometimes exceeds the effects from strong magnetic storms and other severe space weather conditions. Some effects like ionospheric effects from tropical hurricanes have more complex physical nature including the formation of streams of neutral atmosphere over the hurricane eye and formation of the strong positive plasma concentration anomaly at the altitude near 1000 km. Some plasma anomalies registered over the tropical depressions before hurricane formation give hope on predictive capabilities of plasma observations over the tropical depressions.

  12. One-dimensional multi-species MHD model of the ionospheres of Venus and Mars

    SciTech Connect

    Shinagawa, H.

    1987-01-01

    The behavior of the ionospheric magnetic fields and ionospheric plasma of the dayside ionospheres of Venus and Mars was studied using a one-dimensional multi-species MHD model. The coupled continuity, momentum, and Maxwell's equations were solved simultaneously for the major ions and for the magnetic field. In the ionosphere of Venus, the calculated magnetic-filed profiles were in good agreement with observations obtained by the Pioneer Venus Orbiter magnetometer at all altitudes. Good agreement was also obtained between the calculated and observed plasma densities for altitudes below 250 km, including the electron density ledge near 190 km in magnetized ionospheres. It was found that the magnetic field in the lower ionosphere is maintained by the magnetic flux transported from the magnetic barrier region by the downward plasma motion. The model was also applied to the ionosphere of Mars in order to study the solar wind-Mars interaction and to estimate the magnitude of a possible intrinsic magnetic field on Mars. The calculation showed that even a small intrinsic magnetic field (B approx. = 30 nT) results in considerably larger electron densities at high altitudes than the densities measured by the retarding potential analyzers on Viking 1 and 2.

  13. Dynamics of the Venus ionosphere revisited

    SciTech Connect

    Mccormick, P.T.; Whitten, R.C.; Knudsen, W.C.

    1987-06-01

    The Whitten et al. (1984) dynamical model of the Venus ionosphere is presently modified in order to obtain a better match between observations and predictions. It is found that the nighttime ion densities are comparatively insensitive to the height of the ionopause above a value of 450 km. The density increases by only about 25 percent when the ionopause is raised to 800 km, but is noted to be very sensitive to the choice of a neutral model atmosphere, and to the ion and electron temperatures that influence both plasma scale height and ion diffusivity. 12 references.

  14. Ground and Space-Based Measurement of Rocket Engine Burns in the Ionosphere

    NASA Technical Reports Server (NTRS)

    Bernhardt, P. A.; Ballenthin, J. O.; Baumgardner, J. L.; Bhatt, A.; Boyd, I. D.; Burt, J. M.; Caton, R. G.; Coster, A.; Erickson, P. J.; Huba, J. D.; Earle, G. D.; Kaplan, C. R.; Foster, J. C.; Groves, K. M.; Haaser, R. A.; Heelis, R. A.; Hunton, D. E.; Hysell, D. L.; Klenzing, J. H.; Larsen, M. F.; Lind, F. D.; Pedersen, T. R.; Pfaff, R. F.; Stoneback, R. A.; Roddy, P. A.; Rodriguez, S. P.; San Antonio, G. S.; Schuck, P. W.; Siefring, C. L.; Selcher, C. A.; Smith, S. M.; Talaat, E. R.; Thomason, J. F.; Tsunoda, R. T.; Varney, R. H.

    2013-01-01

    On-orbit firings of both liquid and solid rocket motors provide localized disturbances to the plasma in the upper atmosphere. Large amounts of energy are deposited to ionosphere in the form of expanding exhaust vapors which change the composition and flow velocity. Charge exchange between the neutral exhaust molecules and the background ions (mainly O+) yields energetic ion beams. The rapidly moving pickup ions excite plasma instabilities and yield optical emissions after dissociative recombination with ambient electrons. Line-of-sight techniques for remote measurements rocket burn effects include direct observation of plume optical emissions with ground and satellite cameras, and plume scatter with UHF and higher frequency radars. Long range detection with HF radars is possible if the burns occur in the dense part of the ionosphere. The exhaust vapors initiate plasma turbulence in the ionosphere that can scatter HF radar waves launched from ground transmitters. Solid rocket motors provide particulates that become charged in the ionosphere and may excite dusty plasma instabilities. Hypersonic exhaust flow impacting the ionospheric plasma launches a low-frequency, electromagnetic pulse that is detectable using satellites with electric field booms. If the exhaust cloud itself passes over a satellite, in situ detectors measure increased ion-acoustic wave turbulence, enhanced neutral and plasma densities, elevated ion temperatures, and magnetic field perturbations. All of these techniques can be used for long range observations of plumes in the ionosphere. To demonstrate such long range measurements, several experiments were conducted by the Naval Research Laboratory including the Charged Aerosol Release Experiment, the Shuttle Ionospheric Modification with Pulsed Localized Exhaust experiments, and the Shuttle Exhaust Ionospheric Turbulence Experiments.

  15. 3D Multi-fluid Model of the Coupled Ion and Neutral Interaction between Titan's Ionosphere and Saturn's Magnetosphere

    Microsoft Academic Search

    D. S. Snowden; R. Winglee

    2009-01-01

    The interaction between plasma in Saturn's magnetosphere and Titan's ionosphere is complex because of the high density of neutral particles in Titan's ionosphere, the variability of Saturn's magnetosphere, and the variation of solar zenith angle as Titan orbits around Saturn's magnetosphere. Modeling this interaction can be difficult because 1-D and 2-D atmospheric models that include detailed chemistry cannot capture the

  16. Investigation of ionospheric disturbances and associated diagnostic techniques. Final report, 1 January 1992-31 December 1994

    Microsoft Academic Search

    1995-01-01

    The objectives of this research and development program were to conduct simulation modeling of the generation and propagation of atmospheric acoustic signals associated with surface and subsurface ground disturbances; to construct an experimental measurement system for exploratory research studies of acoustic generated ionospheric disturbances; to model high power radio wave propagation through the ionosphere, including nonlinear wave plasma interaction effects;

  17. The nighttime winter anomaly (NWA) effect in the american sector as a consequence of interhemispheric ionospheric coupling

    Microsoft Academic Search

    M. Foerster; N. Jakowski

    1988-01-01

    The nighttime winter anomaly (NWA) effect was observed during solar minimum conditions at the American sector by means of ionospheric electron content and vertical sounding measurements in Havana (Cuba). An effective interhemispheric transport of plasma is suggested to explain enhanced northern nighttime ionization during winter solstice. To elucidate this effect, an adequate physicalnumerical model of the coupled system ionosphere-plasmasphere is

  18. Gas convection caused by electron pressure drop in the afterglow of a pulsed inductively coupled plasma discharge

    SciTech Connect

    Cunge, G.; Vempaire, D.; Sadeghi, N. [Laboratoire des Technologies de la Microelectronique, CEA-LETI, CNRS, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2010-03-29

    Neutral depletion is an important phenomenon in high-density plasmas. We show that in pulsed discharges, the neutral depletion caused by the electron pressure P{sub e} plays an important role on radical transport. In the afterglow, P{sub e} drops rapidly by electron cooling. So, a neutral pressure gradient built up between the plasma bulk and the reactor walls, which forces the cold surrounding gas to move rapidly toward the reactor center. Measured drift velocity of Al atoms in the early afterglow of Cl{sub 2}/Ar discharge by time-resolved laser induced fluorescence is as high as 250 ms{sup -1}. This is accompanied by a rapid gas cooling.

  19. Low/Mid-latitude Ionospheric irregularities and scintillation climatology

    NASA Astrophysics Data System (ADS)

    Abdallah, Amr; Groves, K. M.; Mahrous, Ayman; Hussein, Fayrouz

    Ionospheric scintillation occur when radio signals propagate through an irregular ionosphere (e.g., plasma bubbles). Since plasma bubbles are regions of depleted ion and electron densities, a plasma bubble located on the satellite-to-ground signal path will cause radio signals to fluctuate in phase and amplitude. Ionospheric scintillation data were analyzed in the magnetic latitudinal field-of-view 29° N -13.4° N, observed by a stand-alone SCINDA (Scintillation Network Decision Aid) - GPS receiver at Helwan, Egypt (29.86° N, 31.32° E). A minimum 20° elevation cut off angle has been set in order to minimize the multipath effect. During the enhancing phase of the current solar cycle 24 (years 2010, 2011, 2012 and 2013), the behaviour of the scintillation occurrence were characterized. The seasonal, annual and solar cycle variation of scintillation occurrence is investigated together with the Total Electron Content (TEC), to put in evidence the relation between the electron density gradients and the ionospheric irregularities causing scintillation. This study considers a first step to develop a scintillation climatology over Northern Africa.

  20. Relationship between four-cell and distorted two-cell convection patterns during northward IMF

    Microsoft Academic Search

    L. Zhu; J. R. Kan

    1990-01-01

    Four-cell convection pattern in the ionosphere during a northward IMF (interplanetary magnetic field) was widely accepted until it was challenged by the distorted two-cell convection pattern proposed by Heppner and Maynard [1987]. We propose that a four-cell convection pattern, imposed on the magnetosphere by the solar wind, can be distorted into a wrapped two-cell pattern by the nonuniform and anisotropic

  1. Relationship between four-cell and distorted two-cell convection patterns during northward IMF

    Microsoft Academic Search

    L. Zhu; J. R. Kan

    1990-01-01

    Four-cell convection pattern in the ionosphere during a northward IMF was widely accepted until it was challenged by the distorted two-cell convection pattern proposed by Heppner and Maynard (1987). It is proposed here that a four-cell convection pattern, imposed on the magnetosphere by the solar wind, can be distorted into a wrapped two-cell pattern by the nonuniform and anisotropic conductance

  2. RCM-E and AMIE studies of the Harang reversal formation during a steady magnetospheric convection event

    NASA Astrophysics Data System (ADS)

    Yang, Jian; Toffoletto, Frank; Lu, Gang; Wiltberger, Michael

    2014-09-01

    This paper presents the results of a modeling study on the formation of the Harang reversal (HR) during a steady magnetospheric convection event. The Harang reversal is identified as the boundary of the northward and southward electric field in the nightside auroral zone using the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure. We simulate the event with the Rice Convection Model-Equilibrium (RCM-E) by adjusting its boundary conditions to approximately match Time History of Events and Macroscale Interactions during Substorms (THEMIS) and GOES observations in the nightside magnetosphere. Our results show that the HR is collocated with an upward region 1 field-aligned current, where converging ionospheric currents cause a southward/northward electric field on the poleward/equatorward side of the HR. Our results also indicate that the electric field reversal is slightly poleward of the ionospheric east-west current reversal and is to the northeast of the ground magnetic reversal, which is consistent with previous observations. We also test the sensitivity of the HR formation to a variety of parameters in the RCM-E simulations. We find that (1) the reduction of the flux tube entropy parameter PV5/3 near the midnight sector plays a major role in the formation of the HR; (2) a run carried out assuming uniform conductance produced the same major features as the run with more realistic precipitation-enhanced conductance; and (3) the detailed pattern of the polar cap potential distribution plays a minor role, but its dawn-dusk asymmetry significantly controls the location of the HR with respect to midnight. The RCM-E simulations also predict PV5/3 and flow distributions associated with the magnetospheric source of the HR in the plasma sheet, which can be further tested against observations.

  3. Mid-latitude ionospheric response to active experiments

    NASA Technical Reports Server (NTRS)

    Foster, John C.

    1992-01-01

    Understanding the ion chemistry and conditions leading to the formation of ionospheric depletions (ionospheric holes) was an important objective of the NASA active ionospheric experiment program. Millstone Hill radar observations were used to monitor the magnitude and temporal extent of the plasma holes produced under varying conditions. The major objective of the completed project was to provide radar diagnostic support for individual NASA rocket campaigns flown from Wallops Island. Two rocket programs, NICARE and REDAIR 2, were selected by NASA for radar support during the proposal period and pre-launch and in-flight radar observations were provided for each as well as basic reduction of the acquired data for scientific analysis. Radar operations and analysis for both of these experiments were performed as proposed and the work on these projects at M.I.T. was completed.

  4. Propagation of whistler mode waves through the ionosphere

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Woodroffe, J. R.; Huba, J. D.

    2012-08-01

    We present results from numerical studies of whistler mode wave propagation in the Earth's ionosphere when artificially created plasma ducts are present. Using realistic density profiles from the SAMI2 ionospheric code, we solve the two-dimensional electron magnetohydrodynamics equations to study the trans-ionospheric propagation of artificially generated whistler waves at HAARP latitudes (L = 4.9). Both ducted and non-ducted propagation is considered, but only ducted whistlers are able to propagate without a significant reduction in wave amplitude. The conditions necessary for the trapping of waves in both high- and low-density ducts are discussed with particular attention paid to the practical accessibility of these parameter regimes.

  5. IONOTOMO: A new approach for ionospheric tomography using OTH radar

    NASA Astrophysics Data System (ADS)

    Rummel, R. F.; Gruber, T.; Ihde, J.; Liebsch, G.; Sideris, M. G.; Rangelova, E. V.; Woodworth, P. L.; Hughes, C. W.; Gerlach, C.

    2011-12-01

    Tomography techniques have been recently developed to reconstruct electron density in the ionosphere. Most of the recent methods are based on the inversion of the Total Electron Content (TEC) measured by ground-based GPS receivers (e.g., Garcia & Crespon). Notwithstanding the high-density of the stations coverage, as a consequence of the high frequency of the GPS signals, the inversion of the TEC-GPS measurements mainly reconstructs the electron density of the F2 region, where the ionosphere reaches the maximum of ionization, neglecting the lower ionosphere regions. Close to the ionospheric tomography by GPS, additional studies in ionospheric tomography explore HF propagation by OTH radar (Fridman and Fridman, 1994; Ruelle and Landeau, 1994; Landeau et al., 1997; Fridman, 1998). Those works are only based on the inversion of the leading edge echo curve, neglecting valuable informations present in the OTH radar data. To overcome those limits, we set up a new ionospheric tomography 3D method, based on ray-tracing theory and achieving the full analysis of over-the-horizon (OTH) radar data. The major advance of our methodology is taking into account, numerically and jointly, not only the speed variation of EM wave induced by the electron density variation but also the perturbation in the raypath, both necessary for the OTH radar inversion. We present here the originality and the advantages of our method with a full set of synthetic benchmark highlighting the sensitivity of our tomography to the plasma heterogeneities. Additionally, we show the possibility to integrate GPS-TEC data as well as satellite TEC occultations to our tomographic method, for a complete joint inversion capable to reconstruct the entire ionosphere. [Fridman and Fridman, 1994] J. Atmos. Terr. Phys., 56, 115-131, 1994. [Ruelle and Landeau, 1994] J. Atmos. Terr. Phys., 56, 103-114, 1994. [Landeau et al., 1997] J. Atm. Solar Terr. Phys., 59, 125-138, 1997. [Fridman, 1998] Radio Sci., 33, 1159-1171, 1998.

  6. Atmosphere-Ionosphere Electrodynamic Coupling

    Microsoft Academic Search

    V. M. Sorokin; V. M. Chmyrev

    2010-01-01

    Numerous phenomena that occur in the mesosphere, ionosphere, and the magnetosphere of the Earth are caused by the sources located in the lower atmosphere and on the ground. We describe the effects produced by lightning activity and by ground-based transmitters operated in high frequency (HF) and very low frequency (VLF) ranges. Among these phenomena are the ionosphere heating and the

  7. Two Anomalies in the Ionosphere

    Microsoft Academic Search

    Edward V. Appleton

    1946-01-01

    DURING the War, many new ionospheric stations were instituted in different parts of the world to serve the operational requirements of the Allied Forces. As a result., there have become available, for the first time, sufficient data to provide a rough general morphological picture of the F2 layer of the ionosphere. A study of these data has disclosed the remarkable

  8. Mass spectrometry in ionospheric research.

    PubMed

    Ferguson, Eldon E

    2007-01-01

    Mass spectrometry played a key role in the development of the understanding of the earth's ionosphere. Of primary importance was its use for in situ atmospheric measurements of the ion and neutral composition of the atmosphere. Mass spectrometry has also played an essential role in the laboratory measurement of critical ionospheric molecular processes. Examples of both are given. PMID:17099890

  9. Asymmetric ionospheric outflow observed at the dayside magnetopause

    NASA Astrophysics Data System (ADS)

    Lee, S. H.; Zhang, H.; Zong, Q.-G.; Wang, Y.; Otto, A.; Rème, H.; Glassmeier, K.-H.

    2015-05-01

    An important source of the terrestrial magnetospheric plasma is the Earth's ionospheric outflows from the high-latitude regions of both hemispheres. The ionospheric ion outflows have rarely been observed at the dayside magnetopause. We report Cluster observations of the ionospheric ion outflows observed at the dayside magnetopause. The low-energy (up to 1.5 keV) electrons are detected with bidirectional pitch angle distributions indicating that the magnetic field lines are closed. The unidirectional cold ions (< 200 eV) are observed in the magnetosphere by both C1 and C3. The pitch angle distributions (0?-75?) of the cold ions (< 1 keV) at the dayside magnetopause indicate that these cold ions are the ionospheric outflows coming only from the Southern Hemisphere. The cold ions (< 200 eV) fluxes are modulated by the ULF wave electric field. Two different species (possibly H+ and He+) are observed in the magnetosphere. Our results suggest that the ionospheric outflows can directly reach the dayside magnetopause region and may participate in the reconnection process.

  10. Electron gyroharmonic effects on ionospheric stimulated Brillouin scatter

    NASA Astrophysics Data System (ADS)

    Mahmoudian, A.; Scales, W. A.; Bernhardt, P. A.; Isham, B.; Kendall, E.; Briczinski, S. J.; Fuentes, N. E. B.; Vega-Cancel, O.

    2014-08-01

    Stimulated Brillouin scattering (SBS) and resonant phenomena are well known in the context of laser fusion, fiber optics, and piezoelectric semiconductor plasmas, as well as in various biological applications. Due to recent advances, active space experiments using high-power high-frequency (HF) radio waves may now produce stimulated Brillouin scattering (SBS) in the ionospheric plasma. The sensitivity of the narrowband SBS emission lines to pump frequency stepping across electron gyroharmonics is reported here for the first time. Experimental observations show that SBS emission sidebands are suppressed as the HF pump frequency is stepped across the second and third electron gyroharmonics. A correlation of artificially enhanced airglow and SBS emission lines excited at the upper hybrid altitude is observed and studied for second gyroharmonic heating. The SBS behavior near electron gyroharmonics is shown to have important diagnostic applications for multilayered, multi-ion component plasmas such as the ionosphere.

  11. Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation). Annual report No. 2

    SciTech Connect

    Tan, A.

    1990-10-01

    The geomagnetic control of the Earth's atmosphere is well understood. In the F-region and the topside ionosphere, non-electrical forces transport plasma along the magnetic field lines only. In consequence, the worldwide distribution of ionization is strongly dependent on the dip angle. For example, the equatorial anomaly is roughly symmetrical about the dipole equator rather than the geographic. The same appears to be the case in the Jovian ionosphere (Mahajan, 1981). The influence of the magnetic field of Jupiter on its ionization pattern is one of several outstanding topics which need to be studied. Tan (1986) investigated the formation of the equatorial anomaly in the Jovian ionosphere under a centered dipole model. Tan (1988) further studied the effect of the tilt of the Jovian dipole. The results were in broad agreement with those of a diffusive equilibrium model (Tan and Wu, 1981). An off-centered dipole model is constructed and its effects on the ionization pattern are investigated.

  12. Scale Height variations with solar cycle in the ionosphere of Mars

    NASA Astrophysics Data System (ADS)

    Sanchez-Cano, Beatriz; Lester, Mark; Witasse, Olivier; Milan, Stephen E.; Hall, Benjamin E. S.; Cartacci, Marco; Radicella, Sandro M.; Blelly, Pierre-Louis

    2015-04-01

    The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on board the Mars Express spacecraft has been probing the topside of the ionosphere of Mars since June 2005, covering currently almost one solar cycle. A good knowledge of the behaviour of the ionospheric variability for a whole solar period is essential since the ionosphere is strongly dependent on solar activity. Using part of this dataset, covering the years 2005 - 2012, differences in the shape of the topside electron density profiles have been observed. These variations seem to be linked to changes in the ionospheric temperature due to the solar cycle variation. In particular, Mars' ionospheric response to the extreme solar minimum between end-2007 and end-2009 followed a similar pattern to the response observed in the Earth's ionosphere, despite the large differences related to internal origin of the magnetic field between both planets. Plasma parameters such as the scale height as a function of altitude, the main peak characteristics (altitude, density), the total electron content (TEC), the temperatures, and the ionospheric thermal pressures show variations related to the solar cycle. The main changes in the topside ionosphere are detected during the period of very low solar minimum, when ionospheric cooling occurs. The effect on the scale height is analysed in detail. In contrast, a clear increase of the scale height is observed during the high solar activity period due to enhanced ionospheric heating. The scale height variation during the solar cycle has been empirically modelled. The results have been compared with other datasets such as radio-occultation and retarding potential analyser data from old missions, especially in low solar activity periods (e.g. Mariner 4, Viking 1 and 2 landers), as well as with numerical modelling.

  13. Ionospheric Estimation and Integrity Threat Detection

    E-print Network

    Stanford University

    Ionospheric Estimation and Integrity Threat Detection Andrew J. Hansen Todd Walter Y.C. Chao Per is focused on ionospheric estimation using tomographic inversion and integrity monitoring of WAAS ionospheric currently focuses on the study of GPS dual-frequency measure- ment calibration, WAAS ionospheric modeling

  14. Feedback instability of the ionospheric resonant cavity

    Microsoft Academic Search

    Robert L. Lysak

    1991-01-01

    The exponential increase of the Alfven speed in the topside ionosphere leads to the formation of a resonant cavity (Lysak, 1988) which has been termed the ionospheric Alfven resonator by Trakhtengertz and Feldstein (1984). These authors primarily considered the situation where the ionospheric Pedersen conductivity is low, while Lysak (1988) considered the opposite limit of the infinite ionospheric conductivity. These

  15. Ionosphere around equinoxes during low solar activity

    Microsoft Academic Search

    Libo Liu; Maosheng He; Xin'an Yue; Baiqi Ning; Weixing Wan

    2010-01-01

    The seasonal behaviors of the ionosphere have been investigated for several decades, but the differences of the ionosphere between the March and September equinoxes are still an open question. In this analysis we utilize the data of ionospheric electron density (Ne) profiles from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission radio occultation measurements, total electron density (TEC)

  16. A plasma generator utilizing the high intensity ASTROMAG magnets

    NASA Technical Reports Server (NTRS)

    Sullivan, James D.; Post, R. S.; Lane, B. G.; Tarrh, J. M.

    1986-01-01

    The magnet configuration for the proposed particle astrophysics magnet facility (ASTROMAG) on the space station includes a cusp magnetic field with an intensity of a few tesla. With these large magnets (or others) located in the outer ionosphere, many quite interesting and unique plasma physics experiments become possible. First there are studies utilizing the magnet alone to examine the supersonic, sub-Alfvenic interaction with the ambient medium; the scale length for the magnet perturbation is approx. 20 m. The magnetic field geometry when combined with the Earth's and their relative motion will give rise to a host of plasma phenomena: ring nulls, x-points, ion-acoustic and lower-hybrid shocks, electron heating (possible shuttle glow without a surface) launching of Alfvenwaves, etc. Second, active experiments are possible for a controlled study of fundamental plasma phenomena. A controlled variable species plasma can be made by using an RF ion source; use of two soft iron rings placed about the line cusp would give an adequate resonance zone (ECH or ICH) and a confining volume suitable for gas efficiency. The emanating plasma can be used to study free expansion of plasma along and across field lines (polar wind), plasma flows around the space platform, turbulent mixing in the wake region, long wavelength spectrum of convecting modes, plasma-dust interactions, etc.

  17. Low-latitude ionospheric height variation as observed by meridional ionosonde chain: Formation of ionospheric ceiling over the magnetic equator

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Uemoto, Jyunpei; Ishii, Mamoru; Tsugawa, Takuya; Supnithi, Pornchai; Komolmis, Taradol

    2014-12-01

    A multipoint ionosonde observation campaign was conducted along the magnetic meridional plane in Southeast Asia to study ionosphere-thermosphere coupling. One station was near the magnetic equator and two of the other stations were at off-equatorial latitudes (˜10° magnetic latitude). The daytime ionospheric peak height (hmF2) was analyzed for each season during the solar minimum years, 2006-2007 and 2009. The peak height increased for ˜3 h after sunrise at the magnetic equator and off-equatorial latitudes, as expected from the daytime upward E × B drift. The apparent upward drift at the magnetic equator ceased before noon, while the drift at the off-equatorial latitudes continued upward and the layer height exceeded the equatorial height around noon. The noontime limited layer peak height at the magnetic equator, which was termed the ionospheric ceiling, did not depend on the season, while the maximum peak height at the off-equatorial latitudes largely varied with each season. Numerical modeling using the SAMI2 code was conducted and the features of the ionospheric ceiling were reproduced quite well. The dynamical parameters provided by the SAMI2 modeling runs showed that the ionospheric ceiling is formed by the field-aligned plasma diffusion, which is a part of the fountain effect.

  18. Solitons and ionospheric modification

    NASA Technical Reports Server (NTRS)

    Sheerin, J. P.; Nicholson, D. R.; Payne, G. L.; Hansen, P. J.; Weatherall, J. C.; Goldman, M. V.

    1982-01-01

    The possibility of Langmuir soliton formation and collapse during ionospheric modification is investigated. Parameters characterizing former facilities, existing facilities, and planned facilities are considered, using a combination of analytical and numerical techniques. At a spatial location corresponding to the exact classical reflection point of the modifier wave, the Langmuir wave evolution is found to be dominated by modulational instability followed by soliton formation and three-dimensional collapse. The earth's magnetic field is found to affect the shape of the collapsing soliton. These results provide an alternative explanation for some recent observations.

  19. Ionospheric heating with oblique HF waves

    SciTech Connect

    Field, E.C.; Bloom, R.M.

    1990-10-01

    This paper presents calculations of ionospheric electron density perturbations and ground-level signal changes produced by intense oblique high-frequency (HF) transmitters. Our analysis takes into account radio field focusing at caustics, the consequent joule-heating of the surrounding plasma, heat conduction, diffusion, and recombination processes--these being the effects of a powerful oblique modifying, wave. It neglects whatever plasma instabilities might occur. We then seek effects on a secondary 'test wave that is propagated along the same path as the first. Our calculations predict ground-level field-strength reductions of several dB in the test wave for modifying waves having ERP in the 85-to-90 dBW range. These field-strength changes are similar in sign, magnitude, and location to ones measured in Soviet experiments. Our results are sensitive to the the model ionosphere assumed, so future experiments should employ the widest possible range of frequencies and propagation conditions. An effective power of 90 dBW seems to be a sort of threshold that, if exceeded, results in substantial rather than small signal changes. Our conclusions are based solely on joule-heating and subsequent defocusing of waves passing through caustic regions.

  20. Ionospheric flows associated with a transpolar arc

    SciTech Connect

    Nielsen, E. (Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau (West Germany)); Carven, J.D.; Frank, L.A. (Univ. of Iowa, Iowa City (USA)); Heelis, R.A. (Univ. of Texas, Richardson (USA))

    1990-12-01

    A theta aurora is observed in the northern hemisphere on January 21, 1982, using the auroral imaging instrumentation on board the DE 1 spacecraft. The period of observations is from 1,807 to 2,121 UT. The transpolar arc is observed to advance toward the dusk sector, in the direction of the interplanetary magnetic field B{sub y} component. Coincidentally, the intersection between the arc and the auroral oval near local midnight passes through the field of view of the STARE coherent radar system, thereby providing the opportunity for measurements of the spatial pattern of ionospheric electron drift velocities. The convection flow in the arc is directed toward the nightside auroral oval, where it divides into westward and eastward directed flows (eastward and westward electrojets). Sunward flows are not observed along the transpolar arc near midnight. The overall flow pattern is identical to that expected at the Harang discontinuity. Two traversals of the auroral oval and polar cap with DE 2 demonstrate that, as expected, transitions from antisunward to sunward flow are associated with the dayside of the transpolar arc. The evolution of the arc and its convective features observed simultaneously on both the dayside and the nightside allow a more complete description of its global configuration than has been made previously.

  1. Ground- and Space-Based Observations of Ionospheric Irregularities over Nigeria during Solar Minimum

    NASA Astrophysics Data System (ADS)

    Carrano, C. S.; Yizengaw, E.; Doherty, P. H.; Bridgwood, C. T.; Adeniyi, J. O.; Amaeshi, L. L.; Pedersen, T. R.; Groves, K. M.; Roddy, P. A.; Caton, R. G.

    2009-12-01

    Ionospheric irregularities and plasma turbulence can cause scintillation in the amplitude and phase of trans-ionospheric radio waves employed by satellite navigation and communication systems, leading to a degradation of system performance. Due to the relatively sparse distribution of ground-based ionospheric monitoring instruments in Africa, the climatology and morphology of ionospheric irregularities over Africa have not been adequately characterized. Boston College, Air Force Research Laboratory, and the Universities of Ilorin and Lagos in Nigeria have collaborated to operate two high-rate GPS receivers capable of monitoring both Total Electron Content (TEC) and scintillation intensity. We use GPS measurements collected from 2007-2009 to 1) identify ionospheric irregularities and quantify their spatial extent, 2) estimate the zonal drift velocity by cross-correlating TEC measurements between pairs of GPS satellites, 3) relate ionospheric irregularities to the occurrence of weak scintillation at the GPS L1 frequency, 4) characterize the strength of amplitude and phase scintillations in terms of their power spectral densities, and 5) use phase screen theory to predict the intensity of scintillation that would be observed by ionospheric monitoring sensors operating at lower frequencies. Measurements of plasma density and zonal drift from the C/NOFS satellite during passes over Nigeria are used to corroborate and complement these ground-based GPS observations.

  2. Oblique reflections in the Mars Express MARSIS data set: Stable density structures in the Martian ionosphere

    NASA Astrophysics Data System (ADS)

    Andrews, David; André, Mats; Opgenoorth, Hermann; Edberg, Niklas; Diéval, Catherine; Duru, Firdevs; Gurnett, Donald; Morgan, David; Witasse, Olivier

    2014-05-01

    The Mars Advanced Radar for Sub-surface and Ionospheric Sounding (MARSIS) on board ESA's Mars Express (MEX) spacecraft routinely detects evidence of horizontal plasma density structures in the Martian ionosphere. Such structures, likely taking the form of spatially-extended elevations in the plasma density at a given altitude, give rise to oblique reflections in the Active Ionospheric Sounder (AIS) data. These structures are likely related to the highly-varied Martian crustal magnetic field. In this study, we use the polar orbit of MEX to investigate the repeatability of the ionospheric structures producing these anomalous reflections, examining sequences of multiple orbits which pass over the same regions of the Martian surface under similar solar illuminations. Presenting three such examples, or case-studies, we show that the signatures of these ionospheric structures are often incredibly stable over periods of many tens of days. To further investigate the nature of these ionospheric structures, we use a 2D ray-tracing code to simulate MARSIS's response to a variety of anomalous ionospheric profiles.

  3. Corotating interplanetary streams and associated ionospheric disturbances at Venus and earth

    SciTech Connect

    Taylor, H.; Cloutier, P.; Dryer, M.; Suess, S.; Barnes, A.; Wolff, R.; Stern, A.

    1984-01-01

    During the summer of 1979, solar corona structure was such that a sequence of recurrent regions produced a corresponding sequence of corotating solar wind streams with pronounced downstream signatures. One of these stream events passed earth on July 3 and was observed later at Venus late on July 11th, with similar characteristics. Corresponding in situ measurements at earth from the Atmospheric Explorer-E satellite and at Venus from the Pioneer Venus Orbiter are examined for evidence of comparable perturbations of the planetary ionospheres. The passage of the stream shock front is found to be associated with pronounced fluctuations in n(O+) which appear as pronounced local depletion of ion concentrations in both ionospheres. The ionosphere disturbances appear to be closely associated with large variations in the solar wind momentum flux. The implied local ionospheric depletions observed at each planet are interpreted to be the consequence of plasma redistribution, rather than actual depletions of plasma. 8 references.

  4. Three-dimensional waveform modeling of ionospheric signature induced by the 2004 Sumatra tsunami

    NASA Astrophysics Data System (ADS)

    Occhipinti, Giovanni; Lognonné, Philippe; Kherani, E. Alam; Hébert, Hélène

    2006-10-01

    The Sumatra, December 26th, 2004, tsunami produced internal gravity waves in the neutral atmosphere and large disturbances in the overlying ionospheric plasma. To corroborate the tsunamigenic hypothesis of these perturbations, we reproduce, with a 3D numerical modeling of the ocean-atmosphere-ionosphere coupling, the tsunami signature in the Total Electron Content (TEC) data measured by the Jason-1 and Topex/Poseidon satellite altimeters. The agreement between the observed and synthetic TEC shows that ionospheric remote sensing can provide new tools for offshore tsunami detection and monitoring.

  5. A new model of cometary ionospheres

    NASA Technical Reports Server (NTRS)

    Korosmezey, A.; Cravens, T. E.; Nagy, A. F.; Gombosi, T. I.; Mendis, D. A.

    1987-01-01

    The coupled continuity, momentum, and energy equations were solved for ionospheric conditions appropriate for Comet Halley at 1 AU. The numerical scheme used is such that any shock transition appears naturally in the solution and no a priori assumptions are necessary. Solutions were obtained for a number of different assumptions concerning electron heating rates, but all showed that the electron temperatures increase rapidly and significantly at a distance from the nucleus where collisional electron-neutral cooling becomes unimportant. This temperature increase is accompanied by a sharp increase in both the plasma pressure and its associated polarization electric field, causing the supersonic plasma flow to go subsonic. It is not clear at this time whether or not this sonic transition is accompanied by a shock.

  6. Interplanetary Radio Transmission Through Serial Ionospheric and Material Barriers

    SciTech Connect

    Fields, David [ORNL; Kennedy, Robert G [ORNL; Roy, Kenneth I [ORNL; Vacaliuc, Bogdan [ORNL

    2013-01-01

    A usual first principle in planning radio astronomy observations from the earth is that monitoring must be carried out well above the ionospheric plasma cutoff frequency (~5 MHz). Before space probes existed, radio astronomy was almost entirely done above 6 MHz, and this value is considered a practical lower limit by most radio astronomers. Furthermore, daytime ionization (especially D-layer formation) places additional constraints on wave propagation, and waves of frequency below 10-20 MHz suffer significant attenuation. More careful calculations of wave propagation through the earth s ionosphere suggest that for certain conditions (primarily the presence of a magnetic field) there may be a transmission window well below this assumed limit. Indeed, for receiving extraterrestrial radiation below the ionospheric plasma cutoff frequency, a choice of VLF frequency appears optimal to minimize loss. The calculation, experimental validation, and conclusions are presented here. This work demonstrates the possibility of VLF transmission through the ionosphere and various subsequent material barriers. Implications include development of a new robust communications channel, communications with submerged or subterranean receivers / instruments on or offworld, and a new approach to SETI.

  7. A comprehensive magnetohydrodynamic model of the Venus ionosphere

    SciTech Connect

    Shinagawa, H. (NASA Marshall Space Flight Center, Huntsville, AL (USA)); Kim, J.; Nagy, A.F. (Univ. of Michigan, Ann Arbor (USA)); Cravens, T.E. (Univ. of Kansas, Lawrence (USA))

    1991-07-01

    The MHD Venus ionospheric model developed by Shinagawa and Cravens (1988) has been improved by including the energy equations for ions and electrons in a self-consistent manner. This new model reproduces observed electron density and magnetic field profiles very well, and the basic MHD processes of the Venus ionosphere, as described by Shinagawa and Cravens (1988), remain virtually unchanged. The results indicate that including energetics does not significantly alter the density and magnetic field profiles. Under unmagnetized conditions, it is necessary to impose heat fluxes for both ions and electrons in order to reproduce the observed plasma temperature profiles, which are consistent with the studies by Cravens et al. (1979, 1980) and Kim et al. (1990). In the magnetized ionosphere, it is likely that a heat source for the ions is present at higher altitudes. On the other hand, the observed very high electron temperatures can be reproduced with a reduced conductivity or with a heat source at high altitudes. It is also found that heating processes do not play a significant role in the dynamics at low altitudes. Thus a nearly supersonic downward velocity layer in the lower ionosphere of Venus, proposed by Cloutuer at al. (1987), is unlikely, suggesting that their flow/field model is not applicable to the solar wind-Venus interaction and other unmagnetized bodies in magnetized plasma flows.

  8. Ionospheric and magnetospheric plasmapauses'

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Hoffman, J. H.; Maynard, N. C.

    1977-01-01

    During August 1972, Explorer 45 orbiting near the equatorial plane with an apogee of about 5.2 R sub e traversed magnetic field lines in close proximity to those simultaneously traversed by the topside ionospheric satellite ISIS 2 near dusk in the L range 2-5.4. The locations of the Explorer 45 plasmapause crossings during this month were compared to the latitudinal decreases of the H(+) density observed on ISIS 2 near the same magnetic field lines. The equatorially determined plasmapause field lines typically passed through or poleward of the minimum of the ionospheric light ion trough, with coincident satellite passes occurring for which the L separation between the plasmapause and trough field lines was between 1 and 2. Vertical flows of the H(+) ions in the light ion trough as detected by the magnetic ion mass spectrometer on ISIS were directed upward with velocities between 1 and 2 kilometers/sec near dusk on these passes. These velocities decreased to lower values on the low latitude side of the H(+) trough but did not show any noticeable change across the field lines corresponding to the magnetospheric plasmapause.

  9. 3D global MHD simulation of the interaction between Saturn's magnetosphere and Titan's atmosphere\\/ionosphere

    Microsoft Academic Search

    Y. Ma; A. F. Nagy; T. Cravens; I. Sokolov

    2004-01-01

    We present our simulation results of the interaction between Saturn's magnetospheric plasma flow and Titan's atmosphere\\/ionosphere by using a multi-species global MHD model. A chemical model is used to describe Titan's atmosphere\\/ionosphere, which is based on 10 neutral and 7 ion spieces. This new model uses spherical coordinates (similar to our Mars model) leading to very good(~28km) altitude resolution. The

  10. A statistical model of ionospheric signals in low-frequency SAR data

    Microsoft Academic Search

    F. J. Meyer; B. Watkins

    2011-01-01

    This paper focuses on deriving a realistic statistical model for ionospheric effects in low-frequency Synthetic Aperture Radar (SAR) data. The approach used to develop this statistical model is based on the assumption that, for a certain range of scales, ionospheric plasma turbulence can be considered a scale-invariant process that can be described by power-law functions or fractal statistics. Based on

  11. The characteristics of the ionospheric asymmetries during the solar cycle 23 (Invited)

    Microsoft Academic Search

    W. Lee; H. Kil; Q. Wu; Y. Kwak; J. Chung; S. Cho

    2009-01-01

    We investigate the annual and hemispheric asymmetries in the ionospheric plasma density during the solar cycle 23 by analyzing the FORMOSAT-3\\/COSMIC, CHAMP, and ROCSAT-1 satellite data. The preliminary results obtained from the COSMIC radio occultation data shows that the ionospheric asymmetries vary with latitude, altitude, hemisphere, and local time during the solar minimum period (2007-2008). For an example, the difference

  12. Substorm onset by plasma sheet divergence

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Wang, C.-P.; Nagai, T.

    2003-12-01

    It is necessary to understand current wedge formation in order to understand the cause of the substorm expansion phase. In the companion paper we used Geotail spacecraft observations to show that the cross-tail current reduction within the inner-plasma-sheet current wedge results from a process that leads to a reduction in equatorial plasma pressure and a substantial reduction in flux tube ion content. Here we use the single-species continuity equation for plasma sheet particles to identify a plausible cause of these plasma reductions and thus for current wedge formation and the initiation of the substorm expansion phase. Specifically, we find that a convection reduction, which follows a growth phase period of enhanced convection, should cause a divergence of plasma sheet particles driven by diamagnetic drift that leads to flux tube content reduction. We find that the reduction in flux tube content should be longitudinally localized to the premidnight to midnight region where the current wedge has been observed to initially form and that the reduction must initiate within the region of the equatorial mapping of the Harang discontinuity, consistent with ionospheric observations of substorm onset. We also find that the reduction in flux tube content should initially develop slowly and then develop more rapidly as the current wedge forms. This is consistent with observations which show that expansion phase aurora, and thus also the current wedge, develops slowly for a few minutes before brightening rapidly, and it is as required if plasma sheet divergence driven by diamagnetic drift leads to current wedge formation and initiation of the substorm expansion phase.

  13. Cold Ion Escape from the Martian Ionosphere

    NASA Astrophysics Data System (ADS)

    Fraenz, M.; Dubinin, E.; Wei, Y.; Woch, J. G.; Morgan, D. D.; Barabash, S. V.; Lundin, R. N.; Fedorov, A.

    2012-12-01

    It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. We first use support from the MARSIS radar experiment for some orbits with fortunate observation geometry. Here we have observed a transterminator flow of O+ and O2+ ions with a super-sonic velocity of around 5km/s and fluxes of 0.8x10^9/cm^2s. If we assume a symmetric flux around the terminator this corresponds to an ion flow of 3.1x10^25/s half of which is expected to escape from Mars (Fraenz et al, 2010). This escape flux is significantly higher than previously observed on the tailside of Mars, we discuss possible reasons for the difference. Since 2008 the MARSIS radar does nightside local plasma density measurement which often coincide with ASPERA-3 measurements. In a new analysis of the combined nightside datasets (Fig. 1) we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of about 0.5 R_M the flux settles at a constant value (Fig. 2) which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvenic regime.; Median oxygen ion flux reconstructed by combining ion velocity observations of the Mars Express ASPERA-3 IMA sensor and local plasma density observations by the MARSIS radar. Each bin value is the median from observations on about 3000 orbits between May 2007 and July 2011. Horizontal axis is MSO X-axis (Sun towards the left), vertical axis is vertical distance from MSO X-axis. ; Ring median flux of cylindrical ring regions of all bins shown in previous figure. The different colors show median fluxes for different regions in R-cylindrical (distance from MSO-X-axis) as a function of tailward distance from the terminator (or surface for Rcyl < 1).

  14. Auroral vortex street formed by the magnetosphere-ionosphere coupling instability

    E-print Network

    Hiraki, Yasutaka

    2014-01-01

    By performing three-dimensional nonlinear MHD simulations including Alfven eigenmode perturbations most unstable to the ionospheric feedback effects, we reproduced the auroral vortex street that often appears just before substorm onset. We found that an initially placed arc splits, intensifies, and rapidly deforms into a vortex street. We also found that there is a critical convection electric field for growth of the Alfven eigenmodes. The vortex street is shown to be a consequence of coupling between the magnetospheric Alfven waves carrying field-aligned currents and the ionospheric density waves driven by Pedersen/Hall currents.

  15. The convection electric field in auroral substorms

    NASA Astrophysics Data System (ADS)

    Gjerloev, J. W.; Hoffman, R. A.

    2001-07-01

    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 by DE 1. The selected passes, which occurred during substorm expansion phase, maximum, or early recovery phase, cover the entire nighttime substorm. The organization of the data used the method developed by Fujii et al. [1994], which divided the data into six local time sectors covering the nighttime substorm region. Following the procedures employed in the paper by Gjerloev and Hoffman [2000b], the latitudinal width and location of each auroral oval crossing was then adjusted to fit the sector average. In addition to the detailed study of the characteristics of the field within each sector 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 channel is coincident with the highest conductances located just poleward of the Harang region. This channel drives the substorm current wedge component of the westward electrojet in the surge and middle surge sectors. It is present in all premidnight passes and consequently is an integral part of the three-dimensional substorm current wedge system.

  16. Features of steady magnetospheric convection

    NASA Technical Reports Server (NTRS)

    Yahnin, A.; Malkov, M. V.; Sergeev, V. A.; Pellinen, R. J.; Aulamo, O.; Vennergstrom, S.; Friis-Christensen, E.; Lassen, K.; Danielsen, C.; Craven, J. D.

    1994-01-01

    The large-scale patterns of ionospheric convection and particle precipitation are described during two intervals of steady magnetospheric convection (SMC) on November 24, 1981. The unique data set used in the analysis includes recordings from the worldwide network of magnetometers and all-sky cameras, global auroral images from the Dynamics Explorer (DE) 1 spacecraft, and particle precipitation data from low-altitude National Oceanic and Atmospheric Administration (NOAA) 6 and NOAA 7 spacecraft. The data show that intense magnetospheric convection continued during more than 10 hours under the steady southward interplanetary magnetic field without any distinct substorm signatures. All data sets available confirmed the stable character of the large-scale magnetospheric configuration during this period. In particular, the magnetic flux threading the polar cap was stable (within 10%) during 3.5 hours of continued DE 1 observations. The dayside cusp was located at an unusually low latitude (70 deg CGL). The nightside auroral pattern consisted of two distinct regions. The diffuse aurora in the equatorward half of the expanded (10 deg wide) auroral oval was well-separated from the bright, active auroral forms found in the vicinity of the poleward boundary of the oval. The twin-vortex convection pattern had no signature of the Harang discontinuity; its nightside 'convection throat' was spatially coincident with the poleward active auroras. This region of the auroral oval was identified as the primary site of the short-lived transient activations during the SMC intervals. The energetic particle observations show that the auroral precipitation up to its high-latitude limit is on closed field lines and that particle acceleration up to greater than 30-keV energy starts close to this limit. The isotropic boundaries of the greater than 30-keV protons and electrons were found close to each other, separating regions of discrete and diffuse precipitation. This suggests that these precipitation types originate on the very taillike and very dipolelike field lines, respectively.

  17. Features of steady magnetospheric convection

    SciTech Connect

    Yahnin, A.; Malkov, M.V. [Polar Geophysical Institute, Apatity (Russian Federation)] [Polar Geophysical Institute, Apatity (Russian Federation); Sergeev, V.A. [Univ. of St. Petersburg (Russian Federation)] [Univ. of St. Petersburg (Russian Federation); Pellinene, R.J.; Aulamo, O. [Finnish Meteorological Institute, Helsinki (Finland)] [Finnish Meteorological Institute, Helsinki (Finland); Vennerstroem, S.; Friis-Christensen, E.; Lassen, K.; Danielsen, C. [Danish Meteorological Institute, Copenhagen (Denmark)] [Danish Meteorological Institute, Copenhagen (Denmark); Craven, J.D. [Univ. of Alaska, Fairbanks (South Africa)] [and others] [Univ. of Alaska, Fairbanks (South Africa); and others

    1994-03-01

    The large-scale patterns of ionospheric convection and particle precipitation are described during two intervals of steady magnetospheric convection (SMC) on November 24, 1981. The unique data set used in the analysis includes recordings from the worldwide network of magnetometers and all-sky cameras, global auroral images from the DE 1 spacecraft, and particle precipitation data from low-altitude NOAA 6 and NOAA 7 spacecraft. The data show that intense magnetospheric convection continued during more than 10 hours under the steady southward interplanetary magnetic field without any distinct substorm signatures. All data sets available confirmed the stable character of the large-scale magnetospheric configuration during this period. In particular, the magnetic flux threading the polar cap was stable (within 10%) during 3.5 hours of continued DE 1 observations. The dayside cusp was located at an unusually low latitude (70{degrees} CGL). The nightside auroral pattern consisted of two distinct regions. The diffuse aurora in the equatorward half of the expanded (10{degrees} wide) auroral oval was well-separated from the bright, active auroral forms found in the vicinity of the poleward boundary of the oval. The twin-vortex convection pattern had no signature of the Harang discontinuity; its nightside {open_quotes}convection throat{close_quotes} was spatially coincident with the poleward active auroras. This region of the auroral oval was identified as the primary site of the short-lived transient activations during the SMC intervals. The energetic particle observations show that the auroral oval was identified as the primary site of the short-lived transient activations during the SMC intervals. The energetic particle observations show that the auroral precipitation up to its high-latitude limit is on closed field lines and that particle acceleration up to > 30-keV energy starts close to this limit. 34 refs., 11 figs., 1 tab.

  18. Arrival of a tongue of ionization in the nightside polar ionosphere and effects on GPS scintillation

    NASA Astrophysics Data System (ADS)

    van der Meeren, Christer; Oksavik, Kjellmar; Lorentzen, Dag; Idar Moen, Jøran; Romano, Vincenzo

    2014-05-01

    In this case study we present findings of Global Positioning System (GPS) scintillation in relation to the arriving front of a tongue of ionization in the nightside polar cap over Svalbard. We find almost no amplitude and some phase scintillation in relation to the leading density gradient, which is interpreted as "false" refractive scintillation due to suboptimal data detrending, as opposed to diffractive scintillation from decametre-to-kilometre-scale irregularities. During active geomagnetic conditions, high-density plasma may convect into and across the polar cap. The plasma may be segmented into F region polar cap patches upon entry in the cusp/cleft region, or it may form a continuous tongue of ionization when no such segmentation occurs. Large-scale ionospheric plasma structures such as polar cap patches may contain decametre- to kilometre-scale irregularities, particularly at the edges. Irregularities of these scale sizes cause problems for global navigation satellite system (GNSS) signals, causing amplitude and phase variations known as scintillations. A drawback of most high-latitude GNSS scintillation studies is the use of a 0.1 Hz detrending filter cutoff frequency, which in the literature has been shown to cause "false" phase scintillation. In the literature, much of the high-latitude scintillation research is statistically oriented and concerns polar cap patches. Scintillation directly in relation to ionization tongues is far less studied. We present findings of GPS scintillation in relation to the arriving front of a tongue of ionization on 31 October 2011 in the nightside polar cap over Svalbard, using GPS scintillation and total electron content (TEC) monitors, the EISCAT Svalbard Radar (ESR), and an optical all-sky airglow imager. To our knowledge, this is the first study presenting such detailed multi-instrument data of scintillation in the Svalbard region as well as taking into account the problems of a 0.1 Hz detrending cutoff filter.

  19. Ionospheric modification using relativistic electrons beams

    SciTech Connect

    Banks, P.M.; Fraser-Smith, A.C.; Gilchrist, B.E.

    1990-10-01

    The recent development of comparatively small electron linear accelerators (linacs) now makes possible a new class of ionospheric modification experiments using beams of relativistic electrons. These experiments can potentially provide much new information about the interactions of natural relativistic electrons with other particles in the upper atmosphere, and it may also make possible new forms of ionization structures extending down from the lower ionosphere into the largely unionized upper atmosphere. In this paper we investigate the consequences of firing a pulsed 1 A, 5 Mev electron beam downwards into the upper atmosphere. If a small pitch angle with respect to the ambient geomagnetic field is selected, the beam produces a narrow column of substantial ionization extending down from the source altitude to altitudes of - 40 to 45 km. This column is immediately polarized by the natural middle atmosphere fair weather electric field and an increasingly large potential difference is established between the column and the surrounding atmosphere. In the regions between 40 to 60 km, this potential can amount to many tens of kilovolts and the associated electric field can be greater than the field required for breakdown and discharge. Under these conditions, it may be possible to initiate lightning discharges along the initial ionization channel. Filamentation may also occur at the lower end to drive further currents in the partially ionized gases of the stratosphere. Such discharges would derive their energy from the earth-ionosphere electrical system and would be sustained until plasma depletion and/or electric field reduction brought the discharge under control. It is likely that this artificially-triggered lightning would produce measurable low-frequency radiation.

  20. Simulating the interplay between plasma transport, electric field, and magnetic field in the near-earth nightside magnetosphere

    NASA Astrophysics Data System (ADS)

    Gkioulidou, Malamati

    The convection electric field resulting from the coupling of the Earth's magnetosphere with the solar wind and interplanetary magnetic field (IMF) drives plasma in the tail plasma sheet earthward. This transport and the resulting energy storage in the near Earth plasma sheet are important for setting up the conditions that lead to major space weather disturbances, such as storms and substorms. Penetration of plasma sheet particles into the near-Earth magnetosphere in response to enhanced convection is crucial to the development of the Region 2 field-aligned current system and large-scale magnetosphere-ionosphere (M-I) coupling, which results in the shielding of the convection electric field. In addition to the electric field, plasma transport is also strongly affected by the magnetic field, which is distinctly different from dipole field in the inner plasma sheet and changes with plasma pressure in maintaining force balance. The goal of this dissertation is to investigate how the plasma transport into the inner magnetosphere is affected by the interplay between plasma, electric field and magnetic field. For this purpose, we conduct simulations using the Rice Convection Model (RCM), which self-consistently calculates the electric field resulting from M-I coupling. In order to quantitatively evaluate the interplay, we improved the RCM simulations by establishing realistic plasma sheet particle sources, by incorporating it with a modified Dungey force balance magnetic field solver (RCM-Dungey runs), and by adopting more realistic electron loss rates. We found that plasma sheet particle sources strongly affect the shielding of the convection electric field, with a hotter and more tenuous plasma sheet resulting in less shielding than a colder and denser one and thus in more earthward penetration of the plasma sheet. The Harang reversal, which is closely associated with the shielding of the convection electric field and the earthward penetration of low-energy protons, is found to be located at lower latitudes and extend more dawnward for a hotter and more tenuous plasma sheet. In comparison with simulation runs under an empirical but not force balance magnetic field from the Tsyganenko 96 model, the simulation results show that transport under force-balanced magnetic field results in weaker pressure gradients and thus weaker R2 FAC in the near-earth region, weaker shielding of the penetration electric field and, as a result, more earthward penetration of plasma sheet protons and electrons with their inner edges being closer together and more azimuthally symmetric. To evaluate the effect of electron loss rate on ionospheric conductivity, a major contributing factor to M-I coupling, we run RCM-Dungey with a more realistic, MLT dependent electron loss rate established from observed wave activity. Comparing our results with those using a strong diffusion everywhere rate, we found that under the MLT dependent loss rate, the dawn-dusk asymmetry in the precipitating electron energy fluxes agrees better with statistical DMSP observations. The more realistic loss rate is much weaker than the strong diffusion limit in the inner magnetosphere. This allows high-energy electrons in the inner magnetosphere to remain much longer and produce substantial conductivity at lower latitudes. The higher conductivity at lower latitudes under the MLT dependent loss rate results in less efficient shielding in response to an enhanced convection electric field, and thus to deeper penetration of the ion plasma sheet into the inner magnetosphere than under the strong diffusion everywhere rate.

  1. Convective equilibrium and mixing-length theory for stellarator reactors

    SciTech Connect

    Ho, D.D.M.; Kulsrud, R.M.

    1985-09-01

    In high ..beta.. stellarator and tokamak reactors, the plasma pressure gradient in some regions of the plasma may exceed the critical pressure gradient set by ballooning instabilities. In these regions, convective cells break out to enhance the transport. As a result, the pressure gradient can rise only slightly above the critical gradient and the plasma is in another state of equilibrium - ''convective equilibrium'' - in these regions. Although the convective transport cannot be calculated precisely, it is shown that the density and temperature profiles in the convective region can still be estimated. A simple mixing-length theory, similar to that used for convection in stellar interiors, is introduced in this paper to provide a qualitative description of the convective cells and to show that the convective transport is highly efficient. A numerical example for obtaining the density and temperature profiles in a stellarator reactor is given.

  2. Ionospheric chemistry of NO(+)

    NASA Technical Reports Server (NTRS)

    Breig, E. L.; Hanson, W. B.; Hoffman, J. H.

    1984-01-01

    An investigation is described of the behavior of NO(+) in the daytime F region, with basic ion concentration measurements from the Atmosphere Explorer C satellite. The data set was acquired along select orbits at low latitudes and exhibits substantial variations in the NO(+) concentration, both along and between nearby orbits. An excellent consistency is demonstrated between these observations and current chemical equilibrium theory, in contrast to differences that have been reported for the related N2(+) ion. Large variations in the concurrently observed electron temperature permit a relevant comparison between different laboratory determinations of the dissociative recombination rate coefficient. Contributions to the NO(+) production from several secondary sources are also evaluated. Results strengthen the basis for the current theoretical ionospheric chemistry of NO(+) and establish important constraints on resolution of the difficulties with N2(+).

  3. Ionospheric scintillation studies

    NASA Technical Reports Server (NTRS)

    Rino, C. L.; Freemouw, E. J.

    1973-01-01

    The diffracted field of a monochromatic plane wave was characterized by two complex correlation functions. For a Gaussian complex field, these quantities suffice to completely define the statistics of the field. Thus, one can in principle calculate the statistics of any measurable quantity in terms of the model parameters. The best data fits were achieved for intensity statistics derived under the Gaussian statistics hypothesis. The signal structure that achieved the best fit was nearly invariant with scintillation level and irregularity source (ionosphere or solar wind). It was characterized by the fact that more than 80% of the scattered signal power is in phase quadrature with the undeviated or coherent signal component. Thus, the Gaussian-statistics hypothesis is both convenient and accurate for channel modeling work.

  4. Atmosphere–Ionosphere Electrodynamic Coupling

    Microsoft Academic Search

    V. M. Sorokin; V. M. Chmyrev

    \\u000a Numerous phenomena that occur in the mesosphere, ionosphere, and the magnetosphere of the Earth are caused by the sources\\u000a located in the lower atmosphere and on the ground. We describe the effects produced by lightning activity and by ground-based\\u000a transmitters operated in high frequency (HF) and very low frequency (VLF) ranges. Among these phenomena are the ionosphere\\u000a heating and the

  5. Large magnetic storm-induced nighttime ionospheric flows at midlatitudes and their impacts on GPS-based navigation systems

    Microsoft Academic Search

    Su. Basu; S. Basu; E. MacKenzie; P. Doherty; J. W. Wright; F. Rich; M. J. Keskinen; R. E. Sheehan

    2008-01-01

    Analysis of GPS phase fluctuations in conjunction with regional total electron content (TEC) maps, in situ measurements of subauroral polarization streams (SAPS) and auroral convection from several Defense Meteorological Satellite Program spacecraft, and dynasonde measurements at the Bear Lake Observatory obtained during the intense magnetic storm of 7–8 November 2004 have indicated the serious impact of large ionospheric velocities on

  6. Ionospheric magnetic fields at Venus and Mars

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Zhang, T. L.; Woch, J.; Wei, Y.

    2014-04-01

    Mars Global Surveyor (MGS) and Venus Express(VEX) spacecraft have provided us a wealth of insitu observations of characteristics of induced magnetospheres of Mars and Venus at low altitudes during the periods of solar minimum. At such conditions the interplanetary magnetic field (IMF) penetrates deeply inside the ionosphere while the solar wind is terminated at higher altitudes. We present the measurements made by MGS and VEX in the ionospheres of both planets which reveal similar features of the magnetization. The arising magnetic field pattern occurs strongly asymmetrical with respect to the direction of the cross-flow component of the IMF revealing either a sudden straightening of the field lines with a release of the magnetic field stresses or a sudden rotation of the magnetic field vector with a reversal of the sign of the cross-flow component. Such an asymmetrical response is observed at altitudes where the motion of ions and electrons is decoupled and collisional effects become important for generation of the electric currents Asymmetry in the field topology significantly modifies a plasma transport to the night side.

  7. Observations and Simulations of the M-I Coupling of Bursty Convection

    NASA Technical Reports Server (NTRS)

    Sanchez, Ennio R.

    2001-01-01

    The ultimate aim of the project is to establish how much of the magnetotail's total potential is due to flow bursts and how much of this potential maps to the ionosphere. In order to quantify these contributions, we further developed a method to measure the total cross-polar cap potential and the total reconnection rate across the entire polar cap boundary. Then we applied the method to different solar wind-magnetosphere-ionosphere conditions that included substorm periods, storms, and steady magnetospheric convection (SMCs, also known as convection bays) periods. In the following section, we describe in more detail the activities during the second year of this grant.

  8. One-dimensional multispecies magnetohydrodynamic models of the ramside ionosphere of Titan

    NASA Technical Reports Server (NTRS)

    Keller, C. N.; Cravens, T. E.; Gan, L.

    1994-01-01

    The interaction of the Saturnian magnetosphere with the ionosphere of Titan has much in common with the solar wind interaction with nonmagnetic bodies in general. A one-dimensional magnetohydrodynamic model was developed, for radial distances of 1.3 to 2 Titan radii (R(sub T)), to study the dynamics of H2CN(+), C(sub n) H(sub m) (+) (n, m greater than z), C2H5(+), and CH5(+), in the ramside ionosphere of Titan. For the case of a dayside ramside ionosphere (solar zenith angle of 60 degs) we found that the external magnetospheric plasma interacting with Titan's ionosphere produced a very broad region of ionospheric magnetic field whose peak field strength was approximately 26 nT. The ionosphere was magnetized well below the ionospheric peak, allowing ionizing Saturnian magnetospheric electrons access to this region. The sources of ionization and the electron temperature profiles incorporated into the model depend on the relative locations of Titan, Saturn, and the Sun. The calculated electron and ion density profiles as well as the magnetic field profile also depend on the relative positions of Titan, Saturn, and the Sun.

  9. Convection Current

    NSDL National Science Digital Library

    The Exploratorium

    2012-06-26

    In this activity, learners make their own heat waves in an aquarium. Warmer water rising through cooler water creates turbulence effects that bend light, allowing you to project swirling shadows onto a screen. Use this demonstration to show convection currents in water as well as light refraction in a simple, visually appealing way.

  10. Modeling Convection

    ERIC Educational Resources Information Center

    Ebert, James R.; Elliott, Nancy A.; Hurteau, Laura; Schulz, Amanda

    2004-01-01

    Students must understand the fundamental process of convection before they can grasp a wide variety of Earth processes, many of which may seem abstract because of the scales on which they operate. Presentation of a very visual, concrete model prior to instruction on these topics may facilitate students' understanding of processes that are largely…

  11. Long-term Changes in Ionospheric F-layer Characteristics

    NASA Astrophysics Data System (ADS)

    Stamper, R.; Davis, C. J.; Blake, R. M.; Rishbeth, H.

    2006-12-01

    A study of ionospheric sounding data from Slough and Chilton, UK from 1935 to 2005, and from Stanley in the Falkland Islands between 1945 and 2005, revealed long-term and apparently systematic changes in the characteristics of the F1 and F2 layers. Specifically, the visibility of the critical frequency of the ionospheric F1 layer has changed with time, with the trends anti-correlated between the two hemispheres. The relative strengths of the semi-annual and annual variations in the critical frequency of the F2 layer also exhibit strong trends with similar hemispheric anti-correlation. Both effects are attributed to changes in composition driven by the variability in geomagnetic activity which controls the average latitudinal extent of the auroral ovals. The extent of the auroral ovals modulates the latitudinal extent of convection cells transporting molecular-rich air into the upper thermosphere. The anti-correlation between stations is harder to explain and may be due to the relative sensitivity of the ionosphere to changes in the position of the geomagnetic pole at each of the stations.

  12. Ionospheric bending correction for GNSS radio occultation signals

    NASA Astrophysics Data System (ADS)

    Hoque, M. M.; Jakowski, N.

    2011-12-01

    Ionospheric propagation effects on Global Navigation Satellite Systems (GNSS) signals are the most pronounced during radio occultation due to long ionospheric travel paths of the received signal on low Earth orbiting satellites. Inhomogeneous plasma distribution and anisotropy cause higher-order nonlinear refraction effects on GNSS signals which cannot be fully removed through a linear combination of dual-frequency observables. In this paper, higher-order ionospheric effects due to straight line of sight (LOS) propagation assumption such as the excess path length of the signal in addition to the LOS path and the total electron content difference between the curved path and the LOS path have been investigated for selected GPS-CHAMP occultation events. Based on simulation studies we have derived correction formulas for computing raypath bending effects as functions of signal frequency, tangential height of the raypath, ionospheric parameters such as the maximum ionization and total electron content. If these parameters are known, the proposed correction method is able to correct on an average about 65-80% bending errors of GNSS occultation signals.

  13. Lunar ionosphere exploration method using auroral kilometric radiation

    NASA Astrophysics Data System (ADS)

    Goto, Yoshitaka; Fujimoto, Takamasa; Kasahara, Yoshiya; Kumamoto, Atsushi; Ono, Takayuki

    2011-01-01

    The evidence of a lunar ionosphere provided by radio occultation experiments performed by the Soviet spacecraft Luna 19 and 22 has been controversial for the past three decades because the observed large density is difficult to explain theoretically without magnetic shielding from the solar wind. The KAGUYA mission provided an opportunity to investigate the lunar ionosphere with another method. The natural plasma wave receiver (NPW) and waveform capture (WFC) instruments, which are subsystems of the lunar radar sounder (LRS) on board the lunar orbiter KAGUYA, frequently observe auroral kilometric radiation (AKR) propagating from the Earth. The dynamic spectra of the AKR sometimes exhibit a clear interference pattern that is caused by phase differences between direct waves and waves reflected on a lunar surface or a lunar ionosphere if it exists. It was hypothesized that the electron density profiles above the lunar surface could be evaluated by comparing the observed interference pattern with the theoretical interference patterns constructed from the profiles with ray tracing. This method provides a new approach to examining the lunar ionosphere that does not involve the conventional radio occultation technique.

  14. Towards ISO Standard Earth Ionosphere and Plasmasphere Model

    NASA Astrophysics Data System (ADS)

    Bilitza, Dieter; Tamara, Gulyaeva

    2012-07-01

    Space exploration has been identified by several governments as a priority for their space agencies and commercial industry. A good knowledge and specification of the ionosphere and plasmasphere are the key elements necessary to achieve this goal in the design and operation of space vehicles, remote sensing, reliable communication and navigation. The International Standardization Organization, ISO, recommends the International Reference Ionosphere (IRI) for the specification of ionosphere plasma densities and temperatures and lists several plasmasphere models for extending IRI to plasmaspheric altitudes, as described in the ISO Technical Specification, ISO/TS16457:2009. IRI is an international project sponsored jointly by the Committee on Space Research (COSPAR) and the International Union of Radio Science (URSI). The buildup of IRI electron density profile in the bottomside and topside ionosphere and its extension to the plasmasphere are discussed in the paper. We report about the current status of the ISO standardization process for IRI. A Draft International Standard (DIS) document was prepared and circulated widely. Feedback and comments led to the latest revision of the document. We will also present a brief review of IRI-related activities and model status.

  15. New techniques in ground-based ionospheric sounding and studies

    NASA Astrophysics Data System (ADS)

    Reinisch, Bodo W.

    1986-05-01

    Rapid progress in the integrated circuit market has led to new advanced techniques in the remote probing of the ionosphere with HF radio waves. The classical ionosonde which measured virtual height as a function of frequency expanded into a geophysical research tool by measuring all the observables contained in the electromagnetic signals reflected from the ionosphere: amplitude, phase, Doppler, incidence angle, and polarization. A receiving antenna array and high speed digital processing provide the desired spatial and temporal resolution. The current emphasis is on both the on-line and off-line postprocessing of the multiparameter ionogram data to extract the geophysically important ionospheric characteristics: the vertical electron density profiles, horizontal gradients (tilts and waves), plasma drift, the mid-latitude F region trough, and auroral and equatorial spread F. Digital ionosonds deployed in the polar cap and the auroral zone have helped to obtain a better understanding of some of the high-latitude features, and measurements of the equatorial spread F have shown the development and motion of the F region bubbles. HF coherent radar techniques for studying ionospheric irregularity structures measure the velocity of irregularities with scale sizes of one half the radio wavelength. They have mainly been used in the northern auroral zone.

  16. A multi-instrument study of high-latitude ionospheric irregularities and their effects on GPS ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    van der Meeren, Christer; Oksavik, Kjellmar; Moen, Jøran; Romano, Vincenzo

    2013-04-01

    Scintillations are rapid amplitude and phase fluctuations of electromagnetic signals. GNSS-based systems may be disturbed by plasma irregularities and structures such as plasma patches (areas of enhanced electron density) and plasma gradients in the ionosphere. When the GNSS radio signals propagate through such areas, in particular gradients, the signals experience scintillations that at best increases positioning errors and at worst may break the receiver's signal lock, potentially resulting in the GNSS receiver losing track of its position. Due to the importance of many GNSS applications, it is desirable to study the scintillation environment to understand the limitations of the GNSS systems. For this study, GPS receiver scintillation and Total Electron Content (TEC) data from high-latitude locations will be combined with several other data sets, including the EISCAT Svalbard Radar (ESR) and allsky cameras to perform a multi-instrument case study of GPS ionospheric scintillations. The EISCAT data provides a means to determine the altitude and density of the F layer, which can then be used to calibrate allsky projections as well as coordinates of ionospheric piercing points of the GPS signals. The focus will be studying any connection between scintillations and polar cap patches; however, other interesting and related findings will also be presented, herein statistical long-timespan studies of GPS TEC and/or scintillation data.

  17. Understanding Meso- and Micro-scale Coupling of Near Earth Plasmas (Invited)

    NASA Astrophysics Data System (ADS)

    Moore, T. E.; Khazanov, G. V.

    2010-12-01

    Known meso-scale processes include the polar wind and plasmaspheric plumes, consisting mainly of light ions, and generic auroral ionospheric heating processes, which add heavy ion outflows including O+ and atmospheric molecular ions to the light ion outflows. Known micro-scale processes include Alfvén waves propagating into the ionosphere from turbulent magnetospheric boundary layers, current-driven instabilities leading to lower hybrid waves in the auroral acceleration region near 1 Re altitude, and convection and shear driven instabilities along auroral flux tubes, including pick-up ion ring beam relaxation in the topside, and Joule-frictional heating in the F region. Much of the latter is sunk into the neutral gas, leading to observable upwelling features above the auroras. Plasma outflows are observed to be dominated by superthermal (eV to 10's eV) ions that are transversely heated and whose flux rises in a power law relationship to the incident DC and AC Poynting (EM) fluxes and the density of precipitating hot electrons. These facts are thought consistent with lifting of ions by the ambipolar electric field, enhanced by superthermal electron precipitation, combined with heating and-or ponderomotive forcing of the ions by broadband cyclotron frequency range waves. The ambipolar electric field is reasonably well understood, but the source of ion resonant waves is indeterminate and their amplitudes cannot be derived from macroscopic disturbance conditions such as MHD field, current, and plasma conditions. The Outstanding Question in all this is "what are the mechanisms by which solar wind energy flux is dissipated in ionospheric plasmas to produce enhanced outflow?" To answer this question, a new mission is needed to provide a comprehensive picture of ionospheric mass ejection, including: i) detailed observations of the 3D energy-angle distribution of transversely accelerated ions and electrons down to thermal energies of ~0.1 eV; ii) control of plasma sensor potential at the plasma potential; iv) observation of BBELF wavelengths as well as frequencies for mode identification; v) observations of auroral neutral gas upwelling that go beyond recent accelerometer missions. Such a mission should deliver simultaneous conjugate diagnostics from the F region (250-300 km), from the exobase region (500-1300 km), and from the auroral acceleration region (4000-6000 km). Ionospheric observations could be provided by incoherent scatter radar.

  18. HF Radio Wave Production of Artificial Ionospheres

    NASA Astrophysics Data System (ADS)

    Carlson, Herbert

    In 1993 it was predicted that artificial ionospheres would be produced by high power HF radio waves, once HF transmitters approached a GWatt ERP. When that threshold was very recently achieved, such production was indeed detected and published at two high latitude high power HF facilities. Here we review: the first-principles logic behind that prediction, which aspects of such production are critically dependent on magnetic latitude, and which aspects of such production depend only on physical parameters independent of latitude. These distinctions follow directly from decomposition of the problem of ionization production into its components of: radio-wave propagation, wave-particle interactions, electron transport, and quantitative elastic/inelastic cross-sections. We outline this analysis to show that, within the context of early observations, the production of ionization is inevitable, and only a question of competing instability thresholds, and scale of ionization production. This illustrates complimentary aeronomy and plasma physics to advance understanding of both.

  19. Ionospheric flows associated with a transpolar arc

    NASA Technical Reports Server (NTRS)

    Nielsen, E.; Craven, J. D.; Frank, L. A.; Heelis, R. A.

    1990-01-01

    Data on plasma flows associated with a transpolar arc are obtained by combining observations (on January 21, 1982) from the auroral imaging instruments aboard the DE 1 spacecraft with simultaneous observations of ionospheric electron drift velocities obtained with a ground-based coherent radar system and with an ion-drift meter on the DE 2 spacecraft at about 800-km altitude. The combined observations demonstrate that the electron-drift velocities within the transpolar arc at the intersection with the auroral oval on the nightside are directed equatorward into the oval and that the transpolar arc connects to the oval near the Harang discontinuity. It is also shown that the sunward flow along the transpolar arc is present near local noon.

  20. The calculation of ionospheric ray paths 

    E-print Network

    Koehler, Buford Ray

    1967-01-01

    Parabolic ionospheric layer of electrons, altitude versus electron density Page 1- 2 Sample ray paths with constant angle of propagation and increasing frequency, parabolic ionosphere of electrons assumed, earth's magnetic field neglected 1- 3 Sample... ray paths with constant frequency and variable angle of propagation and range, parabolic ionosphere of electrons assumed, earth's magnetic field neglected 2- 1 The vertical and lateral deviations of a radio wave propagated in a plane ionosphere...