These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Plasma convection in the Earth's magnetosphere and ionosphere during substorms  

NASA Astrophysics Data System (ADS)

Existing empirical models of the polar ionospheric plasma convection have been established from different data sets and by use of various methods for their synthesis. They provide us with global statistical convection patterns for variable solar-magnetospheric conditions. However, the existing models are mainly static ones, they do not describe transition processes adequately as, e.g, the convection systems characteristic for each of the four phases of a typical substorm. The empirical model suggested in this paper takes into account such transient processes to describe typical substorm developments. The model is represented by series of 2D maps of the ionospheric electric potential (U) for the different phases of the substorm. The potential patterns were calculated by use of the Magnetogram Inversion Technique (MIT2) for a statistic data set of selected substorms. The criteria of the substorm's timing are given in the paper and compared with the traditional ones. Plots of the open tail magnetic flux (?) and the Pointing vector flux (?') from the solar wind into the magnetosphere (&epsilon'˜?^2) are provided. A few details of substorm development are noted here for the first time. The polar cap potential drop Upc is increasing during the substorm loading stage of about ˜ 1 hour from ˜ 20 kV to ˜ 100 kV, as a linear function of ?. We point to some pecularities of the polar cap electric field increase within the old polar cap region (existing prior to the substorm) and beyond its boundaries, i.e. within the new polar cap region. A rapid increase of the electric field is observed within the new polar cap, while it is retarded within the old polar cap. This means that a shielding process takes place. The shielding was found to be accompanied and/or caused by Region 0 FACs. The details of this process are discussed and compared with Cluster observations.

Förster, M.; Mishin, V. M.; Stauning, P.; Watermann, J.; Bazarzhapov, A. D.; Saifudinova, T. I.

2

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

3

Role of vertical ion convection in the high-latitude ionospheric plasma distribution  

NASA Astrophysics Data System (ADS)

We use the Global Ionosphere-Thermosphere Model (GITM) to simulate the ionospheric reaction to a simple step change of the high-latitude forcing terms during the first hour of electric field enhancement. In response to the enhanced convection electric field, both the convection velocity and Joule heating increase dramatically. The changes in NmF2 present that the tongue extends across the polar cap and the troughs stretch longitudinally. The calculated total electron content (TEC) can vary by 15 TECU and have a similar pattern to the changes of NmF2. The changes in the vertical ion drift can be upward 100 m/s on the dayside and downward 100 m/s on the nightside as a consequence of the changes in the E × B drift. Approximately, hmF2 ascends where ViR is upward and descends where ViR is downward. In general, the response of the ionosphere to the enhanced E-field is that the F2 layer moves upward on the dayside and enhances at all altitudes on the nightside. Below the F2 peak (250 km altitude), the region of decreasing electron density coincides with the upward ViR on the dayside, and the reverse is true on the nightside. Above the F2 peak (450 km altitude), the features related with both horizontal convection and vertical advection are present. The vertical ion drift sets up a vertical circulation in the noon-midnight meridional plane during the early stage of E-field enhancement in addition to the widely accepted horizontal two cell convection. According to the circulation, the significant sources of tongue ionization are not only the plasma from the lower latitudes, but also from the low altitudes on the dayside. While the vertical circulation is not well organized after 6-hour E-field enhancement, the contribution of vertical ion convection is still significant. Although the vertical E × B drift in Apex coordinates is more complex and variable than that in a simple dipole magnetic field, the main characteristics are the same, which indicate the significance of the vertical circulation for the electron density distribution in reality during the early stage of E-field enhancement. The Joule heating drives upwelling of the atmosphere and modifies the O/N2 ratio. Meanwhile, the enhanced neutral advection twists the O/N2 ratio pattern a little bit. However, the changes in the O/N2 ratio have relatively poor correlation with the variation of electron density during the first hour of E-field enhanced time.

Deng, Y.; Ridley, A. J.

2006-09-01

4

Travelling convection vortices in the ionosphere map to the central plasma sheet  

NASA Astrophysics Data System (ADS)

We investigate the magnetospheric domain responsible for the generation of ionospheric travelling convection vortices (TCV) by comparing the location of the TCV to the locations of the low-altitude particle-precipitation boundaries deduced from the DMSP satellite measurements. For three very well documented TCV events we are able to identify suitable satellite passes, in the sense that for each event we can identify two to three passes occurring close to the TCV observation in both time and space. In all three cases the comparisons place the TCV centres at or equatorward of the central plasma sheet/boundary plasma sheet precipitation boundary. Thus our results indicate that the field-aligned currents related to the TCV originate in the plasma sheet rather than at the magnetopause or in the low-latitude boundary layer, as previous studies suggest. Acknowledgements. We gratefully appreciate the on-line DMSP database facility at APL (Newell et al., 1991) from which this study has benefited greatly. We wish to thank E. Friis-Christensen for his encouragement and useful discussions. A. Y. would like to thank the Danish Meteorological Institute, where this work was done, for its hospitality during his stay there and the Nordic Baltic Scholarship Scheme for its financial support of this stay. Topical Editor K.-H. Glassmeier thanks M. J. Engebretson and H. Lühr for their help in evaluating this paper.--> Correspondence to: A. Yahnin-->

Yahnin, A.; Moretto, T.

1996-10-01

5

Plasma convection and auroral precipitation processes associated with the main ionospheric trough at high latitudes  

Microsoft Academic Search

Intervals of F-region electron density depletions associated with the main (mid-latitude) ionospheric trough are studied using latitude scanning experiments with the EISCAT UHF radar. An empirical model predicting the latitude of the trough is proposed. Simultaneous ion drift velocity measurements show that the main trough is a region of strong (more than several hundred meters per second) westward flow, with

P. N. Collis; I. Haggstrom

1988-01-01

6

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

SciTech Connect

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.

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

7

Ionospheric convection associated with discrete levels of particle precipitation  

SciTech Connect

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 precipitation index, and the average patterns keyed to it, provides a means of characterizing the global precipitation and convection patterns throughout an event.

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

1986-07-01

8

Mapping ionospheric convection patterns to the magnetosphere  

SciTech Connect

While convection patterns in the high-latitude ionosphere are usually presented in a corotating frame of reference, those of the magnetosphere are given in inertial coordinates. In the corotating representation the convection throat, which is frequently associated with the cusp, opens between 1000 and 1100MLT. Cusp precipitation, however, centers about noon. The authors find that transforming the convection patterns of Heppner and Maynard (hereinafter H-M) into inertial coordinates aligns the throat region with local noon. The authors present projections of the H-M patterns to the magnetosphere in both corotating and inertial coordinates using the field model of Tsyganenko. In inertial coordinates the mapped H-M convection throat opens at noon. Consistent with predictions of the Rice convection model for magnetospheric electric fields late in the substorm cycle, only a small fraction of the equipotential contours penetrate to the subsolar region. This suggests that a significant portion of flux tube merging occurs on magnetic field lines whose equatorial mapping is on the flanks of the magnetosphere. Nonconjugacy between the mapping of H-M patterns for both positive and negative interplanetary magnetic field by Bgamma, especially in the 1400-1600 LT sector, may explain the Bgamma dependence of the electron precipitation `hot spot` discovered by Evans. A separate lobe cell is not required to explain the central equipotential contours of the large convection cell.

Maynard, N.C.; Denig, W.F.; Burke, W.J.

1995-02-01

9

Mapping ionospheric convection patterns to the magnetosphere  

NASA Astrophysics Data System (ADS)

While convection patterns in the high-latitude ionosphere are usually presented in a corotating frame of reference, those of the magnetosphere are given in inertial coordinates. In the corotating representation the convection throat, which is frequently associated with the cusp, opens between 1000 and 1100 MLT. Cusp precipitation, however, centers about noon. We find that transforming the convection patterns of Heppner and Maynard (1987) (hereinafter H-M) into inertial coordinates aligns the throat region with local noon. We present projections of the H-M patterns to the magnetosphere in both corotating and inertial coordinates using the magnetic field model of Tsyganenko (1989). In inertial coordinates the mapped H-M convection throat opens at noon. Consistent with predictions of the Rice convection model for magnetospheric electric fields late in the substorm cycle, only a small fraction of the equipotential contours penetrate to the subsolar region. This suggests that a significant portion of flux tube merging occurs on magnetic field lines whose equatorial mapping is on the flanks of the magnetosphere. Nonconjugacy between the mapping of H-M patterns for both positive and negative interplanetary magnetic field B(sub Y), especially in the 1400-1600 LT sector, may explain the B(sub Y) dependence of the electron precipitation 'hot spot' discovered by Evans (1985). A separate lobe cell is not required to explain the central, equipotential contours of the large convection cell.

Maynard, Nelson C.; Denig, William F.; Burke, William J.

1995-02-01

10

Mapping ionospheric convection patterns to the magnetosphere  

SciTech Connect

While convection patterns in the high-latitude ionosphere are usually presented in a corotating frame of reference, those of the magnetosphere are given in inertial coordinates. In the corotating representation the convection throat, which is frequently associated with the cusp, opens between 1000 and 1100 MLT. Cusp precipitation, however, centers about noon. The authors find that transforming the convection patterns of Heppner and Maynard (hereinafter H-M) into inertial coordinates aligns the throat region with local noon. They present projections of the H-M patterns to the magnetosphere in both corotating and inertial coordinates using the magnetic field model of Tsyganenko. In inertial coordinates the mapped H-M convection throat opens at noon. Consistent with predictions of the Rice convection model for magnetospheric electric fields late in the substorm cycle, only a small fraction of the equipotential contours penetrate to the subsolar region. This suggests that a significant portion of flux tube merging occurs on magnetic field lines whose equatorial mapping is on the flanks of the magnetosphere. Nonconjugacy between the mapping of H-M patterns for both positive and negative interplanetary magnetic field B{sub Y}, especially in the 1400-1600 LT sector, may explain the B{sub Y} dependence of the electron precipitation {open_quotes}hot spot{close_quotes} discovered by Evans. A separate lobe cell is not required to explain the central, equipotential contours of the large convection cell. 31 refs., 3 figs.

Maynard, N.C.; Denig, W.F.; Burke, W.J. [Hanscom Air Force Base, MA (United States)] [Hanscom Air Force Base, MA (United States)

1995-02-01

11

Global-scale observations of ionospheric convection during geomagnetic storms  

NASA Astrophysics Data System (ADS)

The global effects on the ionosphere during periods of intense geomagnetic activity associated with geomagnetic storms are investigated using the Super Dual Auroral Radar Network (SuperDARN). The influence of the main and recovery phases of geomagnetic storms on ionospheric properties such as backscatter occurrence rates, velocity distributions, and convection patterns are presented. The evolution of magnetosphere and ionosphere parameters during the storms did not depend on the origin of the storm (e.g., a coronal mass ejection or a corotating interaction region). Instead, there was a continuum of response to the intensity of the driver. For example, we found a clear relationship between the most negative value of the southward component of the interplanetary magnetic field (IMF Bz) and the most negative value of the Sym-H index, which marks the end of the main phase of a storm. This is one of the first superposed epoch studies that analyzes the sunward/antisunward line-of-sight velocity as a function of magnetic local time for geomagnetic storms of various intensities. In the noon sector, before and during the main phase of the storms, the SuperDARN radars recorded faster antisunward ionospheric plasma drifts together with a significant increase in the number of ionospheric echoes. This is consistent with the expected increase in soft particle precipitation in the noon sector and with the reconnection electric field that occurs when the IMF Bz is strongly negative, as is the case during the main phase of storms. The SuperDARN echo occurrence in the noon sector returned to prestorm values early in the recovery phase. The overall response was similar in the midnight sector, except that the peak echo occurrence for the most intense storms was limited to a narrower time interval centered on the end of the main phase. There were reductions in the strong antisunward flows near local midnight observed during the main phase and early in the recovery phase, particularly for the intense storm class. Strong electric fields are applied in the nightside ionosphere during storms, and the decameter structures from which SuperDARN scatter are more easily produced. However, in regions of energetic auroral precipitation and after a long exposure to strong electric fields, there is often a reduction in SuperDARN echoes due to absorption or changes in radio wave propagation.

Gillies, D. M.; McWilliams, K. A.; St. Maurice, J.-P.; Milan, S. E.

2011-12-01

12

Ionospheric convection at Casey, a southern polar cap station  

NASA Astrophysics Data System (ADS)

A digital ionosonde (Digisonde Portable Sounder 4) located at Casey, Antarctica (66.3°S, 110.5°E, -80.8° corrected geomagnetic latitude) has been operational since early 1993 and has accumulated 3 years of plasma drift measurements, providing an excellent data set for studying the characteristics of ionospheric convection flow at a southern polar cap station. The purpose of this study is to investigate the influence of the IMF on the F region ionospheric convection over Casey and to compare it to the Heppner-Maynard satellite-derived electric field models. We find clear dependencies in the drift on the sign and strength of the IMF By and Bz components and with Kp. Antisunward flow dominates during Bz south conditions, turning to have a sunward component around noon when Bz is northward. The By component causes the entire convection system to rotate and distorts the dayside flow in the proximity of the throat, with a dawnward (duskward) component for By negative (positive). Comparison with the Bz south Heppner-Maynard BC, DE, and A patterns is favorable at most times, although we predict a rounder, more dominant dusk (dawn) cell and a smaller crescent-shaped dawn (dusk) cell for By<0 (By>0). There is a dependence on Kp when Bz is south in both the model and the drifts, flow directions becoming more antisunward and velocities becoming higher on the dayside as Kp increases. This implies the polar cap is expanding under conditions of enhanced reconnection. When Bz is north, the F region drift agreement with the BCP(P) and DEP(P) models is excellent on the dawn (dusk) side for By<0 (By>0) but diverges on the opposite side as the pattern flow lines twist sunward. Separation of the drifts into Bz weakly (<3nT) and strongly (>3nT) northward cases did not reveal any appreciable difference in the observed drift velocities.

Smith, P. R.; Dyson, P. L.; Monselesan, D. P.; Morris, R. J.

1998-02-01

13

Ionospheric convection during different phases of magnetospheric substorms  

NASA Technical Reports Server (NTRS)

Observations of ionospheric convection flows at a range of local times during the various phases of the substorm cycle are reported on with the aim of investigating the convection behavior during a range of times and phases. The ionospheric flow observations are from the EISCAT and DMSP satellites. The substorm phases are identified from energetic particle measurements from geosynchronous satellites. The growth phase convection indicates an initial expansion of the polar cap. There is an unexplained poleward motion of the flow reversal boundary (FRB). It is concluded that this motion does not necessarily provide a true representation of the balance between reconnection at the dayside and in the tail. The expansion phase flows do not show any evidence for tail reconnection until late in the phase. The convection during the recovery phase is indicative of tail reconnection as there is evidence that there is only a lobe cell driving convection on the dayside.

Lester, M.; Fox, N. J.; Reeves, G. D.; Hairston, M.

1996-01-01

14

Ionospheric Control of the Distribution of Magnetospheric Reconnection and Convection  

NASA Astrophysics Data System (ADS)

Observations reveal that for southward interplanetary magnetic field conditions the two-cell convection pattern in Earth's ionosphere rotates clockwise relative to the sun-earth line (when viewed from above the pole) with more magnetic flux circulating in the dusk convection cell than in the dawn cell. For the same interplanetary conditions, the nightside magnetosphere exhibits enhanced magnetic reconnection along the premidnight x-line with fast exhaust flows developing in channels in the premidnight plasmasheet. These asymmetries have been investigated extensively in isolation and essentially as independent phenomena. It is shown here for the first time that they are actually different manifestations of the same coupled process. Global simulations of the magnetosphere-ionosphere interaction and simple physical considerations show that the observed asymmetries are a consequence of meridional gradients in the ionospheric Hall conductance. Causal relationships are demonstrated through a series of controlled numerical experiments which would be practically impossible to tease-out observationally.

Zhang, B.; Smith, R. H.; Brambles, O.; Lotko, W.; Ouellette, J.; Lyon, J.; Haerendel, G.

2012-12-01

15

In situ observations of bifurcation of equatorial ionospheric plasma depletions  

SciTech Connect

Vector electric field measurements from the San Marco D satellite are utilized to investigate the bifurcation of ionospheric plasma depletions (sometimes called {open_quotes}bubbles{close_quotes}) associated with nightside equatorial spread F. These depletions are identified by enhanced upward ExB convection in depleted plasma density channels in the nighttime equatorial ionosphere. The in situ determination of the bifurcation process is based on dc electric field measurements of the bipolar variation in the zonal flow, westward and eastward, as the eastbound satellite crosses isolated signatures of updrafting plasma depletion regions. The authors also present data in which more complicated regions of zonal velocity variations appear as the possible result of multiple bifurcations of updrafting equatorial plasma bubbles. 10 refs., 7 fig.

Aggson, T.L.; Pfaff, R.F. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)] [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Maynard, N.C. [Mission Research Corporation, Nashua, NH (United States)] [Mission Research Corporation, Nashua, NH (United States)

1996-03-01

16

Role of Ionospheric Plasmas in Earth's Magnetotail  

NASA Technical Reports Server (NTRS)

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.

Moore, Thomas E.

2007-01-01

17

Plasma density features associated with strong convection in the winter high-latitude F region  

NASA Technical Reports Server (NTRS)

A single plasma convection model was combined with an ionospheric-atmospheric composition model to study plasma density features associated with string convection in the winter high-latitude F region. Time dependent, three-dimensional, ion density distributions for NO(+), O2(+), N2(+), O(+) and He(+) were produced, and the ionosphere above 42 deg N magnetic latitude was covered for 24 hours. The study found that for strong and weak convection, electron density exhibited a variation with altitude, latitude, longitude and universal time. Ionospheric features were evident for strong convection, but modified in comparison with those found for slow convection. Also found for strong convection was a more pronounced tongue of ionization, the appearance of a new polar hole in the polar cap, and a midlatitude electron density trough that was not as deep as found for a weak convection. In addition, good agreement was found between predictions and Atmosphere Explorer measurements of ion composition variation with latitude and local time.

Sojka, J. J.; Raitt, W. J.; Schunk, R. W.

1981-01-01

18

Ionospheric convection during the magnetic storm of 20-21 March 1991  

NASA Technical Reports Server (NTRS)

We report on the response of high-latitude ionospheric convection during the magnetic storm of March 20-21 1990. IMP-8 measurements of solar wind plasma and interplanetary magnetic field (IMF), ionospheric convection flow measurements from the Wick and Goose Bay coherent radars, EISCAT, Millstone Hill and Sondrestorm incoherent radars and three digisondes at Millstone Hill, Goose Bay and Qaanaaq are presented. Two intervals of particular interest have been indentified. The first starts with a storm sudden commencement at 2243 UT on March 20 and includes the ionospheric activity in the following 7 h. The response time of the ionospheric convection to the southward tuning of the IMF in the dusk to midnight local times is found to be approximately half that measured in a similar study at comparable local times during more normal solar wind conditions. A subsequent reconfiguration of the nightside convection pattern was also observed, although it was not possible to distinguish between effects due to possible changes in B(sub y) and effects due to substorm activity. The second interval, 1200-2100 UT 21 March 1990, included a southward turning of the IMF which resulted in the B(sub z) component becoming -10 nT. The response time on the dayside to this change in the IMF at the magnetopause was approximately 15 min to 30 min which is a factor of approximately 2 greater than those previously measured at higher latitudes. A movement of the nightside flow reversal, possibly driven by current systems associated with the substorm expansion phases, was observed, implying that the nightside convection pattern can be dominated by substorm activity.

Taylor, J. R.; Yeoman, T. K.; Lester, M.; Buonsanto, M. J.; Scali, J. L.; Ruohoniemi, J. M.; Kelly, J. D.

1994-01-01

19

Plasmapause morphology determined from an empirical ionospheric convection model  

NASA Astrophysics Data System (ADS)

Results are examined of mapping the convection electric potential at ionospheric heights, as derived from empirical ionospheric convection models, to the equatorial plane in the magnetosphere where it is added to the earth's rotational potential. The sensitivity of plasmapause shape and size derived in this way was studied by varying the z and y components of the IMF and the geomagnetic activity index. Results show that the model of Heppner and Maynard (1987) produces plasmasphere morphology that is broadly consistent with prior ground-based and satellite measurements of plasmapause position. It is shown that the largest change in the characteristic shape of the plasmapause is due to the direction of IMF Bz; for IMF Bz southward, the plasmapause is circular, while a broad oval plasmapause is found for IMF Bz northward. The ability of this model to reproduce the Lpp-LT shape of the plasmapause shows that empirical ionospheric convection models can be extended to provide a useful method to determine plasmapause location for a variety of steady geomagnetic conditions.

Doe, Richard A.; Moldwin, Mark B.; Mendillo, Michael

1992-02-01

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

21

Ground-based studies of ionospheric convection associated with substorm expansion  

NASA Technical Reports Server (NTRS)

The instantaneous patterns of electric fields and currents in the high-latitude ionosphere are deduced by combining satellite and radar measurements of the ionospheric drift velocity, along with ground-based magnetometer observations for October 25, 1981. The period under study was characterized by a relatively stable southward interplanetary magnetic field (IMF), so that the obtained electric field patterns do reflect, in general, the state of sustained and enhanced plasma convection in the magnetosphere. During one of the satellite passes, however, an intense westward electrojet caused by a substorm intruded into the satellite (DE2) and radar (Chatanika, Alaska) field of view in the premidnight sector, providing a unique opportunity to differentiate the enhanced convection and substorm expansion fields. The distributions of the calculated electric potential for the expansion and maximum phases of the substorm show the first clear evidence of the coexistence of two physically different systems in the global convection pattern. The changes in the convection pattern during the substorm indicate that the large-scale potential distributions are indeed of general two-cell patterns representing the southward IMF status, but the night-morning cell has two positive peaks, one in the midnight sector and the other in the late morning hours, corresponding to the substorm expansion and the convection enhancement, respectively.

Kamide, Y.; Richmond, A. D.; Emery, B. A.; Hutchins, C. F.; Ahn, B.-H.; De La Beaujardiere, O.; Foster, J. C.; Heelis, R. A.; Kroehl, H. W.; Rich, F. J.

1994-01-01

22

Plasma Interactions in Titan's Ionosphere  

E-print Network

calculations of the thermal electron population (electrons with energies less than 2 eV), and chemical reactions in the ionosphere. The results of these models will be compared to data collected by instruments aboard Cassini. Modeled ion production rates...

Richard, Matthew

2013-05-31

23

Ionosphere-magnetosphere coupling. I - Thermal plasma  

NASA Technical Reports Server (NTRS)

The complex interaction of the cold plasma of the plasmasphere and ionosphere with the hot plasma of the ring current and the plasma sheet is studied. It is seen that a coupling, probably through wave particle interactions, exists which seems to have a strong influence on the temperature of the plasma of the outer plasmasphere and on the detailed dynamics of the bulge region, especially the formation of detached plasma regions or plasma tails. Also, there is evidence that the outer plasmasphere may display very high temperatures, and that detached plasma regions are closely associated with ring current injections.

Chappell, C. R.

1975-01-01

24

Venus' nighttime horizontal plasma flow, 'magnetic congestion', and ionospheric hole production  

NASA Technical Reports Server (NTRS)

A simple rectilinear, two-dimensional MHD model is used to investigate the effects of field-aligned plasma loss and cooling on a dense plasma convecting across a weak magnetic field, in order to illumine the Venus nighttime phenomena of horizontal plasma flow, magnetic congestion and ionospheric hole production. By parameterizing field-aligned variations and explicitly solving for cross magnetic field variations, it is shown that the abrupt horizontal enhancements of the vertical magnetic field, as well as sudden decreases of the plasma density to very low values (which are characteristic of ionospheric holes), can be produced in the presence of field-aligned losses.

Grebowsky, J. M.; Mayr, H. G.; Curtis, S. A.; Taylor, H. A., Jr.

1983-01-01

25

Interhemispheric asymmetry of the high-latitude ionospheric convection pattern  

NASA Technical Reports Server (NTRS)

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.

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

26

Magnetotail-Ionosphere Coupling in a Steady Magnetospheric Convection Flow Brake  

NASA Astrophysics Data System (ADS)

The interaction between the magnetotail and ionosphere in a region of reconnection flow braking is analyzed in a global (LFM) MHD simulation. The simulation includes electrostatic coupling at the low-altitude simulation boundary using the ionospheric Ohm’s law, current continuity, mapping of field-aligned current through the MI gap region with allowance for a field-aligned potential drop, and the effects of electron precipitation using the Knight-Fridman-Lemaire formulation for the number and energy fluxes of precipitating electrons in the Robinson et al (1987) empirical relations for dependence of Pedersen and Hall conductances on auroral precipitation. The simulation is driven by constant SW/IMF conditions with Vsw = 400 km/s, Nsw = 5/cc, and Bz = - 10 nT. It settles into a quasi-stationary, steady magnetospheric convection (SMC) state after an initiating substorm. The magnetotail and braking of the reconnection flow in the SMC state exhibit significant dawn-dusk asymmetry due to the interaction with the ionosphere, which also exhibits dawn-dusk asymmetry due to the effects of intense electron precipitation in the pre-midnight region of upward field-aligned current. These strong asymmetries in the magnetosphere and ionosphere disappear when the ionospheric Hall conductance is treated as constant. The electromagnetic dynamo (local magnetotail Jy < 0) produced by braking of the more intense, duskside reconnection flow powers ionospheric Joule dissipation in a pre-midnight (Bostrom) Type 1 auroral current circuit, which develops at the poleward edge of the conductance gradient in the nightside convection throat. Hall currents are diverted into field-aligned currents in this region as the convection streamlines begin to turn sunward (see figure). Hall currents also connect these field-aligned currents to the R2 current dynamo that projects from the inner magnetosphere to lower latitudes. Large Alfvénic Poynting fluxes flow into the premidnight auroral zone from the simulated SMC flow brake, with a time-average pattern resembling statistical patterns from Polar satellite data (Keiling et al, 2003) and FAST satellite data (Chaston et al, 2003). Intense Alfvénic aurora is expected in these regions. Synthetic satellite data in and around the time-variable flow brake resemble observed bursty bulk flows (BBFs) in some regions, but the intense SMC flow is more regular and persistent than is typical of BBFs. Nightside equatorial plasmasheet with flow vectors, plasma pressure contours (yellow) and Bz = 0 contour (white) overlaid on j.E in color. (Right) Ionosphere with potential contours overlaid on field-aligned current in color. Braking of duskside BBF near (x,y) = (-13, 3) RE is evident.

Lotko, W.; Zhang, B.; Brambles, O. J.

2010-12-01

27

Plasmapause morphology determined from an empirical ionospheric convection model  

SciTech Connect

The steady-state electric potentials derived from empirical ionospheric convection models were mapped to the magnetospheric equatorial plane and added to the Earth's rotational field to examine the local time dependence of the plasmapause radius. The last closed equipotential line was assumed to be the plasmapause. The sensitivity of plasmapause shape and size derived in this way was studied by varying the z and y components of the interplanetary magnetic field (IMF) and the geomagnetic activity index Kp. Results show that the Heppner and Maynard model produces plasmasphere morphology that is broadly consistent with prior ground-based and satellite measurements of plasmapause position. The model results show that the largest change in the characteristic shape of the plasmapause is due to the direction of IMF B{sub z}; for IMF B{sub z} southward, the plasmapause is circular, while a broad oval plasmapause (with a bulge at 2100 UT) is found for IMF B{sub z} northward. The ability of the model to reproduce the L{sub pp}-LT shape of the plasmapause as found by previous observations shows that empirical ionospheric convection models can be extended to provide a useful method to determine plasmapause location for variety of steady geomagnetic conditions.

Doe, R.A.; Moldwin, M.B.; Mendillo, M. (Boston Univ., MA (United States))

1992-02-01

28

Modelling of plasma injection and polarization jet in the inner magnetosphere using self-consistent electric field model and ionospheric conductivity model, modified by strong electric field  

Microsoft Academic Search

Polarization Jet (PJ) is a narrow strip of fast westward plasma convection (1-5 km\\/sec at ionosphere altitudes) in the evening sector of the inner magnetosphere \\/ionosphere (often just inside the plasmapause location). PJ is associated with substorm particle injections, but its origin is still not fully explained. PJ phenomena is a strike example of ionosphere-magnetosphere coupling, because in the ionosphere

V. Vovchenko; N. Buzulukova; L. Zinin; V. Khalipov

2004-01-01

29

Dynamic interactions between ionospheric plasma and spacecraft  

NASA Technical Reports Server (NTRS)

Studies of the interactions between the Space Station Freedom and ionospheric plasma led to an improved understanding of the dynamics of these interactions. Some of the issues related to developing and sustaining arcs in ionospheric conditions are considered. A technique for the estimation of the amplitude and duration of arcs is presented. The technique uses the capacitance of the system to estimate the peak current and then uses the charge stored to estimate the arc duration. As new technologies are implemented on spacecraft, new environmental compatibility issues will arise. Some of the issues related to driving dielectric surfaces with alternating current voltages are considered. The steady state charging criteria is that over an oscillation, the ion charge collected is compensated for by the electron charge collected. This tends to drive the average potential negative so that the dielectric surface is positive for only a small portion of the cycle.

Snyder, David B.

1995-01-01

30

Response of ionospheric convection to changes in the interplanetary magnetic field: Lessons from a MHD simulation  

NASA Astrophysics Data System (ADS)

Characteristics of magnetospheric and high-latitude ionospheric convection pattern responses to abrupt changes in the interplanetary magnetic field (IMF) orientation have been investigated using an MHD model with a step function reversal of IMF polarity (positive to negative BY) in otherwise steady solar wind conditions. By examining model outputs at 1 min intervals, we have tracked the evolution of the IMF polarity reversal through the magnetosphere, with particular attention to changes in the ionosphere and at the magnetopause. For discussion, times are referenced relative to the time of first contact (t=0) of the IMF reversal with the subsolar nose of the magnetopause at ~10.5 RE. The linear change in large-scale ionospheric convection pattern begins at t=8min, reproducing the difference pattern results of Ridley et al. [1997, 1998]. Field-aligned current difference patterns, similarly derived, show an initial two-cell pattern earlier, at t=4min. The current difference two-cell pattern grows slowly at first, then faster as the potential pattern begins to change. The first magnetic response to the impact of the abrupt IMF transition at the magnetopause nose is to reverse the tilt of the last-closed field lines and of the ``first''-open field lines. This change in tilt occurs within the boundary layer before merging of IMF with closed magnetospheric field lines starts. In the case of steady state IMF BY, IMF field lines undergo merging or ``changing partners'' with other IMF field lines, as they approach the nose and tilt in response to currents. When the BY reversal approaches the magnetopause nose, IMF field lines from behind the reversal overtake and merge with those in front of the reversal, thus puncturing the reversal front and uncoupling the layer of solar wind plasma in the reversal zone from the magnetosphere. The uncoupled layer propagates tailward entirely within the magnetosheath. Merging of closed magnetospheric field lines with the new polarity IMF begins at t=3min and starts to affect local currents near the cusp 1 min later. While merging starts early and controls the addition of open flux to the polar cap, large-scale convection pattern changes are tied to the currents, which are controlled in the boundary layers. The resulting convection pattern is an amalgamation of these diverse responses. These results support the conclusion of Maynard et al. [2001b], that the small convection cell is driven from the opposite hemisphere in BY-dominated situations.

Maynard, N. C.; Siscoe, G. L.; Sonnerup, B. U. Ö.; White, W. W.; Siebert, K. D.; Weimer, D. R.; Erickson, G. M.; Schoendorf, J. A.; Ober, D. M.; Wilson, G. R.

2001-10-01

31

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

NASA Astrophysics Data System (ADS)

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.

Lotko, W.

2007-03-01

32

Explosive plasma releases in the earth's ionosphere  

NASA Technical Reports Server (NTRS)

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.

Kintner, P. M.

1982-01-01

33

Global MHD modeling of ionospheric convection and field-aligned currents associated with IMF By triggered theta auroras  

NASA Astrophysics Data System (ADS)

numerical magnetohydrodynamic simulations, we investigate the evolution of ionospheric convection and field-aligned currents (FACs) when ? auroras are formed in response to interplanetary magnetic field (IMF) By transitions. When the polarity of IMF By switches abruptly during northward IMF periods, the crossbar of the ? aurora is isolated from the flankside auroral oval and drifts into the polar cap. This drift motion is involved in a large round cell associated with new IMF By, with sunward convection residing only on the dayside tip of the crossbar. There exists an IMF By-controlled large-scale FAC system on the crossbar. When the ? aurora is drifting duskward (dawnward), the FACs are located on the dawnside (duskside) boundary of the crossbar adjacent to the "new" lobe. In contrast, the magnetospheric source region of the crossbar FAC system is located on the duskside (dawnside) boundary of the protruded plasma sheet adjacent to the "old" lobe. In the source region, plasma thermal pressure feeds the electromagnetic energy of FACs, and these processes can be interpreted as coupling of slow mode and Alfvén mode disturbances. In the ionosphere, the crossbar-associated FACs close with part of the region 1 currents associated with the new crescent cell. The magnetospheric source of that part of the region 1 FACs is located on the plasma sheet boundary and the magnetopause both adjacent to the new lobe. Dynamo processes in the old-lobe side and the new-lobe side work together to drive the ionospheric drift motion of the crossbar.

Watanabe, Masakazu; Sakito, Shintaro; Tanaka, Takashi; Shinagawa, Hiroyuki; Murata, Ken T.

2014-08-01

34

Plasma bubble phenomenon in the topside ionosphere  

NASA Astrophysics Data System (ADS)

There are the indications that plasma bubbles/flux tube aligned plasma density depletions, produced by Rayleigh-Taylor instability at the bottomside of ionosphere, could rise up to the topside ionosphere and plasmasphere. Maruyama and Matuura [Maruyama, T., Matuura, N. Longitudinal variability of annual changes in activity of equatorial spread-F and plasma bubbles. J. Geophys. Res. 89(A12), 10903-10912, 1984.], using ISS-b satellite data for the high solar activity period, 1978-1979, have seen the plasma bubbles over equator at 1100 km altitudes in 46 cases in 1700 passes. That is ˜3% only. However, there is distinctly another picture in He + density depletions (subtroughs) according to the ISS-b data for the same period. He + density subtroughs were observed in the topside ionosphere over equatorial and low-latitudinal regions ( L ˜ 1.3-3) in 11% of the cases [Karpachev, A.T., Sidorova, L.N. Occurrence probability of the light ion trough and subtrough in He + density on season and local time. Adv. Space Res. 29, 999-108, 2002; Sidorova, L.N., He + density topside modeling based on ISS-b satellite data. Adv. Space Res. 33, 850-854, 2004.]. We have carried out a statistical study of the He + density subtrough characteristics. 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 the AE-E satellite and IS radar (Jicamarca) data. Striking similarity in development dynamics is revealed for the different seasons. It is noted also that the He + density subtroughs are mostly observed in the evening-night sector (18-05 LT) from October till May, which is very similar to the peculiarities of the equatorial spread-F (ESF), usually associated with plasma bubbles. 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 et al. [Abdu, M.A., Sobral, J.H.A., Batista, I.S. Equatorial spread-F statistics in the american longitudes: some problems relevant to ESF description in the IRI scheme. Adv. Space Res. 25, 113-124, 2000.] from ground-based ionograms obtained over Brazilian region for the same years. The comparison shows good enough correlation ( R ˜ 0.67). It is concluded that: (a) He + density subtroughs like ESF are controlled by pre-reversal enhancement electric field (vertical drift); (b) He + density subtroughs and ESF/bubble irregularities may be considered as phenomena of the same plasma bubble origin; (c) it seems, plasma bubbles, reaching the topside ionosphere altitudes, are most easily observable in He + density as depletions.

Sidorova, L. N.

35

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

NASA Technical Reports Server (NTRS)

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.

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

36

Magnetospheric and ionospheric plasmas; Proceedings of the Ninth Symposium and Topical Meeting, Graz, Austria, June 25-July 7, 1984  

NASA Technical Reports Server (NTRS)

Papers are presented on the physics of the magnetosphere-ionosphere connection, with attention given to theory and modeling, auroras, plasma dynamics and irregularities, waves and electron beams, the dynamics of the thermosphere, and planetary plasmas. Plasma circulation in the magnetosphere is also discussed; consideration is given to observations of magnetospheric convection from low altitudes, the structure and properties of the earth's plasmasphere, and the circulation of energetic ions of terrestrial origin in the magnetosphere.

Schmerling, E. R. (editor); Cowley, S. W. H. (editor); Reiff, P. H. (editor)

1985-01-01

37

Intense spreading of radar echoes from ionospheric plasmas  

E-print Network

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 ...

Dorfman, Seth E

2005-01-01

38

Modeling the observed proton aurora and ionospheric convection responses to changes in the IMF clock angle: 2. Persistence of ionospheric convection  

NASA Astrophysics Data System (ADS)

We apply a numerical model of time-dependent ionospheric convection to two directly driven reconnection pulses during a 15-min interval of southward IMF on 26 November 2000. The model requires an input magnetopause reconnection rate variation, which is here derived from the observed variation in the upstream IMF clock angle, ?. The reconnection rate is mapped to an ionospheric merging gap, the MLT extent of which is inferred from the Doppler-shifted Lyman-? emission on newly opened field lines, as observed by the FUV instrument on the IMAGE spacecraft. The model is used to reproduce a variety of features observed during this event: SuperDARN observations of the ionospheric convection pattern and transpolar voltage; FUV observations of the growth of patches of newly opened flux; FUV and in situ observations of the location of the Open-Closed field line Boundary (OCB) and a cusp ion step. We adopt a clock angle dependence of the magnetopause reconnection electric field, mapped to the ionosphere, of the form Enosin4(?/2) and estimate the peak value, Eno, by matching observed and modeled variations of both the latitude, ?OCB, of the dayside OCB (as inferred from the equatorward edge of cusp proton emissions seen by FUV) and the transpolar voltage ?PC (as derived using the mapped potential technique from SuperDARN HF radar data). This analysis also yields the time constant ?OCB with which the open-closed boundary relaxes back toward its equilibrium configuration. For the case studied here, we find ?OCB = 9.7 ± 1.3 min, consistent with previous inferences from the observed response of ionospheric flow to southward turnings of the IMF. The analysis confirms quantitatively the concepts of ionospheric flow excitation on which the model is based and explains some otherwise anomalous features of the cusp precipitation morphology.

Lockwood, M.; Lanchester, B. S.; Morley, S. K.; Throp, K.; Milan, S. E.; Lester, M.; Frey, H. U.

2006-02-01

39

Plasma temperatures in Saturn's ionosphere Luke Moore,1  

E-print Network

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

Mendillo, Michael

40

Morphology of meteoric plasma layers in the ionosphere of Mars  

E-print Network

Morphology of meteoric plasma layers in the ionosphere of Mars as observed by the Mars Global Radio Science data #12;Meteoric Plasma Layer EUV layer X-ray layer Meteoric layer Layer at 90 km Observations · 71 meteoric plasma layers in 5600 MGS profiles 5217R00A 4353T31A 3176Q39A 0350E42B #12

Withers, Paul

41

Modeling the observed proton aurora and ionospheric convection responses to changes in the IMF clock angle  

E-print Network

Modeling the observed proton aurora and ionospheric convection responses to changes in the IMF clock angle: 1. Persistence of cusp proton aurora K. Throp, M. Lockwood,1 B. S. Lanchester, and S. K employ a numerical model of cusp ion precipitation and proton aurora emission to fit variations

Lockwood, Mike

42

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

Microsoft Academic Search

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

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

2007-01-01

43

Interhemispheric conjugate observations of ionospheric convection flows in the dayside high-latitude regions  

NASA Astrophysics Data System (ADS)

Interhemispheric conjugate observations of ionospheric convection flows are essential for understanding the electrodynamics in the dayside high-latitude regions, particularly in the cusp and the open/closed field line boundary region. We investigate the SuperDARN data for this purpose. Merged vectors obtained from pairs of radars are calculated using the common program data during the 8-year period of 1995-2002. We select 29 events in which a large number of merged vectors are obtained by coverage of pairs of conjugate radars. Most events occurred near equinox under the southward IMF conditions. This is consistent with a fact that the generation of ionospheric irregularities is affected by daylight high diffusion rates and enhancements of convection electric field. Interhemispheric convection patterns are consistent with the Heppner-Maynard pattern when the IMF is stable for >30 min. It is found that convection flows and vorticities tend to be weak in the sunlit region in the vicinity of the open/closed field line boundary. This may reflect an asymmetry of the cusp properties in the northern and southern hemispheres due to ionospheric conductivity differences. Considering these result, we discuss the three dimensional current system producing the interhemispheric convection patterns in the dayside high-latitude region.

Kataoka, R.; Fukunishi, H.; Hosokawa, K.; Yukimatu, A. S.; Sato, N.

2003-12-01

44

Investigating the Importance of Viscous Interactions on Ionospheric Convection via Comparisons of Open-Closed Boundaries (OCBs) and Convection Reversal Boundaries (CRBs)  

NASA Astrophysics Data System (ADS)

Geomagnetic storms cause large global disturbances in the Earth's magnetosphere, during which large amounts of energy are deposited in the magnetotail and inner magnetosphere, producing an enhanced ring current and energising plasma to relativistic levels by poorly-understood excitation mechanisms. A previous study by Hutchinson et al. [2011] identified 143 geomagnetic storms over the last solar cycle (1997-2008) from the global SYM-H index and associated solar wind (SW) data from the Advanced Composition Explorer (ACE) spacecraft. Current work continues to use this dataset to investigate the characteristic ionospheric convection during magnetic storms via radar backscatter observed by the Super Dual Auroral Radar Network (SuperDARN). A superposed epoch analysis is completed using the map potential technique of Ruohoniemi and Baker [1998]. This technique has previously successfully been used to investigate substorm convection, however the technique has not particularly been employed for studies of geomagnetic storms nor has the model fit been applied to combined radar data from multiple storms for statistical studies rather than performing the analysis on an individual storm by storm basis. Latitude-Time-Velocity (LTV) plots, analogous to standard Range-Time-Intensity (RTI) plots, are used to visualise the results, which show the 'average' ionospheric response during different sized geomagnetic storms as the substorm control on the convection is mostly 'averaged out'. This, along with the cross-cap potential derived from the superposed SuperDARN results, is compared with similarly superposed auroral images from the IMAGE and POLAR spacecraft missions to better constrain the storm time coupling between the solar wind and magnetosphere. Results from the comparison of the convection reversal boundaries (derived from the SuperDARN data) and open-closed boundaries (from the auroral imagery) are presented to investigate the significance of a possible viscous interaction between the solar wind and the magnetosphere in addition to the normal reconnection-driven interaction.

Hutchinson, J. A.; Wright, D. M.; Milan, S. E.; Grocott, A.; Boakes, P. D.

2012-04-01

45

Kinetic modeling of the Saturn ring-ionosphere plasma environment  

NASA Technical Reports Server (NTRS)

A time-independent kinetic plasma model was developed on the basis of the Li et al. (1988) semikinetic plasma model and was used to study the interaction of the Saturnian ionosphere and ring plasma. The model includes the gravitational magnetic mirror and centripetal and ambipolar electric forces, and the effect of the mixing of two plasma populations. The results obtained indicate that the density, temperature, and composition of plasma near the rings changing in the direction from the inner C ring to the outer A ring, due to the fact that the predominant source of plasma changes from the ionosphere to the rings. The model results also suggest that the outflow of hydrogen from the ionosphere to the rings may be shut off for field lines passing through the outer B and A ring, due to the ambipolar electric field set up by the warm ring plasma trapped near the ring plane by the centipetal force. In these regions, there will be a net flux of O(+) ions from the rings to the ionosphere.

Wilson, G. R.; Waite, J. H., Jr.

1989-01-01

46

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

NASA Astrophysics Data System (ADS)

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%.

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

2007-01-01

47

Effect of magnetospheric convection on thermal plasma in the inner magnetosphere  

NASA Technical Reports Server (NTRS)

The effects of E x B convection on the distribution of plasma parameters in the inner magnetosphere have been examined. Analytical solutions describing density distributions along convective trajectories in the equatorial plane have been found. These solutions suggest the following dependence of plasma concentration n on the magnetic field B along convective trajectories: n proportional to B(exp alpha), where the parameter alpha varies between alpha is less than or = between 4/3 and 2. The alpha = 2 case corresponds to disregarding transport parallel to B. The lower bound alpha = 4/3 describes the situation when parallel transport dominates over convective motions perpendicular to B. A solution has also been obtained describing the effect of convection on diffusive equilibrium profiles in the dayside plasmasphere. In addition, ion temperature variations due to adiabatic effects associated with plasma convection have been analyzed in detail. Convective drifts lead to ion temperature anisotropies with the value and sign of the anisotropy contingent on density and temperature variations, local time, and the location of the convective trajectory with respect to the location of the plasmapause. We have also found that convective motions lead to a substantial exchange of energy between the ionosphere and the plasmasphere through electron heat fluxes.

Khazanov, G. V.; Rasmussen, C. E.; Konikov, Yu. V.; Gombosi, T. I.; Nagy, A. F.

1994-01-01

48

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

NASA Technical Reports Server (NTRS)

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.

Knudsen, W. C.

1973-01-01

49

Effect of self-consistent magnetic field on plasma sheet penetration to the inner magnetosphere under enhanced convection: RCM simulations combined with force-balance magnetic field solver  

Microsoft Academic Search

Transport of plasma sheet particles into the inner magnetosphere is strongly affected by the penetration of the convection electric field, which is the result of the large-scale magnetosphere-ionosphere electromagnetic coupling. This transport, on the other hand, results in plasma heating and magnetic field stretching, which become very significant in the inner plasma sheet (inside 20 RE). We have previously run

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

2010-01-01

50

Unusual ionospheric plasma density enhancements during high-power ionospheric pumping at EISCAT  

NASA Astrophysics Data System (ADS)

Ionospheric pumping experiments using the EISCAT HF facility at high powers up to 1GW effective radiated power have been executed in 2011 and 2012. Analysis of the UHF incoherent scatter radar ion-line data show apparently large (up to double) plasma density enhancements above the HF reflection altitude. The UHF radar plasma-line data are consistent with the pump-induced electron temperature enhancements derived from the UHF radar ion-line data, but not the large plasma density enhancements. We show that horizontal transport, field-aligned diffusion, temperature-dependent chemical effects and pump-induced ionisation are not likely explanations.

Kosch, M. J.; Senior, A.; Bryers, C.; Rietveld, M. T.; Xu, B.; Wu, J.; Pedersen, T.

2012-12-01

51

New Forms of Convection in Galaxy Cluster Plasmas  

E-print Network

New Forms of Convection in Galaxy Cluster Plasmas (i.e., how do galaxy clusters boil?) Eliot · Hot Plasma in Clusters of Galaxies · Hydrodynamic Convection (`normal' convection; e.g., the sun of Galaxies · largest gravitationally bound objects: · ~ 84% dark matter; ~ 14 % plasma; ~ 2% stars

Wurtele, Jonathan

52

Central Plasma Sheet Ion Properties as Inferred from Ionospheric Observations  

NASA Technical Reports Server (NTRS)

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

Wing, Simon; Newell, Patrick T.

1998-01-01

53

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

54

Plasma vortices in the ionosphere and atmosphere  

NASA Astrophysics Data System (ADS)

Vortices observed in ionized clouds of thunderstorm fronts have the nature of plasma vortices. In this work, the need to account for the electrostatic instability of plasma in the origination, intensification, and decay of plasma vortices in the atmosphere is shown. Moisture condensation results in mass-energy transfer under the inhomogeneous spatial distribution of aerosols. If a phase volume of natural oscillations is transformed in the frequency-wave vector space in inhomogeneous plasma, the damping of plasma oscillations promotes an increase in the pressure gradients normal to the geomagnetic field. Excitation of the gradient instabilities is probable in atmospheric plasma formations.

Izhovkina, N. I.

2014-11-01

55

Linear mode conversion in inhomogeneous magnetized plasmas during ionospheric  

E-print Network

facilitate acceleration of fast energetic electrons, resulting in observed enhanced airglow. INDEX TERMS Science: Ionospheric propagation (2487); 2411 Ionosphere: Electric fields (2712); 2439 Ionosphere of initial density inhomogeneities in the ionosphere which leads to the thermal self-focusing instability

Rubloff, Gary W.

56

Electrodynamics of long metallic tethers in the ionospheric plasma  

NASA Technical Reports Server (NTRS)

A study is presented of the electrodynamic interactions of long metallic tethers (lengths up to 100 km) with the ionospheric plasma. The study, which is of interest in view of possible future experiments using long tethers in space, includes the derivation of current and potential distribution along the tether, taking also the effects of internal resistance into account. Electrostatic and electrodynamic drag forces are computed and compared with aerodynamic drag.

Dobrowolny, M.

1978-01-01

57

Night-side effects on the polar ionospheric convection due to a solar wind pressure impulse .  

NASA Astrophysics Data System (ADS)

The Sudden Impulse (SI) of solar wind dynamic pressure of 20 february 2000, 21:03 UT, is investigated by making use of data from WIND, GEOTAIL, POLAR and GOES; ground magnetometer chains (Greenland, IMAGE, CANOPUS); SuperDARN HF radars in both Northern and Southern hemispheres. The main effect of the SI described herein is an enhancement of the ionospheric convection around midnight MLT. We suggest that such an enhancement be due to an increase of the dawn-dusk electric field caused by the SI compression of the magnetospheric tail.

Coco, I.; Amata, E.; Marcucci, M. F.; Villain, J.-P.; Hanuise, C.; Cerisier, J.-C.; St. Maurice, J.-P.; Sato, N.

58

Understanding the Earth's ionosphere as a fully sufficient source for magnetospheric plasma  

Microsoft Academic Search

One of the most significant questions remaining in space physics concerns the ultimate fate of ionospheric plasma outflows and their relative contribution to the plasma populations within the magnetosphere. A growing number of ionospheric outflow studies over the past two decades have cast serious doubt on the traditional view of solar wind as a dominant source of magnetospheric plasma. A

Matthew Mark Huddleston

2003-01-01

59

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

E-print Network

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

Mendillo, Michael

60

The response of ionospheric convection in the polar cap to substorm activity  

NASA Technical Reports Server (NTRS)

We report multi-instrument observations during an isolated substorm on 17 October 1989. The European Incoherent Scatter (EISCAT) radar operated in the SP-UK-POLI mode measuring ionospheric convection at latitudes 71 deg Lambda - 78 deg Lambda. Sub-Auroral Magnetometer Network (SAMNET) and the EISCAT Magnetometer Cross provide information on the timing of substorm expansion phase onset and subsequent intensifications, as well as the location of the field aligned and ionospheric currents associated with the substorm current wedge. Interplanetary Monitoring Platform-8 (IMP-8) magnetic field data are also included. Evidence of a substorm growth phase is provided by the equatorward motion of a flow reversal boundary across the EISCAT radar field of view at 2130 MLT, following a southward turning of the interplanetary magnetic field (IMF). We infer that the polar cap expanded as a result of the addition of open magnetic flux in the tail lobes during this interval. The flow reversal boundary, which is a lower limit to the polar cap boundary, reached an invariant latitude equatorward of 71 deg Lambda by the time of the expansion phase onset. We conclude that the substorm onset region in the ionosphere, defined by the westward electrojet, mapped to a part of the tail radially earthward of the boundary between open and closed magnetic flux, the distant neutral line. Thus the substorm was not initiated at the distant neutral line, although there is evidence that it remained active during the expansion phase.

Lester, M.; Lockwood, M.; Yeoman, T. K.; Cowley, S. W. H.; Luehr, H.; Bunting, R.; Farrugia, C. J.

1995-01-01

61

Effects of large zonal plasma drifts on the subauroral ionosphere  

NASA Technical Reports Server (NTRS)

A model of the earth's ionosphere and plasmasphere is used to investigate the effects of an imposed westward plasma drift of maximum velocity 2 km/s. A closed subauroral tube of plasma is considered and the velocity spike persists for 10 min. Ion-neutral frictional heating causes rapid elevation of the F-region O(+) temperature. The F-layer O(+) concentration is decreased due to increased O(+) loss rate and rapid ion flows both upward and downward from the F-region. The upward flux of O(+) through the topside ionosphere can each 5 x 10 exp 9/sq cm/s; when the velocity spike ceases there is a return flow of O(+) that tends to replenish the F-layer. Most of the features revealed by the model for the F-region and topside ionosphere are in accord with observations of subauroral ion drifts. Downward flows that are predicted to be persistently present around the 300 km altitude level appear to agree with observations only occasionally; suggestions are made to resolve this discrepancy.

Sellek, R.; Bailey, G. J.; Moffett, R. J.; Heelis, R. A.; Anderson, P. C.

1991-01-01

62

A Miniature Sweeping Impedance Probe for Ionospheric Plasma Diagnostics  

NASA Astrophysics Data System (ADS)

The impedance of a probe immersed in ionospheric plasma at radio frequencies is an important technique for determining absolute electron density. Building on 50 years of history in developing and flying RF probes for plasma diagnostics at Utah State, a new SIP (Sweeping Impedance Probe) design has been completed which will obtain qualitative improvement over previous instruments in terms of accuracy and sweep rate. This instrument will provide a continuous measurement of the plasma impedance magnitude and phase with an expected accuracy of 1% and 1 degree respectively over the 1 to 20 MHz range. This new SIP will be launched in January 2014 onboard the Auroral Spatial Structures Probe (ASSP) NASA sounding rocket mission using a short monopole probe. The rocket apogee of 600 km will allow the characterization of the plasma in the E and F layers at auroral latitudes and the study of short term and spatial variations along the high-altitude profile of the sounding rocket. Although this SIP design has been developed for a sounding rocket, it can be optimized and miniaturized for Cubesat's and included along other ionospheric diagnostic instruments such as double and Langmuir probes. This presentation is focused on the overall design of the instrument, the tests results for the ASSP instrument and conceptual designs for future CubeSat mission similar to the NSF DICE mission.

Martin-Hidalgo, J.; Swenson, C.

2013-12-01

63

Small-scale plasma irregularities in the nightside Venus ionosphere  

NASA Technical Reports Server (NTRS)

The individual volt-ampere curves from the Pioneer Venus Orbiter electron temperature probe showed evidence for small-scale density irregularities, or short-period plasma waves, in regions of the nightside ionosphere where the Orbiter electric field detector observed waves in its 100-Hz channel. A survey of the nightside volt-ampere curves has revealed several hundred examples of such irregularities. The I-V structures correspond to plasma density structure with spatial scale sizes in the range of about 100-2000 m, or alternatively they could be viewed as waves having frequencies extending toward 100 Hz. They are often seen as isolated events, with spatial extent along the orbit frequently less than 80 km. The density irregularities or waves occur in or near prominent gradients in the ambient plasma concentrations both at low altitudes where molecular ions are dominant and at higher altitudes in regions of reduced plasma density where O(+) is the major ion. Electric field 100-Hz bursts occur simultaneously, with the majority of the structured I-V curves providing demonstrative evidence that at least some of the E field signals are produced within the ionosphere.

Grebowsky, J. M.; Curtis, S. A.; Brace, L. H.

1991-01-01

64

Plasma transport in the equatorial ionosphere during the great magnetic storm of March 1989  

NASA Technical Reports Server (NTRS)

We have modeled plasma transport in the low-latitude and equatorial ionosphere during the great magnetic storm of March 1989. Our goal was to provide a consistent explanation for the DMSP (Defense Meteorological Satellite Program) observations of dramatic decreases in ion density and rapid ion drifts in the low latitude ionosphere over South America during the storm. The modeling effort supports the hypothesis that abnormally large upward drifts lifted F region plasma above the satellite's altitude and created the density depletions observed by DMSP. Modeled O(+) densities at the satellite's altitude have a strong qualitative resemblance to DMSP observations. Both the model and the observations indicate a deep density trough with extremely sharp boundaries surrounding the equator. The widths of both the modeled and the observed equatorial troughs increase with time. Vertical ion drifts predicted by the model also have been compared with DMSP measurements. Like the observed vertical drifts, the modeled drifts reversed sign near the trough boundaries. The modeled vertical drifts are of the same order and direction as the vertical component of E x B convection near the equator, but of opposite direction (downward) near the trough boundaries and outside of the trough.

Rasmussen, C. E.; Greenspan, M. E.

1993-01-01

65

On Plasma Instabilities in the Polar Cap Ionosphere  

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

66

Transverse ion heating in multicomponent plasmas. [in ionosphere  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

67

Solar Wind Driven Plasma Fluxes from the Venus Ionosphere  

NASA Astrophysics Data System (ADS)

SOLAR WIND DRIVEN PLASMA FLUXES FROM THE VENUS IONOSPHERE H. Pérez-de-Tejada (1), R. Lundin (2), H. Durand-Manterola (1), S. Barabash (2), T. L. Zhang (3), J. A., Sauvaud (4), and M. Reyes-Ruiz (5) 1 - Institute of Geophysics, UNAM, México, D. F. 2 - Swedish Institute of Space Physics, Kiruna, Sweden 3 - Space Research Institute, Graz, Austria 4 - CESR, Toulouse, France 5 - Institute of Astronomy, UNAM, Ensenada, México Measurements conducted with the ASPERA-4 instrument and the magnetometer of the Venus Express spacecraft show that the kinetic pressure of planetary O+ ion fluxes measured in the Venus wake can be significantly larger than the local magnetic pressure and, as a result, those ions are not being driven by magnetic forces but by the kinetic energy of the solar wind. Beams of planetary O+ ions with those properties have been detected in several orbits of the Venus Express through the wake as the spacecraft traverses by the noon-midnight plane along its near polar trajectory. The momentum flux of the O+ ions leads to superalfvenic flow conditions. It is suggested that such O+ ion beams are produced in the vicinity of the magnetic polar regions of the Venus ionosphere where the solar wind erodes the local plasma leading to plasma channels that extend downstream from those regions.

Perez De Tejada, H. A.; Lundin, R. N.; Zhang, T.; Sauvaud, J. A.; Reyes-Ruiz, M.

2012-12-01

68

Kinetic Space Weather: Toward a Global Hybrid Model of the Polar Ionosphere-Lower Magnetosphere Plasma Transport  

NASA Technical Reports Server (NTRS)

During the indicated period of performance, we had a number of publications concerned with kinetic polar ionosphere-lower magnetosphere plasma transport. For the IUGG 1991-4 Quadrennial Report, we reviewed aspects of U.S. accomplishments concerned with polar plasma transport, among other issues. In another review, we examined the computer simulations of multiple-scale processes in space plasmas, including polar plasma outflow and transport. We also examined specifically multiscale processes in ionospheric outflows. We developed a Generalized Semi-Kinetic(GSK) model for the topside-lower magnetosphere which explored the synergistic action of wave heating and electric potentials in the formation of auroral Ion conics, in particular the "pressure cooker" mechanism. We extended the GSK model all the way down to 120 km and applied this code to illustrate the response of the ionosphere- magnetosphere to soft-electron precipitation and convection-driven frictional ion heating, respectively. Later, the convection-driven heating work was extended to a paper for the Journal of Geophysical Research. In addition to the above full published papers, we also presented the first developments of the coupled fluid-semikinetic model for polar plasma transport during this period. The results from a steady-state treatment were presented, with the second presentation being concerned with the effects of photo-electrons on the polar wind, and the first garnering an outstanding student paper award from the American Geophysical Union. We presented the first results from a time-dependent version of this coupled fluid-semikinetic model.

Horwitz, James L.

1996-01-01

69

Simultaneous observations of ions of ionospheric origin over the ionosphere and in the plasma sheet at storm-time substorms  

NASA Astrophysics Data System (ADS)

We investigate variations of ion flux over the ionosphere and in the plasma sheet when storm-time substorms are initiated, using simultaneous observations of neutral atoms in the energy range of up to a few keV measured by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite and energetic (9-210 keV/e) ion flux measured by the Energetic Particles and Ion Composition/Suprathermal Ion Composition Spectrometer (EPIC/STICS) on board the Geotail satellite. We examined three storm intervals during which the IMAGE satellite was located near its apogee and the Geotail satellite was in the plasma sheet on the nightside. Low-energy neutral atoms traveling from the direction of the Earth can be created by outflowing ionospheric ions through charge exchange processes. The observed neutral atom flux enhancement at storm-time substorms indicates that substorms can cause an immediate increase of low-energy ion flux over the ionosphere by a factor of 3-10. In the plasma sheet, the flux ratio of O+/H+ is rapidly enhanced at storm-time substorms and then increased gradually or stayed at a constant level in a timescale of <60 minutes, suggesting a mass-dependent acceleration of ions at local dipolarization and a subsequent additional supply to the plasma sheet of O+ ions extracted from the ionosphere at the substorms.

Nose, M.; Taguchi, S.; Moore, T. E.; Collier, M. R.; Hosokawa, K.; Christon, S. P.; McEntire, R. W.

2006-12-01

70

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

E-print Network

spacecraft, which was placed in a highly eccentric orbit around Mars on 25 December 2003 [Chicarro et alElectron 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

Gurnett, Donald A.

71

Applications of numerical codes to space plasma problems  

NASA Technical Reports Server (NTRS)

Solar wind, earth's bowshock, and magnetospheric convection and substorms were investigated. Topics discussed include computational physics, multifluid codes, ionospheric irregularities, and modeling laser plasmas.

Northrop, T. G.; Birmingham, T. J.; Jones, F. C.; Wu, C. S.

1975-01-01

72

Annual and solar cycle dependencies of SuperDARN scatter occurrence and ionospheric convection measurements  

NASA Astrophysics Data System (ADS)

The Super Dual Auroral Radar Network (SuperDARN) provides a long term data series which enables investigations of the coupled magnetosphere-ionosphere system. The network has been in existence essentially since 1995 when 6 radars were operational in the northern hemisphere and 4 in the southern hemisphere. We have been involved in an analysis of the data over the lifetime of the project and present results here from two key studies. In the first study we calculated the amount of ionospheric scatter which is observed by the radars and see clear annual and solar cycle variations in both hemispheres. The recent extended solar minimum also produces a significant effect in the scatter occurrence. In the second study, we have determined the latitude of the Heppner-Maynard Boundary (HMB) using the northern hemisphere SuperDARN radars. The HMB represents the equatorward extent of ionospheric convection for the interval 1996 - 2011. We find that the average latitude of the HMB at midnight is 61° magnetic latitude during solar the maximum of 2003, but it moves significantly poleward during solar minimum, averaging 64° latitude during 1996, and 68° during 2010. This poleward motion is observed despite the increasing number of low latitude radars built in recent years as part of the StormDARN network, and so is not an artefact of data coverage. We believe that the recent extreme solar minimum led to an average HMB location that was further poleward than the previous solar cycle. We have also calculated the Open-Closed field line Boundary (OCB) from auroral images during a subset of the interval (2000 - 2002) and find that on average the HMB is located equatorward of the OCB by ~7o. We suggest that the HMB may be a useful proxy for the OCB when global images are not available. The work presented in this paper has been undertaken as part of the European Cluster Assimilation Technology (ECLAT) project which is funded through the EU FP7 programme and involves groups at Leicester, Helsinki, Uppsala, FMI, Graz and St. Petersburg. The aim of the project is to provide additional data sets, primarily ground based data, to the Cluster Active Archive, and its successor the Cluster Final Archive, in order to enhance the scientific productivity of the archives.

Lester, M.; Imber, S. M.; Milan, S. E.

2012-12-01

73

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

74

Response of ions of ionospheric origin to storm time substorms: Coordinated observations over the ionosphere and in the plasma sheet  

NASA Astrophysics Data System (ADS)

We investigate variations of ion flux over the ionosphere and in the plasma sheet when storm time substorms are initiated, using simultaneous observations of neutral atoms in the energy range of up to a few keV measured by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite, outflowing ion flux of <1 keV measured by the ion electrostatic analyzer (IESA) on board the Fast Auroral SnapshoT (FAST) satellite, and energetic (9-210 keV/e) ion flux measured by the energetic particle and ion composition (EPIC) instrument on board the Geotail satellite. We examined three storm intervals during which the IMAGE or FAST satellite was in a suitable location to observe ionospheric ion outflow and the Geotail satellite was in the plasma sheet on the nightside. The neutral atom flux observed by IMAGE/LENA in the first interval and outflowing ion flux observed by FAST/IESA in the second and third intervals indicate that storm time substorms can cause increases of low-energy ion flux over the ionosphere by a factor of 3-50 with time delay of less than several minutes. In the plasma sheet, the flux ratio of O+/H+ is rapidly enhanced at the storm time substorms and then increased gradually or stayed at a constant level in a time scale of ˜1 h, suggesting a mass-dependent acceleration of ions at local dipolarization and a subsequent additional supply of O+ ions to the plasma sheet which have been extracted from the ionosphere at the substorms. These coordinated observations revealed that substorms have both an immediate effect and a delayed effect (i.e., two-step effect) on the ion composition in the plasma sheet.

Nosé, M.; Taguchi, S.; Christon, S. P.; Collier, M. R.; Moore, T. E.; Carlson, C. W.; McFadden, J. P.

2009-05-01

75

Plasma bubbles in the topside ionosphere: estimations of the survival possibilities  

NASA Astrophysics Data System (ADS)

The study deals with the evaluation of the survival possibilities of the plasma bubbles, seen as He+ density depletions in the topside ionosphere. He+ density depletions (or subtroughs) are usually observed during a high solar activity at the topside ionospheric altitudes ( 1000 km) deeply inside the plasmasphere (L 1.3-3). They are considered as originating from equatorial plasma bubbles phenomena or as possible fossil bubble signatures. The estimation of the characteristic times of a life, diffusion and vertical drift transport of helium ions (He+ ) at the topside ionosphere heights of the low-/mid-latitude region was made. It is revealed, that the diffusion transport process is the fastest one (some minutes). Since the ionosphere plasma is magnetized plasma at the topside ionosphere heights, the diffusion processes are field-aligned. Plasma bubbles spread (due to diffusion processes) along the magnetic tubes. Their spreading becomes more and more significant in process of their uplifting. So extended bubbles look like `banana' with the extremities reaching the ionosphere heights in both the hemispheres. This scheme is also correct if the separate components are under considerations, namely He+ . On the other hand, it is well known, that the magnetic tube, partially "devastated" by a plasma bubble, is replenished extremely slowly. The tube replenishment time is proportionally L4 (i.e. Badin, JATP, 1994). For example, it takes 10 hours for refilling the tube (L=2, 45o INVLAT), partially "devastated" or depleted by plasma bubble. It was concluded, that, if some plasma bubbles can reach the topside and plasmashere heights, they can exist here (may be as "dead" bubbles) during some hours. It was also concluded, that there is enough time to register the plasma bubbles at the topside ionosphere heights.

Sidorova, Larisa; Filippov, Sergey

76

Nightside Ionosphere of Mars from Local Electron Plasma Oscillations: A General Overview and Electron Density Holes & Gaps (Invited)  

Microsoft Academic Search

The radar sounder on the Mars Express spacecraft provides local electron densities from electron plasma oscillations. Here, we present results from a study of the nightside ionosphere of Mars using local electron density data. Ionospheric density holes and gaps in the electron density profiles are observed on the nightside. Nightside ionospheric holes are commonly observed at Venus, at locations of

F. Duru; D. A. Gurnett; D. Winningham; R. A. Frahm; D. D. Morgan

2010-01-01

77

Vertical sheets of dense plasma in the topside Martian ionosphere  

Microsoft Academic Search

The low-frequency radar, Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), on board the Mars Express spacecraft is used to sound electron densities in the topside Martian ionosphere. The radar records the delay times to echoes of reflected radio waves as a function of frequency, yielding spectrograms with traces of radar echoes. At times, two traces are present in

E. Nielsen; X.-D. Wang; D. A. Gurnett; D. L. Kirchner; R. Huff; R. Orosei; A. Safaeinili; J. J. Plaut; G. Picardi

2007-01-01

78

Ionospheric perturbations in plasma parameters before global strong earthquakes  

NASA Astrophysics Data System (ADS)

Based on the electron density (Ne) and temperature (Te) data from DEMETER, the ionospheric perturbations before 82 Ms ? 7.0 earthquakes (EQs) during 2005-2010 were studied, using moving median and space difference methods within 10 days before and 2 days after these events in local nighttime. It was found that the plasma parameters disturbances appeared before 49 EQs, in which more disturbances were detected before shallow-focus earthquakes than deep ones, and there was little difference between continental and oceanic ones, both exceeding 1/2 percentage. For the disturbed time, more perturbations were seen in 1, 3, 5, 6, 8 days before EQs and 1 day after EQs. For the spatial distribution, the anomalies before EQs were not just above the epicenters, but shifted equatorward with several degrees to almost twenty degrees. Most of the abnormities were positive ones, which demonstrate that Ne increases before EQs at the altitude of 670 km of DEMETER. Perturbations of Ne were more than that of Te, which illustrates that Ne is much more sensitive to seismic activity than Te.

Liu, Jing; Huang, Jianping; Zhang, Xuemin

2014-03-01

79

Model study of the effects of gravity wave dissipation on the thermosphere and ionosphere from deep convection worldwide  

NASA Astrophysics Data System (ADS)

In this paper, we discuss the methods and results of a global modeling study for the effect of deep convection on the thermosphere and ionosphere through the dissipation of atmospheric gravity waves (GWs). The selected time periods are 15-27 June 2009, during the recent extreme solar minimum, and 15-27 June 2000, during the recent solar maximum. The convective plumes which overshot the tropopause are identified from IR images obtained by 5 satellites covering the Earth during each period. We model the excitation of GWs from these plumes, and ray trace them into the thermosphere using our ray trace model which has been upgraded to span the Earth. We then calculate the forcings/heatings/coolings which result when and where these GWs dissipate in the thermosphere. We input these forcings/heatings/coolings into the global TIME-GCM, and re-run the model. In this paper, we discuss these methods and models in detail. We then discuss how the thermosphere and ionosphere responded to the dissipation of these convectively-generated GWs worldwide. We show that the responses propagate westward due to wind filtering by tides in the lower thermosphere. We also show that the neutral temperature and wind perturbations are larger during extreme solar minimum than during solar maximum.

Vadas, Sharon; Liu, Hanli

80

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

SciTech Connect

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.

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

81

Behavior of thermal plasma in the ionosphere and magnetosphere  

NASA Technical Reports Server (NTRS)

Models of ion flow in the topside ionosphere were developed. These models took both H(+) and O(+) into account and permitted various parameter studies to be made affecting H(+) escape in polar winds. Extensive computer programs were written to display the measured electron density profiles in ways useful to geophysical analysis. The relationship between the location of the plasmapause as it is found in the equatorial plane and the location of the ionospheric trough was also investigated.

Banks, P. M.; Doupnik, J. R.

1973-01-01

82

Observations of the Topside Ionosphere Plasma Bubbles in the Separate Plasma Component (He+): Model Estimations  

NASA Astrophysics Data System (ADS)

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 [1, 2, 3, 4] that there is genetic connection between the He+ density depletions (subtroughs) and the equatorial plasma bubbles. For validation of this idea the characteristic times of the main aeronomy and electrodynamics processes, in which the plasma bubbles and their minor ion component (He+) are involved, have been calculated and compared among themselves. The conditions and factors, connected with solar activity, which are more favorable in the detection of the topside ionosphere plasma bubbles as He+ depletions, were under consideration. The numerical calculations, obtained in SAMIS3 model (3D model of equatorial spread F) and kindly presented by J. Huba (USA) [5], were used for this study. It was revealed that the plasma bubbles, reaching the "ceiling" heights, can exist within several days and that there is principal opportunity to observe them in the separate plasma component (He+). [1] L.N. Sidorova, Adv. Space Res. 33, 850 (2004). [2] L.N. Sidorova, Adv. Space Res. 39, 1284 (2007). [3] L.N. Sidorova, Geomag. and Aeronomy, Intern. 48, 56 (2008). [4] L.N. Sidorova, S.V. Filippov, J. Atm. Solar-Terr. Phys. 86, 83-91, doi: 10.1016/j.jastp.2012.06.013 (2012). [5] J.D. Huba, G. Joyce, J. Krall, Geophys. Res. Lett. 35, L10102, doi:10.1029/2008GL033509 (2008).

Sidorova, Larisa; Filippov, Sergey

2013-04-01

83

Interconnection of the Ionosphere Plasma Parameters and Electromagnetic Phenomena with Lithosphere Structures in Baikal Rift Zone  

NASA Astrophysics Data System (ADS)

Two expeditions to the Baikal rift zone have been spent in 2009 and 2010 to investigate and confirm data for lithosphere - ionosphere interaction. The stimulus for investigations organization was the fact of the ionosphere electric field perturbations revealed over this zone earlier. They were attributed to presence of the Earth crust faults and not connected with seismic activity. The analysis of variations of the ground and ionospheric geomagnetic field and the TEC in Baikal rift zone are presented. Synchronous disturbances of the ground magnetic field and the magnetic field in the ionosphere, caused by sferics propagation from remote lighting discharges were detected. The analysis of number of sferics registration at the height of 700 km by Demeter satellite has shown that there is an area of their intensive propagation through the upper boundary of earth-ionosphere wave guide. The analysis of the frequency spectrum of TEC variations shows that it changes when ionospheric point moves from north to south, and the latitude of this change coincides with the northern boundary of the region of sperics primary propagation. We detected also TEC jerks correlated with perturbations of the ground electric field. The footprints of these TEC jerks occur on the main faults in the south-west part of Baikal rift zone. These data may consider as a new confirmation of interconnection of the ionosphere plasma and electromagnetic phenomena with lithosphere structures.

Gavrilov, B. G.; Zetzer, J. I.; Parrot, M.

2012-12-01

84

Propagation of Impulse-Like Waveforms Through the Ionosphere Modeled by Cold Plasma  

NASA Astrophysics Data System (ADS)

In this chapter, we have studied the propagation of short, impulse-like pulses propagating through the ionosphere. The ionosphere is modeled by simple, cold plasma. The impulse response of such a plasma model is known to consist of two terms. The first term is the impulse itself and the second term contains a Bessel function of first order. This means that the impulse propagates as an impulse followed by a long, oscillatory tail. The numerical example studied here is that of the prototype impulse radiating antenna (IRA). Closed-form expressions are developed for the prototype IRA waveform propagation through the cold-plasma model of the ionosphere. The results are cross-checked with numerical evaluation via a convolution process that uses the known impulse response.

Giri, D. V.; Dvorak, S. L.

85

Simulations of plasma structure evolution in the high-latitude ionosphere  

NASA Technical Reports Server (NTRS)

The Naval Research Laboratory has recently developed a two-dimensional inertial, electrostatic code which has been successfully applied to the development and evolution of ionospheric structure driven by plasma instabilities. This code models the ionosphere and magnetosphere as a set of horizontal two-dimensional layers which are coupled by the vertical magnetic field lines at high latitudes. It is shown that the development of instability-generated structure can be strongly dependent on this coupling. For example, the influence of magnetospheric coupling on the E x B gradient drift instability is to retard the instability's growth and to isotropize density irregularities. The influence of ionospheric coupling on the Kelvin-Helmholtz instability is to retard its growth and to suppress vortex formation. This paper presents the results of numerical simulations of these instabilities and discusses their application to high-latitude ionospheric structure.

Huba, J. D.; Keskinen, M. J.; Fedder, J. A.; Mitchell, H. G.; Satyanarayana, P.

1988-01-01

86

Nonlinear input resistance of a low-frequency electric oscillator in the ionospheric plasma  

NASA Astrophysics Data System (ADS)

Knowledge of the characteristics of low-frequency antennas in a magnetoactive ionospheric plasma is important in radiophysical experiments aimed at the study of the radiation and propagation of VLF electromagnetic waves using space-borne measuring equipment. Here, the effect of the ionospheric plasma on the input resistance of an electric antenna is investigated analytically assuming that the antenna potential is determined solely by the floating potential and induction emf generated during the motion of the antenna in the geomagnetic field. The potential range from -0.2 to -1.5, corresponding to floating potential values at 200-1500 km above the earth surface, is considered as an example.

Lishin, I. V.; Sorokina, R. K.

1990-05-01

87

Ionospheric observations of F region artificial plasma turbulence, modified by powerful X-mode radio waves  

NASA Astrophysics Data System (ADS)

We study the influence of additional X-mode heating of the ionospheric plasma on the features of artificial ionospheric turbulence, induced in the ionospheric F region by O-mode waves over the ``Sura'' heating facility (Nizhny Novgorod, Russia). The X heating is shown to suppress the generation of HF plasma turbulence resulting from the development of both the parametric decay and thermal parametric instabilities. Typical times of variations in the turbulence intensity change from <=0.1 s to ~10 s, strongly depending on the heating scheme. Aftereffects of the X heating last up to 30-60 s. We distinguish at least three types of phenomena, according to the observed typical times of the processes, and discuss possible reasons for each of them.

Frolov, V. L.; Kagan, L. M.; Sergeev, E. N.; Komrakov, G. P.; Bernhardt, P. A.; Goldstein, J. A.; Wagner, L. S.; Selcher, C. A.; Stubbe, P.

1999-06-01

88

Momentum transfer between the Io plasma wake and Jupiter's ionosphere  

Microsoft Academic Search

The interaction between Io and Jupiter is dramatically illustrated by recent ultraviolet and infrared imaging of Jupiter's ionosphere. Bright auroral emissions are observed at the base of Io's flux tube with emissions at the footprint of Io's wake extending large distances downstream (roughly 100° around Jupiter). We propose as a possible explanation for the persisting wake emissions a subcorotating torus

P. A. Delamere; F. Bagenal; R. Ergun; Y.-J. Su

2003-01-01

89

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

SciTech Connect

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. The authors 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 {approximately} 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 ({ge} 5 eV) can be deduced. The earliest measurements are used to illustrate applications of the coded long-pulse technique to several aeronomic/ionospheric 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. 14 refs., 4 figs., 1 tab.

Djuth, F.T.; Elder, J.H. [Geospace Research, Inc., El Segundo, CA (United States)] [Geospace Research, Inc., El Segundo, CA (United States); Sulzer, M.P. [Arecibo Observatory (Puerto Rico)] [Arecibo Observatory (Puerto Rico)

1994-12-01

90

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

NASA Astrophysics Data System (ADS)

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).

Belov, Alexey; Huba, J. D.

91

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

Microsoft Academic Search

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

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

2010-01-01

92

The Interaction of Flowing Plasmas with Planetary Ionospheres: A Titan-Venus Comparison  

Microsoft Academic Search

direction. Corroborating evidence for the aberrated flows was provided by plasma observations. The wake field magnitudes were nonuniform, and in both cases, reduced magnitudes were found on field lines linked to the illuminated (dayside) ionospheres. Finally, both induced magnetotails contained regions in which the projection of the magnetic field onto the incident magnetic field was negative. This observation may indicate

Margaret G. Kivelson; Christopher T. Russell

1983-01-01

93

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

Microsoft Academic Search

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

D. T. Farley; D. T. Jr

1963-01-01

94

Ionosphere Plasma State Determination in Low Earth Orbit from International Space Station Plasma Monitor  

NASA Technical Reports Server (NTRS)

A plasma diagnostic package is deployed on the International Space Station (ISS). The system - a Floating Potential Measurement Unit (FPMU) - is used by NASA to monitor the electrical floating potential of the vehicle to assure astronaut safety during extravehicular activity. However, data from the unit also reflects the ionosphere state and seems to represent an unutilized scientific resource in the form of an archive of scientific plasma state data. The unit comprises a Floating Potential probe and two Langmuir probes. There is also an unused but active plasma impedance probe. The data, at one second cadence, are collected, typically for a two week period surrounding extravehicular activity events. Data is also collected any time a visiting vehicle docks with ISS and also when any large solar events occur. The telemetry system is unusual because the package is mounted on a television camera stanchion and its data is impressed on a video signal that is transmitted to the ground and streamed by internet to two off center laboratory locations. The data quality has in the past been challenged by weaknesses in the integrated ground station and distribution systems. These issues, since mid-2010, have been largely resolved and the ground stations have been upgraded. Downstream data reduction has been developed using physics based modeling of the electron and ion collecting character in the plasma. Recursive algorithms determine plasma density and temperature from the raw Langmuir probe current voltage sweeps and this is made available in real time for situational awareness. The purpose of this paper is to describe and record the algorithm for data reduction and to show that the Floating probe and Langmuir probes are capable of providing long term plasma state measurement in the ionosphere. Geophysical features such as the Appleton anomaly and high latitude modulation at the edge of the Auroral zones are regularly observed in the nearly circular, 51 deg inclined, 400 km altitude ISS orbit. Evidence of waves in the ion collection current data is seen in geographic zones known to exhibit the spread-F phenomenon. An anomaly in the current collection characteristic of the cylindrical probe appears also too be organized by the geomagnetic field.

Kramer, Leonard

2014-01-01

95

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

96

Direct measurements of the ionospheric convection variability near the cusp//throat  

E-print Network

that increased Joule heating due to variability in the electric field occurs near the dayside CRB of the crescent-shaped convection cell and little additional Joule heating occurs in the convection throat. INDEX TERMS: 2411 underestimate the magnitude of Joule heating when only the average electric field is included [Codrescu et al

Shepherd, Simon

97

Modelling the high-latitude ionosphere  

NASA Technical Reports Server (NTRS)

Results of an ionospheric model program are presented which demonstrate the extreme variability of the steady state, daytime, ionospheric F region electron density and ion composition due to both neutral atmospheric changes with solar cycle, season and magnetic activity, and to the effects of ionospheric drifts caused by perpendicular electric fields. Consideration is given to the time history of the ionospheric plasma as it undergoes convective motion due to the combined effects of corotation forces and electromagnetic forces which results from the mapping of the magnetospheric cross tail electric field to the rotating ionosphere. A simple model of the convection pattern is described. The model calculates the net effect of the tendency for the plasma to corotate about the geographic pole and the E sub Bar times B sub Bar velocity induced by a perpendicular electric field mapped to a circle centered about a point 5 deg antisunward of the geomagnetic pole and oriented such that the equipotentials are parallel to the noon midnight meridian. This convection pattern shows the generally accepted features of high latitude convection, but because of the offset between the geographic and geomagnetic poles a marked universal time dependence in these features is predicted.

Raitt, W. J.; Schunk, R. W.; Sojka, J. J.

1981-01-01

98

Anomalous ionospheric conductances caused by plasma turbulence in high-latitude E-region electrojets  

NASA Astrophysics Data System (ADS)

During periods of intense geomagnetic activity, electric fields penetrating from the Earth's magnetosphere to the high-latitude E-region ionosphere drive strong currents named electrojets and excite plasma instabilities. These instabilities give rise to plasma turbulence that induces nonlinear currents and strong anomalous electron heating observed by radars for more than thirty years. This plays an important role in magnetosphere-ionosphere coupling by increasing the ionospheric conductances and modifying the global energy flow. The conductances determine the cross-polar cap potential saturation level and the evolution of field-aligned (Birkeland) currents. This affects the entire behavior of the near-Earth plasma. A quantitative understanding of anomalous conductance and global energy transfer is important for accurate modeling of the geomagnetic storm/substorm evolution. Our theoretical analysis, supported by recent 3D fully kinetic particle-in-cell simulations, shows that during strong geomagnetic storms the inclusion of anomalous conductivity can more than double the total Pedersen conductance - the crucial factor responsible for magnetosphere-ionosphere coupling through the current closure. This should explain why existing global MHD codes developed for predictive modeling of Space Weather and based on laminar conductivities systematically overestimate the cross-polar cap potentials by a factor of two or close.

Dimant, Y. S.; Oppenheim, M. M.

2012-12-01

99

34th EPS Plasma Physics, Warsaw, Poland, 2--7 July, 2007 Nonlinear physics of the ionosphere  

E-print Network

34th EPS Plasma Physics, Warsaw, Poland, 2--7 July, 2007 Nonlinear physics of the ionosphere Space Centre, V�xj� #12;Bo Thid� 34th EPS Plasma Physics, Warsaw, Poland, 2--7 July, 20072 Space plasma diagnostic. #12;Bo Thid� 34th EPS Plasma Physics, Warsaw, Poland, 2--7 July, 20073 Secondary radiation

100

Magnetosphere-ionosphere coupling and scale breaking of a plasma cloud in the magnetosphere  

NASA Astrophysics Data System (ADS)

The goal of this paper is to deliver a long-missing interpretation of a central issue of the NASA-MPE barium injection experiment performed in September 1971. It pertains to the interaction with the ionosphere. Observations of the cloud's motion revealed no obvious sign of such interaction. The barium vapor was released from a Scout rocket at an altitude of 31,000 km above South America during late evening hours and was observed for more than 4000 s. The barium plasma split into several field-parallel streaks which moved for a long time as if subject to constant acceleration as viewed from the inertial frame of the rocket at release. This means that no reflection of energy due to a mismatch of ionospheric conductivity and the characteristic impedance of an impinging Alfvén wave was observed. It is this finding that has never been properly interpreted. Furthermore, after a careful assessment of the barium cloud properties and environmental parameters, we find a theoretical coupling time to the ambient flow which turns out to be substantially longer than observed. Although this appears to indicate that some interaction with the ionosphere occurred, we can rule out multiple wave reflections during the observed acceleration phase. Discarding other possibilities, we interpret the observed motions as sign of perfect matching of the momentum and energy flux into the ionosphere with the rate of dissipation. This is achieved during the initial phase by scale breaking of the cloud into streaks with narrow widths which allow parallel potential drops along the Alfvén wings because of the waves' inertial nature and inside the lower ionosphere owing to the finite parallel resistivity, thereby greatly reducing the effective Pedersen conductivity. The significance of this finding goes beyond understanding the barium injection experiment. It sheds light on how magnetospheric plasma irregularities can share momentum and energy with the ionosphere in an optimized fashion.

Haerendel, Gerhard; Mende, Stephen B.

2012-09-01

101

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

102

Plasma irregularities in the D-region ionosphere in association with sprite streamer initiation.  

PubMed

Sprites are spectacular optical emissions in the mesosphere induced by transient lightning electric fields above thunderstorms. Although the streamer nature of sprites has been generally accepted, how these filamentary plasmas are initiated remains a subject of active research. Here we present observational and modelling results showing solid evidence of pre-existing plasma irregularities in association with streamer initiation in the D-region ionosphere. The video observations show that before streamer initiation, kilometre-scale spatial structures descend rapidly with the overall diffuse emissions of the sprite halo, but slow down and stop to form the stationary glow in the vicinity of the streamer onset, from where streamers suddenly emerge. The modelling results reproduce the sub-millisecond halo dynamics and demonstrate that the descending halo structures are optical manifestations of the pre-existing plasma irregularities, which might have been produced by thunderstorm or meteor effects on the D-region ionosphere. PMID:24806314

Qin, Jianqi; Pasko, Victor P; McHarg, Matthew G; Stenbaek-Nielsen, Hans C

2014-01-01

103

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

NASA Astrophysics Data System (ADS)

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.

Farley, Donald

2010-05-01

104

Could global warming affect space weather? : case studies of intense ionospheric plasma turbulence associated with natural heat sources  

E-print Network

We report on observations of a series of highly-structured ionospheric plasma turbulence over Arecibo on the nights of 22/23 and 23/24 July, 2006. Incoherent scatter measurements by Arecibo radar, airglow measurements using ...

Pradipta, Rezy

2007-01-01

105

Linking Plasma Conditions in the Magnetosphere with Ionospheric Signatures  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

106

Space weather. Ionospheric control of magnetotail reconnection.  

PubMed

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

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

2014-07-11

107

Tsunami in the Ionosphere ? a pinch of gravity with a good plasma sauce !  

NASA Astrophysics Data System (ADS)

A series of ionospheric anomalies following the Sumatra tsunami has been reported in the scientific literature (e.g., Liu et al. 2006; DasGupta et al. 2006; Occhipinti et al. 2006). Similar anomalies were also observed after the tsunamigenic earthquake in Peru in 2001 (Artru et al., 2005) and after the recent earthquakes in Sumatra and Chile in 2007. All these anomalies show the signature in the ionosphere of tsunami-generated internal gravity waves (IGW) propagating in the neutral atmosphere over oceanic regions. Most of these ionospheric anomalies are deterministic and reproducible by numerical modeling (Occhipinti et al., 2006) via the ocean/neutral atmosphere/ionosphere coupling mechanism. In addition, the numerical modeling supplies useful helps in the estimation of expected anomalies in the global scale to explore the effect of geomagnetic field in the neutral/plasma coupling (Occhipinti et al., 2008). Here we present an overview of the physical coupling mechanism highlighting the strong ampli- fication mechanism of atmospheric IGW; it allows to detect these anomalies when the tsunami is offshore where the see level displacement is still small. This property adds to the increasing coverage of ionospheric sounding measurements, suggests the implication of ionospheric sounding in the future oceanic monitoring and tsunami warning system. [Artru et al., 2005] Geophys. J. Int., 160, 2005 [DasGupta et al., 2006] Earth Planet. Space, 35, 929-959. [Liu et al., 2006] J. Geophys. Res., 111, A05303. [Occhipinti et al., 2006] Geophys. Res. Lett., 33, L20104, 2006 [Occhipinti et al., 2008] Geophys. J. Int., in press.

Occhipinti, Giovanni; Rolland, Ms Lucie; Kherani, Alam; Lognonné, Philippe; Komjathy, Attila; Mannucci, Anthony

108

First storm-time plasma velocity estimates from high-resolution ionospheric data assimilation  

NASA Astrophysics Data System (ADS)

This paper uses data assimilation to estimate ionospheric state during storm time at subdegree resolution. We use Ionospheric Data Assimilation Four-Dimensional (IDA4D) to resolve the three-dimensional time-varying electron density gradients of the storm-enhanced density poleward plume. By Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE), we infer the three-dimensional plasma velocity from the densities. EMPIRE estimates of ExB drift are made by correcting the Weimer 2000 electric potential model. This is the first time electron densities derived from GPS total electron content (TEC) data are being used to estimate field-aligned and field-perpendicular drifts at such high resolution, without reference to direct drift measurements. The time-varying estimated electron densities are used to construct the ionospheric spatial decorrelation in vertical total electron content (TEC) on horizontal scales of less than 100 km. We compare slant TEC (STEC) estimates to actual STEC GPS observations, including independent unassimilated data. The IDA4D density model of the extreme ionospheric storm on 20 November 2003 shows STEC delays of up to 210 TEC units, comparable to the STEC of the GPS ground stations. Horizontal drifts from EMPIRE are predicted to be northwestward within the storm-enhanced density plume and its boundary, turning northeast at high latitudes. These estimates compare favorably to independent Assimilative Mapping of Ionospheric Electrodynamics-assimilated high-latitude ExB drift estimates. Estimated and measured Defense Meteorological Satellite Program in situ drifts differ by a factor of 2-3 and in some cases have incorrect direction. This indicates that significant density rates of change and more accurate accounting for production and loss may be needed when other processes are not dominant.

Datta-Barua, Seebany; Bust, Gary S.; Crowley, Geoff

2013-11-01

109

Relaxation Time of Artificial Periodic Irregularities of the Ionospheric Plasma and Diffusion in the Inhomogeneous Atmosphere  

NASA Astrophysics Data System (ADS)

We consider diffusion of the ionospheric-plasma irregularities as applied to the problem of experimental determination of the lower-ionosphere parameters by artificial periodic irregularities of the electron number density. A rigorous solution to the problem of diffusion of one-dimensional plasma irregularities in a weakly ionized medium, whose diffusion coefficient exponentially decreases with the altitude, is obtained. The Green's function for this problem is found. Three parameters are taken into account in the solution, namely, the size of the region occupied by the irregularities, the size of the irregularities, and a typical spatial scale of the e-fold decrease in the diffusion coefficient. Theoretical relaxation times of the irregularities as functions of these parameters are analyzed. Calculated relaxation times are compared with the times measured in the observation of the artificial periodic irregularities created by the SURA facility. Calculated relaxation times of these irregularities are in good agreement with the observed values.

Grigor'ev, G. I.; Bakhmet'eva, N. V.; Tolmacheva, A. V.; Kalinina, E. E.

2013-09-01

110

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

NASA Astrophysics Data System (ADS)

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.

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

2002-11-01

111

Ionospheric Research with Miniaturized Plasma Sensors Aboard FalconSAT-3  

NASA Astrophysics Data System (ADS)

Investigations into a novel technique to measure ionosphere-thermosphere parameters have culminated in the Flat Plasma Spectrometer (FLAPS) experiment, presently under development through a collaboration between NASA Goddard Space Flight Center (GSFC) and the U. S. Air Force Academy (USAFA). FLAPS is capable of providing measurements of the full neutral wind vector, full ion-drift velocity vector, neutral and ion temperatures, and deviations from thermalization. In addition, coarse mass spectroscopy is possible using an energy analysis technique. The suite of instruments is comprised of a set of 16 individual neutral and ion analyzers, each of which is designed to perform a specific function. Advances in miniaturization technology have enabled a design in which the 16-sensor suite resides on a circular microchannel plate with an effective area of 25 cm2. The FLAPS electronics package, consisting of low voltage and high voltage power supplies, a microprocessor, and Application Specific Integrated Circuit (ASIC) amplifiers, requires a volume of 290 cm3, power of 1.5 W, and a mass of 500 g. The suite requires a +5V regulated power line from the spacecraft, and the telemetry interface is a 5.0 V TTL-compatible serial connection. Data collection rates vary from 1 to 1000 (192 Byte) spectra per second. The motivation for the FLAPS experiment is driven by objectives that fall into both basic science and technology demonstration categories. Scientifically, there is strong interest in the effects of ionosphere-thermosphere coupling and non-thermalized plasma on the processes associated with equatorial F-region ionospheric plasma bubbles. These bubbles have been known to scintillate transionospheric propagation of radio waves, often resulting in disruptions of space-based communication and navigation systems. FLAPS investigations will assist in quantifying the impact of various processes on the instigation or suppression of plasma bubbles; certain outstanding questions include 1) What is the relevance of meridional winds in suppression of plasma bubble growth? 2) What role does a velocity space instability driven by non-thermalized plasma play in the generation of small scale (<1 km) bubbles? 3) What process is responsible for turbulence in plasma beyond the edges of a bubble structure? Technologically, the need for small yet capable instruments arises from the desire to make multipoint in situ measurements of "microscopic" plasma parameters to provide insight into "macroscopic" phenomena. Examples include coherency of spatial boundaries of large-scale ( ˜100 km) plasma bubbles, three dimensional structure of the equatorial wind and temperature anomaly, and vertical velocity gradients in the low latitude ionosphere. This paper provides an overview of the experiment motivation and instrument design of the FLAPS experiment.

Habash Krause, L.; Herrero, F. A.; Chun, F. K.; McHarg, M. G.

2003-12-01

112

Convective Cell Formation in a Z-Pinch Plasma Science and Fusion Center  

E-print Network

Convective Cell Formation in a Z-Pinch J. Kesner Plasma Science and Fusion Center Massachusetts systems can develop convective cells when the MHD inter- change stability criterion is violated. Using the system may develop large-scale convective cells which can lead to nonlocal transport [6, 7, 8, 9, 10

113

Ionospheric convection observations following the solar flare of 20 January 2005 and during the geomagnetic storm of 21 January 2005  

NASA Astrophysics Data System (ADS)

The MINIS balloon campaign was successfully conducted in January 2005 to investigate relativistic electron loss mechanisms. The MINIS campaign provided multi-point measurements of electron precipitation up to MeV energies, including simultaneous measurements at different longitudes and hemispheres. Two balloons, each carrying an X-ray spectrometer for measuring the bremsstrahlung produced as electrons precipitate into the atmosphere, were launched from Churchill, Manitoba. Four balloons, each carrying an X-ray spectrometer, and a 3-axis electric field instrument providing DC electric field and VLF measurements in 3 frequency bands, were launched from the South African Antarctic Station (SANAE IV). An X 7.1 solar flare occurred at 0636 UT on 20 January 2005. A CME from this flare arrived at the Earth 34 hours later. An SSC began at ~1650 UT followed by a geomagnetic storm with a Dst perturbation of ~-100nT. The AE index shows that the 20 January flare was followed first by 6 hours of deep quiet and then 28 hours of moderate activity. The balloon data contain evidence for two interesting geoelectric responses to the flare. The response of the tropospheric global circuit is discussed in a companion paper. There was an abrupt reduction of the horizontal electric field to a value near zero. Either the column resistance between the balloon and the ground fell to a value near zero, or the increased load from the ionosphere shorted out the cross-polar-cap potential. The arrival of the CME initiated an interval of very strong relativistic electron precipitation. The second and third Southern payloads and the first Northern payload made observations in both hemispheres of several extensive relativistic electron precipitation events that occurred from 1700 to 2000 UT on 21 January 2005. Each x-ray burst was preceded by a strong pulse of ionospheric convection. These flow bursts were directed poleward and sunward transport. The detailed comparison of data from the two balloons indicates that these bursts were temporal variations, not spatial structures. The data are consistent with an interval of enhanced reconnection and convection preceding each major enhancement in precipitation activity.

Holzworth, R. H.; Bering, E. A.; Reddell, B. D.; Kokorowski, M.; Bale, S.; Blake, J. B.; Collier, A. B.; Hughes, A. R.; Lay, E.; Lin, R. P.; McCarthy, M. P.; Millan, R. M.; Moraal, H.; O'Brien, T. P.; Parks, G. K.; Pulupa, M.; Sample, J. G.; Smith, D. M.; Stoker, P.; Woodger, L.

2005-12-01

114

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

NASA Technical Reports Server (NTRS)

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.

Faelthammar, Carl-Gunne

1986-01-01

115

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

NASA Astrophysics Data System (ADS)

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.

Sidorova, Larisa; Filippov, Sergey

116

The role of ionospheric plasma in the magnetosphere  

NASA Technical Reports Server (NTRS)

During the course of this project we have made a great deal of progress developing and using a new plasma modeling technique which we now refer to as the Generalized Semikinetic (GSK) model. It has been used to study the development of plasma flows in the plasmasphere, the polar cap and auroral zones, and the transition region. Below we describe some of the major accomplishments of this grant.

Wilson, Gordon R.

1993-01-01

117

The role of ionospheric plasma in the magnetosphere  

NASA Astrophysics Data System (ADS)

During the course of this project we have made a great deal of progress developing and using a new plasma modeling technique which we now refer to as the Generalized Semikinetic (GSK) model. It has been used to study the development of plasma flows in the plasmasphere, the polar cap and auroral zones, and the transition region. Below we describe some of the major accomplishments of this grant.

Wilson, Gordon R.

1993-09-01

118

Effect of vertical plasma transport on ionospheric F2-region parameters at equatorial latitude  

NASA Astrophysics Data System (ADS)

The variability of the F2-layer even during magnetically quiet times are fairly complex owing to the effects of plasma transport. The vertical E × B drift velocities (estimated from simplified electron density continuity equation) were used to investigate the seasonal effects of the vertical ion drifts on the bottomside daytime ionospheric parameters over an equatorial latitude in West Africa, Ibadan, Nigeria (Geographic: 7.4°N, 3.9°E, dip angle: 6°S) using 1 year of ionsonde data during International Geophysical Year (IGY) of 1958, that correspond to a period of high solar activity for quiet conditions. The variation patterns between the changes of the vertical ion drifts and the ionospheric F2-layer parameters, especially; foF2 and hmF2 are seen remarkable. On the other hand, we observed strong anti-correlation between vertical drift velocities and h?F in all the seasons. We found no clear trend between NmF2 and hmF2 variations. The yearly average value of upward daytime drift at 300 km altitude was a little less than the generally reported magnitude of 20 ms-1 for equatorial F-region in published literature, and the largest upward velocity was roughly 32 ms-1. Our results indicate that vertical plasma drifts; ionospheric F2-layer peak height, and the critical frequency of F2-layer appear to be somewhat interconnected.

Oyekola, O. S.; Ojo, Akin

119

SuperDARN observations of an unusually contracted ionospheric convection pattern during the recent deep solar minimum  

NASA Astrophysics Data System (ADS)

We present a long term study, from 1995 - 2011, of the latitude of the Heppner-Maynard Boundary (HMB) determined using the northern hemisphere SuperDARN radars. The HMB represents the equatorward extent of ionospheric convection. We find that the average latitude of the HMB at midnight is 61° magnetic latitude during the solar maximum of 2003, but it moves significantly poleward during solar minimum, averaging 64° latitude during 1996, and 68° during 2010. This poleward motion is observed despite the increasing number of low latitude radars built in recent years as part of the StormDARN network, and so is not an artefact of data coverage. We believe that the recent extreme solar minimum lead to an average HMB location that was further poleward than previous solar cycles. We also calculated the open-closed field line boundary (OCB) from auroral images during the years 2000-2002 and find that on average the HMB is located equatorward of the OCB by ~6°. We suggest that the HMB may be a useful proxy for the OCB when global auroral images are not available.

Imber, S. M.; Milan, S. E.; Lester, M.

2012-04-01

120

On the effect of BUM generation enhancement revealed using the scheme of additional heating of ionospheric plasma  

NASA Astrophysics Data System (ADS)

We present measured characteristics of the artificial ionospheric radio emission (AIRE), which were obtained experimentally using additional heating of the ionospheric F-region by O-polarized waves. It is shown that the observed enhancement of intensity of the broad upshifted maximum (BUM) of the AIRE can result from the influence of electrons accelerated in the plasma: esonance region on its generation. An empirical model of the phenomenon observed is developed. It is concluded from experimental results that the BUM has a complex structure and only one of its components produces the above emission enhancement. We show the possibility of using the AIRE in additional heating of ionospheric plasma for diagnostics of artificial ionospheric turbulence and investigation of the features of perturbation propagation along the geomagnetic field lines.

Frolov, V. L.; Erukhimov, L. M.; Komrakov, G. P.; Sergeev, E. N.; Thidé, B.; Bernhardt, P. A.; Wagner, L. S.; Goldstein, J. A.; Selcher, G.

1997-05-01

121

Ionized Plasma and Neutral Gas Coupling in the Sun's Chromosphere and Earth's Ionosphere/Thermosphere  

NASA Astrophysics Data System (ADS)

We review physical processes of ionized plasma and neutral gas coupling in the weakly ionized, stratified, electromagnetically-permeated regions of the Sun's chromosphere and Earth's ionosphere/thermosphere. Using representative models for each environment we derive fundamental descriptions of the coupling of the constituent parts to each other and to the electric and magnetic fields, and we examine the variation in magnetization of the components. Using these descriptions we compare related phenomena in the two environments, and discuss electric currents, energy transfer and dissipation. We present examples of physical processes that occur in both atmospheres, the descriptions of which have previously been conducted in contrasting paradigms, that serve as examples of how the chromospheric and ionospheric communities can further collaborate. We also suggest future collaborative studies that will help improve our understanding of these two different atmospheres, which while sharing many similarities, also exhibit large disparities in key quantities.

Leake, J. E.; DeVore, C. R.; Thayer, J. P.; Burns, A. G.; Crowley, G.; Gilbert, H. R.; Huba, J. D.; Krall, J.; Linton, M. G.; Lukin, V. S.; Wang, W.

2014-11-01

122

Studies of HF-induced Strong Plasma Turbulence at the HAARP Ionospheric Observatory  

NASA Astrophysics Data System (ADS)

High power HF transmitters may induce a number of plasma instabilities in the interaction region of overdense ionospheric plasma. We report results from our recent experiments using over one gigawatt of HF power (ERP) to generate and study strong Langmuir turbulence (SLT) and particle acceleration at the HAARP Observatory, Gakona, Alaska. Among the effects observed and studied in UHF radar backscatter are: SLT spectra including the outshifted plasma line or free-mode, appearance of a short timescale ponderomotive overshoot effect, collapse, cascade and co-existing spectra, control of artificial field-aligned irregularities (AFAI), the aspect angle dependence of the plasma line spectra, and suprathermal electrons. Mapping the intensity of SLT versus pointing angle, we have discovered a number of regions of strong interaction displaced from the primary HF interaction region. Stimulated electromagnetic emission (SEE) measurements complement radar measurements. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts.

Sheerin, J. P.; Adham, N.; Roe, R. G. E.; Keith, M. R.; Watkins, B. J.; Bristow, W. A.; Bernhardt, P. A.; Selcher, C. A.

2010-11-01

123

The generation of non aspect sensitive plasma density irregularities by eld aligned drifts in the lower ionosphere  

E-print Network

The generation of non aspect sensitive plasma density irregularities by ®eld aligned drifts irregularities with virtually no aspect sensitivity, in the lower ionosphere at high latitudes, by electron Small-scale plasma density irregularities are an impor- tant and ubiquitous phenomenon

Paris-Sud XI, Université de

124

Integrated Multi-Point Space Plasma Measurements With Four Ionospheric Satellites  

NASA Astrophysics Data System (ADS)

The STP-1 launch scheduled for late 2006 will place four satellites with ionospheric plasma diagnostics into the same nearly circular orbit with an altitude of 560 km and inclination of 35.4°. The satellites will allow for unique multipoint measurements of ionospheric scintillations and their causes. Both the radio and in-situ diagnostics will provide coverage of low- and mid-latitudes. The four satellites, STPSat1, NPSat1, FalconSat3, and CFE will follow the same ground-track but because of drag and mass differences their relative velocities will be different and vary during the lifetime of the satellites. The four satellites will start close together; separate over a few months and coming back together with near conjunctions at six and eight months. Two satellite conjunctions between NPSat1 and STPSat1 will occur most often, approximately one month apart at the end of the mission. STPSat1 is equipped with CITRIS (sCintillation and TEC Receiver In Space) which will measure scintillations in the VHF, UHF and L-band along with measuring Total Electron Content (TEC) along the propagation path. NPSat1 will carry a three-frequency CERTO (Coherent Electromagnetic Radio TOmography) Beacon which broadcasts phase-coherent signals at 150.012 MHz, 400.032 MHz, and 1066.752 MHz. CITRIS will be able to measure TEC and Scintillations along the orbital path (propagation path from NPSat1 to STPSat1) as well as between the CITRIS and the ground. NPSat1 carries electron and ion saturation Langmuir Probes, while FalconSat3 carries the FLAPS (FLAt Plasma Spectrometer) and PLANE (Plasma Local Anomalous Noise Environment). The in-situ diagnostic complement the CITRIS/CERTO radio techniques in many ways. The CIBOLA Flight Experiment (CFE) contains a wide band receiver covering 100 to 500 MHz. The CFE data can be processed to show distortion of wide-band modulations by ionospheric irregularities. CFE and CITRIS can record ground transmissions from the French DORIS beacons which radiate at 401.25 and 2036.25 MHz. The multi-point techniques provide redundant measurements of radio scintillations and other ionospheric distortions. The causative density irregularities will be imaged using computerized ionospheric tomographic and inverse-diffraction algorithms. The STP-1 sensors in low-earth-orbit will relate electron and ion density fluctuations and radio scintillation effects over a wide range of frequencies. This research supported at NRL by ONR.

Siefring, C. L.; Bernhardt, P. A.; Selcher, C.; Wilkens, M. R.; McHarg, M. G.; Krause, L.; Chun, F.; Enloe, L.; Panholzer, R.; Sakoda, D.; Phelps, R.; D Roussel-Dupre, D.; Colestock, P.; Close, S.

2006-12-01

125

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)

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.

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

2014-09-01

126

Properties of convective cells generated in magnetized toroidal plasmas  

SciTech Connect

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.

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

127

The Skylab barium plasma injection experiments. I - Convection observations  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

128

Ionospheric nf sub H resonances: Frequency shifts versus plasma conditions  

NASA Technical Reports Server (NTRS)

The Alouette 2 resonances observed near the harmonics of the electron cyclotron frequency f sub H reveal frequency shifts (relative to the n(f sub H) values derived from model field calculations) which can be interpreted in terms of plasma wave dispersion effects. These effects are observed on the 2(f sub H) resonance when it is near the resonance observed close to the upper hybrid frequency f sub T. The observations suggest that an oblique echo model may be required to give a proper interpretation of the 2(f sub H) resonance. Cyclotron damping can be ignored only when the angle between the propagation vector and the direction perpendicular to the earth's magnetic field B is less than a few degrees for the 2(f sub H) wave, and less than a few tenths of a degree for the n(f sub H) waves with n 2. The negative offset of the absolute value of B inferred from the plasma resonance observations is consistent with expectations based on recent OGO 3 and OGO 5 rubidium magnetometer observations at higher altitudes in the equatorial regions.

Benson, R. F.

1971-01-01

129

Storm-induced plasma stream in the low-latitude to midlatitude ionosphere  

NASA Astrophysics Data System (ADS)

Geomagnetic disturbances from 7 to 12 November 2004 were quite intense, and the maximum excursion of Dst reached -374 nT. Unusual ionospheric phenomena have been observed around the world that have been associated with successive magnetic storms during this period. The ionospheric total electron content (TEC) was increased at the longitudes of Japan within a short time after sunset on 8 November, from 20 TEC units at 1830 JST to 97 TEC units at 2015 JST (JST = UT + 9 h), where 1 TEC unit = 1×1016 el/m2. The enhanced TEC was significant over Hokkaido (˜43°N), and the center of the enhanced region was well within the plasmasphere as an L value of approximately 1.5. The drift velocity of the plasma in the density-enhanced region measured by the Defense Meteorological Satellite Program (DMSP) satellite was westward with a peak value of 250 m/s in the Earth's frame, demonstrating a positive correlation between density and drift velocity. A similar TEC event was observed after sunset on 10 November: TEC was enhanced, from 15 TEC units at 1830 JST to 45 TEC units at 2030 JST. During the second event, the ionosphere was highly structured and the rate of the TEC index (ROTI) increased. The two-dimensional map of a ROTI-enhanced region exhibited the west to northwest transportation of plasma in which density irregularities were entrained. A physical mechanism is proposed to explain these disturbances, i.e., storm-induced plasma stream, which is different from a phenomenon called storm-enhanced density at midlatitudes.

Maruyama, Takashi; Ma, Guanyi; Tsugawa, Takuya

2013-09-01

130

Modelling ionospheric density structures  

NASA Technical Reports Server (NTRS)

Large-scale density structures are a common feature in the high-latitude ionsphere. The structures were observed in the dayside cusp, polar cap, and nocturnal auroral region over a range of altitudes, including the E-region, F-region and topside ionosphere. The origins, lifetimes and transport characteristics of large-scale density structures were studied with the aid of a three-dimensional, time-dependent ionospheric model. Blob creation due to particle precipitation, the effect that structured electric fields have on the ionosphere, and the lifetimes and transport characteristics of density structures for different seasonal, solar cycle, and interplanetary magnetic field (IMF) conditions were studied. The main conclusions drawn are: (1) the observed precipitation energy fluxes are sufficient for blob creation if the plasma is exposed to the precipitation for 5 to 10 minutes; (2) structured electric fields produce structured electron densities, ion temperatures, and ion composition; (3) the lifetime of an F-region density structure depends on several factors, including the initial location where it was formed, the magnitude of the perturbation, season, solar cycle and IMF; and (4) depending on the IMF, horizontal plasma convection can cause an initial structure to break up into multiple structures of various sizes, remain as a single distorted structure, or become stretched into elongated segments.

Schunk, R. W.; Sojka, J. J.

1989-01-01

131

Monitoring ionospheric plasmas in space weather context via DSLP observations on board Proba-2  

NASA Astrophysics Data System (ADS)

The experiment Dual Segmented Langmuir Probe (DSLP) on board Proba-2 spacecraft (ESA) provides a long-term continual survey of basic plasma properties measured in situ in the dawn and dusk sectors of the upper terrestrial ionosphere. DSLP observations are acquired by two identical segmented spherical Langmuir probes representing a novel approach to a well developed plasma diagnostic technique. Starting its nominal operations in May 2010 almost four years of regular observations are currently being available providing a substantial data set for monitoring observed ionospheric disturbances and irregularities in view of potential space weather drivers. Here we present initial DSLP data scientific applications including seasonal or immediate variations of derived plasma properties in comparison with possible effects of sudden solar events or long term trends in the overall solar activity. In addition we present an on-line data archive build on complete DSLP data set where all raw measurements are routinely being processed into calibrated higher level data products derived from the PDS and CDF standards and made available throughout web interface.

Travnicek, Pavel; Stverak, Stepan; Hercik, David; Pavelka, Roman

2014-05-01

132

Effect of self-consistent magnetic field on plasma sheet penetration to the inner magnetosphere under enhanced convection: RCM simulations combined with force-balance magnetic field solver  

NASA Astrophysics Data System (ADS)

Transport of plasma sheet particles into the inner magnetosphere is strongly affected by the penetration of the convection electric field, which is the result of the large-scale magnetosphere-ionosphere electromagnetic coupling. This transport, on the other hand, results in plasma heating and magnetic field stretching, which become very significant in the inner plasma sheet (inside 20 RE). We have previously run simulations with the Rice Convection Model (RCM) to investigate how the earthward penetration of convection electric field, and therefore plasma sheet population, depends on plasma sheet boundary conditions. Outer boundary conditions at r ~20 RE are a function of MLT and interplanetary conditions based on 11 years of Geotail data. In the previous simulations, Tsyganenko 96 magnetic field model (T96) was used so force balance between plasma pressure and magnetic fields was not maintained. We have now integrated the RCM with a magnetic field solver (Liu et al., 2006) to obtain the required force balance in the equatorial plane. We have run the self-consistent simulations under enhanced convection with different boundary conditions in which we kept different parameters (flux tube particle content, plasma pressure, plasma beta, or magnetic fields) at the outer boundary to be MLT-dependent but time independent. Different boundary conditions result in qualitatively similar plasma sheet profiles. The results show that magnetic field has a dawn dusk asymmetry with field lines being more stretched in the pre-midnight sector, due to relatively higher plasma pressure there. The asymmetry in the magnetic fields in turn affects the radial distance and MLT of plasma sheet penetration into the inner magnetosphere. In comparison with results using the T96, plasma transport under self-consistent magnetic field results in proton and electron plasma sheet inner edges that are located in higher latitudes, weaker pressure gradients, and more efficient shielding of the near-Earth convection electric field (since auroral conductance is also confined to higher latitudes). We are currently evaluating the simulated plasma sheet properties by comparing them with statistical results obtained from Geotail and THEMIS observations.

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

2010-12-01

133

Non-Uniform Plasma Discharges in Near Earth Space Environment and Ionosphere to Troposphere Responses  

NASA Astrophysics Data System (ADS)

Most earth weather and ionosphere-space environment coupling studies separate the problems into distinct groups. Heliosphere to solar wind - solar storm activity to ionospheric coupling - thermosphere and mid- altitude to the ionosphere and electrical effects such as elves and sprites and thunderstorms in another group - additionally mid and high latitude weather systems are many times separated also. The theoretical work here shows that not only are these areas coupled and related, but it also shows that without the constant electrical and resulting magnetic driving forces from space environments, earth would have little if no weather variability at all below the ionosphere. With only solar light energy as input, earth (and the other planets) would have little weather at all. The realization that extensive electrical activates occur in and above the troposphere, extending to the ionosphere and ultimately coupling to the magnetosphere have raised the theoretical and experimental questions regarding the sources of EMF which create the observed effects. The current work has identified 17 Local Electrical Batteries (LEBs), which provide the electrical EMF that can be linked to the observed effects the jet streams and lower atmospheric weather phenomenon. The path of the sources of EMF can be followed from the passing solar wind through "tunnels" that end in electrical currents that pass into the atmosphere via the ionosphere to storm cloud systems in the lower atmosphere. However the source of energy comes from localized plasma discharging of a non-uniform plasma environment that powers the electrical systems of the entire solar system. These are ultimately the sources of electrical energy that power the severe lower atmospheric storm systems such as westerly moving hurricanes at low latitudes and associated tornadoes. The connection is made theoretically with the solar wind that drives the 17 identified LEBs. The ultimate source of driving energy is the result of an excess current of protons in the solar wind, which creates an overall capacitor with inherent non-uniform electric field surrounding the Sun. On a local scale the voltage gradients are quite low, but all objects in this solar capacitor, including the planets and their moon systems, discharge this capacitor over extensive trans-planetary distances, thus creating excessive current flows, which also respond to CMEs and solar flares which carry a far greater potential gradient in the passing solar wind. The key to understanding reactions to non-uniform electric fields in the LEB environment is based on the fact that planetary Debye shielding takes on a new form, which is extended from that of the neutral environment typically considered in previous theoretical models. An attempt is made to solve the fundamental problem of the source of energy that drives these systems. The effects of moons and their positions relative to the planet and solar wind, as well as multiple planetary electrical alignments, are shown to contribute to the overall discharge phenomenon. A connection is made between these energy sources and cyclonic storms, earthquakes and volcanic "trigger" mechanisms. The goal of this research is to create an overall space weather model that couples the single energy source (the non-uniform plasma environment of the Sun created by an excess current of positive charge in the solar wind) to the earth's magnetosphere and ionosphere (and other planetary environments) and ultimately to the low altitude weather systems.

McCanney, J. M.

2009-05-01

134

Modeling magnetospheric plasma; Proceedings of the First Huntsville Workshop on Magnetosphere/Ionosphere Plasma Models, Guntersville, AL, Oct. 14-16, 1987  

NASA Technical Reports Server (NTRS)

The conference presents papers on the global modeling of magnetospheric plasma processes, the modeling of the midlatitude ionosphere and plasmasphere, the modeling of the auroral zone and boundary layer, the modeling of the polar magnetosphere and ionosphere, and the modeling of the plasma sheet and ring current. Particular attention is given to the kinetic approach in magnetospheric plasma transport modeling, self-consistent neutral point current and fields from single particle dynamics, preliminary statistical survey of plasmaspheric ion properties from observations by DE 1/RIMS, and a model of auroral potential structures based on dynamics explorer plasma data. Other topics include internal shear layers in auroral dynamics, quantitative parameterization of energetic ionospheric ion outflow, and open flux merging in an expanding polarcap model.

Moore, T. E. (editor); Waite, J. H., Jr. (editor)

1988-01-01

135

Topside ionosphere plasma bubbles, seen in He+ density: longitudinal dependence and thermosphere meridional wind influence  

NASA Astrophysics Data System (ADS)

He+ density depletions, considered as originating from equatorial plasma bubbles, or as fossil bubble signatures, were involved in this study. He+ density depletions, obtained from ISS-b spacecraft data, were observed during a high solar activity (1978-80, F10.7=200) in the topside ionosphere (900-1100 km) deeply inside the plasmasphere (L=1.3-3) (Sidorova, 2004, 2007). (1) He+ density depletion statistics with respect to longitude is considered for the post-sunset hours under winter, summer and equinoctial conditions within of 35° invariant latitudes. The map of He+ density depletion distribution as function of latitude- and longitude was also derived. The statistics and the map were compared with Equatorial Spread-F statistics, plasma bubble distribution and Range Spread-F statistics, obtained by Maruyama and Matuura (1984, 1980) from ISS-b spacecraft data for the same period (1978-80). The longitudinal variations of the Equatorial F-region Irregularities probability, obtained from the AE-E spacecraft data (McClure et al., 1998) for the same period, were also taken. Comparison shows good conformity in statistics/spatial distributions of all mentioned irregularities. Their predominant occurrence area for all seasons and both hemispheres covers the region of Brasilia, Atlantic Ocean and Africa (270°-0°-30°), where the range of magnetic field declination angle varies from 0° to 20°. (2) It is also suggested, that the plasma bubbles, 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 thermosphere winds in the development of plasma bubbles, observed in He+ density, the evaluation of the possible influence of the thermosphere meridional winds was done. The diurnal He+ density depletion statistics, averaged for solstices and equinoxes, were compared with the model velocity variations of the thermosphere meridional wind, taken from (Maruyama, 1996). It was revealed that the meridional wind influence shows itself as modulation effect. The modulation has seasonal dependence and the best correlation in equinoxes (R=0.87). The best amplitude correlation was found for the longitudes of 270°-360° (Brasilia, Atlantic regions), where the declination angle of the magnetic meridional wind component is near 20°. It was concluded that the topside plasma bubbles, seen as He+ density depletions, are strong enough affected by thermosphere meridional wind. REFERENCE Maryama, T. and N. Matuura, Global distribution of occurrence probability of spread echoes based on ISS-b observation, RRL, vol.27, N 124, 201-216, 1980. Maryama, T. and N. Matuura, Longitudinal variability of annual changes in activity of equatorial spread F and plasma bubbles, J. Geophys. Res., 89(A12), 10,903-10,912, 1984. Maruyama, T., Modeling study of equatorial ionospheric height and spread F occurrence, J. Geophys. Res., vol. 101, A3, pp. 5157-5163, 1996. McClure, J. P., Singh S., Bamgboye D.K., Johnson F.S., Hyosub Kil. Occurrence of equatorial F region irregularities: Evidence for tropospheric seeding, J. Geophys. Res., 103(A12), 29,119-29,135, 1998. Sidorova, L.N., He+ density topside modeling based on ISS-b satellite data, Adv. Space Res., vol. 33, pp. 850-854, 2004. Sidorova, L.N., Plasma bubble phenomenon in the topside ionosphere, Adv. Space Res., Special issue (COSPAR), doi: 10.1016/j.asr.2007.03.067, 2007.

Sidorova, L.

2009-04-01

136

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

SciTech Connect

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.

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

137

Characterization of the geometries of the high-latitude ionospheric convection pattern  

NASA Astrophysics Data System (ADS)

An investigation of the geometries of the high-latitude convection pattern is conducted using spacecraft observations of the northern hemisphere during conditions when the z-component of the interplanetary magnetic field is negative. In the first part of this investigation we examine the specification of the polar cap boundary as a circle using data from nearly simultaneous satellites to investigate the variation in size and location of the circle and the means by which such variations may be specified. We also investigate the degree to which a circle departs from the instantaneous configuration of the boundary and the effect that such departures may have on the global potential distribution. The DMSP satellites F8 and F9 provide an opportunity to identify the polar cap boundary with four nearly simultaneous points that can be used in a least squares fitting procedure to derive a best fit circle describing the polar cap boundary. The results of this exercise confirmed that the polar cap boundary can be well represented by a circle with the center offset towards the midnight sector with a B(sub y) and seasonal dependence in the radius of the circle and the location of the center point. Our results indicated that departures from a nominally circular boundary occur most frequently on the dayside. These departures led us to conclude that the polar cap boundary can be best represented by two circular segments with a smaller segment on the dawnside for conditions of B(sub y) negative. We also identified localized bulges or depressions as departures from the circle that are consistent with the descriptions of suggested impulsive additions of magnetic flux to the polar cap. In the second part of this investigation we examine the latitude distribution of the potential at latitudes below the polar cap boundary to determine its sensitivity to interplanetary conditions, magnetic activity, and local time. We use a gaussian curve segment to best represent the distribution of the potential equatorward of the polar cap and find the gaussian halfwidth is dependent on the potential at the polar cap boundary with the halfwidth being larger on the duskside than on the dawnside. We also find this parameter is dependent on local time as well as Kp and IMF B(sub z). In all cases, the halfwidth shows a greater variability on the duskside than on the dawnside. Finally, we note that the potential distribution around the polar cap boundary shows significant departures from the sinusoidal distribution frequently assumed in model treatments. As a final exercise, we use our results to generate inputs into a mathematical model of the high-latitude convection pattern and compare the results to measured data and find the model results to be reasonable representations of the actual conditions.

Keating, Christopher Francis

138

Plasma sheet magnetic fields and flows during steady magnetospheric convection events  

NASA Astrophysics Data System (ADS)

Inner magnetosphere magnetic field and plasma flow data are examined during 228 steady magnetospheric convection events. We find that the BZ component of the magnetic field around geostationary orbit is weaker than during average conditions and the plasma flow speeds are higher than average in the dusk sector just beyond geostationary orbit. The steady magnetospheric convection periods include more enhanced earthward and tailward flow intervals than during average conditions. The steady convection period magnetic field is not steady: The near-geostationary nightside field grows increasingly taillike throughout the steady convection period. In the midtail, earthward flows are enhanced in a wide region around the midnight sector, which leads to enhanced magnetic flux transport toward the Earth during the steady convection periods. Compared to well-known characteristics during magnetospheric substorms, the inner tail evolution resembles that during the substorm growth phase, while the midtail flow characteristics during steady convection periods are similar to those found during substorm recovery phases.

Pulkkinen, T. I.; Partamies, N.; Kissinger, J.; McPherron, R. L.; Glassmeier, K.-H.; Carlson, C.

2013-10-01

139

Dynamics of three-dimensional plasma clouds with coupling to the background ionosphere  

NASA Technical Reports Server (NTRS)

A three-dimensional, time-dependent model with a two-grid system was developed to study the expansion of a plasma cloud in the F region and topside ionosphere. The model maintains an adequate resolution for the released cloud motion and its interaction with the immediate environment, and it includes the effect due to the coupling with the distant part of the ionosphere (i.e., E region). Simulations were performed using realistic background ionospheric density profiles in both the E and F regions. The results show that the cloud coupling to the underlying E region affects the perpendicular cloud motion the most. The distant coupling acts to reduce the perturbation potential and perpendicular velocity and delays or eliminates the striations. These simulation results are consistent with simple analytical approximations. The simulation results also show that the distant coupling has a very small effect on 'localized' phenomena, such as the cloud expansion along the B RIGHT ARROW field and the electrostatic snowplow. The cloud-induced electric potential is attenuated in the lower E region. The electrons flow along the B RIGHT ARROW field, carrying the current to the E region and back to the cloud. The current closure is demonstrated in three dimensions for the first time for such a problem. The perpendicular current flowing through the plasma cloud is closed by the field-aligned electron current and the background perpendicular (mainly Pedersen) current in both the E and F regions. The 'image cloud' formation in t he E region is also clearly demonstrated. The variation of the density change in the 'image cloud' along the B RIGHT ARROW field and the features of the image cloud are shown.

Ma, T.-Z.; Schunk, R. W.

1994-01-01

140

Self-Consistent Magnetosphere-Ionosphere Coupling and Associated Plasma Energization Processes  

NASA Technical Reports Server (NTRS)

Magnetosphere-Ionosphere (MI) coupling and associated with this process electron and ion energization processes have interested scientists for decades and, in spite of experimental and theoretical research efforts, are still ones of the least well known dynamic processes in space plasma physics. The reason for this is that the numerous physical processes associated with MI coupling occur over multiple spatial lengths and temporal scales. One typical example of MI coupling is large scale ring current (RC) electrodynamic coupling that includes calculation of the magnetospheric electric field that is consistent with the ring current (RC) distribution. A general scheme for numerical simulation of such large-scale magnetosphere-ionosphere coupling processes has been presented earlier in many works. The mathematical formulation of these models are based on "modified frozen-in flux theorem" for an ensemble of adiabatically drifting particles in the magnetosphere. By tracking the flow of particles through the inner magnetosphere, the bounce-averaged phase space density of the hot ions and electrons can be reconstructed and the magnetospheric electric field can be calculated such that it is consistent with the particle distribution in the magnetosphere. The new a self-consistent ring current model has been developed that couples electron and ion magnetospheric dynamics with calculation of electric field. Two new features were taken into account in addition to the RC ions, we solve an electron kinetic equation in our model, self-consistently including these results in the solution. Second, using different analytical relationships, we calculate the height integrated ionospheric conductances as the function of precipitated high energy magnetospheric electrons and ions as produced by our model. This results in fundamental changes to the electric potential pattern in the inner magnetosphere, with a smaller Alfven boundary than previous potential formulations would predict but one consistent with recent satellite observations. This leads to deeper penetration of the plasma sheet ions and electrons into the inner magnetosphere and more effective ring current ions and electron energization.

Khazanov, G. V.; Six, N. Frank (Technical Monitor)

2002-01-01

141

Large-scale imaging of high-latitude convection with Super Dual Auroral Radar Network HF radar observations  

Microsoft Academic Search

The HF radars of the Super Dual Auroral Radar Network (SuperDARN) provide measurements of the E x B drift of ionospheric plasma over extended regions of the high- latitude ionosphere. With the recent augmentation of the northern hemisphere component to six radars, a sizable fraction of the entire convection zone (approximately one-third) can be imaged nearly instantaneously (-2 min). To

J. M. Ruohoniemi; K. B. Baker

1998-01-01

142

Plasma bubbles in the topside ionosphere: Estimations of the survival possibility  

NASA Astrophysics Data System (ADS)

The question about the survival possibility and the life duration of the topside ionosphere equatorial spread F (ESF) plasma bubbles observed in the separate ion component (He+) is investigated. For this aim the main aeronomy processes, in which plasma bubbles and their He+ ions are involved, were under consideration. It was obtained that the main competition takes place between the He+ loss reactions (He+-N2 reaction) and the uplift during linear growth phase (~10 min) of the Rayleigh-Taylor (R-T) instability, when the plasma bubbles are forming. It was revealed that the ambipolar diffusion of the He+ ions inside the plasma bubble is the fastest (~1-2 min) in the altitude region up to 500 km and becomes slower (~1 h) above 500 km. On the other hand, the plasma bubbles seen in He+ density are pretty stable structures against the cross-field (Bohm) diffusive collapse. It was concluded that the ESF plasma bubbles, reaching the “ceiling” heights, can exist for a night and several morning hours (~10-13 h) and that there is a principal opportunity to observe them in the separate ion component (He+).

Sidorova, L. N.; Filippov, S. V.

2014-11-01

143

Plasma expansion characteristics of ionized clouds in the ionosphere - Macroscopic formulation  

NASA Technical Reports Server (NTRS)

A macroscopic plasma expansion model, based on a numerical solution of the type-dependent nonlinear coupled continuity and momentum equations for background O(+) ions and several released ion species, was used to examine plasma expansion characteristics of ionized clouds in the ionosphere. Information is obtained on Ba(+), Li(+), and Ba(+) - Li(+) clouds; different cloud sizes (Gaussian half widths of 0.1, 0.5, and 1 km); cloud/background ion density ratios covering two orders of magnitude; electron/ion temperature ratios of 1, 5, and 10; and several cloud-background relative velocities along B (0, 1, 2, 4, 6, and 8 km/sec). The macroscopic expansion features obtained were found to be in general agreement with those obtained from the small-scale numerical simulations.

Schunk, R. W.; Szuszczewicz, E. P.

1991-01-01

144

Geomagnetic activity as a reflection of processes in the magnetospheric tail: 2. Plasma convection model  

NASA Astrophysics Data System (ADS)

A model of plasma convection in the magnetospheric tail was developed. Although highly simplified, the model adequately describes the main characteristics of the process. We have calculated the physical parameters characterizing the magnetotail, as well as described the convection of fluxtubes in it and the process of electron dropout. The model explains the semiannual variation in magnetic activity.

Krymskii, G. F.; Danilov, A. A.; Makarov, G. A.

2013-09-01

145

Auroral ionospheric signatures of the plasma sheet boundary layer in the evening sector  

NASA Technical Reports Server (NTRS)

We report on particles and fields observed during Defense Meteorological Satellite Program (DMSP) F9 and DE 2 crossings of the polar cap/auroral oval boundary in the evening magnetic local time (MLT) sector. Season-dependent, latitudinally narrow regions of rapid, eastward plasma flows were encountered by DMSP near the poleward boundary of auroral electron precipitation. Ten DE 2 orbits exhibiting electric field spikes that drive these plasma flows were chosen for detailed analysis. The boundary region is characterized by pairs of oppositely-directed, field-aligned current sheets. The more poleward of the two current sheets is directed into the ionosphere. Within this downward current sheet, precipitating electrons either had average energies of a few hundred eV or were below polar rain flux levels. Near the transition to upward currents, DE 2 generally detected intense fluxes of accelerated electrons and weak fluxes of ions, both with average energies between 5 and 12 keV. In two instances, precipitating ions with energies greater than 5 keV spanned both current sheets. Comparisons with satellite measurements at higher altitudes suggest that the particles and fields originated in the magnetotail inside the distant reconnection region and propagated to Earth through the plasma sheet boundary layer. Auroral electrons are accelerated by parallel electric fields produced by the different pitch angle distributions of protons and electrons in this layer interacting with the near-Earth magnetic mirror. Electric field spikes driving rapid plasma flows along the poleward boundaries of intense, keV electron precipitation represent ionospheric responses to the field-aligned currents and conductivity gradients. The generation of field-aligned currents in the boundary layer may be understood qualitatively as resulting from the different rates of earthward drift for electrons and protons in the magnetotail's current sheet.

Burke, W. J.; Machuzak, J. S.; Maynard, N. C.; Basinska, E. M.; Erickson, G. M.; Hoffman, R. A.; Slavin, J. A.; Hanson, W. B.

1994-01-01

146

New ISTP Solar Max: A Multi-Spacecraft Study of the Flow of Ionospheric Plasma  

NASA Technical Reports Server (NTRS)

The unique instrumentation on the Polar satellite combined with the simultaneous measurement of different parts of the magnetosphere with multiple satellites make possible the study of magnetospheric processes in a special way. In particular, the study of the ionospheric supply of plasma to the magnetosphere can by accomplished to give important results on the plasmas which drive the dynamics of the magnetosphere. This study concentrated on the period of September to December, 2001 in which the Polar orbit had precessed to the point that the line of apsides was near the equatorial plane. This unique orbital configuration enabled the TIDE instrument to measure outflowing ions across the polar cap and then transit the magnetotail lobes and observe the dramatic change in plasma characteristics as the satellite entered the plasma sheet. Contact was made with investigators on the Cluster and Geotail satellite missions and corresponding time frames were studied in the data. There were two approximate conjunctions between Polar and Geotail and data were compared to look for features which might be related. The higher energy concentration of the Geotail instrument made direct comparisons with TIDE difficult, and the Cluster measurements did not surface any cases that corresponded closely in space and time. There were, however, many interesting aspects of the Polar orbits which permitted the observation of the changing ionospheric outflowing plasma characteristics. As in earlier measurements, the ionospheric plasma could be seen flowing up the magnetic field lines out of the northern and southern polar caps. Its energy suggested a polar wind origin energized by the centrifugal acceleration of flow through the polar cusp. The roughly 10eV ions then moved out into the lobes of the magnetotail where they could be seen flowing toward the plasma sheet in both the northern and southern magnetotail lobes. There was also a double field-aligned region of warm ions observed just outside the plasmasphere, stretching toward the auroral zone and inner plasma sheet boundary. Upon entering the plasma sheet, the plasma energy jumped from 10 s of eV to greater than 1 keV. The single field aligned flows transitioned to highly variable spatially choppy energized ion distributions with a variety of pitch angle configurations. This pattern was quite repeatable in all of the Polar orbits that were examined and are compatible with the source of ions being the polar wind which is then energized to 10 s of eV by the centrifugal acceleration. These modestly energized polar wind ions are then carried to the magnetotail where they are substantially energized by the curvature drift-induced movement across the cross-tail potential of the magnetotail. This latter drift energizes the ions to the energies typically found in the plasma sheet. Subsequent drift and energization can cause the ions to become part of the ring current. The results of this study were presented at the Spring AGU meeting in 2002 and the GEM meeting in June 2003. They are the foundation for a paper that has been submitted by Matthew Huddleston to the Journal of Geophysical Research in December 2003. This work was part of the thesis that Matthew completed in finishing his Ph.D. in Physics at Vanderbilt University.

Chappell, Charles R.

2003-01-01

147

Radial convection of finite ion temperature, high amplitude plasma blobs  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

148

Distinctive plasma density features of the topside ionosphere and their electrodynamics investigated during southern winter  

NASA Astrophysics Data System (ADS)

This study utilizes a novel technique to map the Defense Meteorological Satellite Program (DMSP) data across the two hemispheres to learn about the morphology and plasma composition of the topside ionosphere, and the underlying ionospheric dynamics. In the southern winter hemisphere, the regional maps tracked a heavy-ion (Ni-O+) trough, aurora zone, polar hole, and large plasma density depletion. The latter appeared in the region of the South Atlantic Magnetic Anomaly (SAMA). The electron temperature (Te) map detected the thermal characteristics of these features, while the plasma drifts and flux maps tracked their dynamics. Results show that there were special electrodynamic effects in the SAMA region due to the low magnetic field and high conductivity. These increased the vertical downward (VZ) and the westward (VY) drifts. Independently, the VZ and VY maps registered the affected area that was depleted in heavy ions and rich in light ions. Some field-aligned profiles tracked the impact of these SAMA effects on the heavy-ion trough, which was a stagnation trough and appeared markedly differently at different longitudes. At trough latitudes ((56 +/- 4)°S (geomagnetic) when Dstav = 0 nT), the elevated electron temperatures forming a Te peak indicated subauroral heating effects. A statistical study modeled the magnetic activity dependence of the Te peak's magnitude and location and revealed their linear correlation with the activity level. Statistically, the Te peak increased [10.226 +/- 1.355]°K and moved equatorward [0.051 +/- 0.009]° (geomagnetic) per 1 nT decrease in the averaged Dst index. Per 1 nT increase in the averaged AE index, its magnitude increased [1.315 +/- 0.444]°K and the equatorward movement was [0.014 +/- 0.003]°.

Horvath, Ildiko; Lovell, Brian C.

2009-01-01

149

Evaluations of the impedance probe measurements in the ionosphere and its application to plasma diagnostics  

NASA Astrophysics Data System (ADS)

The impedance probe is a powerful tool to measure the electron density. The frequency variations of the probe impedance give upper hybrid resonance (UHR) frequency. We can accurately determine the electron density from the UHR frequency. In addition to the UHR frequency, the probe impedance in ionospheric plasmas shows characteristic variations. Especially, the ion sheath surrounding the probe significantly affects the probe impedance. In this presentation, we will discuss the instrumental development for the next sounding rocket observation and evaluations of the probe impedance via electron hybrid simulations. The sheath capacitance is a useful parameter to the ionospheric plasma diagnostics. The impedance probe onboard the sounding rocket demonstrated that the Debye length of the Maxwellian plasma can be estimated from the sheath capacitance (Oya and Aso, 1969; Suzuki et al., submitted). The measurements of the sheath capacitance do not require the frequency sweep in contrast to the detection of the UHR frequency. For the next sounding rocket experiment, we design the impedance probe instrument to measure the sheath capacitance frequently. The improvement realizes both the high time resolution measurements from the sheath capacitance and the high accurate measurements from the UHR frequency. We will show the concept of the instrument. We also perform electron hybrid simulations in order to evaluate the impedance probe measurements including the effect of the ion sheath. Since the ion sheath significantly modifies the probe impedance at lower frequencies in comparison to that around the UHR frequency, it is necessary to take into account the effect of the sheath in evaluating the probe impedance. We develop a particle-in-cell code based on the electron hybrid code, which treats cold electrons as fluid and hot electrons as particles (Katoh, 2003), so as to consider the formation of the ion sheath. We will report on the present state of the electron hybrid simulations of the impedance probe measurements.

Suzuki, T.; Ono, T.; Kumamoto, A.; Katoh, Y.; Terada, N.; Uemoto, J.

2009-12-01

150

Plasma wave turbulence due to the wake of an ionospheric sounding rocket  

NASA Astrophysics Data System (ADS)

In the ionosphere, a rarefied plasma region called "plasma wake" is formed behind a sounding rocket. Based on a one-dimensional Vlasov-Maxwell simulation, it was suggested that electron distribution functions in the plasma wake behind spacecraft are different from the Maxwell-Boltzmann distribution function [Singh et al., 1987]. Thus, plasma waves are expected to be generated in the wake of a sounding rocket. Some studies reported plasma waves around the wake of artificial satellites [Keller et al., 1997] and solar system bodies such as Moon [Nakagawa et al., 2003]. Yamamoto (2000) is the first study that focused on plasma waves induced by sounding rockets on the basis of the results of several rocket experiments. He compared the observed wave frequency with the electron number density in the wake and indicated plasma waves could be generated inside the rocket wake. In order to investigate the properties of the waves in more detail (e.g. spin-phase dependence, generation mechanism, etc.), we are now analyzing the data of electron number density and electric fields of plasma waves in mid-latitude ionosphere by an impedance probe and a plasma wave receiver, which were installed on the sounding rocket S-520-26. In the analysis, we have found plasma waves in a frequency range of 1.3-2.4 MHz (hereinafter called Group-A) as well as those in a frequency range between 0.02 MHz to about 0.6 fce (Group-B), and those in a frequency range from about 0.5 fce to 0.9 fce (Group-C), where fce is the electron cyclotron frequency deduced from the IGRF model. The Group-A emissions are similar to the waves observed in previous studies [Yamamoto, 2000]. Comparison with the data of the impedance probe has suggested the Group-A waves are short-wavelength electrostatic waves including upper-hybrid resonance (UHR) mode waves and electrostatic electron cyclotron harmonic (ESCH) waves. On the other hand, the Group-B and Group-C waves are whistler mode waves. Besides, the analysis with the rocket attitude data has clarified that the Group-A emissions are enhanced when the antenna element pointed in the directions of 320°-20° and 150°-250° in spin-phase angle while that the Group-B waves have been observed clearly when the antenna element pointed to 50°-110° and 200°-300°, and that the Group-C waves are found in 90°-160°. The spin-phase dependences suggest inhomogeneous distributions of the occurrence regions of plasma instabilities with respect to the wake structure, or anisotropy of the wave propagation in plasma. In order to discuss the generation mechanism of the observed plasma waves, we have performed numerical calculations of linear growth rate of plasma waves by assuming anisotropic velocity distribution functions with an electron beam or temperature anisotropy. As a result, we could confirm positive linear growth rates in wave numbers and frequency ranges of UHR mode waves, ESCH waves, and electrostatic whistler mode waves. Actual distribution functions around the rocket wake, however, might not be simple as we assumed. Therefore, further studies with using Vlasov-Maxwell simulation will be needed.

Endo, K.; Kumamoto, A.; Ono, T.; Katoh, Y.

2013-12-01

151

The collective gyration of a heavy ion cloud in a magnetized plasma. [in earth ionosphere  

NASA Technical Reports Server (NTRS)

Results are reported from the ionospheric barium injection experiments CRIT I and CRIT II, during both of which a long-duration oscillation was observed with a frequency close to the gyrofrequency of barium and a time duration of about 1 sec. A model for the phenomenon which was proposed for CRIT I is compared to the results from CRIT II, which made a much more complete set of measurements. The model follows the motion of a low-beta ion cloud through a larger ambient plasma. As the ions move across the magnetic field, the space charge is continuously neutralized by magnetic-field aligned electron currents from the ambient ionosphere, drawn by the divergence in the perpendicular electric field. These currents yield a perturbation of the magnetic field related to the electric perturbation by Delta-E/Delta-B is approximately equal to V sub A. The possibility of extending the model to the active region, where the ions are produced in this type of self-ionizing injection experiments, is discussed.

Brenning, N.; Swenson, C.; Kelley, M. C.; Providakes, J.; Torbert, R.

1992-01-01

152

Energetic O+ and H+ Ions in the Plasma Sheet: Implications for the Transport of Ionospheric Ions  

NASA Technical Reports Server (NTRS)

The present study statistically examines the characteristics of energetic ions in the plasma sheet using the Geotail/Energetic Particle and Ion Composition data. An emphasis is placed on the O+ ions, and the characteristics of the H+ ions are used as references. The following is a summary of the results. (1) The average O+ energy is lower during solar maximum and higher during solar minimum. A similar tendency is also found for the average H+ energy, but only for geomagnetically active times; (2) The O+ -to -H+ ratios of number and energy densities are several times higher during solar maximum than during solar minimum; (3) The average H+ and O+ energies and the O+ -to -H+ ratios of number and energy densities all increase with geomagnetic activity. The differences among different solar phases not only persist but also increase with increasing geomagnetic activity; (4) Whereas the average H+ energy increases toward Earth, the average O+ energy decreases toward Earth. The average energy increases toward dusk for both the H+ and O+ ions; (5) The O+ -to -H+ ratios of number and energy densities increase toward Earth during all solar phases, but most clearly during solar maximum. These results suggest that the solar illumination enhances the ionospheric outflow more effectively with increasing geomagnetic activity and that a significant portion of the O+ ions is transported directly from the ionosphere to the near ]Earth region rather than through the distant tail.

Ohtani, S.; Nose, M.; Christon, S. P.; Lui, A. T.

2011-01-01

153

The relative importance of dayside and nightside reconnection on the ionospheric convection system during sudden enhancements of solar wind dynamic pressure: OpenGGCM-CTIM results  

NASA Astrophysics Data System (ADS)

Recent studies have shown that sudden enhancement of solar wind dynamic pressure (Psw) is a significant driver of energy transfer to the magnetosphere-ionosphere (MI) system, generating strong responses such as increase in the cross polar cap potential (CPCP), reduction of the polar cap area, expansion of the auroral oval, etc. This study investigates where, when, and how solar wind energy is deposited into the MI system during sudden solar wind dynamic pressure enhancement, like shocks. We analyze three unique events that occurred during strongly southward, near-zero Bz, and northward IMF by simulating the MI responses with the OpenGGCM-CTIM coupled magnetosphere-ionosphere model. We examine the behavior of dayside and nightside reconnection, and quantify their respective contribution to CPCP, a proxy of ionospheric flow convection. The dayside and nightside reconnection rates (Rd and Rn) are defined to be the open flux per unit time crossing the dayside and nightside open-closed field line boundaries. The relative contributions to CPCP are estimated by fitting the reconnection rates and the modeled CPCP to a widely used linear equation, CPCP = CdRd + CnRn + viscosity, where the correlation coefficients of dayside and nightside reconnection rates Cd and Cn define the quantitative contribution of each merging rate. The model results reproduce the CPCP increase at the arrival of the Psw enhancement, showing good agreement with the observations of Defense Meteorological Satellite Program (DMSP) spacecraft and predictions from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) technique. For all three events, the dayside reconnection reacts first, increasing its rate right after the Psw increase. The nightside reconnection intensifies about 10-20 minutes later due to the solar wind propagation to the magnetotail. For southward IMF, dayside reconnection contributes to the CPCP increase twice as much as the nightside one, while for northward IMF, nightside reconnection dominates.

Connor, H. K.; Zesta, E.; Ober, D. M.; Raeder, J.

2013-12-01

154

International Reference Ionosphere: Past, present, and future. I - Electron density. II - Plasma temperatures, ion composition and ion drift  

NASA Technical Reports Server (NTRS)

The most important investigations leading to the International Reference Ionosphere 1990 (IRI-90) are overviewed, and the latest version of the model is described. The shortcomings and limitations of the IRI-90 are pointed out, together with the ways of overcoming them. The list of studies that the IRI group has yet to carry out includes the investigations of magnetic storm effects as the highest priority. This paper discusses determinations of and the available data on the electron density, plasma temperatures, ion composition, and ion drift in the ionosphere, together with future improvements needed on these parameters.

Bilitza, D.; Rawer, D.; Bossy, L.; Guliaeva, T.

1993-01-01

155

Plasma wave turbulence due to the wake of an ionospheric sounding rocket  

NASA Astrophysics Data System (ADS)

A sounding rocket moving in the ionosphere generally interacts with surrounding plasma. Because this affects in-situ measurement data, it is very important to understand the physics of the interaction between the ionosphere and a moving vehicle. For instance, a rarefied plasma region called "plasma wake" is formed behind a sounding rocket. Several previous studies based on rocket experiments have suggested that upper-hybrid resonance (UHR) mode waves are excited in a rocket wake. A wake turbulence model has been proposed as a possible explanation for the waves where two stream instability occurs in the wake center owing to the incident plasma flow from the both sides of the wake edges. Thus, plasma waves are generated and have been observed by the wave receivers onboard the rockets. Plasma waves in a wake have been reported not only around sounding rockets but also around solar system bodies such as Moon. As for a rocket wake, the generation mechanism of the waves has been investigated by using wave receivers with time resolutions worse than 500 msec. They are, however, not enough for detailed investigations about the plasma wave generations and propagations. To discuss the properties of the plasma waves caused around a rocket wake, we have analyzed the data of electric fields and electron number density in the S-520-26 sounding rocket experiment, which was performed at Uchinoura, Japan, on January 12, 2012. The rocket reached an altitude of 298 km, and the data has been obtained four or five times in one spin period of the rocket by using a newly developed digital plasma wave monitor and an impedance probe, whose time resolutions are about 260 msec. In the observation, enhancement of plasma waves has been observed in two frequency ranges from 0.02 to 0.9 MHz (LF range), and from 1.3 to 2.4 MHz (MF range). The frequency range of the MF emissions is around the UHR frequency, which is determined based on the IGRF magnetic field model and electron number density measured by the impedance probe. However, the lowest frequency of the emissions is almost the same as the Z-mode cutoff frequency, particularly in higher altitude range than 280 km. The wave spectra are similar to those observed by the previous studies. The frequency range of the LF emissions is found to be that of whistler mode branch. Based on the rocket attitude, it is suggested that the electric fields of the LF and MF emissions are nearly perpendicular and parallel to the wake structure, respectively. If we can assume that the observed waves are generated around the rocket, they have to be electrostatic waves because the wave length should be shorter than the size of the disturbed region. We have performed calculations of plasma dispersion relations with assuming some anisotropic velocity distribution functions of electrons expected around the wake, and deduced the linear growth rates, group velocities, etc. We compare the observational results with calculated ones, and discuss the generation mechanisms of the plasma waves.

Endo, Ken; Kumamoto, Atsushi; Oya, Hiroshi; Ono, Takayuki; Katoh, Yuto

2013-04-01

156

Plasma waves stimulated by electron beams in the lab and in the auroral ionosphere  

NASA Astrophysics Data System (ADS)

Energetic electron beams are frequently used as active probes of space plasmas. Often the assumed test particle nature of these electrons is violated when the electron beam stimulates plasma wave emissions. Such complex phenomena have been observed on rockets and satellites and are being modeled in laboratory plasmas. The large vacuum chamber at NASA Johnson Space Center in Houston, Texas has been used for modeling F-region type ionospheric plasmas. A VLF receiver has been flown into an auroral plasma and the spectra from this flight will be compared to VLF spectra obtained in the NASA/JSC laboratory chamber. The electron beam is believed to have produced beam plasma discharge (BPD) on the rocket similar to that seen in the lab. At times during the rocket flight the electron beam was operated at 4 kilovolts and the electron current modulated at 3 kilohertz from 0 to 80 milliamps. This resulted in the beam pulsing in and out of BPD and a variety of propagating wave modes. The laboratory VLF electric field spectra during BPD show a characteristic peak at a few kilohertz with amplitudes over 100 mV/m. This peak broadens and moves to higher frequencies as the current is increased at a fixed electron voltage. Other features of BPD in the lab as seen in the VLF spectra include appearance of the spectral peak prior to optical BPD threshold, differences between E and B spectra below the peak, and oscillation in and out of BPD, even under a steady-state electron gun current on time scales of 100 ms.

Holzworth, R. H.; Harbridge, W. B.; Koons, H. C.

1982-10-01

157

Space Shuttle Exhaust Modifications of the Mid-Latitude Ionospheric Plasma As Diagnosed By Ground Based Radar  

NASA Astrophysics Data System (ADS)

The Space Shuttle's Orbital Maneuvering System (OMS) engines have been used since the early days of the STS program for active ionospheric modification experiments designed to be viewed by ground based ionospheric radar systems. In 1995, the Naval Research Laboratory initiated the Shuttle Ionospheric Modification with Pulsed Localized Exhaust (SIMPLEX) Program using dedicated Space Shuttle OMS burns scheduled through the US Department of Defense's Space Test Program. SIMPLEX objectives include generation of localized ion-acoustic turbulence and the formation of ionospheric density irregularities for injections perpendicular to the local magnetic field, creating structures which can scatter incident UHF radar signals. We discuss radar observations made during several recent SIMPLEX mid-latitude experiments conducted over the Millstone Hill incoherent scatter radar system in Westford, Massachusetts. OMS engine firings release 10 kg/s of CO2, H2, H2O, and N2 molecules which charge exchange with ambient O+ ions in the F region, producing molecular ions and long lived electron density depletions as recombination occurs with ambient electrons. Depending on the magnetic field angle, the high velocity of the injected reactive exhaust molecules relative to the background ionosphere can create longitudinal propagating ion acoustic waves with amplitudes well above normal thermal levels and stimulate a wide variety of plasma instability processes. These effects produce high radar cross section targets readily visible to the Millstone Hill system, a high power large aperture radar designed to measure very weak scatter from the quiescent background ionosphere. We will survey the plasma instability parameter space explored to date and discuss plans for future SIMPLEX observations.

Lind, F. D.; Erickson, P. J.; Bhatt, A.; Bernhardt, P. A.

2009-12-01

158

Observations of solar-wind-driven progression of interplanetary magnetic field B{sub Y}-related dayside ionospheric disturbances  

SciTech Connect

Observations from August 2, and 3, 1991, of poleward progressing, dayside convection disturbances accompanied by geomagnetic perturbations and ionospheric radio wave absorption have been analyzed and compared to variations in the solar wind parameters as observed from the IMP 8 satellite. The convection disturbances appear to start at dayside cusp latitudes from where they progress antisunward to high latitudes. The reported observations have enabled calculations of the progression directions and velocities and precise estimates of the delays between solar wind variations as measured by the IMP 8 satellite and ionospheric convection changes as observed from an array of polar magnetic observatories. The progressing ionospheric disturbance events occur during intervals of southward interplanetary magnetic fields (negative interplanetary magnetic field (IMF) B{sub Z} component); they are found to be closely related to variations of the east-west component B{sub Y} of the IMF. The close coupling between the solar wind and the polar ionosphere(s) is explained in an open magnetospheric model in which the geomagnetic field extending from a localized region of the dayside polar cap merges with the southward interplanetary field. Variations in the IMF B{sub Y} component are reproduced in corresponding modulations of the east-west component of the plasma flow at the ionospheric foot points of the connecting `open` field lines. The perturbations of the plasma flow persist while the open field lines are convected with the ionospheric plasma across part of the dayside polar cap. The observed geomagnetic perturbations result from the combined effects of field-aligned currents and horizontal ionospheric currents, notably the convection-related Hall currents. The associated radio wave absorption events are explained as the result of E region electron heating by the horizontal electric fields associated with the convection enhancements. 48 refs., 16 figs., 3 tabs.

Stauning, P.; Friis-Christensen, E. [Danish Meterological Institute, Copenhagen (Denmark)] [Danish Meterological Institute, Copenhagen (Denmark); Clauer, C.R. [Univ. of Michigan, Ann Arbor, MI (United States)] [Univ. of Michigan, Ann Arbor, MI (United States)

1995-05-01

159

Dusty plasmas at the Moon: The role of dust grain capacitance and implications for the lunar ionosphere  

NASA Astrophysics Data System (ADS)

Indirect evidence for the existence of dusty plasmas at the Moon comes from observations of dust in the lunar exosphere, a denser than expected lunar ionosphere, and the fact that the Moon is constantly immersed in plasma and its sunlit surface emits photoelectrons. Evidence for the presence of exospheric dust comes from several observations acquired during the Apollo era, while radio occultation experiments onboard the Soviet missions of Luna 19 and 22, as well as more recently aboard the Japanese Kaguya mission, appear to indicate the lunar ionosphere can reach concentrations of ˜100-1000 electrons cm{}(-3) . In the dust-electron model it is proposed that these observations are related, and that the photoemission of electrons from positively-charged exospheric dust could be responsible for observations of a denser than expected lunar ionosphere. Being dominated by the photoemission of electrons, the resulting dusty plasma is expected to behave differently from those previously studied in the outer solar system where photocurrents can often be neglected. Therefore, it is particularly important to consider the effects of the irregular and fractal shapes of the exospheric dust grains on their capacitance and photoemissive properties. In this presentation we discuss the evidence related to presence of dusty plasmas at the Moon, the role that grain shapes play in the capacitance and photoemissive properties of dust, and how the resulting properties of the dusty plasmas may differ from those previously studied in the outer solar system.

Collier, Michael; Stubbs, Timothy; Glenar, David; Zimmerman, Michael

160

Mechanisms of Ionospheric Mass Escape  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

161

Convection of Plasmaspheric Plasma into the Outer Magnetosphere and Boundary Layer Region: Initial Results  

NASA Technical Reports Server (NTRS)

We present initial results on the modeling of the circulation of plasmaspheric-origin plasma into the outer magnetosphere and low-latitude boundary layer (LLBL), using a dynamic global core plasma model (DGCPM). The DGCPM includes the influences of spatially and temporally varying convection and refilling processes to calculate the equatorial core plasma density distribution throughout the magnetosphere. We have developed an initial description of the electric and magnetic field structures in the outer magnetosphere region. The purpose of this paper is to examine both the losses of plasmaspheric-origin plasma into the magnetopause boundary layer and the convection of this plasma that remains trapped on closed magnetic field lines. For the LLBL electric and magnetic structures we have adopted here, the plasmaspheric plasma reaching the outer magnetosphere is diverted anti-sunward primarily along the dusk flank. These plasmas reach X= -15 R(sub E) in the LLBL approximately 3.2 hours after the initial enhancement of convection and continues to populate the LLBL for 12 hours as the convection electric field diminishes.

Ober, Daniel M.; Horwitz, J. L.

1998-01-01

162

GPS TEC and scintillation measurements from the polar ionosphere during the October 2003 storm  

NASA Astrophysics Data System (ADS)

Severe ionospheric storms occurred at the end of October 2003. During the evening of 30 October a narrow stream of high electron concentration plasma crossed the polar cap in the antisunward ionospheric convection. A GPS scintillation receiver in the European high arctic, operating at 1.575 GHz, experienced both phase and amplitude scintillation on several satellite-to-ground links during this period. Close examination of the GPS signals revealed the scintillation to be co-located with strong gradients in Total Electron Content (TEC) at the edge of the plasma stream. The gradient-drift instability is a likely mechanism for the generation of the irregularities causing some of the scintillation at L band frequencies during this storm. The origin of the high TEC is explored and the possible implications of the work for scintillation forecasting are noted. The results indicate that the GPS scintillation over Svalbard can originate from traceable ionospheric plasma structures convecting from the American sector.

Mitchell, C. N.; Alfonsi, L.; De Franceschi, G.; Lester, M.; Romano, V.; Wernik, A. W.

2005-05-01

163

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

164

Plasma heating, plasma flow and wave production around an electron beam injected into the ionosphere  

NASA Technical Reports Server (NTRS)

A brief historical summary of the Minnesota ECHO series and other relevant electron beam experiments is given. The primary purpose of the ECHO experiments is the use of conjugate echoes as probes of the magnetosphere, but beam-plasma and wave studies were also made. The measurement of quasi-dc electric fields and ion streaming during the ECHO 6 experiment has given a pattern for the plasma flow in the hot plasma region extending to 60m radius about the ECHO 6 electron beam. The sheath and potential well caused by ion orbits is discussed with the aid of a model which fits the observations. ELF wave production in the plasma sheath around the beam is briefly discussed. The new ECHO 7 mission to be launched from the Poker Flat range in November 1987 is described.

Winckler, J. R.; Erickson, K. N.

1986-01-01

165

Model of the high-latitude ionospheric convection pattern during southward interplanetary magnetic field using DE 2 data  

NASA Technical Reports Server (NTRS)

Data from the polar-orbiting satellite DE 2 are used to calculate one-dimensional electrostatic potential distributions across the polar cap region. Using passes that lie within + or - 3 hours MLT of the dawn-dusk line, various parameters of the polar potential distribution (location and magnitude of the maxima and minima, location of the zero potential point, etc.) are analyzed in relation to each other and to the IMF. The resulting dependences are used to derive a two-dimensional model of the distribution of the electrostatic potential in the high-latitude ionosphere during times of southward IMF. This model can be generated using as inputs either the ionospheric potential parameters or, based on the relationships analyzed here, the IMF conditions. The capabilities of the resulting mathematical model are illustrated, and the importance of retaining a flexibility in the model to accommodate individual observations is emphasized.

Hairston, M. R.; Heelis, R. A.

1990-01-01

166

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

167

Evidence of auroral oval TEC enhancement and simultaneous plasma patch break-off events in the Arctic and Antarctic ionosphere during the initial phase of a geomagnetic storm event at equinox, 26 September 2011  

NASA Astrophysics Data System (ADS)

A moderate geomagnetic storm during 26-27 September 2011 instigated ionospheric TEC responses in the high latitude regions, imaged in this dual-hemispheric study using the ionospheric reconstruction tool MIDAS (Multi-Instrument Data Analysis System). This case study showcases the current capabilities of GPS inversion tomography at high latitudes, given the improvement in ground-based receiver distribution in the polar reaches during the last decade. Several interesting features of the high latitude response are highlighted. During the initial phase of the storm (Dst+ increase signature), a ring feature in the TEC was imaged around the position of the Arctic auroral oval that persisted for over an hour. Verification of the auroral oval position and incident particle precipitation was provided by the SSUSI ultra-violet imager and SSJ/4 spectrometer on-board the polar-orbiting DMSP satellites. Shortly after the ring feature dissipated, two consecutive and defined plasma patch break-off events occurred within the North American sector, with anti-sunward convection then circulating the TEC enhancements over Greenland and Iceland. Apparent during the main phase of the storm (Dst- signature), these break-off events were likely triggered by switching periods of the interplanetary magnetic field (IMF) from southward (Bz-) to northward (Bz+) under constant By+ conditions projected at the magnetopause. A coincident patch break-off event was imaged in the Antarctic in the local dawn-noon sector; this simultaneity may be attributed to the more balanced incidence angle of the IMF during equinox upon the Northern and Southern hemispheres. Finally, the ionospheric trough was identified over Scandinavia and Europe as a clear band of depletion between the storm-enhanced dayside electron density and expansion of the auroral zone during the main phase of the storm. This study demonstrates that, in combination with other instruments, GPS tomography has become a useful tool providing a unique view on the physical processes occurring in the Arctic and Antarctic ionospheres.

Kinrade, Joe; Mitchell, Cathryn; Paxton, Larry; Bust, Gary

2013-04-01

168

Dawn and dusk sector comparisons of small-scale irregularities, convection, and particle precipitation in the high-latitude ionosphere  

E-print Network

backscattered signals from field-aligned electron density irregularities. These irregular- ities have scale field and precipitation-induced electron-density gradients. INDEX TERMS: 2760 Magnetospheric PhysicsDawn and dusk sector comparisons of small-scale irregularities, convection, and particle

Shepherd, Simon

169

In-situ studies of plasma irregularities in high latitude ionosphere with the ICI-2 sounding rocket within the 4DSpace project  

NASA Astrophysics Data System (ADS)

Ionospheric plasma is often characterized by irregularities, instabilities, and turbulence. Two regions of the ionospheric F-layer are of particular interest: low-latitudes for the equatorial anomaly and electrojet, and high-latitude regions where the most dynamic phenomena occur due to magnetic field lines coupling to the magnetosphere and the solar wind. The spectra of plasma fluctuations in the low-latitude F-layer usually exhibit a power law with a steeper slope at high frequencies [1]. Until recently, there was no clear evidence of the corresponding double slope spectra for plasma fluctuations in the high latitude ionospheric F-layer, and this difference was not well understood. We report the first direct observations of the double slope power spectra for plasma irregularities in the F-layer of the polar ionosphere [2]. The ICI-2 sounding rocket, which intersected enhanced plasma density regions with decameter scale irregularities in the cusp region, measured the electron density with unprecedented high resolution. This 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 gyro-frequency. The double slope spectra are further supported by the results from the ICI-3 sounding rocket. Double slope spectra were not resolved in previous works presumably due to limited resolution of instruments. The study is a part of the 4DSpace initiative for integrated studies of the ionospheric plasma turbulence with multi-point, multi-scale in-situ studies by sounding rockets and satellites, and numerical and analytical models. A brief overview of the 4DSpace initiative is given. [1] M.C. Kelley, The Earth’s Ionosphere Plasma Physics and Electrodynamics (Elsevier, Amsterdam 2009). [2] A. Spicher, W. J. Miloch, and J. I. Moen, Geophys. Res. Lett. 40, (in press, accepted 13.02.2014).

Miloch, Wojciech; Moen, Joran; Spicher, Andres

170

Observation of GNSS signal perturbations due to HF heating induced plasma irregularities in the high latitude ionosphere  

NASA Astrophysics Data System (ADS)

Perturbations of the Total Electron Content (TEC) during HF heating experiments in the high latitude ionosphere are presented. Several experiments were carried out in December 2010 by the EISCAT heating facility in Ramsfjordbotn, Norway. Electromagnetic pumping waves were transmitted along the geomagnetic field lines with varying heating intervals. TEC has been derived for the experiment times, based on the measurements of two high rate dual frequency GNSS receivers placed in appropriate locations close to the facility. It has been previously reported that perturbations of GNSS signals can be found due to ionospheric plasma irregularities caused by high power radio waves. In the experiments presented here, HF ordinary mode beams were directed with elevation angle of 78 degrees in north-south plane transmitting at a frequency around 4 MHz. The center of the perturbed area in the F region ionosphere is estimated to be 41 km south of the facility. The heating and relaxation intervals varied between 10 and 180 seconds. EISCAT UHF radar measurements showed an enhancement of the electron temperature and electron density irregularity in the altitudes corresponding to the estimated piercing points of the GNSS satellite-receiver links. The variations in TEC measurements are identified from the data taken from GNSS receivers placed in Ramsfjordbotn and in Tromsø with a separation of approximately 14 km. During the heating experiments GLONASS satellites are in the field of view of the receivers at high elevation angle. The links between a satellite and a receiver crossing the estimated heating area is capable of providing information about plasma irregularities along the intersection. The simultaneous measurements from the two different receivers allow detecting horizontal structures in the vicinity of the perturbed ionospheric plasmas if the distances between two piecing points are comparable to the size of heated area. The TEC variations are analyzed with regard to the relative distance between each piercing point and the heating center over a series of heating intervals. It is shown that the effects of successive changes of the heating times on the perturbed plasma density structures can be implied from the GNSS TEC signals. The results suggest that the oscillation signature of the TEC may result from the irregularities in the plasmas excited by the different HF heating intervals.

Sato, Hiroatsu; Jakowski, Norbert; Rietveld, Michael; Borries, Claudia; Wilken, Volker

171

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

E-print Network

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.

Benjamin D. G. Chandran

2004-07-18

172

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)

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.

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

1993-01-01

173

Nonlinear coupling of lower hybrid waves to the kinetic low-frequency plasma response in the auroral ionosphere  

NASA Astrophysics Data System (ADS)

A hybrid kinetic-fluid model is developed which is relevant to lower hybrid spikelets observed in the topside auroral ionosphere [Vago et al., 1992; Eriksson et al., 1994]. In contrast to previous fluid models [Shapiro et al., 1995; Tam and Chang, 1995; Seyler, 1994; Shapiro et al., 1993] our linear low frequency plasma response is magnetized and kinetic. Fluid theory is used to incorporate the nonlinear wave coupling. Performing a linear stability analysis, we calculate the growth rate for the modulational instability, driven by a lower hybrid wave pump. We find that both the magnetic and kinetic effects inhibit the modulational instability.

Sanbonmatsu, K. Y.; Goldman, M. V.; Newman, D. L.

174

Convective dust clouds driven by thermal creep in a complex plasma.  

PubMed

Steady-state clouds of microparticles were observed, levitating in a low-frequency glow discharge generated in an elongated vertical glass tube. A heated ring was attached to the tube wall outside, so that the particles, exhibiting a global convective motion, were confined vertically in the region above the location of the heater. It is shown that the particle vortices were induced by the convection of neutral gas, and the mechanism responsible for the gas convection was the thermal creep along the inhomogeneously heated tube walls. The phenomenon of thermal creep, which commonly occurs in rarefied gases under the presence of thermal gradients, should generally play a substantial role in experiments with complex plasmas. PMID:19113560

Mitic, S; Sütterlin, R; Höfner, A V Ivlev H; Thoma, M H; Zhdanov, S; Morfill, G E

2008-12-01

175

Convective Dust Clouds Driven by Thermal Creep in a Complex Plasma  

SciTech Connect

Steady-state clouds of microparticles were observed, levitating in a low-frequency glow discharge generated in an elongated vertical glass tube. A heated ring was attached to the tube wall outside, so that the particles, exhibiting a global convective motion, were confined vertically in the region above the location of the heater. It is shown that the particle vortices were induced by the convection of neutral gas, and the mechanism responsible for the gas convection was the thermal creep along the inhomogeneously heated tube walls. The phenomenon of thermal creep, which commonly occurs in rarefied gases under the presence of thermal gradients, should generally play a substantial role in experiments with complex plasmas.

Mitic, S.; Suetterlin, R.; Hoefner, A. V. Ivlev H.; Thoma, M. H.; Zhdanov, S.; Morfill, G. E. [Max-Planck-Institut fuer extraterrestrische Physik, D-85741 Garching (Germany)

2008-12-05

176

Solar wind erosion of the polar regions of the Mars ionosphere  

NASA Astrophysics Data System (ADS)

Measurements conducted with the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) instrument of the Mars Express spacecraft provide data of plasma fluxes that stream away from the polar regions of the Mars ionosphere with energy spectra whose peak value increases with distance from the planetary surface. The observed energy distribution reveals a velocity boundary layer with ionospheric plasma that is eroded from the polar regions of the Mars ionosphere and that extends in the downstream direction within a geometry similar to that present along the polar flanks of the Venus ionosheath. The direction of motion of the ionospheric particles in those fluxes is close to that of the solar wind velocity and is not also oriented in a transverse direction as would have been expected if they were solely accelerated by the convective electric field of the solar wind. The ionospheric plasma eroded and deviated by the solar wind within the boundary layer forms a region whose shape is compatible with that of the asymmetric Mars plasma halo that was inferred from the X-ray emission lines measured with the reflecting grating spectrometer of the XMM-Newton telescope. The latter emission is interpreted as resulting from thermal dissipative processes associated with the transport of solar wind momentum to the polar upper ionosphere where both plasma populations interact with each other. Different conditions are applicable throughout most of the dayside hemisphere where the enhanced interplanetary magnetic field intensities that are observed within the ionosphere should make the interaction of the oncoming solar wind plasma with the ionospheric material less efficient.

Pérez-de-Tejada, H.; Lundin, R.; Durand-Manterola, H.; Reyes-Ruiz, M.

2009-02-01

177

Prompt penetration electric fields (PPEFs) and their ionospheric effects during the great magnetic storm of 30–31 October 2003  

Microsoft Academic Search

We explore the ionospheric effects of prompt penetration electric fields (PPEFs) for a variety of interplanetary magnetic field directions. We use the great magnetic storm of 30–31 October as an example of PPEF effects. For intense southward interplanetary magnetic fields (IMFs), inward plasma sheet convection occurs with the result of magnetospheric ring current formation and an intense magnetic storm. Concurrent

B. T. Tsurutani; O. P. Verkhoglyadova; A. J. Mannucci; A. Saito; T. Araki; K. Yumoto; T. Tsuda; M. A. Abdu; J. H. A. Sobral; W. D. Gonzalez; H. McCreadie; G. S. Lakhina; V. M. Vasyli?nas

2008-01-01

178

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

179

Electric Field Observations of Plasma Convection, Shear, Alfven Waves, and other Phenomena Observed on Sounding Rockets in the Cusp and Boundary Layer  

NASA Technical Reports Server (NTRS)

On December 14,2002, a NASA Black Brant X sounding rocket was launched equatorward from Ny Alesund, Spitzbergen (79 N) into the dayside cusp and subsequently cut across the open/closed field line boundary, reaching an apogee of771 km. The launch occurred during Bz negative conditions with strong By negative that was changing during the flight. SuperDarn (CUTLASS) radar and subsequent model patterns reveal a strong westward/poleward convection, indicating that the rocket traversed a rotational reversal in the afternoon merging cell. The payload returned DC electric and magnetic fields, plasma waves, energetic particle, suprathermal electron and ion, and thermal plasma data. We provide an overview of the main observations and focus on the DC electric field results, comparing the measured E x B plasma drifts in detail with the CUTLASS radar observations of plasma drifts gathered simultaneously in the same volume. The in situ DC electric fields reveal steady poleward flows within the cusp with strong shears at the interface of the closed/open field lines and within the boundary layer. We use the observations to discuss ionospheric signatures of the open/closed character of the cusp/low latitude boundary layer as a function of the IMF. The electric field and plasma density data also reveal the presence of very strong plasma irregularities with a large range of scales (10 m to 10 km) that exist within the open field line cusp region yet disappear when the payload was equatorward of the cusp on closed field lines. These intense low frequency wave observations are consistent with strong scintillations observed on the ground at Ny Alesund during the flight. We present detailed wave characteristics and discuss them in terms of Alfven waves and static irregularities that pervade the cusp region at all altitudes.

Pfaff, R. F.

2009-01-01

180

In situ measurements of plasma irregularity growth in the cusp ionosphere  

E-print Network

that electron density irregularities are a common phenomenon in the F region arctic ionosphere [e.g., Bates these irregularities are closely related to electron density enhancements in high-latitude F region called polar cap than the surrounding background electron density [Buchau et al., 1983; Weber et al., 1984; Crowley et

Bergen, Universitetet i

181

Modeling the martian ionosphere  

NASA Astrophysics Data System (ADS)

The accessibility of the Martian atmosphere to spacecraft provides an opportunity to study an ionosphere that differs from our own. Yet, despite the half century of measurements made at Mars, the current state of the neutral atmosphere and its embedded plasma (ionosphere) remains largely uncharacterized. In situ measurements of the neutral and ionized constituents versus height exist only from the two Viking Landers from the 1970s. Subsequent satellite and remote sensing data offer sparse global coverage of the ionosphere. Thermal characteristics of the plasma environment are not well understood. Patchy crustal magnetic fields interact with the Martian plasma in a way that has not been fully studied. Hence, investigating the coupled compositional, thermal and crustal-field-affected properties of the ionosphere can provide insight into comparative systems at Earth and other planets, as well as to atypical processes such as the solar wind interaction with topside ionospheric plasma and associated pathways to escape. Ionospheric models are fundamental tools that advance our understanding of complex plasma systems. A pre-existing one-dimensional model of the Martian ionosphere has been upgraded to include more comprehensive chemistry and transport physics. This new BU Mars Ionosphere Model has been used to study the composition, thermal structure and dynamics of the Martian ionosphere. Specifically: the sensitivity of the abundance of ions to neutral atmospheric composition has been quantified, diurnal patterns of ion and electron temperatures have been derived self-consistently using supra-thermal electron heating rates, and the behavior of ionospheric plasma in crustal field regions was simulated by constructing a two-dimensional ionospheric model. Results from these studies were compared with measurements and show that (1) ion composition at Mars is highly sensitive to the abundance of neutral molecular and atomic hydrogen, (2) lighter ions heat up more efficiently than heavier ones and provide additional heating sources for cooler plasma, and (3) crustal field morphology affects plasma dynamics and structure at Mars in a way that is consistent with observations. Finally, model predictions of ion composition and plasma temperatures are provided for observations to be made by several instruments on board the upcoming 2013 MAVEN orbiter.

Matta, Majd Mayyasi

182

Application of lightning discharge generated radio atmospherics/tweeks in lower ionospheric plasma diagnostics  

NASA Astrophysics Data System (ADS)

Lightning discharges during thunderstorm are the significant natural source of electromagnetic waves. They generate electromagnetic pulses, which vary from few Hz to tens of MHz, but the maximum radiated energy is confined in extremely low (ELF: 3-3000Hz) and very low (VLF: 3-30 KHz) frequency band. These pulsed signals with frequency dispersion are known as radio atmospherics or tweeks. These waves propagate through the process of multiple reflections in the earth-ionosphere waveguide over long distances with very low attenuation (2-3 dB/1000km). Since these waves are reflected by lower boundary of ionosphere, these are used extensively for probing the D-region ionosphere. D-region is important to the space weather, as well as the submarine communication and navigational aid. In this perspective the measurement of electron density profiles of the D-region is undoubtedly of great interest to both the development of reliable models and radio wave propagation. Earlier work on the tweeks is mainly focused to the theoretical considerations related to polarization, waveform analysis, and occurrence time and propagation mechanism. In this study we investigate tweeks to determine the equivalent night time electron densities at reflection height of the D-region. Distance traveled by the VLF waves from the causative lightning discharges to the receiving station has also been calculated. Tweeks recorded at a low latitude ground station of Allahabad (Geomag. lat. 16.050 N) during the night of 23 March 2007 have been used in the present analysis. Based on the analysis of the fundamental cut-off frequency of tweeks, the estimated equivalent electron density of the D-region has been found to be in the range of ~20 to 25 el/cm3 at ionospheric reflection height of ~80 to 95 km respectively. Propagation distance in Earth-Ionosphere wave guide (EIWG) from causative lightning source to experimental site varies from ~1500 to 8000 km.

Maurya, A. K.; Singh, R.; Veenadhari, B.; Pant, P.; Singh, A. K.

2010-02-01

183

Internal consistency of the Tsyganenko magnetic field model and the Heppner-Maynard empirical model of the ionospheric electric field distribution  

NASA Astrophysics Data System (ADS)

The Tsyganenko magnetic field models (1987 and 1989) are used to map the electric field distribution of Heppner and Maynard (1987) into the geomagnetic tail and to infer the velocity of the central plasma sheet (CPS) convective flow. Qualitatively different convection patterns are obtained from the two Tsyganenko models. Results obtained with the 1987 model predict a narrow jet of earthward moving plasma in the center of the CPS, while the 1989 model predicts relatively uniform earthward convection throughout the CPS. It is concluded from in situ observations of the CPS convection that the 1989 model provides the most realistic mapping. The convection distributions derived from measurements are compared with convection patterns inferred from the two magnetic field models and the Heppner-Maynard ionospheric convection model to help evaluate the magnetic field models. The results of this comparison can be used to direct research aimed at improving the magnetic field models.

Donovan, E. F.; Rostoker, G.

1991-06-01

184

Plasma convection in the nightside magnetosphere of Saturn determined from energetic ion anisotropies  

NASA Astrophysics Data System (ADS)

The Cassini Ion and Neutral Camera measures intensities of hydrogen and oxygen ions and neutral atoms in the Saturnian magnetosphere and beyond. We use the measured intensity spectrum and anisotropy of energetic hydrogen and oxygen ions to detect, qualify, and quantify plasma convection. We find that the plasma azimuthal convection speed relative to the local rigid corotation speed decreases with radial distance, lagging the planetary rotation rate, and has no significant local time dependences. Plasma in the dusk-midnight quadrant sub-corotates at a large fraction of the rigid corotation speed, with the primary velocity being azimuthal but with a distinct radially outward component. The duskside velocities are similar to those obtained from earlier orbits in the midnight-dawn sector, in contrast to the depressed velocities measured at Jupiter using Energetic Particles Detector measurements on the Galileo spacecraft in the dusk-midnight quadrant. We find significant radial outflow in most of the nightside region. The radial component of the flow decreases with increasing local time in the midnight-dawn sector and reverses as dawn is approached. This and previous results are consistent with a plasma disk undergoing a centrifugally induced expansion as it emerges into the nightside, while maintaining partial rotation with the planet. The magnetodisk expansion continues as plasma rotates across the tail to the dawnside. We do not see evidence in the convection pattern for steady state reconnection in Saturn's magnetotail. The outermost region of the magnetodisk, having undergone expansion upon emerging from the dayside magnetopause confinement, is unlikely to recirculate back into the dayside. We conclude that plasma in the outer magnetodisk [at either planet] rotates from the dayside, expands at the dusk flank, but remains magnetically connected to the respective planet while moving across the tail until it interacts with and is entrained into the dawnside magnetosheath flow. This interaction causes plasma in the outer magnetospheric regions of Jupiter and Saturn to decouple from the planet and exhaust tailward down a dawnside low latitude boundary layer. Magnetospheric plasma will also interact with the dayside magnetosheath plasma, moving across the boundary [enhanced by shear instability] and into the magnetosheath, where it is lost to the magnetosphere with the magnetosheath flow.

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

2014-02-01

185

In situ measurements of ionospheric plasma turbulence over five frequency decades: Heritage flight of the Plasma Local Anomalous Noise Experiment (PLANE)  

NASA Astrophysics Data System (ADS)

Observations of ionospheric plasma density and frequency-dependent broadband plasma turbulence made during the heritage flight of the Plasma Local Anomalous Noise Experiment (PLANE) are presented. Rather than record high frequency time series data, the experiment was designed to record Power Spectral Distributions (PSDs) in five decadal frequency bins with upper limits ranging from 1.0 Hz to 10 kHz. Additionally, PLANE was designed distinguish turbulence in the ambient plasma from that local to the spacecraft. The instrument consists of two retarding potential analyzers (RPAs) connected together via a feedback loop to force one analyzer into the I-V trace retardation region at all times. Fluctuations in this measurement are believed to be ambient only as the RPA's voltage would be too high for locally turbulent plasma to surmount the potential barrier, which is nominally at ram energy. The instrument requires pointing along the spacecraft's ram velocity vector to make this measurement, thus requiring stabilization in pitch and yaw. During PLANE's heritage flight, though the satellite's attitude control system failed early in the mission, plasma data were collected during opportune times in which the instrument rotated into and out of the ram. Observations of plasma density and PSDs of high frequency plasma turbulence were recorded on several occasions. Additionally, a plasma source onboard the satellite was used to generate artificial plasma turbulence, and the PLANE data observed periodic structure presumably associated with the rotation of the spacecraft during these source firings. A brief comparison with other high frequency in situ plasma instruments is presented.

Habash Krause, L.; Enloe, C. L.; McHarg, M. G.

2013-12-01

186

Effect of the zonal E × B plasma drift on the electron number density in the low-latitude ionospheric F region at high solar activity near the December solstice  

NASA Astrophysics Data System (ADS)

The variations in the electron number density of the ionospheric F2 layer maximum ( NmF2) under the action of the zonal plasma drift in the geomagnetic west-geomagnetic east direction perpendicularly to the electric ( E) and geomagnetic ( B) fields during a geomagnetically quiet period on December 7, 1989, at high solar activity have been studied based on a three-dimensional nonstationary theoretical model of electron number densities and temperatures in the ionospheric F region. Calculated and measured NmF2 values for 12 low-latitude ionospheric sounding stations have been compared. When the zonal E × B plasma drift is ignored, the NmF2 values become smaller by up to a factor of 3 under nighttime conditions in the low-latitude ionosphere. The average effect of the zonal E × B plasma drift on NmF2 in the low-latitude ionosphere is larger during winter nights than under summer nighttime conditions.

Pavlov, A. V.; Pavlova, N. M.

2013-04-01

187

Macroscopic time and altitude distribution of plasma turbulence induced in ionospheric modification experiments  

Microsoft Academic Search

This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This research concentrated on the time dependence of the heater, induced-turbulence, and electron-density profiles excited in the ionosphere by a powerful radio-frequency heater wave. The macroscopic density is driven by the ponderomotive pressure and the density self-consistently determines the

H. Rose; D. Dubois; D. Russell; A. Hanssen

1996-01-01

188

Equatorial ionospheric plasma structures observed with the C/NOFS satellite and multiple ground-based diagnostics in October 2008  

NASA Astrophysics Data System (ADS)

Comparison of equatorial ionospheric disturbances observed with C/NOFS in-situ measurements and ground-based observations is performed on two days in Oct 2008. Electron density at 400-850km altitudes in the equatorial ionosphere is measured with a Planar Langmuir Probe (PLP) on the Communications/ Navigation Outage Forecast System (C/NOFS) satellite, which was launched in April 2008 in order to monitor and forecast ionospheric scintillation. In early October, 2008, the C/NOFS satellites flew over the American sector around the dip equator at the perigee altitude at dusk. On 5 Oct, strong 250MHz scintillation occurred at the Ancon SCINDA site without much electron density disturbance in C/NOFS measurements. On the other hand, on 10 Oct., lower scintillations were observed with severe electron density disturbance in C/NOFS data. On 5 Oct, the bottom-side irregularities did not reach the C/NOFS perigee altitude. Latitudinal total electron content (TEC) profiles obtained by Low-latitude Ionospheric Sensor Network (LISN) over South America shows smaller latitudinal gradient of TEC on 5 Oct. than on 10 Oct. The under developed Equatorial Ionization Anomaly (EIA) at dusk on 5 Oct can be an evidence of the absence of irregularity upwelling. The high TEC at the dip equator would enhance the scintillation level on 5 Oct. On 10 Oct, the upwelling of the irregularities was also observed by 50MHz radar backscatter observations at Jicamarca. Latitudinal TEC profile of LISN shows well-developed EIA. This allowed the irregularity bubbles to reach the C/NOFS perigee height. LISN-TEC also shows lower values around the equator, which could contribute to lower scintillation levels. Such day-to-day variability of irregularities remains an unresolved issue during solar minimum as well. We will try to understand this variability better by obtaining spectral measurements of high-resolution in-situ data to provide insight into plasma processes, optical and digisonde observations to provide information regarding the bottom-side of the F-region and using observed vertical drifts to model electron density profiles using the SAMI2 model for comparison with the TEC.

Nishioka, M.; Basu, S.; Valladares, C. E.; Roddy, P. A.; Groves, K. M.; Makela, J. J.

2009-12-01

189

Convective amplification of a three-wave parametric instability in inhomogeneous plasma  

SciTech Connect

The three-wave parametric instability in inhomogeneous plasma is revisited and the inconsistency of the convective amplification in previous literatures is resolved. By employing multiple methods, the amplification factor of the decay mode due to the inhomogeneity is confirmed as A=??{sub 0}{sup 2}/(v{sub g1x}v{sub g2x}?{sup ?}), which is independent of the linear damping rate of the decay mode, where ?{sub 0} is the nonlinear growth rate in homogeneous plasma, v{sub g1x} and v{sub g2x} are the group velocities in the x direction of the two decay modes and ?{sup ?} is the derivative of the wavevector mismatch of the three coupled waves due to the plasma inhomogeneity.

Zhao, Aihui; Gao, Zhe [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)] [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2013-11-15

190

Electric Field and Plasma Density Observations of Irregularities and Plasma Instabilities in the Low Latitude Ionosphere Gathered by the C/NOFS Satellite  

NASA Technical Reports Server (NTRS)

The Vector Electric Field Investigation (VEFI) on the C/NOFS equatorial satellite provides a unique data set which includes detailed measurements of irregularities associated with the equatorial ionosphere and in particular with spread-F depletions. We present vector AC electric field observations gathered on C/NOFS that address a variety of key questions regarding how plasma irregularities, from meter to kilometer scales, are created and evolve. The talk focuses on occasions where the ionosphere F-peak has been elevated above the C/NOFS satellite perigee of 400 km as solar activity has increased. In particular, during the equinox periods of 2011, the satellite consistently journeyed below the F-peak whenever the orbit was in the region of the South Atlantic anomaly after sunset. During these passes, data from the electric field and plasma density probes on the satellite have revealed two types of instabilities which had not previously been observed in the C/NOFS data set: The first is evidence for 400-500km-scale bottomside "undulations" that appear in the density and electric field data. In one case, these large scale waves are associated with a strong shear in the zonal E x B flow, as evidenced by variations in the meridional (outward) electric fields observed above and below the F-peak. These undulations are devoid of smaller scale structures in the early evening, yet appear at later local times along the same orbit associated with fully-developed spread-F with smaller scale structures. This suggests that they may be precursor waves for spread-F, driven by a collisional shear instability, following ideas advanced previously by researchers using data from the Jicamarca radar. A second result is the appearance of km-scale irregularities that are a common feature in the electric field and plasma density data that also appear when the satellite is near or below the F-peak at night. The vector electric field instrument on C/NOFS clearly shows that the electric field component of these waves is strongest in the zonal direction. These waves are strongly correlated with simultaneous observations of plasma density oscillations and appear both with, and without, evidence of larger-scale spread-F depletions. These km-scale, quasi-coherent waves strongly resemble the bottomside, sinusoidal irregularities reported in the Atmosphere Explorer satellite data set by Valladares et al. and are believed to cause scintillations of VHF radiowaves. We interpret these new observations in terms of fundamental plasma instabilities associated with the unstable, nighttime equatorial ionosphere.

Pfaff, Robert F.; Freudenreich, H.; Rowland, D.; Klenzing, J.; Liebrecht, C.

2012-01-01

191

The COMPASS-2 satellite and the ground-based LOIS vector sensing radar facility as novel tools for ionospheric plasma diagnostics  

NASA Astrophysics Data System (ADS)

To give a more detailed and complete understanding of physical plasma processes that govern the solar-terrestrial space, and to develop qualitative and quantitative models of the magnetosphere-ionosphere-thermosphere coupling, it is necessary to design and build the next generation of instruments for space diagnostics and monitoring. Novel ground-based wide-area sensor networks, such as the LOFAR Outrigger In Scandinavia (LOIS, LOFAR: Low Frequency Array) radar facility, comprising wide band, and vector-sensing radio receivers with full three-dimensional polarization coverage, and multi-spacecraft plasma diagnostics should help solve outstanding problems of space physics and describe long-term environmental changes. The new digital radio frequency analyzer (RFA) on board the low-orbiting COMPASS-2 satellite was designed to monitor and investigate the ionospheric plasma properties. This two-point ground-based and topside ionosphere-located space plasma diagnostic can be a useful new tool for monitoring and diagnosing turbulent plasma properties. The RFA on board the COMPASS-2 satellite is the first in a series of experiments which is planned to be launched into the near-Earth environment. The main purpose of this presentation is to describe new advanced diagnostic techniques of the near-Earth space plasma and point out the scientific challenges of the COMPASS-2 and LOIS experiments.

Rothkaehl, H.; Bergman, J. E. S.; Thidé, B.; Klos, Z.

2008-04-01

192

Reviewing the Mechanisms Underlying the Pre-reversal Enhancement of the Vertical Plasma Drift in the Low Latitude Ionosphere  

NASA Astrophysics Data System (ADS)

The evening pre-reversal enhancement (PRE) of the zonal electric field and the corresponding vertical plasma drift in the low-latitude ionosphere is an important feature in determining the structure and stability of the ionosphere. There are three competing theories of the cause of the PRE; curl free response [Eccles, 1998a and Rishbeth, 1972], off-equator Hall current divergence [Farley et al., 1986]; and equatorial electrojet current divergence [Harendel and Eccles, 1992]. We review these theories of the PRE cause in the context of field-line-integrated electrodynamics model and then examine the viability of each proposed cause using simplified electrodynamics simulations. While all three physical theories are real physical processes occurring in the evening low latitude ionosphere, we demonstrate that the PRE arises primarily from a curl-free response to the rapid temporal evolution of the vertical electric field as proposed by Eccles [1998a] in support of a short comment by Rishbeth [1972] within his paper on the F region dynamo. The curl-free effect magnitude has three components: (1) the exchange of the dominance of the E region dynamo to the F region dynamo as the E region Pedersen conductivity in conjugant hemispheres decay around sunset, (2) the acceleration of the F region zonal neutral wind as the ion-neutral drag diminishes around sunset, and (3) the apex altitude range of operation of the F region dynamo current. The maximum PRE magnitude occurs at E region sunset when the integrated E region Pedersen conductivities of both hemispheres decrease to less than the integrated F region Pedersen conductivity. The mechanism proposed by Farley et al. [1986] is examined. While the off-equator gradient of the Hall currents can affect the zonal electric field near sunset, it only provides a modest adjustment to the PRE magnitude. The Farley mechanism is limited due to the slow acceleration of the zonal neutral wind prior to E region sunset. It is also demonstrated that the magnitude of the PRE in response to the curl-free effect is affect only very slightly by conductivity conditions within the equatorial electrojet (EEJ). While the EEJ is the most important path of zonal current in the low-latitude ionosphere it is more of a passive load on the F region dynamo electromotive presence. However, the EEJ does dominate the electric field structure below the field-line integrated bottomside F region as presented by Haerendel and Eccles [1992]. These results suggest that the prediction of the PRE magnitude requires accurate knowledge of the decay of the E regions of both hemispheres and of the magnitude and acceleration of the zonal neutral wind in the F region near E region sunset. Eccles, J. V. (1998), A simple model of low-latitude electric fields, J. Geophys. Res., 103, 26,699-26,708. Farley, D. T., E. Bonelli, B.G. Fejer, and M. F. Larsen (1986), The pre-reversal enhancement of the zonal electric field in the equatorial ionosphere, J. Geophys. Res., 91, 13,723-13,728. Haerendel, G. and J. V. Eccles (1992), The Role of the equatorial electrojet in the evening ionosphere, J. Geophys. Res., 97, 1181-1192. Rishbeth, H. (1971), Polarization fields produced by winds in the equatorial F-region, Planet. Space Sci. (19) 357-369.

Eccles, J. V.; St-Maurice, J.; Schunk, R. W.

2013-12-01

193

Identification of the plasma instabilities responsible for decameter-scale ionospheric irregularities on plasmapause field lines  

NASA Astrophysics Data System (ADS)

The mid-latitude SuperDARN radars have revealed decameter-scale ionospheric irregularities during quiet geomagnetic periods that have been proposed to be responsible for the observed low-velocity Sub-Auroral Ionospheric Scatter (SAIS). The mechanism responsible for the growth of such common irregularities is still unknown. Joint measurements by Millstone Hill Incoherent Scatter Radar (ISR) and SuperDARN HF radar located at Wallops Island, Virginia reported by Greenwald et al. [2006] have determined decameter-scale irregularities with low drift velocities in the quiet-time mid-latitude night-side ionosphere. Temperature gradient instability (TGI) is investigated as the cause of irregularities associated with these SuperDARN echoes. The electrostatic dispersion relation for TGI has been extended into the kinetic regime appropriate for SuperDARN radar frequencies by including Landau damping, finite gyro-radius effects, and temperature anisotropy. This dispersion relation allows study of the TGI over a wide range of parameter regimes that have not been considered for such ionospheric applications up to this time. The calculations of electron temperature and density gradients in the direction perpendicular to the geomagnetic field have shown that the TGI growth is possible in the top-side F-region for the duration of the experiment. A time series for the growth rate has been developed for mid-latitude ionospheric irregularities observed by SuperDARN in the top-side F-region [Greenwald et al., 2006]. This time series is computed for both perpendicular and meridional density and temperature gradients. These observations show the role of TGI is dominant over the gradient drift instability (GDI) in this case. Nonlinear evolution of the TGI has been studied utilizing gyro-kinetic "Particle In Cell" (PIC) simulations with Monte Carlo collisions. This allows detailed study of saturation amplitude, particle flux, heat flux, diffusion coefficient, and thermal diffusivity of the resistive drift wave turbulence. The simulation results have been compared with the linear theory. The simulations show important consequences of nonlinear evolution, particularly saturation mechanisms and wave cascading of TGI into the decameter scale regime of the radar observations. A critical comparison of computational modeling results and experimental observations is discussed

Eltrass, Ahmed; Ruohoniemi, J. Michael; Mahmoudian, Alireza; Scales, Wayne; De Larquier, Sebastien; Baker, Joseph; Greenwald, Ray; Erickson, Philip

194

The plasma environment, charge state, and currents of Saturn's C and D rings  

NASA Technical Reports Server (NTRS)

The charge state and associated currents of Saturn's C an D rings are studied by modeling the flow of ionospheric plasma from the mid- to low-latitude ionosphere to the vicinity of the rings. It is found that the plasma density near the C and D rings, at a given radial location, will experience a one to two order of magnitude diurnal variation. The surface charge density (SCD) of these rings can show significant radial and azimuthal variations due mainly to variation in the plasma density. The SCD also depends on structural features of the rings such as thickness and the nature of the particle size distribution. The associated azimuthal currents carried by these rings also show large diurnal variations resulting in field-aligned currents which close in the ionosphere. The resulting ionospheric electric field will probably not produce a significant amount of plasma convection in the topside ionosphere and inner plasmasphere.

Wilson, G. R.

1991-01-01

195

Planetary ionospheres  

NASA Technical Reports Server (NTRS)

An analogy is drawn between the Eath's ionosphere and the existence of ionospheres around other planets or natural satellites. An ionosphere is defined as a series of layers (D, E, E1, F2) and their characteristics are discussed. Emphasis is on the role of solar wind impacting with the potential ionosphere and the subsequent chemical and diffusion processes that can be observed. Data from the MARINER and PIONEER space programs are cited concerning measured electron density and ionospheric refractivity of extraterrestrial ionospheres, then an attempt is made to model these atmospheres based on Earth ionosphere theory.

Bauer, S. J.

1977-01-01

196

Low-rank approximation in the numerical modeling of the Farley-Buneman instability in ionospheric plasma  

NASA Astrophysics Data System (ADS)

We consider numerical modeling of the Farley-Buneman instability in the Earth's ionosphere plasma. The ion behavior is governed by the kinetic Vlasov equation with the BGK collisional term in the four-dimensional phase space, and since the finite difference discretization on a tensor product grid is used, this equation becomes the most computationally challenging part of the scheme. To relax the complexity and memory consumption, an adaptive model reduction using the low-rank separation of variables, namely the Tensor Train format, is employed. The approach was verified via a prototype MATLAB implementation. Numerical experiments demonstrate the possibility of efficient separation of space and velocity variables, resulting in the solution storage reduction by a factor of order tens.

Dolgov, S. V.; Smirnov, A. P.; Tyrtyshnikov, E. E.

2014-04-01

197

Ionospheric irregularity physics modelling  

SciTech Connect

Theoretical and numerical simulation techniques have been employed to study ionospheric F region plasma cloud striation phenomena, equatorial spread F phenomena, and high latitude diffuse auroral F region irregularity phenomena. Each of these phenomena can cause scintillation effects. The results and ideas from these studies are state-of-the-art, agree well with experimental observations, and have induced experimentalists to look for theoretically predicted results. One conclusion that can be drawn from these studies is that ionospheric irregularity phenomena can be modelled from a first principles physics point of view. Theoretical and numerical simulation results from the aforementioned ionospheric irregularity areas will be presented.

Ossakow, S.L.; Keskinen, M.J.; Zalesak, S.T.

1982-01-01

198

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

NASA Astrophysics Data System (ADS)

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.

Sidorova, Larissa

199

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

NASA Astrophysics Data System (ADS)

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.

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

200

The coupling of tail fast flows to ionospheric flow signatures and their relationship to substorm onset  

NASA Astrophysics Data System (ADS)

Earthward convection of the tail plasma sheet is often organized in bursts of fast ion flows restricted in azimuthally narrow channels. It has been shown that Auroral Poleward Boundary Intensifications (PBIs) are often the ionospheric signature of such fast flow channels in the midtail. While PBIs can occur for all IMF orientations and solar wind conditions, they have a clear preference for southward IMF and their occurrence peaks within 1 hour after a substorm onset, with a secondary occurrence peak at 3 hrs after onset. Equatorward flow bursts have been observed in the ionosphere, that are presumably the ionospheric mapping of the tail fast flow channels. We focus on identifying such ionospheric signatures and understanding the physics of this magnetosphere-ionosphere interaction via conjunctions of the THEMIS probes with the Sondrestrom radar. From a number of such conjunctions we find that the onset of a substorm that is soon followed by a PBI has a very distinct signature in the radar data. At onset and expansion the ionospheric flow turns strictly westward. During the PBI, tail fast flows originate in the mid-tail and ionospheric flows turn equatorward. The generality and physical implications of this pattern are explored.

Zesta, E.; Lyons, L.; Angelopoulos, V.; Donovan, E.; McFadden, J.; Carlson, C.; Glassmeier, K.; Mende, S.

2008-12-01

201

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

Microsoft Academic Search

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

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

1988-01-01

202

An investigation of mechanisms other than lightning to explain certain wideband plasma wave bursts detected in the Venusian nightside ionosphere  

NASA Technical Reports Server (NTRS)

Several related topics are briefly discussed. Reviewed here is work on an investigation of plasma wave phenomena associated with the question of lightning on Venus. The work supported the contention that lightning is at least a candidate explanation for many of the 100 Hz-only Pioneer Venus orbital electric field detector (OEFD) signals. A review of the work on the investigation of mechanisms other than lightning to explain certain wideband plasma wave bursts detected in the Venusian nightside ionosphere is given. A summary is given of our analysis of data from 23 OEFD observing periods as well as a discussion of the properties of specifically multifrequency events. Our opportunity to work on this topic was not sufficient to draw any firm conclusions about the origins of the multifrequency bursts, but we call attention to what we consider to be several candidate sources. Also discussed are case studies to test for evidence of whistler mode propagation from subionospheric sources, results of a search for dispersive effects in the OEFD data, the results for a search for simultaneous 100 Hz and 730 Hz observations at altitudes below 150 km, changes with altitude in dispersive broadening effects in the time signatures of 100 Hz bursts, and a survey of activity at altitudes above 1000 km.

Carpenter, D. L.

1992-01-01

203

Chemical depletion of the ionosphere  

NASA Technical Reports Server (NTRS)

A theoretical study of the chemical and gas dynamical processes resulting from the release of reactive gases into the daytime ionosphere is discussed. Only point releases, such as from an explosion or a pulsed jet, are considered. Some scientific uses of the artificial reduction of the ionospheric plasma are considered.

Bernhardt, P. A.; Darosa, A. V.; Park, C. G.

1977-01-01

204

Ionospheres of the terrestrial planets  

Microsoft Academic Search

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

R. W. Schunk; A. F. Nagy

1980-01-01

205

On the possibility of inducing strong plasma convection in the divertor of MAST  

NASA Astrophysics Data System (ADS)

In this paper, a theory is developed to describe scrape-off layer (SOL) broadening by inducing convective cells through divertor plate biasing in a tokamak. The theory is applied to the Mega-Ampere Spherical Tokamak, where such experiments are planned in the near future. Criteria are derived for achieving strong broadening and for exciting shear-flow turbulence in the SOL, and 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 in the SOL by the biasing and the associated heating power are also calculated and are found to be modest.

Ryutov, D. D.; Helander, P.; Cohen, R. H.

2001-10-01

206

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

SciTech Connect

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.

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

2001-09-05

207

Tail and Ionospheric Signatures of Tail Fast Flows Associated with PBIs and with Substorms  

NASA Astrophysics Data System (ADS)

Earthward convection of the tail plasma sheet is often organized in bursts of fast ion flows restricted in azimuthally narrow channels. It has been shown that Auroral Poleward Boundary Intensifications (PBIs) are often the ionospheric signature of such fast flow channels in the midtail. Equatorward flow bursts have been observed in the ionosphere, and have been shown to be the ionospheric mapping of the tail fast flow channels in few case studies. We focus on identifying such ionospheric signatures and understanding the physics of this magnetosphere-ionosphere interaction via conjunctions of the THEMIS probes with the Sondrestrom radar. We find fundamental differences between the tail fast flows that are associated with substorm onsets and those associated with PBIs, as well as between their respective ionospheric flow signatures. The tail fast flows that produce PBIs are observed in the midtail. They do not typically penetrate to the inner magnetosphere and they are accompanied by plasma sheet expansion signatures in the mid tail. No dipolarization signatures are observed in the inner magnetosphere. The ionospheric signatures associated with such tail flows are PBI- type aurora and substantially enhanced equatorward flows. Tail fast flows that are associated with substorm onsets are typically observed only by the inner magnetosphere probes, only occasionally being seen also in the midtail. Clear dipolarizations are seen with such flows in the inner magnetosphere but not in the midtail. The ionospheric flow associated with such tail fast flows is far distinct, enhanced westward flows being occasionally seen at the higher latitude part of the Sondrestrom field of view with enhanced eastward flows observed at the lower latitudes. Enhanced equatorward flows are not seen.

Shi, Y.; Zesta, E.; Lyons, L.; Angelopoulos, V.; Donovan, E.; McFadden, J.; Carlson, C.; Glassmeier, K.; Mende, S.

2009-05-01

208

A theoretical study of the ionosphere over Zhongshan Station, Antarctica  

Microsoft Academic Search

A three-dimensional, time-dependent model for the polar ionosphere has been developed. The simulation results are applied to the interpretation of the ionospheric F region over Zhongshan Station. The daily variation is obtained for the high-latitude global polar ionosphere NmF2, mainly taking into account the interaction between the solar EUV ionization and the ionospheric convection processes in the polar region. It

B. Zhang; R. Liu; H. Yang; Z. Chen

2005-01-01

209

Low Latitude Ionospheric Zonal Plasma Drifts Measured by C/NOFS During the 2008-2011 Solar Minimum  

NASA Astrophysics Data System (ADS)

We use the measurements by Vector Electric Field Instrument (VEFI) on board the C/NOFS satellite to study seasonal, longitudinal, and latitudinal dependence of low latitude ionospheric zonal plasma drifts during 2008-2011. Over Jicamarca, these measurements are in good agreement with incoherent scatter radar F-region zonal drifts. Our data show strong longitudinal variations on both the daytime westward and nighttime eastward drifts at all seasons, particularly in the South American sector during the solstices. The daytime data indicate the occurrence of largely enhanced and short-lived westward drifts near sunrise, and strong longitude dependent peaks close to noon that resemble those observed on the equatorial vertical drift data. The nighttime eastward drifts have largest values near the western American sector at all seasons. Near midnight during June solstice, there is a sharp decrease in the magnitude of the eastward drifts at about 45 west and much smaller values in the entire eastern hemisphere. We also compare the satellite nighttime drifts with zonal winds and equatorial bubble drift velocities.

Fejer, B. G.; Tracy, B. D.; Pfaff, R. F.

2012-12-01

210

Adiabatic Betatron deceleration of ionospheric charged particles: a new explanation for (i) the rapid outflow of ionospheric O ions, and for (ii) the increase of plasma mass density observed in magnetospheric flux tubes during main phases of geomagnetic s  

NASA Astrophysics Data System (ADS)

Using European arrays of magnetometers and the cross-phase analysis to determine magnetic field line resonance frequencies, it has been found by Kale et al. (2009) that the plasma mass density within plasmaspheric flux tubes increased rapidly after the SSC of the Hallowe'en 2003 geomagnetic storms. These observations tend to confirm other independent experimental results, suggesting that heavy ion up-flow from the ionosphere is responsible for the observed plasma density increases during main phases of geomagnetic storms. The aim of our contribution is to point out that, during main phases, reversible Betatron effect induced by the increase of the southward Dst-magnetic field component (|? Bz|), diminishes slightly the perpendicular kinetic energy (W?) of charged particles spiraling along field lines. Furthermore, due to the conservation of the first adiabatic invariant (? = Wm/ Bm) the mirror points of all ionospheric ions and electrons are lifted up to higher altitudes i.e. where the mirror point magnetic field (Bm) is slightly smaller. Note that the change of the mirror point altitude is given by: ? hm = -1/3 (RE + hm) ? Bm / Bm. It is independent of the ion species and it does not depend of their kinetic energy. The change of kinetic energy is determined by: ? Wm = Wm ? Bm / Bm. Both of these equations have been verified numerically by Lemaire et al. (2005; doi: 10.1016/S0273-1177(03)00099-1) using trajectory calculations in a simple time-dependant B-field model: i.e. the Earth's magnetic dipole, plus an increasing southward B-field component: i.e. the Dst magnetic field whose intensity becomes more and more negative during the main phase of magnetic storms. They showed that a variation of Bz (or Dst) by more than - 50 nT significantly increases the mirror point altitudes by more than 100 km which is about equal to scale height of the plasma density in the topside ionosphere where particles are almost collisionless (see Fig. 2 in Lemaire et al., 2005). From these theoretical results we infer that all ionospheric electrons and ions species (including the O+ ions) experience an outward flow along geomagnetic field lines whose angle of dip is not too large. Since above 500 km altitude the various ions densities decrease almost exponentially with altitude with characteristic scale heights (Hions) of the order of 100 km or less, the main phase uplift of all mirror points increases the local mass density all along these field lines. This changes the plasmaspheric concentrations of the O+ ions as well as of others heavy ions in the topside ionosphere and plasmasphere. We will outline experimental tests to check this new hypothesis and physical mechanism to enhance the plasma mass density during the main phases of geomagnetic storms. A subsequent decrease of the plasma ion mass density is expected following the geomagnetic storm event, due to inverse Betatron effect during the recovery phase, and due to the effect of gravity pulling the heavier ions back to lower altitudes.

Lemaire, Joseph; Pierrard, Viviane; Darrouzet, Fabien

2013-04-01

211

GEOPHYSICAL RESEARCH LETTERS, VOL. 30(21), 2109, DOI:10.1029/2003GL017668, 2003 Direct measurements of the ionospheric convection variability  

E-print Network

the variable IMF. Based on these observations it is expected that increased Joule heating due to variability Joule heating occurs in the convection throat. 1. Introduction Variability of the convection electric Joule heating rates in the upper atmo- sphere. General circulation models (GCM) of the thermo- sphere

Shepherd, Simon

212

Heater Beam Angle Effect on Simulated Brillouin Scatter in Magnetized Ionospheric Plasma  

NASA Astrophysics Data System (ADS)

High power electromagnetic waves transmitted from HAARP have recently been shown to excite low frequency electrostatic waves by magnetized stimulated Brillouin scatter MSBS near the reflection or upper hybrid resonance regions. The pump wave may excite either electrostatic ion acoustic wave (IA) or electrostatic ion cyclotron wave (EIC) waves. Whether IA and EIC waves are excited depends on the wave propagation relative to the ambient magnetic field. It had been confirmed that only ion acoustic waves are observed for propagation near magnetic zenith while EIC waves can only be observed with more oblique propagation angles. The original discovery of EIC waves excited by the MSBS process considered only a narrow range of heater beam angles. The EIC wave strength in the spectrum was observed to be highly variable and proposed to possibly be near threshold. Also observations of the upshifted EIC waves in the spectrum were almost nonexistent. This was true for cascading of the downshifted EIC lines as well. Those EIC spectrum lines can provide valuable diagnostics for ion composition. This experiment conducted at the 2010 HAARP Summer School aims to look more thoroughly at a broader range of heater beam angle effects on IA and EIC waves generated by MSBS in the F layer ionosphere. The expected results show that the stronger IA and EIC spectrum lines were observed by the O-mode excitation. With increasing tilting angles, there exists a critical heater power beam angle above that EIC modes appear in the lower SEE spectrum. The power spectrum of EIC is more sensitively affected by the power beam angle than the IA spectrum lines. The experiments also aim to observe the second EIC (or even higher) frequency downshifted harmonics generated with increasing tilting angle.

Fu, H.; Bernhardt, P. A.; Scales, W. A.; Briczinski, S. J.; San Antonio, G.; Selcher, C. A.

2010-12-01

213

Early-time plasma expansion characteristics of ionized clouds in the ionosphere  

NASA Technical Reports Server (NTRS)

A series of Vlasov-Poisson simulations were conducted with barium and lithium gas mixtures expanding into an O(+) background plasma, with the values for the Ba(+)/Li(+) composition ratios and the cloud/background density ratios based on anticipated release values in the upcoming Combined Release and Radiation Effects Satellite (CRRES) experiment. The results obtained on the early-time expansion of high-density Ba(+), Li(+), and Ba(+)-Li(+) plasma clouds into low-density O(+) background plasma complement the H(+)-O(+) expansions of Gurevich et al. (1973) and Singh and Schunk (1982, 1983), and the characteristic features observed apply to the very-early-time expansion phase of the CRRES releases.

Schunk, R. W.; Szuszczewicz, E. P.

1988-01-01

214

Characterizing ISS Charging Environments with On-Board Ionospheric Plasma Measurements  

NASA Technical Reports Server (NTRS)

Charging of the International Space Station (ISS) is dominated by interactions of the biased United States (US) 160 volt solar arrays with the relatively high density, low temperature plasma environment in low Earth orbit. Conducting surfaces on the vehicle structure charge negative relative to the ambient plasma environment because ISS structure is grounded to the negative end of the US solar arrays. Transient charging peaks reaching potentials of some tens of volts negative controlled by photovoltaic array current collection typically occur at orbital sunrise and sunset as well as near orbital noon. In addition, surface potentials across the vehicle structure vary due to an induced v x B (dot) L voltage generated by the high speed motion of the conducting structure across the Earth's magnetic field. Induced voltages in low Earth orbit are typically only approx.0.4 volts/meter but the approx.100 meter scale dimensions of the ISS yield maximum induced potential variations ofapprox.40 volts across the vehicle. Induced voltages are variable due to the orientation of the vehicle structure and orbital velocity vector with respect to the orientation of the Earth's magnetic field along the ISS orbit. In order to address the need to better understand the ISS spacecraft potential and plasma environments, NASA funded development and construction of the Floating Potential Measurement Unit (FPMU) which was deployed on an ISS starboard truss arm in August 2006. The suite of FPMU instruments includes two Langmuir probes, a plasma impedance probe, and a potential probe for use in in-situ monitoring of electron temperatures and densities and the vehicle potential relative to the plasma environment. This presentation will describe the use of the FPMU to better characterize interactions of the ISS with the space environment, changes in ISS charging as the vehicle configuration is modified during ISS construction, and contributions of FPMU vehicle potential and plasma environment measurements to investigations of on-orbit anomalies in ISS systems.

Minow, Jospeh I.; Craven, Paul D.; Coffey, Victoria N.; Schneider, Todd A.; Vaughn, Jason A.; Wright Jr, Kenneth; Parker, Paul D.; Mikatarian, Ronald R.; Kramer, Leonard; Hartman, William A.; Alred, John W.; Koontz, Steven L.

2008-01-01

215

Towards the dispersion relation for ionacoustic instabilities in weakly inhomogeneous ionospheric plasma at altitudes 80-200km and its low-frequency solution  

E-print Network

In the paper within the approximation of the two-fluid magnetohydrodynamics and geometrooptical approximation the dispersion relation was found for ionacoustic instabilities of the ionospheric plasma at 80-200km altitudes in three-dimensional weakly irregular ionosphere. Low freqeuncy solution was found. The difference between obtained and standard solution becomes significant at altitudes above 140 km. As the analysis shown in this case the solution grows with time. The conditions for existence of such solution are the presence of co-directed electron density gradients and electron drifts and perpendicularity of line-of-sight to the magnetic field. The necessary conditions regularly exist at the magnetic equator. Detailed analysis has shown that this solution corresponds to well-known 150km equatorial echo and explains some of its statistical characteristics observed experimentally.

Berngardt, Oleg I

2009-01-01

216

A study of the cleft region using synoptic ionospheric plasma data obtained by the polar orbiting satellites Aeros-B and Isis-2  

NASA Technical Reports Server (NTRS)

The concentrations of O(+) and NO(+) in the dayside high-latitude cleft region of the ionosphere are investigated based on synoptic particle and plasma measurements obtained by the polar orbiting Aeros-B and Isis-2 satellites. At a time when the orbital planes of the satellites are almost at right angles to each other, three maxima in ion temperature are observed, with two of them accompanied by an increased electron temperature and electron density irregularities, and the density of the molecular ions NO(+) and O2(+) is found to increase at the expense of O(+) density. Results are discussed in terms of a theory relating perpendicular electric fields to oxygen atom reaction rates. Systematic analysis of the Aeros data base reveals 14 additional instances of O(+) to NO(+) conversion, with a large variety of forms and structures reflecting the complex structure and dynamics of the high-latitude dayside ionosphere.

Kist, R.; Klumpar, D.

1980-01-01

217

Ion-neutral momentum coupling near discrete high-latitude ionospheric features  

NASA Technical Reports Server (NTRS)

A two-dimensional numerical model is developed to study the momentum coupling between the ionosphere and neutral atmosphere in the vicinity of discrete high-latitude features, such as convection channels and plasma density troughs. Based on generalized magnetohydrodynamic equations the model takes account of global pressure gradients, viscous dissipation, ion drag, the Coriolis force, and electrodynamic drifts. Among the findings of an initial steady state investigation are the following: (1) in convection channels, significant shears and rotations of the thermospheric flow can occur below 200 km if a minimum in the electron density profile is present between the E and F regions; (2) in convection channels, the thermospheric wind decreases with height in the F region owing to the effects of horizontal viscosity; and (3) at low altitudes, the boundaries of convection channels may produce Ekman spirals.

St-Maurice, J.-P.; Schunk, R. W.

1981-01-01

218

Soviet ionospheric modification research  

Microsoft Academic Search

Soviet published literature in ionospheric modification research by high-power radio waves is assessed, including an evaluation of its impact on and applications to future remote-sensing and telecommunications systems. This assessment is organized to place equal emphasis on basic research activities, designed to investigate both the natural geophysical environment and fundamental plasma physics; advanced research programs, such as those studying artificial

L. M. Duncan; H. C. Carlson; F. T. Djuth; J. A. Fejer; N. C. Gerson; T. Hagfors; D. B. Newman Jr.; R. L. Showen

1988-01-01

219

Real-Time Ionospheric Plasma Density Estimates in the Polar Cap using Simultaneous Dual Frequency Doppler Measurements at the SuperDARN McMurdo Radar  

NASA Astrophysics Data System (ADS)

SuperDARN radars estimate plasma drift velocities from the Doppler shift observed on signals scattered from field-aligned density irregularities. The radars operate in the range of 8 MHz to 20 MHz and have ray paths covering a wide range of elevation angles, in order to maximize the range over which the scattering conditions are satisfied. Upward-propagating electromagnetic signals in this frequency range can be significantly refracted by the ionospheric plasma. The propagation paths of the refracted signals are bent earthward and at some point along this refracted path propagate perpendicular to the local magnetic field and scatter on the field-aligned density irregularities. The refraction results from gradients of the index of refraction in the ionospheric plasma. The index inside the ionosphere is lower than its free-space value, which depresses the measured line of sight velocity relative to the actual velocity of the plasma. One way to account for the depression of the measured velocity is to estimate the index of refraction in the scattering region by making multiple velocities measurements at different operating frequencies. Together with the appropriate plasma dispersion relations, multiple frequency measurements can be used to construct relations for the index of refraction, plasma density and the line of sight velocity correction factor as functions of frequency weighted measured velocity differences. Recent studies have used frequency-switching events spanning many days during traditional SuperDARN radar operation to build a statistical estimate for index of refraction, which is insensitive to the real-time spatial dynamics of the ionosphere. This statistical approach has motivated the development of a new mode of radar operation that provides simultaneous dual frequency measurements in order to resolve the temporal and spatial dynamics of the index of refraction calculations. Newly-developed multi-channel capabilities available in the SuperDARN radar control software now allow simultaneous dual frequency measurements at the McMurdo radar. This simultaneous dual frequency capability makes it possible, for the first time, to calculate real-time spatially resolved index of refraction and velocity correction factors across the radar field of view. Selected findings from the first several months of simultaneous dual frequency operation at the McMurdo SuperDARN radar will be presented.

Spaleta, J.; Bristow, W. A.

2012-12-01

220

Hybrid Description of Outflowing Ionospheric Plasma: A Monte Carlo\\/n-Moment Transport Equations Model  

Microsoft Academic Search

At terrestrial high latitudes, the plasma flows along ``open'' field lines, gradually going from a collision-dominated region into a collisionless region. Over several decades, the (fluid-like) generalized transport equations, TE, and the particle-based Monte Carlo, MC, approaches evolved as two of the most powerful simulation techniques that address this problem. In contrast to the computationally intensive Monte Carlo, the transport

J. Ji; A. R. Barakat; R. W. Schunk

2009-01-01

221

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)

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.

Parrot, M.

2010-12-01

222

Radar Soundings of the Ionosphere of Mars  

NASA Astrophysics Data System (ADS)

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.

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.

2005-12-01

223

Ionospheric Erosion by Alfven Waves  

NASA Astrophysics Data System (ADS)

Using observations from the FAST small explorer spacecraft we present fields and plasma observations above the dayside auroral oval showing the erosion of ionospheric plasmas from the topside ionosphere by the action of Alfven waves. Using interferometric techniques the waves are shown to approximately obey the expected dispersion for Alfven waves with transverse scales extending from greater than electron inertial lengths down to ion gyro-radii. Measurements of the plasma density where these waves are observed show that over latitudinal widths exceeding 100 km total depletion of the cold ionospheric plasma can occur. The plasma within these depleted regions or cavities is composed of magnetosheath ion and electron distributions and upgoing transversely accelerated ions and downgoing field-aligned electrons distributed as conics and field-aligned beams respectively. Poynting flux observations on the density gradients comprising the cavity walls show that these waves are directed downwards and focused inwards towards regions of lower density. The wave phase velocity measurement in the plasma frame, while subject to significant uncertainty, is directed transversely outwards from the cavity. These observations suggest a feedback model for Alfven wave focusing and ion heating on density gradients that can lead to intense ion outflow from the ionosphere and subsequent depletion of ionospheric plasmas.

Chaston, C. C.; Genot, V.; Bonnell, J. W.; Carlson, C.; McFadden, J.; Ergun, R.; Strangeway, R.; Lund, E.; Hwang, K.

2005-12-01

224

Nonlinearly generated plasma waves as a model for enhanced ion acoustic lines in the ionosphere  

NASA Astrophysics Data System (ADS)

Observations from the EISCAT Svalbard Radar, for instance, demonstrate that the symmetry of the naturally occurring ion line can be broken by an enhanced, non-thermal, level of fluctuations, i.e., Naturally Enhanced Ion-Acoustic Lines (NEIALs). In a significant number of cases, the entire ion spectrum can be distorted, with the appearance of a third line, corresponding to a propagation velocity significantly below the ion acoustic sound speed. By numerical simulations, we consider one possible model accounting for the observations, suggesting that a primary process can be electron acoustic waves excited by a cold electron beam. Subsequently, an oscillating two-stream instability excites electron plasma waves which in turn decay to asymmetric ion lines. Our code solves the full Vlasov equation for electrons and ions, with the dynamics coupled through the electrostatic field derived from Poisson's equation.

Daldorff, L. K. S.; Pécseli, H. L.; Trulsen, J.

2007-09-01

225

Attribution of ionospheric vertical plasma drift perturbations to large-scale waves and the dependence on solar activity  

NASA Astrophysics Data System (ADS)

In this study, we quantify the contribution of individual large-scale waves to ionospheric electrodynamics and examine the dependence of the ionospheric perturbations on solar activity. We focus on migrating diurnal tide (DW1) plus mean winds, migrating semidiurnal tide (SW2), quasi-stationary planetary wave one (QSPW1), and nonmigrating semidiurnal westward wave one (SW1) under northern winter conditions, when QSPW1 and SW1 are climatologically strong. From thermosphere-ionosphere-mesosphere electrodynamics general circulation model simulations under solar minimum conditions, it is found that the mean winds and DW1 produce a wave two pattern in equatorial vertical E×Bdrift that is upward in the morning and around dusk. The modeled SW2 also produces a wave two pattern in the ionospheric vertical drift that is nearly a half wave cycle out of phase with that due to mean winds and DW1. SW1 can cause large vertical drifts around dawn, while QSPW1 does not have any direct impact on the vertical drift. Wind components of both SW2 and SW1 become large at middle to high latitudes in the E-region, and kernel functions obtained from numerical experiments reveal that they can significantly affect the equatorial ion drift, likely through modulating the E-region wind dynamo. The most evident changes of total ionospheric vertical drift when solar activity is increased are seen around dawn and dusk, reflecting the more dominant role of large F-region Pedersen conductivity and of the F-region dynamo under high solar activity. Therefore, the lower atmosphere driving of the ionospheric variability is more evident under solar minimum conditions, not only because variability is more identifiable in a quieter background but also because the E-region wind dynamo is more significant. These numerical experiments also demonstrate that the amplitudes, phases, and latitudinal and vertical structures of large-scale waves are important in quantifying the ionospheric responses.

Liu, H.-L.; Richmond, A. D.

2013-05-01

226

Tsunamigenic ionospheric hole  

NASA Astrophysics Data System (ADS)

Traveling ionospheric disturbances generated by an epicentral ground/sea surface motion, ionospheric disturbances associated with Rayleigh-waves as well as post-seismic 4-minute monoperiodic atmospheric resonances and other-period atmospheric oscillations have been observed in large earthquakes. In addition, a giant tsunami after the subduction earthquake produces an ionospheric hole which is widely a sudden depletion of ionospheric total electron content (TEC) in the hundred kilometer scale and lasts for a few tens of minutes over the tsunami source area. The tsunamigenic ionospheric hole detected by the TEC measurement with Global Position System (GPS) was found in the 2011 M9.0 off the Pacific coast of Tohoku, the 2010 M8.8 Chile, and the 2004 M9.1 Sumatra earthquakes. This occurs because plasma is descending at the lower thermosphere where the recombination of ions and electrons is high through the meter-scale downwelling of sea surface at the tsunami source area, and is highly depleted due to the chemical processes.

Kakinami, Yoshihiro; Kamogawa, Masashi; Tanioka, Yuichiro; Watanabe, Shigeto; Riadi Gusman, Aditya; Liu, Jann-Yenq; Watanabe, Yasuyuki; Mogi, Toru

227

Tsunamigenic ionospheric hole  

NASA Astrophysics Data System (ADS)

Traveling ionospheric disturbances generated by an epicentral ground/sea surface motion, ionospheric disturbances associated with Rayleigh-waves as well as post-seismic 4-minute monoperiodic atmospheric resonances and other-period atmospheric oscillations have been observed in large earthquakes. In addition, a giant tsunami after the subduction earthquake produces an ionospheric hole which is widely a sudden depletion of ionospheric total electron content (TEC) in the hundred kilometer scale and lasts for a few tens of minutes over the tsunami source area. The tsunamigenic ionospheric hole detected by the TEC measurement with Global Position System (GPS) was found in the 2011 M9.0 off the Pacific coast of Tohoku, the 2010 M8.8 Chile, and the 2004 M9.1 Sumatra earthquakes. This occurs because plasma is descending at the lower thermosphere where the recombination of ions and electrons is high through the meter-scale downwelling of sea surface at the tsunami source area, and is highly depleted due to the chemical processes.

Kakinami, Yoshihiro; Kamogawa, Masashi; Tanioka, Yuichiro; Watanabe, Shigeto; Gusman, Aditya Riadi; Liu, Jann-Yenq; Watanabe, Yasuyuki; Mogi, Toru

2012-06-01

228

A Dynamic Coupled Magnetosphere-Ionosphere-Ring Current Model  

NASA Astrophysics Data System (ADS)

In this thesis we describe a coupled model of Earth's magnetosphere that consists of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) simulation, the MIX ionosphere solver and the Rice Convection Model (RCM). We report some results of the coupled model using idealized inputs and model parameters. The algorithmic and physical components of the model are described, including the transfer of magnetic field information and plasma boundary conditions to the RCM and the return of ring current plasma properties to the LFM. Crucial aspects of the coupling include the restriction of RCM to regions where field-line averaged plasma-beta ¡=1, the use of a plasmasphere model, and the MIX ionosphere model. Compared to stand-alone MHD, the coupled model produces a substantial increase in ring current pressure and reduction of the magnetic field near the Earth. In the ionosphere, stronger region-1 and region-2 Birkeland currents are seen in the coupled model but with no significant change in the cross polar cap potential drop, while the region-2 currents shielded the low-latitude convection potential. In addition, oscillations in the magnetic field are produced at geosynchronous orbit with the coupled code. The diagnostics of entropy and mass content indicate that these oscillations are associated with low-entropy flow channels moving in from the tail and may be related to bursty bulk flows and bubbles seen in observations. As with most complex numerical models, there is the ongoing challenge of untangling numerical artifacts and physics, and we find that while there is still much room for improvement, the results presented here are encouraging. Finally, we introduce several new methods for magnetospheric visualization and analysis, including a fluid-spatial volume for RCM and a field-aligned analysis mesh for the LFM. The latter allows us to construct novel visualizations of flux tubes, drift surfaces, topological boundaries, and bursty-bulk flows.

Pembroke, Asher

229

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

Microsoft Academic Search

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

J. M. Ruohoniemi; R. A. Greenwald

1996-01-01

230

Global equatorial ionospheric vertical plasma drifts measured by the AE-E satellite  

NASA Technical Reports Server (NTRS)

Ion drift meter observations from the Atmosphere Explorer E (AE-E) satellite during the period of January 1977 to December 1979 are used to study the dependence of equatorial (dip latitudes less than or equal to 7.5 deg) F region vertical plasma drifts (east-west electric fields) on solar activity, season, and longitude. The satellite-observed ion drifts show large day-to-day and seasonal variations. Solar cycle effects are most pronounced near the dusk sector with a large increase of the prereversal velocity enhancement from solar minimum to maximum. The diuurnal, seasonal, and solar cycle dependence of the logitudinally averaged drifts are consistent with results from the Jicamarca radar except near the June solstice when the AE-E nighttime downward velocities are significantly smaller than those observed by the radar. Pronounced presunrise downward drift enhancements are often observed over a large longituudinal range but not in the Peruvian equatorial region. The satellite data indicate that longitudinal variations are largest near the June solstice, particularly near dawn and dusk but are virtually absent during equinox. The longitudinal dependence of the AE-E vertical drifts is consistent with results from ionosonde data. These measurements were also used to develop a description of equatorial F region vertical drifts in four longitudinal sectors.

Fejer, B. G.; De Paula, E. R.; Heelis, R. A.; Hanson, W. B.

1995-01-01

231

High Power HF Excitation of Low Frequency Stimulated Electrostatic Waves in the Ionospheric Plasma over HAARP  

NASA Astrophysics Data System (ADS)

High Power electromagnetic (EM) waves transmitted from the HAARP facility in Alaska can excite low frequency electrostatic waves by several processes including (1) direct magnetized stimulated Brillouin scatter (MSBS) and (2) parametric decay of high frequency electrostatic waves into electron and ion Bernstein waves. Either an ion acoustic (IA) wave with a frequency less than the ion cyclotron frequency (fCI) or an electrostatic ion cyclotron (EIC) wave just above fCI can be produced by MSBS. The coupled equations describing the MSBS instabil-ity show that the production of both IA and EIC waves is strongly influenced by the wave propagation direction relative to the background magnetic field. Experimental observations of stimulated electromagnetic emissions (SEE) using the HAARP transmitter in Alaska have confirmed the theoretical predictions that only IA waves are excited for propagation along the magnetic zenith and that EIC waves can only be detected with oblique propagation angles. The electron temperature in the heated plasma is obtained from the IA spectrum offsets from the pump frequency. The ion composition can be determined from the measured EIC frequency. Near the second harmonic of the electron cyclotron frequency, the EM pump wave is converted into an electron Bernstein (EB) wave that decays into another EB wave and an ion Bernstein (IB) wave. Strong cyclotron resonance with the EB wave leads to acceleration of the electrons. Ground based SEE observations are related to the theory of low-frequency electrostatic wave generation.

Bernhardt, Paul; Selcher, Craig A.

232

Global characteristics of ionospheric electric fields and disturbances during the first hours of magnetic storms  

Microsoft Academic Search

The ionospheric plasma density can be significantly disturbed during magnetic storms. In the conventional scenario of ionospheric storms, the negative storm phases with plasma density decreases are caused by neutral composition changes, and the positive storm phases with plasma density increases are often related to atmospheric gravity waves. However, recent studies show that the global redistribution of the ionospheric plasma

Chao-Song Huang

2008-01-01

233

Ionospheric research  

NASA Technical Reports Server (NTRS)

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.

1975-01-01

234

Ionosphere research  

NASA Technical Reports Server (NTRS)

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.

1976-01-01

235

Persistent Longitudinal Variations of Plasma Density and DC Electric Fields in the Low Latitude Ionosphere Observed with Probes on the C/NOFS Satellite  

NASA Technical Reports Server (NTRS)

Continuous measurements using in situ probes on consecutive orbits of the C/N0FS satellite reveal that the plasma density is persistently organized by longitude, in both day and night conditions and at all locations within the satellite orbit, defined by its perigee and apogee of 401 km and 867 km, respectively, and its inclination of 13 degrees. Typical variations are a factor of 2 or 3 compared to mean values. Furthermore, simultaneous observations of DC electric fields and their associated E x B drifts in the low latitude ionosphere also reveal that their amplitudes are also strongly organized by longitude in a similar fashion. The drift variations with longitude are particularly pronounced in the meridional component perpendicular to the magnetic field although they are also present in the zonal component as well. The longitudes of the peak meridional drift and density values are significantly out of phase with respect to each other. Time constants for the plasma accumulation at higher altitudes with respect to the vertical drift velocity must be taken into account in order to properly interpret the detailed comparisons of the phase relationship of the plasma density and plasma velocity variations. Although for a given period corresponding to that of several days, typically one longitude region dominates the structuring of the plasma density and plasma drift data, there is also evidence for variations organized about multiple longitudes at the same time. Statistical averages will be shown that suggest a tidal "wave 4" structuring is present in both the plasma drift and plasma density data. We interpret the apparent association of the modulation of the E x B drifts with longitude as well as that of the ambient plasma density as a manifestation of tidal forces at work in the low latitude upper atmosphere. The observations demonstrate how the high duty cycle of the C/NOFS observations and its unique orbit expose fundamental processes at work in the low latitude, inner regions of geospace.

Pfaff, R.; Freudenreich, H.; Klenzing, J.; Rowland, D.; Liebrecht, C.; Bromund, K.; Roddy, P.

2010-01-01

236

Ionospheric signatures of Lightning  

NASA Astrophysics Data System (ADS)

The geostationary metrology satellite (GMS) monitors motions of thunderstorm cloud, while the lightning detection network (LDN) in Taiwan and the very high Frequency (VHF) radar in Chung-Li (25.0›XN, 121.2›XE) observed occurrences of lightning during May and July, 1997. Measurements from the digisonde portable sounder (DPS) at National Central University shows that lightning results in occurrence of the sporadic E-layer (Es), as well as increase and decrease of plasma density at the F2-peak and E-peak in the ionosphere, respectively. A network of ground-based GPS receivers is further used to monitor the spatial distribution of the ionospheric TEC. To explain the plasma density variations, a model is proposed.

Hsu, M.; Liu, J.

2003-12-01

237

Attribution of ionospheric vertical plasma drift perturbations to large-scale waves and the dependence on solar activity (Invited)  

NASA Astrophysics Data System (ADS)

In this study we quantify the contribution of individual large-scale waves to ionospheric electrodynamics, and examine the dependence of the ionospheric perturbations on solar activity. We focus on migrating diurnal tide (DW1) plus mean winds, migrating semidiurnal tide (SW2), quasi-stationary planetary wave 1 (QSPW1), and nonmigrating semidiurnal westward wave 1 (SW1) under northern winter conditions, when QSPW1 and SW1 are climatologically strong. From TIME-GCM simulations under solar minimum conditions, we calculate equatorial vertical ExB drifts due to mean winds and DW1, SW2, SW1 and QSPW1. In particular, wind components of both SW2 and SW1 become large at mid to high latitudes in the E-region, and kernel functions obtained from numerical experiments reveal that they can significantly affect the equatorial ion drift, likely through modulating the E-region wind dynamo. The most evident changes of total ionospheric vertical drift when solar activity is increased are seen around dawn and dusk, reflecting the more dominant role of large F-region Pedersen conductivity and of the F-region dynamo under high solar activity. Therefore, the lower atmosphere driving of the ionospheric variability is more evident under solar minimum conditions, not only because variability is more identifiable in a quieter background, but also because the E-region wind dynamo is more significant. These numerical experiments also demonstrate that the amplitudes, phases and latitudinal and vertical structures of large-scale waves are important in quantifying the ionospheric responses.

Liu, H.; Richmond, A. D.

2013-12-01

238

Plasma structuring by the gradient drift instability at high latitudes and comparison with velocity shear driven processes  

NASA Technical Reports Server (NTRS)

Using results of the in situ measurements made by the DE 2 satellite, the nature of plasma structuring at high latitudes, caused by the gradient drift instability process, is described. Using noon-midnight and dawn-dusk orbits of the DE 2 satellite, it was possible to examine the simultaneous density and electric field spectra of convecting large-scale plasma density enhancements in the polar cap known as 'patches', in directions parallel and perpendicular to their antisunward convection. The results provide evidence for the existence of at least two generic classes of instabilities operating in the high-latitude ionosphere: one driven by large-scale density gradients in a homogeneous convection field with respect to the neutrals, and the other driven by the structured convection field itself in an ambient ionosphere where density fluctuations are ubiquitous.

Basu, Sunanda; Mackenzie, E.; Basu, S.; Coley, W. R.; Sharber, J. R.; Hoegy, W. R.

1990-01-01

239

Main ionospheric trough as a boundary layer in the ionosphere  

NASA Astrophysics Data System (ADS)

The mid-latitude electron density trough observed in the topside ionosphere has been shown to be the near-Earth signature of the plasmapause and can provide useful information about the magnetosphere-ionosphere dynamics and morphology. Thus for present the evolution of iono-spheric trough in time and space domain we need some multipoint measurements and different type of measurements techniques. To develop a quantitative model of evolution ionospheric trough features during geomagnetic disturbances the analyse of particle and waves in situ mea-surements and TEC data was carried out. The high resolutions plasma particle diagnostics and wave diagnostics located on board of currently operated satellite DEMETER can give us precisely description of trough signatures and instabilities at define point in space. In particular we will show the temperature and ion drifts manifestation inside ionospheric trough. On the other hand GPS permanent networks such as IGS and EPN provide regular monitoring of the ionosphere in a global scale. Furthermore radio occultation techniques is considered. The radio occultation technique using GPS signals has been proven to be a promising technique to retrieve accurate profiles of the ionospheric electron density with high vertical resolution on a global scale. FormoSat-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) is a joint scientific mission between Taiwan and the U.S.A. The mission placed six small micro-satellites into six different orbits at 700˜800 kilometer above the earth surface. The aim of this paper is to present some general behavior of trough dynamics as well as the fine structures of ionospheric trough and discuss the different type of instability generated inside the trough region from ULF frequency range thru VLF up to HF frequency range. In order to better understand the physical conditions and evolution of ionosphere trough region and describe the coupling between ionosphere and inner magnetosphere the detail examination of geomagnetic storm in January 2005 is presented. As a consequence of different time scales of physical processes occurred in the near Earth environment during geomagnetic disturbances and energy transfer between ionosphere and magnetosphere the examination of ion end electron fluxes inside ionosphere trough are disused.

Rothkaehl, Hanna; Krankowski, Andrzej; Liu, Yann-Yeng; Slominska, Ewa; Czajkowski, Tomasz

240

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)

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.

Horvath, Ildiko; Lovell, Brian C.

2008-12-01

241

Comparing F region ionospheric irregularity observations from C/NOFS and Jicamarca  

NASA Astrophysics Data System (ADS)

Observations of plasma density irregularities associated with equatorial spread F (ESF) have been made using the Jicamarca Radio Observatory and the Plasma Langmuir Probe (PLP) and Vector Electric Field Instrument (VEFI) instruments on the Communications Navigation Outage Forecast System (C/NOFS) satellite during a close spatio-temporal conjunction. The radar data resolution is of the order of 1 km and a few sec. in space and time, respectively. We find that coherent scatter intensifications at these scales are coincident and collocated with plasma density depletions as determined by C/NOFS. The Doppler shifts of the localized echoes are also comparable to the vertical components of the E × B plasma drifts. The strongest backscatter does not necessarily come from the deepest or most rapidly convecting depletions. This implies a complex relationship between coherent backscatter and the underlying state parameters in the ionospheric plasma.

Hysell, D. L.; Hedden, R. B.; Chau, J. L.; Galindo, F. R.; Roddy, P. A.; Pfaff, R. F.

2009-07-01

242

Ionospheric ions in the near-Earth magnetotail  

NASA Astrophysics Data System (ADS)

We report studies of the relationship between geomagnetic storms and the spatial distribution of cold ions, mostly of ionospheric origin, in the near-Earth magnetotail using in situ particle and field measurements from the Polar spacecraft, solar wind measurements from the ACE spacecraft, and ground geomagnetic indices, during the years from 2000 to 2005. We find local time and latitude-dependent distributions of the plasma moments of cold ions at various levels of geomagnetic storms characterized by the Sym-H and Dst indices. (1) Denser cold ions were observed at the duskside (N > 10 cm-3 compared with 1 cm-3 on average): consistent with the formation of plasma plumes and enhanced bulge region formed as the cold ions wrapped under corotation. (2) Higher temperatures were observed in the auroral oval regions, and a larger temperature anisotropy was observed at the dawnside. (3) Heating processes were strongest near midnight and in the auroral oval regions, which map to PSBL or CPS, except during extremely high geomagnetic activity levels, when heating occurred at high latitudes toward the dawnside, which map to the plasma mantle or distant magnetotail. We interpret these variations as results of ionospheric outflows and plasmaspheric expansion interacting with enhancements of near-Earth magnetospheric convection and geomagnetic-storm-related heating processes in the magnetotail.

Chen, Sheng-Hsien; Moore, Thomas E.

2008-08-01

243

Physical Processes for Driving Ionospheric Outflows in Global Simulations  

NASA Technical Reports Server (NTRS)

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.

Moore, Thomas Earle; Strangeway, Robert J.

2009-01-01

244

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

Microsoft Academic Search

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

V. M. Sorokin

2007-01-01

245

Kinetic and thermodynamic properties of a convecting plasma in a two-dimensional dipole field  

NASA Technical Reports Server (NTRS)

Charged particle guiding center motion is considered in the magnetic field of a two-dimensional ('line') dipole on which is superimposed a small, static, perpendicular electric field. The parallel equation of motion is that of a simple harmonic oscillator for cos theta, the cosine of magnetic colatitude theta. Equations for the perpendicular electric and magnetic drifts are derived as well as their bounce-averaged forms. The latter are solved to yield a bounce-averaged guiding center trajectory, which is the same as that obtained from conversation of magnetic moment mu, longitudinal invariant J, and total (kinetic plus electrostatic) energy K. The algebraic simplicity of the trajectory equations is also manifest in the forms of the invariants. An interesting result is that guiding centers drift in such a way that they preserve the values of their equatorial pitch angles and (equivalently) mirror latitudes. The most general Maxwellian form of the equilibrium one-particle distribution function f is constructed from the invariants, and spatially varying density and pressure moments, parallel and perpendicular to the magnetic field, are identified. Much of the paper deals with the more restricted problem in which f is specified as a bi-Maxwellian over a straight line of finite length in the equatorial plane of the dipole and perpendicular to field lines. This might be thought of as specifying a cross-tail ion injection source; our formalism then describes the subsequent spatial development. The distribution away from the source is a scaled bi-Maxwellian but one that is cut off at large and small kinetic energies, which depend on position. Density and pressure components are reduced from the values they would have if the total content of individual flux tubes convected intact. The equatorial and meridional variations of density and pressure components are examined and compared systematically for the isotropic and highly anisotropic situations. There appears to be little qualitative difference due to anisotropy. An anisotropy measure is defined, and its spatial variation determined as a signature of possible MHD instability. Extreme values are found, larger than at the source, but the plasma beta in such regions is probably so low as to render the effect inconsequential energetically. Finally, the possible consequence of 'nonadia- batic' pressure profiles on electrostatic interchanges is considered, and a boundary delineating stabilizing and destabilizing regions determined.

Huang, T. S.; Birmingham, T. J.

1994-01-01

246

Magnetosphere-Ionosphere coupling through the auroral acceleration region  

NASA Technical Reports Server (NTRS)

An important form of coupling between the magnetosphere and the ionosphere occurs through acceleration mechanisms operative in the high altitude ionosphere on magnetic field lines connecting to the auroral zone. Energetic ion mass spectrometer data from within these auroral acceleration regions are presented to illustrate the characteristics of the mechanisms. Observations of ionospheric plasmas in the ring current, the distant plasma sheet, and the magnetotail lobes are shown illustrating the extent of their circulation and the importance of their contribution to the plasma in each regime. Finally the precipitating plasmas in the auroral region and the extent and peculiar effects of the 0(+) component of that precipitation on the ionosphere are illustrated.

Sharp, R. D.; Shelley, E. G.

1981-01-01

247

Simultaneous conjugate observations of dynamic variations in high-latitude dayside convection due to changes in IMF B sub y  

SciTech Connect

Two conjugate HF radars are currently operating at Goose Bay, Labrador, and Halley Station, Antarctica, and are providing continuous, high temporal resolution measurements of plasma convection over large areas of the high-latitude ionosphere. In this paper, data from these radars for a single 45-min period about local noon on 22 April 1988 are examined to study near-instantaneous, conjugate, two-dimensional patterns of plasma convection in the vicinity of the cusp and their response to changes in the B{sub y} component of the interplanetary magnetic field (IMF). The observations indicate that under quasi-stationary IMF conditions, the conjugate convection patterns are quite similar to the synthesized patterns of Heppner and Maynard (1987). The patterns respond rapidly to changes in the IMF B{sub y} component. The average response time was 8 min between an IMF transition at the IMP-8 satellite and the beginning of a convection reconfiguration in the ionosphere. Typically, the newly reconfigured convection pattern filled the radar field of view (10{degree} to 15{degree} of invariant latitude and 2.5 h of local time) within 6 min of reconfiguration onset. For the examples studied the reconfiguration onsets began over an extended local time sector in the invariant latitude range from 73{degree} to 75{degree} and proceeded by means of a poleward expansion of the reconfigured pattern into a region containing fossil convection associated with the prior IMF state. The authors interpret the onset region in the ionosphere as being associated with cusp field lines and the poleward region as being associated with open field lines in the plasma mantle and tail lobe.

Greenwald, R.A.; Baker, K.B.; Ruohoniemi, J.M. (Johns Hopkins Univ., Laurel, MD (USA)); Dudeney, J.R.; Pinnock, M.; Mattin, N.; Leonard, J.M. (Natural Environment Research Council, Cambridge (England)); Lepping, R.P. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1990-06-01

248

Plasmapause Convects to the Magnetopause During Halloween Solar Storm  

NSDL National Science Digital Library

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.

Bridgman, Tom; Williams, James; Shirah, Greg; Goldstein, Jerald

2004-12-15

249

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

250

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

National Technical Information Service (NTIS)

This paper surveys theory issues associated with inducing convective cells through diverter 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 plan...

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

2001-01-01

251

Convection in Galaxy-Cluster Plasmas Driven by Active Galactic Nuclei and Cosmic-Ray This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Convection in Galaxy-Cluster Plasmas Driven by Active Galactic Nuclei and Cosmic-Ray Buoyancy This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2004 ApJ 616 IOPscience #12;CONVECTION IN GALAXY-CLUSTER PLASMAS DRIVEN BY ACTIVE GALACTIC NUCLEI AND COSMIC-RAY BUOYANCY

Chandran, Ben

252

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

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.

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

1989-02-01

253

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

Microsoft Academic Search

A number of events have been observed in the Los Alamos\\/Garching fast plasma experiment data from ISEE 2 within {plus minus} 3 hours of noon wherein the y component of the plasmas flow within the low latitude boundary layer and magnetopause current layer is oppositely directed to that in the adjacent magnetosheath. When the y component, B{sub y}, of the

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

1990-01-01

254

Ionospheric redistribution during geomagnetic storms  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

255

Direct measurements of plasma drift velocities at high magnetic latitudes.  

NASA Technical Reports Server (NTRS)

Description of an incoherent scatter radar experiment performed at the 23-cm radar facility in Chatanika, Alaska. The experiment has provided a direct method for measuring the ionospheric plasma transport velocity vector over long periods with relatively good time resolution. Since the F-region transport at this site is closely associated with magnetospheric convection, particularly at night, the radar can provide important information about the behavior of the magnetosphere.

Doupnik, J. R.; Banks, P. M.; Baron, M. J.; Rino, C. L.; Petriceks, J.

1972-01-01

256

Effect of an MLT dependent electron loss rate on the magnetosphere-ionosphere coupling  

NASA Astrophysics Data System (ADS)

As plasma sheet electrons drift earthward, they get scattered into the loss cone due to wave-particle interactions and the resulting precipitation produces auroral conductance. Realistic electron loss is thus important for modeling the magnetosphere - ionosphere (M-I) coupling and the degree of plasma sheet electron penetration into the inner magnetosphere. In order to evaluate the significance of electron loss, we used the Rice Convection Model (RCM) coupled with a force-balanced magnetic field to simulate plasma sheet transport under different electron loss rates and under self-consistent electric and magnetic field. We used different magnitudes of i) strong pitch angle diffusion everywhere electron loss rate (strong rate) and ii) a more realistic loss rate with its MLT dependence determined by wave activity (MLT rate). We found that electron pressure under the MLT rate is larger compared to the strong rate inside L ? 12 RE. The dawn-dusk asymmetry in the precipitating electron energy flux under the MLT rate, with much higher energy flux at dawn than at dusk, agrees better with statistical DMSP observations. High-energy electrons inside L ? 8 RE can remain there for many hours under the MLT rate, while those under the strong rate get lost within minutes. Under the MLT rate, the remaining electrons cause higher conductance at lower latitudes; thus after a convection enhancement, the shielding of the convection electric field is less efficient, and as a result, the ion plasma sheet penetrates further earthward into the inner magnetosphere than under the strong rate.

Gkioulidou, Matina; Wang, Chih-Ping; Wing, Simon; Lyons, Larry R.; Wolf, Richard A.; Hsu, Tung-Shin

2012-11-01

257

Ionospheric modification by rocket effluents. Final report  

SciTech Connect

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.

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

1980-06-01

258

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

NASA Astrophysics Data System (ADS)

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.

Horvath, Ildiko; Lovell, Brian C.

2014-06-01

259

Computer study of convection of weakly ionized plasma in a nonuniform magnetic field.  

NASA Technical Reports Server (NTRS)

A weakly ionized plasma in a strong and nonuniform magnetic field exhibits an instability analogous to the flute instability in a fully ionized plasma. The instability sets in at a critical magnetic field. To study the final state of the plasma after the onset of the instability, the plasma equations are integrated numerically assuming a certain initial spectrum of small disturbances. In the regime studied, numerical results indicate a final steadily oscillating state consisting of a single finite amplitude mode together with a time-independent modification of the original equilibrium. These results agree with the analytic results obtained by Simon in the slightly supercritical regime. As the magnetic field is increased further, the wavelength of the final oscillation becomes nonunique. There exists a subinterval in the unstable wave band. Final stable oscillation with a wavelength in this subinterval can be established if the initial disturbance has a sufficiently strong component at the particular wavelength.

Shiau, J. N.

1972-01-01

260

A two-dimensional theory of plasma contactor clouds used in the ionosphere with an electrodynamic tether  

NASA Technical Reports Server (NTRS)

Plasma contactors have been proposed as a means of making good electrical contact between biased surfaces such as found at the ends of an electrodynamic tether and the space environment. A plasma contactor is a plasma source which emits a plasma cloud which facilitates the electrical connection. The physics of this plasma cloud is investigated for contactors used as electron collectors and it is shown that contactor clouds in space will consist of a spherical core possibly containing a shock wave. Outside of the core the cloud will expand anisotropically across the magnetic field leading to a turbulent cigar shape structure along the field. This outer region is itself divided into two regions by the ion response to the electric field. A two-dimensional theory of the motion of the cloud across the magnetic field is developed. The current voltage characteristic of an Argon plasma contactor cloud is estimated for several ion currents in the range of 1-100 Amperes. It is shown that small ion current contactors are more efficient than large ion current contactors. This suggests that if a plasma contactor is used on an electrodynamic tether then a miltiple tether array will be more efficient than a single tether.

Hastings, D. E.; Gatsonis, N. A.; Rivas, D. A.

1988-01-01

261

Earthquake-Ionosphere Coupling Processes  

NASA Astrophysics Data System (ADS)

After a giant earthquake (EQ), acoustic and gravity waves are excited by the displacement of land and sea surface, propagate through atmosphere, and then reach thermosphere, which causes ionospheric disturbances. This phenomenon was detected first by ionosonde and by HF Doppler sounderin the 1964 M9.2 Great Alaskan EQ. Developing Global Positioning System (GPS), seismogenic ionospheric disturbance detected by total electron content (TEC) measurement has been reported. A value of TEC is estimated by the phase difference between two different carrier frequencies through the propagation in the dispersive ionospheric plasma. The variation of TEC is mostly similar to that of F-region plasma. Acoustic-gravity waves triggered by an earthquake [Heki and Ping, EPSL, 2005; Liu et al., JGR, 2010] and a tsunami [Artu et al., GJI, 2005; Liu et al., JGR, 2006; Rolland, GRL, 2010] disturb the ionosphere and travel in the ionosphere. Besides the traveling ionospheric disturbances, ionospheric disturbances excited by Rayleigh waves [Ducic et al, GRL, 2003; Liu et al., GRL, 2006] as well as post-seismic 4-minute monoperiodic atmospheric resonances [Choosakul et al., JGR, 2009] have been observed after the large earthquakes. Since GPS Earth Observation Network System (GEONET) with more than 1200 GPS receiving points in Japan is a dense GPS network, seismogenic ionospheric disturbance is spatially observed. In particular, the seismogenic ionospheric disturbance caused by the M9.0 off the Pacific coast of Tohoku EQ (henceforth the Tohoku EQ) on 11 March 2011 was clearly observed. Approximately 9 minutes after the mainshock, acoustic waves which propagated radially emitted from the tsunami source area were observed through the TEC measurement (e. g., Liu et al. [JGR, 2011]). Moreover, there was a depression of TEC lasting for several tens of minutes after a huge earthquake, which was a large-scale phenomenon extending to a radius of a few hundred kilometers. This TEC depression may be an ionospheric phenomenon attributed to tsunami, termed tsunamigenic ionospheric hole (TIH) [Kakinami and Kamogwa et al., GRL, 2012]. After the TEC depression accompanying a monoperiodic variation with approximately 4-minute period as an acoustic resonance between the ionosphere and the solid earth, the TIH gradually recovered. In addition, geomagnetic pulsations with the periods of 150, 180 and 210 seconds were observed on the ground in Japan approximately 5 minutes after the mainshock. Since the variation with the period of 180 seconds was simultaneously detected at the magnetic conjugate of points of Japan, namely Australia, field aligned currents along the magnetic field line were excited. The field aligned currents might be excited due to E and F region dynamo current caused by acoustic waves originating from the tsunami. This result implies that a large earthquake generates seismogenic field aligned currents. Furthermore, monoperiodical geomagnetic oscillation pointing to the epicenter of which velocity corresponds to Rayleigh waves occurs. This may occur due to seismogenic arc-current in E region. Removing such magnetic oscillations from the observed data, clear tsunami dynamo effect was found. This result implies that a large EQ generates seismogenic field aligned currents, seismogenic arc-current and tsunami dynamo current which disturb geomagnetic field. Thus, we found the complex coupling process between a large EQ and an ionosphere from the results of Tohoku EQ.

Kamogawa, Masashi

262

Role of stochasticity in turbulence and convective intermittent transport at the scrape off layer of Ohmic plasma in QUEST  

NASA Astrophysics Data System (ADS)

Statistical features of fluctuations are investigated using the fast camera imaging technique in the scrape of layer (SOL) of electron cyclotron resonance heated Ohmic plasma. Fluctuations in the SOL towards low field side are dominated by coherent convective structures (blobs). Two dimensional structures of the higher order moments (skewness s and kurtosis k) representing the shape of probability density function (PDF) are studied. s and k are seen to be functions of the magnetic field lines. s and k are consistently higher towards the bottom half of the vessel in the SOL showing the blob trajectory along the field lines from the top towards bottom of the vessel. Parabolic relation ( k = A s 2 + C) is observed between s and k near the plasma boundary, featuring steep density gradient region and at the far SOL. The coefficient A, obtained experimentally, indicates a shift of prominence from pure drift-wave instabilities towards fully developed turbulence. Numerical coefficients characterizing the Pearson system are derived which demonstrates the progressive deviation of the PDF from Gaussian towards gamma from the density gradient region, towards the far SOL. Based on a simple stochastic differential equation, a direct correspondence between the multiplicative noise amplitude, increased intermittency, and hence change in PDF is discussed.

Banerjee, Santanu; Zushi, H.; Nishino, N.; Hanada, K.; Ishiguro, M.; Tashima, S.; Liu, H. Q.; Mishra, K.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A.; Nagashima, Y.; Matsuoka, K.

2014-07-01

263

Corotating magnetospheric convection  

Microsoft Academic Search

The longitudinal asymmetry of the Io plasma torus, as predicted by the magnetic-anomaly model and observed by Earth-based optical astronomy, provides a driving mechanism for a corotating convection system in Jupiter's magnetosphere. Here we deduce some qualitative properties of this convection system from the general equations that govern a steady state corotating convection system (although we expect that time-dependent effects

T. W. Hill; A. J. Dessler; L. J. Maher

1981-01-01

264

The Capability of Space Mission to Study the Ionosphere and Electromagnetic Disturbances Related to Seismicn Activity  

NASA Astrophysics Data System (ADS)

Based on observational evidence, we suggest that a series of observational and modeling experiments could be carried out to demonstrate the viability of a satellite based earthquake prediction program based on a search for earthquake precursors. The satellite project has an exploratory character and aims first of all to detect the ionosphere plasma and the electromagnetic anomalies related to seismic, meteo and human activity. The observations made by the satellite have the very great advantage of very rapidly covering almost the whole of the active seismic regions in the world and monitoring the effects of a large number of earthquakes. The micro - satellite COMPASS - 2 launched on May 26, 2006. It has the capacity to carry out precise and systematic measurements around the Earth and thus to collect a maximum number of events. Without modifying the payload, like COMPASS - 2, is capable for studying the influence of storms in relation between Sun and Earth, and of assessing the impact of human activities on the ionosphere. The detailed COMPASS - 2 mission and payload description and also some results of measurements are presented. We present electrodynamic model of the atmosphere - ionosphere coupling for interpretation of satellite data. Our model gives an explanation to some electromagnetic and plasma phenomena preceding typhoons and earthquakes by amplification of DC electric field in the ionosphere over disturbed region. This field is connected with the conductivity current flowing in the atmosphere - ionosphere electric circuit, which is formed by external electric currents generated in the lower atmosphere disturbed by typhoon and earthquake preparation processes. Appearance of such currents is associated with upward transport of charged water drops and aerosols in hurricane convection zone and enhancement of charge aerosols emanation with soil gases into the atmosphere caused by growing seismic activity. The most important property of this mechanism is that numerous electromagnetic and plasma effects can be explained by the operation of only one source - an amplification of DC electric field in the ionosphere. This source is controlled by the dynamics of atmospheric processes through modification of electrical parameters of the lower atmosphere and seismic processes. The presented model could be applied to studies of the plasma and electromagnetic effects of large - scale natural and technological disasters.

Kuznetsov, V. D.; Ruzhin, Y. Y.; Sorokin, V. M.

2007-12-01

265

Ionospheric D and E region plasma density enhancements caused by X17-class solar flare on September 7, 2005 - an Arecibo perspective.  

NASA Astrophysics Data System (ADS)

On September 7, 2005 at 1740 UT, Earth orbiting satellies detected a major X17-class solar flare coming from the Sun's eastern limb. The blast caused a complete blackout of HF radio transmissions on the daylit side of Earth. The Arecibo Incohenrent scatter radar was operating as part of the World Month campaign. The radar's power profile (60-500 km) and coded long pulse (CLP) Ion Line experiments were used to get D, E, and F region electron density profiles, and E and F region spectra for temperature, composition, and velocity measurements. High resolution (150 m) plasma line profiles using the observatory's new digital receiver were measured during part of the period. Returned scattered power profiles indicated great enhancement in the D and E region, allowing us to estimate the density enhancement due to this large solar flare. Theoretical support is provided with the Data-Driven D region electron density model together with the Ionospheric Forecast Model developed by the Space Environment Corporation

Vo, H.; Gonzalez, S. A.; Sulzer, M. P.; Aponte, N.; Eccles, V.; Sojka, J.

2005-12-01

266

The current status of the ionospheric observations in NICT  

NASA Astrophysics Data System (ADS)

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.

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

2012-07-01

267

Radar-satellite studies of the high-latitude ionosphere. Final report, 1 August 1989-31 August 1992  

SciTech Connect

Emphasis has been placed on the analysis of multi-instrument experiments investigating the physics of the auroral oval/polar cap boundary and the vicinity of the plasmapause and inner edge of the ring current at mid-latitudes utilizing existing data sets from Millstone Hill and other incoherent scatter radars and available satellite overflights and supporting ground-based information. Ionospheric signatures of the cusp and the mechanisms involved in large-scale plasma transport into the polar cap during magnetic storms have been investigated. Data from Air Force sensors on DMSP satellites have been combined with ground-based observations to examine intense oxygen ion outflow, localized intensifications of the convection electric field, and SAR arcs all of which occur equatorward of the main auroral enhancements during geomagnetic storms. The characteristics of the ring current and plasmasheet particle populations are closely coupled to these ionospheric phenomena.

Foster, J.C.

1992-10-15

268

Effects of pressure gradients and convection on the inner plasma sheet stability  

Microsoft Academic Search

We present a computer model that solves the system of nonlinear MHD equations in dipolar coordinates and is designed specifically to simulate the near-Earth plas ma sheet region which has a near-dipolar field line topology. The objective of this work is a detailed study of the inner plasma sheet as a region of particular importance for auroral processes including the

V. Prosolin; I. Voronkov; E. Donovan

2006-01-01

269

The morphology and physical interpretations of the longitudinal variations in the ionospheric plasma density at low-, mid- and high-latitudes  

NASA Astrophysics Data System (ADS)

As it is well known the longitudinal variations in the ionospheric electron density at equatorial, low-, mid- and high-latitudes have a number of similarities and differences. The data obtained from topside ionospheric sounding, GPS-LEO radio occultation method, worldwide network of ground-based ionosondes and GPS receivers were previously used for investigations of the various kinds of manifestations of the longitudinal ionospheric variability. We discuss and present the brief review of the recent advances and outstanding problems in this important scientific issue. We paid a special attention into our understanding of local time, seasonal, geomagnetic and solar activity dependence of the longitudinal variations in the ionospheric F region parameters. Another main objective of our report is to describe the theoretical understanding and recent model finding of the main formation mechanisms of ionospheric longitudinal variations using the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP). We compared the GSM TIP model results with IRI empirical model, and different observation data (Intercosmos-19 satellite, DPS-4 ionosondes, GPS TEC and COSMIC ionospheric electron content). This work was supported by RFBR Grants ?14-05-00788, ?14-05-00578, and Program 22 RAS.

Klimenko, Maxim; Klimenko, Vladimir; Cherniak, Iurii; Zakharenkova, Irina; Ratovsky, Konstantin; Karpachev, Alexander

270

Ionospheric Feedback Effects on Magnetosphere-Ionosphere Coupling  

NASA Astrophysics Data System (ADS)

A new interactive M-I coupling model is developed to investigate the dynamic interaction between magnetospheric dispersive waves, compressional modes, and auroral electron precipitations. The model is applied to investigate the geomagnetic electromagnetic pulsations observed in Earth's magnetosphere in terms of magnetospheric waves triggered by field line resonances and ionospheric feedback instability. M-I coupling is included by accounting for the closure of magnetospheric field-aligned currents through Pedersen currents in the ionosphere. The height-integrated Pedersen conductivity is treated as a dynamic parameter by electrodynamically coupling the 2D finite element wave model "TOPO" to the ionospheric ionization model "GLOW". It is shown that both mechanisms can be used to explain many features of auroral arcs such as the periodic intensification, FACs, and electric fields. However, unlike in a field line resonance where the ponderomotive force causes the plasma to move mainly along the field line, the plasma in the feedback instability is distributed either as a bump or a cavity along a field line and leads to a multi-banded structure in the radial direction. The nonlinear feedback instability model can explain the formation of plasma density and electromagnetic perturbations with the same frequency, which disagree with current FLR scenario.

Lu, Jianyong; Wang, Wenbin; Rankin, Robert; Marchand, Richard

271

The estimated required minimum flash rate to change the ionosphere dynamics in the electrodynamical coupling model of atmosphere and ionosphere  

NASA Astrophysics Data System (ADS)

We developed an electrodynamical coupling model of atmospheric thunderstorm current system and the ionospheric current system. Using the average flash rate of thunderstorm as a parameter In the coupling model, we calculate the upward current injecting into the ionosphere. From the lower boundary of the ionosphere, the upward current from thunderstorm can be served as input current in the ionospheric current system. With upward current from thunderstorm, the perpendicular electric field is derived using local conductivity tensor at given magnetic latitudes. The associated electric field leads to the plasma ExB drift motion in the ionosphere. The caused plasma motion changes the plasma density, i.e., the changes of observed total electron content. In the nighttime ionosphere, the depletion region caused by thunderstorm current near equator may trigger the plasma bubbles. We also estimate required minimum flash rate to change the ionosphere dynamics. It is found that a cluster of thunderstorms with total flash rate greater than tens of ampere may cause ?TEC ~ 1% and plasma bubbles in the nighttime ionosphere.

Kuo, C.; Hsu, R.; Huba, J. D.; Chen, A. B.; Su, H.; Lee, L.

2013-12-01

272

Three-dimensional MHD simulation of the solar wind interaction with the ionosphere of Venus: Results of two-component reacting plasma simulation  

Microsoft Academic Search

The large-scale solar wind interaction with the Venusian ionosphere is numerically simulated in the framework of two-component, three-dimensional magnetohydrodynamics (MHD). The finite volume total variation diminishing scheme is used to solve this problem. The impinging solar wind is represented by H+ ions, and the ionosphere is assumed to consist of O+ ions produced by photoionization of atomic oxygen in the

T. Tanaka; K. Murawski

1997-01-01

273

Whistlers. [in earth ionosphere and magnetosphere  

NASA Technical Reports Server (NTRS)

Theoretical models of ionospheric whistler phenomena are reviewed and compared with experimental data. Whistlers were characterized as lightning discharges through a dispersive medium in 1919, with the first observed appearance of whistler noises detected in telephone communications. Magneto-ionic theory is used to characterize whistlers, with the Appleton-Hartree equations applied to the wave fields arising from lightning interactions with ionospheric plasma. Large values of the refractive index or slow propagation speeds give rise to the whistler mode, i.e., propagation of the wave through plasmas of any density. Propagation through the ionosphere is examined with the Snell's law, and account is taken of absorption and the necessity of obtaining full-wave solutions. Finally, theories are under development to explain the occurrence of ducting, i.e., guiding of the whistler wave by field-aligned plasma density irregularities.

Park, C. G.

1982-01-01

274

LIFDAR: A Diagnostic Tool for the Ionosphere  

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

275

The critical solar wind pressure for IMF penetration into the Venus ionosphere  

Microsoft Academic Search

Early observations and simulations have revealed that the occurrence of IMF penetration into the Venus ionosphere depends on the upstream solar wind pressure, and that IMF is transported into the ionosphere by the downward convection when the solar wind dynamic pressure is relatively large. In this paper, we investigated the critical solar wind pressure for the IMF penetration, by using

H. Jin; K. Maezawa; T. Mukai

2008-01-01

276

Collisional Joule dissipation in the ionosphere of Venus: The importance of electron heat conduction  

Microsoft Academic Search

The ionosphere of an unmagnetized planet, such as Venus, is characterized by rel- atively high Pedersen conductivity in comparison to the terrestrial ionosphere because of the weak magnetic field. Collisional Joule dissipation of plasma waves might therefore be an important source of heat within the Venus ionosphere. However, any assessment of the importance of colli- sional Joule dissipation must take

R. J. Strangeway

1996-01-01

277

Spatial structure of very low frequency modulated ionospheric currents  

Microsoft Academic Search

The High Frequency Active Auroral Research Project (HAARP) heater has been used to generate Extremely Low Frequency and Very Low Frequency (ELF\\/VLF) electromagnetic radiation in the lower ionosphere since March 1999. The HAARP beam modulates the conductivity of the ionospheric plasma in a region where a small ambient electric field exists. This produces a modulated distribution of currents that primarily

Joseph Allen Payne Jr.

2007-01-01

278

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

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

279

Joule heating of Io's ionosphere by unipolar induction currents  

NASA Technical Reports Server (NTRS)

Electrical induction in Io's ionosphere, due to the corotating plasma bound to the Jovian magnetosphere, is one possible source for the attainment of the high temperatures suggested by the large scale height of Io's ionosphere. Unipolar induction models are constructed to calculate ionospheric joule heating numerically, whose heating rates lie between 10 to the -9th and 10 to the -8th W/cu m. The binding and coupling of the ionosphere is due to the dense, and possibly ionized, neutral SO2 atmosphere, and there appears to be no need to postulate the existence of an intrinsic Ionian magnetic field in order to retain the observed ionnosphere.

Herbert, F.; Lichtenstein, B. R.

1980-01-01

280

Response of the convection electric field on southward turning of the IMF  

NASA Astrophysics Data System (ADS)

We have investigated the response of convection electric fields in the inner magnetosphere on southward turning of the interplanetary magnetic field (IMF), and its spatial dependence using the CRRES spacecraft data measured in the inner magnetosphere. When the southward turning of IMF to -20 nT was measured by IMP-8 twice at 3:12 and 5:52 UT, which was accompanied by a storm with the minimum SYM-H of -216 nT, the CRRES spacecraft was located in the dusk inner magnetosphere and detected enhancements of the convection electric field within 1 min after the southward IMF Bz reaches the dayside magnetopause. The amplitude of the electric field is well reproduced by the Weimer model. These results indicate that plasma convection in the inner magnetosphere quickly responds to the energy input from the solar wind to the magnetosphere, and the time variation can be described by simple mapping of two-cell convection in the ionosphere. However, when the spacecraft is located in the midnight sector, convection electric fields do not quickly respond to southward turning of the IMF. CRRES measured a 20 min delay of enhancements of the electric field at 6.6 RE and 21.5 MLT on March 21, 1991. The amplitude is about a half of the Weimer model electric field mapped onto the spacecraft location. A statistical analysis using 165 events of southward and northward turning of the IMF has clarified that the electric field quickly (< 5 min) responds to IMF variations at the earthward of the inner edge of the electron plasma sheet, while it takes more than 30 min in the plasma sheet. This tendency indicates that plasma convection has a different behavior in and earthward of the plasmasheet.

Nishimura, Y.; Kikuchi, T.; Wygant, J.; Shinbori, A.; Brautigam, D.; Ono, T.; Iizima, M.; Kumamoto, A.

2008-12-01

281

A theoretical study of the production and decay of localized electron density enhancements in the polar ionosphere  

NASA Technical Reports Server (NTRS)

Uniform convection patterns were introduced into a high latitude time-dependent F region model (HLTD) to study if soft auroral particle precipitation is a necessary precondition to blob formation in the ionosphere. Attention was limited to the conditions leading to the formation of parent blobs (dimensions of at least 10 km) due to plasma instabilities. Consideration was given to the effects of discrete auroral structures and to different O(+) precipitation ionization rate profiles during solar maximum conditions in the thermosphere. Blobs were assumed to be produced on the dayside due to ionization caused by sun-aligned arcs. The simulations indicated that parent blobs would form whenever plasma flux tubes in the ionosphere were exposed to soft particle precipitation lasting more than 10 min. The blobs cease to exist when convected to a region with a high particle production rate where the background particle density exceeds that of the blobs. Conditions wherein either hard or soft particle production can produce blobs are outlined.

Sojka, J. J.; Schunk, R. W.

1986-01-01

282

The ionospheric responses in the equatorial anomaly region during the 6-7 April 2000 ionospheric storm  

NASA Astrophysics Data System (ADS)

The great magnetic storm on 6-7 April 2000 generated ionospheric disturbances in the equatorial anomaly region. The ionosonde at Chung-Li (24.9›XN, 121›XE) and the GPS receivers observed the ionosphere during this period. The variations of the ionospheric parameters, NmF2 (plasma density of the F-peak), hmF2 (height of the F-peak) and h­ÝF (minimum virtual height of the F-layer), demonstrate that a traveling atmospheric disturbance (TAD) affects the ionosphere in this region. The simultaneous total electron content (TEC) derived from GPS shows that the crest of equatorial anomaly region moves equatorward. To further understand the causality of ionosphere response, the TIEGCM (Thermosphere/Ionosphere General Circulation Model) has been applied to simulate this event. The agreement and discrepancy between the simulated and observed results will be illustrated and discussed.

Lee, C.; Liu, J.; Chen, M.

2002-05-01

283

Main ionospheric trough as a duct of energy between ionosphere and magnetosphere region  

NASA Astrophysics Data System (ADS)

The mid-latitude electron density trough observed in the topside ionosphere has been shown to be the near-Earth signature of the plasmapause and can provide useful information about the magnetosphere-ionosphere dynamics and morphology. Thus for present the evolution of ionospheric trough in time and space domain we need some multipoint measurements and different type of measurements techniques. To develop a quantitative model of evolution ionospheric trough features during geomagnetic disturbances the analyse of particle and waves in situ measurements and TEC data was carried out. The high resolutions plasma particle diagnostics and wave diagnostics located on board of currently operated satellite DEMETER can give us precisely description of trough signatures and instabilities at define point in space. On the other hand GPS permanent networks such as IGS and EPN provide regular monitoring of the ionosphere in a global scale. The aim of this paper is to present some general behaviour of trough dynamics as well as the fine structures of ionospheric trough and discuss the different type of instability generated inside the trough region from ULF frequency range thru VLF up to HF frequency range. In order to better understand the physical conditions and evolution of ionosphere trough region and describe the coupling between ionosphere and inner magnetosphere the detail examination of geomagnetic storm in January 2005 is presented. As a consequence of different time scales of physical processes occurred in the near Earth environment during geomagnetic disturbances and energy transfer between ionosphere and magnetosphere the examination of ion end electron fluxes inside ionosphere trough are disused.

Rothkaehl, Hanna; Czajkowski, Tomasz; Grzesiak, Marcin; S?omi?ska, Ewa; Wronowski, Roman; S?omi?ski, Jan; Koperski, Piotr; Krankowski, Andrzej

2010-05-01

284

Global Dayside Ionospheric Uplift and Enhancement Associated with Interplanetary Electric Fields  

NASA Technical Reports Server (NTRS)

The interplanetary shock/electric field event of 5-6 November 2001 is analyzed using ACE interplanetary data. The consequential ionospheric effects are studied using GPS receiver data from the CHAMP and SAC-C satellites and altimeter data from the TOPEX/ Poseidon satellite. Data from 100 ground-based GPS receivers as well as Brazilian Digisonde and Pacific sector magnetometer data are also used. The dawn-to-dusk interplanetary electric field was initially 33 mV/m just after the forward shock (IMF BZ = -48 nT) and later reached a peak value of 54 mV/m 1 hour and 40 min later (BZ = -78 nT). The electric field was 45 mV/m (BZ = -65 nT) 2 hours after the shock. This electric field generated a magnetic storm of intensity DST = -275 nT. The dayside satellite GPS receiver data plus ground-based GPS data indicate that the entire equatorial and midlatitude (up to +/-50(deg) magnetic latitude (MLAT)) dayside ionosphere was uplifted, significantly increasing the electron content (and densities) at altitudes greater than 430 km (CHAMP orbital altitude). This uplift peaked 2 1/2 hours after the shock passage. The effect of the uplift on the ionospheric total electron content (TEC) lasted for 4 to 5 hours. Our hypothesis is that the interplanetary electric field ''promptly penetrated'' to the ionosphere, and the dayside plasma was convected (by E x B) to higher altitudes. Plasma upward transport/convergence led to a 55-60% increase in equatorial ionospheric TEC to values above 430 km (at 1930 LT). This transport/convergence plus photoionization of atmospheric neutrals at lower altitudes caused a 21% TEC increase in equatorial ionospheric TEC at 1400 LT (from ground-based measurements). During the intense electric field interval, there was a sharp plasma ''shoulder'' detected at midlatitudes by the GPS receiver and altimeter satellites. This shoulder moves equatorward from -54(deg) to -37(deg) MLAT during the development of the main phase of the magnetic storm. We presume this to be an ionospheric signature of the plasmapause and its motion. The total TEC increase of this shoulder is 80%. Part of this increase may be due to a "superfountain effect." The dayside ionospheric TEC above 430 km decreased to values 45% lower than quiet day values 7 to 9 hours after the beginning of the electric field event. The total equatorial ionospheric TEC decrease was 16%. This decrease occurred both at midlatitudes and at the equator. We presume that thermospheric winds and neutral composition changes produced by the storm-time Joule heating, disturbance dynamo electric fields, and electric fields at auroral and subauroral latitudes are responsible for these decreases.

Tsurutani, Bruce; Mannucci, Anthony; Iijima, Byron; Abdu, Mangalathayil Ali; Sobral, Jose Humberto A.; Gonzalez, Walter; Guarnieri, Fernando; Tsuda, Toshitaka; Saito, Akinori; Yumoto, Kiyohumi; Fejer, Bela; Fuller-Rowell, Timothy J.; Kozyra, Janet; Foster, John C.; Coster, Anthea; Vasyliunas, Vytenis M.

2004-01-01

285

Emission of whistler waves from an ionospheric tether  

E-print Network

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 ...

Takiguchi, Yu

2009-01-01

286

Ionospheric response to the sustained high geomagnetic activity during the March `89 great storm  

SciTech Connect

A simulation was conducted to model the high-latitude ionospheric to the sustaied level of high geomagnetic activity for the great magnetic storm period of March 13-14, 1989. The geomagnetic and solar activity indices and the Defense Meterological Satellite Program (DMSP) F8 and F9 satellite data for particle precipitation and high-latitude convection were used as inputs to a time-dependent ionospheric model (TDIM). The results of the TDIM were compared to both DMSP plasma density data and ground-based total electron content (TEC) measurements for the great storm period as well as with earlier storm observations. The comparisons show that the overall structure of the high-latitude ionosphere was dominated by an increased convection speed within the polar cap that led to increased ion temperatures. In turn, this enhanced the NO(+) density, raised the atomic-to-molecular ion transition height to over 300 km, decreased N(sub m)F(sub 2), increased h(sub m)F(sub 2), and in places either increased n(sub e) at 800 km or slightly decreased it. The morphology of the ionosphere under these extreme conditions was considerably different than that modeled for less distributed intervals. These differences included the character of the dayside tongue of ionization that no longer extended deep into the polar cap. Instead, as a result of the ion heating and consequent reduction in N(sub m)F(sub 2), a large polar hole occupied much of the polar region. This polar hole extended beyond the auroral oval and merged with the night sector midatitude trough. The limitaions associated with the applicability of the TDIM to the geomagnetic conditions present on March 13 and 14 are discussed. The primary limitations of the TDIM derive from the limited temporal resolution of the model input parameters and the lack of suitably dynamic thermospheric specification for the great storm conditions. These limitations leads to midlatitude ionospheric storm phases that do no follow those observed.

Sojka, J.J.; Schunk, R.W.; Denig, W.F. [Utah State Univ., Logan, UT (United States)]|[Phillips Laboratory Air Force Materials Command, Hanscom AFB, MA (United States)

1994-11-01

287

Ionospheric response to the sustained high geomagnetic activity during the March '89 great storm  

NASA Technical Reports Server (NTRS)

A simulation was conducted to model the high-latitude ionospheric to the sustaied level of high geomagnetic activity for the great magnetic storm period of March 13-14, 1989. The geomagnetic and solar activity indices and the Defense Meterological Satellite Program (DMSP) F8 and F9 satellite data for particle precipitation and high-latitude convection were used as inputs to a time-dependent ionospheric model (TDIM). The results of the TDIM were compared to both DMSP plasma density data and ground-based total electron content (TEC) measurements for the great storm period as well as with earlier storm observations. The comparisons show that the overall structure of the high-latitude ionosphere was dominated by an increased convection speed within the polar cap that led to increased ion temperatures. In turn, this enhanced the NO(+) density, raised the atomic-to-molecular ion transition height to over 300 km, decreased N(sub m)F(sub 2), increased h(sub m)F(sub 2), and in places either increased n(sub e) at 800 km or slightly decreased it. The morphology of the ionosphere under these extreme conditions was considerably different than that modeled for less distributed intervals. These differences included the character of the dayside tongue of ionization that no longer extended deep into the polar cap. Instead, as a result of the ion heating and consequent reduction in N(sub m)F(sub 2), a large polar hole occupied much of the polar region. This polar hole extended beyond the auroral oval and merged with the night sector midatitude trough. The limitaions associated with the applicability of the TDIM to the geomagnetic conditions present on March 13 and 14 are discussed. The primary limitations of the TDIM derive from the limited temporal resolution of the model input parameters and the lack of suitably dynamic thermospheric specification for the great storm conditions. These limitations leads to midlatitude ionospheric storm phases that do no follow those observed.

Sojka, J. J.; Schunk, R. W.; Denig, W. F.

1994-01-01

288

Ionosphere around equinoxes during low solar activity  

NASA Astrophysics Data System (ADS)

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) from TOPEX and Jason-1, and TEC from Global Positioning System (GPS) receivers as well as global ionosonde measurements of the F2 layer peak electron density (NmF2) to investigate the behaviors of the daytime ionosphere around equinoxes during low solar activity (LSA). The analysis reveals that during LSA the equinoctial asymmetry in ionospheric plasma density is mainly a low-latitude phenomenon. The differences of equinoctial TEC and NmF2 have considerable amplitudes at low latitudes in both hemispheres and less significant at higher latitudes. With increasing altitude, the asymmetry in COSMIC Ne becomes weaker in the Southern Hemisphere, and the northern pronounced asymmetry regions move toward the magnetic equator. The ionospheric equinoctial asymmetry may be considered as a manifestation of the annual variation, whose annual phase significantly shifts away from the solstices. The F layer peak height (hmF2) extracted from COSMIC Ne profiles also shows an equinoctial asymmetry at low latitudes, indicating the existence of equinoctial differences in low-latitude neutral winds, specifically in the Northern Hemisphere. It reveals that, besides the important effect of the neutral wind, other processes should play roles in the forming of the observed equinoctial asymmetry in the ionosphere.

Liu, Libo; He, Maosheng; Yue, Xin'an; Ning, Baiqi; Wan, Weixing

2010-09-01

289

Formation and detection of high latitude ionospheric irregularities  

NASA Technical Reports Server (NTRS)

Measurements of Total Electron Content (TEC) and airglow variations show that large scale plasma patches appearing in the high-latitude ionsophere have irregular structures evidenced by the satellite phase and amplitude scintillations. Whistler waves, intense quasi-DC electric field, and atmospheric gravity waves can become potential sources of various plamsa instabilities. The role of thermal effects in generating ionospheric irregularities by these sources is discussed. Meter-scale irregularities in the ionospheric E and F regions can be excited parametrically with lower hybrid waves by intense whistler waves. Ohmic dissipation of Pedersen current in the electron gas is able to create ionospheric F region irregularities in plasma blobs or plasma patches (i.e., high ambient plasma density environment) with broad scale lengths ranging from tens of meters to a few kilometers. Through the neutral-charged particle collisions, gravity waves can excite large-scale (less than tens of kilometers) ionospheric irregularities simultaneously with forced ion acoustic modes in the E region. The large-scale ionospheric density fluctuations produced in the E region can extend subsequently alogn the earth's magnetic field to the F region and the topside ionospheric regions. These mechanisms characterized by various thermal effects can contribute additively with other processes to the formation of ionospheric irregularities in the high latitude region.

Lee, M. C.; Buchau, J.; Carlson, H. C., Jr.; Klobuchar, J. A.; Weber, E. J.

1985-01-01

290

Long-lived plasmaspheric drainage plumes: Where does the plasma come from?  

NASA Astrophysics Data System (ADS)

(weeks) plasmaspheric drainage plumes are explored. The long-lived plumes occur during long-lived high-speed-stream-driven storms. Spacecraft in geosynchronous orbit see the plumes as dense plasmaspheric plasma advecting sunward toward the dayside magnetopause. The older plumes have the same densities and local time widths as younger plumes, and like younger plumes they are lumpy in density and they reside in a spatial gap in the electron plasma sheet (in sort of a drainage corridor). Magnetospheric-convection simulations indicate that drainage from a filled outer plasmasphere can only supply a plume for 1.5-2 days. The question arises for long-lived plumes (and for any plume older than about 2 days): Where is the plasma coming from? Three candidate sources appear promising: (1) substorm disruption of the nightside plasmasphere which may transport plasmaspheric plasma outward onto open drift orbits, (2) radial transport of plasmaspheric plasma in velocity-shear-driven instabilities near the duskside plasmapause, and (3) an anomalously high upflux of cold ionospheric protons from the tongue of ionization in the dayside ionosphere, which may directly supply ionospheric plasma into the plume. In the first two cases the plume is drainage of plasma from the magnetosphere; in the third case it is not. Where the plasma in long-lived plumes is coming from is a quandary: to fix this dilemma, further work and probably full-scale simulations are needed.

Borovsky, Joseph E.; Welling, Daniel T.; Thomsen, Michelle F.; Denton, Michael H.

2014-08-01

291

Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System: A UnifiedApproach for Studying Hot and Cold Plasma Interactions  

NASA Astrophysics Data System (ADS)

The Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System is complex; it varies on a wide range in spatial and temporal scales, exhibits relatively thin ion-scale boundaries (e.g., bow shock, magnetopause, magnetotail), contains hot and cold particle populations, and the particle distribution functions are typically non-Maxwellian. The existing space weather frameworks are based on global fluid models and therefore cannot address many important issues concerning particle, momentum, and energy coupling in the system. To remedy this situation, we have formed a multi-disciplinary team to create a new kinetic modeling framework. The new framework will include kinetic electron and ion formulations for the ionosphere, plasmasphere, and polar wind domains, and kinetic ions and fluid electrons for the magnetosphere. The proposed methodology is expected to lead to breakthroughs in studying numerous problems/issues, including the self-consistent formation of the ring current, the self-consistent formation of ion scale turbulence and waves, the calculation of appropriate reconnection rates, the effect that multiple species and ion outflows from the ionosphere have on the development and evolution of storms/substorms, among others. The presentation will focus on the current state and capabilities of the global kinetic models that form the framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind Model.

Karimabadi, H.; Omelchenko, Y.; Schunk, R. W.; Barakat, A. R.; Gardner, L. C.; Khazanov, G. V.; Glocer, A.; Kistler, L. M.

2013-12-01

292

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)

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.

Saka, O.; Hayashi, K.; Thomsen, M.

2014-08-01

293

The Importance of Microphysical Processes in the Magnetosphere-Ionosphere System  

NASA Astrophysics Data System (ADS)

The effects of low-altitude collisionless energy conversion on global aspects of the magnetosphere-ionosphere (M-I) interaction are considered. Electromagnetic power flowing from the magnetosphere into auroral and cusp regions is converted, via an abundance of collisionless plasma processes, to beams of precipitating electrons and transversely accelerated ions (TAIs), principally O+ due to its larger gyroradius. Electron precipitation gates ionospheric Joule dissipation by modifying the ionospheric conductance. Depending on its energy spectrum and flux, precipitation also increases the scale height of the ionosphere, thereby enhancing the source population of TAIs. TAIs become ionospheric outflows under the action of the mirror force. Outflows have the capacity to inflate and stretch the nightside plasmasheet and modify the nightside reconnection rate. Their effects seem to be integral in determining (in global simulations) whether the M-I system, for steady solar wind (SW) driving, settles into a steady magnetospheric convection mode or a sawtooth mode. By enhancing the asymmetric ring current, outflows also effectively change the shape of the magnetospheric boundary, which changes the solar wind - magnetosphere interaction, the dayside reconnection potential, the cross polar cap potential, ionospheric Joule dissipation and the current-voltage characteristics of the SW-M-I interaction. From a dynamical system perspective, one is tempted to trace the causal chain from solar wind and magnetotail dynamos, to the resulting electromagnetic power flows that deposit energy at low altitude, to conversion of this energy to particle beams and heat, and, then, to ascribe observed morphologies of these processes to the distributions of the dynamos. However, it will be shown using global simulation experiments that the morphology and dynamics and, to some extent, the power derived from the dynamos is determined as much by the M-I interaction as by the SW-M interaction. This behavior is indicative of a geospace system exhibiting strong coupling and feedback among its internal elements. That the products of energy conversion (electron beams and ion flows) enabled by local, microphysical processes feedback into global system behavior is also indicative of a scale-interactive system: Large-scale processes regulate microprocesses, which, in turn, regulate the large-scale processes.

Lotko, W.

2012-12-01

294

Magnetospheric plasma interactions  

NASA Astrophysics Data System (ADS)

The Earth's magnetosphere (including the ionosphere) is our nearest cosmical plasma system and the only one accessible to mankind for extensive empirical study by in situ measurements. As virtually all matter in the universe is in the plasma state, the magnetosphere provides an invaluable sample of cosmical plasma from which we can learn to better understand the behavior of matter in this state, which is so much more complex than that of unionized matter. It is therefore fortunate that the magnetosphere contains a wide range of different plasma populations, which vary in density over more than six powers of ten and even more in equivalent temperature. Still more important is the fact that its dual interaction with the solar wind above and the atmosphere below make the magnetopshere the site of a large number of plasma phenomena that are of fundamental interest in plasma physics as well as in astrophysics and cosmology. The interaction of the rapidly streaming solar wind plasma with the magnetosphere feeds energy and momentum, as well as matter, into the magnetosphere. Injection from the solar wind is a source of plasma populations in the outer magnetosphere, although much less dominating than previously thought. We now know that the Earth's own atmosphere is the ultimate source of much of the plasma in large regions of the magnetosphere. The input of energy and momentum drives large scale convection of magnetospheric plasma and establishes a magnetospheric electric field and large scale electric current systems that car ry millions of ampere between the ionosphere and outer space. These electric fields and currents play a crucial role in generating one of the the most spectacular among natural phenomena, the aurora, as well as magnetic storms that can disturb man-made systems on ground and in orbit. The remarkable capability of accelerating charged particles, which is so typical of cosmical plasmas, is well represented in the magnetosphere, where mechanisms of such acceleration can be studied in detail. In situ measurements in the magnetosphere have revealed an unexpected tendency of cosmical plasmas to form cellular structure, and shown that the magnetospheric plasma sustains previously unexpected, and still not fully explained, chemical separation mechanisms, which are likely to operate in other cosmical plasmas as well.

Faelthammar, Carl-Gunne

1994-04-01

295

Saturn: atmosphere, ionosphere, and magnetosphere.  

PubMed

The Cassini spacecraft has been in orbit around Saturn since 30 June 2004, yielding a wealth of data about the Saturn system. This review focuses on the atmosphere and magnetosphere and briefly outlines the state of our knowledge after the Cassini prime mission. The mission has addressed a host of fundamental questions: What processes control the physics, chemistry, and dynamics of the atmosphere? Where does the magnetospheric plasma come from? What are the physical processes coupling the ionosphere and magnetosphere? And, what are the rotation rates of Saturn's atmosphere and magnetosphere? PMID:20299587

Gombosi, Tamas I; Ingersoll, Andrew P

2010-03-19

296

Uplift of Ionospheric Oxygen Ions During Extreme Magnetic Storms  

NASA Technical Reports Server (NTRS)

Research reported earlier in literature was conducted relating to estimation of the ionospheric electrical field, which may have occurred during the September 1859 Carrington geomagnetic storm event, with regard to modern-day consequences. In this research, the NRL SAMI2 ionospheric code has been modified and applied the estimated electric field to the dayside ionosphere. The modeling was done at 15-minute time increments to track the general ionospheric changes. Although it has been known that magnetospheric electric fields get down into the ionosphere, it has been only in the last ten years that scientists have discovered that intense magnetic storm electric fields do also. On the dayside, these dawn-to-dusk directed electric fields lift the plasma (electrons and ions) up to higher altitudes and latitudes. As plasma is removed from lower altitudes, solar UV creates new plasma, so the total plasma in the ionosphere is increased several-fold. Thus, this complex process creates super-dense plasmas at high altitudes (from 700 to 1,000 km and higher).

Tsurutani, Bruce T.; Mannucci, Anthony J.; Verkhoglyadova, Olga P.; Huba, Joseph; Lakhina, Gurbax S.

2013-01-01

297

LISN: A distributed observatory to image and study ionospheric irregularities  

NASA Astrophysics Data System (ADS)

During nighttime the low-latitude ionosphere commonly develops plasma irregularities and density structures able to disrupt radio wave signals. This interference produces an adverse impact on satellite communication and navigation signals. For example, EM signals originated from satellites can suffer fading as deep as 20 dB even at UHF frequencies. In addition, civil aviation is increasingly dependent upon Global Navigation Satellite Systems and disruption of the navigation capability from ionospheric irregularities poses a clear threat to passengers and crews. To monitor and specify the conditions of the ionosphere over South America, the Low-latitude Ionospheric Sensor Network (LISN) was established as a permanent array of scientific instruments that operate continuously and transmit their observables to a central server in a real-time basis. Presently, the LISN observatory includes 3 different types of instruments: (1) 47 GPS receivers, (2) 5 flux-gate magnetometers and (3) 2 Vertical Incidence Pulsed Ionospheric Radar (VIPIR) ionosondes. In addition to providing a nowcast of the disturbed state of the ionosphere over South America, LISN permits detailed studies of the initiation and development of plasma irregularities. By using data assimilation and tomography techniques, LISN provides continuous estimates of several important geophysical parameters that are indispensable to a program aimed at forecasting the plasma electrodynamics and the formation of density structures in the low-latitude ionosphere.

Sheehan, R.; Valladares, C. E.

2013-05-01

298

Origin of ultraviolet emission source in the Jovian ionosphere at the feet of the Io flux tube  

Microsoft Academic Search

A model for an explanation of far ultraviolet (FUV) emissions observed from the Io flux tube footprints at the Jovian ionosphere is presented. An acceleration of electrons and ions of the ionospheric plasma up to sufficient energies for an effective excitation of H2 Lyman and Werner bands is proposed. The neutral particles within the Jovian ionosphere are excited due to

Vladimir E. Shaposhnikov; Valerii V. Zaitsev; Helmut O. Rucker; Galina V. Litvinenko

2001-01-01

299

Semikinetic modeling and observations of high-latitude plasma outflow  

NASA Technical Reports Server (NTRS)

In one fo the most exciting areas of progress, we have now developed a dynamic semikinetic model for examining the synergistic effects of waves and magnetospheric hot plasma populations on the outflowing ionospheric plasma. We have done this by imposing hot biMaxwellian ion and electron distributions at the top of our auroral simulation flux tube (4 R(sub e)), as well as a spectrum of waves with altitude which perpendicularly heats the ionospheric ions. We have also addressed the quasi-statistical properties of out flowing O(+) through bulk parameter analysis of DE-1/RIMS observations when DE-1 was in the midaltitude polar cap magnetosphere. A very exciting paper which was both submitted and appeared during this period in JGR concerned the centrifugal acceleration effect on the polar wind. During this year, we also developed the extension of our GSK code to include the lower ionosphere and associated processes. Finally, perhaps our most exciting project currently is a study of F-region upflows using a modification of the FLIP ionospheric fluid dynamics model of Richards and Torr to allow for the effects of soft electron precipitation ionization and convection-driven ion heating, and performed comparisons with satellite and radar data. A list of reference papers that have been published is listed.

Horwitz, James L.

1995-01-01

300

International reference ionosphere 1990  

NASA Technical Reports Server (NTRS)

The International Reference Ionosphere 1990 (IRI-90) is described. IRI described monthly averages of the electron density, electron temperature, ion temperature, and ion composition in the altitude range from 50 to 1000 km for magnetically quiet conditions in the non-auroral ionosphere. The most important improvements and new developments are summarized.

Bilitza, Dieter; Rawer, K.; Bossy, L.; Kutiev, I.; Oyama, K.-I.; Leitinger, R.; Kazimirovsky, E.

1990-01-01

301

Electric fields in the ionosphere and magnetosphere.  

NASA Technical Reports Server (NTRS)

Review of current techniques for measuring ionospheric and magnetospheric electric fields and existing measurements. Considerable progress in understanding electric fields has been made in the auroral regions where fields originating basically from convection patterns in the magnetosphere and modified by ionospheric interaction have been detected by both the barium ion cloud and double floating probe techniques and have been compared against predictions. The anticorrelation of electric fields and auroral arcs, the establishment of the auroral electrojet currents as Hall currents, the irregular nature of the electric fields, and the reversal of the electric fields between the eastward and westward electrojet regions have been some of the important observations. Recent barium ion cloud observations in the polar cap have indicated that the long assumed electrojet return current across the polar cap does not exist.

Maynard, N. C.

1972-01-01

302

Evidence for the stimulation of field-aligned electron density irregularities on a short time scale by ionospheric topside sounders  

Microsoft Academic Search

Ionospheric topside sounders can be considered to act as mobile ionospheric heating facilities. They stimulate a wide variety of plasma phenomena that suggests that significant plasma heating can be produced in the vicinity of the spacecraft following the short duration (0.1 ms) high-power (hundreds of watts) sounder pulse. Most of these phenomena are sensitive to the ambient plasma conditions, particularly

Robert F. Benson

1997-01-01

303

Stationary electrostatic solitary waves in the auroral plasma  

NASA Technical Reports Server (NTRS)

Time-stationary fluid equations are used to describe electrostatic solitons in an auroral plasma of cold ionospheric and hot plasma sheet particles. A one-dimensional fluid analysis of the four component model auroral plasma indicates that at least two different, weakly damped, small amplitude electrostatic solitons can propagate along the geomagnetic field. The slower of the two is a generalization of an ion-acoustic solitary wave in a multi-component plasma, and ion inertia is negligible for the faster mode which is supported by the two electron components and resembles a clump of shielded negative space charge convected by the drifting plasma sheet electrons. Some expected features of the large amplitude properties are indicated qualitatively, and an analogy is considered between the theory of ion-acoustic shocks and a theory of double layers.

Lotko, W.; Kennel, C. F.

1981-01-01

304

Traveling convection vortices as seen by the SuperDARN HF radars  

NASA Astrophysics Data System (ADS)

Two impulsive traveling convection vortex (TCV) events observed simultaneously by ground based magnetometers and the SuperDARN HF radars in the prenoon sector were studied. In both cases, disturbances traveled westward at speeds of 4-6 km/s. Convection patterns derived from magnetometer measurements and radar observations were overall in reasonable agreement; observed differences at some points might be caused by both the nonuniform ionospheric conductivity distribution and difference in the integration time of the radar and magnetometer data. For one event, the convection patterns obtained from magnetometer data and SuperDARN radar measurements were relatively simple; they can be interpreted as a result of the westward motion of a convection vortex system associated with a pair of field-aligned currents separated in azimuthal direction. This TCV event was associated with relatively low Pc5 pulsation activity, contrary to the second TCV event that was accompanied by a train of Pc5 magnetic pulsations of large amplitude. Convection patterns for the second event were complicated. A simple scenario for the interpretation of the generation of TCVs and Pc5 pulsations is suggested. A sudden impulse in the solar wind dynamic pressure produces disturbances on several boundaries of magnetospheric plasma: on the magnetopause, the LLBL inner edge, and the plasma sheet inner edge. These boundaries are elastic so that surface waves can propagate along them. The high-latitude wave is responsible mainly for TCVs, whereas the low-latitude waves may be responsible for excitation of Pc5 field line resonance pulsations. The scenario explains important features of both TCV events and Pc5 pulsations: both phenomena appear simultaneously and show westward (eastward) propagation, but the TCVs are observed at latitudes close to the LLBL inner edge, whereas the Pc5 pulsations occur at lower latitudes, close to the inner boundary of the plasma sheet.

Lyatsky, W. B.; Sofko, G. J.; Kustov, A. V.; André, D.; Hughes, W. J.; Murr, D.

1999-02-01

305

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)

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.

Zhu, L.; Schunk, R. W.; Scherliess, L.; Sojka, J. J.; Eccles, J. V.

2011-12-01

306

Observations of O+ in transit from the ionosphere: The pipeline  

NASA Astrophysics Data System (ADS)

Energetic O+ ions have important dynamic effects on all regions of the magnetosphere including the ring current. Here we discuss some of the dynamical effects. We emphasize observations of O+ populations escaping from the ionosphere under various geomagnetic conditions and their access to the plasma sheet and ring current. We review data establishing that a significant flux of O+ escapes the ionosphere during geomagnetically quiet intervals. Our analysis suggests that most magnetospheric O+ is in transit between the ionosphere and ring current during the quiet intervals before geomagnetic storms.

Peterson, William; Elkington, Scot; Yau, Andrew W.

307

Modeling Oxygen-Rich Magnetotail Plasma Flows with Global Multi-Fluid MHD  

NASA Astrophysics Data System (ADS)

Earthward and tailward flow channels in Earth's magnetotail result from bursty, patchy reconnection occurring in the mid-tail. The resulting injection fronts transport plasma, entropy, and magnetic flux to and from the inner magnetosphere. Changes in the composition and distribution of magnetospheric plasma due to ionospheric outflow affect these flows, changing inner magnetospheric properties and global magnetospheric states. We examine the effects of ionospheric oxygen outflow on these magnetotail flows using the Multi-Fluid Lyon-Fedder-Mobarry (MFLFM) global MHD code. We compare magnetospheric processes during a simulated stormtime event with and without ionospheric outflow. Ionospheric outflow sources include a low-energy polar wind-type outflow from the polar cap and a higher-energy auroral outflow from the nightside and cusp. We show that the addition of mass and pressure to the magnetotail through O+ outflow increases the frequency and size scale of these dynamic, bursty reconnection events, changing the nature of Earthward convection, plasma transport, and plasmoid formation.

Garcia-Sage, K.; Moore, T. E.

2012-12-01

308

Mesoscale ionospheric tomography at the Auroral region  

NASA Astrophysics Data System (ADS)

FMI (Finnish Meteorological Institute) has used observations from the dense GNSS network in Finland for high resolution regional ionospheric tomography. The observation system used in this work is the VRS (Virtual Reference Station) network in Finland operated by Geotrim Ltd. This network contains 86 GNSS ground stations providing two frequency GPS and GLONASS observations with the sampling rate of 1 Hz. The network covers the whole Finland and the sampling of the ionosphere is very good for observing mesoscale ionospheric structures at the Auroral region. The ionospheric tomography software used by FMI is the MIDAS (Multi-Instrument Data Analysis System) algorithm developed and implemented by the University of Bath (Mitchell and Spencer, 2003). MIDAS is a 3-D extension of the 2-D tomography algorithm originally presented by Fremouw et al. (1992). The research at FMI is based on ground based GNSS data collected in December 2006. The impacts of the two geomagnetic storms during the month are clearly visible in the retrieved electron density and TEC maps and they can be correlated with the magnetic field disturbances measured by the IMAGE magnetometer network. This is the first time that mesoscale structures in the ionospheric plasma can be detected from ground based GNSS observations at the Auroral region. The continuous high rate observation data from the Geotrim network allows monitoring of the temporal evolution of these structures throughout the storms. Validation of the high resolution electron density and TEC maps is a challenge as independent reference observations with a similar resolution are not available. FMI has compared the 3-D electron density maps against the 2-D electron density plots retrieved from the observations from the Ionospheric Tomography Chain operated by the Sodankylä Geophysical Observatory (SGO). Additional validation has been performed with intercomparisons with observations from the ground based magnetometer and auroral camera network (MIRACLE), riometers, and the ionosonde station at SGO. This presentation will show the results from the ionospheric tomography research at FMI. References: Fremouw, E., J. Secan and B. Howe (1992): Application of stochastic inverse theory to ionospheric tomography, Radio Sci., 27(5), 721-732. Mitchell, C.N. and Spencer, P.S.J. (2003): A three-dimensional time-dependent algorithm for ionospheric imaging using GPS, Ann. Geophys., 46, 687-696.

Luntama, J.; Kokkatil, G. V.

2008-12-01

309

Gravity Wave Propagation into the Thermosphere from Deep Convection  

NASA Astrophysics Data System (ADS)

In this talk, we discuss the excitation and propagation of primary gravity waves from deep convective overshoot. We show that many of these fast waves can escape filtering in the lower atmosphere and propagate into the thermosphere. There, gravity waves dissipate, creating thermospheric body forces which rapidly accelerate the local fluid over spatial scales of 100-500 km. This acceleration process creates local "mean" winds which eventually dissipate, and excites upward and downward propagating gravity waves dubbed "secondary waves". Using our new compressible body force model, we calculate the secondary gravity wave spectrum excited by a typical thermospheric body force. We also show the spectrum of secondary waves near the bottomside of the F layer determined from a recent study involving convective overshoot from tropical storm Noel. We find that this secondary wave spectrum agrees well with a spectrum of scales from repeating equatorial plasma bubbles. Additionally, we show that these secondary waves can propagate 20-40 degrees (up to globally), depending on their periods, thereby creating ionospheric variability far from their sources. These secondary gravity waves are the fingerprints of this important but little-understood dynamical process in the thermosphere. Finally, we show that when deep convection occurs over many hours in a localized area, the induced mean winds are coherent because of the coherency of the tidal and planetary wave filtering over these times scales. These mean winds are large, up to 150 m/s in a study over Brazil. Because deep convection tends to have a daily cycle, these mean wind perturbations may manifest themselves as global-scale, migrating or non-migrating tides.

Vadas, Sharon

310

High-latitude ionospheric outflows characterized through analytic formulas  

NASA Astrophysics Data System (ADS)

Recent advances involving multi-fluid treatments have begun to allow the prospect of global magnetospheric models to simulate the dynamics of multiple ion species, such as various ion species originating from sources in the solar wind and terrestrial ionosphere. Such opportunities for the dynamic treatment of ionospheric ions within the magnetosphere portend a need for realistic accessible methods of estimating ionospheric outflows as linked plasma sources for these global models. Toward this end, in this presentation, the results of numerous physics-based simulations of ionospheric plasma outflows under varied driving agents are distilled in terms of relatively compact analytic expressions. The simulations are conducted with the UT Arlington Dynamic Fluid (DyFK) ionospheric plasma transport code. These analytic expressions for O+ and H+ densities, temperatures and flow velocities are obtained at the 3 RE altitudes corresponding to typical inner boundary levels for certain current global magnetospheric models. These O+ and H+ parameters are expressed as functions of precipitation electron energy flux levels, characteristic energy levels of the precipitating electrons, the peak spectral wave densities for low-frequency electrostatic waves which transversely heat ionospheric ions, and solar zenith angle.

Zeng, W.; Horwitz, J. L.

2008-12-01

311

Ionosphere-Thermosphere-Magnetosphere Coupling at Mid-Latitudes  

NASA Astrophysics Data System (ADS)

The ionosphere-thermosphere system at middle and low latitudes is a highly dynamic, nonlinear, and complex system that is strongly coupled to the overlying magnetosphere, particularly during geomagnetic storms. The coupling occurs via electric fields, precipitating particles, and ionosphere-plasmasphere flows. For example, during the early stages of a geomagnetic storm, the magnetospheric electric field can penetrate to the mid-low latitude ionosphere, and it acts to create a region of strong plasma drift. The plasma in the stream drifts in a northwest direction across the United States, which results in enhanced plasma densities in a narrow longitudinal region that extend from Florida to the Great Lakes (Storm Enhanced Densities). In addition, the outer plasmasphere is depleted during geomagnetic storms and this induces ionospheric outflows from both the northern and southern hemispheres, which act to refill the plasmasphere. However, some of the out-flowing ions undergo charge exchange reactions with the background neutrals and become energetic neutrals. The energetic oxygen neutrals don't have sufficient energy to escape and subsequently rain down on the thermosphere, adding mass, momentum, and energy to the mid-low latitude regions of the thermosphere-ionosphere system. These and other ionosphere-thermosphere-magnetosphere coupling issues will be discussed.

Schunk, R. W.

2012-12-01

312

Experimental evidence of electromagnetic pollution of ionosphere  

NASA Astrophysics Data System (ADS)

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.

Pronenko, Vira; Korepanov, Valery; Dudkin, Denis

313

Spatial and temporal evolution of 630. 0 nm airglow enhancement during ionospheric heating experiments  

SciTech Connect

Images of 630.00 nm enhancements have been recorded during the January, 1986 ionospheric heating campaign at Arecibo. The artificial airglow clouds convected eastward, vanished, and then reappeared at the zenith of the HF heater. Occasionally, the airglow patches are bifurcated. The structure and motion of the airglow clouds is an indication of the dynamic behavior of the modified ionosphere. 5 refs., 8 figs.

Bernhardt, P.A.; Duncan, L.M.; Tepley, C.A.; Behnke, R.A.; Sheerin, J.P.

1986-01-01

314

Survey of the ionospheric disturbances related with large seismic events in multi-satellite ionospheric observations  

NASA Astrophysics Data System (ADS)

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.

Ryu, K.; Chae, J.; Lee, E.; Kil, H.

2013-12-01

315

Modeling Convection  

NSDL National Science Digital Library

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.

Schulz, Amanda; Ebert, James R.; Elliott, Nancy A.

2004-09-01

316

Terminator field-aligned currents: A new finding from the Ionospheric Dynamics and Electrodynamics Data Assimilation Model  

NASA Astrophysics Data System (ADS)

new field-aligned current system in the high-latitude ionosphere has been discovered. The finding was based on the reconstructions from the Ionospheric Dynamics and Electrodynamics Data Assimilation Model with the ingestion of ground-based magnetometer measurements. The new current system develops and evolves along the ionospheric terminator, and it is thus termed as the terminator field-aligned currents. This is the first field-aligned current system in the high-latitude ionosphere that is not directly driven by the magnetospheric dynamics and has an ionospheric origin. The study of it will help us to explore the active role of the ionosphere in the magnetosphere-ionosphere coupling and improve the physical understanding of the electrodynamics and plasma dynamics of many small-scale structures in the polar ionosphere.

Zhu, L.; Schunk, R. W.; Eccles, V.; Scherliess, L.; Sojka, J. J.; Gardner, L.

2014-06-01

317

Tsunami Ionospheric warning and Ionospheric seismology  

NASA Astrophysics Data System (ADS)

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.

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

318

Model of Jovian F region ionosphere (Jovian ionosphere model in offset dipole approximation)  

NASA Technical Reports Server (NTRS)

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.

Tan, A.

1990-01-01

319

Plasma jets and plasma bullets  

Microsoft Academic Search

Plasma plumes, or plasma jets, belong to a large family of gas discharges whereby the discharge plasma is extended beyond the plasma generation region into the surrounding ambience, either by a field (e.g. electromagnetic, convective gas flow, or shock wave) or a gradient of a directionless physical quantity (e.g. particle density, pressure, or temperature). This physical extension of a plasma

M G Kong; B N Ganguly; R F Hicks

2012-01-01

320

The Flow of Plasma in the Solar-Terrestrial Environment  

NASA Technical Reports Server (NTRS)

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.

Schunk, Robert W.; Sojka, Jan J.; Barakat, Abdallah R.; Demars, Howard G.; Zhu, Lie

2005-01-01

321

The Comprehensive Inner Magnetosphere-Ionosphere Model  

NASA Astrophysics Data System (ADS)

studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the ring current and plasmasphere on the radiation belts. We have performed a CIMI simulation for the storm on 5-9 April 2010 and then compared our results with data from the Two Wide-angle Imaging Neutral-atom Spectrometers and Akebono satellites. We identify the dominant energization and loss processes for the ring current and radiation belts. We find that the interactions with the whistler mode chorus waves are the main cause of the flux increase of MeV electrons during the recovery phase of this particular storm. When a self-consistent electric field from the CRCM is used, the enhancement of MeV electrons is higher than when an empirical convection model is applied. We also demonstrate how CIMI can be a powerful tool for analyzing and interpreting data from the new Van Allen Probes mission.

Fok, M.-C.; Buzulukova, N. Y.; Chen, S.-H.; Glocer, A.; Nagai, T.; Valek, P.; Perez, J. D.

2014-09-01

322

Low-latitude ionosphere dynamics as deduced from meridional ionosonde chain: Ionospheric ceiling  

NASA Astrophysics Data System (ADS)

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.

Maruyama, Takashi; Uemoto, Junpei; Tsugawa, Takuya; Supnithi, Pornchai; Ishii, Mamoru; Komolmis, Tharadol

323

Sputnik 1 and the First Satellite Ionospheric Experiment  

NASA Astrophysics Data System (ADS)

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.

Sinelnikov, Vyacheslav; Kuznetsov, Vladimir; Alpert, Svetlana

324

Flux Tube Properties and Ionospheric Maps of Magnetotail Currentsheet Thinning  

NASA Astrophysics Data System (ADS)

The growth phase of geomagnetic substorms is characterized by the equatorward motion of the growth phase arc close to or even into the region of diffuse aurora characteristic for a dipolar magnetic field. We have proposed a model of current sheet thinning based on sunward convection to replenish magnetic flux which is eroded on the dayside by magnetic reconnection during periods of southward IMF. This presentation examines the changes of the near Earth magnetotail region as mapped into the ionopshere. The results are using a three-dimensional mesocale MHD simulation of the near Earth tail. Of specific interest are the changes in flux tube volume, flux tube entropy, convection, field-aligend currents, and the size and location of the respective ionospheric footprints of magnetotail structure and properties. We compare results from the simulation model with typical ionospheric and in-situ satellite observations.

Hsieh, M.; Otto, A.

2012-12-01

325

Solar power satellites and the ionosphere - The effect of high power microwave beams on the ionosphere and the chemical effects due to Heavy-Lift Launch Vehicles  

NASA Astrophysics Data System (ADS)

The effects of solar power satellites on the ionosphere are discussed, separated into two categories: (1) passive interactions, in which the ionospheric plasma influences the propagation of the power satellite beam in some way, and in some instances possibly gives rise to co-channel interference through scattering off the beam, and (2) an active inteference, in which ionospheric plasma itself is modified. Strong electron heating from the power satellite beam may produce irregularities in the ionization capable of scattering radio waves of lower frequencies, thereby increasing the potential for broad-band interference. Ionospheric modification may also result from the emission of exhaust effluents from heavy lift launch vehicles, and associated changes in ionospheric chemistry can lead to depletions in ionization at F-region heights. Interference with radio services is briefly discussed.

326

Ionospheric Alfvén resonator response to remote earthquakes  

NASA Astrophysics Data System (ADS)

The ionospheric Alfvén resonances (IARs) are an interesting wave phenomenon well described in the literature. The IAR formation region is located between two bends of the plasma density profile: in the lower part of the ionospheric F region and at altitudes of about 1000-3000 km. In this region, Alfvén waves are entrapped and form standing waves. The quality factor of the resonator can attain a value of 5-10. We studied local IAR features using data of the Borok Geophysical Observatory (58°N, 38° E) and found that the ionospheric Alfvén resonances observed as geomagnetic pulsations at frequencies of a few hertz respond to remote seismic events. There are different kinds of the seismic wave effect on the IARs mode: sometimes the oscillations arise after an earthquake moment, in other cases they sharply decay, and sometimes they abruptly change their intensity. Among possible mechanisms of the earthquake action on the ionosphere acoustic and electromagnetic waves emerged by a seismic shock are discussed. The work was supported by the RFBR grants 09-05-00048 and 10-05-00661.

Potapov, Alexander S.; Dovbnya, Boris V.; Tsegmed, Battuulai

2010-05-01

327

Global Response to Local Ionospheric Mass Ejection  

NASA Technical Reports Server (NTRS)

We revisit a reported "Ionospheric Mass Ejection" using prior event observations to guide a global simulation of local ionospheric outflows, global magnetospheric circulation, and plasma sheet pressurization, and comparing our results with the observed global response. Our simulation framework is based on test particle motions in the Lyon-Fedder-Mobarry (LFM) global circulation model electromagnetic fields. The inner magnetosphere is simulated with the Comprehensive Ring Current Model (CRCM) of Fok and Wolf, driven by the transpolar potential developed by the LFM magnetosphere, and includes an embedded plasmaspheric simulation. Global circulation is stimulated using the observed solar wind conditions for the period 24-25 Sept 1998. This period begins with the arrival of a Coronal Mass Ejection, initially with northward, but later with southward interplanetary magnetic field. Test particles are launched from the ionosphere with fluxes specified by local empirical relationships of outflow to electrodynamic and particle precipitation imposed by the MIlD simulation. Particles are tracked until they are lost from the system downstream or into the atmosphere, using the full equations of motion. Results are compared with the observed ring current and a simulation of polar and auroral wind outflows driven globally by solar wind dynamic pressure. We find good quantitative agreement with the observed ring current, and reasonable qualitative agreement with earlier simulation results, suggesting that the solar wind driven global simulation generates realistic energy dissipation in the ionosphere and that the Strangeway relations provide a realistic local outflow description.

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

2010-01-01

328

Origin of the main auroral oval in Jupiter's coupled magnetosphere–ionosphere system  

Microsoft Academic Search

We show that the principal features of the main auroral oval in the jovian system are consistent with an origin in the magnetosphere–ionosphere coupling currents associated with the departure of the plasma from rigid corotation in the middle magnetosphere, specifically with the inner region of field-aligned current directed upwards from the ionosphere to the magnetosphere. The features we refer to

S. W. H. Cowley; E. J. Bunce

2001-01-01

329

Kinetic description of ionospheric dynamics in the three-fluid approximation  

NASA Technical Reports Server (NTRS)

Conservation equations are developed in the three-fluid approximation for general application problems of ionospheric dynamics in the altitude region 90 km to 800 km for all geographic locations. These equations are applied to a detailed study of auroral E region neutral winds and their relationship to ionospheric plasma motions.

Comfort, R. H.

1975-01-01

330

Titan's ionosphere: Model comparisons with Cassini Ta data T. E. Cravens,1  

E-print Network

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

California at Berkeley, University of

331

Did Tsunami-Launched Gravity Waves Trigger Ionospheric Turbulence over Arecibo?  

Microsoft Academic Search

We report on measurements of ionospheric plasma dynamics conducted at the Arecibo Observatory between 20:00 and 24:00 local time (LT) on December 25 and 26, 2004 using the 430 MHz incoherent scatter radar (ISR). For interpretive purposes these measurements are supported by data from two nearby ionosondes and Global Positioning System (GPS) satellites. The ISR detected different ionospheric behaviors during

R. Pradipta; W. J. Burke; A. Labno; L. M. Burton; J. A. Cohen; S. E. Dorfman; S. P. Kuo

2008-01-01

332

Investigations on ionospheric electron content and electron density irregularities at low latitudes with geostationary satellites  

Microsoft Academic Search

The report embodies the results of continuous measurements of ionospheric electron content and scintillations obtained for the first time with a geostationary satellite over the Indian subcontinent. The observations near the crest of the equatorial anomaly indicate the importance of plasma transport in the equatorial ionosphere. Solar and geomagnetic controls also show some interesting features. It has been observed that

J. N. Bhar; S. Basu; A. Dasgupta; B. K. Guhathakurfa; G. N. Bhattacharyya

1976-01-01

333

C/NOFS Observations of Ionospheric Irregularities  

NASA Astrophysics Data System (ADS)

The Communication/Navigation Outage Forecasting System (C/NOFS) satellite was launched 5 years ago in a 130 inclination orbit, at an altitude between 400 and 850 km. The satellite sensors measure the following: ambient and fluctuating ion densities; ion and electron temperatures; neutral wind; AC and DC electric and magnetic fields; ion drift velocities; ionospheric scintillation and line-of-sight total electron content with the beacon and the GPS occultation receiver. In this talk we mention a few of the scientific results from the C/NOFS mission. The mission started during the lowest solar minimum in 100 years. As a consequence, the pre-reversal enhancement in the upward plasma drift was rarely seen. Thus, C/NOFS rarely detected plasma irregularities in the evening hours. Instead, C/NOFS often observed equatorial plasma bubbles (EPBs) after midnight. However, irregularities did occur in the evening hours as a result of magnetic storms. As the solar cycle activity increased, the pre-reversal enhancement was often present and irregularities were observed in the dusk sector. The C/NOFS data seem to contradict the well-accepted notion that plasma bubbles decay within a few hours and become dead fossil bubbles. EPBs have been observed to remain in the ionosphere with upward plasma drift inside them for 12 and more hours, suggesting that the decay time of plasma irregularities decreases as the ambient ionospheric density increases. C/NOFS also observed EPBs almost equidistant in longitude, about 1000 Km apart, over the whole nightside of the equator region. When the solar cycle activity increased, the F-peak height increased and, close to perigee, C/NOFS flew at times below the F-peak. By examining these events, we surveyed how the F-peak altitude varies with local time, longitude and latitude.

de La Beaujardiere, O.; Huang, C.; Su, Y.; Roddy, P.; Heelis, R. A.; Pfaff, R. F.

2013-12-01

334

Ionospheric Corrections to Tropospheric Retrievals  

NASA Technical Reports Server (NTRS)

Ionosphere affects radio occultations significantly, particularly at stratospheric altitudes. Variations with solar and diurnal cycle are major concerns for observing climate trends. Large scale and small scale ionospheric structure have different impacts. The International Radio Occultation Working Group (CGMS) will benefit from greater participation of the ionospheric community.

Mannucci, A. J.; Ao, C. O.; Iijima, B. A.; Pi, Xiaoqing

2012-01-01

335

Planning for coordinated space and ground-based ionospheric modification experiments  

NASA Technical Reports Server (NTRS)

The planning and conduction of coordinated space and ground-based ionospheric modification experiments are discussed. The purpose of these experiments is to discuss: (1) the nonlinear VLF wave interaction with the ionospheric plasmas; and (2) the nonlinear propagation of VLF waves in the HF-modified ionosphere. It is expected that the HF-induced ionospheric density striations can render the nonlinear mode conversion of VLF waved into lower hybrid waves. Lower hybrid waves can also be excited parametrically by the VLF waves in the absence of the density striations if the VLF waves are intense enough. Laboratory experiments are planned for crosschecking the results obtained from the field experiments.

Lee, M. C.; Burke, William J.; Carlson, Herbert C.; Heckscher, John L.; Kossey, Paul A.; Weber, E. J.; Kuo, S. P.

1990-01-01

336

Ionospheric Transmission Losses Associated with Mars-orbiting Radars  

NASA Technical Reports Server (NTRS)

There are a number of obstacles to radar sounding of the deep Martian subsurface from orbit, including signal losses from the medium conductivity, layer reflective losses, and ground clutter. Another adverse process is signal loss as radio waves propagate through the ionospheric plasma medium. The ionosphere is a plasma consisting of free electrons, ions and neutrals that can effectively damp/attenuate radar signals via electrodneutral collisions. The effect is most severe for transmissions at lower frequencies, which, unfortunately, are also favorable transmissions for deep penetration into the subsurface.

Farrell, W. M.

2005-01-01

337

The HERO project: Rocket experiments in the artificially heated ionosphere  

NASA Astrophysics Data System (ADS)

Heating experiments will be carried out near Tromsoe, Norway: very powerful radio-waves transmitted upwards into the ionosphere give rise to artificially induced modifications of the natural ionospheric plasma. Many of these modification effects can be followed and interpreted by ground based diagnostic installations such as the EISCAT incoherent scatter facility. Some, however, require in situ methods. Therefore heating rocket (HERO) measurements will complement the ground based observations, gathering data on the modified F region plasma. The planned four payloads are described briefly.

Rose, G.

1980-06-01

338

Report from ionospheric science  

NASA Technical Reports Server (NTRS)

The general strategy to advance knowledge of the ionospheric component of the solar terrestrial system should consist of a three pronged attack on the problem. Ionospheric models should be refined by utilization of existing and new data bases. The data generated in the future should emphasize spatial and temporal gradients and their relation to other events in the solar terrestrial system. In parallel with the improvement in modeling, it will be necessary to initiate a program of advanced instrument development. In particular, emphasis should be placed on the area of improved imaging techniques. The third general activity to be supported should be active experiments related to a better understanding of the basic physics of interactions occurring in the ionospheric environment. These strategies are briefly discussed.

Raitt, W. J.; Banks, Peter M.; Nagy, A. F.; Chappell, C. R.

1989-01-01

339

Differences of the Plasma Drift and Upper Thermospheric Wind Behaviour in the Northern and Southern Polar Regions due to the Geomagnetic Field Asymmetry  

NASA Astrophysics Data System (ADS)

The non-dipolar portions of Earth's main magnetic field constitute substantial differences between the geomagnetic field configurations of both hemispheres. They cause in particular different magnetic field flux densities in the opposite polar regions and different offsets of the invariant poles with respect to the rotation axis of the Earth. The offset is presently considerable larger (factor ~2) in the Southern Hemisphere compared to the Northern, which has substantial implications for the coupled magnetosphere-ionosphere-thermosphere system under the influence of external drivers. Recent observations have shown that the ionospheric/thermospheric response to solar wind and IMF dependent processes in the magnetosphere can be very dissimilar in the Northern and Southern Hemisphere. We present statistical studies of both the high-latitude ionospheric convection and the upper thermospheric circulation patterns obtained from almost a decade of measurements starting in 2001 of the electron drift instrument (EDI) on board the Cluster satellites and an accelerometer on board the CHAMP spacecraft, respectively. Using the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model, on the other hand, we simulated a 20-day spring equinox interval of low solar activity with both symmetric dipole and realistic (IGRF) geomagnetic field configurations to prove the importance of the hemispheric differences for the plasma and neutral wind dynamics. The survey of both the numerical simulation and the statistical observation results show some prominent asymmetries between the two hemispheres, which are likely due to the different geographic-geomagnetic offset, or even due to different patterns of geomagnetic flux densities. Plasma drift differences can partly be attributed to differing ionospheric conductivities. The forthcoming Swarm satellite mission will provide valuable observations for further detailed analyses of the North-South asymmetries of plasma convection and neutral wind dynamics.

Foerster, M.; Cnossen, I.; Haaland, S.

2013-12-01

340

HF radar ionospheric clutter  

NASA Astrophysics Data System (ADS)

The characteristics of HF radar echoes reflected from ionization irregularities aligned along the lines of force of the Earth's magnetic field are presented. Utilizing experimental radar-ionospheric clutter data acquired at frequencies between HF and UHF, an analysis is made of the amplitude, the cross-sectional area and the angular extent statistics of HF field-aligned echoes. The Doppler frequency variation, the frequency of occurrence and the diurnal and seasonal variation of HF ionospheric backscatter echoes and their correlation with solar-geophysical conditions are also discussed.

Millman, G. H.

1982-08-01

341

Computerized ionospheric tomography  

SciTech Connect

In this paper the background of computerized tomography (CT) and its application to the ionosphere is reviewed. CT techniques, using only total electron content (TEC) data, can be used to reconstruct a two-dimensional image of the electron density in the ionosphere. The limitations of this technique are discussed and examples showing the limitations and capabilities are presented. Simulation results for two applications are presented: imaging the high latitude trough, and the correction of tracking radar range rate errors. Some possible extensions of the technique are presented.

Austen, J.R.; Raymund, T.D.; Klobuchar, J.A.; Stalker, J.; Liu, C.H.

1990-05-03

342

Gas convection caused by electron pressure drop in the afterglow of a pulsed inductively coupled plasma discharge  

SciTech Connect

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.

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

343

Aspects of magnetosphere-ionosphere coupling in sawtooth substorms: a case study  

NASA Astrophysics Data System (ADS)

In a case study we report on repetitive substorm activity during storm time which was excited during Earth passage of an interplanetary coronal mass ejection (ICME) on 18 August 2003. Applying a combination of magnetosphere and ground observations during a favourable multi-spacecraft configuration in the plasma sheet (GOES-10 at geostationary altitude) and in the tail lobes (Geotail and Cluster-1), we monitor the temporal-spatial evolution of basic elements of the substorm current system. Emphasis is placed on activations of the large-scale substorm current wedge (SCW), spanning the 21:00-03:00 MLT sector of the near-Earth plasma sheet (GOES-10 data during the interval 06:00-12:00 UT), and magnetic perturbations in the tail lobes in relation to ground observations of auroral electrojets and convection in the polar cap ionosphere. The joint ground-satellite observations are interpreted in terms of sequential intensifications and expansions of the outer and inner current loops of the SCW and their respective associations with the westward electrojet centred near midnight (24:00 MLT) and the eastward electrojet observed at 14:00-15:00 MLT. Combined magnetic field observations across the tail lobe from Cluster and Geotail allow us to make estimates of enhancements of the cross-polar-cap potential (CPCP) amounting to ? 30-60 kV (lower limits), corresponding to monotonic increases of the PCN index by 1.5 to 3 mV m-1 from inductive electric field coupling in the magnetosphere-ionosphere (M-I) system during the initial transient phase of the substorm expansion.

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

2014-10-01

344

Convection Movies  

NSDL National Science Digital Library

This page, on the website of Stephane Labrosse of ENS Lyon, presents some examples of flow motions resulting from convection calculations in different situations. All are for infinite Prandtl number and free-slip boundary conditions on horizontal surfaces

Labrosse, Stephane; Lyon, Ens

345

Drift wave instability in the Io plasma torus  

NASA Technical Reports Server (NTRS)

A linear normal mode analysis of the drift wave instability in the Io plasma torus was carried out on the basis of the Richmond (1973) and Huang et al. (1990) analyses of drift waves in the vicinity of the earth's plasmapause. Results indicate that the outer torus boundary is linearly unstable to the growth of electrostatic drift waves. It is shown that the linear growth rate is proportional to the ion drift frequency and to the ratio of the flux tube charge content to the Jovian ionospheric Pedersen conductance. It is also shown that various theoretical models of global radial transport in Jupiter's atmosphere (including corotating convection, interchange diffusion, and transient flux tube convection) can be understood as plausible nonlinear evolutions of electrostatic drift waves.

Huang, T. S.; Hill, T. W.

1991-01-01

346

On formation of Global Cowling channel in the ionosphere and the generalized Ohm's Law  

NASA Astrophysics Data System (ADS)

Time-dependent generalized 3-fluids Ohm's law in the ionosphere is reconsidered. We explicitly show that difference between electric field and E.M.F. (Electro Motive Force, such as Lorentz force, friction force and pressure gradient force acting to electron fluid) become source for radiation of electromagnetic wave. In a spatiotemporal scale much slower than the electron plasma frequency and much larger than the electron inertial length, the electric field and E.M.F should converge to the same value. Thus the evolution of magnetic field in a time scale that we are interested in, is described by the Faraday's law driven by the E.M.F. After time scale that an inductive response is completing, the resultant electrostatic electric field distribution and associated current system is determined to satisfy the current conservation law with appropriate boundary conditions. Using this framework, possible mechanism for current closure from polar to equatorial ionosphere via global Cowling channel is discussed. The Cowling channel is formed by generation of secondary electric field in a cancelling process of accumulated charge caused by Hall current divergence. In our model, a global (primary) Hall current accompanied by two-cell type ionospheric convection induces polarization charge at the conductivity gradient region of dawn-dusk conductivity terminator and magnetic dip-equator. The secondary electric field accompanied by this induced charge generates the secondary Hall current flows along the dawn-side terminator line to the magnetic dip-equator. Resultantly, the global Cowling channel from polar to equatorial ionosphere via the terminator-line and magnetic-dip equator could be formed. Our model shows that enhancement of polar origin equatorial electrojet (EEJ) at morning side region, is due to the converging Hall current from polar to the dawn side dip-equator. Meanwhile, decaying of EEJ is due to the diverging Pedersen current from dusk-side dip-equator to the polar region. This mechanism can be applied to the EEJ disturbances accompanied by the solar wind variations such as DP2-type magnetic field disturbances and many phenomena associate the equatorial enhancement and/or depression of the geomagnetic field disturbances.

Yoshikawa, A.; Nakamizo, A.; Ohtani, S.

2013-12-01

347

The Response of Dayside Ionospheric Upflows to Solar Wind Forcings  

NASA Astrophysics Data System (ADS)

The ionosphere is clearly a significant source of magnetospheric plasma [Chappell et al., 1987] since terrestrial ions have been discovered in the ring current [Johnson et al., 1977], the plasma sheet [Peterson et al., 1981], and the tail lobes [Eastman et al., 1984]. The escape of plasma from the ionosphere to the magnetosphere is a multi-step process that begins with upwelling of ionospheric plasma in the topside. Some distance above the topside, the heavier ions (O+, N+, N2+, O2+, NO+) gain escape energy by one or more of a multitude of wave-particle energization processes. Ionospheric upwelling does not always lead to plasma escape since it can be part of the normal "breathing" of the atmosphere as it responds to changes in the inputs of solar or magnetospheric energy. When upwelling does participate in ion outflow, it can control the flux of escaping ions by the rate at which it feeds thermal plasma to the higher altitude energization regions. In that regard, it is important to understand ionospheric upwelling that occurs in places where escaping ions are generated routinely such as the so-called cleft ion fountain [Lockwood et al., 1985; Valek et al., 2002] and the dayside auroral zone. Using ion driftmeter and RPA data from several DMSP satellites we demonstrate how topside plasma upflow on the dayside responds to variations in the solar wind. We have observed that the intensity of the upflow flux, the location of the upflow region, and the size of the upflow region are highly correlated with solar wind parameters such as the merging electric field and dynamic pressure.

Wilson, G. R.; Germany, G. A.

2007-12-01

348

Solitons and ionospheric heating  

NASA Technical Reports Server (NTRS)

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.

Weatherall, J. C.; Goldman, M. V.; Sheerin, J. P.; Nicholson, D. R.; Payne, G. L.; Hansen, P. J.

1982-01-01

349

Emissions of ionospheric Alfvén resonator and ionospheric conditions  

NASA Astrophysics Data System (ADS)

We analyze continuous magnetic observations of ionospheric Alfvén resonator (IAR) emissions at mid-latitude observatory Mondy. The measurements were by a LEMI-30 search-coil magnetometer covering the period from March 2010 to May 2011. The results are compared with data from simultaneous ionospheric sounding data and International Reference Ionosphere (IRI-2012) model parameters. The large amount of observational data allowed us to inspect the daily and seasonal variations in some morphological characteristics of the emissions as well as their relationship to ionospheric conditions. The main factor affecting the duration of the emission is how long the lower ionosphere stays in Earth's shadow. We demonstrate a close inverse correlation between the diurnal and seasonal IAR frequency variations, on the one hand, and changes in the ionospheric critical frequency, f0F2, on the other. Additionally, the expected emission frequency scale calculated with the IRI-2012 model is in good agreement with the values measured from the emission spectrograms.

Potapov, A. S.; Polyushkina, T. N.; Dovbnya, B. V.; Tsegmed, B.; Rakhmatulin, R. A.

2014-11-01

350

RCM-E and AMIE studies of the Harang reversal formation during a steady magnetospheric convection event  

NASA Astrophysics Data System (ADS)

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.

Yang, Jian; Toffoletto, Frank; Lu, Gang; Wiltberger, Michael

2014-09-01

351

Upper limits to the nightside ionosphere of Mars  

NASA Technical Reports Server (NTRS)

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.

Fox, J. L.; Brannon, J. F.; Porter, H. S.

1993-01-01

352

Nonlinear Ionospheric Propagation Effects on UHF and VLF Radio Signals  

Microsoft Academic Search

An investigation of nonlinear wave-plasma interactions in the ionosphere causing significant propagation effects on VLF and UHF radio waves has been conducted. Nonlinear scattering of VLF waves off existing density irregularities is shown to be responsible for the observed spectral broadening. When the irregularity scale size does not exceed a few tens of meters, the scattered wave is found to

Keith Michael Groves

1991-01-01

353

Joule Heating of the Jovian Ionosphere by Corotation Enforcement Currents  

Microsoft Academic Search

A simple magnetodisk model is used to estimate the Joule heating rate, for several causes of departure from the corotation during whose enforcement heat is deposited on the Jovian magnetosphere. Following compression or expansion of the magnetosphere, the magnetospheric plasma sub- or super-rotates due to conservation of angular momentum and thermal energy is deposited in the ionosphere at a rate

Atsuhiro Nishida; Yukio Watanabe

1981-01-01

354

Magnetospheric convection in the presence of interplanetary magnetic field By: A conceptual model and simulations  

NASA Astrophysics Data System (ADS)

Existing observations from ISEE 3 and new observations from Galileo show that when the interplanetary magnetic field (IMF) has a By component, a By component also develops in the Earth's magnetotail, but only in those quadrants in which the addition of the newly opened magnetic flux tubes occurs. The presence of By on the closed field lines (which is in the same direction as the IMF By) is also seen. We suggest that for a positive IMF By, the magnetopause is open only in the north dawn and south dusk quadrants of the magnetotail. The continuity of magnetic field across the open boundary then requires that a By component be present in the magnetosphere in these quadrants but not in the other two quadrants. We present a model of the magnetospheric convection that postulates cross-tail flows in the mantle/lobe system and the plasma sheet. We suggest that shear flows between the northern and the southern halves of the plasma sheet generate a By component on the closed magnetic field lines. The model is consistent with the two-cell ionospheric convection models constructed from electric field observations by Heppner and Maynard [1987]. Results from global MHD simulations confirm the main features of the proposed model.

Khurana, Krishan K.; Walker, Raymond J.; Ogino, Tatsuki

1996-03-01

355

Moist Convection  

NASA Astrophysics Data System (ADS)

On Jupiter there is little doubt that the water condensation level is the seat of moist convective activity. Two major differences between Earth and Jupiter are the importance of the relatively high molecular weight of water on Jupiter and the altered bottom boundary condition on Jupiter. In addition, the triggering mechanism for convection by large scale motion is not yet understood. On Saturn the Great Storm came at a good time for Cassini observations, and the most interesting is the reversal in direction of the vertical motion tracers parahydrogen and potential temperature. Uranus and Neptune appear, on the basis of much less information, to be more exotic. With a high degree of uncertainty we here conjecture that moist convection on these planets is affected by hydrogen ortho-para latent heat in addition to water and methane and that intermittency is the outcome in both the spatial and temporal domains.

Gierasch, Peter J.

2014-11-01

356

Magnetospheres of Planets and Moons: Links to Their Ionospheres. (Invited)  

NASA Astrophysics Data System (ADS)

The phrase “magnetosphere-ionosphere coupling” has become almost hackneyed in the terrestrial context, but plays an important role in the terrestrial system and must also be emphasized in the context of planetary- and moon-magnetospheres because the underlying principles are similar in all systems. This talk will introduce only two intriguing aspects of the coupling problem for planets and moons. In describing the first topic, we note that, especially for the gas giants Jupiter and Saturn, much of the evidence of magnetosphere-ionosphere coupling is obtained from auroral imaging. In images of Jupiter’s polar ionosphere, bright auroral spots are found to link magnetically to the moons Io, Europa and Ganymede. The spots give evidence of intense field-aligned currents generated near the equator in the interaction between the moons and the flowing plasma of Jupiter’s magnetosphere. The currents must penetrate through regions of impedance mismatch near the upper and lower boundaries of Jupiter’s equatorial plasma torus in order to close in the planetary ionosphere. There is some evidence that the signal propagates through the strong gradient of plasma density at the boundary of the plasma torus by converting into a striated structure that guides high frequency waves. As well, at Io, the interaction has been found to generate localized intense electron fluxes observed to flow along and antiparallel to the magnetic field near the equator. These bidirectional beams are probably accelerated by parallel electric fields near the ionospheric ends of the flux tube, but how the accelerated electrons reach the equator has not been explained. It seems likely that their presence there requires that the (parallel) electric fields in the Jovian ionosphere vary either temporally at high frequency or spatially on short transverse length scales. The full explanation has not yet been developed. As a second example of the role of magnetosphere-ionosphere coupling in planetary systems, we turn to an MHD simulation of the mini-magnetosphere of Ganymede carried out by X. Jia (2010). The significance of the ionosphere in the simulation is that, as the inner plasma boundary, it affects the flow and the dynamics of the entire system. The mathematical reason for the result is evident: differential equations have different solutions for different boundary conditions, but the dramatic changes that arise throughout the entire volume of the magnetosphere as the inner boundary condition is slightly modified may be both surprising and illuminating.

Kivelson, M. G.

2010-12-01

357

A Campaign to Study Equatorial Ionospheric Phenomena over Guam  

NASA Astrophysics Data System (ADS)

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.

Habash Krause, L.; Balthazor, R.; Dearborn, M.; Enloe, L.; Lawrence, T.; McHarg, M.; Petrash, D.; Reinisch, B. W.; Stuart, T.

2007-05-01

358

Monitoring and modeling of ionospheric characteristics in the framework of European COST 296 Action MIERS  

NASA Astrophysics Data System (ADS)

The Mitigation of Ionospheric Effects on Radio Systems COST 296 Action is devoted to the mitigation of ionospheric effects on radio systems. It creates a platform for sharing of data, algorithms, models, and jointly developed advanced technologies, the processing chain from measurements, through algorithms, to operational knowledge. This initiative creates a unique possibility for national groups to consolidate the design of a product required for their own activity and for European assessments in the ionosphere and telecommunication area. An important part of the action is to stimulate and integrate many national and international activities which provide tools for global and regional ionospheric monitoring and modeling. The work includes the near-Earth space plasma monitoring, modeling and forecasting, and a study of the upper atmosphere climate. Well-defined terms of reference include developing ground-based and space-borne monitoring techniques and parameters describing the state of ionospheric plasma, maintaining and extending the flow of real-time and retrospective ionospheric monitoring data to databases. To obtain adequate, high-quality information, special attention is paid to the data ingestion and assimilation in constructing ionospheric models of different spatial and time scale perturbations, as well as storms, small variations, and irregularities. The physical origin of atmospheric/ionospheric effects and their signatures and parameters are investigated. Identification criteria are studied and formulated.

Stanislawska, Iwona; Lastovicka, Jan; Bourdillon, Alain; Zolesi, Bruno; Cander, Ljiljana R.

2010-02-01

359

Solar Surface Magneto-Convection  

E-print Network

Magneto-convection simulations on meso-granule and granule scales near the solar surface are used to study small scale dynamo activity, the emergence and disappearance of magnetic flux tubes, and the formation and evolution of micropores. From weak seed fields, convective motions produce highly intermittent magnetic fields in the intergranular lanes which collect over the boundaries of the underlying meso-granular scale cells. Instances of both emerging magnetic flux loops and magnetic flux disappearing from the surface occur in the simulations. We show an example of a flux tube collapsing to kG field strength and discuss how the nature of flux disappearance can be investigated. Observed stokes profiles of small magnetic structures are severely distorted by telescope diffraction and seeing. Because of the strong stratification, there is little recycling of plasma and field in the surface layers. Recycling instead occurs by exchange with the deep layers of the convection zone. Plasma and field from the surface descend through the convection zone and rise again toward the surface. Because only a tiny fraction of plasma rising up from deep in the convection zone reaches the surface due to mass conservation, little of the magnetic energy resides in the near surface layers. Thus the dynamo acting on weak incoherent fields is global, rather than a local surface dynamo.

Robert F. Stein; Aake Nordlund

2002-09-23

360

Day-side ionospheric conductivities at Mars  

NASA Astrophysics Data System (ADS)

We present estimates of the day-side ionospheric conductivities at Mars based on magnetic field measurements by Mars Global Surveyor (MGS) at altitudes down to ˜100 km during aerobraking orbits early in the mission. At Mars, the so-called ionospheric dynamo region, where plasma/neutral collisions permit electric currents perpendicular to the magnetic field, lies between 100 and 250 km altitude. We find that the ionosphere is highly conductive in this region, as expected, with peak Pedersen and Hall conductivities of 0.1-1.5 S/m depending on the solar illumination and induced magnetospheric conditions. Furthermore, we find a consistent double peak pattern in the altitude profile of the day-side Pedersen conductivity, similar to that on Titan found by Rosenqvist et al. (2009). A high altitude peak, located between 180 and 200 km, is equivalent to the terrestrial peak in the lower F-layer. A second and typically much stronger layer of Pedersen conductivity is observed between 120 and 130 km, which is below the Hall conductivity peak at about 130-140 km. In this altitude region, MGS finds a sharp decrease in induced magnetic field strength at the inner magnetospheric boundary, while the day-side electron density is known to remain high as far down as 100 km. We find that such Titan-like behaviour of the Pedersen conductivity is only observed under regions of strongly draped magnetospheric field-lines, and negligible crustal magnetic anomalies below the spacecraft. Above regions of strong crustal magnetic anomalies, the Pedersen conductivity profile becomes more Earth-like with one strong Pedersen peak above the Hall conductivity peak. Here, both conductivities are 1-2 orders of magnitude smaller than the above only weakly magnetised crustal regions, depending on the strength of the crustal anomaly field at ionospheric altitudes. This nature of the Pedersen conductivity together with the structured distribution of crustal anomalies all over the planet should give rise to strong conductivity gradients around such anomalies. Day-side ionospheric conductivities on Mars (in regions away from the crustal magnetic anomalies) and Titan seem to behave in a very similar manner when horizontally draped magnetic field-lines partially magnetise a sunlit ionosphere. Therefore, it appears that a similar double peak structure of strong Pedersen conductivity could be a more general feature of non-magnetised bodies with ionised upper atmospheres, and thus should be expected to occur also at other non-magnetised terrestrial planets like Venus or other planetary bodies within the host planet magnetospheres.

Opgenoorth, H. J.; Dhillon, R. S.; Rosenqvist, L.; Lester, M.; Edberg, N. J. T.; Milan, S. E.; Withers, P.; Brain, D.

2010-08-01

361

Comparative Ionospheres: All Planets Enjoy Sunshine  

NASA Astrophysics Data System (ADS)

The ionization of a planet's (or moon's) upper atmosphere is caused by energetic photons (EUV and X-rays), augmented by the influx of energetic particles (meteoritic, heliospheric, magnetospheric). The primary structure of an ionosphere, its electron density profile with height Ne(h), results from photochemical processes, with modifications (sometimes dramatically so) due to transport. Typically, the Ne(h) profiles on Venus and Mars conform to photochemical equilibrium, while at Earth both photochemistry and dynamics are needed. For the giant planets, photochemistry alone is unable to match observations. This suggests the need for dynamical processes (winds, E-fields), energetics (e.g., loss via vibrationally-excited molecules), and possible influxes of material (e.g., water products)--- all poorly constrained by observations. Variable solar activity affects all planetary ionospheres, and local plasma instabilities may occur as well. This brief paper provides an overview of known characteristics of planetary ionospheres, and then gives examples of regional and episodic disturbances on Mars as a way to encourage the study of solar-terrestrial planet-relationships (STPR) as a future direction for aeronomy.

Mendillo, M.

2005-12-01

362

OVERCOMING IONOSPHERIC SCINTILLATION FOR WORLDWIDE GPS AVIATION  

E-print Network

in the equatorial area, including Brazil and India, is ionospheric scintillation. Due to electron density irregularities inside the ionosphere, transionospheric radio waves interfere constructively and de- structively

Stanford University

363

Theory of radar detection of solitons during ionospheric heating  

NASA Technical Reports Server (NTRS)

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.

Sheerin, J. P.; Nicholson, D. R.

1983-01-01

364

An atlas of ionospheric F-region structures as determined by the NRL-747/S3-4 ionospheric irregularities satellite investigation  

NASA Astrophysics Data System (ADS)

The Naval Research Laboratory in collaboration with the Air Force Space Test Program and the Office of Naval Research conducted an 'in situ' ionospheric irregularities investigation using pulsed-plasma-probe instrumentation on the polar-orbiting STP/S3-4 satellite. The polar orbit made possible a global study of F-region ionospheric electron densities Ne, temperature Te, irregularity structures delta Ne and associated power spectral distributions Pn(k). The data provide a fundamental base upon which to catalogue similarities and differences between polar and equatorial irregularities and ultimately sort out casual mechanisms coupling plasma instabilities, ionospheric irregularities, and associated effects on communication and surveillance systems. In this report the experimental techniques is briefly described, associated data sets outlined, and a complete catalogue of ionospheric density profiles is presented covering over 600 orbits of data during the period March-September 1978.

Szuszczewicz, E. P.; Holmes, J. C.; Walker, D. N.; Singh, M.; Rodriguez, P.; Swinney, M.; Kegley, L.

1982-07-01

365

Modeling Convection  

ERIC Educational Resources Information Center

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…

Ebert, James R.; Elliott, Nancy A.; Hurteau, Laura; Schulz, Amanda

2004-01-01

366

DC discharge experiment in an Ar/N2/CO2 ternary mixture: A laboratory simulation of the Martian ionosphere's plasma environment  

NASA Astrophysics Data System (ADS)

A low-pressure DC plasma discharge sustained in a 1.6%Ar-2.7%N2-95.3%CO2 ternary mixture is studied. This plasma was generated in a total pressure range from 1.0 to 4.0 Torr, a power of 6.3 W and a 12 l/min flow rate of gases. The electron temperature was found to be 8.41 eV and the ion density, in the order of 109 cm-3. The species observed in the plasma mixture were CO2, CO2+, CN, CO, CO+, O2, O2+, N2, N2+, NO, C+, Ar and Ar+. At the pressure range in the present study, the species observed do not change their intensity due to an increase in the pressure and they separate in two groups according to their emission intensity: the band of the first group (CO2, CO2+ and CN) is approximately a factor of 3 more intense than that of the second group (CO, CO+, O2, O2+, N2, N2+, NO, C+, Ar and Ar+). The behavior of the emission intensities may be correlated to the constant ion density and electron temperature measured. Also, we observed the same constant behavior in the ratios of the neutral and positive species intensities to that of the N2 intensity, as a function of pressure. This may suggest that the different rate coefficients and cross sections of elastic collision, excitation and de-excitation of electronic or vibrational levels, inelastic and superelastic collisions of electrons with the gas phase and products, neutral-neutral interactions, resonant charged transfer processes, recombination, to mention some, to produce these species change in the same proportion, as a function of the pressure to keep the relative ratios of the species almost constant.

Garcia-Cosio, G.; Martinez, H.; Calixto-Rodriguez, M.; Gomez, A.

2011-12-01

367

Penetration of storm-time electric fields to the middle-latitude ionosphere and inner magnetosphere observed by the magnetometers and Akebono satellite  

NASA Astrophysics Data System (ADS)

It has been generally believed that the convection electric field is significantly enhanced in the inner magnetosphere and polar ionosphere during the main phase of geomagnetic storms caused by the strong southward interplanetary magnetic field (IMF) based on the ground magnetometer and satellite observations. The convection electric field penetrates from the polar ionosphere to low-latitude and equatorial ionosphere and drives the global ionospheric DP2 currents which produce magnetic disturbances with clear magnetic local time (MLT) dependence. However, temporal and spatial developments of the storm-time electric fields in the inner magnetosphere and middle-latitude ionosphere have not yet been clarified enough due to the limitation of magnetometer-array observation in the middle latitudes and satellite observations of electric field in the inner magnetosphere. In this study, we have analyzed geomagnetic field variations of H-component obtained from the lowand middle-latitude stations and electric field data observed by the Akebono satellite in order to investigate the change of the global distribution of electric fields and currents associated with the development and decay of geomagnetic storms. At the beginning of the main phase of the geomagnetic storm occurred on July 8-11, 1991, DP2 magnetic field variations associated with a sudden enhancement of the convection electric field clearly appeared in the polar cap, auroral zone, and middle-latitude region at 05:54 (UT) about 3 minutes after the arrival of the strong southward IMF at the IMP satellite position (X=24.8 Re). From the Akebono satellite observation, it is shown that the dawn-to-dusk electric field is significantly enhanced with its magnitude of 1.1 mV/m in the inner magnetosphere (L=2.5) simultaneously with the onset time of the sudden changes of geomagnetic field. Moreover, the magnetic field observations by the GOES-7 and -8 satellites showed a sudden increase of the earthward component indicating the plasma sheet thinning phenomenon associated with the enhancement of the convection electric field in the nightside inner magnetosphere. During the main phase, the Akebono satellite observation showed that a strong dawn-to-dusk electric field locally appears in the inner magnetosphere (L=3.0) with its magnitude of up to 8-10 mV/m. The storm-time electric field seems to correspond to the SAID/SAPS phenomena associated with the development of the region-2 field-aligned currents (R-2 FACs). During the recovery phase, the strong electric field abruptly decays to the level of quiet condition within 3-6 hours. Instead, the reversed convection electric field appears in the inner magnetosphere (L¡3-4) of the afternoon (14-16 h MLT) and post-midnight (01-03 h MLT) with its magnitude of 0.5-1.5 mV/m. The reversed electric field seems to correspond to the shielding electric field produced by the enhanced R-2 FACs.

Shinbori, Atsuki; Tsuji, Yuji; Kikuchi, Takashi; Matsuoka, Ayako

368

Ionospheric Irregularities at High Latitudes During Geomagnetic Storms and Substorms: Simultaneous Observations of Magnetic Field Perturbations and GPS Scintillations  

NASA Astrophysics Data System (ADS)

Plasma instability in the ionosphere is often observed as disturbance and distortion of the amplitude and phase of radio signals, which are known as ionospheric scintillations. High-latitude ionospheric plasma, closely connected to solar wind and magnetospheric dynamics, produce very dynamic and short-lived GPS scintillations, making it challenging to characterize them. This study reports simultaneous observations of geomagnetic pulsations and GPS signal scintillations during geomagnetic storms and substorms using a newly designed Autonomous Adaptive Low-Power Instrument Platform (AAL-PIP) installed at the South Pole. A statistical investigation of the AAL-PIP data recorded from January through May 2012 is presented to study local time distribution of scintillation events and a correlation between GPS scintillation and magnetic field perturbations. This report discusses a possible connection between magnetic field perturbations associated with the ionospheric currents and the creation of plasma instability by examining relative contribution of storm/substorm activity to ionospheric irregularities.

Kim, H.; Deshpande, K.; Clauer, C. R.; Bust, G. S.; Crowley, G.; Humphreys, T. E.; Kim, L.; Lessard, M.; Weatherwax, A. T.; Zachariah, T. P.

2012-12-01