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1

Effects of Ionospheric Conductivity on Convective Flow of Plasma in the Magnetosphere  

Microsoft Academic Search

Convective flow of plasma in the magnetosphere is apparently driven by the interaction between the solar wind and the magnetosphere, but the flow pattern is regulated by the ionosphere and by pressure gradients in the magnetospheric plasma. The equations for conservation of ionospheric currents are used here to deduce theoretical flow patterns. The currents caused by the pressure of magnetospheric

R. A. Wolf

1970-01-01

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

Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitation, Plasma Waves, and Convection Observed by Polar  

NASA Technical Reports Server (NTRS)

The POLAR satellite often observes upflowing ionospheric ions (UFIs) in and near the aurora] oval on southern perigee (approx. 5000 km altitude) passes. We present the UFI features observed by the thermal ion dynamics experiment (TIDE) and the toroidal imaging mass angle spectrograph (TIMAS) in the dusk-dawn sector under two different geomagnetic activity conditions in order to elicit their relationships with auroral forms, wave emissions, and convection pattern from additional POLAR instruments. During the active interval, the ultraviolet imager (UVI) observed a bright discrete aurora on the duskside after the substorm onset and then observed a small isolated aurora form and diffuse auroras on the dawnside during the recovery phase. The UFIs showed clear conic distributions when the plasma wave instrument (PWI) detected strong broadband wave emissions below approx. 10 kHz, while no significant auroral activities were observed by UVI. At higher latitudes, the low-energy UFI conics gradually changed to the polar wind component with decreasing intensity of the broadband emissions. V-shaped auroral kilometric radiation (AKR) signatures observed above -200 kHz by PWI coincided with the region where the discrete aurora and the UFI beams were detected. The latitude of these features was lower than that of the UFI conics. During the observations of the UFI beams and conics, the lower-frequency fluctuations observed by the electric field instrument were also enhanced, and the convection directions exhibited large fluctuations. It is evident that large electrostatic potential drops produced the precipitating electrons and discrete auroras, the UFI beams, and the AKR, which is also supported by the energetic plasma data from HYDRA. Since the intense broadband emissions were also observed with the UFIs, the ionospheric ions could be energized transversely before or during the parallel acceleration due to the potential drops.

Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.; Pollock, C. J.; Gurnett, D. A.; Pickett, J. S.; Persoon, A. M.; Scudder, J. D.; Maynard, N. C.; Mozer, F. S.; Brittnacher, M. J.; Nagai, T.

1998-01-01

4

Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitations, Plasma Waves, and Convection Observed by POLAR  

NASA Technical Reports Server (NTRS)

The POLAR satellite often observes upflowing ionospheric ions (UFls) in and near the auroral oval on southern perigee (approximately 5000 km altitude) passes. We present the UFI features observed by the thermal ion dynamics experiment (TIDE) and the toroidal imaging mass-angle spectrograph (TIMAS) in the dusk-dawn sector under two different geomagnetic activity conditions in order to elicit their relationships with auroral forms, wave emissions, and convection pattern from additional POLAR instruments. During the active interval, the ultraviolet imager (UVI) observed a bright discrete aurora on the dusk side after the substorm onset and then observed a small isolated aurora form and diffuse auroras on the dawn side during the recovery phase. The UFls showed clear conic distributions when the plasma wave instrument (PWI) detected strong broadband wave emissions below approximately 10 kHz, while no significant auroral activities were observed by UVI. At higher latitudes, the low-energy UFI conics gradually changed to the polar wind component with decreasing intensity of the broadband emissions. V-shaped auroral kilometric radiation (AKR) signatures observed above approximately 200 kHz by PWI coincided with the region where the discrete aurora and the UFI beams were detected. The latitude of these features was lower than that of the UFI conics. During the observations of the UFI beams and conics, the lower-frequency fluctuations observed by the electric field instrument (EFI) were also enhanced, and the convection directions exhibited large fluctuations. It is evident that large electrostatic potential drops produced the precipitating electrons and discrete auroras, the UFI beams, and the AKR, which is also supported by the energetic plasma data from HYDRA. Since the intense broadband emissions were also observed with the UFIs. the ionospheric ions could be energized transversely before or during the parallel acceleration due to the potential drops.

Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.; Pollock, C. J.; Gurnett, D. A.; Persoon, A. M.; Scudder, J. D.; Maynard, N. C.; Mozer, F. S.; Brittnacher, M. J.; Nagai, T.

1997-01-01

5

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

6

SuperDARN observations of ionospheric convection and magnetospheric reconnection  

NASA Astrophysics Data System (ADS)

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

Watanabe, Masakazu

7

A new method to reconstruct the ionospheric convection patterns in the polar cap  

NASA Astrophysics Data System (ADS)

A new method to reconstruct the instantaneous convection pattern in the Earth's polar ionosphere is suggested. Plasma convection in the polar cap ionosphere is described as a hydrodynamic incompressible flow. This description is valid in the region where the electric currents are field aligned (and hence, the Lorentz body force vanishes). The problem becomes two-dimensional, and may be described by means of stream function. The flow pattern may be found as a solution of the boundary value problem for stream function. Boundary conditions should be provided by measurements of the electric field or plasma velocity vectors along the satellite orbits. It is shown that the convection pattern may be reconstructed with a reasonable accuracy by means of this method, by using only the minimum number of satellite crossings of the polar cap. The method enables us to obtain a reasonable estimate of the convection pattern without knowledge of the ionospheric conductivity.

Israelevich, P. L.; Ershkovich, A. I.

1999-06-01

8

Comparison between ionospheric convection vortices and the associated equivalent currents  

Microsoft Academic Search

The equivalent current pattern derived from CANOPUS, NRCAN\\/GSC and MACCS magnetometers has been compared with the ionospheric convection pattern observed by SuperDARN HF radars. The discrepancies between the equivalent convection (EQC) and the SuperDARN-observed convection (SDC) patterns are explained in terms of the effect of day-night photoionization conductance gradient and the coupling between field-aligned currents (FACs) and ionospheric conductances. In

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

2004-01-01

9

Convection surrounding mesoscale ionospheric flow channels  

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

10

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

11

Plasma jet effects on the ionospheric plasma  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

12

The response of the large scale ionospheric convection pattern to changes in the IMF and substorms - Results from the SUNDIAL 1987 campaign  

NASA Astrophysics Data System (ADS)

Multipoint observations of ionospheric convection, made during the SUNDIAL 1987 campaign (May 29 to June 8) which included two intervals of variable IMF Bz and By and several substorms, are used to examine the response of the ionospheric convection in the postdusk and midnight sectors to changes in the IMF Bz component, as well as the effect of substorms on ionospheric convection. It was found that the primary ionospheric effect of a change in the IMF from positive Bz to negative Bz is an enhancement in plasma flow magnitude. The response time of the ionospheric convection to each southward turning varies from 15 min near 1800 MLT to 30 min near 2100 MLT and close to one hour near midnight. During one of the substorms, which consisted of several intensifications, the nightside flow reversal moved progressively to earlier local times in response to each substorm intensification.

Lester, M.; de La Beaujardiere, O.; Foster, J. C.; Freeman, M. P.; Luehr, H.; Ruohoniemi, J. M.; Swider, W.

1993-07-01

13

Tropical convection, ionospheric potentials and global circuit variation  

NASA Technical Reports Server (NTRS)

The ionospheric potential (VI), a measure of the earth's overall electric field intensity, correlates with the classic 'Carnegie curve' diurnal variation in electric field caused by the global distribution of thunderstorms. A comparison of VI variation with satellite images of high tropical cloud fields indicates that equatorial thunderstorms over the continents are dominant in maintaining the earth's electric field. VI time series obtained at just one location may provide a high-resolution measure of intense tropical convection.

Markson, R.

1986-01-01

14

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

15

Ionospheric plasma acceleration at Mars: ASPERA-3 results  

Microsoft Academic Search

The Analyzer of Space Plasma and Energetic Atoms (ASPERA) on-board the Mars Express spacecraft (MEX) measured penetrating solar wind plasma and escaping\\/accelerated ionospheric plasma at very low altitudes (250 km) in the dayside subsolar region. This implies a direct exposure of the martian topside atmosphere to solar wind plasma forcing leading to energization of ionospheric plasma. The ion and electron

R. Lundin; D. Winningham; S. Barabash; R. A. Frahm; H. Andersson; M. Holmström; A. Grigoriev; M. Yamauchi; H. Borg; J. R. Sharber; J.-A. Sauvaud; A. Fedorov; E. Budnik; J.-J. Thocaven; K. Asamura; H. Hayakawa; A. J. Coates; D. R. Linder; D. O. Kataria; C. Curtis; K. C. Hsieh; B. R. Sandel; M. Grande; M. Carter; D. H. Reading; H. Koskinen; E. Kallio; P. Riihelä; W. Schmidt; T. Säles; J. Kozyra; N. Krupp; J. Woch; M. Fränz; J. Luhmann; S. McKenna-Lawler; R. Cerulli-Irelli; S. Orsini; M. Maggi; E. Roelof; D. Williams; S. Livi; P. Wurz; P. Bochsler

2006-01-01

16

Study of mid-latitude ionospheric convection during quiet and disturbed periods using the SuperDARN Hokkaido radar  

NASA Astrophysics Data System (ADS)

Westward ionospheric convective flows around midnight are frequently observed at mid-latitudes. They can be generated by so-called disturbance dynamo mechanisms working mainly in the mid-latitudes. To understand the influence of disturbance dynamo effects in the mid-latitudes, we studied the latitudinal distribution of westward flows in association with several kinds of geomagnetic disturbances using the SuperDARN Hokkaido radar. This radar creates high temporal resolution (1 s to 2 min), two-dimensional observations measuring the line-of-sight velocities of ionospheric plasma irregularities, which can be regarded as line-of-sight velocities of ionospheric convection in the mid-latitude region from 40° to 50°. This region could not be monitored using preexisting SuperDARN radars. In this study, we used ionospheric echo data obtained by the SuperDARN Hokkaido radar over 5 years (December 2006 to November 2011). We identified westward flows around midnight at about 40° to 55° geomagnetic latitude. Additionally, the data showed that the westward flow around midnight intensified under high geomagnetic activity (high Kp). This suggests that the disturbance dynamo could affect the mid-latitude ionospheric convection. We performed Superposed Epoch Analysis (SEA) to study the influences from the geomagnetic disturbances on mid-latitude ionospheric convection. We found no obvious influence during major storms (minimum Dst below -60 nT). SEA was also used to study the temporal and latitudinal dependence on the influences from substorms. From analysis of 36 events of AL-defined substorms, we saw that the influence of substorms lasted from 5 to 20 h after the onset between 44° and 53° geomagnetic latitude. The westward flow at mid-latitude grew to a maximum at 12 h after the geomagnetic substorm onset. This is consistent with the results of past numerical simulation studies of the disturbance dynamo effects.

Zou, Yun; Nishitani, Nozomu

2014-08-01

17

Evolution of Artificial Plasma Inhomogeneities in the Earth's Ionosphere  

NASA Astrophysics Data System (ADS)

The authors generalize for the first time in the literature the data concerning plasma clouds injection in the ionosphere. The difussion and drift of the plasma clouds in the magnetic fields are discussed in detail with taking account of real parameters of the ionosphere, the initial configuration of plasma and for arbitrary orientation of the artificial inhomogeneities. The works on modeling of the dispersion processes in the ionosphere are generalized. A comparison analysis of the experimental data and theoretical results has been given. The book is designed for specialists in the area of ionospheric physics and Near -Earth cosmic space. It can be usefull for students and doctorands in radiophysics, geophysics and radiocommunications.

Filipp, N. D.; Oraevskij, V. N.; Blaunshtein, N. Sh.; Ruzhin, Iu. Ya.

1986-10-01

18

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

19

Evidence that solar wind fluctuations substantially affect the strength of dayside ionospheric convection  

E-print Network

magnetic field exhibits high ULF power. We find that ULF power enhances the convection strengthEvidence that solar wind fluctuations substantially affect the strength of dayside ionospheric magnetic field (IMF) is not strongly southward and the IMF By is not large. Such enhanced convection flows

Lyons, Larry

20

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

21

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

22

Ionospheric physics  

SciTech Connect

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

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

1991-01-01

23

Cassini measurements of cold plasma in the ionosphere of Titan.  

PubMed

The Cassini Radio and Plasma Wave Science (RPWS) Langmuir probe (LP) sensor observed the cold plasma environment around Titan during the first two flybys. The data show that conditions in Saturn's magnetosphere affect the structure and dynamics deep in the ionosphere of Titan. The maximum measured ionospheric electron number density reached 3800 per cubic centimeter near closest approach, and a complex chemistry was indicated. The electron temperature profiles are consistent with electron heat conduction from the hotter Titan wake. The ionospheric escape flux was estimated to be 10(25) ions per second. PMID:15894529

Wahlund, J E; Boström, R; Gustafsson, G; Gurnett, D A; Kurth, W S; Pedersen, A; Averkamp, T F; Hospodarsky, G B; Persoon, A M; Canu, P; Neubauer, F M; Dougherty, M K; Eriksson, A I; Morooka, M W; Gill, R; André, M; Eliasson, L; Müller-Wodarg, I

2005-05-13

24

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

25

Interhemispheric Conjugacy of High-Latitude Ionospheric Convection Determined From DMSP IMF-Dependent Models  

NASA Astrophysics Data System (ADS)

In this study we report on a series of new ionospheric convection models constructed from the DMSP thermal ion drift measurements for both the northern and southern polar regions and for the summer, winter, and equinox. Applying the regression analysis technique to the IMF and DMSP data, we first obtained four basic elements of the convection response on 1-nT changes in the corresponding IMF component: (a) the two-cell, ``quasi-viscous'' convection (i.e., for IMF ~0 (b) the lobe convection cell controlled by the IMF azimuthal component; (c) the merging two-cell convection driven by the IMF southward orientation; and (d) the near-pole, two-cell ``reverse'' convection caused by the northward IMF. Then we fitted the obtained distributions of regression coefficients by the spherical harmonics; the resulting DMSP-based ionospheric convection model (DICM) is fully parameterized by the IMF strength and direction. After comparisons with other available high-latitude convection patterns organized by the IMF ``clock-angle'', we concluded that DICM shows all expected features of the solar wind-magnetosphere-ionosphere coupling. A new element in our model is its ``quasi-viscous'' term, which has not been yet obtained in any other satellite or radar-based ionospheric convection studies. Another new elements are the DICM seasonal dependence and interhemispheric symmetry/asymmetry features; for example, we found that the summer cross-polar potentials are 10-15% smaller than the winter potentials. The latter is in agreement with the seasonal dependence of field-aligned currents and with the voltage-current relationship required for the proper magnetosphere-ionosphere coupling. The obtained results justify a need in developing a unified approach for the modeling of high-latitude ionospheric convection from various data sources (i.e., from ground magnetometers, radars, digisondes, and satellite observations) allowing seemliness data assimilation in various ``space weather'' applications. The new models can be run on-line at the SPRL Web site http://www.sprl.umich.edu/mist/.

Papitashvili, V. O.; Rich, F. J.

2001-12-01

26

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

27

Contribution of low-energy ionospheric protons to the plasma sheet  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

28

Some aspects of modelling the high-latitude ionospheric convection from Cluster/Edi data  

NASA Astrophysics Data System (ADS)

Measurements onboard Cluster satellites are briefly described, which form the base for determining the intensity and direction of the electric field in the magnetosphere. The aim of this paper is to describe (1) the methodology of calculating the potential distribution at the ionospheric level and the results of constructing spatiotemporal convection patterns for different orientations of the IMF vector in the GSM YZ plane; (2) derivation of basic convection patterns (BCPs), which allow to deduce the statistical ionospheric convection pattern at high latitudes for any IMF Bz and By values (statistical convection model) using different sets of independent data; (3) the consequences of enlarging the amount of data used for analysis; (4) the results of potential calculations with various orders of the spherical harmonics describing them; (5) determination of the cross-polar cap potential with different IMF sector widths (? from 45° down to 10°); (6) the results of our trials to determine the contribution of the IMF Bx component to the convection pattern.

Förster, M.; Feldstein, Y. I.; Gromova, L. I.; Dremukhina, L. A.; Levitin, A. E.; Haaland, S. E.

2013-01-01

29

Stimulated plasma instability and nonlinear phenomena in the ionosphere  

Microsoft Academic Search

Several hundred topside ionograms, corresponding to both high- and low-power sounder operation, were used to investigate stimulated wave-particle interactions in the ionosphere. The investigation combined the benefits of high frequency resolution Alouette 2 analog sounder data with modern digital graphics techniques. One of the main conclusions of the study is that the sounder pulse can cause significant plasma heating when

Robert F. Benson

1982-01-01

30

Average patterns of precipitation and plasma flow in the plasma sheet flux tubes during steady magnetospheric convection  

NASA Technical Reports Server (NTRS)

Average patterns of plasma drifts and auroral precipitation in the nightside auroral zone were constructed during a steady magnetospheric convection (SMC) event on February 19, 1978. By comparing these patterns with the measurements in the midtail plasma sheet made by ISEE-1, and using the corresponding magnetic field model, the following features are inferred: (1) the concentration of the earthward convection in the midnight portion of the plasma sheet (convection jet); (2) the depleted plasma energy content of the flux tubes in the convection jet region; and (3) the Region-1 field-aligned currents generated in the midtail plasma sheet. It is argued that these three elements are mutually consistent features appearing in the process of ionosphere-magnetosphere interaction during SMC periods. These configurational characteristics resemble the corresponding features of substorm expansions (enhanced convection and 'dipolarized' magnetic field within the substorm current wedge) and appear to play the same role in regulating the plasma flow in the flux tubes connected to the plasma sheet.

Sergeev, V. A.; Lennartsson, W.; Pellinen, R.; Vallinkoski, M.; Fedorova, N. I.

1990-01-01

31

Ionospheric Plasma Bubbles observed at 29 degree south  

NASA Astrophysics Data System (ADS)

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

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

32

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

33

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

34

Computer Simulation of Convective Plasma Cells  

E-print Network

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

Carboni, Rodrigo

2015-01-01

35

Multi-Scale Observations of Plasma Conditions and Features in the Coupled Mid-Latitude Ionosphere and Plasmasphere  

NASA Astrophysics Data System (ADS)

Energy input to the terrestrial ionosphere, magnetosphere, and plasmasphere during disturbed intervals manifests itself on subauroral field lines in a complex interplay between induced and feedback Region 2 associated currents, large and small scale plasma transport, embedded plasma irregularities, and enhanced ionospheric recombination processes. Particularly dramatic examples of tight magnetosphere-ionosphere-plasmasphere coupling mechanisms include storm enhanced density plumes feeding significant electron density content into high latitude convection, and fast westward/poleward transport within the sub-auroral polarization stream. The advent of modern enhanced distributed observation networks at mid-latitudes in the American longitude sector provides an opportunity to investigate these mid-latitude associated coupling processes and phenomena in a targeted, more optimized manner. We will discuss plans and initial results from using these capabilities for focused observations, applying simultaneous GPS total electron content maps, mid-latitude SuperDARN HF radar backscatter, and Millstone Hill UHF incoherent scatter radar observations. In particular, we use the multi-hour magnetic local time coverage and continuous monitoring of the mid-latitude SuperDARN network, along with predictive capabilities, as a prompt trigger for regional ionospheric plasma diagnostics with the wide coverage Millstone Hill system. The resulting observational set advances studies of plasma conditions and drivers before and during the emergence of sub-auroral polarization stream events and related phenomena.

Erickson, P. J.; Ruohoniemi, J. M.; Baker, J. B.; de Larquier, S.; Thomas, E. G.; Shepherd, S. G.; Coster, A. J.

2012-12-01

36

The ionosphere as a fully adequate source of plasma for the earth's magnetosphere  

Microsoft Academic Search

A series of recent measurements of the outflow of ionization from the ionosphere have further heightened the awareness of the strength of the ionospheric source of magnetospheric plasmas. In this paper the ionospheric contribution of the polar wind and cleft ion fountain at energies less than 10 eV has been added to the previously measured sources; this total ion outflow

C. R. Chappell; T. E. Moore; J. H. Jr. Waite

1987-01-01

37

Interplanetary magnetic field control of the ionospheric field-aligned current and convection distributions  

NASA Astrophysics Data System (ADS)

Patterns of the high-latitude ionospheric convection and field-aligned current (FAC) are a manifestation of the solar wind-magnetosphere-ionosphere coupling. By observing them we can acquire information on magnetopause reconnection, a process through which solar wind energy enters the magnetosphere. We use over 10 years of magnetic field and convection data from the CHAMP satellite and Super Dual Auroral Radar Network radars, respectively, to display combined distributions of the FACs and convection for different interplanetary magnetic field (IMF) orientations and amplitudes. During southward IMF, convection follows the established two-cell pattern with associated Region 1 and Region 2 FACs, indicating subsolar reconnection. During northward IMF, superposed on a weak two-cell pattern there is a reversed two-cell pattern with associated Region 0 and Region 1 FACs on the dayside, indicating lobe reconnection. For dominant IMF Bx, the sign of Bz determines whether lobe or subsolar reconnection signatures will be observed, but Bx will weaken the signatures compared to pure northward or southward IMF. When the IMF rotates from northward to duskward or dawnward, the distinct reversed and forward two-cell patterns start to merge into a distorted two-cell pattern. This is in agreement with the IMF By displacing the reconnection location from the open lobe field lines to closed dawn or dusk field lines, even though IMF Bz>0. As the IMF continues to rotate southward, the distorted pattern transforms smoothly to that of the symmetric two-cell pattern. While the IMF direction determines the configuration of the FACs and convection, the IMF amplitude affects their intensity.

Juusola, L.; Milan, S. E.; Lester, M.; Grocott, A.; Imber, S. M.

2014-04-01

38

Galileo radio occultation measurements of Io's ionosphere and plasma wake  

NASA Astrophysics Data System (ADS)

Six radio occultation experiments were conducted with the Galileo orbiter in 1997, yielding detailed measurements of the distribution and motion of plasma surrounding Io. This distribution has two components. One is highly asymmetric, consisting of a wake or tail that appears only on the downstream side and extends to distances as large as 10 Io radii. The other resembles a bound ionosphere and is present within a few hundred kilometers of Io's surface throughout the upstream and downstream hemispheres. Motion of plasma within the wake was measured through cross correlation of data acquired simultaneously at two widely separated terrestrial antennas. Plasma near Io's equatorial plane is moving away from Io in the downstream direction. Its speed increases from 30 kms-1 at a distance of 3 Io radii from the center of Io to 57 kms-1 at 7 Io radii. The latter corresponds to corotation with Jupiter's magnetic field, which suggests that bulk plasma motion rather than wave motion is being observed. Results for the bound ionosphere include vertical profiles of electron density at 10 locations near Io's terminator. The ionosphere is substantial, with the peak density exceeding 50,000 cm-3 at 9 out of 10 locations and reaching a maximum of 277,000 cm-3. The peak density varies systematically with Io longitude, with maxima near the center of the hemispheres facing toward (0°W) and away from (180°W) Jupiter and minima near the center of the downstream (90°W) and upstream (270°W) hemispheres. This pattern may be related to the Alfvénic current system induced by Io's motion through magnetospheric plasma. The vertical extent of the bound ionosphere increases from ~200 km near the center of the upstream hemisphere to ~400 km near the boundary between the leading and trailing hemispheres. There is a close resemblance between one ionospheric profile and a Chapman layer, and the topside scale height implies a plasma temperature of 202+/-14K if Na+ is the principal ion. Two intense volcanic hot spots, Kanehekili and 9606A, may be influencing the atmospheric structure at this location.

Hinson, D. P.; Kliore, A. J.; Flasar, F. M.; Twicken, J. D.; Schinder, P. J.; Herrera, R. G.

1998-12-01

39

The response of the large scale ionospheric convection pattern to changes in the IMF and substorms - Results from the SUNDIAL 1987 campaign  

Microsoft Academic Search

Multipoint observations of ionospheric convection, made during the SUNDIAL 1987 campaign (May 29 to June 8) which included two intervals of variable IMF Bz and By and several substorms, are used to examine the response of the ionospheric convection in the postdusk and midnight sectors to changes in the IMF Bz component, as well as the effect of substorms on

M. Lester; O. de La Beaujardiere; J. C. Foster; M. P. Freeman; H. Luehr; J. M. Ruohoniemi; W. Swider

1993-01-01

40

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.

41

Some peculiarities of the procedure for determination of ionospheric plasma parameters during natural disturbances in the ionosphere  

NASA Astrophysics Data System (ADS)

An anomalous change of the spectrum of signals scattered by the ionospheric plasma was observed with the incoherent scatter radar of the Institute of Ionosphere during the strong geomagnetic storm on 30 May 2003. The change was observed for 1.5 h at heights from 700 to 1200 km. Such phenomenon was detected with the use of Kharkiv incoherent scatter radar for the first time. The results of the observations are presented and a procedure for determination of the disturbed ionosphere is described.

Lysenko, V. N.; Cherniak, Yu. V.

42

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

43

Artificial plasma jet in the ionosphere  

NASA Astrophysics Data System (ADS)

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

Haerendel, G.; Sagdeev, R. Z.

44

Ionospheric convection signatures of the interchange cycle at small interplanetary magnetic field clock angles  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to show a "proof of the existence" of the ionospheric situation that is expected for the interchange cycle, during periods of favorable interplanetary magnetic field (IMF) and dipole tilt conditions. To do so, we present three case studies of dayside high-latitude ionospheric convection that is observed around the equinoxes (near-zero dipole tilt) and at small IMF clock angles (one ?c ˜ -30° event and two ?c ˜ 30° events, where ?c ? Arg(BZ + iBY)), using Super Dual Auroral Radar Network (SuperDARN)/Defense Meteorological Satellite Program (DMSP)/National Oceanic and Atmospheric Administration (NOAA) data in the Northern Hemisphere and, when available, DMSP data in the Southern Hemisphere. The convection pattern exhibits twin reverse cells in both hemispheres, but the constituents of each cell are different. In the Northern Hemisphere, for ?c ˜ 30° (?c ˜ -30°), the center of the dawnside (duskside) cell is located poleward of the polar cap boundary, while the center of the duskside (dawnside) cell is located equatorward of the polar cap boundary. For ?c ˜ 30°, we confirmed that the above-mentioned dawn-dusk relation reverses in the Southern Hemisphere. The north-south asymmetric behavior of the conjugate reverse cells, on the dawnside and duskside each, is consistent with two independent interchange cycles that result from the coupling of IMF-lobe reconnection in one hemisphere with lobe-closed reconnection in the opposite hemisphere.

Watanabe, Masakazu; Sofko, George J.; Yan, Xi; McWilliams, Kathryn A.; St.-Maurice, Jean-Pierre; Koustov, Alexandre V.; Hussey, Glenn C.; Hairston, Marc R.

2010-12-01

45

The influence of convection electric fields on thermal proton outflow from the ionosphere  

NASA Technical Reports Server (NTRS)

The continuity, momentum and energy hydrodynamic equations for an O(+)-H(+) ionosphere have been solved self-consistently for steady state conditions when a perpendicular (convection) electric field is present. Comparison of the H(+) temperature profiles obtained with and without the electric field show that the effect of the electric field is to enhance the H(+) temperature at high altitudes from about 3600 to 6400 K. Due to ion heating by the electric field, there is a net reduction of O(+) in the F2-region as compared with the case of a nonconvecting ionosphere. When the reduction of O(+) is neglected, the electric field acts to increase the H(+) outward flux. However, when the reduction of O(+) is included, there is a net reduction in the outward H(+) flux. Nevertheless, the convection electric field still results in an increase in the rate of depletion of the F-region ionization due to H(+) outflow, by a factor of 2.2 for a 100 mV/m electric field.

Raitt, W. J.; Schunk, R. W.; Banks, P. M.

1977-01-01

46

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

47

Spherical cap harmonic analysis of Super Dual Auroral Radar Network (SuperDARN) observations for generating maps of ionospheric convection  

Microsoft Academic Search

A spherical cap harmonic analysis (SCHA) technique is introduced for mapping the 2-D high-latitude ionospheric convection pattern based on Super Dual Auroral Radar Network (SuperDARN) velocity measurements. The current method for generating such maps is the FIT technique which generates global-scale maps over the entire convection region. This is accomplished by combining observations with a statistical model to prevent unphysical

R. A. D. Fiori; D. H. Boteler; A. V. Koustov; G. V. Haines; J. M. Ruohoniemi

2010-01-01

48

Aurora and convection channel events in response to solar wind - magnetosphere - ionosphere interaction processes (Invited)  

NASA Astrophysics Data System (ADS)

We describe the ionospheric manifestations of the temporal-spatial evolution of open magnetic field lines during the first 20 min after the onset of pulsed magnetopause reconnectionevents, appearing in the form of aurora and convection channel events. We then discuss their relevance to our understanding of temporal-spatial structure in the reconnecting magnetosphere. We first distinguish between two consecutive phases of this evolution, depending on time elapsed since reconnection (``newly open''and "old open" field lines). Phase 1 consists of the auroral brightening events appearing on the pre- and postnoon sides of the ``midday gap aurora'' and associated flow channels (FC 1 in our terminology; originally known as pulsed ionospheric flows; PIFs) as described by Southwood (1987). The auroral brightenings in both sectors expand noonward and poleward, followed by a fading phase in the regime of mantle precipitation after appr. 10 min. The later phase 2 (time since reconnection appr. 10-20 min) is characterized by the appearance of a 200-300 km wide channel of enhanced (> 1 km/s) antisunward convection located on the dusk - or dawn side of the polar cap, the location depending on the IMF By polarity. This fast flow appears within the regime of polar rain precipitation. This is our flow channel FC 2. In the case of a By - dominated IMF orientation (|By/Bz| > 1) flow channel FC 2 contributes to extending the dawn-dusk convection asymmetry of polar cap flows tailward of the cusp region. The momentum transfer from high magnetospheric altitudes (cusp dynamo) to the ionosphere is attributed to a system of C1-C2 Birkeland currents (HCC-LCC currents of Taguchi et al., 1993) located poleward of the R1-R2 currents. In many instances a considerable fraction of the CPCP potential is associated with these flow channels. In the case of strongly south IMF orientation (|By/Bz| < 1) a different, more symmetric FC 2 configuration appears, characterized by flow channels on both sides of the polar cap. The FC 2 flow channels appear in the form of events ``directly driven'' by IMF southward turnings or as a sequence of appr. 10 min long ``spontaneous events'' during intervals of quasi-steady IMF orientation. The two phases of the flow evolution (the FC 1 and FC 2 events) in the convection cycle are clearly manifest in ground magnetic deflections. In particular, the Svalgaard-Mansurov effect appearing at longitudes tailward of the cusp is due to Hall currents in FC 2.

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

2010-12-01

49

Electric Field Double Probe Measurements for Ionospheric Space Plasma Experiments  

NASA Technical Reports Server (NTRS)

Double probes represent a well-proven technique for gathering high quality DC and AC electric field measurements in a variety of space plasma regimes including the magnetosphere, ionosphere, and mesosphere. Such experiments have been successfully flown on a variety of spacecraft including sounding rockets and satellites. Typical instrument designs involve a series of trades, depending on the science objectives, type of platform (e.g., spinning or 3-axis stabilized), expected plasma regime where the measurements will be made, available telemetry, budget, etc. In general, ionospheric DC electric field instruments that achieve accuracies of 0.1 mV/m or better, place spherical sensors at large distances (10m or more) from the spacecraft body in order to extend well beyond the spacecraft wake and sheath and to achieve large signal-to-noise ratios for DC and long wavelength measurements. Additional sets of sensors inboard of the primary, outermost sensors provide useful additional information, both for diagnostics of the plasma contact potentials, which particularly enhance the DC electric field measurements on non-spinning spacecraft, and for wavelength and phase velocity measurements that use the spaced receiver or "interferometer" technique. Accurate attitude knowledge enables B times V contributions to be subtracted from the measured potentials, and permits the measured components to be rotated into meaningful geophysical reference frames. We review the measurement technique for both DC and wave electric field measurements in the ionosphere discussing recent advances involving high resolution burst memories, multiple baseline double probes, new sensor surface materials, biasing techniques, and other considerations.

Pfaff, R.

1999-01-01

50

The interplanetary electric field, cleft currents and plasma convection in the polar caps  

NASA Technical Reports Server (NTRS)

The relationship between the pattern of plasma convection in the polar cleft and the dynamics of the interplanetary electric field (IEF) is examined theoretically. It is shown that owing to the geometrical properties of the magnetosphere, the East-West component of the IEF will drive field-aligned currents which connect to the ionosphere at points lying on either side of noon, while currents associated with the North-South component of the IEF will connect the two polar caps as sheet currents, also centered at 12 MLT. In order to describe the consequences of the Interplanetary Magnetic Field (IMF) effects upon high-latitude electric fields and convection patterns, a series of numerical simulations was carried out. The simulations were based on a solution to the steady-state equation of current continuity in a height-integrated ionospheric current. The simulations demonstrate that a simple hydrodynamical model can account for the narrow 'throats' of strong dayside antisunward convection observed during periods of southward interplanetary IMF drift, as well as the sunward convection observed during periods of strongly northward IMF drift.

Banks, P. M.; Clauer, C. R.; Araki, T.; St. Maurice, J. P.; Foster, J. C.

1984-01-01

51

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

52

Comparison of ionospheric convection and the transpolar potential before and after solar wind dynamic pressure fronts: implications for magnetospheric reconnection  

NASA Astrophysics Data System (ADS)

The solar wind dynamic pressure, both through its steady state value and through its variations, plays an important role in the determination of the state of the terrestrial magnetosphere and ionosphere, its effects being only secondary to those of the Interplanetary Magnetic Field (IMF). Recent studies have demonstrated the significant effect solar wind dynamic pressure enhancements have on ionospheric convection and the transpolar potential. Further studies have shown a strong response of the polar cap boundary and thus the open flux content of the magnetosphere. These studies clearly illustrate the strong coupling of solar wind dynamic pressure fronts to the terrestrial magnetosphere-ionosphere system. We present statistical studies of the response of Super Dual Auroral Radar Network (SuperDARN) flows, and Assimilative Mapping of Ionospheric Electrodynamics (AMIE) transpolar potentials to sudden enhancements in solar wind dynamic pressure. The SuperDARN results show that the convection is enhanced within both the dayside and nightside ionosphere. The dayside response is more clear and immediate, while the response on the nightside is slower and more evident for low IMF By values. AMIE results show that the overall convection, represented by the transpolar potential, has a strong response immediately after an increase in pressure, with magnitude and duration modulated by the background IMF Bz conditions. We compare the location of the SuperDARN convection enhancements with the location and motion of the polar cap boundary, as determined by POLAR Ultra-Violet Imager (UVI) images and runs of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic model for specific events. We find that the boundary exhibits a poleward motion after the increase in dynamic pressure. The enhanced ionospheric flows and the poleward motion of the boundary on the nightside are both signatures of enhanced tail reconnection, a conclusion that is reinforced by the observation of the enhanced flows crossing the polar cap boundary in selected case studies when simultaneous measurements are available.

Boudouridis, A.; Zesta, E.; Lyons, L. R.; Kim, H.-J.; Lummerzheim, D.; Wiltberger, M.; Weygand, J. M.; Ruohoniemi, J. M.; Ridley, A. J.

2012-04-01

53

Ionospheric chemical releases  

NASA Technical Reports Server (NTRS)

Ionospheric plasma density irregularities can be produced by chemical releases into the upper atmosphere. F-region plasma modification occurs by: (1) chemically enhancing the electron number density; (2) chemically reducing the electron population; or (3) physically convecting the plasma from one region to another. The three processes (production, loss, and transport) determine the effectiveness of ionospheric chemical releases in subtle and surprising ways. Initially, a chemical release produces a localized change in plasma density. Subsequent processes, however, can lead to enhanced transport in chemically modified regions. Ionospheric modifications by chemical releases excites artificial enhancements in airglow intensities by exothermic chemical reactions between the newly created plasma species. Numerical models were developed to describe the creation and evolution of large scale density irregularities and airglow clouds generated by artificial means. Experimental data compares favorably with theses models. It was found that chemical releases produce transient, large amplitude perturbations in electron density which can evolve into fine scale irregularities via nonlinear transport properties.

Bernhardt, Paul A.; Scales, W. A.

1990-01-01

54

Plasma bubbles in the topside ionosphere: solar activity dependence  

NASA Astrophysics Data System (ADS)

The present study deals with the He+ density depletions, observed during a high solar activity at the topside ionosphere heights. There are the indications that plasma bubbles, produced by Rayleigh-Taylor instability at the bottomside of ionosphere, could rise up to the topside ionosphere and plasmasphere. Maryama and Matuura (1984), using ISS-b spacecraft data (high solar activity - F10.7=200, 1978-80), have seen the plasma bubbles in Ne density over equator at 1100 km heights in 46 cases in 1700 passes (3%). However, there is distinctly another picture in He+ density depletions according to ISS-b spacecraft data for the same period. They occur in the topside ionosphere over low- and middle- latitudinal regions (L=1.3-3) in 11% of the cases (Karpachev, Sidorova, 2002; Sidorova, 2004, 2007). The detailed study of the He+ density depletion characteristics was done. It was noted that the He+ density depletions are mostly seen in the evening-night sector (18-05 LT) from October till May. It was like to the peculiarities of the Equatorial Spread-F (ESF), usually associated with plasma bubble. The monthly mean He+ density depletion statistics, plotted in LT versus month, was compared with the similar plots for ESF statistics, obtained by Abdu and colleagues (2000) from ground-based ionograms over Brazilian regions for the period of the same solar activity. It was revealed good enough correlation (R=0.67). Also depletion values as function of LT were compared with the vertical plasma drift velocity variations, obtained for the same period from AE-E spacecraft and IS radar (Jicamarca) data. Striking similarity in development dynamics was revealed for the different seasons. It was concluded, that the He+ density depletions should be considered as originating from equatorial plasma bubbles. It seems the plasma bubbles, reaching the topside ionosphere altitudes, are mostly seen not in electron density but in He+ density as depletions. According to publications, many cases of the He+ density depletions were revealed on OGO-4, OGO-6, Oreol-1 and DE-2 spacecraft data. The most of these cases occur during high and maximal solar activity periods, when the He+ density layer is very well developed at the topside ionosphere heights (Wilford et al., 2003). Using the model of the plasma bubble formation as suggested by Woodman and La Hoz (1976), it was shown that the topside plasma bubbles, seen in He+ density, are rather typical phenomena for the topside ionosphere for high solar activity epoch. REFERENCE Abdu, M.A., J.H.A. Sobral, I.S. Batista, Equatorial spread F statistics in the american longitudes: some problems relevant to ESF description in the IRI scheme, Adv. Space Res., vol. 25, pp. 113-124, 2000. Karpachev, A.T. and L.N. Sidorova, Occurrence probability of the light ion trough and subtrough in ??+ density on season and local time, Adv. Space Res., vol. 29, pp. 999-1008, 2002. 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. 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. Wilford, C.R., R.J. Moffett, J.M. Rees, G.J. Bailey, Comparison of the He+ layer observed over Arecibo during solar maximum and solar minimum with CTIP model results, J. Geophys. Res., vol. 108, A12, pp. 1452, doi:10.1029/2003JA009940, 2003. Woodman, R.F. and C. La Hoz, Radar observations of F-region equatorial irregularities, J. Geophys. Res., vol. 81, pp. 5447-5466, 1976.

Sidorova, L.

2009-04-01

55

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

56

Measuring ionospheric electron density using the plasma frequency probe  

SciTech Connect

During the past decade, the plasma frequency probe (PFP) has evolved into an accurate, proven method of measuring electron density in the ionosphere above about 90 km. The instrument uses an electrically short antenna mounted on a sounding rocket that is immersed in the plasma and notes the frequency where the antenna impedance is large and nonreactive. This frequency is closely related to the plasma frequency, which is a direct function of free electron concentration. The probe uses phase-locked loop technology to follow a changing electron density. Several sections of the plasma frequency probe circuitry are unique, especially the voltage-controlled oscillator that uses both an electronically tuned capacitor and inductor to give the wide tuning range needed for electron density measurements. The results from two recent sounding rocket flights (Thunderstorm II and CRIT II) under vastly different plasma conditions demonstrate the capabilities of the PFP and show the importance of in situ electron density measurements of understanding plasma processes. 9 refs.

Jensen, M.D.; Baker, K.D. (Utah State University, Logan (United States))

1992-02-01

57

AGN-driven convection in galaxy-cluster plasmas  

E-print Network

This paper describes how active galactic nuclei can heat galaxy-cluster plasmas by driving convection in the intracluster medium. A model is proposed in which a central supermassive black hole accretes intracluster plasma at the Bondi rate and powers a radio source. The central radio source produces cosmic rays, which mix into the thermal plasma. The cosmic-ray luminosity is proportional to the mass accretion rate. The cosmic-ray pressure gradient drives convection, which causes plasma heating. It is assumed that plasma heating balances radiative cooling. The plasma heating rate is self-regulating because the Bondi accretion rate is a decreasing function of the specific entropy near the cluster center; if heating exceeds cooling, then the central entropy increases, the Bondi rate and cosmic-ray luminosity decrease, and the convective heating rate is reduced. This paper focuses on the role of intracluster magnetic fields, which affect convection by causing heat and cosmic rays to diffuse primarily along magnetic field lines. A new stability criterion is derived for convection in a thermal-plasma/cosmic-ray fluid, and equations for the average fluid properties in a convective cluster are obtained with the use of a nonlocal two-fluid mixing length theory. Numerical solutions of the model equations compare reasonably well with observations without requiring fine tuning of the model parameters.

Benjamin D. G. Chandran

2005-06-04

58

The influence of IMF on the lower ionosphere plasma in high and middle latitudes  

NASA Technical Reports Server (NTRS)

As shown by ground-based absorption measurements, the lower ionospheric plasma is markedly controlled by the structure of the IMF. Whereas in high auroral and subauroral latitudes this effect is very pronounced, in midlatitudes its influence is less important. A comparison of these results with satellite data of the IMF and the solar wind speed confirms the important role of these components, not only during special events but also for the normal state of the ionospheric D region plasma.

Bremer, J.

1989-01-01

59

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

60

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

61

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

62

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

SciTech Connect

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

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

2014-04-15

63

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

64

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

NASA Astrophysics Data System (ADS)

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.; Popel, S. I.; Yu, M. Y.

2009-06-01

65

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

Microsoft Academic Search

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

S. I. Kopnin; S. I. Popel; M. Y. Yu

2009-01-01

66

Dayside ionospheric convection changes in response to long-period interplanetary magnetic field oscillations: Determination of the ionospheric phase velocity  

SciTech Connect

Ground magnetic field perturbations recorded by the CANOPUS magnetometer network in the 7 to 13 MLT sector are used to examine how reconfigurations of the dayside polar ionospheric flow take place in response to north-south changes of the IMF. During the 6-hour interval in question IMF B[sub z] oscillates between [plus minus] 7 nT with about a 1-hour period. Corresponding variations in the ground magnetic disturbance are observed which the authors infer are due to changes in ionospheric flow. Cross correlation of the data obtained from two ground stations at 73.5[degrees] magnetic latitude, but separated by [approximately]2 hours in MLT, shows that changes in the flow are initiated in the prenoon sector ([approximately]10 MLT) and then spread outward toward dawn and dusk with a phase speed of [approximately]5 km s[sup [minus]1] over the longitude range [approximately]8 to 12 MLT, slowing to [approximately] 2 km s[sup [minus]1] outside this range. Cross correlating the data from these ground stations with IMP 8 IMF B[sub z] records produces a MLT variation in the ground response delay relative to the IMF which is compatible with these deduced phase speeds. The authors interpret these observations in terms of the ionospheric response to the onset, expansion and decay of magnetic reconnection at the dayside magnetopause.

Saunders, M.A.; Freeman, M.P.; Southwood, D.J.; Cowley, S.W.H. (Imperial College of Science, Technology and Medicine, London (United Kingdom)); Lockwood, M. (Rutherford Appleton Lab., Oxfordshire (United Kingdom)); Samson, J.C. (Univ. of Alberta, Edmonton (Canada)); Farrugia, C.J. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Hughes, T.J. (National Research Council of Canada, Ottawa, Ontario (Canada))

1992-12-01

67

Plasma distribution at Mars and ionospheric magnetic fields: A lesson from Venus  

Microsoft Academic Search

MAG\\/ER experiment on Mars Global Surveyor (MGS), spacecraft has shown the presence of large-scale horizontal magnetic fields in the ionosphere of Mars. These fields can be used to explain the ``depressed'' nature of electron density profiles observed by the radio occultation experiments, since the horizontal fields can inhibit upward diffusion of plasma and reduce the plasma scale heights in the

A. K. Dwivedi; K. K. Mahajan

2004-01-01

68

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

NASA Astrophysics Data System (ADS)

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

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

1984-04-01

69

Convective transport of plasma in the inner Jovian magnetosphere  

NASA Astrophysics Data System (ADS)

The transport of plasma in the inner Jovian magnetosphere is investigated according to the corotating convection model of Hill et al. (1981), emphasizing mathematical aspects of the theory. A simplified but physically plausible boundary condition at the inner Io torus, representing a 5 percent density enhancement of S(+) ions in an 'active sector' that is fixed in Jovian (system III) longitude is employed. The convection electric field pattern resulting from this longitudinal mass anomaly alone is investigated, and then the theory to include the effects of Coriolis force and plasma acceleration is generalized. It is found that even a small (about 5 percent) longitudinal asymmetry of the inner torus produces a convection system capable of removing torus plasma from the magnetosphere on a time scale of order one month.

Liu, W. W.; Hill, T. W.

1990-04-01

70

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

71

Stimulated Raman and Compton scattering of high energy laser beams in a disturbed ionospheric space plasma environment - Linear theory  

Microsoft Academic Search

The interaction of a high energy laser beam with the ionospheric space plasma environment is discussed. The plasma is considered to be inhomogeneous, underdense, collisional, and embedded in a magnetic field. Linear theory is used to compute the growth rates for stimulated Raman scattering and beam filamentation parametric instabilities using several values for laser beam intensity and disturbed ionospheric space

M. K. Keskinen; H. L. Rowland; P. K. Chaturvedi; Y. C. Lee

1989-01-01

72

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

73

Dayside ionospheric convection changes in response to long-period interplanetary magnetic field oscillations - Determination of the ionospheric phase velocity  

NASA Technical Reports Server (NTRS)

Ground magnetic field perturbations recorded by the CANOPUS magnetometer network in the 7 to 13 MLT sector are used to examine how reconfigurations of the dayside polar ionospheric flow take place in response to north-south changes of the IMF. During the 6-h interval in question, IMF Bz oscillates between +/- 7 nT with about a 1-h period. Corresponding variations in the ground magnetic disturbance are observed which we infer are due to changes in ionospheric flow. Cross correlation of the data obtained from two ground stations at 73.5 deg magnetic latitude, but separated by about 2 hours in MLT, shows that changes in the flow are initiated in the prenoon sector (about 10 MLT) and then spread outward toward dawn and dusk with a phase speed of about 5 km/s over the longitude range about 8 to 12 MLT, slowing to about 2 km/s outside this range. Cross correlating the data from these ground stations with IMP 8 IMF Bz records produces a MLT variation in the ground response delay relative to the IMF which is compatible with these deduced phase speeds.

Saunders, M. A.; Freeman, M. P.; Southwood, D. J.; Cowley, S. W.; Lockwood, M.; Samson, J. C.; Farrugia, C. J.; Hughes, T. J.

1992-01-01

74

Modeling of the Convection and Interaction of Ring Current, Plasmaspheric and Plasma Sheet Plasmas in the Inner Magnetosphere  

NASA Technical Reports Server (NTRS)

Distinctive sources of ions reside in the plasmasphere, plasmasheet, and ring current regions at discrete energies constitute the major plasma populations in the inner/middle magnetosphere. They contribute to the electrodynamics of the ionosphere-magnetosphere system as important carriers of the global current system, in triggering; geomagnetic storm and substorms, as well as critical components of plasma instabilities such as reconnection and Kelvin-Helmholtz instability at the magnetospheric boundaries. Our preliminary analysis of in-situ measurements shoves the complexity of the plasmas pitch angle distributions at particularly the cold and warm plasmas, vary dramatically at different local times and radial distances from the Earth in response to changes in solar wind condition and Dst index. Using an MHD-ring current coupled code, we model the convection and interaction of cold, warm and energetic ions of plasmaspheric, plasmasheet, and ring current origins in the inner magnetosphere. We compare our simulation results with in-situ and remotely sensed measurements from recent instrumentation on Geotail, Cluster, THEMIS, and TWINS spacecraft.

Fok, Mei-Ching; Chen, Sheng-Hsien; Buzulukova, Natalia; Glocer, Alex

2010-01-01

75

The response of the high-latitude ionosphere to IMF variations  

Microsoft Academic Search

The convection of plasma in the high-latitude ionosphere is strongly affected by the interplanetary magnetic field (IMF) carried by the solar wind. From numerous statistical studies, it is known that the plasma circulation conforms to patterns that are characteristic of particular IMF states. Following a change in the IMF, the convection responds by reconfiguring into a pattern that is more

J. M. Ruohoniemi; S. G. Shepherd; R. A. Greenwald

2002-01-01

76

Spacelab-2 plasma depletion experiments for ionospheric and radio astronomical studies  

NASA Astrophysics Data System (ADS)

The Spacelab-2 Plasma Depletion Experiments were a series of studies to examine Shuttle-induced perturbations in the ionosphere and their application to ground-based radio astronomy. The Space Shuttle Challenger fired its orbital maneuvering subsystem engines, releasing large amounts of exhaust molecules that caused the electrons and ions in earth's upper atmosphere to chemically recombine, thereby creating so-called 'ionospheric holes'. Two burns conducted over New England produced ionospheric peak depletions ranging from 25 to 50 percent, affected the ionosphere over a 200-kilometer altitude range, and covered 1 to 2 deg of latitude. Optical emissions associated with the hole spanned an area of several hundred thousand square kilometers. A third burn was conducted over a low-frequency radio observatory in Hobart, Australia, to create an 'artificial window' for ground-based observations at frequencies normally below the natural ionospheric cutoff (penetration) frequency. The Hobart experiment succeeded in making high-resolution observations at 1.7 megahertz through the induced ionospheric hole.

Mendillo, M.; Baumgardner, J.; Allen, D. P.; Foster, J.; Holt, J.

1987-11-01

77

Spacelab-2 plasma depletion experiments for ionospheric and radio astronomical studies.  

PubMed

The Spacelab-2 Plasma Depletion Experiments were a series of studies to examine shuttle-induced perturbations in the ionosphere and their application to ground-based radio astronomy. The space shuttle Challenger fired its orbital maneuvering subsystem engines on 30 July and 5 August 1985, releasing large amounts of exhaust molecules (water, hydrogen, and carbon dioxide) that caused the electrons and ions in Earth's upper atmosphere to chemically recombine, thereby creating so-called "ionospheric holes." Two burns conducted over New England produced ionospheric peak depletions ranging from 25 to 50 percent, affected the ionosphere over a 200-kilometer altitude range, and covered 1 degrees to 2 degrees of latitude. Optical emissions associated with the hole spanned an area of several hundred thousand square kilometers. A third burn was conducted over a low-frequency radio observatory in Hobart, Australia, to create an "artificial window" for ground-based observations at frequencies normally below the natural ionospheric cutoff (penetration) frequency. The Hobart experiment succeeded in making high-resolution observations at 1.7 megahertz through the induced ionospheric hole. PMID:17744364

Mendillo, M; Baumgardner, J; Allen, D P; Foster, J; Holt, J; Ellis, G R; Klekociuk, A; Reber, G

1987-11-27

78

Convective Instability in the Plasma Couette Experiment  

Microsoft Academic Search

The emergence of flux from the tachocline and through the sun's surface is thought to occur by the magnetic buoyancy instability (Parker instability). The Plasma Couette Experiment (PCX) at U. Wisconsin-Madison presents a unique opportunity to explore this instability, as well as an instability due to compositional buoyancy, in the laboratory. In PCX, a cylindrical, axisymmetric plasma is confined in

Noam Katz; Cami Collins; Dave Weisberg; Ben Brown; John Wallace; Mike Clark; Cary Forest

2010-01-01

79

Tomographic imaging and characterization of ionospheric equatorial plasma irregularities with the Global Ultraviolet Imager  

NASA Astrophysics Data System (ADS)

This dissertation develops a technique for reconstructing multidimensional images of the electron density of the Earth's ionosphere using spectroscopic measurements obtained from the Global Ultraviolet Imager (GUVI). This work combines a novel image processing approach, models of GUVI observations as tomographic reconstruction problems, and new studies of equatorial plasma irregularities and the global F-region ionosphere. The image processing component of the research involves the development of a computationally efficient, edge-preserving regularization technique incorporating projection on convex sets (POCS) in order to solve the limited-angle tomographic image reconstruction problem. The algebraic reconstruction technique was specifically tailored to reconstruct the shapes of plasma irregularities while also recovering the altitude and longitude profile of the background ionosphere, all using data with a low signal-to-noise ratio. GUVI observation geometry is discretely modeled and a linear algebraic relationship is derived between GUVI brightness measurements and ionospheric electron density values. The specific formulation of the problem varies to accommodate the physics of different latitude regions of the ionosphere in order to allow the three-dimensional observation geometry to be cast as a two-dimensional limited-angle tomography problem. The experimental aspect explores the equatorial plasma bubble imaging capabilities of this technique and its scientific impact. Retrievals of altitude and longitude profiles allow for characterization of plasma bubbles based on their structure and depth of depletion. This information can then be used in coordinated studies of plasma bubbles with groundbased imaging systems. These coordinated studies both serve to validate the reconstructed images and to provide complementary information for a more complete understanding of plasma bubble events.

Comberiate, Joseph Michael

80

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

81

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

82

On plasma convection in Saturn's magnetosphere  

NASA Astrophysics Data System (ADS)

We use CAPS plasma data to derive particle characteristics within Saturn's inner magnetosphere. Our approach is to first develop a forward-modeling program to derive 1-dimensional (1D) isotropic plasma characteristics in Saturn's inner, equatorial magnetosphere using a novel correction for the spacecraft potential and penetrating background radiation. The advantage of this fitting routine is the simultaneous modeling of plasma data and systematic errors when operating on large data sets, which greatly reduces the computation time and accurately quantifies instrument noise. The data set consists of particle measurements from the Electron Spectrometer (ELS) and the Ion Mass Spectrometer (IMS), which are part of the Cassini Plasma Spectrometer (CAPS) instrument suite onboard the Cassini spacecraft. The data is limited to peak ion flux measurements within +/-10° magnetic latitude and 3-15 geocentric equatorial radial distance (RS). Systematic errors such as spacecraft charging and penetrating background radiation are parametrized individually in the modeling and are automatically addressed during the fitting procedure. The resulting values are in turn used as cross-calibration between IMS and ELS, where we show a significant improvement in magnetospheric electron densities and minor changes in the ion characteristics due to the error adjustments. Preliminary results show ion and electron densities in close agreement, consistent with charge neutrality throughout Saturn's inner magnetosphere and confirming the spacecraft potential to be a common influence on IMS and ELS. Comparison of derived plasma parameters with results from previous studies using CAPS data and the Radio And Plasma Wave Science (RPWS) investigation yields good agreement. Using the derived plasma characteristics we focus on the radial transport of hot electrons. We present evidence of loss-free adiabatic transport of equatorially mirroring electrons (100 eV - 10 keV) in Saturn's magnetosphere between 10-19 RS and from July 1st, 2004 to . Hot electron densities peak near 9 RS and decrease radially at a rate of 1/r3, which suggests a source in the inner magnetosphere. We also observe a decrease in electron energy at a rate of 1/r3 due to the conservation of the first adiabatic invariant, consistent with radial transport through a magnetic dipole. Data from the magnetic field instrument is used to derive the magnetic moment of hot electrons which shows a constant value of 103.4 kgm2s-2 nT-1 +/-10 between 10-19 RS, indicating a loss-free adiabatic transport with minor fluctuations. Plasma transport at Saturn can occur through flux tube interchange instabilities within the magnetosphere, where cold dense plasma is transported radially outward while hot tenuous plasma from the outer magnetosphere moves radially inward. Gradient-curvature drifts cause these hot electrons leave the injection and superimpose on the ambient cold plasma, consequently forcing it to move radially outward. This implies flux-tube interchange to be the main source for hot electrons. Hot electrons are part of the plasma analysis for which CAPS was designed, while the MIMI-LEMMS instrument measures higher energy electrons. Taking into account the penetrating background radiation, we are able to derive information for these energetic particles using our plasma instruments. We present CAPS-IMS background measurements derived from plasma data and show strong correlation with high energy particle data from MIMI-LEMMS. IMS background is generated via two main processes: 1) Collisions between the instrument walls and ambient energetic particles, which cause X-rays to trigger count signals in the instrument optics, and 2) backscatter of energetic particles in the electrostatic analyzer. We quantify these effects and use the results to identify Saturn's radiation belt peaks and nadirs, and magnetospheric regions of depleted particle fluxes, or microsignatures, which are formed through interactions with moons and ring systems. Using methods described in [119] we analyze a moon microsignatures during

Livi, Roberto

83

Modeling the low-latitude ionospheric electron density and plasma turbulence in the November 2004 storm period  

Microsoft Academic Search

The storm period of 8–12 November 2004 offers an opportunity for insight into the phenomena of low-latitude ionospheric structure during geomagnetically disturbed times because of the strength of the disturbances, the timing of the storms, and the instrumentation that was operating during the interval. We will take advantage of these factors to model the ambient ionosphere and the plasma turbulence

J. M. Retterer; Ronald Ilma; M. C. Kelley; Jorge L. Chau; C. E. Valladares; L. C. Gentile; K. Groves

2010-01-01

84

Modeling the low-latitude ionospheric electron density and plasma turbulence in the November 2004 storm period  

Microsoft Academic Search

The storm period of 8-12 November 2004 offers an opportunity for insight into the phenomena of low-latitude ionospheric structure during geomagnetically disturbed times because of the strength of the disturbances, the timing of the storms, and the instrumentation that was operating during the interval. We will take advantage of these factors to model the ambient ionosphere and the plasma turbulence

J. M. Retterer; Ronald Ilma; M. C. Kelley; Jorge L. Chau; C. E. Valladares; L. C. Gentile; K. Groves

2010-01-01

85

Handling cycle slips in GPS data during ionospheric plasma bubble events  

NASA Astrophysics Data System (ADS)

During disturbed ionospheric conditions such as the occurrence of plasma bubbles, the phase and amplitude of the electromagnetic waves transmitted by GPS satellites undergo rapid fluctuations called scintillation. When this phenomenon is observed, GPS receivers are more prone to signal tracking interruptions, which prevent continuous measurement of the total electron content (TEC) between a satellite and the receiver. In order to improve TEC monitoring, a study was conducted with the goal of reducing the effects of signal tracking interruptions by correcting for "cycle slips," an integer number of carrier wavelengths not measured by the receiver during a loss of signal lock. In this paper, we review existing cycle-slip correction methods, showing that the characteristics associated with ionospheric plasma bubbles (rapid ionospheric delay fluctuations, data gaps, increased noise, etc.) prevent reliable correction of cycle slips. Then, a reformulation of the "geometry-free" model conventionally used for ionospheric studies with GPS is presented. Geometric information is used to obtain single-frequency estimates of TEC variations during momentary L2 signal interruptions, which also provides instantaneous cycle-slip correction capabilities. The performance of this approach is assessed using data collected on Okinawa Island in Japan during a plasma bubble event that occurred on 23 March 2004. While an improvement in the continuity of TEC time series is obtained, we question the reliability of any cycle-slip correction technique when discontinuities on both GPS legacy frequencies occur simultaneously for more than a few seconds.

Banville, S.; Langley, R. B.; Saito, S.; Yoshihara, T.

2010-12-01

86

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, Växjö #12;Bo Thidé 34th EPS Plasma Physics, Warsaw, Poland, 2--7 July, 20072 Space plasma diagnostic. #12;Bo Thidé 34th EPS Plasma Physics, Warsaw, Poland, 2--7 July, 20073 Secondary radiation

87

Seasonal trends of nighttime plasma density enhancements in the topside ionosphere  

NASA Astrophysics Data System (ADS)

In situ registrations of electron density from the Langmuir probe on board Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions satellite are used to study spatial and temporal evolution of nighttime plasma density enhancements (NPDEs). The study introduces the normalized density difference index INDD in order to provide global estimates of the phenomenon. In the validation test, in situ data are compared with synthetic data set generated with the International Reference Ionosphere model. We find signatures of two most common examples of NPDEs, the Weddell Sea Anomaly (WSA) and midlatitude nighttime summer anomaly (MSNA) with proposed index, in the topside ionosphere. The study provides evidence that the occurrence of the WSA and MSNA is not limited to the local summer conditions. Analyzed annual trend of INDD and in particular spatial pattern obtained during equinoxes suggest that mechanisms governing the behavior of the equatorial ionosphere cannot be neglected in the explanation of the development of NPDEs.

Slominska, Ewa; Blecki, Jan; Lebreton, Jean-Pierre; Parrot, Michel; Slominski, Jan

2014-08-01

88

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

89

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

90

Radial convection of plasma structures in a turbulent rotating magnetized plasma column  

Microsoft Academic Search

The turbulent regime of the rotating magnetized plasma column in the Mistral device has been studied. The structures inside the turbulence move on average along a spiral trajectory. These long-lived structures are convected in the background plasma to the walls contributing to a large extent both to particle and to energy transport. Without drift induced by the curvature and the

Claudia Riccardi; Ruggero Barni; Thiery Pierre; Alexandre Escarguel; Didier Guyomarc'h

2003-01-01

91

Variations in the parameters of scattered signals and the ionosphere connected with plasma modification by high-power radio waves  

Microsoft Academic Search

We describe the results of using the incoherent scatter technique to observe time-altitude variations in regular parameters\\u000a of the ionospheric plasma and wave disturbances, which accompanied periodic modification of the near-Earth plasma by radio\\u000a waves emitted by the “Sura” facility. A distinctive feature of the experiments was that the processes in the ionosphere were\\u000a diagnosed at a distance of about

V. P. Burmaka; I. F. Domnin; V. P. Uryadov; L. F. Chernogor

2009-01-01

92

Recent and planned observations of thermal plasma in magnetosphere-ionosphere coupling using thermal plasma imaging  

NASA Astrophysics Data System (ADS)

Thermal plasma imaging (TPI) is a technique developed over the past fifteen years, beginnning with the Freja Cold Plasma Analyzer. TPI generates high-resolution, 2-D (angle/energy) representations of charged particle distribution functions in the thermal (0-20 eV) or suprathermal (0-200 eV) energy ranges. This talk will review results from a series of sub-orbital flights of TPI instruments, and will preview capabilities and studies planned for the ePOP Suprathermal Electron Imager and the Swarm Electric Field Instruments. The enhanced Polar Outflow Probe, planned for launch in 2009, will study polar ion outflow and the mechanisms that cause it, including ambipolar electric fields driven by photoelectrons and/or soft electron precipitation. The Swarm EFIs are TPI-based instruments that will measure electric fields through ion drifts during a four-year mission that will begin in 2010. These measurements combined with Swarm's precision magnetic field measurements will provide an unprecedented view of electrodynamic coupling and energy transfer between the ionosphere, thermosphere and magnetosphere.

Knudsen, David

93

Description of the mean behaviour of ionospheric plasma temperatures  

NASA Technical Reports Server (NTRS)

A status report on the empirical modeling of ionospheric electron and ion temperatures is given with special emphasis on the models used in the International Reference Ionosphere (IRI). Electron temperature models have now reached a state where reliable prediction of the mean altitudinal, latitudinal and diurnal variations is possible. These models are largely based on satellite measurements, but comparisons with incoherent scatter radar measurements have shown excellent agreement. Variations with season and magnetic and solar activity seem to be small and are not yet included consistently in these models. Similar to the electron temperature, the ion temperature shows the largest variations with altitude, latitude and local time. But due to the larger mass, these variations are smoother and more steady in the case of the ions and therefore easier to model. Nevertheless, very few ion temperature models exist. The IRI model takes advantage of the observed concurrence of the ion temperature with the neutral temperature at low altitudes and with the electron temperature at high altitudes.

Bilitza, Dieter

1987-01-01

94

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

95

Morphology of the postsunset vortex in the equatorial ionospheric plasma drift  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

96

Processes accompanying the charging of dust grains in the ionospheric plasma  

SciTech Connect

The influence of the neutral component of the dusty ionospheric plasma on the process of dust grain charging is analyzed. Microscopic ion fluxes onto a dust grain are calculated with allowance for the interaction with the neutral components of the ionospheric plasma for both negatively and positively charged dust grains. For the latter case, which takes place in the presence of intense UV or X-ray solar radiation, the electron heating caused by the photoelectric effect is also investigated. It is found that the efficiency of electron heating depends on the density of neutral particles. The altitudes at which these effects appreciably influence the charging of different types of nano- and microscale dust grains are determined. It is shown that these effects should be taken into account in describing noctilucent clouds, polar mesosphere summer echoes, and physical phenomena involving grains of meteoric origin.

Kopnin, S. I.; Morzhakova, A. A.; Popel, S. I. [Russian Academy of Sciences, Institute of Geosphere Dynamics (Russian Federation); Shukla, P. K. [Ruhr University Bochum (Germany)

2011-08-15

97

submitted to Journal of Geophysical Research 2013JA018867 Estimating the Effects of Ionospheric Plasma on Solar-Wind/Magnetosphere  

E-print Network

-ionosphere system is controlled by the amount of magnetic-field-line reconnection between the solar wind magnetic-field strength and same mass density) collisionless plasmas, the reconnection rate R is given by R in the plasmas near the reconnection site and B is the magnetic-field strength in the plasmas near

Lotko, William

98

Kinetic modeling of O(+) upflows resulting from E x B convection heating in the high-latitude F region ionosphere  

NASA Technical Reports Server (NTRS)

We report here the results of modeling work aimed at understanding the development of ionospheric O(+) field-aligned upflows that develop in response to high-latitude E x B drift induced frictional heating. The model used is a collisional semikinetic model which includes ion-neutral resonant charge exchange and polarization collisions as well as Coulomb self-collisions. It also includes the process of chemical removal of O(+) as well as all of the macroscopic forces: ambipolar electric, gravity, magnetic mirror, and centripetal. Model results show the development of several types of non-Maxwellian velocity distributions including toroids at low altitude, distributions with large heat flow in the perpendicular component at intermediate altitudes, and distributions with a separate upflowing population or upward superthermal tail at high altitudes. Whenever the convection electric field increases from a small value (less than 25 mV/m) to a large value (100-200 mV/m) in 6 min or less large upflows develop with parallel drift speeds which peak (below 1000 km) at values between 500 m/s and 2 km/s, parallel fluxes which peak between 6.0 x 10(exp 8) and 3.2 x 10(exp 9)/sq cm/s, and parallel per particle heat flows which peak between 8.0 x 10(exp -9) and 8.0 x 10(exp -8) ergs cm/s. The higher values in these ranges occur for a cooler neutral atmosphere, with a larger convection electric field that is turned on quickly. The model produces field-aligned O(+) flow speeds that are larger than those produced by a 20-moment generalized transport model but smaller then those produced by an isotropic hydrodynamic model for comparable values of the convection turn on times. The model results compare favorably with some topside satellite and radar data.

Wilson, G. R.

1994-01-01

99

2-dimensional FDTD simulations of plasma wave propagations in the ionosphere  

NASA Astrophysics Data System (ADS)

We developed a 2-dimensional FDTD simulation code which can treat wave propagations in magnetized plasma. Though we need to perform full particle simulations in order to recognize accurate characteristics of waves propagating in space plasma, FDTD simulations can be performed with much less computer resources than those necessary for full particle simulations, in memories as well as cpu times. Since space plasma is magnetized, it is necessary to incorporate the dielectric tensor with anisotropy and dispersibility in FDTD simulation code, in order to calculate the electromagnetic field in space plasma. We use PLRC method to formulization FDTD scheme to reduce numerical errors. In FDTD simulations, it is essential that how to realize an effective absorbing boundary. We developed PML absorbing boundary condition with anisotropy and dispersibility, and succeeded to realize very effective absorbind boundary. According to the rocket observations, we can receive MF radio wave above the dense ionospheric layer whose density is larger than those corresponding to cutoff frequency of MF radio wave. We consider that this is because the thickness of the ionopheric layer is smaller than the wavelength of MF radio wave, the density of ionospheric layer is not constant in the horizontal plane. We have been analyzing the characteristics of MF wave propagation in the ionospher with Full-wave method. In the Full-wave method, since the electron density profile is assumed to change in one-dimensional corrsponding to the alititude, we can only treat one-dimensional electron density profiles. In this study, therefore, we performed a series of FDTD simulations of MF wave propagations in ionospheres with several types of electron density distributions in the horizontal plane, such as electron dense cloud, sporadic layer, etc., and studied the relation between spatial scale of ionospheric layer and MF radio wavelength. In addition, we performed a FDTD simulation of MF radio wave propagations with the ionospheric layer model which is estimated by Full-wave analysis of S-310-37 sounding rocket observations. S-310-37 sonding rocket was launched at USC (Uchinoura Space Center, Kagoshima) in Jan. 2007. We are going to compare FDTD simulation results, Full-wave analysis and rocket observations, and study the influence of electron density profile on the propagation characterictics of MF radio wave in the ionosphere.

Miyake, T.; Yoshino, S.; Okada, T.; Ishisaka, K.

2007-12-01

100

Solar System Ionospheres  

NASA Astrophysics Data System (ADS)

This article reviews our understanding of the ionospheres in the solar system. It provides some basic information on the sources and sinks of the ionospheric plasma, its dynamics, the energetics and the coupling to the neutral atmosphere. Ionospheres in the solar system are reviewed and comparative ionospheric topics are discussed.

Witasse, O.; Cravens, T.; Mendillo, M.; Moses, J.; Kliore, A.; Nagy, A. F.; Breus, T.

101

Solar System Ionospheres  

Microsoft Academic Search

This article reviews our understanding of the ionospheres in the solar system. It provides some basic information on the sources\\u000a and sinks of the ionospheric plasma, its dynamics, the energetics and the coupling to the neutral atmosphere. Ionospheres\\u000a in the solar system are reviewed and comparative ionospheric topics are discussed.

O. Witasse; T. Cravens; M. Mendillo; J. Moses; A. Kliore; A. F. Nagy; T. Breus

2008-01-01

102

Solar System Ionospheres  

Microsoft Academic Search

This article reviews our understanding of the ionospheres in the solar system. It provides some basic information on the sources\\u000a and sinks of the ionospheric plasma, its dynamics, the energetics and the coupling to the neutral atmosphere. Ionospheres\\u000a in the solar system are reviewed and comparative ionospheric topics are discussed.

O. Witasse; T. Cravens; M. Mendillo; J. Moses; A. Kliore; A. F. Nagy; T. Breus

103

Solar System Ionospheres  

NASA Astrophysics Data System (ADS)

This article reviews our understanding of the ionospheres in the solar system. It provides some basic information on the sources and sinks of the ionospheric plasma, its dynamics, the energetics and the coupling to the neutral atmosphere. Ionospheres in the solar system are reviewed and comparative ionospheric topics are discussed.

Witasse, O.; Cravens, T.; Mendillo, M.; Moses, J.; Kliore, A.; Nagy, A. F.; Breus, T.

2008-08-01

104

Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill  

NASA Astrophysics Data System (ADS)

Elevation scans across geomagnetic mid latitudes by the incoherent scatter radar at Millstone Hill captured the ionospheric response to the firing of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow and the formation of an ionospheric hole during this event have been reported in an earlier paper by Mendillo et al.. The depletion (factor sim2) near the 320 km Shuttle orbital altitude persisted for sim35 min and then recovered to near normal levels, while at 265 km the density was reduced by a factor of sim6; this significant reduction in the bottomside F-region density persisted for more than 3 hours. Total electron content in the vicinity of the hole was reduced by more than a factor of 2, and an oscillation of the F-region densities with 40-min period ensued and persisted for several hours. Plasma vertical Doppler velocity varied quasi-periodically with a sim80-min period, while magnetic field variations observed on the field line through the Shuttle-burn position exhibited a similar sim80-min periodicity. An interval of magnetic field variations at hydromagnetic frequencies (sim95 s period) accompanied the ionospheric perturbations on this field line. Radar observations revealed a downward phase progression of the 40-min period density enhancements of -1.12° km-1, corresponding to a 320-km vertical wavelength. An auroral-latitude geomagnetic disturbance began near the time of the Spacelab-2 experiment and was associated with the imposition of a strong southward IMF Bz across the magnetosphere. This created an additional complication in the interpretation of the active ionospheric experiment. It cannot be determined uniquely whether the ionospheric oscillations, which followed the Spacelab-2 experiment, were related to the active experiment or were the result of a propagating ionospheric disturbance (TID) launched by the enhanced auroral activity. The most reasonable conclusion is that the ionospheric oscillations were a result of the coincident geomagnetic disturbance. The pronounced depletion of the bottomside ionosphere, however, accentuated the oscillatory behavior during the interval following the Shuttle OMS burn.

Foster, J. C.; Holt, J. M.; Lanzerotti, L. J.

2000-01-01

105

The Ionosphere of Io and the Plasma Environments of Europa, Ganymede, and Callisto  

NASA Astrophysics Data System (ADS)

The Galileo spacecraft has provided multiple opportunities for radio occultation investigations of the Galilean satellites of Jupiter: Io, Europa, Ganymede, and Callisto. There have been 12 measurements of the ionosphere of Io. They present an ionosphere controlled by its interaction with the magnetosphere of Jupiter, with a maximum electron density of 20,000 to 60,000 el./cc on the "upstream" side, with little or no ionization above 200 km, and a maximum density of 60,000 to 100,000 el./cc on the "downstream" side , with ionization extending to at least 3,000 km. On Europa, evidence was found of a much more tenuous ionosphere, with a peak density of 5,000 to 14,000 el/cc and a greater vertical extent in the downstream direction. On Ganymede, six radio occultation measurements provided inconclusive results in four instances, with only two upstream measurements suggesting an ionosphere with a maximum density of about 5,000 el./cc near the surface. This could be due to its own magnetosphere, which may be shielding its surface from Jupiter's magnetospheric plasma. The single occultation by Callisto provided only two profiles , remarkably similar to each other, with 2,000 el./cc maximum density.

Kliore, A. J.; Herrera, R. G.; Hinson, D. P.; Twicken, J. D.; Flasar, F. M.; Schinder, P. D.

1998-12-01

106

The ionosphere of Venus - Observations and their interpretation  

NASA Technical Reports Server (NTRS)

The implications of Soviet and U.S. observations of the Venus ionosphere's density, temperature, composition, motion, and magnetic structure are discussed, in view of the strong influence exerted on nearly all ionospheric parameters by the solar wind. The IMF conveys solar wind pressure to the ionosphere, compressing, accelerating, heating and removing plasma, forming the ionopause and inducing a nightward convection of plasma. Within the ionosphere, the main electron density peak is at an altitude of about 140 km on the day side, and is believed to be formed by local production and loss analogous to the earth's E region. Throughout most of the ionosphere, the nightward ion flow is primarily driven by the day-to-night pressure gradient, and electron precipitation also contributes to the nightside ionization. The lower atmosphere is dominated by O2(+), except at the lowest altitudes at night, where NO(+) and CO2(+) become significant ions.

Brace, L. H.; Taylor, H. A., Jr.; Gombosi, T. I.; Kliore, A. J.; Knudsen, W. C.; Nagy, A. F.

1983-01-01

107

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

108

Comparative studies of the plasma turbulence in the different regions of the ionosphere- discussion of the results from DEMETER satellite  

NASA Astrophysics Data System (ADS)

Plasma turbulence is a very common phenomenon in the Earth's ionosphere. There are difference sources of it, but the generally the nonlinear developing of the plasma instabilities is a main cause of its presence. In the ionosphere there are several regions with conditions favorable for the generation and developing of the plasma instabilities. The main regions in which the turbulence has been registered are: equatorial ionosphere, auroral oval, polar cusp, ionospheric trough and also regions over epicenters of the earthquakes. The turbulence is characterized as multiscale nonlinear and intermittent process. We will present results of electric field wave form analysis using wavelet and bispectral methods for selected strong earthquakes and for crossings of the polar cusp, equatorial region and ionospheric trough. All data used in our presentation were gathered by ICE experiment onboard DEMETER satellite. These methods allow to find the energy cascade being a main mechanism of the turbulence developing. Plasma turbulence can be described by the shape of the spectra, the probability distribution function and its moments- kurtosis and skewness. The main goal of our presentation is comparison of these parameters for the turbulence over seismic regions and other ionospheric sites with turbulence.

Blecki, J.; Ko?ciesza, M.; Boudjada, M.; Parrot, M.; Savin, S.; Wronowski, R.

2012-04-01

109

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

E-print Network

Convective Cell Formation in a Levitated Dipole J. Kesner Plasma Science and Fusion Center dipole may be subject to the formation of convective cells. Using a "Drift" fluid model we show and azimuthally in a closed field line system. This can lead to the formation of convective cells in closed field

110

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

111

Plasma bubbles and irregularities in the equatorial ionosphere  

Microsoft Academic Search

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

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

1977-01-01

112

Comparison of the ionospheric plasma turbulence over seismic and equatorial regions.  

NASA Astrophysics Data System (ADS)

Many strong earthquakes which are objects of interest in investigations of the changes registered in the electric field in the ELF frequency range (1 Hz - 1250 Hz) in the ionospheric plasma, occurs in the equatorial region. In order to determine, if the observed disturbances are connected with the coupling between the ground and the ionosphere in the seismic active region, it is necessary to analyse and compare plasma instability phenomena occurring in the equatorial F-region ionosphere and are known as equatorial spread F (ESF) to changes before earthquakes because their character is very similar. The aim of this paper is the analysis of changes in the electromagnetic ELF field, registered by the French micro-satellite DEMETER over epicentres of three selected strong earthquakes with magnitude bigger than 6, which took place in: Sichuan, Chile and Haiti. A comparison between those cases and changes observed by the same satellite over the equatorial region in the similar time of year is presented. The analysis of the data, was conducted with the Fourier, wavelet and bispectral methods. The last one gives answer to question, whether the changes localized with the spectral analysis are nonlinear. Further processing consists the determination of the power spectrum and its slope, which allows to determine the type of turbulence which was inducted by the three wave interaction. The last stage of the presented research, was finding the characteristic remarks of changes, by calculation of the probability density function (PDF) and calculation of its characteristic values such as kurtosis and skewness.

Kosciesza, M.; Blecki, J.; Parrot, M.; Wronowski, R.

2012-04-01

113

Radial Convection of Plasma Structures in a Turbulent Rotating Magnetized-Plasma Column  

Microsoft Academic Search

The turbulent regime of a rotating magnetized plasma column has been studied. The detection and the spatiotemporal analysis of structures by means of conditional sampling techniques is performed. Because of the overall rotation and centrifugal effects, the structures inside the turbulence move on average along a spiral trajectory leading to a net radial convection of the charged particles to the

Th. Pierre; A. Escarguel; D. Guyomarc'h; R. Barni; C. Riccardi

2004-01-01

114

Magnetosphere of Uranus: plasma sources, convection, and field configuration  

SciTech Connect

At the time of the Voyager 2 flyby of Uranus, the planetary rotational axis will be roughly antiparallel to the solar wind flow. If Uranus has a magnetic dipole moment that is approximately aligned with its spin axis, and if the heliospheric shock has not been encountered, we will have the rare opportunity to observe a ''pole-on'' magnetosphere as discussed qualitatively by Siscoe. Qualitative arguments based on analogy with Earth, Jupiter, and Saturn suggest that the magnetosphere of Uranus may lack a source of plasma adequate to produce significant internal currents, internal convection, and associated effects. In order to provide a test of this hypothesis with the forthcoming Voyager measurements, we have constructed a class of approximately self-consistent quantitative magnetohydrostatic equilibrium configurations for a pole-on magnetosphere with variable plasma pressure parameters. Given a few simplifying assumptions, the geometries of the magnetic field and of the tail current sheet can be computed for a given distribution of trapped plasma pressure. The configurations have a single funnel-shaped polar cusp that points directly into the solar wind and a cylindrical tail plasma sheet whose currents close within the tail rather than on the tail magnetopause, and whose length depends on the rate of decrease of thermal plasma pressure down the tail. Interconnection between magnetospheric and interplanetary fields results in a highly asymmetric tail-field configuration. These features were predicted qualtitatively by Siscoe; the quantitative models presented here may be useful in the interpretation of Voyager encounter results.

Voigt, G.; Hill, T.W.; Dessler, A.J.

1983-03-01

115

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

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

116

Galileo radio occultation measurements of lo's ionosphere and plasma wake  

Microsoft Academic Search

Six radio occultation experiments were conducted with the Galileo orbiter in 1997, yielding detailed measurements of the distribution and motion of plasma surrounding Io. This distribution has two components. One is highly asymmetric, consisting of a wake or tail that appears only on the downstream side and extends to distances as large as 10 Io radii. The other resembles a

D. P. Hinson; A. J. Kliore; F. M. Flasar; J. D. Twicken; P. J. Schinder; R. G. Herrera

1998-01-01

117

Physics of planetary ionospheres  

NASA Technical Reports Server (NTRS)

The fundamental physical and chemical processes in an idealized planetary ionosphere are considered as a general abstraction, with actual planetary ionospheres representing special cases. After describing the structure of the neutral atmospheres (the barosphere, the thermosphere, and the exosphere) and noting the principal ionizing radiations responsible for the formation of planetary ionospheres, a detailed study is made of the thermal structure of these ionospheres and of the chemical processes and plasma-transport processes occurring in them. The features of equilibrium and realistic models of planetary ionospheres are discussed, and an attempt is made to determine the extent of these ionospheres. Considering the ionosphere as a plasma, a plasma kinetic approach is developed for determining the effects of interactions between individual particles and waves in this plasma. The use of remote-sensing radio techniques and direct measurement or in situ techniques is discussed. Finally, the observed properties of the ionospheres of the Earth, Mars, Venus, and Jupiter are reviewed.

Bauer, S. J.

1973-01-01

118

Possible role of ionospheric oxygen in the initiation and development of plasma sheet instabilities  

SciTech Connect

We relate measurements made during substorm growth and expansion to available plasma compositional observations and propose that asymmetries in the distribution of enhanced densities of O/sup +/ (of ionospheric origin) may define regions of the plasma sheet in which tearing mode growth rates are increased and the instability threshold is lowered. We make qualitative estimates of the growth rates of the linear ion tearing mode using statistical models of the dusk-dawn and earthward-tailward distributions of O/sup +/. The theoretical results predict maximum ion tearing growth rate in the range X/sub GSM/ = -10 to -15 R/sub E/ and Y/sub GSM/approx.5 R/sub E/. These values are in reasonable accord with substorm observations since many asymmetries in particle and field phenomena associated with substorms favor the interpretation that substorm onset occurs in the dusk sector of the near-earth plasma sheet. Present results therefore suggest that substorm initiation and development may be closely related to distribution patterns of ionospheric ions.

Baker, D.N.; Hones, E.W. Jr.; Young, D.T.; Birn, J.

1982-12-01

119

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

SciTech Connect

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

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

2011-07-15

120

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

PubMed

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

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

2011-07-01

121

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

122

The Equatorial Ionosphere During Solar Minimum -- C/NOFS Observations of Deep Plasma Depletions at Sunrise  

NASA Astrophysics Data System (ADS)

The Communication/Navigation Forecasting System (C/NOFS) satellite was launched in April 2008 into an equatorial orbit at an altitude between 400 and 850 km, to study the equatorial ionosphere as well as irregularities within it. The satellite sensors measure the following parameters: ambient and fluctuating ion densities; ion and electron temperatures; neutral winds, AC and DC electric and magnetic fields. C/NOFS is circling the Earth at a time when the solar cycle is the lowest it has been since the beginning of the space age. In this talk, we stress the findings that are unique to solar minimum conditions. The plasma density is the smallest seen in the past half century. The pre-reversal enhancement in the upward plasma drift, which is responsible for early evening irregularities, is rarely seen. Instead, plasma irregularities form mostly after midnight. An unexpected feature in the data concerns deep plasma depletions observed at sunrise. They are seen at all satellite altitudes and associated with ionospheric irregularities. Dawn depletions are more frequent in the America-Africa sector and in the Indonesia sector. Dawn depletions are also observed in other data sets, in particular in data from DMSP morning passes, and the CHAMP satellite. This fact confirms that they are real and not an artifact of the plasma instrument. It also allows measuring the N-S extent of the dawn depletions - we find that they are typically 50 x 14 degrees in the N-S and E-W directions respectively, but they can be much wider in longitude. We postulate that they are caused by upward plasma drifts, which are seen in the C/NOFS and ground-based data.

de La Beaujardiere, O.; Roddy, P.; Retterer, J.; Su, Y.; Hunton, D.; Kelley, M.; Pfaff, R.

2009-05-01

123

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

124

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

125

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

126

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

127

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

128

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

129

Erosion/redeposition analysis of the ITER first wall with convective and non-convective plasma transport  

NASA Astrophysics Data System (ADS)

Sputtering erosion/redeposition is analyzed for IAEA [Report GA10FDR1-01-07-13 (2001)] plasma facing components, with scrape-off layer (SOL) plasma convective radial transport and nonconvective (diffusion-only) transport. The analysis uses the UEDGE code [T .D. Rognlien et al., J. Nucl. Mater. 196, 347 (1992)] and DEGAS code [D. P. Stotler et al., Contrib. Plasma Phys. 40, 221 (2000) ] to compute plasma SOL profiles and ion and neutral fluxes to the wall, TRIM-SP code [J. P. Biersack, W. Eckstein, J. Appl. Phys. A34, 73 (1984)] to compute sputter yields, and the REDEP/WBC code package [J. N. Brooks, Fusion Eng. Des. 60, 515 (2002)] for three-dimensional kinetic modeling of sputtered particle transport. Convective transport is modeled for the background plasma by a radially varying outward-flow component of the fluid velocity, and for the impurity ions by three models designed to bracket existing models/data. Results are reported here for the first wall with the reference beryllium coating and an alternative tungsten coating. The analysis shows: (1) sputtering erosion for convective flow is 20-40 times higher than for diffusion-only but acceptably low (˜0.3nm/s) for beryllium, and very low (˜0.002nm/s) for tungsten; (2) plasma contamination by wall sputtering, with convective flow, is of order 1% for beryllium and negligible for tungsten; (3) wall-to-divertor beryllium transport may be significant (˜10%-60% of the sputtered Be current); (4) tritium co-deposition in redeposited beryllium may be high (˜1-6gT/400s pulse).

Brooks, J. N.; Allain, J. P.; Rognlien, T. D.

2006-12-01

130

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

131

The influence of artificial electron heating on plasma irregularities in the lower ionosphere  

NASA Astrophysics Data System (ADS)

It is known small-scale ionospheric irregularities below the homopause level are generated by the neutral air turbulence. Usually an approximation of isothermality Te = Ti = Tn is valid for the lower ionosphere, especially, at middle latitudes. However, the approximation may be broken due to electron heating by powerful radio waves. In the report we consider theoretically reaction of ionospheric irregularities created by the neutral turbulence on the increasing of electron temperature Te due to the radio wave action. For this aim, expressions for the irregularity spectrum, the mean-square level of the plasma density fluctuations, and the radar backscatter cross-section per unit volume have been obtained. Using the expressions we have calculated the spectral form, the rms fluctuation level, and the cross-section ? for the case of the mid-latitude ionosphere at an altitude near 100 km when the ratio of the electron to ion temperature Te /Ti increased from 1 to 10. The spectrum has corresponded to the inertial range of turbulence, the rms level has been estimated for irregularity length-scales smaller than 500 m, and ? has been evaluated for the diagnostic radar frequencies from 5 to 50 MHz and the vertical direction of antenna beam. It was shown that an increase in Te produces a decrease in both the fluctuation level and the backscatter cross-section. In our calculations this level reduced from 6.2 to 4.8 %; the cross-section ? from 1.28×10-8 to 9.06×10-9 m-1 at 5 MHz and from 1.25×10-11 to 8.93×10-12 m-1 at 50 MHz. The rise in Te has also resulted in an increase in the spectral slope (for the approximation of spectrum by a power law k -p , the index p took values from 1.62 to 2.34). These changes are explained by a decrease in the cut-off wavenumber in the irregularity spectrum resulted from an increase in the ambipolar diffusivity due to the rise in Te .

Kyzyurov, Yurij; Chernogor, Leonid F.

132

The flow of plasma in the solar terrestrial environment  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

133

Traveling ionospheric disturbances generated due to periodic plasma heating by high-power high-frequency radiation  

NASA Astrophysics Data System (ADS)

The results of observations of variations in the Doppler-frequency shift of electromagnetic radiation of decameter waves reflected from the ionosphere during the plasma modification by highpower radio-frequency radiation from the "Sura" facility and in reference days are presented. The distance from the facility to the diagnostic tools (Doppler radar) was about 1000 km. The traveling ionospheric disturbances corresponding to a delay time of about 50 min with respect to the time of switching high-power periodic radiation and a propagation velocity of 300-400 m/s were observed. The relative amplitude of the electron-density perturbations was 1-4 %, while their oscillation period amounted to tens of minutes. The parameters of the traveling ionospheric disturbances significantly depended on the "Sura" facility radiation mode.

Chernogor, L. F.; Frolov, V. L.

2012-06-01

134

Calculation of ionospheric plasma density irregularities parameters by using EISCAT measurements for strong scintillation modelling  

NASA Astrophysics Data System (ADS)

Ionospheric plasma density irregularities may cause rapid fluctuations in the intensity and phase of radio waves propagating through. Usually, scintillation events are modelled in the diffractive scattering approach which is valid for weak scattering conditions. Some mathematical tricks help then in reproducing high levels of scintillation, lacking of full physical meaning. Strong scintillation events are better modelled in the refractive scattering approach, which includes weak scattering conditions. A few parameters (e.g., spatial correlation length and drift velocity) are of key importance in understanding which approach may be correct. Last year, two EISCAT measurement campaigns have been set up in the framework of the Trans-National Access programme, in order to infer and calculate all those parameters useful for numerical modelling of scintillation events. The radar measurement results are compared with transionospheric radio signals at VHF, UHF, and L band in order to understand the feasibility and appropriateness of the two approaches.

Forte, Biagio; Häggström, Ingemar; Turunen, Esa

2010-05-01

135

Rocket-borne particle, field, and plasma observations in the cleft region. [ionospheric sounding  

NASA Technical Reports Server (NTRS)

Results are reported for comprehensive observations of magnetic and electric fields together with ambient and suprathermal plasmas above the dayside auroral oval with rocket-borne instrumentation which penetrated the cleft region. Measurements were also obtained equatorward and poleward of the cleft. Convection velocities as inferred from electric-field measurements were generally toward noon equatorward of the cleft and were antisunward over the polar cap. Observations of electron temperatures, electric fields, and low-frequency electrostatic noise provide strong evidence of a plasma instability (Farley-Buneman) in the E-layer associated with the appearance of the 'slant E condition' identified in ground-acquired ionograms. The positions of these measurements relative to that of the cleft were firmly established via the determination of the plasma environment with an electrostatic analyzer.

Ungstrup, E.; Bahnsen, A.; Olesen, J. K.; Primdahl, F.; Spangslev, F.; Heikkila, W. J.; Klumpar, D. M.; Winningham, J. D.; Fahleson, U.; Falthammar, C.-G.

1975-01-01

136

Irregularities in ionospheric plasma clouds: Their evolution and effect on radio communication  

Microsoft Academic Search

Both satellite radio communications, which travel through the Earth's ionosphere, and high frequency (HF) sky wave circuits, which use the ionosphere as a refracting medium, can be strongly affected by radio wave scintillation. High altitude nuclear explosions cause scintillation (by strongly disturbing the ionosphere) and thus severely degrade satellite radio communications over a large region. Since further atmospheric nuclear tests

J. F. Vesecky; J. W. Chamberlain; J. M. Cornwall; D. A. Hammer; F. W. Perkins

1980-01-01

137

Irregularities in ionospheric plasma clouds: their evolution and effect on radio communication. Technical report  

Microsoft Academic Search

Both satellite radio communications, which travel through the Earth's ionosphere, and high frequency (HF) sky wave circuits, which use the ionosphere as a refracting medium, can be strongly affected by radio wave scintillation. High altitude nuclear explosions cause scintillation (by strongly disturbing the ionosphere) and thus severely degrade satellite radio communications over a large region. Since further atmospheric nuclear tests

J. F. Vesecky; J. W. Chamberlain; J. M. Cornwall; D. A. Hammer; F. W. Perkins

1980-01-01

138

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

Microsoft Academic Search

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

J. M. McCanney

2009-01-01

139

Radial convection of plasma structures in a turbulent rotating magnetized-plasma column.  

PubMed

The turbulent regime of a rotating magnetized plasma column has been studied. The detection and the spatiotemporal analysis of structures by means of conditional sampling techniques is performed. Because of the overall rotation and centrifugal effects, the structures inside the turbulence move on average along a spiral trajectory leading to a net radial convection of the charged particles to the walls. The development of a poloidal electric field inside the structures has been measured. It leads to the observed outwards radial E x B drift in agreement with the expectations of recent theoretical works. PMID:14995247

Pierre, Th; Escarguel, A; Guyomarc'h, D; Barni, R; Riccardi, C

2004-02-13

140

Cold streams of ionospheric oxygen in the plasma sheet during the CDAW-6 event of March 22, 1979  

NASA Technical Reports Server (NTRS)

During magnetospheric substorm events, the plasma and ion composition experiments in the ISEE-1 and 2 satellites detected cold ionospheric O+ streams, moving tailwards in the near Earth magnetotail. Flow is parallel to the magnetic field lines, with drift velocity in agreement with the electric field topology obtained by mapping the model ionospheric field along the magnetic field lines. Fluctuations of the flow velocity of the streams can be related to magnetotail movements. Oscillations of the flow direction and speed with periods ranging from 5 to 10 min that suggest the presence of waves are observed. The streams are observed at all distances between 15 and 6 Re from the Earth. When averaged over 360 deg, the streams show up as a low energy peak, superimposed on the distribution of isotropic plasma sheet ions. This double-peak structure of the energy spectrum seems typical of the disturbed plasma sheet.

Orsini, S.; Amata, E.; Candidi, M.; Balsiger, H.; Stokholm, M.; Huang, C. Y.; Lennartsson, W.; Lindqvist, P. A.

1983-01-01

141

Electron velocity distributions and plasma waves associated with the injection of an electron beam into the ionosphere  

NASA Astrophysics Data System (ADS)

An electron beam was injected into earth's ionosphere on August 1, 1985, during the flight of the Space Shuttle Challenger as part of the objectives of the Spacelab 2 mission. In the wake of the Space Shuttle a magnetically aligned sheet of electrons returning from the direction of propagation of the beam was detected with the free-flying Plasma Diagnostics Package. The thickness of this sheet of returning electrons was about 20 m. Large intensifications of broadband electrostatic noise were also observed within this sheet of electrons. A numerical simulation of the interaction of the electron beam with the ambient ionospheric plasmas is employed to show that the electron beam excites electron plasma oscillations and that it is possible for the ion acoustic instability to provide a returning flux of hot electrons by means of quasi-linear diffusion.

Frank, L. A.; Paterson, W. R.; Kurth, W. S.; Ashour-Abdalla, M.; Schriver, D.

1989-06-01

142

Electron velocity distributions and plasma waves associated with the injection of an electron beam into the ionosphere  

SciTech Connect

An electron beam was injected into Earth's ionosphere on August 1, 1985, the flight of the space shuttle /ital Challenger/ as part of the objectives of the Spacelab 2 mission. In the wake of the space shuttle a magnetically aligned sheet of electrons returning from the direction of propagation of the beam was detected with the free-flying plasma Diagnostics Package. The thickness of this sheet of returning electrons was about 20 m. Large intensifications of broadband electrostatic noise were also observed within this sheet of electrons. A numerical simulation of the interaction of the electron beam with the ambient ionospheric plasmas is employed to show that the electron beam excites electron plasma oscillations and that it is possible for the ion ascoustic instability to provide a returning flux of hot electorns by means of quasi-linear diffusion. /copyright/ American Geophysical Union 1989

Frank, L. A.; Paterson, W. R.; Ashour-Abdalla, M.; Schriver, D.; Kurth, W. S.; Gurnett, D. A.

1989-06-01

143

Nonlinear evolution of modified two-stream instability above ionosphere of Titan: Comparison with the data of the Cassini Plasma Spectrometer  

NASA Astrophysics Data System (ADS)

The ionosphere of Titan, moon of Saturn, is directly exposed to the streaming plasma either of magnetospheric or solar wind origin. A turbulent interaction region is formed, called here flowside plasma mantle, where both cold ionospheric and hot streaming plasma are present at comparable densities. Within the framework of a one-dimensional electromagnetic hybrid simulation using realistic electron mass we have shown that significant wave activity may be generated because of a modified two-stream instability (MTSI). Having its free energy in the relative drift between the streaming ion flow and the ionospheric ions MTSI is very effective in generating "anomalous viscosity" type interaction leading to significant bulk velocity loss of the proton component of the external plasma flow and turbulent heating of the ionospheric ions. The stochastic energy transfer from the streaming plasma to the ionospheric ions may also increase the tailward planetary ion escape by collective pickup mechanism enhancing the rate of erosion of the atmosphere of Titan. We predict significant wave activity within the characteristic frequency range of about 1-10 Hz and at saturated wave electric field levels of about 5-25 mV/m. Similarly, according to our model calculations superthermal charged particles of ionospheric origin with kinetic energies of about few tens of eV are expected to be detectable by the charged particle analyzers onboard of Cassini spacecraft close to the upper edge of Titan's ionosphere.

Dóbé, ZoltáN.; Szego, Karoly; Quest, Kevin B.; Shapiro, Vitali D.; Hartle, R. E.; Sittler, E. C.

2007-03-01

144

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

145

Mechanisms of Ionospheric Mass Ejection  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

146

Investigating Solar Wind-Magnetosphere-Ionosphere Coupling with SuperDARN and AMPERE  

NASA Astrophysics Data System (ADS)

The dynamics of the Earth's plasma environment are driven by coupling between the solar wind, with its embedded interplanetary magnetic field, and the magnetosphere through magnetic reconnection occurring at the magnetopause. Terrestrial magnetic field lines which are connected to interplanetary space in this way are subsequently released by magnetic reconnection occurring in the magnetotail. These two processes lead to increases and decreases in the proportion of the terrestrial flux that is open, as observed in changes in the latitude of the auroral zones. A circulation of plasma and magnetic flux is effected, the Dungey cycle, with a sympathetic plasma convection signature in the ionosphere. In this talk we review recent advances of our understanding of the coupling process, provided by measurements of ionospheric convection with the Super Dual Auroral Radar Network (SuperDARN) and the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) which measures the coupling currents that transfer stress from the magnetosphere into the ionosphere.

Milan, S. E.; Coxon, J.; Imber, S. M.; Clausen, L.; Korth, H.; Anderson, B. J.

2013-12-01

147

Microsatellite missions to conduct midlatitude studies of equatorial ionospheric plasma bubbles  

NASA Astrophysics Data System (ADS)

Two missions presently under development by the United States Air Force Academy (USAFA), FalconSAT-2 and FalconSAT-3, include mission scientific objectives targeting the study of ionospheric F region plasma density depletions and topside bubbles associated with the so-called Equatorial Spread F (ESF) phenomena. The Miniature Electrostatic Analyzer (MESA), a USAFA-designed patch sensor that measures differential energy fluxes of electrons from 0.05 to 13 eV in six channels, is the primary experiment aboard FalconSAT-2, a 25-kg microsatellite intended for launch into an International Space Station (ISS) orbit via the Space Shuttle. Because the orbit will be approximately 360 km in altitude and of 52° inclination, FalconSAT-2 observations will complement those of low latitude missions (e.g., C/NOFS) and polar latitude, higher altitude missions (e.g., DMSP). Realistic internal magnetic field models demonstrate that field lines with apex heights of 1500 km (representing the upper altitude limit of equatorial plasma bubbles) may intersect the orbit plane at dip latitudes greater than 35°. Thus, FalconSAT-2 will be able to observe plasma depletions that have propagated poleward along the field lines and lower in altitude, depletions that may not be observed with the high altitude DMSP and the low latitude C/NOFS. Additionally, there may be opportunities for FalconSAT-2 to make simultaneous multipoint in situ measurements of large-scale plasma bubbles with other low altitude satellites, such as C/NOFS and DMSP. We will present a statistical analysis of the probability of making such measurements using nominal orbital parameters of the relevant spacecraft. Finally, a description of the FalconSAT-3 follow-on mission, including scientific objectives associated with seeking kinetic effects, is presented.

Krause, L. Habash; Enloe, C. L.; Haaland, R. K.; Golando, P.

148

A simulation study of radial expansion of an electron beam injected into an ionospheric plasma  

NASA Technical Reports Server (NTRS)

Injections of nonrelativistic electron beams from a finite equipotential conductor into an ionospheric plasma have been simulated using a two-dimensional electrostatic particle code. The purpose of the study is to survey the simulation parameters for understanding the dependence of beam radius on physical variables. The conductor is charged to a high potential when the background plasma density is less than the beam density. Beam electrons attracted by the charged conductor are decelerated to zero velocity near the stagnation point, which is at a few Debye lengths from the conductor. The simulations suggest that the beam electrons at the stagnation point receive a large transverse kick and the beam expands radially thereafter. The buildup of beam electrons at the stagnation point produces a large electrostatic force responsible for the transverse kick. However, for the weak charging cases where the background plasma density is larger than the beam density, the radial expansion mechanism is different; the beam plasma instability is found to be responsible for the radial expansion. The simulations show that the electron beam radius for high spacecraft charging cases is of the order of the beam gyroradius, defined as the beam velocity divided by the gyrofrequency. In the weak charging cases, the beam radius is only a fraction of the beam gyroradius. The parameter survey indicates that the beam radius increases with beam density and decreases with magnetic field and beam velocity. The beam radius normalized by the beam gyroradius is found to scale according to the ratio of the beam electron Debye length to the ambient electron Debye length. The parameter dependence deduced would be useful for interpreting the beam radius and beam density of electron beam injection experiments conducted from rockets and the space shuttle.

Koga, J.; Lin, C. S.

1994-01-01

149

Recovery of the Nonmonotonic Altitude Profile of the Plasma Frequency Based on the Ionospheric Oblique Sounding Data  

NASA Astrophysics Data System (ADS)

We propose a method and an algorithm for recovery of the nonmonotonic altitude profile of the plasma frequency using the model data on oblique sounding of a spherically layered isotropic ionosphere in the piecewise-quasiparabolic approximation of the altitude profile of the electron number density. The algorithm has been tested with a fairly complex ionosphere model allowing for the E, F1, and F2 layers and the E-F1 interlayer valley. This method was used to recover the effective altitude profile of the plasma frequency at the midpoints of the Khabarovsk-Tory, Magadan-Tory, Norilsk-Tory, and Usolie-Tory paths from the experimental ionograms having a gap in the single-hop mode traces.

Mikhailov, S. Ya.; Grozov, V. P.

2013-12-01

150

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

151

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.; Gallagher, D. L.

1998-01-01

152

Multiscale modeling and nested simulations of three-dimensional ionospheric plasmas: Rayleigh-Taylor turbulence and nonequilibrium layer dynamics at fine scales  

NASA Astrophysics Data System (ADS)

Multiscale modeling and high resolution three-dimensional simulations of nonequilibrium ionospheric dynamics are major frontiers in the field of space sciences. The latest developments in fast computational algorithms and novel numerical methods have advanced reliable forecasting of ionospheric environments at fine scales. These new capabilities include improved physics-based predictive modeling, nesting and implicit relaxation techniques that are designed to integrate models of disparate scales. A range of scales, from mesoscale to ionospheric microscale, are included in a 3D modeling framework. Analyses and simulations of primary and secondary Rayleigh-Taylor instabilities in the equatorial spread F (ESF), the response of the plasma density to the neutral turbulent dynamics, and wave breaking in the lower region of the ionosphere and nonequilibrium layer dynamics at fine scales are presented for coupled systems (ions, electrons and neutral winds), thus enabling studies of mesoscale/microscale dynamics for a range of altitudes that encompass the ionospheric E and F layers. We examine the organizing mixing patterns for plasma flows, which occur due to polarized gravity wave excitations in the neutral field, using Lagrangian coherent structures (LCS). LCS objectively depict the flow topology and the extracted scintillation-producing irregularities that indicate a generation of ionospheric density gradients, due to the accumulation of plasma. The scintillation effects in propagation, through strongly inhomogeneous ionospheric media, are induced by trapping electromagnetic (EM) waves in parabolic cavities, which are created by the refractive index gradients along the propagation paths.

Mahalov, Alex

2014-09-01

153

Convection in the magnetotail  

NASA Astrophysics Data System (ADS)

It is well known that the Earth's magnetosphere is permeated by a large-scale electric field, E, which in its turn produces a global flow pattern known as magnetospheric convection, with velocity u = (E × B)/B2 . Convection is the key to understanding the global features of the magnetosphere, for instance the large-scale flow of electric currents along magnetic field lines (“Birkeland currents”) into and out of the polar ionosphere.A successful theory of convection in the inner magnetosphere was formulated about 20 years ago. That, however, explains only part of the puzzle, because the inner magnetosphere receives its E from more distant regions, mainly the magnetotail and its boundary layers, where convection is still poorly understood. One problem has been the Erickson-Wolf effect [Erickson and Wolf, 1980; Hau et al., 1989] by which convection rapidly deforms the tail until a reconnection crisis is likely. Another problem was the observational uncertainty about the polytropic (or “adiabatic”) exponent ? of the gas law expected to hold in the plasma sheet [Zhu, 1990; Baumjohann and Paschmann, 1989; Huang et al., 1989]. MHD simulations appear to be of limited use, because convection theory in the inner magnetosphere goes beyond MHD and depends on actualparticle motion. In the weak fields of the magnetotail, these may involve not only guiding center drifts but also nonadiabatic motions [e.g., Büchner and Zelenyi, 1989] and finite-gyroradius effects [Macmahon, 1965; Stasiewicz, 1987].

Stern, David

154

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

155

Equilibrium and convective stability of a plasma with interlinked toroidal and weak poloidal magnetic fields  

NASA Astrophysics Data System (ADS)

This study is related to the physics of a snowflake divertor [1]. One of its features is a large size of the zone of a very weak poloidal magnetic field in the divertor area. In this zone, the poloidal plasma beta (defined as a ratio of the plasma pressure to the pressure of a poloidal magnetic field) significantly exceeds unity. This brings up some interesting new features to the equilibrium and convective stability of the divertor plasma. It has recently been suggested [2] that convective instability can spread the heat over a larger area than normally assumed and ``activate'' all four divertor legs of a snowflake divertor, thereby significantly reducing the divertor heat load, especially during the ELM events. A quantitative analysis of the convective instability and/or loss of equilibrium at high poloidal betas will be presented and related to the heat flux reduction for a simplified geometry. Experimentally detectable signatures of plasma convection in the divertor zone will be considered. Work performed for U.S. DoE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344[4pt] [1] D.D. Ryutov, Phys. Plas., 14, 064502, 2007;[0pt] [2] D.D. Ryutov et al., Contrib. Plasma Phys., to be published, 2012.

Ryutov, Dmitri

2012-03-01

156

Microsatellite missions to conduct midlatitude studies of equatorial ionospheric plasma bubbles  

NASA Astrophysics Data System (ADS)

Two missions presently under development by the United States Air Force Academy (USAFA), FalconSAT-2 and FalconSAT-3, include mission scientific objectives targeting the study of ionospheric F region plasma density depletions and topside bubbles associated with the so-called Equatorial Spread F (ESF) phenomena. The Miniature Electrostatic Analyzer (MESA), a USAFA-designed patch sensor that measures differential energy fluxes of electrons from 0.1 eV to 13 eV in six channels, is the primary sensor aboard FalconSAT-2, a 25 kg microsatellite manifested for launch into an International Space Station (ISS) orbit via the Space Shuttle in January 2003. Because the orbit is approximately 360 km in altitude and of 52 degrees inclination, FalconSAT-2 observations will complement those of low latitude missions ( .g., C/NOFS) and high latitude, high altitude missions (e.g.,e DMSP). It is true that a 52 degree orbit appears rather high in inclination for study of ESF phenomena. However, realistic internal magnetic field models demonstrate that field lines with apex heights of 1500 km (representing the upper altitude limit of equatorial plasma bubbles) may intersect the orbit plane at dip latitudes greater than 35 degrees. Thus, FalconSAT-2 will be able to observe plasma depletions that have propagated poleward along the field lines and lower in altitude, depletions that may not be observed with the high altitude DMSP and the low latitude C/NOFS. Additionally, there may be opportunities for FalconSAT-2 to make simultaneous multipoint in situ measurements of large-scale plasma bubbles with other low altitude satellites, such as C/NOFS and DMSP. We will present a statistical analysis of the probability of making such measurements using nominal orbital parameters of the relevant spacecraft. Finally, a brief description of the FalconSAT-3 follow-on mission, including scientific objectives associated with seeking kinetic effects, will be included in the paper.

Habash Krause, L.; Haaland, R.; Enloe, C.; Golando, P.

157

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

158

Dominance of convective heat transport in the core of TFTR (Tokamak Fusion Test Reactor) supershot plasmas  

SciTech Connect

Using perturbations in electron density and temperature induced by small Helium gas puffs in TFTR (Tokamak Fusion Test Reactor) the dominance of convective heat transport in the core (r/a < 0.4) of supershot plasmas has been demonstrated in a new way. The TRANSP transport code was used to calculate the time-dependent particle and heat fluxes. Perturbations in the calculated convective and total electron heat fluxes were compared. They demonstrate that the conductive component decreases moving into the supershot core, and the convective component dominates in the supershot core. These results suggest a different transport drive in the supershot core compared to that in the rest of the supershot plasma.

Kissick, M.W.; Efthimion, P.C.; Mansfield, D.K.; Callen, J.D.; Bush, C.E.; Park, H.K.; Schivell, J.; Synakowski, E.J.; Taylor, G.

1993-08-01

159

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

160

Coupling Processes in the Equatorial Spread F\\/Plasma Bubble Irregularity Development  

Microsoft Academic Search

\\u000a The plasma convection pattern of the evening sector equatorial ionosphere sets the condition for the plasma structuring through\\u000a instability processes leading to the Equatorial Spread F (ESF)\\/plasma bubble irregularity development and evolution. Vertical\\u000a coupling through upward propagating atmospheric waves controls\\/modifies the ionosphere-thermosphere interactive processes\\u000a that eventually lead to the irregularity development. Instabilities grow by the Rayleigh-Taylor mechanism at the bottom

Mangalathayil Ali Abdu; E. Alam Kherani

161

The perturbation characteristics in plasma parameters in ionosphere before strong earthquakes  

NASA Astrophysics Data System (ADS)

Based on the data observed by DEMETER satellite, the perturbation characteristics of plasma parameters were analyzed and summarized, such as Ni(O+), Ne and so on. Two cases were presented as examples, which are Yushu M7.1 earthquake in China on April 13 2010 and Tanga M7.9 earthquake on May 3 2006. Around Yushu earthquake, more than seven-month data were selected since Oct. 2009 in a distance of 2000km to the epicenter. Long time comparison over a certain region revealed that the Ni(O+) began to increase in Feb. 2010, two months before this event, and the maximum oxygen ion density occurred on April 13, 20 hours before the earthquake with the amplitude of more than 100% relative to the normal peak values at the south of this seismic region. Before and after the earthquake during more than 7 months, the peak values of Ni(O+) had never been so large in quiet magnetic conditions. As for the Ms7.9 Tonga Islands earthquake, perturbations of plasma parameters above epicenter were detected six days, two days, one day before and two days after it. The variation feature of O+ density was more obvious than that of H+ and He+ density. Compared with the 16-day revisiting orbits in 2 years of the half orbit just one day before the earthquake, O+ density increased 20% more at the orbit closest to the epicenter than the other orbits in the same day, and it increased nearly an order of magnitude referred to the mean of O+ density in May from 2006 to 2008 by taking account of the seasonal variations in it. In addition, electron density detected simultaneously to increase with O+ density onboard DEMETER at the above-mentioned revisiting orbits. Furthermore, the statistic analysis was carried out on the earthquakes with magnitude larger than 6.0 during Jan. 2006 to Apr. 2010 in China and a few earthquakes with M?7.0 in the world. It was found that perturbations in plasma parameters occurred before 15 cases in all 29 cases. The ionospheric disturbances were detected 1-7 days before these strong earthquakes and they were exhibited both at the west or the east to the epicenter, but always turned to the equator. Finally, the enhancement phenomena of electron and ion density before earthquakes and its formation mechanism were discussed based on our study results.

Zhang, X.; Ouyang, X.; Liu, J.; Shen, X.

2012-04-01

162

Generation of mesoscale convective structures in tokamak edge plasma  

SciTech Connect

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

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

2007-10-15

163

Assimilative Modeling of MidLatitude Ionospheric Plasma Plumes during the October 2003 Storm  

Microsoft Academic Search

A significant daytime ionospheric total electron content (TEC) enhancement was observed at middle latitudes by the ground-based and space-borne GPS receivers during the geomagnetic storm on October 30, 2003. This TEC enhancement has been identified as the storm enhanced density (SED). To investigate ionospheric disturbances associated with the SED, GPS data collected from 200 ground stations and two low-Earth-orbiters (CHAMP

X. Pi; A. J. Mannucci; T. F. Runge; B. A. Iijima; B. D. Wilson; A. Komjathy; V. Akopian

2007-01-01

164

Electric fields and electrostatic potentials in the high latitude ionosphere  

NASA Technical Reports Server (NTRS)

Recent interpretive studies of electric field-driven ionospheric plasma convection data from the AE-C satellite are described, where the instruments employed include an ion drift meter and an ion-retarding potential analyzer. Electrostatic potential curves are derived from ion drift velocity measurements for high-latitude segments of the satellite's orbit. The potential curves are shown to be useful in determining the character of the global electrostatic potential pattern, with emphasis on the separation of convective cells. Results are given for six orbits, with attention to the mid-day auroral region.

Banks, P. M.; Saint Maurice, J.-P.; Heelis, R. A.; Hanson, W. B.

1981-01-01

165

Current leakage for low altitude satellites - Modeling applications. [simulation of high voltage solar cell array in ionospheric plasma environment  

NASA Technical Reports Server (NTRS)

To simulate the behavior of a high voltage solar cell array in the ionospheric plasma environment, the large (90 ft x 55 ft diameter) vacuum chamber was used to measure the high-voltage plasma interactions of a 3 ft x 30 ft conductive panel. The chamber was filled with Nitrogen and Argon plasma at electron densities of up to 1,000,000 per cu cm. Measurements of current flow to the plasma were made in three configurations: (a) with one end of the panel grounded, (b) with the whole panel floating while a high bias was applied between the ends of the panel, and (c) with the whole panel at high negative voltage with respect to the chamber walls. The results indicate that a simple model with a constant panel conductivity and plasma resistance can adequately describe the voltage distribution along the panel and the plasma current flow. As expected, when a high potential difference is applied to the panel ends more than 95% of the panel floats negative with respect to the plasma.

Konradi, A.; Mccoy, J. E.; Garriott, O. K.

1979-01-01

166

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

167

Convective cell formation in a levitated dipole Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139  

E-print Network

Convective cell formation in a levitated dipole J. Kesner Plasma Science and Fusion Center cells. Using a ``drift'' fluid model, it is shown that such flow patterns can represent an appropriate of convective cells in closed field line configurations that lack magnetic shear.4­6 Thus, in a dipole

Garnier, Darren T.

168

Convective motion and the structure of the Jupiter magnetosphere  

NASA Technical Reports Server (NTRS)

The convective motion and its relation to the electric field in the magnetosphere of Jupiter are investigated. It is shown that the electric field is induced in the Jovian ionosphere due to the corotating action of the ionospheric gases and further is communicated into the magnetosphere along the magnetic lines of force which connect between the ionosphere and the magnetosphere. This electric field drives the plasma to corotate with the planet in the magnetosphere. The distribution of the electric field and its effect on the plasma motion is estimated in the magnetosphere. The shape of the magnetosphere is then estimated considering the equilibrium condition. Discussion is given on the equilibrium plasma distribution in the magnetosphere and on the condition for the excitation of wave-particle interaction at the Io orbit.

Sakurai, K.

1971-01-01

169

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

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

170

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

171

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

172

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

Microsoft Academic Search

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

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

2008-01-01

173

Mid-latitude ionospheric perturbation associated with the Spacelab-2 plasma depletion experiment at Millstone Hill  

E-print Network

scatter radar at Millstone Hill captured the ionospheric response to the ®ring of the Space Shuttle In a sequence of planned experiments, the orbital maneuvering subsystem (OMS) engines of the Space Shuttle Challenger OMS thrusters near the peak of the F layer on July 30, 1985. Details of the excitation of airglow

Paris-Sud XI, Université de

174

Nonlinear dynamics of the 3D FMS and Alfven wave beams propagating in plasma of ionosphere and magnetosphere  

NASA Astrophysics Data System (ADS)

We study the formation, structure, stability and dynamics of the multidimensional soliton-like beam structures forming on the low-frequency branch of oscillation in the ionospheric and magnetospheric plasma for cases when beta=4pinT/B(2) <<1 and beta>1. In first case with the conditions omega>{k_{yz}}(2,) v_{x}$<plasma parameters and the angle Theta=(B,k) [2]. In another case the dynamics of the finite-amplitude Alfvén waves propagating in the ionosphere and magnetosphere near-to-parallel to the field B is described by the 3D derivative nonlinear Schrödinger (3-DNLS) equation for the magnetic field of the wave h=(B_{y}+iB_{z})/2B/1-beta/ [3]. To study the stability of multidimensional solitons in both cases we use the method developed in [2] and investigated the Hamiltonian bounding with its deformation conserving momentum by solving the corresponding variation problem. To study evolution of solitons and their collision dynamics the proper equations were being integrated numerically using the codes specially developed and described in detail in [3]. As a result, we have obtained that in both cases for a single solitons on a level with wave spreading and collapse the formation of multidimensional solitons can be observed. These results may be interpreted in terms of self-focusing phenomenon for the FMS and Alfvén waves’ beam as stationary beam formation, scattering and self-focusing of wave beam. The soliton collisions on a level with known elastic interaction can lead to formation of complex structures including the multisoliton bound states. For all cases the problem of multidimensional soliton dynamics in the ionospheric and magnetospheric plasma including all stages of their evolution and collision dynamics is investigated in detail. References 1. Karpman V.I., Belashov V.Yu. Physics Letters, 1991, V. 154A, N 3/4, P. 131. 2. Belashov V.Yu. Plasma Phys. And Contr. Fusion, 1994, V. 36, P. 1661. 3. Belashov V.Yu., Vladimirov S.V., Solitary Waves in Dispersive Complex Media. Theory, Simulation, Applications. Springer-Verlag GmbH & Co. KG, 2005, 305 p.

Belashov, Vasily

175

The ‘churning mode’ of plasma convection in the tokamak divertor region  

NASA Astrophysics Data System (ADS)

The churning mode can arise in a toroidally-symmetric plasma where it causes convection in the vicinity of the poloidal magnetic field null. The mode is driven by the toroidal curvature of magnetic field lines coupled with a pressure gradient. The toroidal equilibrium conditions cannot be satisfied easily in the virtual absence of the poloidal field (PF)—hence the onset of this mode, which ‘churns’ the plasma around the PF null without perturbing the strong toroidal field. We find the conditions under which this mode can be excited in magnetic configurations with first-, second-, and third-order PF nulls (i.e., in the geometry of standard, snowflake and cloverleaf divertors). The size of the affected zone in second- and third-order-null divertors is much larger than in a standard first-order-null divertor. The proposed phenomenological theory allows one to evaluate observable characteristics of the mode, in particular the frequency and amplitude of the PF perturbations. The mode spreads the tokamak heat exhaust between multiple divertor legs and may lead to a broadening of the plasma width in each leg. The mode causes much more intense plasma convection in the poloidal plane than the classical plasma drifts.

Ryutov, D. D.; Cohen, R. H.; Farmer, W. A.; Rognlien, T. D.; Umansky, M. V.

2014-08-01

176

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

177

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

178

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

179

A Miniaturized Plasma Impedance Probe For Ionospheric Absolute Electron Density and Electron-Neutral Collision Frequency Measurements  

NASA Astrophysics Data System (ADS)

A fully integrated, low power, miniaturized Plasma Impedance Probe (PIP) is developed for small satellite constellation missions to create a map of electron density in the ionosphere. Two alternative methods for deriving plasma parameters from impedance measurements are discussed. The first method employs a frequency sweep technique, while the second employs a pulse based technique. The pulse based technique is a new method that leads to faster measurements. The two techniques necessitate different specifications for the front end analog circuit design. Unlike previous PIP designs, the integrated PIP performs direct voltage/current sampling at the probe's terminal. The signal processing tasks are performed by an off-chip FPGA to compute the impedance of the probe in the surrounding plasma. The new design includes self- calibration algorithms in order to increase the accuracy and reliability of the probe for small satellite constellation missions. A new feature included in this instrument is that the plasma parameters are derived from impedance measurements directly on the FPGA, significantly reducing the bandwith of telemetered data down to ground.

Patra, S.; Rao, A. J.; Jayaram, M.; Hamoui, M. E.; Spencer, E. A.; Winstead, C.

2008-12-01

180

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

181

A snowflake divertor: reduction of the ELM heat load due to plasma convection  

NASA Astrophysics Data System (ADS)

A snowflake magnetic configuration is created when the poloidal magnetic field and its spatial derivatives turn zero at a certain point. The separatrix then acquires a characteristic hexagonal shape reminiscent of a snowflake and the number of divertor plate strike points increases from two to four. We point out that the snowflake divertor could solve the ELM heat load problem by spreading the heat over a large area and engaging all four strike points. The mechanism is related to a fast increase of the plasma beta in the divertor region during ELM. Due to very low values of the poloidal magnetic field over a large area of a snowflake divertor, plasma convection sets in that leads to the desired effect. Conditions for the onset of a convective instability and/or the loss of equilibrium are formulated, and estimates of the size of the zone involved in convective motion are presented. Work performed for U.S. DoE by LLNL under Contract DE-AC52-07NA27344.

Ryutov, D. D.; Cohen, R. H.; Rognlien, T. D.; Umansky, M. V.

2011-11-01

182

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

183

Mapping Ionospheric Electrodynamics with SuperDARN Data: An Assimilative Technique  

NASA Astrophysics Data System (ADS)

Mapping of electrodynamic parameters in Earth's high-latitude ionosphere has been performed widely for many years. Knowledge of the complete pattern of ionospheric plasma convection enables studies of solar wind-magnetosphere-ionosphere coupling, allows for the placing of localized observations in a larger context, and can be used to drive coupled ionosphere-thermosphere first-principles models. In the past, an assimilative procedure has been developed to map ionospheric electrodynamics based on combining various types of observations (e.g., magnetometers, satellites, and incoherent or coherent scatter radars) [Richmond and Kamide, 1988], and a simple regression technique has been developed to use exclusively data from the Super Dual Auroral Radar Network (SuperDARN) coherent backscatter radars [Ruohoniemi and Baker, 1998; Shepherd and Ruohoniemi, 2000]. In this study, an assimilative procedure is developed to combine exclusively SuperDARN data with the empirical plasma convection model of Cousins and Shepherd [2010] (CS10, also based on SuperDARN data). The statistical properties of the CS10 model errors are investigated using the method of empirical orthogonal functions (EOFs) applied to an ~2 yr data set, and a parameterization of the CS10 model error covariance matrix is obtained. The new SuperDARN assimilative procedure, which takes into account realistic error covariances, is shown to significantly improve the mapping of electrodynamic parameters (as compared to the existing regression-based SuperDARN mapping procedure). The application of this assimilative procedure is demonstrated for a geomagnetic storm.

Cousins, E. D.; Matsuo, T.; Richmond, A. D.

2013-12-01

184

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

185

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

186

C/NOFS satellite observations of equatorial ionospheric plasma structures supported by multiple ground-based diagnostics in October 2008  

NASA Astrophysics Data System (ADS)

In early October 2008, the C/NOFS satellite orbited near the magnetic equator at its perigee altitude of ˜400 km at dusk in the Peruvian sector. This provided an ideal opportunity for a comparison, under the current very low solar flux condition, of equatorial ionospheric disturbances observed with the Communication/Navigation Outage Forecasting System (C/NOFS) in situ measurements and ground-based observations available near Jicamarca Observatory. The primary objective was the comparison of plasma density disturbances measured by a Planar Langmuir Probe (PLP) instrument on the C/NOFS satellite with VHF scintillation activity at Ancon near Jicamarca for this period. Here we discuss in detail two extreme cases: one in which severe in situ disturbances were accompanied by mild scintillation on a particular day, namely, 10 October while there was little in situ disturbance with strong scintillation on 5 October. This apparent contradiction was diagnosed further by a latitudinal ground-based GPS network at Peruvian longitudes, a Digisonde, and the incoherent scatter radar (ISR) at Jicamarca. The crucial distinction was provided by the behavior of the equatorial ionization anomaly (EIA). The EIA was well-developed on the day having severe in situ disturbances (10 Oct). This led to lower equatorial plasma density and total electron content (TEC) at the equator and consequently reduced the scintillations detected at Ancon. On the other hand, on the day with severe scintillations (5 Oct), the EIA was not so well developed as on 10 October, leading to relatively higher equatorial plasma density and TEC. Consequently the severe scintillations at Ancon were likely caused by ionospheric structure located below the altitude of C/NOFS. The NRL SAMI2 model was utilized to gain a greater understanding of the role of neutral winds and electric fields in reproducing the TEC as a function of latitude for both classes of irregularities. Spectral studies with high resolution in situ PLP data were also performed. The power law spectra within the plasma bubbles showed two slopes: the low frequency slope being ˜-5/3 and the high frequency ˜-5 with a break around ? = 70 m. This particular type of two-slope spectra may be related to the extremely low solar activity and its impact on ion composition and temperature.

Nishioka, M.; Basu, Su.; Basu, S.; Valladares, C. E.; Sheehan, R. E.; Roddy, P. A.; Groves, K. M.

2011-10-01

187

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

NASA Astrophysics Data System (ADS)

We propose a simple model of the flow and currents in Saturn's polar ionosphere. This model is motivated by theoretical reasoning, and guided quantitatively by in situ field and flow data from space missions, ground-based IR Doppler measurements, and Hubble Space Telescope images. The flow pattern consists of components which represent (1) plasma sub-corotation in the middle magnetosphere region resulting from plasma pick-up and radial transport from internal sources; (2) the Vasyliunas-cycle of internal plasma mass-loss down the magnetospheric tail at higher latitudes; and (3) the polar Dungey-cycle flow driven by the solar wind interaction. Upstream measurements of the interplanetary magnetic field (IMF) indicate the occurrence of both extended low-field rarefaction intervals with essentially negligible Dungey-cycle flow, and few-day high-field compression regions in which the Dungey-cycle voltage peaks at a few hundred kV. Here we model the latter conditions when the Dungey-cycle is active, advancing on previous axi-symmetric models which may be more directly applicable to quiet conditions. For theoretical convenience the overall flow pattern is constructed by adding together two components - a purely rotational flow similar to previous axi-symmetric models, and a sun-aligned twin vortex representing the dawn-dusk asymmetry effects associated with the Vasyliunas-and Dungey-cycle flows. We calculate the horizontal ionospheric current associated with the flow and the field-aligned current from its divergence. These calculations show that a sheet of upward-directed field-aligned current flows at the boundary of open field lines which is strongly modulated in local-time by the Dungey-cycle flows. We then consider implications of the field-aligned current for magnetospheric electron acceleration and aurorae using two plasma source populations (hot outer magnetospheric electrons and cool dense magnetosheath electrons). Both sources display a strong dawn-dusk asymmetry in the accelerating voltages required and the energy fluxes produced, resulting from the corresponding asymmetry in the current. The auroral intensities for the outer magnetosphere source are typically ~50 kR at dawn and ~5 kR at dusk, in conformity with recent auroral observations under appropriate conditions. However, those for the magnetosheath source are much smaller. When the calculated precipitating electron energy flux values are integrated across the current layer and around the open closed field line boundary, this yields total UV output powers of ~10 GW for the hot outer magnetosphere source, which also agrees with observations.

Jackman, C. M.; Cowley, S. W. H.

2006-05-01

188

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

SciTech Connect

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

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

2010-02-15

189

On the threshold of thermal parametric instabilities in inhomogeneous ionospheric plasma  

E-print Network

instabilities 45 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 5.2 TPI in homogeneous plasma . . . . . . . . . . . . . . . . . . . . 49 5.3 TPI in inhomogeneous plasma . . . . . . . . . . . . . . . . . . . 55 5.4 TPI with 0 nce . . . . . . . . . . . . . . . . . . . . . . . . . 56 5.5 Graphical

190

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

191

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

192

Progress in Observation-Based Ionospheric Modeling  

Microsoft Academic Search

Models for the ionospheric component of space weather are needed for a wide range of applications. For example, any remote sensing techniques that use radio waves traveling through the ionosphere, looking up from the ground or down from space, must correct for the retarding, refractive, and scintillation effects of the ionospheric plasma. Two types of models are used for this

Dieter Bilitza; Bodo Reinisch; Jan Lastovicka

2008-01-01

193

High latitude field aligned light ion flows in the topside ionosphere deduced from ion composition and plasma temperatures  

NASA Technical Reports Server (NTRS)

Using a comprehensive ionospheric data set comprised of all available ion composition and plasma temperature measurements from satellites, the vertical distributions of ion composition and plasma temperatures are defined from middle latitudes up into the polar cap for summer conditions for altitudes below about 1200 km. These data are sufficient to allow a numerical estimation of the latitudinal variation of the light ion outflows from within the plasmasphere to the polar wind regions. The altitude at which significant light ion outflow begins is found to be lower during solar minimum conditions than during solar maximum. The H(+) outward speeds are of the order of 1 km/s near 1100 km during solar maximum but attain several km/s speeds for solar minimum. He(+) shows a similar altitude development of flow but attains polar cap speeds much less than 1 km/s at altitudes below 1100 km, particularly under solar maximum conditions. Outward flows are also found in the topside F-region for noontime magnetic flux tubes within the plasmasphere.

Grebowsky, J. M.; Hoegy, W. R.; Chen, T. C.

1993-01-01

194

Subgrid modeling of convective turbulence in weakly ionized collisional plasma by renormalization group analysis  

SciTech Connect

The equations governing the nonlinear evolution of density fluctuations in a low-pressure weakly ionized plasma driven unstable by the ExB or gradient-drift instability were derived by Sudan and Keskinen for addressing the electrostatic turbulence in the E and F regions of the Earth`s ionosphere. The authors have developed a subgrid model suitable for the numerical simulation of these equations which is closely related to renormalized diffusion caused by small-scale fluctuation spectrum. {open_quotes}Dynamical Renormalization Group{close_quotes} (RNG) methods are employed to obtain the renormalized diffusion. This procedure computes the long-wavelength, long-time behavior of density correlations generated by the evolution equation for the plasma stirred by a Gaussian random force characterized by a correlation function {proportional_to} k{sup m} where k is the wavenumber of the forcing function. The effect of small scales on the large-scale dynamics in the limit k{yields}0 and infinite Reynolds number can be expressed in the form of renormalized coefficients; in this case, renormalized diffusion. If one assumes the power spectra to be given by the Kolmogorov argument of cascading of energy through k space then one can derive a subgrid model based on the results of RNG. 27 refs.

Hamza, A.M. [Univ. of Western Ontario, London (Canada)] [Univ. of Western Ontario, London (Canada); Sudan, R.N. [Cornell Univ., Ithaca, NY (United States)] [Cornell Univ., Ithaca, NY (United States)

1995-03-01

195

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

E-print Network

GEOPHYSICAL RESEARCH LETTERS, VOL. 30(21), 2109, DOI:10.1029/2003GL017668, 2003 Direct measurements of the field over the entire high-latitude ionosphere. Copyright 2003 by the American Geophysical Union. 0094

Shepherd, Simon

196

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

197

Plasma density-electric field turbulence in the low-latitude ionosphere from the observation on satellites; possible connection with seismicity  

Microsoft Academic Search

Based on plasma density data from the Cosmos-900 satellite we have analyzed the spatial distribution of the ionospheric turbulence in a form k?b, where k is wave number and b is the fractal index. In this case spatial scales (?k?1) are ranging from 15 to 300 km at the satellite height h=450–500 km. Depending on season, local time and seismic

O. A Molchanov; O. S Akentieva; V. V Afonin; E. A Mareev; E Fedorov

2004-01-01

198

Ionospheric modeling  

Microsoft Academic Search

The purpose of this report is to familiarize a user of ionospheric models with the options presently available for ionospheric prediction and specification. Two types of ionospheric models are available: the numerical-phenomenological and theoretical models. From the numerical type, the ITS-78, IONCAP, and Bent models have been discussed. In the theoretical models the main concern is the number of parameters

B. S. Dandekar

1982-01-01

199

Diagnosis of the turbulent state of ionospheric plasma by propagation methods  

Microsoft Academic Search

An electromagnetic signal randomized by scattering from plasma irregularities and by subsequent diffraction in the nonrandom part of the medium is known to bear statistical information about the plasma turbulent irregularities. For example, if the turbulent spectrum is of the form K -p in its wavenumber dependence, the received amplitude of the electromagnetic signal will fluctuate with a high frequency

K. C. Yeh; C. H. Liu

1977-01-01

200

Convective radial transport in a linear magnetized plasma column and fast infrared imaging of plasma turbulence  

Microsoft Academic Search

The transition to turbulence of strongly nonlinear low frequency unstable waves obtained in a new magnetized plasma device is studied. The device consists in a large multipolar plasma chamber (1.4m diameter, 1 m length) connected to a cylinder (40 cm diam., 1m length) and a half-torus (40 cm diam., 0.61 m large radius). The linear and curved columns are surrounded

Alexandre Escarguel; Thiery Pierre; Gerard Leclert; Didier Guyomarc'h; Kamal Quotb

2002-01-01

201

Small scale processes in ionosphere-magnetosphere coupling, from an ionospheric perspective.  

NASA Astrophysics Data System (ADS)

On a global scale, ionospheric-magnetospheric coupling is reasonably well understood in terms of Regions I and II currents and the convection patterns that they generate. However the smaller scale picture can be much more complex, with substructures in the ionosphere that do not necessarily line up with the original magnetospheric configuration, important physics introduced by very different current carriers, and with small scale plasma irregularities affecting the transport properties of the overall plasma in major ways. As a starting point, we have to recognize that the ionosphere does not react passively to electron precipitation and Alfven waves triggered by magnetospheric processes. For instance, the ionosphere reflects incoming Alfven waves by establishing the net parallel currents that must come out of the ionosphere for a given perpendicular electric field distribution associated with the impeding waves. One aspect that deserves attention is that with or without an Alfven wave transition, the vertical current distribution can be quite complex particularly when small scale conductivity gradients are taken into account. For instance, the tilt in the magnetic field can be such that in relatively narrow (km size) auroral structures, advection by Pedersen ion drifts will take the E region plasma as far as 100 km away from the region of precipitation, further modifying the conductivities and parallel current distribution in the process. In addition, above about 300 km, the currents are essentially all field-aligned. An interesting aspect is that the carriers for return currents originating from the ionosphere are cold thermal electrons moving upwards. If these returning current densities are large enough, then, somewhere above the topside, the current carriers have to switch to high energy electrons since the plasma is bound to become violently unstable to streaming instabilities. The instabilities slow down the upgoing electrons through the introduction of anomalous resistivity, in turn triggering a change in the current carriers from thermal or suprathermal to much more energetic. It can also be shown that the negative space charge in those regions is able to produce, as observed, ion conics in addition to triggering fluxes of energetic electrons. The thermal current density can also become so intense at times, that large amplitude ion acoustic waves detected as NEALS by incoherent scatter radars will be generated in the ionosphere itself through the large relative drifts between the different ion and electron populations (with relative drifts from either thermal or suprathermal electrons). It should also be recognized that even without an instability, the vertical currents generated by the ionospheric electrons will involve an increasingly large number of runaway electrons. This has been shown to increase the parallel conductivity by measurable amounts. Finally, when the perpendicular electric field exceeds 25 to 30 mV/m, strong Farley-Buneman turbulence in the E region will lead to increased electron temperatures and to changes in the ionospheric conductivities, providing yet another nonlinear feedback mechanism between the ionosphere and the magnetosphere.

St-Maurice, Jean-Pierre

202

DRIFT-DISSIPATIVE PLASMA INSTABILITY AND EQUATORIAL SPREAD F  

Microsoft Academic Search

Electrostatic oscillations of a plasma drifting across a magnetic field are considered. The convective instability that arises in a medium containing a gradient of electron concentration is investigated for the case when charge-particle motions are dominated by collisions. The proposal that this instability is the amplification mechanism for producing the irregularities responsible for ionospheric spread-F conditions at equatorial latitudes is

D. M. Cunnold

1969-01-01

203

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

SciTech Connect

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 heater propagation. For typical parameters of the current Arecibo heater, a dramatic quasi-periodic behavior was found. For about 50 ms after turn-on of the heater wave, the turbulence is concentrated at the first standing-wave maximum of the heater near reflection altitude. From 50--100 ms the standing-wave pattern drops by about 1--2 km in altitude and the quasi-periodicity reappears at the higher altitudes with a period of roughly 50 ms. This behavior is due to the half-wavelength density depletion grating that is set up by the ponderomotive pressure at the maxima of the heater standing-wave pattern. Once the grating is established the heater can no longer propagate to higher altitudes. The grating is then unsupported by the heater at these altitudes and decays, allowing the heater to propagate again and initiate another cycle. For stronger heater powers, corresponding to the Arecibo upgrade and the HAARP heater now under construction, the effects are much more dramatic.

Rose, H.; Dubois, D.; Russell, D. [Lodestar Research Corp., Boulder, CO (United States); Hanssen, A. [Univ. of Tromsoe (Norway)

1996-03-01

204

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

SciTech Connect

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

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

2014-08-15

205

Incoherent scatter radar detection of enhanced plasma line in ionospheric E-region over Arecibo  

E-print Network

A series of incoherent scatter radar (ISR) observation were conducted at the Arecibo Observatory from December 27, 2005 until January 3, 2006. From plasma line measurements that were taken during this radar campaign, we ...

Pradipta, Rezy

2006-01-01

206

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

207

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

NASA Astrophysics Data System (ADS)

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

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

208

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

209

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

210

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

211

Kinetic simulation of plasma flows in the inner magnetosphere  

NASA Technical Reports Server (NTRS)

A one-dimensional hybrid particle code is used to study the interactions between upflowing thermal ions from conjugate ionospheres. The simulation model allows for multiple species, convection of plasmaspheric flux tubes, and Coulomb self-collisions which conserve momentum and energy locally. The model incorporates a variable-flux boundary condition where the flux, at the boundaries, approaches zero as the plasmasphere fills and equilibrium conditions are reached. The effects of two important processes on plasmaspheric refilling have been considered. The first includes convection of the plasmaspheric flux tube. The second is the interaction of ionospheric thermal plasma and particle injection from an external source. Particle injection seems to play an important role in the evolution of the total particle distribution on the early timescales (t less than 1 hour); however, for late timescales (t larger than 8 days) the thermal plasma from the ionosphere dominates the particle distribution.

Miller, Ronald H.; Rasmussen, Craig E.; Gombosi, Tamas I.; Khazanov, Georgi V.; Winske, Dan

1993-01-01

212

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

213

Radar soundings of the ionosphere of Mars.  

PubMed

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

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

2005-12-23

214

Cold plasma heating in the plasma sheet boundary layer - Theory and simulations  

NASA Technical Reports Server (NTRS)

Satellite observations in recent years have confirmed that the plasma sheet boundary layer is a permanent feature of the earth's magnetotail located between the lobe and central plasma sheet during both quiet and active magnetic periods. Distinct features of the boundary layer include field aligned ion beams and intense electrostatic emissions known as broadband electrostatic noise. Since the plasma sheet boundary layer is a spatial feature of the magnetotail, within it will occur thermal mixing of the resident warm boundary layer plasma with inflowing (convecting) cold ionospheric plasma. A theoretical study involving linear theory and nonlinear numerical particle simulations is presented which examines ion beam instabilities in the presence of a thermally mixed hot and cold background plasma. It is found that the free energy in the ion beams can heat the cool ionospheric plasma to ambient plasma sheet boundary layer temperatures via broadband electrostatic noise. These results, along with recent observational reports that ionospheric outflow can account for measured plasma sheet densities, suggest that the ionospheric role in plasma sheet dynamics and content may be as large as the solar wind.

Schriver, David; Ashour-Abdalla, Maha

1990-01-01

215

Multi-instrument studies of ionospheric and magnetospheric processes  

NASA Astrophysics Data System (ADS)

In this thesis, several aspects of the convection, magnetic, and optical auroral dynamics of the high-latitude ionosphere are investigated from multi- instrument observations. The spatial and temporal relationships between nightside radar flow enhancements (NRFEs) and auroral intensifications are studied in Chapter 3. The NRFEs on open field lines are usually associated with very little accompanying auroral and magnetic activity. The NRFEs on closed field lines are often accompanied by optical auroral activity, but there is not a definite one-to-one correspondence. Both the statistical investigation and event study showed that the NRFEs may occur nearly simultaneously with the auroral intensifications. Because existing models associating the tail reconnection process and near- geosynchronous onset of substorms do not explain these correlated radar and optical observations very well, we propose a new model to explain the nearly simultaneous onset of the NRFEs and the auroral intensifications. In Chapter 4 we describe a small postmidnight substorm event on October 9, 2000 during dominantly IMF By+ Bz+ conditions. A sequence of three optical auroral intensifications and Pi2 bursts were found. The first two activations were characteristic of pseudobreakups, while the last and strongest intensification corresponded to a substorm expansive phase (EP). The auroral, magnetic and radar signatures of the event are interpreted as the consequence of three successive drift-Alfven-ballooning (DAB) mode instabilities in the near- geosynchronous orbit plasma sheet (NGOPS). About 10 minutes after the EP onset, there was a second auroral brightening. The convection feature during this second auroral brightening was consistent with the scenario of a Stage-2 EP. We suggest that the first two pseudobreakups, the Stage-1 EP, and the Stage-2 EP are related, respectively, to loading-unloading, directly driven, and internal magnetotail processes. Finally, in Chapter 5, we make some comparisons between the ionospheric plasma convection vortex structure observed by SuperDARN and the associated equivalent current pattern derived from the magnetometer observations. The discrepancies between the equivalent convection (EQC) and the SuperDARN-observed convection (SDC) pattern are explained in terms of the effect of day-night photoionization conductance gradient, and the coupling between field-aligned currents (FACs) and ionospheric conductances. In particular, we found the agreement between the EQC and SDC patterns is rather poor for a counterclockwise convection vortex. We suggest the discrepancies are probably due to a downward FAC-conductance coupling process.

Liang, Jun

216

Ionospheric plasma modification in the vicinity of a spacecraft by powerful radio pulses in topside sounding  

NASA Astrophysics Data System (ADS)

A mechanism of strong turbulence is proposed for interpretation of the resonances observed by a wide-band receiver during topside sounding. The turbulence is created in the vicinity of the spacecraft due to the striction modulation instability. Experimental results obtained with the aid of a wide-band receiver on board the Intercosmos-19 satellite are discussed in terms of strong wave-wave and/or wave-particle interaction, namely electron acceleration in Langmuir cavitons and non-linear generation of the electron Langmuir plasma waves and Tonks-Dattner resonances.

Pulinets, S. A.; Selegei, V. V.

1986-02-01

217

Plasma waves generated in the ionosphere by an argon ion beam  

NASA Astrophysics Data System (ADS)

Two argon ion generators were operated during a sounding rocket flight from Sondre Stromfjord, Greenland, on February 10, 1985. One generator emitted an ion beam perpendicular to the magnetic field and the other a beam parallel to the field. The ion generators were on a subpayload that was separated from the main payload early in the flight. Plasma waves were observed during most of the first seven operations of each beam. Helium and oxygen cyclotron harmonics were observed in early perpendicular beam operations. The parallel beam waves were line emissions, some at approximate multiples of the hydrogen cyclotron frequency and near the lower hybrid frequency.

Cahill, L. J., Jr.; Erlandson, R. E.; Arnoldy, R. L.; Pollock, C. J.

218

Coordinated ESR-Reimei observations of the cusp ionosphere  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

219

Polar BEAR ionospheric experiments - a pre-launch overview. Technical report, 1 March-31 October 1985  

SciTech Connect

Polar BEAR (Polar BEacon and Auroral Research) will carry three ionospheric experiments: (1) a beacon functionally identical to that on HiLat, (2) a three-axis vector magnetometer for detecting the satellite's attitude, and (3) an improved imager, the Auroral/Ionospheric Remote Sensor (AIRS). In addition to providing images of the aurorae and airglow at four visual and vacuum-ultraviolet wavelengths, AIRS will function as an ultraviolet spectrophotometer. Using AIRS in its imaging mode and receiving stations it will be possible to obtain images of essentially the entire auroral oval in broad daylight as well as in darkness. Polar BEAR is scheduled for launch into a nearly circular orbit near 1000-km altitude and 82 inclination. That orbit will afford a broad view for AIRS and many opportunities for coordinated observations of (1) scintillation using the beacons on both HiLat and Polar BEAR, (2) major current systems flowing between the ionosphere and magnetosphere using the magnetometers on both satellites, and (3) energetic electron precipitation and ambient plasma convection at 800 km altitude as recorded with HiLat's electron spectrometer and thermal-plasma monitor. These observations should contribute to further understanding of plasma instrumental to the development of density irregularities in the highly dynamic high-latitude ionosphere.

Fremouw, E.J.

1986-05-09

220

The response of the high-latitude dayside ionosphere to an abrupt northward transition in the IMF  

NASA Technical Reports Server (NTRS)

We examine the response of the high-latitude ionosphere in the prenoon sector to a northward turning of the IMF. The event was observed in the 11-13 UT interval on June 1, 1987, in the course of a multiday SUNDIAL campaign. The transition in the IMF was observed by the IMP-8 satellite which was located upstream of the earth at a distance of 36 Re. The ionospheric response in the 70-80 deg invariant latitude interval was monitored by two radars. The preexisting plasma convection observed by the radars exhibited large velocities (500-1000 m/s) and stable longterm trends, consistent with the inertial rotation of the convection pattern expected of the conditions then prevailing, B(z) less than 0, B(y) greater than 0. The plasma flow rapidly abated in response to the IMF transition. The electron density measurements made by radar in the meridional plane showed that the ionosphere had been rich in structure with the active deposition of ionization by particle precipitation. Subsequently it resembled an inactive, unstructured mid-latitude configuration. There was a dramatic decrease in the amount of backscatter observed by the HF radar. We analyze the times of transition in the various data sets and show that the ionosphere began to show the effects of the IMF transition about 2 min after its probable arrival at the magnetopause boundary.

Ruohoniemi, J. M.; Greenwald, R. A.; De La Beaujardiere, O.; Lester, M.

1993-01-01

221

The response of the high-latitude dayside ionosphere to an abrupt northward transition in the IMF  

NASA Astrophysics Data System (ADS)

We examine the response of the high-latitude ionosphere in the prenoon sector to a northward turning of the IMF. The event was observed in the 11-13 UT interval on June 1, 1987, in the course of a multiday SUNDIAL campaign. The transition in the IMF was observed by the IMP-8 satellite which was located upstream of the earth at a distance of 36 Re. The ionospheric response in the 70-80 deg invariant latitude interval was monitored by two radars. The preexisting plasma convection observed by the radars exhibited large velocities (500-1000 m/s) and stable longterm trends, consistent with the inertial rotation of the convection pattern expected of the conditions then prevailing, B(z) less than 0, B(y) greater than 0. The plasma flow rapidly abated in response to the IMF transition. The electron density measurements made by radar in the meridional plane showed that the ionosphere had been rich in structure with the active deposition of ionization by particle precipitation. Subsequently it resembled an inactive, unstructured mid-latitude configuration. There was a dramatic decrease in the amount of backscatter observed by the HF radar. We analyze the times of transition in the various data sets and show that the ionosphere began to show the effects of the IMF transition about 2 min after its probable arrival at the magnetopause boundary.

Ruohoniemi, J. M.; Greenwald, R. A.; de La Beaujardiere, O.; Lester, M.

1993-07-01

222

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

223

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

224

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

225

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

226

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

227

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

228

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

Microsoft Academic Search

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

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

1982-01-01

229

Magnetospheric Convection near a Drainage Plume  

NASA Astrophysics Data System (ADS)

We report on equatorial convection associated with a plasmaspheric drainage plume using simultaneous observations from five satellites. During the early recovery phase of the July 2000 Bastille Day magnetic storm, the Extreme Ultraviolet sensor on the Magnetopause-to-Aurora Global Exploration satellite detected the plume near 16:00-17:00 magnetic local time extending outward to L ? 2.8. The plasmaspheric boundary was near L = 2 at other local times. We mapped simultaneously measured ionospheric plasma drifts from ROCSAT-1 and three Defense Meteorological Satellite Program (DMSP) spacecraft along magnetic field lines to infer equatorial convection velocities in the inner magnetosphere. The zonal component of convection derived from ROCSAT-1 ion-drift measurements had a sharp, positive azimuthal gradient near the plume's boundaries, reversing direction from westward to eastward. The meridional profile of horizontal velocities deduced from DMSP measurements shows a large, westward-flowing subauroral polarization stream (SAPS) located outside the plasmapause. The peak velocity of the SAPS centered at a radial distance of L ? 2.8 with a full width of ˜1 RE. In the inertial frame of reference, equatorial plasmas flowed toward the plume from both its day and evening sides, suggesting a negative gradient in the equatorial azimuthal velocity that was largest near the plume's outermost boundary. These observations provide new evidence about diversion of SAPS plasma flows and distinctive azimuthal velocity patterns in the vicinity of plasmaspheric plumes.

Lin, Chin S.; Yeh, Huey-Ching; Sandel, Bill R.; Goldstein, J.; Rich, Frederick J.; Burke, William J.; Foster, J. C.

2007-05-01

230

Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere  

NASA Astrophysics Data System (ADS)

A new approach for investigating ionosphere chemical depletion in the laboratory is introduced. Air glow discharge plasma closely resembling the ionosphere in both composition and chemical reactions is used as the artificially created ionosphere. The ionospheric depletion experiment is accomplished by releasing chemicals such as SF6, CCl2F2, and CO2 into the model discharge. The evolution of the electron density is investigated by varying the plasma pressure and input power. It is found that the negative ion (SF6-, CCl2F2-) intermediary species provide larger reduction of the electron density than the positive ion (CO2+) intermediary species. The negative ion intermediary species are also more efficient in producing ionospheric holes because of their fast reaction rates. Airglow enhancement attributed to SF6 and CO2 releases agrees well with the published data. Compared to the traditional methods, the new scheme is simpler to use, both in the release of chemicals and in the electron density measurements. It is therefore more efficient for investigating the release of chemicals in the ionosphere.

Liu, Yu; Cao, Jinxiang; Wang, Jian; Zheng, Zhe; Xu, Liang; Du, Yinchang

2012-09-01

231

Experimentally investigate ionospheric depletion chemicals in artificially created ionosphere  

SciTech Connect

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

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

2012-09-15

232

Tomographic estimation of the ionosphere using terrestrial GPS sensors  

Microsoft Academic Search

The ionosphere is a region of partially ionized plasma in Earth's upper atmosphere distributed in layers of varying free electron density. The free electrons change the local index of refraction causing radio waves propagating in the ionosphere to be delayed and bent. Trans-ionospheric propagation of GPS radio signals transmitted from satellites provides observations, in a tomographic sense, of the electron

Andrew Jakob Hansen

2002-01-01

233

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

234

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

235

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

236

Excitation of convective cells by drift-like electromagnetic modes in a magnetized dusty plasma  

Microsoft Academic Search

We present a pair of coupled equations that shows the nonlinear coupling between a newly discovered low-frequency dispersive electromagnetic mode and flute-like electrostatic convective cells in a non-uniform dusty magnetoplasma. From the coupled mode equations we obtain a nonlinear dispersion relation, which predicts efficient excitation of convective cells at the expense of the dispersive electromagnetic wave energy. The relevance of

P. K. Shukla; L. Stenflo

2004-01-01

237

Change of ionospheric plasma parameters under the influence of electric field which has lithospheric origin and due to radon emanation  

NASA Astrophysics Data System (ADS)

A mechanism of electric-photochemistry channel of seismo-ionospheric coupling is investigated. In particular, the penetration of electric field from the lithospheric source into the ionosphere and effect of this field on the photochemistry coefficient and ionospheric parameters in the altitude range in the lower D region are modeled numerically. It is shown that observable effects can be expected when lithospheric electric source strength is of the order of 1.5 kV/m. In this case, variations of electron temperature and electron concentration will be of the order of (40-60)% and (25-40)% respectively at the range of altitudes 60-70 km. An increase of near-ground conductivity (caused by increasing humidity and/or radon emanation) by ?2.3 times can cause increase of electric field intensity by ?2 times in altitude ranges of 60-70 km. Corresponding relative change of Te increases up to ?50%, as compared with the case of lower near-ground temperature. Spatial shapes of relative distribution of electron temperature and the ratio of negative ion-electron concentration map the spatial shape of the lithospheric electric field distribution. Spatial shapes of electron concentration distribution and electric field strength distribution of the lithospheric source are “opposite” to each other.

Rapoport, Y.; Grimalsky, V.; Hayakawa, M.; Ivchenko, V.; Juarez-R, D.; Koshevaya, S.; Gotynyan, O.

238

Ion Escape from the Ionosphere of Titan  

NASA Technical Reports Server (NTRS)

Ions have been observed to flow away from Titan along its induced magnetic tail by the Plasma Science Instrument (PLS) on Voyager 1 and the Cassini Plasma Spectrometer (CAPS) on Cassini. In both cases, the ions have been inferred to be of ionospheric origin. Recent plasma measurements made at another unmagnetized body, Venus, have also observed similar flow in its magnetic tail. Much earlier, the possibility of such flow was inferred when ionospheric measurements made from the Pioneer Venus Orbiter (PVO) were used to derive upward flow and acceleration of H(+), D(+) and O(+) within the nightside ionosphere of Venus. The measurements revealed that the polarization electric field in the ionosphere produced the principal upward force on these light ions. The resulting vertical flow of H(+) and D(+) was found to be the dominant escape mechanism of hydrogen and deuterium, corresponding to loss rates consistent with large oceans in early Venus. Other electrodynamic forces were unimportant because the plasma beta in the nightside ionosphere of Venus is much greater than one. Although the plasma beta is also greater than one on Titan, ion acceleration is expected to be more complex, especially because the subsolar point and the subflow points can be 180 degrees apart. Following what we learned at Venus, upward acceleration of light ions by the polarization electric field opposing gravity in the ionosphere of Titan will be described. Additional electrodynamic forces resulting from the interaction of Saturn's magnetosphere with Titan's ionosphere will be examined using a recent hybrid model.

Hartle, R.; Sittler, E.; Lipatov, A.

2008-01-01

239

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

240

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

NASA Astrophysics Data System (ADS)

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.

1994-09-01

241

Generation mechanisms for magnetosphere-ionosphere current systems deduced from a three-dimensional MHD simulation of the solar wind-magnetosphere-ionosphere coupling processes  

NASA Astrophysics Data System (ADS)

Mechanisms that generate the field-aligned current (FAC) systems in the magnetosphere-ionosphere coupling scheme by virtue of the solar wind-magnetosphere interaction are investigated with a three-dimensional magnetohydrodynamic (MHD) simulation. As a simulation scheme, the finite volume total variation diminishing (TVD) scheme on an unstructured grid system is employed for precise calculations of the ionospheric region. In the ionosphere, the divergence of the Pederson and Hall currents is matched with FAC, mainly assuming uniform conductivity. The present calculation reproduces the traditional region 1 and 2 currents in the polar ionosphere, for both the northward and southward interplanetary magnetic fields (IMFs). The calculated magnitude of the region 1 current becomes large on the dayside, in agreement with observational results. For the northward IMF, NBZ currents that dominate the entire polar cap are obtained, with a maximum on the dayside. This current is totally absent in the southward IMF result. Corresponding to the FACs, the northward IMF results in multicell convection in the polar ionosphere, and the southward IMF results in two-cell convection. On the evening side, the calculated region 1 currents flow almost along the field lines away from the Earth toward the magnetospheric low-latitude boundary layer (LLBL), then flow up the magnetopause across the field lines to high latitudes. The region 1 currents in the morning side are similar but opposite in direction. In the noon-midnight meridian (xz) plane, the main part of the region 1 current passes the tailward side of the cusp in the magnetosphere. The region 1 current converges to a very narrow region in the noon-midnight meridian (xz) plane when the IMF is northward, whereas it passes the noon-midnight meridian (xz) plane diverging to wide regions in the x direction when the IMF is southward. These differences are attributed to the efficient current-driving effect (J dot E less than 0) of the high-latitude boundary layer (HLBL) for the southward IMF. The calculated region 2 currents on the evening (morning) side flow toward (away from) the Earth and close in the inner magnetosphere near the equator. The evening region 2 currents flow azimuthally from the inner boundary of the plasma sheet and show a sharp turn toward the Earth at the ring current region where strong drivers are distributed. For the northward IMF, the NBZ current that flows toward (away from) the evening (morning) polar cap ionosphere is connected with currents in the magnetotail. In the NBZ current loop, there is no remarkable driver or load (J dot E greater than 0). In the evening magnetosphere, the NBZ current that flows into the dayside ionosphere passes the low-latitude side of the NBZ current that flows into the nightside ionosphere, then it turns aside to the outward (+y) direction and turns back before reaching the dayside ionosphere. ionospheric conductivity results in a wedge-current-like structure in the evening side. This result indicates that the current generated in the ionosphere cannot be ignored in the magnetosphere-ionosphere current systems.

Tanaka, T.

1995-07-01

242

Observations of ionosphere/magnetosphere interactions from the Dynamics Explorer satellites  

NASA Technical Reports Server (NTRS)

The Dynamics Explorer program was a dual spacecraft mission designed to study the interactions between the upper atmosphere, ionosphere and magnetosphere. The global auroral images acquired from the high altitude spacecraft have provided a revolutionary new time-dependent frame of reference for the interpretation of data acquired in situ. Using data especially from the low altitude spacecraft, interrelationships are developed between the various electrodynamic parameters measured. Ionospheric irregularities are found to be especially intense in regions of electric field convection shears, which are closely related to the dusk hemisphere field-aligned currents. These region 1 currents are spatially connected to the boundary plasma sheet electron precipitation. At all local times, there appears to be a universal relationship between regions where div E is less than 0 and electron precipitation structures. Depending upon the characteristics of the electrons bombarding the atmosphere, the atmosphere will radiate various spectral optical emissions, which can be imaged from high above the polar caps, with temporal resolution sufficient to follow the time-dependent evolution of a substorm. It is concluded that with further detailed analyses of the electrodynamic parameters obtained from in situ measurements, analyses of auroral images will yield specific information on many of the important ionospheric parameters over an entire auroral oval and polar cap, including regions of intense ionospheric irregularities.

Hoffman, R. A.

1989-01-01

243

Two-dimensional Ionospheric Flow Pattern Associated with Auroral Streamers  

NASA Astrophysics Data System (ADS)

We present direct flow observations and auroral images from the SuperDARN radar and IMAGE WIC imager to investigate the ionospheric flow pattern associated with auroral streamers. For all four cases studied, streamers were ejected from east-west (EW) arcs that initiated from bead-like or small-scale auroral intensifications around the auroral poleward boundary. We find a vortex-like flow pattern with clockwise sense surrounding both the initial auroral forms and the ensuing streamers. The initial eastward flows poleward of the auroral forms and westward flows equatorward of the forms evolved to be roughly equatorward within and to the east of the streamers, and primarily poleward or toward a more poleward direction to the west of the streamers. We also found in three cases signatures of flow bifurcations at the equatorward end of the streamers, which suggests a double vortex-like flow pattern with the counterclockwise one further east of the clockwise one. Our results are consistent with the double-vortex flow structure due to interchange convection associated with a plasma sheet bubble predicted by different numerical simulations, and also provide solid evidence to several previous studies, especially Sergeev et al. [2004]. This indicates that the observed flow pattern may be the ionospheric manifestation of interchange instability in the plasma sheet.

Shi, Y.; Zesta, E.; Lyons, L. R.; Yang, J.; Boudouridis, A.; Ge, Y. S.; Ruohoniemi, J. M.; Mende, S. B.

2011-12-01

244

Role of the atmospheric gravity waves in lithosphere-ionosphere coupling and in generation of the ionospheric earthquake precursors  

NASA Astrophysics Data System (ADS)

Up to the present days there are no well-distinguished physical mechanisms of lithosphere-ionosphere interaction and generation of the ionospheric earthquake precursors. Several hypothetical possibilities have been suggested in the literature: (i) electric currents are generated in the lithosphere during earthquake preparation phase, the electromagnetic emission of these currents influences the ionosphere; (ii) ionosphere responds to the seismogenic variations of air conductivity and related variation of fair-weather electric field; (iii) lithosphere and ionosphere are coupled via middle-scale atmospheric gravity waves (AGW) traveling upwards to the ionospheric heights and producing the effects known as traveling ionospheric disturbances (TID). In spite of great quantity of observations of ionospheric earthquake precursors, there is a lack of appropriate experimental data: such kind of data that will help us to choose between mentioned hypotheses. Our research is devoted to the studying and verification of AGW-mechanism of seismo-ionospheric effects. The original data have been provided by synchronous measurements of atmospheric pressure variations and ionospheric plasma variations carried out in seismically active Chiba area in Japan during the year 2003. Seismogenic AGW with period about 1 hour has been selected from the broad spectra of pressure variations. Correlated ionospheric response has been detected by means of subionospheric VLF/LF propagation. Cross-analysis of barometric and ionospheric parameters has been done in order to recognize the process of AGW-coupling between perturbations at surface and ionospheric levels.

Lizunov, G.; Hayakawa, M.; Hattori, K.; Mayakawa, Sh.

245

Ionospheric imaging in Africa  

NASA Astrophysics Data System (ADS)

ionospheric specification is necessary for improving human activities such as radar detection, navigation, and Earth observation. This is of particular importance in Africa, where strong plasma density gradients exist due to the equatorial ionization anomaly. In this paper the accuracy of three-dimensional ionospheric images is assessed over a 2 week test period (2-16 December 2012). These images are produced using differential Global Positioning System (GPS) slant total electron content observations and a time-dependent tomography algorithm. The test period is selected to coincide with a period of increased GPS data availability from the African Geodetic Reference Frame (AFREF) project. A simulation approach that includes the addition of realistic errors is employed in order to provide a ground truth. Results show that the inclusion of observations from the AFREF archive significantly reduces ionospheric specification errors across the African sector, especially in regions that are poorly served by the permanent network of GPS receivers. The permanent network could be improved by adding extra sites and by reducing the number of service outages that affect the existing sites.

Chartier, Alex T.; Kinrade, Joe; Mitchell, Cathryn N.; Rose, Julian A. R.; Jackson, David R.; Cilliers, Pierre; Habarulema, John-Bosco; Katamzi, Zama; Mckinnell, Lee-Anne; Matamba, Tshimangadzo; Opperman, Ben; Ssessanga, Nicholas; Giday, Nigussie Mezgebe; Tyalimpi, Vumile; Franceschi, Giorgiana De; Romano, Vincenzo; Scotto, Carlo; Notarpietro, Riccardo; Dovis, Fabio; Avenant, Eugene; Wonnacott, Richard; Oyeyemi, Elijah; Mahrous, Ayman; Tsidu, Gizaw Mengistu; Lekamisy, Harvey; Olwendo, Joseph Ouko; Sibanda, Patrick; Gogie, Tsegaye Kassa; Rabiu, Babatunde; Jong, Kees De; Adewale, Adekola

2014-01-01

246

Parametric instabilities as a reason of VLF/ELF plasma turbulence excited in the upper ionosphere by ground based VLF transmitters  

NASA Astrophysics Data System (ADS)

Recently Parrot et al. (2007) reported the results of the DEMETER satellite observations of strong plasma density and temperature perturbations simultaneously with different events in VLF/ELF electrostatic emissions when the satellite orbit crossed the region about 500 km in the diameter above the ground-based VLF transmitters at the height about 800 km. We have shown that during the night estimated electric field (of the transmitter radiated whistler mode (˜ 0.02-0.05 V/m) in the height region ˜ 500-1000 km exceeds the thresholds of the parametric instabilities responsible for excitation pf the lower hybrid waves, particularly three wave decay of the whistler to ion sound and/or lower hybrid/whistler waves, or induced scattering of whistlers to lower hybrid/whistler waves on thermal ions. To our opinion latter processes are responsible for the phenomena observed by the DEMETER satellite. The work is supported by the RFBR grant 06-02-17334. 1. M. Parrot, J.A. Sauvaud, J.J. Berthelier, J.P. Lebreton Strong ionospheric perturbations generated by powerful VLF ground-based transmitters, X International Seminar on "Low frequency processes in the space plasma", Moscow, November, 2007.

Kotik, Dmitry

247

Temperature anisotropies in the terrestrial ionosphere and plasmasphere  

NASA Technical Reports Server (NTRS)

Theoretical work in which the solution of closed sets of transport equations has predicted the existence of temperature anisotropies in the terrestrial ionosphere-plasmasphere system is discussed, considering only thermal (less than 1 eV) particle populations. Various models used to predict ion and electron temperature anisotropies, including kinetic, semikinetic, hydromagnetic, and generalized transport models, predict temperature anisotropies in the polar wind, along plasmapause field lines, during the refilling of the outer plasmasphere after depletion by a magnetic storm, and at F region altitudes in regions of rapid plasma convection. However, only some of the theoretical predictions agree with experimental evidence. Other models predict isotropic temperature distributions in regions where observations indicated the presence of temperature anisotropies.

Demars, H. G.; Schunk, R. W.

1987-01-01

248

Space weather challenges of the polar cap ionosphere  

NASA Astrophysics Data System (ADS)

This paper presents research on polar cap ionosphere space weather phenomena conducted during the European Cooperation in Science and Technology (COST) action ES0803 from 2008 to 2012. The main part of the work has been directed toward the study of plasma instabilities and scintillations in association with cusp flow channels and polar cap electron density structures/patches, which is considered as critical knowledge in order to develop forecast models for scintillations in the polar cap. We have approached this problem by multi-instrument techniques that comprise the EISCAT Svalbard Radar, SuperDARN radars, in-situ rocket, and GPS scintillation measurements. The Discussion section aims to unify the bits and pieces of highly specialized information from several papers into a generalized picture. The cusp ionosphere appears as a hot region in GPS scintillation climatology maps. Our results are consistent with the existing view that scintillations in the cusp and the polar cap ionosphere are mainly due to multi-scale structures generated by instability processes associated with the cross-polar transport of polar cap patches. We have demonstrated that the SuperDARN convection model can be used to track these patches backward and forward in time. Hence, once a patch has been detected in the cusp inflow region, SuperDARN can be used to forecast its destination in the future. However, the high-density gradient of polar cap patches is not the only prerequisite for high-latitude scintillations. Unprecedented high-resolution rocket measurements reveal that the cusp ionosphere is associated with filamentary precipitation giving rise to kilometer scale gradients onto which the gradient drift instability can operate very efficiently. Cusp ionosphere scintillations also occur during IMF BZ north conditions, which further substantiates that particle precipitation can play a key role to initialize plasma structuring. Furthermore, the cusp is associated with flow channels and strong flow shears, and we have demonstrated that the Kelvin-Helmholtz instability process may be efficiently driven by reversed flow events.

Moen, Jøran; Oksavik, Kjellmar; Alfonsi, Lucilla; Daabakk, Yvonne; Romano, Vineenzo; Spogli, Luca

2013-01-01

249

Current-driven plasma waves in the Versatile Toroidal Facility (VTF)  

SciTech Connect

The authors have been conducting laboratory experiments to investigate plasma turbulence that can affect the propagation of electromagnetic waves. This work is aimed at simulating the ionospheric plasma turbulence and cross-checking the radar experiments at Arecibo, Puerto Rico. The large toroidal plasma device, called the Versatile Toroidal Facility (VTF), can produce a radially inhomogeneous plasma imposed in a helically shaped magnetic field. VTF plasma has a sharp density gradient and an intense magnetic field-aligned current, simulating well the plasma environment in the auroral ionosphere. A broad spectrum of plasma waves can be exited in VTF by the injected microwaves and electron beams. In this paper, the authors discuss the excitation of low-frequency plasma waves driven by electric currents, including ion acoustic waves and current-convective modes. A good agreement has been found between the experimental results and the theories developed for the VTF plasmas. However, their experimental results are quite different from those obtained in the rocket/space shuttle experiments. The difference in the laboratory experiments and space experiments arise form two facts. One is that the plasma inhomogeneity does not play a significant role in the space experiments. The other is that the electron beam injected in the space experiments does not produce a drifting Maxwellian plasma as seen in the VTF plasmas. The contrast between the VTF experiments and the active space experiments show that VTF can adequately simulate the ionospheric plasma turbulence and complement the rocket/space shuttle experiments.

Moriarty, D.T.; Lee, M.C.; Riddolls, R.J.; Murphy, S.M.; Rowlands, M.J. [Massachusetts Inst. of Technology, Cambridge, MA (United States). Plasma Fusion Center

1995-12-31

250

Transport Induced by Large Scale Convective Structures in a Dipole-Confined Plasma B. A. Grierson,1,* M. E. Mauel,2  

E-print Network

Transport Induced by Large Scale Convective Structures in a Dipole-Confined Plasma B. A. Grierson,1 transport rates are calculated from density dynamics obtained from multipoint measurements and the reconstructed electrostatic potential. The calculated transport rates determined from the large- scale dynamics

Mauel, Michael E.

251

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

252

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

253

Mid-Latitude Ionospheric Redistribution and Horizontal Flux In The Coupled Geospace System (Invited)  

NASA Astrophysics Data System (ADS)

The plasmasphere boundary layer (PBL) is a region of dynamic interactions between the subauroral ionosphere and the ring current influenced portions of the inner magnetosphere. Within this interaction zone, coupling currents during disturbance times lead to significant cross-field ion flows which can provide an important source of cold ionospheric O+ ions to the noontime cusp region. The delivery of these O+ ions is a hallmark of magnetosphere-ionosphere coupling and may form a critical source for upwelling and/or outflow processes which deliver material detected in the plasma sheet and other magnetospheric regions. We describe statistical and event characterizations of horizontal ion flux in the subauroral American longitude sector using large databases of incoherent scatter radar observations. When combined with satellite measurements of near topside density, GPS total electron content maps, and convection flow patterns using HF radar, the results highlight the crucial role played by the subauroral polarization stream in delivering a regulated horizontal ion flux of more than 1E14 ions/m^2-sec to the cusp. Flux levels have a well defined MLT dependence which is nearly invariant to ring current strength as monitored by the DsT index. Additionally, we will describe several key characteristics of ion fluxes observed near the sunset terminator. In particular, observed cross-field flows oppose corotation in a 2 to 4 hour MLT window, helping to keep SAPS-entrained plasma fixed in an inertial frame.

Erickson, P. J.; Miskin, M. Z.; Beroz, F.; Foster, J. C.

2010-12-01

254

Formation of spiral structures and radial convection in the edge region of a magnetized rotating plasma  

Microsoft Academic Search

The rotation of a cylindrical plasma column in a magnetic field has been studied in the linear section of the new plasma device Mistral. Under suitable conditions we observe a transition to a turbulent regime characterized by strong, bursty fluctuations at the edge of the column. The detection and the study of the spatio-temporal evolution of structures in the turbulent

R. Barni; C. Riccardi; Th Pierre; G. Leclert; A. Escarguel; D. Guyomarc'h; K. Quotb

2005-01-01

255

Assimilative mapping of ionospheric electrodynamics in the thermosphere-ionosphere general circulation model comparisons with global ionospheric and thermospheric observations during the GEM\\/SUNDIAL period of March 28-29, 1992  

Microsoft Academic Search

Satellite and ground-based observations from March 28 to 29, 1992, were combined in the assimilative mapping of ionospheric electrodynamics (AMIE) procedure to derive realistic global distributions of the auroral precipitation and ionospheric convection which were used as inputs to the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere general circulation model (TIGCM). Comparisons of neutral model winds were made with Fabry-Perot

B. A. Emery; G. Lu; E. P. Szuszczewicz; R. G. Roble; P. G. Richards; K. L. Miller; R. Niciejewski; D. S. Evans; F. J. Rich; W. F. Denig; D. L. Chenette; P. Wilkinson; S. Pulinets; K. F. O'Loughlin; R. Hanbaba; M. Abdu; P. Jiao; K. Igarashi; B. M. Reddy

1996-01-01

256

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

257

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

PubMed Central

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

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

2012-01-01

258

Evolution of equatorial ionospheric plasma bubbles and formation of broad plasma depletions measured by the C/NOFS satellite during deep solar minimum  

NASA Astrophysics Data System (ADS)

An unexpected feature revealed by the measurements of the Communication/Navigation Outage Forecasting System (C/NOFS) satellite is the presence of broad plasma depletions in the midnight-dawn sector during deep solar minimum. It has not been well understood what causes the broad plasma depletions and how equatorial plasma bubbles are related to the broad depletions. In this paper we present the C/NOFS measurements of equatorial plasma bubbles and broad depletions in a few cases. The ion density perturbations and enhanced ion vertical velocity are first identified in the topside F region at ˜2200 LT, suggesting that the plasma bubbles start to form earlier at lower altitudes. The observations show that the plasma bubbles observed in the midnight-dawn sector may originate in the evening sector. The plasma bubbles continue growing for more than 3.3 h, and the decay time of the bubbles is also longer than 3.3 h. The continuous growth of the plasma bubbles in the evening sector and the slow decay after midnight determine that most plasma bubbles become fully developed and are easily detected in the midnight-dawn sector. The plasma flow inside the bubbles remains strongly upward throughout the entire nighttime. We propose the following mechanism for the generation of wide plasma bubbles and broad depletions. A series of plasma bubbles is generated through the Rayleigh-Taylor instability process over a large longitudinal range. These plasma bubbles grow and merge to form a wide bubble (width of ˜700 km as observed), and multiple regular and/or wide bubbles can further merge to form broad plasma depletions (thousands of kilometers in longitude). The ion vertical drift inside each plasma bubble is driven by the polarization electric field and remains large after the bubbles have merged. This mechanism provides a reasonable interpretation of the large upward ion drift velocity inside the broad depletion region.

Huang, Chao-Song; de La Beaujardiere, O.; Roddy, P. A.; Hunton, D. E.; Pfaff, R. F.; Valladares, C. E.; Ballenthin, J. O.

2011-03-01

259

Ray trace calculation of ionospheric propagation at lower frequencies  

NASA Astrophysics Data System (ADS)

The Raytrace/Ionospheric Conductivity and Electron Density-Bent-Gallagher model has been revised to make it applicable to ionospheric propagation at low radio frequencies (0.5-5.0 MHz), where the ionosphere and magnetic anisotropy drastically alter propagation paths and provide a severe test of propagation model algorithms. The necessary revisions are discussed, and the model is applied to the problem of ionospheric penetration from a source below the ionosphere to a receiver above the ionosphere. It is necessary to include the electron collision frequency in the Appleton-Hartree index of refraction in order to permit ionospheric penetration for radio frequencies below the maximum plasma frequency (e.g., whistler modes). The associated reformulation of the ray trace equations for a complex index of refraction is straightforward. Difficulties with numerical methods are cited for the lowest frequencies, and future improvements are indicated.

Reilly, Michael H.

2006-10-01

260

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

SciTech Connect

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=As{sup 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, E-mail: sbanerje@ipr.res.in; Ishiguro, M.; Tashima, S.; Mishra, K. [IGSES, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Zushi, H.; Hanada, K.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A.; Nagashima, Y.; Matsuoka, K. [RIAM, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Nishino, N. [Mechanical System Engineering, Hiroshima University, Hiroshima 739-8527 (Japan); Liu, H. Q. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

2014-07-15

261

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

262

Space weather phenomena in the equatorial ionosphere  

NASA Astrophysics Data System (ADS)

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

Bhattacharyya, Archana

2013-03-01

263

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

SciTech Connect

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

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

2013-09-20

264

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

NASA Astrophysics Data System (ADS)

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

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

265

Ionospheric plasma flow about a system of electrically biased flat plates. M.S. Thesis - Cleveland State Univ. Final Report  

NASA Technical Reports Server (NTRS)

The steady state interaction of two electrically biased parallel plates immersed in a flowing plasma characteristic of low earth orbit is studied numerically. Fluid equations are developed to describe the motion of the cold positively charged plasma ions, and are solved using finite-differences in two dimensions on a Cartesian grid. The behavior of the plasma electrons is assumed to be described by the Maxwell-Boltzmann distribution. Results are compared to an analytical and a particle simulation technique for a simplified flow geometry consisting of a single semi-infinite negatively biased plate. Comparison of the extent of the electrical disturbance into the flowing plasma and the magnitude of the current collected by the plate is very good. The interaction of two equally biased parallel plates is studied as a function of applied potential. The separation distance at which the current collected by either plate decreases by five and twenty percent is determined as a function of applied potential. The percent decreases were based on a non-interacting case. The decrease in overall current is caused by a decrease in ionic density in the region between the plates. As the separation between the plates decreases, the plates collect the ions at a faster rate than they are supplied to the middle region by the oncoming plasma flow. The docking of spacecraft in orbit is simulated by moving two plates of unequal potential toward one another in a quasi-static manner. One plate is held at a large negative potential while the other floats electrically in the resulting potential field. It is found that the floating plate does not charge continuously negative as it approaches the other more negatively biased plate. Instead, it charges more and then less negative as ionic current decreases and then increases respectively upon approach. When the two plates come into contact, it is expected that the electrically floating plate will charge rapidly negative to a potential near that of the other plate.

Herr, Joel L.

1993-01-01

266

Strong ionospheric field-aligned currents for radial interplanetary magnetic fields  

NASA Astrophysics Data System (ADS)

The present work has investigated the configuration of field-aligned currents (FACs) during a long period of radial interplanetary magnetic field (IMF) on 19 May 2002 by using high-resolution and precise vector magnetic field measurements of CHAMP satellite. During the interest period IMF By and Bz are weakly positive and Bx keeps pointing to the Earth for almost 10 h. The geomagnetic indices Dst is about -40 nT and AE about 100 nT on average. The cross polar cap potential calculated from Assimilative Mapping of Ionospheric Electrodynamics and derived from DMSP observations have average values of 10-20 kV. Obvious hemispheric differences are shown in the configurations of FACs on the dayside and nightside. At the south pole FACs diminish in intensity to magnitudes of about 0.1 ?A/m2, the plasma convection maintains two-cell flow pattern, and the thermospheric density is quite low. However, there are obvious activities in the northern cusp region. One pair of FACs with a downward leg toward the pole and upward leg on the equatorward side emerge in the northern cusp region, exhibiting opposite polarity to FACs typical for duskward IMF orientation. An obvious sunward plasma flow channel persists during the whole period. These ionospheric features might be manifestations of an efficient magnetic reconnection process occurring in the northern magnetospheric flanks at high latitude. The enhanced ionospheric current systems might deposit large amount of Joule heating into the thermosphere. The air densities in the cusp region get enhanced and subsequently propagate equatorward on the dayside. Although geomagnetic indices during the radial IMF indicate low-level activity, the present study demonstrates that there are prevailing energy inputs from the magnetosphere to both the ionosphere and thermosphere in the northern polar cusp region.

Wang, Hui; Lühr, Hermann; Shue, Jih-Hong; Frey, Harald. U.; Kervalishvili, Guram; Huang, Tao; Cao, Xue; Pi, Gilbert; Ridley, Aaron J.

2014-05-01

267

Midnight reversal of ionospheric plasma bubble eastward velocity to westward velocity during geomagnetically quiettime: Climatology and its model validation  

NASA Astrophysics Data System (ADS)

In an effort to better understand the dynamics of westward velocities of the nocturnal F-region plasma, the climatology of the westward traveling plasma bubbles - WTB - occurring during quiettime is studied here. The climatology of the WTB is analyzed here based on airglow images obtained during 14 quiet days between 2001 and 2006 at the Brazilian station São João do Cariri (Geographic 7.45°S, 36.5°W, dip ˜20°S). The frequency of occurrence of the WTB maximizes in the descending phase of the solar cycle. The WTB velocities ranged between ˜20 and 40 ms-1. The frequency of occurrence had a peak value of only 3.65% at 2345 LT. The maximum occurrence of the WTB was in July-September. No WTB have been observed from November until April in all years 2001-2006. We show for the first time theoretically that the WTB dominant forcing mechanisms during geomagnetically quiet days are westward thermospheric winds.

Sobral, José H. A.; de Castilho, Vivian M.; Abdu, M. A.; Takahashi, Hisao; Paulino, I.; Gasparelo, Ulisses A. C.; Arruda, Daniela C. S.; Mascarenhas, Matheus; Zamlutti, C. J.; Denardini, C. M.; Koga, Daiki; de Medeiros, A. F.; Buriti, R. A.

2011-07-01

268

Solar wind interaction with the ionosphere of Venus inferred from radio scintillation measurements  

Microsoft Academic Search

This paper presents the first S-band (2.3 GHz) radio scintillations observed in the ionosphere of Venus and discovered when the Pioneer Venus Orbiter spacecraft traversed the ionosphere of Venus. In situ plasma measurements as well as propagation calculations confirm that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. While these topside

Richard Woo; William L. Sjogren; A. J. Kliore; J. G. Luhmann; Larry H. Brace

1989-01-01

269

Modeling Ionospheric Variability Based on Long-term Datasets of World Incoherent Scatter Radars  

Microsoft Academic Search

The ionospheric variability, or the deviation from climatological means, is a pronounced and permanent feature of the ionosphere. Understanding variability in the upper atmosphere from various aspects, such as characterization, physical causes and prediction, remains an outstanding problem. As a first step toward such understanding, this paper is to characterize and quantify the ionospheric variability in electron density and plasma

Shunrong Zhang

2008-01-01

270

Magnetosphere sawtooth oscillations induced by ionospheric outflow.  

PubMed

The sawtooth mode of convection of Earth's magnetosphere is a 2- to 4-hour planetary-scale oscillation powered by the solar wind-magnetosphere-ionosphere (SW-M-I) interaction. Using global simulations of geospace, we have shown that ionospheric O(+) outflows can generate sawtooth oscillations. As the outflowing ions fill the inner magnetosphere, their pressure distends the nightside magnetic field. When the outflow fluence exceeds a threshold, magnetic field tension cannot confine the accumulating fluid; an O(+)-rich plasmoid is ejected, and the field dipolarizes. Below the threshold, the magnetosphere undergoes quasi-steady convection. Repetition and the sawtooth period are controlled by the strength of the SW-M-I interaction, which regulates the outflow fluence. PMID:21636770

Brambles, O J; Lotko, W; Zhang, B; Wiltberger, M; Lyon, J; Strangeway, R J

2011-06-01

271

Measurements and Modeling of Ionosphere-Plasmasphere Transport  

Microsoft Academic Search

A fundamental aspect of the coupling between Earth's ionosphere and inner magnetosphere is the flow of ionospheric plasma that supplies material to the plasmasphere. Using global observations of the He+ column abundance made by the IMAGE Extreme Ultraviolet Imager, we investigate refilling of the plasmasphere after erosion events associated with geomagnetic storms. To minimize the confounding effects of phenomena other

B. R. Sandel; M. H. Denton

2005-01-01

272

25 Years of Ionospheric Modification with the Space Shuttle  

NASA Astrophysics Data System (ADS)

The ionosphere is a low temperature (0.1 eV) plasma layer that surrounds the Earth and affects a wide range of radio systems that involve communications, navigation, and radar. The unmodified ionosphere is in an equilibrium state defined by the balance of production, transport and loss of plasma. The modified ionosphere responds to neutral gas injections with (1) the generation and propagation of plasma waves and (2) the production of plasma irregularities. A single 10 second burn of the on-orbit engines on the Space Shuttle injects 1 GJoule of energy into the upper atmosphere. Injection of hypersonic exhaust vapors from rocket engines pushes the ionosphere out of its equilibrium to yield 20 eV ion beams, launch both neutral and plasma waves, and trigger several instability processes. A wide range of optical emissions, plasma density fluctuations, enhanced temperatures, and changes in composition may be detected during these experiments. Multiple sensors such as instrumented satellites, ground radars, and ground optical instruments are used to determine the extent and lifetime for ionospheric modification. This presentation will focus on experimental data and theoretical discussions of the Space Shuttle Orbital Maneuver Subsystem (OMS) Engines used to modify the upper atmosphere from 1985 to the present. Artificial disturbances in the ionosphere produced by OMS burns have two applications. First, the artificial modification of the ionosphere can provide some control on the radio propagation environment. Second, the man-made disturbances are being produced as proxies to natural disturbances.

Bernhardt, P. A.

2011-12-01

273

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

274

The theory of ionospheric focused heating  

NASA Technical Reports Server (NTRS)

Ionospheric modification by high power radio waves and by chemical releases are combined in a theoretical study of ionospheric focused heating. The release of materials which promote electron-ion recombination creates a hole in the bottomside ionosphere. The ionospheric hole focuses high power radio waves from a ground-based transmitter to give a 20 dB or greater enhancement in power density. The intense radio beam excites atomic oxygen by collisions with accelerated electrons. Airglow from the excited oxygen provides a visible trace of the focused beam. The large increase in the intensity of the radio beam stimulates new wave-plasma interactions. Numerical simulations show that the threshold for the two-plasmon decay instability is exceeded. The interaction of the pump electromagnetic wave with the backward plasmon produces a scattered electromagnetic wave at 3/2 the pump frequency. The scattered wave provides a unique signature of the two-plasmon decay process for ground-based detection.

Bernhardt, P. A.; Duncan, L. M.

1987-01-01

275

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

276

Investigation of low-latitude ionospheric irregularities and their relationship to equatorial plasma bubbles using Sanya VHF radar  

NASA Astrophysics Data System (ADS)

A VHF radar has been set up at Sanya (18.34° N, 109.62° E, geomagnetic latitude 7.04°N), China in 2009. On the basis of the E, valley and F region irregularity observations detected by the Sanya VHF radar during equinoctial months, we focus on the simultaneous observations of E region irregularities disruption and valley region irregularities generation during the presence of post-sunset F region bubble structures. We stress that both the low latitude the E region irregularities (ERI) disruption and valley region irregularities (VRI) generation are associated with the development of post-sunset equatorial plasma bubble (EPB) structures. It is suggested that the electric field coupling from the unstable equatorial F region to low-latitude E and valley region could trigger and inhibit the occurrence of irregularities, depending on the polarity of the polarization electric field associated with the bifurcation of equatorial plasma bubbles. The mapping of upward/eastward and downward/eastward electric field associated with the west-tilted and east-tilted bubble structures, may be responsible for the disruption of E region irregularities, and the generation of valley region irregularities, respectively. However, more observations from multi instruments will be required to confirm such a scenario that the multi bifurcated EPBs play crucial roles for the simultaneous occurrence of low latitude ERI disruption and VRI generation.

Ning, B.; Li, G.; Hu, L.

2011-12-01

277

Verification of ionospheric sensors  

Microsoft Academic Search

Ionospheric products from sensors and models were compared to investigate strengths and limitations of each. Total electron content data from computerized ionospheric tomography (CIT) and TOPEX sensors in the Caribbean region in 1997 were compared to estimates produced by models Parameterized Ionospheric Model (PIM) and Raytrace\\/ICED-Bent-Gallagher (RIBG) and global maps from GPS. A 5 total electron content unit (TECU) bias

Clayton Coker; Glenn Kronschnabl; David S. Coco; Gary S. Bust; Thomas L. Gaussiran

2001-01-01

278

Disturbance of midlatitude electrodynamic parameters due to the magnetospheric convection  

NASA Astrophysics Data System (ADS)

Two case studies of ionospheric disturbances in electric fields, currents, and winds during periods of geomagnetic storms detected by incoherent scatter radar are presented. The disturbances are shown to originate from two distinct physical mechanisms: penetration of electric fields to lower latitudes during times of rapid change in magnetospheric convection; and the action of the disturbed ionospheric dynamo driven by storm induced wind disturbances. One storm illustrates penetrative convection electric fields when the Bz component of the interplanetary fields turns southward and northward. The observed events on the following day are clearly identifiable as the delayed response of the disturbance ionospheric dynamo.

Mazaudier, C.

1984-09-01

279

The plasma environment of Uranus  

NASA Technical Reports Server (NTRS)

An overview of the observational results on the plasma environment at Uranus is given, and the implications of these observations for magnetospheric physics at Uranus are discussed. During the Voyager 2 encounter with Uranus, an extended magnetosphere filled with a tenuous plasma was detected. This low-energy plasma was found to consist of protons and electrons, with no significant heavy ion contribution, and with a density in the regions sampled by the spacecraft of at most three electrons per cubic centimeter. The plasma electrons and ions exhibit both a thermal component (with temperatures of tens of eV) and a hot component (with temperatures of a few keV). The thermal ion component is observed both inside and outside an L-shell value near 5, whereas the hot ion and electron component is excluded from the region inside of that L-shell. The source of the thermal component of the plasma is either the planetary ionosphere or the neutral hydrogen corona surrounding Uranus, whereas the hot component is convected in from the magnetotail, with probably an ionospheric source.

Belcher, J. W.; Mcnutt, R. L., Jr.; Richardson, J. D.; Selesnick, R. S.; Sittler, E. C., Jr.; Bagenal, F.

1991-01-01

280

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

E-print Network

to describe large-scale circulation inside the magnetosphere caused by the interaction of the solar wind (SW of geomagnetic field lines in the crossed E and B fields. By analogy with the thermal convection in a non-conductive-latitude, auroral zone. Fig. 1. Regions and currents Fig. 2. Viscous Fig. 3. Magnetic merging Fig. 4. Convection

Michigan, University of

281

Studies of the configuration of the Venus ionospheric magnetic field  

NASA Technical Reports Server (NTRS)

The dayside ionospheric magnetic field of Venus has been modeled from two different points of view. The Cloutier et al. electrodynamic model makes specific predictions about the behavior of the global magnetic field configuration that can be compared with those expected from the alternate diffusion/convection model. Although the diffusion/convection model is currently only one-dimensional, it is found that it is consistent with the observations in several areas where the three-dimensional electrodynamic model is not.

Luhmann, J. G.; Phillips, J. L.; Russell, C. T.

1987-01-01

282

Studies of the configuration of the Venus ionospheric magnetic field  

NASA Astrophysics Data System (ADS)

The dayside ionospheric magnetic field of Venus has been modelled from two different points of view. The Cloutier et al. electrodynamic model makes specific predictions about the behavior of the global magnetic field configuration that can be compared with those expected from the alternate diffusion/convection model. Although the diffusion/convection model is currently only one-dimensional, it is found that it is consistent with the observations in several areas where the 3-dimensional electrodynamic model is not.

Luhmann, J. G.; Phillips, J. L.; Russell, C. T.

283

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

284

HAARP-Induced Ionospheric Ducts  

SciTech Connect

It is well known that strong electron heating by a powerful HF-facility can lead to the formation of electron and ion density perturbations that stretch along the magnetic field line. Those density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents observations of the plasma density perturbations caused by the HF-heating of the ionosphere by the HAARP facility. The low orbit satellite DEMETER was used as a diagnostic tool to measure the electron and ion temperature and density along the satellite orbit overflying close to the magnetic zenith of the HF-heater. Those observations will be then checked against the theoretical model of duct formation due to HF-heating of the ionosphere. The model is based on the modified SAMI2 code, and is validated by comparison with well documented experiments.

Milikh, Gennady; Vartanyan, Aram [University of Maryland, College Park, MD, 20742 (United States)

2011-01-04

285

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

286

Magnetospheric convection at Uranus  

NASA Technical Reports Server (NTRS)

The unusual configuration of the Uranian magnetosphere leads to differences in the relative effects of solar wind induced magnetospheric convection and plasma corotation from those at the other planets. At the present epoch the orientation of the rotation axis of Uranus with respect to the solar wind flow direction leads to a decoupling of the convective and corotational flows, allowing plasma from the tail to move unimpeded through the inner magnetosphere. As Uranus progresses in its orbit around the sun, corotation plays a gradually more important role and the plasma residence times within the magnetosphere increase. When the rotation axis finally becomes perpendicular to the solar wind flow, corotation is dominant.

Selesnick, R. S.

1987-01-01

287

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

288

Solar wind interaction with the ionosphere of Venus inferred from radio scintillation measurements  

NASA Technical Reports Server (NTRS)

The observation of S-band (2.3 GHz) radio scintillations in the ionosphere of Venus by the Pioneer Venus Orbiter is reported. In situ plasma measurements and propagation calculations show that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. It is suggested that these topside plasma irregularities are associated with the penetration of large-scale magnetic fields in the ionosphere. It is found that the disturbed plasma and the scintillations are a manifestation of high-dynamic solar wind interaction with the ionosphere.

Woo, Richard; Sjogren, William L.; Kliore, Arvydas J.; Luhmann, Janet G.; Brace, Larry H.

1989-01-01

289

Ionogram inversion for a tilted ionosphere  

Microsoft Academic Search

Digital ionosondes such as the Dynasonde disclose that the ionosphere is seldom horizontal even when it is plane stratified to a good approximation. The local magnetic dip does not then determine correctly the radiowave propagation angle for inversion of the ionogram to a plasma density profile. The measured echo direction of arrival can be used together with the known dip

J. W. Wright

1990-01-01

290

Low Frequency Rada Sounding Through Martian Ionosphere  

NASA Technical Reports Server (NTRS)

In remote radar sounding, it is highly desirable to operate at low frequencies to improve depth of penetration. For spaceborne sounders, the lowest operating frequency is limited by the effect of the ionosphere due to significant dispersion of the radar waves at near plasma frequency.

Safaeinili, A.; Jordan, R.

2000-01-01

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

Magnetosphere-Ionosphere Coupling Processes in the Ionospheric Trough Region During Substorms  

NASA Astrophysics Data System (ADS)

The ionospheric troughs are regions of remarkable electron density depression at the subauroral and auroral latitudes, and are categorized into the mid-latitude trough or high-latitude trough, depending on their relative location to the auroral oval. Substorms are one fundamental element of geomagnetic activity, during which structured field-aligned currents (FACs) and convection flows develop in the subauroral and auroral ionosphere. The auroral/trough region is expected to experience severe electron density variations during substorms. Accurate specification of the trough dynamics during substorms and understanding its relationship with the structured FACs and convection flows are of important practical purpose, including providing observational foundations for assessing the attendant impact on navigation and communication. In addition, troughs are important since they map to magnetospheric boundaries allowing the remote sensing of magnetosphere-ionosphere coupling processes. In this talk, we discuss the dynamics of the mid-latitude and high-latitude troughs during substorms based on multi-instrument observations. Using GPS total electron content (TEC) data, we characterize the location and width of the mid-latitude trough through the substorm lifecycle and compare them with existing trough empirical models. Using a combination of incoherent scattering radar (ISR), GPS TEC, auroral imager and a data assimilative model, we investigate the relationship between the high-latitude trough and FACs as well as convection flows. The high-latitude trough is found to be collocated with a counter-clockwise convection flow vortex east of the Harang reversal region, and downward FACs as part of the substorm current system are suggested to be responsible for the high-latitude trough formation. In addition, complex ionospheric electron temperature within the high-latitude trough is found, i.e., increase in the E region while decrease in the F region. We discuss possible processes responsible for this complex temperature change, such as ion composition change and/or presence of downward FACs.

Zou, S.; Moldwin, M.; Nicolls, M. J.; Ridley, A. J.; Coster, A. J.; Yizengaw, E.; Lyons, L. R.; Donovan, E.

2013-12-01

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

Radar Ionospheric Impact Mitigation  

Microsoft Academic Search

New ionospheric modeling technology is being developed to improve correction of ionospheric impacts on the performance of ground-based space-surveillance radars (SSRs) in near-real-time. These radars, which detect and track space objects, can experience significant target location errors due to ionospheric delay and refraction of the radar signals. Since these radars must detect and track targets essentially to the radar horizon,

G. Bishop; D. Decker; C. Baker

2006-01-01

295

Dynamic Ionosphere Cubesat Experiment (DICE)  

NASA Astrophysics Data System (ADS)

The Dynamic Ionosphere Cubesat Experiment (DICE) mission has been selected for flight under the NSF "CubeSat-based Science Mission for Space Weather and Atmospheric Research" program. The mission has three scientific objectives: (1) Investigate the physical processes responsible for formation of the midlatitude ionospheric Storm Enhanced Density (SED) bulge in the noon to post-noon sector during magnetic storms; (2) Investigate the physical processes responsible for the formation of the SED plume at the base of the SED bulge and the transport of the high density SED plume across the magnetic pole; (3) Investigate the relationship between penetration electric fields and the formation and evolution of SED. The mission consists of two identical Cubesats launched simultaneously. Each satellite carries a fixed-bias DC Langmuir Probe (DCP) to measure in-situ ionospheric plasma densities, and an Electric Field Probe (EFP) to measure DC and AC electric fields. These measurements will permit accurate identification of storm-time features such as the SED bulge and plume, together with simultaneous co-located electric field measurements which have previously been missing. The mission team combines expertise from ASTRA, Utah State University/Space Dynamics Laboratory (USU/SDL), Embry-Riddle Aeronautical University and Clemson University.

Crowley, G.; Fish, C. S.; Bust, G. S.; Swenson, C.; Barjatya, A.; Larsen, M. F.

2009-12-01

296

Magnetosphere-ionosphere-thermosphere coupling: Effect of neutral winds on energy transfer and field-aligned current  

Microsoft Academic Search

The assimilative mapping of ionospheric electrodynamics (AMIE) algorithm has been applied to derive the realistic time-dependent large-scale global distributions of the ionospheric convection and particle precipitation during a recent Geospace Environment Modeling (GEM) campaign period: March 28-29, 1992. The AMIE outputs are then used as the inputs of the National Center for Atmospheric Research thermosphere-ionosphere general circulation model to estimate

G. Lu; A.D. Richmond; B. A. Emery; R. G. Roble

1995-01-01

297

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

298

IMF B(y) and day-night conductivity effects in the expanding polar cap convection model  

NASA Technical Reports Server (NTRS)

During southward B(z) periods the open field line region in the ionosphere (polar cap) expands due to increased dayside merging. Ionospheric plasma flow patterns result which can be classified by the sign of the interplanetary magnetic field (IMF) B(y) component. In this paper, a time-dependent ionospheric convection model is constructed to simulate these flows. The model consists of a spiral boundary with a gap in it. The sign of the IMF B(y) component determines the geometry of the gap. A potential is applied across the gap and distributed around the boundary. A flow results which enters the polar cap through the gap and uniformly pushes the boundary outward. Results of the model show that B(y) effects are greatest near the gap and virtually unnoticeable on the nightside of the polar cap. Adding a day-night ionospheric conductivity gradient concentrates the polar cap electric field toward dawn. The resulting flow curvature gives a sunward component that is independent of B(y). These patterns are shown to be consistent with published observations.

Moses, J. J.; Gorney, D. J.; Siscoe, G. L.; Crooker, N. U.

1987-01-01

299

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

300

Parameterized study of the ionospheric modification associated with sun-aligned polar cap arcs  

NASA Technical Reports Server (NTRS)

The local ionospheric modification that is due to a generalized steady state solar aligned (SA) arc structure is addressed. For a representative set of SA arc parameters which includes both convection and precipitation, emphasis is placed on the modification by SA polar cap arcs upon the F region electron density and the height integrated conductivity. At low fluxes and low characteristic energies, SA polar cap arcs have the most pronounced relative effect at F region altitudes in darkness for winter solar minimum conditions. The absolute enhancement in summer solar minimum and winter solar maximum is equivalent to that of winter solar minimum, but the higher ambient densities make the relative enhancement less. The TEC enhancement associated with an SA arc may be used to indicate the degree of plasma cross flow across the arc.

Crain, D. J.; Sojka, J. J.; Schunk, R. W.; Zhu, L.

1993-01-01

301

The Pedersen current carried by electrons: Effects on magnetosphere-ionosphere coupling  

NASA Astrophysics Data System (ADS)

Observations by the EISCAT Svalbard radar show that electron temperatures Te in the cusp electrojet reach up to about 4000 K. The heat is tapped and converted from plasma convection in the near Earth space by a Pedersen current that is carried by electrons due to the presence of irregularities and their demagnetising effect. The heat is transfered to the neutral gas by collisions. In order to enhance Te to such high temperatures the maximally possible dissipation at 50 % demagnetisation must nearly be reached. The effective Pedersen conductances are found to be enhanced by up to 60 % compared to classical values. Conductivities and conductances respond significantly to variations of the electric field strength E, and "Ohm's law" for the ionosphere becomes non-linear for large E.

Buchert, Stephan

302

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

303

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

304

Wenchuan Earthquake Ionospheric Precursors: Modeling and Experiment  

NASA Astrophysics Data System (ADS)

Early it was shown, that for strong middle-latitude earthquakes the effects in Total Electron Content (TEC) and in critical frequency of F2-layer (foF2) look like local changes in electron concentration which maxima are located in immediate proximity from epicenter area. Pre-cursory effects of strong near-equatorial earthquakes might be in the form of deepening and widening of electron concentration minimum over the magnetic equator and displacement of equatorial ionization anomaly crests. The problems of physical explanation of possible forma-tion mechanisms of the seismo-ionospheric effects are under discussion now. In Namgaladze et al., 2009 it has been come out with the assumption, that the most probable formation mech-anism of TEC disturbed areas, observable prior strong earthquakes, is the vertical transport of the F2-region ionospheric plasma under the zonal electric field action. The geomagnetic conjugacy of the earthquake ionospheric precursors and effects in equatorial anomaly which development is controlled by zonal electric field are strong arguments in favor of this hypoth-esis. Besides, the analysis of model calculation results with use of the Global Self-consistent Model of the Thermosphere, Ionosphere, Protonosphere (GSM TIP) in Namgaladze et al., 2009 testifies in favor of this hypothesis. There is a question how such electric fields can arise in the ionosphere prior to earthquakes? Now it is not answer to this question. Therefore, for understanding of formation mechanisms of earthquake ionospheric precursors it is necessary to understand the physics of lithosphere-atmosphere-ionosphere coupling prior to earthquake. Many researchers tried to solve this problem. However, until now there is not common opinion concerning to the lithosphere-atmosphere-ionosphere coupling prior to earthquake. Some ba-sic hypotheses for the explanation of this mechanism have been offered: the Internal Gravity Waves (IGWs) of seismogenic origin with the period 1-3 hours, the IGWs with the period from several minutes up to tens minutes, the seismogenic electric field with amplitude from units up to tens mV/m, the abnormal electromagnetic fields and emissions. However, the appearance of local large-scale seismo-ionospheric anomalies in TEC and foF2 it is possible to explain only by two of the mentioned mechanisms: an atmospheric electric field and/or small-scale IGWs. In this study, we present the numerical calculation results for reproduction of observed changes in the ionosphere prior to strong Wenchuan earthquake. This earthquake has been fixed on 12 May 2008. The geomagnetic activity indices for the period on 1-13 May were low. The calcu-lations of Wenchuan earthquake ionospheric precursors were carried out with use of the GSM TIP model. In calculations, the small-scale IGWs and/or the penetration of vertical electric field are considered as the formation mechanisms of earthquake ionospheric precursors. It was carried out the comparison of calculation results with experimental data of TEC and foF2 at various stations, located in China and nearby areas. The obtained results confirm the proposed mechanisms of seismo-ionospheric effect formation by small-scale IGWs and the penetration of the seismogenic vertical electric field from the atmosphere into the ionosphere. References Namgaladze A.A., Klimenko M.V., Klimenko V.V. and Zakharenkova I.E. Physical Mechanism and Mathematical Simulation of Ionosphere Earthquake Precursors Observed in Total Electron Content. Geomagnetism and Aeronomy, 2009, Vol. 49, 252-262.

Klimenko, Maxim; Klimenko, Vladimir; Zhao, Biqiang; Pulinets, Sergej; Zakharenkova, Irina; Bryukhanov, Valerij

305

Solar wind interaction with the ionosphere of Venus inferred from radio scintillation measurements  

SciTech Connect

This paper presents the first S-band (2.3 GHz) radio scintillations observed in the ionosphere of Venus and discovered when the Pioneer Venus Orbiter spacecraft traversed the ionosphere of Venus. In situ plasma measurements as well as propagation calculations confirm that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. While these topside plasma irregularities have not been studied before, simultaneous magnetic field measurements presented here reveal that they are associated with the penetration of large-scale magnetic fields in the ionosphere. Previous studies based on extensive magnetic field measurements have shown that the presence of large-scale magnetic fields occurs in the subsolar region when the solar wind dynamic pressure exceeds the ionospheric plasma pressure. As with the large-scale magnetic fields, the disturbed plasma and resulting scintillations are therefore a manifestation of high-dynamic solar wind interaction with the ionosphere. Since the scintillations only occur in the subsolar region of Venus, the global morphology of ionospheric scintillations at Venus is different from that of the terrestrial ionosphere, where scintillations are observed in both polar and equatorial regions, with peaks occurring during nighttime. This difference apparently stems from the fact that Venus is not a magnetic planet. The authors also demonstrate that the disturbed plasma produced by the high-dynamic solar wind interaction can be remotely sensed by scintillations during radio occultation measurements, that is, when the spacecraft is outside the ionosphere.

Woo, R.; Sjogren, W.L.; Kliore, A.J. (California Institute of Technology, Pasadena (USA)); Luhmann, J.G. (Univ. of California, Los Angeles (USA)); Brace, L.H. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1989-02-01

306

Characteristics of High Latitude Ionosphere Scintillations  

NASA Astrophysics Data System (ADS)

As we enter a new solar maximum period, global navigation satellite systems (GNSS) receivers, especially the ones operating in high latitude and equatorial regions, are facing an increasing threat from ionosphere scintillations. The increased solar activities, however, also offer a great opportunity to collect scintillation data to characterize scintillation signal parameters and ionosphere irregularities. While there are numerous GPS receivers deployed around the globe to monitor ionosphere scintillations, most of them are commercial receivers whose signal processing mechanisms are not designed to operate under ionosphere scintillation. As a result, they may distort scintillation signal parameters or lose lock of satellite signals under strong scintillations. Since 2008, we have established and continuously improved a unique GNSS receiver array at HAARP, Alaska. The array contains high ends commercial receivers and custom RF front ends which can be automatically triggered to collect high quality GPS and GLONASS satellite signals during controlled heating experiments and natural scintillation events. Custom designed receiver signal tracking algorithms aim to preserve true scintillation signatures are used to process the raw RF samples. Signal strength, carrier phase, and relative TEC measurements generated by the receiver array since its inception have been analyzed to characterize high latitude scintillation phenomena. Daily, seasonal, and solar events dependency of scintillation occurrence, spectral contents of scintillation activities, and plasma drifts derived from these measurements will be presented. These interesting results demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations and natural disturbances.

Morton, Y.

2012-12-01

307

Estimation of the High-Latitude Topside Heat Flux Using DMSP In Situ Plasma Densities  

Microsoft Academic Search

The high-latitude ionosphere interfaces with the hot, tenuous, magnetospheric plasma, and a heat flow into the ionosphere is expected, which has a large impact on the plasma densities and temperatures in the high-latitude ionosphere. The value of this magnetospheric heat flux is unknown. In an effort to estimate the value of the magnetospheric heat flux into the ionosphere and, and

H. Bekerat; R. Schunk; L. Scherliess

2005-01-01

308

Vertical drift velocities during the polarization jet observations by the ground-based ionospheric data  

NASA Astrophysics Data System (ADS)

Polarization jet (PJ) or narrow band of rapid westward drift of ionospheric plasma at subauroral latitudes has a horizontal velocity from hundreds of meters to a few kilometers per second. The PJ is clearly identified on the ground-based ionograms as an additional characteristic reflection trace from ionospheric heights. According to the Doppler measurements at the Yakutsk meridian chain of subauroral ionospheric stations the vertical drifts during registration PJ are investigated. It is shown that in periods of PJ observation vertical drift velocity is higher than the background level, and there is a variation of the ionospheric plasma flow direction from the upward to the downward and back.

Bondar, Elena; Stepanov, Alexandr; Khalipov, Victor

309

Assimilation Ionosphere Model: Development and testing with Combined Ionospheric Campaign Caribbean measurements  

NASA Astrophysics Data System (ADS)

Assimilation Ionosphere Model (AIM) is a physics-based, global, ionospheric specification model that is currently under development. It assimilates a diverse set of real-time (or near-real-time) measurements, such as ionograms, GPS slant total electron content (TEC), and in situ plasma measurements. This study focuses on a middle latitude ionosonde assimilation capability in both local and regional forms. The models described are capable of using theƒ0F2 and hmF2 from ionograms to generate either a local or a regional distribution of the induced plasma drift. This induced drift is usually caused by the meridional neutral wind. Results from a local model (AIM1.03L) and a regional model (AIM1.03R) are presented and compared with the international reference ionosphere (IRI) climatological predictions as well as GPS slant TEC measurements. Results from year-long studies during solar maximum show that the accuracy of the AIM1.03L model is about a factor of 2 better than that of IRI. An initial month-long regional study is also presented, and the results are almost as good. A study is also carried out using observations taken during the Combined Ionospheric Campaign (CIC) held in November, 1997, in the Caribbean. The digisonde located at Ramey Solar Observatory is used to drive the AIM1.03L model, and the predicted GPS slant TECs are compared to those observed by a GPS receiver located at St. Croix. This study confirms that this first step in preparing a weather-sensitive ionospheric representation is superior to a climatological representation. This sets the stage for the development of full assimilation of GPS TEC, in situ density measurements, etc., and it is anticipated that the AIM1.03L-R ionospheric representation will provide an accurate ionospheric specification.

Sojka, J. J.; Thompson, D. C.; Schunk, R. W.; Bullett, T. W.; Makela, J. J.

2001-03-01

310

Mantle Convection  

NSDL National Science Digital Library

This page discusses thermal convection as it applies to the Earth's mantle and includes three QuickTime movies for three different cases of convection: heating from below, heating from within, and a combination of the two.

H. Schmeling

311

Particle-in-cell simulations of electron beam instabilities in the ionosphere and implications for ISR spectra  

NASA Astrophysics Data System (ADS)

Incoherent Scatter Radars (ISRs) are powerful tools for studying the Earth's plasma environment. In standard ISR analysis, the received power spectrum is fitted to an analytic model of the reflection from a uniform plasma in thermal equilibrium. This provides estimates of density, temperature, and bulk velocity in the ionospheric plasma. However, these constraints may be readily violated at high latitudes, where the presence of electron and ion beams, magnetic field-aligned currents, and convection electric fields serve to structure the ionospheric plasma on small scales and drive it out of thermal equilibrium. In this work, a plasma particle-in-cell (PIC) code is used to investigate distortions in the ISR spectrum related to electron beam instabilities. To simulate the affected radar volume, an electrostatic PIC code is modified to allow for particle beam injections and multiple boundary conditions (including open boundary). Simulated densities are Fourier-analyzed in time and space to study effects on the ISR spectrum as a function of wavelength of the probing radar. This powerful approach allows the study of complex plasma phenomena in terms of directly observable effects in the received ISR signal. This study focuses on so-called Naturally Enhance Ion-Acoustic Lines (NEIALs), a form of ISR distortion commonly observed in the vicinity of auroral arcs. NEIALs are believed to indicate a destabilization of the plasma caused by precipitating (or injected) electrons. Simulations confirm the parametric decay of Langmuir waves as a plausible mechanism. The spectral distortions are similar at aspect angles as large as +/-15° of the beam direction. The main parameters controlling the decay process are the beam velocity and the ionospheric plasma density, which explains why high frequency radars, such as Sondrestrom, are unable to observe the NEIALs. The simulations also demonstrate the simultaneous enhancement of both ion acoustic shoulders, one of the main features predicted by the electron beam mechanism. Even though the enhancement is clear and defined over specific wavenumbers, simulations show that the enhancement over the ion acoustic line has a white-noise-like spectrum for larger wavenumbers. This could lead to an erroneous estimation of electron density since the effect produces no significant change in either the power or the shape of the spectrum. In addition to the Langmuir decay effect, simulations of the electron beam instability show the appearance of Langmuir wave harmonics. Simulations indicate the first harmonic contains sufficient power to be detected with ISR. Since, the first harmonic appears at large wavenumbers, radars operating at larger wavenumbers could help in the study of NEAILs happening at lower wavenumbers if they are able to detect this plasma mode.

Diaz, Marcos

312

The Ionosphere of Mars: Sources, Variability and Coupling to the Solar Wind  

NASA Astrophysics Data System (ADS)

The ionosphere -thermosphere components of the Mars International Reference Atmosphere (MIRA) represent the upper limits of the planet's atmospheric environment. Above approximately 100 km, the ionospheric domain occurs in a relatively limited altitude region, but one that contains a rich blend of photo- chemical processes and space plasma dynamics. There are two ionospheric layers between 100-150 km, an exosphere that begins near 200 km and an "ionopause" near 350 km that results from the solar wind interaction with ionospheric plasma. The recent discovery of localized magnetic fields (predominately in the southern hemisphere) adds a complexity of ionosphere-magnetosphere-like interactions that needs to be understood. The MIRA Ionospheric Team will be composed of an international group of researchers involved in all aspects of upper atmospheric science at Mars. The proposed effort will involve working with other MIRA groups in the years ahead, and especially with colleagues involved in upcoming satellite missions to Mars.

Mendillo, M.; Kliore, A.

313

The Venus ionosphere  

NASA Technical Reports Server (NTRS)

Physical properties of the Venus ionosphere obtained by experiments on the US Pioneer Venus and the Soviet Venera missions are presented in the form of models suitable for inclusion in the Venus International Reference Atmosphere. The models comprise electron density (from 120 km), electron and ion temperatures, and relative ion abundance in the altitude range from 150 km to 1000 km for solar zenith angles from 0 to 180 deg. In addition, information on ion transport velocities, ionopause altitudes, and magnetic field characteristics of the Venus ionosphere, are presented in tabular or graphical form. Also discussed is the solar control of the physical properties of the Venus ionosphere.

Bauer, S. J.; Brace, L. M.; Taylor, H. A., Jr.; Breus, T. K.; Kliore, A. J.

1985-01-01

314

Jovian magnetosphere-ionosphere current system characterized by diurnal variation of ionospheric conductance  

NASA Astrophysics Data System (ADS)

We developed a new numerical model of the Jovian magnetosphere-ionosphere coupling current system in order to investigate the effects of diurnal variation of ionospheric conductance. The conductance is determined by ion chemical processes that include the generation of hydrogen and hydrocarbon ions by solar EUV radiation and auroral electrons precipitation. The model solves the torque equations for magnetospheric plasma accelerated by the radial currents flowing along the magnetospheric equator. The conductance and magnetospheric plasma then change the field-aligned currents (FACs) and the intensity of the electric field projected onto the ionosphere. Because of the positive feedback of the ionospheric conductance on the FAC, the FAC is the maximum on the dayside and minimum just before sunrise. The power transferred from the planetary rotation is mainly consumed in the upper atmosphere on the dayside, while it is used for magnetospheric plasma acceleration in other local time (LT) sectors. Further, our simulations show that the magnetospheric plasma density and mass flux affect the temporal variation in the peak FAC density. The enhancement of the solar EUV flux by a factor of 2.4 increases the FAC density by 30%. The maximum density of the FAC is determined not only by the relationship between the precipitating electron flux and ionospheric conductance, but also by the system inertia, i.e., the inertia of the magnetospheric plasma. A theoretical analysis and numerical simulations reveal that the FAC density is in proportion to the planetary angular velocity on the dayside and to the square of the planetary angular velocity on the nightside. When the radial current at the outer boundary is fixed at values above 30 MA, as assumed in previous model studies, the peak FAC density determined at latitude 73°-74° is larger than the diurnal variable component. This result suggests large effects of this assumed radial current at the outer boundary on the system.

Tao, Chihiro; Fujiwara, Hitoshi; Kasaba, Yasumasa

2010-02-01

315

Propagation of Extremely Low Frequency Waves Through the Ionosphere  

Microsoft Academic Search

The propagation features of extremely low frequency electromagnetic waves through the multicomponent ionospheric plasma are studied. It is shown that at relatively lower frequencies refractive index for right hand mode is higher than the left-hand mode, which is reversed at higher frequencies. The thermal temperature of plasma particle causes decrease in phase and group velocities of both right and left-hand

Ashok K. Singh; D. Narayan; R. P. Singh

2002-01-01

316

Convective radial energy flux due to resonant magnetic perturbations and magnetic curvature at the tokamak plasma edge  

NASA Astrophysics Data System (ADS)

With the resonant magnetic perturbations (RMPs) consolidating as an important tool to control the transport barrier relaxation, the mechanism on how they work is still a subject to be clearly understood. In this work, we investigate the equilibrium states in the presence of RMPs for a reduced MHD model using 3D electromagnetic fluid numerical code with a single harmonic RMP (single magnetic island chain) and multiple harmonics RMPs in cylindrical and toroidal geometry. Two different equilibrium states were found in the presence of the RMPs with different characteristics for each of the geometries used. For the cylindrical geometry in the presence of a single RMP, the equilibrium state is characterized by a strong convective radial thermal flux and the generation of a mean poloidal velocity shear. In contrast, for toroidal geometry, the thermal flux is dominated by the magnetic flutter. For multiple RMPs, the high amplitude of the convective flux and poloidal rotation are basically the same in cylindrical geometry, but in toroidal geometry the convective thermal flux and the poloidal rotation appear only with the islands overlapping of the linear coupling between neighbouring poloidal wavenumbers m, m - 1, and m + 1.

Marcus, F. A.; Beyer, P.; Fuhr, G.; Monnier, A.; Benkadda, S.

2014-08-01

317

Convective radial energy flux due to resonant magnetic perturbations and magnetic curvature at the tokamak plasma edge  

SciTech Connect

With the resonant magnetic perturbations (RMPs) consolidating as an important tool to control the transport barrier relaxation, the mechanism on how they work is still a subject to be clearly understood. In this work, we investigate the equilibrium states in the presence of RMPs for a reduced MHD model using 3D electromagnetic fluid numerical code with a single harmonic RMP (single magnetic island chain) and multiple harmonics RMPs in cylindrical and toroidal geometry. Two different equilibrium states were found in the presence of the RMPs with different characteristics for each of the geometries used. For the cylindrical geometry in the presence of a single RMP, the equilibrium state is characterized by a strong convective radial thermal flux and the generation of a mean poloidal velocity shear. In contrast, for toroidal geometry, the thermal flux is dominated by the magnetic flutter. For multiple RMPs, the high amplitude of the convective flux and poloidal rotation are basically the same in cylindrical geometry, but in toroidal geometry the convective thermal flux and the poloidal rotation appear only with the islands overlapping of the linear coupling between neighbouring poloidal wavenumbers m, m – 1, and m?+?1.

Marcus, F. A., E-mail: albertus@if.usp.br [Institute of Physics at University of São Paulo, C.P. 66318, 05315-970 São Paulo, S.P. (Brazil); Aix-Marseille Université, CNRS, PIIM UMR 7345, 13397 Marseille Cedex 20 (France); Beyer, P.; Fuhr, G.; Monnier, A.; Benkadda, S. [Aix-Marseille Université, CNRS, PIIM UMR 7345, 13397 Marseille Cedex 20 (France)

2014-08-15

318

Interpre: a Windows software for semiautomatic scaling of ionospheric parameters from ionograms  

Microsoft Academic Search

By analysing an ionogram several important parameters like foF2 and MUF(3000)F2 can be found, that have a significant role in the studies concerning ionospheric physics and related phenomena. Furthermore, the observation of ionospheric plasma and the forecasting of physical phenomena connected to the Sun-Magnetosphere–Ionosphere–Thermosphere system holds a remarkable scientific interest with respect to space weather, because of the influence that

Michael Pezzopane

2004-01-01

319

Electron densities and temperatures in the Venus ionosphere Effects of solar EUV, solar wind pressure and magnetic field  

NASA Technical Reports Server (NTRS)

The Venus ionosphere is influenced by variations in both solar EUV flux and solar wind conditions. On the dayside the location of the topside of the ionosphere, the ionopause, is controlled by solar wind dynamic pressure. Within the dayside ionosphere, however, electron density is affected mainly by solar EUV variations, and is relatively unaffected by solar wind variations and associated magnetic fields induced within the ionosphere. The existence of a substantial nightside ionosphere of Venus is thought to be due to the rapid nightward transport of dayside ionospheric plasma across the terminator. Typical solar wind conditions do not strongly affect this transport and consequently have little direct influence on nightside ionospheric conditions, except on occasions of extremely high solar wind dynamic pressure. However, both nightside electron density and temperature are affected by the presence of magnetic field, as in the case of ionospheric holes.

Elphic, R. C.; Russell, C. T.; Brace, L. H.

1985-01-01

320

Inertial currents in isotropic plasma  

NASA Technical Reports Server (NTRS)

The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasmas, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, MHD plasma. Solutions are developed by taking the MHD limit ot two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

Heinemann, M.; Erickson, G. M.; Pontius, D. H., Jr.

1994-01-01

321

Inertial Currents in Isotropic Plasma  

NASA Technical Reports Server (NTRS)

The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasma, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, MED plasma. Solutions are developed by taking the MHD limit of two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

Heinemann, M.; Erickson, G. M.; Pontius, D. H., Jr.

1993-01-01

322

Inertial currents in isotropic plasma  

NASA Technical Reports Server (NTRS)

The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasma, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, magnetohyrodynamic (MHD) plasma. Solutions are developed by taking the MHD limit of two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

Heinemann, M.; Erickson, G. M.; Pontius, D. H. JR.

1994-01-01

323

Seismo-Ionospheric Precursors  

NASA Astrophysics Data System (ADS)

Large earthquakes are often preceded or accompanied by signals of a different nature: electric, electromagnetic, or luminous, although seismic waves are the most obvious manifestation. Recently, seismo-ionospheric phenomena have received considerable discussions. To investigate possible seismo-ionospheric precursors, we statistically examine the relationship between electron density variations at the ionospheric F2 peak observed by a local ionosonde and 184 earthquakes with magnitude 5.0 or larger, which occurred in 170 days during 1994~1999 in the Taiwan area. Results demonstrate that the electron density abnormally decreases during the afternoon period, 1200~1800 LT, within 5 days before the earthquakes. The odds of the earthquakes with the precursor increasing in the earthquake magnitude but decreasing in the range between the epicenter and the ionosonde confirm the existence of an imminent seismo-ionospheric precursor.

Liu, J.; Chen, Y.; Chuo, Y.

2003-12-01

324

Modeling Ionospheric Electrodynamics (Invited)  

NASA Astrophysics Data System (ADS)

We present modeling results of ionospheric electrodynamics using the 3D NRL ionosphere model SAMI3. Recently, SAMI3 has been upgraded to solve the potential equation that determines the electrostatic potential from the ionospheric conductances (Pedersen and Hall) and drivers: neutral wind, gravity, and parallel current systems. We present results showing the impact of different neutral wind models (e.g., HWM93, HWM07, TIMEGCM) on the dynamics of the low- to mid-latitude ionosphere, as well as the Region 1 and 2 current systems. We point out issues and concerns with obtaining an accurate specification of the global electric field within the context of existing models.(with J. Krall, G. Joyce, S. Slinker, and G. Crowley). Research supported by NASA and ONR

Huba, J. D.

2009-12-01

325

Radar Ionospheric Impact Mitigation  

NASA Astrophysics Data System (ADS)

New ionospheric modeling technology is being developed to improve correction of ionospheric impacts on the performance of ground-based space-surveillance radars (SSRs) in near-real-time. These radars, which detect and track space objects, can experience significant target location errors due to ionospheric delay and refraction of the radar signals. Since these radars must detect and track targets essentially to the radar horizon, it is necessary to accurately model the ionosphere as the radar would observe it, down to the local horizon. To correct for spatial and temporal changes in the ionosphere the model must be able to update in near-real-time using ionospheric sensor data. Since many radars are in isolated locations, or may have requirements to operate autonomously, an additional required capability is to provide accurate ionospheric mitigation by exploiting only sensor data from the radar site. However, the model must also be able to update using additional data from other types of sensors that may be available. The original radar ionospheric mitigation approach employed the Bent climatological model. This 35-year-old technology is still the means employed in the many DoD SSRs today. One more recent approach used capabilities from the PRISM model. PRISM technology has today been surpassed by `assimilative models' which employ better physics and Kalman filtering techniques. These models are not necessarily tailored for SSR application which needs to optimize modeling of very small regions using only data from a single sensor, or very few. The goal is to develop and validate the performance of innovative and efficient ionospheric modeling approaches that are optimized for the small regions applicable to ground-based radar coverage (radius of ~2000 km at ionospheric altitudes) and somewhat beyond. These approaches must adapt a continuous modeling scheme in near-real-time to be consistent with all observational data that may become available, and degrade gracefully toward a climatological representation in the absence of data. In this presentation we will discuss the issues for improving correction of ionospheric impacts on SSRs, some of the capabilities and limitations of current models, and the requirements and goals for new modeling technologies.

Bishop, G.; Decker, D.; Baker, C.

2006-12-01

326

The upper ionospheres of Jupiter and Saturn  

NASA Technical Reports Server (NTRS)

The electron-density profiles of Jupiter's and Saturn's ionospheres are modeled with a 1D chemical diffusive model incorporating measured parameters of the neutral atmospheric structure. The Voyager RSS ion-density data are modeled by accounting for ion chemistry, the H3(+) recombination-rate coefficient, and H2O chemistry. Electron-density peaks for both ionospheres are 900-1000 km lower in the model than the measured values, and the role of vibrational excitation of H2 is discussed in converting H(+) to H2(+) and H3(+). Vertical ion flow is also considered which can maintain the plasma peaks under the conditions of electrical fields or horizontal neutral winds. An assumed influx of H2O molecules of a specific quantity is theorized to reproduce the measured values on Saturn when combined with a vertical plasma drift.

Majeed, Tariq; Mcconnell, John C.

1991-01-01

327

Ionospheric Signatures of Plasmaspheric Tails  

NASA Astrophysics Data System (ADS)

We present direct comparisons between GPS maps of total electron content (TEC) over the North American continent with Millstone Hill radar observations of storm enhanced density and low and high-altitude satellite measurements of the perturbation of the outer plasmasphere during the March 31, 2001 geomagnetic storm. We find that storm enhanced density (SED) [Foster, J. Geophys. Res., 98, 1675, 1993] and plumes of greatly-elevated TEC result from the erosion of the outer plasmasphere by penetration jet electric fields. Boundaries of the SED/TEC plumes identified at low altitude map directly onto the magnetospheric determination of the boundaries of the plasmapause and plasmaspheric tail determined by EUV imaging from the IMAGE spacecraft. Ground-based GPS observations and radar scans are used to present 2-D snapshots of the ionospheric SED, while DMSP overflights identify the magnetospheric boundaries and mechanisms which contribute to these events. During this event, sunward-convecting plumes of high-TEC plasmaspheric material span the continent from New England to the Canadian Yukon and are responsible for significant ionospheric space weather effects including steep TEC gradients [Vo and Foster, J. Geophys. Res., 106, 21555, 2001] and the occurrence of mid-latitude radio scintillation. Characteristics of the SED/TEC plumes/tails for the March 31, 2001 event are. TEC ~100 TECu; F-region (300 km - 1000 km altitude) sunward velocity ~1000 m/s; sunward flux ~ 5*E24 ions s-1. Total transport to dayside magnetopause/merging region (3-hr event) is ~ 5*E28 ions.

Foster, J. C.; Coster, A. J.; Erickson, P. J.; Goldstein, J.; Rich, F. J.

2002-05-01

328

Dayside Ionospheric Superfountain  

NASA Technical Reports Server (NTRS)

The Dayside Ionospheric Super-fountain modified SAMI2 code predicts the uplift, given storm-time electric fields, of the dayside near-equatorial ionosphere to heights of over 800 kilometers during magnetic storm intervals. This software is a simple 2D code developed over many years at the Naval Research Laboratory, and has importance relating to accuracy of GPS positioning, and for satellite drag.

Tsurutani, Bruce T.; Verkhoglyadova, Olga P.; Mannucci, Anthony J.

2010-01-01

329

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

330

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

331

Longitudinal Variability in the Geomagnetically Quiescent Ionosphere  

NASA Astrophysics Data System (ADS)

We report on the effects of nonmigrating tides on the Earth's upper atmosphere based upon calculations made with the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere- mesosphere-electrodynamics general circulation model (TIME-GCM) and global-scale wave model (GSWM). We extend the results reported by Hagan et al. (2007) who demonstrated that longitude variations in IMAGE satellite airglow brightness measurements associated with equatorial ionization anomaly peak densities can be attributed to longitudinally variable nonmigrating zonal wind tides which modulate the E-region dynamo and produce electric field effects that map into the F-region aloft. We explore the local time, altitude and seasonal variability of these nonmigrating tidal components in the TIME-GCM along with viable sources of excitation, including latent heat release associated with raindrop formation in deep convective towers in the tropical troposphere as parameterized in the GSWM. We also assess the reliability of our TIME-GCM predictions via comparison with accessible observations of the quiescent ionosphere. Hagan, M.E., A. Maute, R. G. Roble, A. D. Richmond, T. J. Immel, and S. L. England, (2007), Connections between deep tropical clouds and the Earths ionosphere, Geophys. Res. Lett., in press.

Hagan, M. E.; Maute, A.; Roble, R. G.; Richmond, A. D.

2007-12-01

332

All Ionospheres are not Alike: Reports from other Planets  

NASA Technical Reports Server (NTRS)

Our understanding of planetary ionospheres made some progress during the last four years. Most of this progress was due to new and/or improved theoretical models, although some new data were also obtained by direct and remote sensing observations. The very basic processes such as ionization, chemical transformations and diffusive as well as convective transports are analogous in all ionospheres; the major differences are the result of factors such as different neutral atmospheres, intrinsic magnetic field strength, distance from the Sun, etc. Improving our understanding of any of the ionospheres in our solar system helps in elucidating the controlling physical and chemical processes in all of them. New measurements are needed to provide new impetus, as well as guidance, in advancing our understanding and we look forward to such information in the years ahead.

Nagy, Andrew F.; Cravens, Thomas E.; Waite, H. J., Jr.

1995-01-01

333

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

334

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

335

3246 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, NO. 7, JULY 2012 A 3-D Global Earth-Ionosphere FDTD Model  

E-print Network

to couple FDTD Earth-ionosphere models to other geophysical models, such as the Naval Research Lab's SAMI33246 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, NO. 7, JULY 2012 A 3-D Global Earth-Ionosphere FDTD Model Including an Anisotropic Magnetized Plasma Ionosphere Yaxin Yu, Member, IEEE, Jiajun Niu

Simpson, Jamesina J.

336

Response of topside ionosphere to man-made electromagnetic emissions  

NASA Astrophysics Data System (ADS)

Investigation of electromagnetic measurements in the VLF range, obtained by DEMETER satellite revealed that terrestrial navigational stations are clearly "visible" in the ionosphere. Statistical studies were performed in the frequency range between 10kHz and 20kHz for one component of electric and magnetic field. We used data collected with ICE and IMSC in-struments placed on-board DEMETER. Global maps of man-made emissions show significant ionospheric response. This first satellite from the CNES MYRIADE micro-satellite series was launched on a polar orbit in June 2004 and provides permanent in-situ observations of ionospheric plasma parameters at the altitude of 700 km. As there are now more than five years of operational data a statistical study on both, the bulk ionospheric parameters and electromagnetic emissions, is possible. Since, statistical analysis have shown how easily are detectable man-made signals in the ionosphere, it has implied further studies on other plasma parameters. Using Langmuir probe experiment ISL ("Instrument Sonde de Langmuir") we develop global maps for electron temperature and density. Data are represented in geographic coordinates and averaged over one-month period. We present comparison analysis, that give the statistical background for further studies of noises occurring in the upper layers of ionosphere.

Slominska, Ewa; Rothkaehl, Hanna; Slominski, Jan

337

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

338

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

339

Medium and small-scale ionospheric irregularities detected by GPS radio occultation method  

Microsoft Academic Search

The radio occultation technique is used to study plasma irregularities in the F2 layer ionosphere and below. The data, acquired by the GPS receiver onboard the geophysical research satellite CHAMP for more than three years, allow to study ionospheric irregularities under different geophysical conditions on a global scale. The dual-frequency GPS signals provide a possibility to trace irregularities with a

K. Tsybulya; N. Jakowski

2005-01-01

340

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

341

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

342

Momentum, Heat, and Neutral Mass Transport in Convective Atmospheric Pressure Plasma-Liquid Systems and Implications for Aqueous Targets  

E-print Network

There is a growing interest in the study of plasma-liquid interactions with application to biomedicine, chemical disinfection, agriculture, and other fields. This work models the momentum, heat, and neutral species mass transfer between gas and aqueous phases in the context of a streamer discharge; the qualitative conclusions are generally applicable to plasma-liquid systems. The problem domain is discretized using the finite element method. The most interesting and relevant model result for application purposes is the steep gradients in reactive species at the interface. At the center of where the reactive gas stream impinges on the water surface, the aqueous concentrations of OH and ONOOH decrease by roughly 9 and 4 orders of magnitude respectively within 50 $\\mu$m of the interface. Recognizing the limited penetration of reactive plasma species into the aqueous phase is critical to discussions about the therapeutic mechanisms for direct plasma treatment of biological solutions. Other interesting results fro...

Lindsay, Alexander; Slikboer, Elmar; Shannon, Steven; Graves, David

2015-01-01

343

The solar tidal component SW3 in ionospheric parameters  

NASA Astrophysics Data System (ADS)

In recent years there have been many reports about tidal signatures in the upper atmosphere. Particularly prominent are the wave-4 longitudinal structures which have been related to the eastward propagating tidal component DE3. This tide is believed to be driven by deep tropical convection in the troposphere. In this presentation we will focus on another tidal component, the westward propagating semi-diurnal tide SW3. During certain seasons it can be rather prominent in various ionospheric parameters. Conversely, it does not seem to be important for thermospheric quantities. Lühr et al. (2012) reported for the first time about a dominant SW3 in the tidal spectrum of vertical plasma drift. Later prominent tidal SW3 signals were also found to modulate the intensity of the equatorial electrojet and the longitudinal distribution of the equatorial ionisation anomaly. Closer inspection revealed that the amplitude of SW3 is closely controlled by the level of solar EUV flux, but there is no dependence on magnetic activity. The preferred season for SW3 is around December solstice and a secondary maximum appears during the months around May. All these observations imply that SW3 is not driven by influences from below. We prefer an in-situ mechanism as the cause for the tides, but cannot offer a conclusive explanation at the moment. Lühr, H., M. Rother, K. Häusler, B. Fejer, P. Alken (2012), Direct comparison of non-migrating tidal signatures in the electrojet, vertical plasma drift and equatorial ionization anomaly, J. Atmos. Solar-Terr. Phys., 75-76, 31-43, doi:10.1016/j.jastp.2011.07.009.

Lühr, Hermann; Xiong, Chao; Park, Jaeheung

2014-05-01

344

Self-consistent particle and parallel electrostatic field distributions in the magnetospheric-ionospheric auroral region  

Microsoft Academic Search

The variation of the self-consistent electrostatic potential along the magnetic field is calculated by application of the principle of quasi-neutrality to the plasma components distributed along an auroral field line. The equilibrium plasma consists of hot anisotropic magnetospheric plasma, ionospheric plasma evaporated or extracted upward by the parallel electrostatic field, and backscattered electrons. It is shown that the above charged

Y. T. Chiu; Michael Schulz

1978-01-01

345

Auroral pulsations from ionospheric winds  

NASA Technical Reports Server (NTRS)

The possibility that auroral pulsations are due to oscillatory electrical circuits in the ionosphere that are driven by the negative resistance of jet stream winds is examined. For the condenser plates, the highly conducting surfaces above the edges of the jet stream are postulated. The dielectric constant of the plasma between the plates is quite large. The current that is driven perpendicular to and by the jet stream closes along the plates and through Pedersen currents in the F region above the stream. This closed loop gives the inductance and resistance for the circuit. Periods of oscillation for this circuit appear to be in the range of Pc 1 to Pc 3. In accord with observations, this circuit appears to be able to limit the brightness of pulsations.

Nakada, M. P.

1989-01-01

346

Ionospheric Features Diagnosed by Radio Tomography during Strong Geomagnetic Disturbances  

NASA Astrophysics Data System (ADS)

During the periods of geomagnetic storms, the ionosphere has a particularly complicated and rapidly changing structure. Each storm is marked by its own set of specific manifestations, which reflect rearrangement of the dynamical pattern of the ionosphere and strong perturbations in its parameters. The complexity and global scale of the ionospheric processes that occur during the storms call for the nonlocal methods for diagnosing the spatiotemporal structure of the ionospheric disturbances. Here, we present the results of studying the ionospheric structure by the methods of low orbital radio tomography (RT). The ionospheric radio tomography is rapidly developing during the last two decades. Due to the sufficiently high satellite velocity (~7.9 km/s) and, correspondingly, quite fast (compared to the characteristic times of the ionospheric processes) passage of the satellite through the ionospheric region under study, the radio tomographic approach is suitable for making nearly instantaneous (covering an interval of 5-10 min) 2D snapshots of the ionosphere in the altitude-latitude plane. The vertical and horizontal resolution of RT is 30-40 km and 20-30 km, respectively. We consider the ionospheric manifestations of strong geomagnetic storms (1991-2012) in different regions worldwide including the European part of Russia and North America. We note that during the geomagnetic disturbances, the ionosondes frequently show unstable operation. In contrast to the ionosondes that use HF radio waves, the RT methods are suitable for imaging the ionosphere even during severe solar and geophysical disturbances. During the periods of strong perturbations, RT detected various wavelike structures, travelling ionospheric disturbances, and different manifestations of acoustic gravity waves in the ionosphere. Using the RT methods, the wave effects of particle precipitation were analyzed, and plasma flows were estimated. Radio tomographic imaging of the ionosphere during severe disturbances reveals multiextremal spotty patterns with steep wall-like gradients in electron density in the north. Thin enhancements of electron concentration that are elongated by hundreds of kilometers along the magnetic field lines and attain dozens of kilometers in the transversal direction are identified. The complexly structured ionospheric trough with a tilted polar wall shifted towards the equator is revealed. Many RT reconstructions show the ionospheric trough to split. For example, the RT imaging of the storm of March 24-28, 1991 indicates that the ionospheric structures that are normally typical of the subauroral and auroral ionosphere (the troughs and anomalous ionization in the F-region) reached middle latitudes at that time. During the strongest geomagnetic storm on October 30-31, 2003, the ionosphere over the European part of Russia was marked by anomalously high electron concentration; the distribution of electron density in the region of increased ionization was extremely complicated in space and highly variable in time. We are grateful to the North-West Research Associates (NWRA) for providing the experimental data on relative TEC measured at the RT system in Alaska. The work was supported by the Russian Foundation for Basic Research (grants 11-05-01157 and 13-05-01122).

Andreeva, Elena S.; Kunitsyn, Vyacheslav E.; Tereshchenko, Evgeniy D.; Kozharin, Maksim A.; Nazarenko, Marina O.

2013-04-01

347

Cold Ion Escape from the Martian Ionosphere  

NASA Astrophysics Data System (ADS)

It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. The ion sensor IMA of this experiment has in principle a low-energy cut-off at 10eV but in negative spacecraft charging cold ions are lifted into the range of measurement but the field of view is restricted to about 4x360 deg. In a recent paper Nilsson et al. (Earth Planets Space, 64, 135, 2012) tried to use the method of long-time averaged distribution functions to overcome these constraints. In this paper we first use the same method to show that we get results consistent with this when using ASPERA-3 observations only. But then we can show that these results are inconsistent with observations of the local plasma density by the MARSIS radar instrument on board Mars Express. We demonstrate that the method of averaged distribution function can deliver the mean flow speed of the plasma but the low-energy cut-off does usually not allow to reconstruct the density. We then combine measurements of the cold ion flow speed with the plasma density observations of MARSIS to derive the cold ion flux. In an analysis of the combined nightside datasets we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of about 0.5 Martian radii the flux settles at a constant value which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

Fränz, Markus; Dubinin, Eduard; Andrews, David; Nilsson, Hans; Fedorov, Andrei

2014-05-01

348

First observation of the anomalous electric field in the topside ionosphere by ionospheric modification over EISCAT  

NASA Astrophysics Data System (ADS)

have developed an active ground-based technique to estimate the steady state field-aligned anomalous electric field (E*) in the topside ionosphere, up to ~600 km, using the European Incoherent Scatter (EISCAT) ionospheric modification facility and UHF incoherent scatter radar. When pumping the ionosphere with high-power high-frequency radio waves, the F region electron temperature is significantly raised, increasing the plasma pressure gradient in the topside ionosphere, resulting in ion upflow along the magnetic field line. We estimate E* using a modified ion momentum equation and the Mass Spectrometer Incoherent Scatter model. From an experiment on 23 October 2013, E* points downward with an average amplitude of ~1.6 ?V/m, becoming weaker at higher altitudes. The mechanism for anomalous resistivity is thought to be low-frequency ion acoustic waves generated by the pump-induced flux of suprathermal electrons. These high-energy electrons are produced near the pump wave reflection altitude by plasma resonance and also result in observed artificially induced optical emissions.

Kosch, M. J.; Vickers, H.; Ogawa, Y.; Senior, A.; Blagoveshchenskaya, N.

2014-11-01

349

Martian ionospheric responses to dynamic pressure enhancements in the solar wind  

NASA Astrophysics Data System (ADS)

a weakly magnetized planet, Mars ionosphere/atmosphere interacts directly with the shocked solar wind plasma flow. Even though many numerical studies have been successful in reproducing numerous features of the interaction process, these earlier studies focused mainly on interaction under steady solar wind conditions. Recent observations suggest that plasma escape fluxes are significantly enhanced in response to solar wind dynamic pressure pulses. In this study, we focus on the response of the ionosphere to pressure enhancements in the solar wind. Through modeling of two idealized events using a magnetohydrodynamics model, we find that the upper ionosphere of Mars responds almost instantaneously to solar wind pressure enhancements, while the collision dominated lower ionosphere (below ~150 km) does not have noticeable changes in density. We also find that ionospheric perturbations in density, magnetic field, and velocity can last more than an hour after the solar wind returns to the quiet conditions. The topside ionosphere forms complicated transient shapes in response, which may explain unexpected ionospheric behaviors in recent observations. We also find that ionospheric escape fluxes do not correlate directly with simultaneous solar wind dynamic pressure. Rather, their intensities also depend on the earlier solar wind conditions. It takes a few hours for the ionospheric/atmospheric system to reach a new quasi-equilibrium state.

Ma, Y. J.; Fang, X.; Nagy, A. F.; Russell, C. T.; Toth, Gabor

2014-02-01

350

Research on the lunar ionosphere using dual-frequency radio occultation with a small VLBI antenna  

NASA Astrophysics Data System (ADS)

The Vstar in the Japanese lunar SELENE Radio Science experiment was occulted by virtue of the lunar ionosphere. Using the single sub-satellite and the S/X band coherent radio waves, dual-frequency measurements were acquired at a ground receiving station. In order to investigate the variation of ionospheric total electron content (TEC) surrounding the moon, the TEC, including the terrestrial ionosphere, the interplanetary plasma and lunar ionosphere, can be derived from the phase information of the observational data. We update the observation equation and algorithms, calculate the linear fitting trend of the lunar ionosphere from 60 to 30 km above the surface of the moon. The fitting trend is extended from 30 to 0 km above the surface of the moon. The lunar ionosphere is obtained by using the short time trend extrapolation method.

Wang, Zhen; Wang, Na; Ping, Jinsong

2015-01-01

351

Ionospheric RF lidar  

NASA Astrophysics Data System (ADS)

A new diagnostic consisting of a high-power RF or microwave transmitter and a ground-based lidar system is proposed for probing the ionosphere at heights of 80-200 km. The high-power transmitter creates energetic electrons in the ionosphere, which excite molecules to higher energy levels. These excited molecules become targets for a laser ranging system by resonantly absorbing and reradiating light at specific wavelengths. A laser pulse tuned to a specific transition wavelength is fired from a ground-based laser, and the reradiated light is detected by a ground-based light collector. A study of atmospheric species for ranging was performed, and the most suitable species were found to be N2 and N2(+). A laser whose output is matched exactly to the vibrational-rotational spectrum of ionospheric N2 is proposed as the lidar master oscillator instead of a tunable due laser.

Fukuchi, T.; Wong, A. Y.; Wuerker, R. F.

1990-12-01

352

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

353

Study of plasma convection and wall interactions in magnetic-confinement systems. Progress report, October 1, 1980September 30, 1981  

Microsoft Academic Search

Experimental and analytical studies of plasma interactions with magnetic fields and end walls have been carried out. The final effort for studying flow on open-ended theta pinches has resulted in: (1) new understanding of collisional flow processes; and (2) has presented unique measurements of density and temperature near the end wall. An orignal effort to use Nd-glass lasers for Thomson

T. M. York; E. H. Klevans

1981-01-01

354

Integrated Research Plan April 1, 2008 "Effects of Ionospheric-Magnetospheric  

E-print Network

and at nightside auroral latitudes inject these ionospheric source plasmas outward along magnetic field lines of the solar wind interaction, and is powered mainly by the solar EUV energy absorbed in the F layer [e

Lotko, William

355

Observations of ionospheric magnetospheric coupling - DE and Chatanika coincidences  

NASA Technical Reports Server (NTRS)

Observations from several experiments on board the Dynamics Explorer 1 and 2 (DE 1 and 2) spacecraft and ground-based radar measurements from the Chatanika radar are combined in order to examine the details of ionospheric/magnetospheric coupling in the local evening sector. DE 1 and DE 2 were in coplanar polar orbits that provided measurements almost simultaneously in time and magnetically coincident with the Chatanika radar from L = 3 to L = 17. The coupling processes are inferred from the density, temperature, composition, and angular distributions of the low-energy plasma observed from the E region of the ionosphere to magnetospheric altitudes of 2.5 earth radii. Plasma characteristics of the plasmasphere, main trough, auroral zone, and polar cap can be studied in this data set. The observations imply that as L increases, the dominant coupling mechanism between the ionosphere and magnetosphere in the measured energy range changes from equilibrium diffusion to perpendicular acceleration and finally to parallel acceleration.

Green, J. L.; Brace, L. H.; Waite, J. H.; Chappell, C. R.; Chandler, M. O.; Doupnik, J. R.; Richards, P. G.; Heelis, R.; Shawhan, S. D.

1986-01-01

356

The Ptolemaic Approach to Ionospheric Electrodynamics  

NASA Astrophysics Data System (ADS)

The conventional treatment of ionospheric electrodynamics (as expounded in standard textbooks and tutorial publications) consists of a set of equations, plus verbal descriptions of the physical processes supposedly represented by the equations. Key assumptions underlying the equations are: electric field equal to the gradient of a potential, electric current driven by an Ohm's law (with both electric-field and neutral-wind terms), continuity of current then giving a second-order elliptic differential equation for calculating the potential; as a separate assumption, ion and electron bulk flows are determined by ExB drifts plus collision effects. The verbal descriptions are in several respects inconsistent with the equations; furthermore, both the descriptions and the equations are not compatible with the more rigorous physical understanding derived from the complete plasma and Maxwell's equations. The conventional ionospheric equations are applicable under restricted conditions, corresponding to a quasi-steady-state equilibrium limit, and are thus intrinsically incapable of answering questions about causal relations or dynamic developments. Within their limited range of applicability, however, the equations are in most cases adequate to explain the observations, despite the deficient treatment of plasma physics. (A historical precedent that comes to mind is that of astronomical theory at the time of Copernicus and for some decades afterwards, when the Ptolemaic scheme could explain the observations at least as well if not better than the Copernican. Some of the verbal descriptions in conventional ionospheric electrodynamics might be considered Ptolemaic also in the more literal sense of being formulated exclusively in terms of a fixed Earth.) I review the principal differences between the two approaches, point out some questions where the conventional ionospheric theory does not provide unambiguous answers even within its range of validity (e.g., topside and bottomside boundary conditions on electrodynamics), and illustrate with some simple examples of how a neutral-wind dynamo really develops.

Vasyliunas, V. M.

2010-12-01

357

One-dimensional multispecies hydrodynamic models of the wakeside ionosphere of Titan  

Microsoft Academic Search

The passage of Voyager 1 through the wakeside region of Titan's ionosphere provided an interesting probe of this plasma environment. A one-dimensional multispecies hydrodynamic model was developed to study the wakeside ionosphere for radial distances ranging from 1.3 to 4.5 RT and included the ion species H2CN(+), Cn Hm(+), C2H5(+), CH5(+), H(+), H2(+), and H3(+). Plasma transport only along magnetic

C. N. Keller; T. E. Cravens

1994-01-01

358

Observations of Midlatitude Ionospheric  

Microsoft Academic Search

Using data from the available networks of GPS receivers (CORS and FAA WAAS), observations of rapid drops in TEC (as much as 14 meters of ionospheric delay or 84 TECu within 100 seconds) have been observed in mid-latitudes during major geomagnetic storms. Investigations of these TEC drops have suggested that the drops were due to what appeared to be \\

T. F. Dehel; A. J. Mannucci; A. Komjathy; X. Pi

2004-01-01

359

Seismo-Ionospheric Phenomena  

NASA Astrophysics Data System (ADS)

Ionospheric F-region disturbances and anomalous foEs increases were separately observed within a few days before two great earthquakes in geomagnetic and solar quiet conditions. The ionospheric foF2 decreased from its monthly median at Wakkanai, 290 km north of the epicenter from 3 days before the M 7.8 earthquake onset of July 12, 1993 in the northern Japan to 3 days after it. Anomalous foEs increases above 7 MHz were observed at Shigaraki, 100 km northeast of the epicenter in the daytime on January 15, 1995 before the M 7.2 Hyogoken-nambu earthquake onset of January 17, 1995. The F-region disturbances before the earthquake is discussed in terms of the ionospheric vertical movements caused by a seismo electric field on the assumption of the global ionosphere-earth seismo current system. The anomalous foEs increases before the earthquake onset could be, caused by unknown super-volt seismo discharges since there was no thunderstorm cloud over the observatories

Ondoh, Tadanori

360

The Venus ionosphere  

Microsoft Academic Search

Physical properties of the Venus ionosphere obtained by experiments on the US Pioneer Venus and the Soviet Venera missions are presented in the form of models suitable for inclusion in the Venus International Reference Atmosphere. The models comprise electron density (from 120 km), electron and ion temperatures, and relative ion abundance in the altitude range from 150 km to 1000

S. J. Bauer; L. M. Brace; H. A. Taylor Jr.; T. K. Breus; A. J. Kliore

1985-01-01

361

The Dayside Ionospheric \\  

Microsoft Academic Search

Prompt penetration electric fields (PPEFs) and the consequential dayside ionospheric superfountain (DIS) are reviewed. An example of O + uplift to ~840 km altitude at ~0940 local time (DMSP F15) during the superstorm of 30 October 2003 is illustrated. The SAMI-2 model is modified to incorporate intense superstorm electric fields. With an inclusion of a ~4 mV\\/m eastward electric field,

B. T. Tsurutani; A. Saito; O. P. Verkhoglyadova; A. J. Mannucci; M. A. Abdu; T. Araki; W. D. Gonzalez; T. Tsuda; K. Yumoto

2006-01-01

362

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

363

Plasmasphere-ionosphere coupling. II - Ion composition measurements at plasmaspheric and ionospheric altitudes and comparison with modeling results  

NASA Technical Reports Server (NTRS)

This paper presents Dynamic Explorer data on the plasma coupling between the plasmasphere and ionosphere. DE 1 measurements of ion composition and temperatures at 1.4-3.5 R(F) in the plasmasphere were combined with DE-2 measurements of ion composition and electron and ion temperatures in the upper F region/topside ionosphere, closely spaced in universal and local time for cases in the November 6-11, 1981 period. The observations are compared directly with the field-line interhemispheric plasma (FLIP) model calculations of altitudinal ion density and temperature profiles. It was found that, when the FLIP model permitted fractional trapping of ionospheric photoelectrons and consequent plasmaspheric heating, good agreement with the observations was obtained.

Horwitz, J. L.; Comfort, R. H.; Richards, P. G.; Chandler, M. O.; Chappell, C. R.; Anderson, P.; Hanson, W. B.; Brace, L. H.

1990-01-01

364

ASPERA/Phobos measurements of the ion outflow from the Martian ionosphere  

NASA Astrophysics Data System (ADS)

This report reviews the first results on the ionospheric ion outflow in the Martian magnetosphere by the Automatic Space Plasma Experiment with a Rotating Analyzer ion composition experiment on Phobos-2. The measurements show that Mars is characterized by a strong loss of plasma from its topside ionosphere. A preliminary estimate of the ionospheric outflow from Mars indicates that the planet at present is losing oxygen at a rate of about 3 x 10 to the 25th ions/s. This corresponds to an evacuation of its present total atmospheric oxygen content in less than 100 million years.

Lundin, R.; Zakharov, A.; Pellinen, R.; Barabasj, S. W.; Borg, H.; Dubinin, E. M.; Hultqvist, B.; Koskinen, H.; Liede, I.; Pissarenko, N.

1990-05-01

365

Development and error analysis of nonlinear ionospheric removal algorithm for ionospheric electron density determination using broadband RF data  

NASA Astrophysics Data System (ADS)

The first documented, empirical comparisons are provided of four methods to retrieve total electron content (TEC) that use broadband, impulsive events detected by satellite in the lower very high frequency range (20-150 MHz). The four TEC retrieval methods are the quasi-longitudinal approximation (i.e., Taylor expansion) of the Appleton-Hartree (A-H) dispersion relation to the first and second orders, as well as the nonlinear ionospheric removal algorithm (NIRA) that utilizes the A-H dispersion equation directly to model the propagation of an electromagnetic wave through the ionosphere. NIRA solves not only for TEC between the ground source and satellite, but also for higher-order ionospheric terms, such as electron density, ionospheric thickness, and angle between wave vector and magnetic field. Regimes of validity for each TEC retrieval method are analyzed by comparison of the parameters retrieved from synthetic data with a known ionosphere and from RF FORTE satellite data measurements of a ground-based broadband transmitter. Results include a comparison between TEC and infinite frequency time of arrival (to) determined by NIRA and determined by using the first- and second-order terms from the Taylor expansion of the A-H equation. Plasma density, ionospheric thickness, and angle between magnetic field and wave vector as determined by the two NIRA methods are also compared.

Lay, E. H.; Close, S.; Colestock, P.; Bust, G.

2011-02-01

366

High-latitude ionospheric electrodynamics as determined by the assimilative mapping of ionospheric electrodynamics procedure for the conjunctive SUNDIAL\\/ATLAS 1\\/GEM period of March 28–29, 1992  

Microsoft Academic Search

During the conjunctive SUNDIAL\\/ATLAS 1\\/GEM campaign period of March 28-29, 1992, a set of comprehensive data has been collected both from space and from ground. The assimilative mapping of ionospheric electrodynamics (AMIE) procedure is used to derive the large-scale high-latitude ionospheric conductivity, convection, and other related quantities, by combining the various data sets. The period was characterized by several moderate

G. Lu; B. A. Emery; A. S. Rodger; M. Lester; J. R. Taylor; D. S. Evans; J. M. Ruohoniemi; W. F. Denig; O. de la Beaujardière; R. A. Frahm; J. D. Winningham; D. L. Chenette

1996-01-01

367

High-latitude ionospheric electrodynamics as determined by the assimilative mapping of ionospheric electrodynamics procedure for the conjunctive SUNDIAL\\/ATLAS 1\\/GEM period of March 28-29, 1992  

Microsoft Academic Search

During the conjunctive SUNDIAL\\/ATLAS 1\\/GEM campaign period of March 28-29, 1992, a set of comprehensive data has been collected both from space and from ground. The assimilative mapping of ionospheric electrodynamics (AMIE) procedure is used to derive the large-scale high-latitude ionospheric conductivity, convection, and other related quantities, by combining the various data sets. The period was characterized by several moderate

G. Lu; B. A. Emery; A. S. Rodger; M. Lester; J. R. Taylor; D. S. Evans; J. M. Ruohoniemi; W. F. Denig; O. de la Beaujardière; R. A. Frahm; J. D. Winningham; D. L. Chenette

1996-01-01

368

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

Stephane Labrosse

369

Structure of Titan's ionosphere: Model comparisons with Cassini data  

NASA Astrophysics Data System (ADS)

Solar extreme ultraviolet and X-ray radiation and energetic plasma from Saturn's magnetosphere interact with the upper atmosphere producing an ionosphere at Titan. The highly coupled ionosphere and upper atmosphere system mediates the interaction between Titan and the external environment. New insights into Titan's ionosphere are being facilitated by data from several instruments onboard the Cassini Orbiter, although the Ion and Neutral Mass Spectrometer (INMS) measurements will be emphasized here. We present dayside ionosphere models and compare the results with both Radio and Plasma Wave-Langmuir Probe (RPWS/LP) and INMS data, exploring the sensitivity of models to ionospheric chemistry schemes and solar flux variations. Modeled electron densities for the dayside leg of T18 and all of T17 (dayside) had reasonable agreement with the measured RPWS electron densities and INMS total ion densities. Magnetospheric inputs make at best minor contributions to the ionosphere for these flybys, at least for altitudes above about 1000 km. At lower (<1100 km) altitudes, the total ion densities measured by the INMS are less than the electron densities measured by the RPWS/LP which could be due to heavy (>100 daltons) ions, which the INMS is not able to detect. Qualitatively, INMS spectra exhibit the same ion species and 12 amu family separations for the dayside ionospheres of T17 and T18 as were seen in the mass spectra measured during T5 (nightside). However, the relative abundance of high-mass ( m>50) ion species is about 10 times less for the dayside T17 and T18 passes than it was for the polar nightside T5 flyby, which can perhaps be explained in several ways including differences in neutral composition, less dissociative recombination on the nightside than on the dayside (due to lower electron densities and affecting heavier ion species more than lighter ones), and transport of longer-lived high-mass species from day-to-night.

Robertson, I. P.; Cravens, T. E.; Waite, J. H.; Yelle, R. V.; Vuitton, V.; Coates, A. J.; Wahlund, J. E.; Ågren, K.; Mandt, K.; Magee, B.; Richard, M. S.; Fattig, E.

2009-12-01

370

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

371

Broadband meter-wavelength observations of ionospheric scintillation  

NASA Astrophysics Data System (ADS)

Intensity scintillations of cosmic radio sources are used to study astrophysical plasmas like the ionosphere, the solar wind, and the interstellar medium. Normally, these observations are relatively narrow band. With Low-Frequency Array (LOFAR) technology at the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) station in northern Finland we have observed scintillations over a three-octave bandwidth. "Parabolic arcs," which were discovered in interstellar scintillations of pulsars, can provide precise estimates of the distance and velocity of the scattering plasma. Here we report the first observations of such arcs in the ionosphere and the first broadband observations of arcs anywhere, raising hopes that study of the phenomenon may similarly improve the analysis of ionospheric scintillations. These observations were made of the strong natural radio source Cygnus-A and covered the entire 30-250 MHz band of KAIRA. Well-defined parabolic arcs were seen early in the observations, before transit, and disappeared after transit although scintillations continued to be obvious during the entire observation. We show that this can be attributed to the structure of Cygnus-A. Initial results from modeling these scintillation arcs are consistent with simultaneous ionospheric soundings taken with other instruments and indicate that scattering is most likely to be associated more with the topside ionosphere than the F region peak altitude. Further modeling and possible extension to interferometric observations, using international LOFAR stations, are discussed.

Fallows, R. A.; Coles, W. A.; McKay-Bukowski, D.; Vierinen, J.; Virtanen, I. I.; Postila, M.; Ulich, Th.; Enell, C.-F.; Kero, A.; Iinatti, T.; Lehtinen, M.; Orispää, M.; Raita, T.; Roininen, L.; Turunen, E.; Brentjens, M.; Ebbendorf, N.; Gerbers, M.; Grit, T.; Gruppen, P.; Meulman, H.; Norden, M. J.; de Reijer, J.-P.; Schoenmakers, A.; Stuurwold, K.

2014-12-01

372

Response of topside ionosphere to man-made electromagnetic emissions  

NASA Astrophysics Data System (ADS)

Investigation of electromagnetic measurements in the VLF range, obtained by DEMETER satellite revealed that terrestrial navigational stations are clearly "visible" in the ionosphere. Statistical studies were performed in the frequency range between 10kHz and 20kHz for one component of electric and magnetic field. We used data collected with ICE and IMSC instruments placed on-board DEMETER. This first satellite from the CNES MYRIADE micro-satellite series was launched on a polar orbit in June 2004 and provides permanent in-situ observations of ionospheric plasma parameters at the altitude of ~700 km. As there are now more than five years of operational data a statistical study on both, the bulk ionospheric parameters and electromagnetic emissions, is possible. Since, statistical analysis have shown how easily are detectable man-made signals in the ionosphere, it has implied further studies on other plasma parameters. Using Langmuir probe experiment ISL ("Instrument Sonde de Langmuir") we develop global maps for electron temperature and density. Data are represented in geographic coordinates and averaged over one-month period. We present comparison analysis, that give the statistical background for further studies of noises occurring in the upper layers of ionosphere.

Slominska, Ewa; Rothkaehl, Hanna; Slominski, Jan; Wiktorowicz, Grzegorz

2010-05-01

373

Ionospheric mid-latitude response to solar wind discontinuities  

NASA Astrophysics Data System (ADS)

We have compiled a database of 356 discontinuities detected by both the Advanced Composition Explorer ACE) and Cluster satellites in the solar wind between 2001-2012 and analyzed their ionospheric response. Each discontinuity of the data base is defined by a change of at least 5 nT in less than 5 min in one or more components of the interplanetary magnetic field (IMF). The discontinuities are observed in January-April every year, when Cluster enters the solar wind. The ionospheric effects of solar wind discontinuities are investigated by checking the variations of critical frequencies foF2, the heights of the F layer and the ionospheric plasma dynamics recorded using ground measurement with a time resolution of 15 minutes from mid-latitude digisondes located in Czech Republic. The time delay between solar wind input and the ionospheric response is analyzed using the characteristics and the shape of the ionograms. The geoeffectiveness of the solar wind discontinuities is expressed as correlation between key plasma parameters (e,g, the solar wind velocity, magnetic jump across the discontinuity) and the ionospheric variations. Solar cycle effects are also discussed.

Munteanu, Costel; Mosna, Zbysek; Kouba, Daniel; Echim, Marius

2013-04-01

374

The fine structure of 'caviton' signal scattered by modified ionosphere  

Microsoft Academic Search

The results of experimental study of the spatial and temporal characteristics of ``caviton'' signal (CS) (narrow-band one), scattered by artificially disturbed ionospheric plasma under its sounding by short probing radio pulses are presented. At the heating facilities ``Zimenki'' and ``Sura'' the registration of the time dependencies of CS amplitude and phase at the different virtual heights of scattering with different

G. I. Terina

2004-01-01

375

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 106, NO. A2, PAGES 1771-1783, FEBRUARY 1, 2001 Radar studies of midlatitude ionospheric plasma drifts  

E-print Network

periods. We presentinitially a local time, season, and solar flux dependent analytical model of the quiet Santin drift patterns during solar maximum. We have usedthese quiet time modelsto extract analyticalseasonal model of their quiet time F region plasma drifts. This model included a steady drift componentand

Paris-Sud XI, Université de

376

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

377

Study of the ionospheric variability within the Euro-Asian sector during the Sundial/Atlas 1 mission  

NASA Astrophysics Data System (ADS)

In order to quantify, and to identify possible origins of, subauroral ionospheric variability during periods of moderate geomagnetic activity, ionospheric observations taken during the SUNDIAL/ATLAS-1 campaign (March 24 to April 2) from 10 stations were analyzed in conjunction with observations from EISCAT, geomagnetic observations from magnetometer networks in Scandinavia and the United Kingdom, and auroral particle energy input observations from the NOAA-12 satellite. The network of ionospheric stations spanned longitudes from 13°E to 90°E but were relatively confined in geomagnetic latitudes so that longitudinal and local time dependencies in ionospheric variability are more clearly exposed. The ionospheric observations were analyzed in terms of both ?f0F2, the difference between the hourly f0F2 at a given station and the monthly median f0F2 for that hour, and a new daily variability index Af0F2. The analysis using both parameters demonstrated an apparent longitudinal variation in ionospheric variability with a reversal at about 55°E from a negative to a positive phase in the departure of ionospheric conditions from their median values. An analysis of these ionospheric data in conjunction with the NOAA/TIROS estimates of power deposition by auroral particles demonstrated a significant local time dependence in midlatitude ionospheric responses to auroral activity. This dependence may arise from the premidnight to postmidnight asymmetry in high-latitude convection electric fields.

Pulinets, S. A.; Yudakhin, K. F.; Evans, D.; Lester, M.

1996-12-01

378

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

379

The Tordo 1 polar cusp barium plasma injection experiment  

NASA Technical Reports Server (NTRS)

In January 1975, two barium plasma injection experiments were carried out with rockets launched into the upper atmosphere where field lines from the dayside cusp region intersect the ionosphere. The Tordo 1 experiment took place near the beginning of a worldwide magnetic storm. It became a polar cap experiment almost immediately as convection perpendicular to the magnetic field moved the fluorescent plasma jet away from the cusp across the polar cap in an antisunward direction. Convection across the polar cap with an average velocity of more than 1 km/s was observed for nearly 40 min until the barium flux tubes encountered large electron fields associated with a poleward bulge of the auroral oval near Greenland. Prior to the encounter with the aurora near Greenland there is evidence of upward acceleration of the barium ions while they were in the polar cap. The three-dimensional observations of the plasma orientation and motion give an insight into convection from the cusp region across the polar cap, the orientation of the polar cap magnetic field lines out to several earth radii, the causes of polar cap magnetic perturbations, and parallel acceleration processes.

Wescott, E. M.; Stenbaek-Nielsen, H. C.; Davis, T. N.; Jeffries, R. A.; Roach, W. H.

1978-01-01

380

Gravity Waves in the Thermosphere/Ionosphere simulated by a Whole Atmosphere Model  

NASA Astrophysics Data System (ADS)

Behaviors of gravity waves in the thermosphere/ionosphere are examined by using a whole atmosphere-ionosphere coupled model, GAIA. The dominant period of thermospheric gravity waves simulated by the GAIA becomes shorter at higher altitudes due to dissipation processes in the thermosphere, such as molecular viscosity and ion drag force, indicating that gravity waves with a larger horizontal phase velocity (larger vertical wavelength) can penetrate into the thermosphere. We also investigate the longitudinal and seasonal variations of gravity wave activity in low latitudes and upward propagation of gravity waves from the lower atmosphere to the thermosphere/ionosphere. Our results clearly indicate that the longitudinal variation of the gravity wave activity in the thermosphere is closely related to the cumulus convective activity in the tropics. Furthermore, we investigate effects of thermospheric gravity waves on the ionospheric variability.

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

2012-12-01

381

Impact of geomagnetic storm on fine and global structures of the ionosphere  

NASA Astrophysics Data System (ADS)

We have analyzed Demeter micro-satellite data, in particular from ISL, IAP and ICE experiments to study 3 magnetic storm events on January 2005: 7-8, 17-19 and 21-22. The most direct impact on ionosphere is situated at auroral zone but it also affects the dynamics of the ionosphere-thermosphere system at lower latitudes. In effect one can observe changes in the plasma parameters on the global scale. In this study we have analyzed plasma processes related to magnetic storm events and their impact on large scale ionospheric structures such as ionospheric trough. The aim of this study was to establish relation between large scale plasma inhomogeneities and small scale processes. We have produced diurnal global maps for electron density and temperature, ion temperature and ion concentrations. We also analyzed dynamics of the electric field distribution at ULF, ELF, VLF frequency ranges.

Przepiorka, D.; Gromadzki, M.; Grzesiak, M.; Slominska, E.; Rothkaehl, H.; Space Plasma Group

2011-12-01

382

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

383

A semi-empirical low-latitude ionospheric model  

Microsoft Academic Search

A computationally fast semiempirical low-latitude ionospheric model (SLIM) is developed which more realistically describes the daytime plasma density scale-height and total electron content (TEC) values. Electron density profiles are theoretically determined as a function of latitude and local time by solving the time-dependent plasma continuity equation, and they are reproduced via sets of coefficients which are generated by simple exponential

David N. Anderson; Michael Mendillo; Bruce Herniter

1987-01-01

384

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

385

Long-term Scintillations in the Dayside Cusp and Polar Cap Locations and its Impact on Trans-ionospheric Satellite Communication Links at VHF  

NASA Astrophysics Data System (ADS)

This study provides the first long-term scintillation statistics at 250 MHz from 2000-2005 at the cusp at two longitudes, namely in Sondrestorm, Greenland and in NyAlesund, Svalbard, the former remaining in sunlight during winter whereas the latter is in darkness. The interpretation of statistics at these stations are, however, quite complex since the quasi-stationary satellites observed, combined with the observing geometry, yield a data base in which different magnetic latitude ranges (polar, auroral and sub-auroral) are explored during different times of day and seasons with no easy way to separate these variables. Ionospheric plasma from midlatitudes entering the dayside cusp region are structured through shear flows or gradient drift instability mechanisms and during the passage of the plasma through the central polar cap the anti-sunward convection continually structures the plasma by the gradient drift instability mechanism until it transits into the nightside auroral oval. The structured plasma scatters signals from satellites and introduces scintillations of signal amplitude and degrades the quality of a communication link. Overall, maximum scintillation occurrence at the cusp is observed at the two equinoxes and the December solstice with the minimum occurrence noted in Jun-July. In addition, both the magnitude of scintillation and percent occurrence decline with declining sunspot number. Earlier, long-term statistics for Thule, a polar cap location, were shown in Basu et al. (Radio Sc., 1988). Though the peak sunspot values of solar cycle 23 are lower than those in the 1979 time period, there is favorable comparison of scintillation occurrence and seasonal variability for similar sunspot periods at Thule. The study provides a quantitative measure of degradation in satellite to ground or satellite to aircraft communication links at VHF in the polar region due to structured ionospheric plasma.

MacKenzie, E.; Basu, S.; Pedersen, T. R.

2010-12-01

386

Natural hazards monitoring and forecast using the GNSS and other technologies of the ionosphere monitoring  

NASA Astrophysics Data System (ADS)

It is well established now that Atmosphere-Ionosphere Coupling is provided through the local changes of the Global Electric Circuit parameters. Main agent - is column conductivity, modulated mainly at the altitudes of the Global Boundary Layer. We demonstrate the ionospheric effects for different types of natural hazards including volcano eruptions, dusty storms from Western Africa, ionospheric effects from tropical hurricanes, multiple earthquakes. We consider the important role of air ionization from natural (natural ground radioactivity and galactic cosmic rays) and artificial sources (nuclear weapon tests in atmosphere and underground, nuclear power stations and other nuclear enterprises emergencies). We rise also important question that such effects of the ionosphere variability are not taken into account by any ionospheric model and their correct recognition is important not only from the point of view the disasters monitoring but for navigation itself because the magnitude of the ionospheric effects sometimes exceeds the effects from strong magnetic storms and other severe space weather conditions. Some effects like ionospheric effects from tropical hurricanes have more complex physical nature including the formation of streams of neutral atmosphere over the hurricane eye and formation of the strong positive plasma concentration anomaly at the altitude near 1000 km. Some plasma anomalies registered over the tropical depressions before hurricane formation give hope on predictive capabilities of plasma observations over the tropical depressions.

Pulinets, S. A.; Davidenko, D.

2013-12-01

387

Ionospheric response to the acoustic gravity wave singularity  

NASA Astrophysics Data System (ADS)

An original model of atmospheric wave propagation from ground sources to the ionosphere in the atmosphere with a realistic high-altitude temperature profile is analyzed. Shaping of a narrow domain with elevated pressure in the resonance region where the horizontal phase wave velocity is equal to the sound velocity is examined theoretically within the framework of linearized Eq.s. Numerical simulations for the model profiles of atmospheric temperature and viscosity confirm analytical result for the special feature of wave fields. The formation of the narrow domain with plasma irregularities in the D and low E ionospheric layers caused by the acoustic gravity wave singularity is discussed.

Savina, Olga N.; Bespalov, Peter A.

2014-11-01

388

The Dayside Ionospheric  

Microsoft Academic Search

Prompt penetration electric fields (PPEFs) and the consequential dayside ionospheric superfountain (DIS) are reviewed. An example of O+ uplift to ~840 km altitude at ~0940 local time (DMSP F15) during the superstorm of 30 October 2003 is illustrated. The SAMI-2 model is modified to incorporate intense superstorm electric fields. With an inclusion of a ~4 mV\\/m eastward electric field, SAMI-2*

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

2006-01-01

389

On the dynamics and instabilities of the low latitude ionosphere  

NASA Astrophysics Data System (ADS)

The Ionosphere is a region in the upper atmosphere that results from solar radiation acting upon the neutral gases existing there. The created ions and electrons form the ionospheric plasma that coexists and interacts with the neutral gases. This dissertation deals with the dynamics of the low latitude ionosphere, a region near the magnetic equator, where the Earth's magnetic field lines are almost horizontal and thus perpendicular to gravity and the gradients of electron density. Winds generated by the daily thermal expansion of the upper atmosphere affect the motion of the ionospheric plasma and vice versa. The unique magnetic field geometry existing in the low latitude ionosphere leads to a latitudinal re- distribution of the ionosphere, and this pattern affects the winds via a mechanism called ion-drag. The initial results from this dissertation come from the first multi-site, ground-based measurements of eastward winds in the same longitude sector at low latitudes. Airglow emissions serve as tracers of the motions of the atmosphere. Observations of these emissions, made from two observatories in South-America, reveal a latitude structure of the winds that is inconsistent with current models due to their inadequate representation of ion-drag. Imaging systems are used to broaden this approach to the first study of the latitude dependence of zonal plasma drifts by following the motions of airglow structures from two different locations. The results obtained show only partial agreement with state-of-the-art models, indicating that the electric fields are not adequately represented in the models. In addition to the horizontal motion of neutral and charged particles, there is vertical motion of ionospheric plasma that can lead to the occurrence of plasma instabilities. These instabilities have dramatic consequences, not only on the overall dynamics of the r