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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Some possible effects of Jupiter's rings on the Jovian inner plasmasphere

The ionospheric plasma density on magnetic field lines threading the Jovian rings which are located inside approximately 1.8 Jupiter radii on the jovigraphic equatorial plane is calculated by using a rotating ion exosphere model. It is found that the bulk of the ionospheric particles on these field lines are on ballistic trajectories. On field lines approximately symmetric with respect to the jovigraphic equator, the ring, which to a first approximation would absorb the population of trapped particles, consequently has little effect. On field lines which are made asymmetric by the higher-order multipoles of Jupiter's field and the tilt of the dipole axis, the rings may have a significant effect. It is suggested that better definition of the rings' atmospheric and ionospheric properties is required to model these localized effects. If the rings are found to be an important plasma source for the inner magnetosphere, the present exospheric model will have to be revised.

Luhmann, J. G.↗
NASA NTRS1982

Coordinated measurements of slot region electron precipitation by plasmaspheric wave bands

Simultaneous measurements have been made of slot region precipitating electron spectra, wave frequency distributions and plasma density profiles using the P78-1 low altitude satellite and ISEE 1 spacecraft. Broad bands are often observed in the electron energy spectra with a well-defined low energy cutoff which decreases in energy with increasing L value. This is consistent with calculations for first-order cyclotron resonance with waves at the high frequency cutoff of the band. On the basis of electron spectra and plasma densities observed from upper hybrid resonance frequencies, hiss cutoff frequencies are calculated for an assumed first-order cyclotron resonance interaction and compared with wave spectral density profiles. Plasma wave and electron measurements are generally consistent, supporting the precipitation mechanism hypothesis.

Imhof, W. L.↗
NASA NTRS1983

Characteristics of low-energy plasma in the plasmasphere and plasma trough

Initial results of studies of low-energy plasma using the light ion mass spectrometer (LIMS) on the SCATHA satellite are presented. Results are discussed primarily for plasma flux in the noon to midnight local time sector, examining the behavior of the plasma with geomagnetic activity and local time. Measurements of the ion mass composition in this region for the energy ranges of the LIMS instrument are presented. Results of temperature measurements are given and a possible explanation for the difference between the whistler and OGO 5 plasmapause positions is suggested. The observed pitch angle distributions are presented, limited to a broad characterization of the plasma population. The effects of the spacecraft potential on the low-energy plasma measurements are considered.

Reasoner, D. L.↗
NASA NTRS1987

Plasmasphere and magnetosphere structure from ISEE-1 and DE-1

The density structure of the plasmapause was investigated using the two satellites ISEE-1 and DE-2 to obtain complementary radial and latitudinal profiles. Data from the plasma wave receivers were to be used to obtain the total electron density, and from the ion mass spectrometers to determine thermal plasma morphology. Electron density profiles were obtained for 25 sets of orbits when the satellites were adjacent.

Olsen, R. C.↗
NASA NTRS1987

Plasmasphere and magnetosphere structure from ISEE-1 and DE-1

The density structure of the plasmapause region was investigated using the two satellites, ISEE-1 and DE-1 to obtain complementary radial and latitudinal profiles. Data from the plasma wave receivers were to be used to obtain total electron density, and from the ion mass spectrometers to determine thermal plasma morphology.

Olsen, R. C.↗
NASA NTRS1986

Models of the plasmaspheric thermal plasma distribution

Current understanding of the thermal plasma in the atmosphere and its coupling to the ionosphere is reviewed. Existing models appear adequate to explain the gross behavior of the cold thermal plasma, but there remain some vexing problems. Notably, (1) why does the density in flux tubes appear to saturate at lower values than are predicted theoretically, (2) what causes the sunset peak in measured Te, and (3) why does the equatorial plasmapause signature differ in latitude from the ionosphere signatures. The more difficult problem of what happens during the early stages of refilling after a magnetic storm, when the high altitude plasma is likely to be supersonic and collisionless, has received much attention, but the results are not definite. A number of papers have dealt with the interaction of supersonic counterstreaming fluxes and there are now models that can handle the transition from supersonic to subsonic flows although the transition from a collisionless to a collision-dominated plasma remains difficult to deal with.

Richards, P. G.↗
NASA NTRS1988

Refilling of a plasmaspheric flux tube - Microscopic plasma processes

The paper elucidates those microscopic plasma processes (electrostatic shocks, pitch angle scattering of the ions, and ion perpendicular heating) which help in trapping and/or thermalizing the plasma in the flux tubes. The mechanism and conditions for electrostatic shock formation are discussed. It is shown that equatorial ion heating stops interhemispheric flow by setting up a potential barrier at the equator.

Singh, N.↗
NASA NTRS1988

Review of microscopic plasma processes of occurring during refilling of the plasmasphere

Refilling of the plasmashere after geomagnetic storms involves both macroscopic and microscopic plasma processes. The latter types of processes facilitate the refilling by trapping the plasma in the flux tube and by thermalizing the interhemispheric flow. A review of studies on microscopic processes is presented. The primary focus in this review is on the processes when the density is low and the plasma is collisionless. The discussion includes electrostatic shock formation, pitch angle scatterring extended ion heating and localized ion heating in the equatorial region.

Singh, N.↗
NASA NTRS1990

Properties of large scale plasma flow during the early stage of the plasmaspheric refilling

The objective is to better characterize the macroscopic properties of the interhemisphere plasma flow by solving a more complete set of hydrodynamic equations than that solved previously. Specifically, the ion continuity, momentum and energy equations were solved for the plasma flow along the closed magnetic field lines. During the initial stage of the supersonic outflow in the equatorial region, the ions cool substantially. Using the hydrodynamic model for the large-scale plasma flow, the dynamics of shocks was examined which form in the geomagnetic flux tubes during the early stages of refilling. These shocks are more like those forming in neutral gases than the electrostatic shocks driven by microinstabilities involving ion-ion interaction. Therefore, the shocks seen in the hydrodynamic model are termed as hydrodynamic shocks. Such shocks are generally unsteady and therefore the usual shock jump conditions given by Rankine-Hugoniot relations are not strictly applicable to them. The density, flow velocity and temperature structures associated with the shocks are examined for both asymmetrical and symmetrical flows. In the asymmetrical flow the outflow from one of two conjugate ionospheres is dominant. On the other hand, in the symmetrical case outflows from the two ionospheric sources are identical. Both cases are treated by a two-stream model. In the late type of flow, the early-time refilling shows a relaxation type of oscillation, which is driven by the large-scale interactions between the two identical streams. After this early stage, the resulting temperature structure shows some interesting features. In the equatorial region the streams are isothermal, but in the off-equatorial regions the streams have quite different temperatures, and also densities and flow velocities. The dense and slow stream is found to be warmer than the low-density fast stream. In the late stage of refilling, the temperature is found to steadily increase from the conjugate ionospheres towards the equator; the equatorial temperature is found to be as high as about 8000 K compared to the ionospheric temperature of 3600 K.

Singh, Nagendra↗
NASA NTRS1991

Role of ion temperature anisotropy in multistage refilling of the outer plasmasphere

The refilling processes predicted by the ion temperature anisotropy (TAN) model and those of a model based on the assumption of temperature isotropy (TISO) are compared. It is noted that the TISO model predicts that a flux tube with L = 4 undergoes a substantial refilling in about 12 hours after a severe depletion, while the TAN model predicts much longer refilling time divided in two stages, with the supersonic flows from the conjugate ionospheres in the early stage, lasting over a few hours. The plasma in the flux tube develops an anisotropy causing a downward force, which balances the upward electric and pressure forces on ions keeping the flux tube depleted. The second stage starts when the temperature anisotropy begins to relax due to Coulomb collisions at high altitudes and is characterized by a subsonic flow.

Singh, Nagendra↗
NASA NTRS1992

Effects of equatorially trapped ions on refilling of the plasmasphere

The kinetic aspects of shock formation in response to the equatorial heating of ions are reported by means of small-scale kinetic simulations of countersteaming plasma flows along a spatially varying magnetic field having the features of the dipolar magnetic field lines. Attention is given to the trapping of the field-aligned flowing ions in response to the simulated equatorial heating of ions and the associated self-consistent structures in the electric potentials and the f-plasma flow pattern. Trapping is found to lead to the formation of electrostatic shocks, which propagate away from the 'equator' as seen in the hydrodynamic model of Singh and Torr (1990). The shocks form near the mirror points of the 'equatorially' heated ions. The second stage of the refilling with equatorially trapped ions is reported. A variety of structures in density and temperature distributions as the refilling proceeds slowly is found.

Singh, Nagendra↗
NASA NTRS1992

Magnetospherically reflected whistlers as a source of plasmaspheric hiss

Ray-tracing simulations and estimates of whistler wave damping show that magnetospherically reflected whistlers can persist for about 100 s in a LF band (about 1 kHz). The combined contribution from whistler rays produced by a single lightning flash but entering the magnetosphere at different points form a continuous hisslike signal, as observed at a fixed point. Estimates indicate that the total whistler wave energy input into the magnetosphere from lightning discharges may maintain experimentally observed levels of magnetospheric hiss.

Draganov, A. B.↗
NASA NTRS1992

Kinetic plasma processes occurring in the outer plasmasphere

One area of data analysis work that was begun under this contract is the fitting of the perpendicular velocity distributions of equatorially trapped ions with a Kappa function. This type of characterization of the trapped ions will be very useful for comparison with velocity distributions produced by the model. A second area of data analysis is to study data from consecutive passes when DE 1's apogee was near the magnetic equator and the spacecraft was often skimming along nearly the same L shell. In 1982 three such periods occurred in May, June, and July. For these consecutive events we have Kp histories, density measurements from a number of sources (Whistler data, DE SFR, ISEE SFR) and consecutive samples of ion pitch angle distributions along field lines. It is clear from this data how the pitch angle distributions evolve during a flux tube refilling event. Our modeling of the flow of plasma along closed field lines is following two basic tracks. The first is a study of the basic refilling process without the effect of wave-particle heating near the equator or the effect of large or abrupt field-aligned electric potential drops. This model includes the effects of Coulomb self-collisions and collisions with the O+ ions in the topside ionosphere. The second track is a study of the effects of wave produced pitch-angle scattering and perpendicular heating occurring near the magnetic equator, in connection with the development of large potential drops that result from electron heating and the development of density gradients.

Wilson, Gordon R.↗
NASA NTRS1994

Studies on equatorial shock formation during plasmaspheric refilling

Investigations based on small-scale simulations of microprocesses occurring when a magnetic flux tube refills with a cold plasma are summarized. Results of these investigations are reported in the following attached papers: (1) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: The Role of Ion Beam-Driven Instabilities'; and (2) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: Effects of Magnetically Trapped Hot Plasma'. Other papers included are: 'Interaction of Field-Aligned Cold Plasma Flows with an Equatorially-Trapped Hot Plasma: Electrostatic Shock Formation'; and 'Comparison of Hydrodynamic and Semikinetic Treatments for a Plasma Flow along Closed Field Lines'. A proposal for further research is included.

Singh, N.↗
NASA NTRS2000

Specifications of a Plasmasphere Modeling Code for GGCM

The Dynamic Global Core Plasma Model (DGCPM) is a parameterized model for core or thermal plasma in the magnetosphere. The model accounts for dayside ionospheric outflow and nightside inflow. It accounts for the global pattern of convection and corotation. The model is capable of being coupled to ring current and superthermal electron models for the purpose of providing thermal plasma spatial distributions and for the purpose of accepting the dynamic influences of these plasma populations back upon the thermal plasma. The DGCPM is designed to operate alone or to operate as part of a larger integrated package. The convection electric field and magnetic field used within the DGCPM can be shared with models of other plasma populations, in addition to the exchange of parameters important to the collective modeling of whole plasma systems in the inner magnetosphere. This talk will present the features of the DGCPM model code and the various forms of information that can be exchanged with other cooperating codes.

Gallagher, D. L.↗