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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 91 records · Page 5
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NASA NTRS1985

Computer simulation of plasma electron collection by PIX-II

A wake model was defined for the NASCAP/LEO finite element model for the plasma interaction experiment (PIX-II) launched to study the interaction between high-voltage large solar arrays with the space plasma environment. The cell surface model considers the individual cells, distances between interconnects, and the fraction of surface covered by interconnects. Account is taken of the electrostatic potential around the spacecraft, which travels at 7500 mps, over five times the speed of thermal ions. Ram ions are produced ahead of the array and the wake ion density is described with a geometric shadowing model. The model correctly predicted the currents in high and low bias voltages when compared to orbital data. The panel snapover, however, was projected to occur at 100 V and instead occurred at 300 V, which indicates that the snapover state is bistable. Finally, a low potential was both predicted and measured in the wake.

Mandell, M. J.↗
NASA NTRS1988

Plasma electrons as tracers of distant magnetotail structure - ISEE-3

This paper compares the electron spectra and phase space densities measured concurrently by ISEE-3 at 200 R(E), with those measured by DMSP at low altitudes. The field-aligned lobe electron phase space densities above 200 eV at ISEE were found to agree well with the DMSP-measured polar rain phase space densities near the polar cap; the spectral slopes above 200 eV were also similar. Below 100-200 eV, a thermal electron population was measured by ISEE in the distant tail, which arose from local entry of plasma through the distant magnetopause, which is not present at DMSP altitudes. These data show that the suprathermal tail lobe electrons are essentially a test particle population which can move freely along field lines to form polar rain; in contrast, the thermal electrons are bound to the tailward-flowing lobe ion population far down the tail and, thus, cannot reach the polar cap regions.

Baker, D. N.↗
NASA NTRS1987

Plasma electron collection through biased slits in a dielectric

A large number of experimental and analytical efforts have been directed toward understanding the plasma sheath growth and discharge phenomena which lead to high-voltage solar array/space plasma interactions. An important question which has not been addressed is how the voltage gradient in the plasma sheath near the surface of such an array may affect these interactions. The purpose of the experimental study described in this paper is to examine the merging of the sheaths around biased slits in a dielectric and how this affects the collection of electrons through these slits. The data, which are obtained by emissive probes and direct measurement of the current collected through the slits, indicate that when the sheaths merge the current collection by the slits is significantly altered with the most positive slit collecting more electrons than it otherwise would. Therefore, the effect of a voltage gradient in the sheath around a solar array should be considered when evaluating solar array performance.

Carruth, M. R., Jr.↗
NASA NTRS1984

Relationship of dusk sector radial electric field to energy dispersion at the inner edge of the electron plasma sheet

It is shown that, by assuming that the magnetospheric particle boundaries are the result of steady state convection, the electron boundaries in the dusk sector are essentially sensitive to the local, not the global, electric field configuration. A simple, direct relationship is obtained between the dusk sector radial electric field and the inner edge of electron boundaries at various energies.

Horwitz, J. L.↗
NASA NTRS1995

A review of solar wind ion and electron plasma distribution functions: Present understanding and Ulysses results

Our present understanding of the distribution functions of the solar wind ion and electron thermal/suprathermal populations will be reviewed covering selected theoretical and observational topics. Roughly half the review will be devoted to recent discoveries (since Solar Wind 7). Among recent results are those of the Ulysses mission. The SWICS experiment observed pick-up protons and alpha particles, and acceleration of these particles at interplanetary shocks. Positive ion phenomena observed by SWOOPS include enhanced proton-alpha particle differential streaming both: (1) at high latitudes; and (2) in the ecliptic beyond 1 AU in the vicinity of shocks. The SWOOPS positive ion observations also demonstrate relative constancy of the entropy per proton at high latitudes beyond about 2.5 AU. Double beaming in both protons and alphas is observed by SWOOPS on either side of the current sheet, but not within; a possible explanation is reconnection at the edge of the current sheet. SWOOPS observed bi-directional streaming of electrons beyond 2 AU not only within Coronal Mass Ejections, but also upstream of corotating interplanetary shocks. Latitudinal and radial gradients of Ulysses electron core and halo temperatures will be discussed, as will work in progress on the three dimensional (in velocity space) properties of ion distributions.

Goldstein, B. E.↗
NASA NTRS1987

The Giotto electron plasma experiment

The RPA-Copernic experiment aboard Giotto is described. The experiment is designed to measure the three-dimensional distributions of electrons between 10 eV and 30 keV (by the RPA-1 EESA spectrometer) and the composition and distribution, close to the comet, of thermal positive ions in the mass range 10-213 amu (by the RPA-2 PICCA electrostatic mass analyzer). Three microprocessors interface RPA-1 EESA with RPA-2 PICCA and with the spacecraft and perform extensive onboard data processing. The experiment was operated successfully aboard the spacecraft in September 1985 during the encounter of Giotto with the comet Halley. The results provided by the EESA-1 indicate that the solar wind interaction with the comet Halley forms a well-defined bow shock with features quite different from the features of the comet Giacobini-Zinner bow shock; the data also showed a presence of accelerated keV electrons at the cometary bow shock, upstream and in the transition region.

Reme, H.↗
NASA NTRS1972

Electron plasma oscillations in the near-earth solar wind: Preliminary observations and interpretations

Preliminary results and conclusions of a study of electric field oscillations in the upstream solar wind are reported. The OGO-5 orbits are on the dusk (three) and on the dawn (one) sides of the earth-sun line. It is concluded that there are electron streams produced at or near the bow shock. These streams penetrate the incoming solar wind plasma, and generate quasi-electromagnetic waves. The streams (as inferred from the wave levels) occur without regard to dawn-dusk location, as opposed to the low-frequency MHD upstream disturbances driven by backstreaming protons, which show a definitely strong preference for the dawn-noon sector. The presence of the suprathermal electron streams and associated wave turbulence indicates that some near-earth electron distributions are probably not representative of true solar wind distributions far away from the earth.

Fredricks, R. W.↗
NASA NTRS1979

Plasma electron observations in the vicinity of magnetic holes

In the present study, 14 events of interplanetary magnetic field dips are identified. Eleven of these are found to be associated with significant enhancements in the flux of electrons of energies of approximately 100 eV. Five (of the eleven) are characterized by significant changes in the magnetic field direction, and six are not. Thus, even though an electron enhancement is usually seen at a dip, the enhancement need not be always associated with magnetic reconnection, for which a directional change is essential. It appears that some events involve local acceleration, possibly the results of reconnection, while others may involve electrons injected onto the field line at a remote point.

King, J. H.↗
NASA NTRS1982

Plasma electron signature of magnetic connection to the earth's bow shock - ISEE 3

New observations of bowshock modified electron velocity distribution for upstreams are investigated using the Los Alamos ISEE 3 electron analyzer. Examples of two-dimensional electron distributions observed when ISEE 3 magnetically connected to the bowshock are presented, and the velocity moments are determined. The origin of the enhanced backstreaming electron fluxes and their likely effects on the upstream microturbulence spectrum are interpreted. A nearly isotropic component of back-streaming shock-heated electrons is found with energies at least as high as 1 keV. Phase-space density of the low energy parts of distributions measures well within the boundaries of accessibility and is observed to be depressed. Such distributions are likely to result from the direct sampling of electrons originating within the forward edge of the earth's bowshock, and may be unstable to whistler waves.

Feldman, W. C.↗
NASA NTRS1984

The adiabatic energy change of plasma electrons and the frame dependence of the cross-shock potential at collisionless magnetosonic shock waves

The adiabatic energy gain of electrons in the stationary electric and magnetic field structure of collisionless shock waves was examined analytically in reference to conditions of the earth's bow shock. The study was performed to characterize the behavior of electrons interacting with the cross-shock potential. A normal incidence frame (NIF) was adopted in order to calculate the reversible energy change across a time stationary shock, and comparisons were made with predictions made by the de Hoffman-Teller (HT) model (1950). The electron energy gain, about 20-50 eV, is demonstrated to be consistent with a 200-500 eV potential jump in the bow shock quasi-perpendicular geometry. The electrons lose energy working against the solar wind motional electric field. The reversible energy process is close to that modeled by HT, which predicts that the motional electric field vanishes and the electron energy gain from the electric potential is equated to the ion energy loss to the potential.

Goodrich, C. C.↗
NASA NTRS1987

Dynamic substorm injections - Similar magnetospheric phenomena at earth and Mercury

Correlations between energetic electrons, plasma electrons, and magnetic fields during the Mercury 1 energetic particle events are examined and comparisons are made with several well-documented substorm injections at the earth. The data reveal that the B and B-prime events possess the same characteristics as single-point observations of terrestrial dynamic injections. Several recently discovered correlations between the energetic electrons, plasma electrons, and magnetic fields at Mercury are discussed.

Christon, S. P.↗