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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

In situ observations of Io torus plasma

The physical properties of the Io plasma formation deduced from in situ observations are described. The torus plasma is characterized by spatially distinct regions with steep gradients in plasma parameters between them. The innermost region has a cool plasma which collapses toward the centrifugal equator and gives rise to a distinctive localized concentration of plasma well inside of Io's orbit. The next region has a warm plasma which includes the L-shell of Io and is the presumed injection region of the plasma. Other regions, known as the plasma ledge and ramp, are described. The changes in plasma characteristics are accounted for by centrifugally driven flux tube interchange diffusion to provide radial mass transport. The ramp is shown to result from impoundment of the plasma by the inner edge of the energetic particle population. It is also shown how the power required to excite the ultraviolet emissions of the torus and the Jovian aurora determines the rate at which new plasma is fed into the torus.

Sullivan, J. D.↗
NASA NTRS1983

Ponderomotive force in a warm two-fluid plasma

A general expression for the ponderomotive force of electromagnetic field with slowly varying amplitude in a warm plasma is obtained in the collisionless two-fluid model. Compared to the existing expression obtained for a cold and stationary plasma, this result contains two additional terms for the general case. One of them is involved with the density gradient and the wavenumber derivative of the dielectric tensor of a plasma. Thus, for an inhomogeneous plasma, it accounts for the effects of spatial dispersion, hence of finite temperature of the plasma. The other term is proportional to the time derivative of the density and the frequency derivative of the dielectric tensor, and is nonzero unless the plasma is stationary or nondispersive. Inclusion of these new terms in the ponderomotive force will enable self-consistent analysis of the general behavior of nonlinear waves with finite wavelengths in a warm plasma.

Lee, N. C.↗
NASA NTRS1980

Plasma chemistry for inorganic materials

Practical application of plasma chemistry to the development of inorganic materials using both low temperature and warm plasmas are summarized. Topics cover: the surface nitrification and oxidation of metals; chemical vapor deposition; formation of minute oxide particles; the composition of oxides from chloride vapor; the composition of carbides and nitrides; freezing high temperature phases by plasma arc welding and plasma jet; use of plasma in the development of a substitute for petroleum; the production of silicon for use in solar cell batteries; and insulating the inner surface of nuclear fusion reactor walls.

Matsumoto, O.↗
NASA NTRS1992

A comparison of two plasma models

The time dependent behavior of a plasma which surrounds a highly biased conducting sphere is considered. This plasma is treated as either a cold two component fluid or as a warm plasma whose time development can be found by solving the Vlasov equation. Both models demonstrate oscillatory behavior, but the electric fields predicted by the models are quantitatively quite different in regions close to the surface of the sphere and very similar otherwise. A broadening of the electron distribution function with time is observed indicating local heating of the plasma near the surface of the sphere.

Cottam, Russell↗
NASA NTRS2008

ISIS Topside-Sounder Plasma-Wave Investigations as Guides to Desired Virtual Wave Observatory (VWO) Data Search Capabilities

Many plasma-wave phenomena, observed by space-borne radio sounders, cannot be properly explained in terms of wave propagation in a cold plasma consisting of mobile electrons and infinitely massive positive ions. These phenomena include signals known as plasma resonances. The principal resonances at the harmonics of the electron cyclotron frequency, the plasma frequency, and the upper-hybrid frequency are well explained by the warm-plasma propagation of sounder-generated electrostatic waves, Other resonances have been attributed to sounder-stimulated plasma instability and non-linear effects, eigenmodes of cylindrical electromagnetic plasma oscillations, and plasma memory processes. Data from the topside sounders of the International Satellites for Ionospheric Studies (ISIS) program played a major role in these interpretations. A data transformation and preservation effort at the Goddard Space Flight Center has produced digital ISIS topside ionograms and a metadata search program that has enabled some recent discoveries pertaining to the physics of these plasma resonances. For example, data records were obtained that enabled the long-standing question (several decades) of the origin of the plasma resonance at the fundamental electron cyclotron frequency to be explained [Muldrew, Radio Sci., 2006]. These data-search capabilities, and the science enabled by them, will be presented as a guide to desired data search capabilities to be included in the Virtual Wave Observatory (VWO).

Benson, Robert F.↗
NASA NTRS1985

Plasma and magnetospheric research

Progress is reported in the development of programs for statistical analysis of boundary and structure type files based on surveys of Dynamics Explorere data. Programs being used for handling data on plasma boundaries in the inner magnetosphere, the structure of the plasmasphere, and the heavy ion torus may be useful for determining statistics on the warm plasma cloak and the auroral ion fountain. Data analysis and modeling; spacecraft sheath effects; and laboratory plasma flow studies are discussed.

Comfort, R. H.↗
NASA NTRS1971

Conversion of electrostatic plasma waves into electromagnetic waves - Numerical calculation of the dispersion relation for all wavelengths.

The dispersion curves have been computed for a wide range of wavelengths from electromagnetic waves to electrostatic waves in a magnetoactive warm plasma with a Maxwellian velocity distribution function. The computation was carried out mainly for the perpendicular propagation mode. The upper hybrid resonance is the connection point of the electrostatic waves and the electromagnetic waves. The electrostatic waves not associated with the upper hybrid resonance are subjected to electron cyclotron damping when the wavelength becomes long. Oblique propagation is allowed for the electrostatic waves in a frequency range from the plasma frequency to the upper hybrid resonance frequency in the long-wavelength region where Landau damping can be neglected and where the electrostatic mode smoothly connects to the electromagnetic X-mode. In a slightly inhomogeneous plasma, the Bernstein-mode electrostatic wave can escape by being converted into the O-mode electromagnetic wave; two reflections take place during this escape process.

Oya, H.↗
NASA NTRS1972

Interaction of the solar wind with the moon.

During its orbit about the earth, the moon is located in the interplanetary medium or in the geomagnetosheath-geomagnetotail formed by the solar wind interaction with earth. In the tail, no evidence is found for a lunar magnetic field. In the interplanetary medium, no evidence exists for a bow shock or a trailing shock, although a well defined plasma wake region is observed in the anti-solar wind direction. The moon absorbs the solar wind plasma that strikes its surface and creates a void region or cavity in the flow. The observed lunar Mach cone gives evidence for the anisotropic propagation of waves in the magnetized collisionless warm plasma of the solar wind. The transmission of microstructural discontinuities in the interplanetary medium past the moon shows little distortion, indicating a low effective electrical conductivity of the lunar body. Fluctuations of the interplanetary magnetic field upstream from the plasma wake are stimulated by the disturbed conditions in that region. The moon behaves like a cold, nonmagnetic, fully absorbing dielectric sphere in the solar wind flow.

Ness, N. F.↗
NASA NTRS1977

Significant initial results from the environmental measurements experiment on ATS-6

The Applications Technology Satellite (ATS-6), launched into synchronous orbit on 30 May 1974, carried a set of six particle detectors and a triaxial fluxgate magnetometer. The particle detectors were able to determine the ion and electron distribution functions from 1 to greater than 10 to the 8th power eV. It was found that the magnetic field is weaker and more tilted than predicted by models which neglect internal plasma and that there is a seasonal dependence to the magnitude and tilt. ATS-6 magnetic field measurements showed the effects of field-aligned currents associated with substorms, and large fluxes of field-aligned particles were observed with the particle detectors. Encounters with the plasmasphere revealed the existence of warm plasma with temperatures up to 30 eV. A variety of correlated waves in both the particles and fields were observed: pulsation continuous oscillations, seen predominantly in the plasmasphere bulge; ultralow frequency (ULF) standing waves; ring current proton ULF waves; and low frequency waves that modulate the energetic electrons. In additon, large scale waves on the energetic-ion-trapping boundary were observed, and the intensity of energetic electrons was modulated in association with the passage of sector boundaries of the interplanetary magnetic field.

Fritz, T. A.↗
NASA NTRS1989

Effects of unequal particle number densities on Alfven waves

Analytic plasma theory and numerical solutions of the dispersion equation are used to show that the assumption that the linear properties of the waves are determined by a charge-neutral plasma in the absence of the nonthermal particles, while the nonthermal particles cause growth or additional damping superposed onto the background, is seriously flawed even for stable plasmas. Even when the nonthermal particles do not contribute significantly to the dispersion equation, unequal thermal electron and ion number densities (due to the presence of the nonthermal particles) may cause fundamental low wave number modifications to the Alfven modes, including the creation of a new resonance and severely modified dispersion. These results are found for both cold and warm plasmas. Previous work on Alfven waves should be reevaluated in view of these results.

Cairns, I. H.↗
NASA NTRS1974

Plasma waves in the dayside polar cusp. II - Magnetopause and polar magnetosheath

During the outbound pass of Nov. 1, 1968, Ogo 5 sporadically encountered the low-altitude polar cusp at low magnetic latitudes. The spacecraft remained in the cusp beyond six earth radii, and it then traversed the interface region between the magnetospheric cusp and the magnetosheath. Two large scale discontinuities were detected in this sheath-cusp transition region, and several possible interpretations are evaluated here. At 1427 UT, local changes in magnetic field orientation and the variation in ULF magnetic power spectral density were typical of shifts detected at the magnetopause, although the spacecraft did not traverse a true boundary of warm plasma at this point. The second discontinuity, detected at 1456 UT, resembled a collisionless shock, and it was characterized by observations of intense, impulsive VLF electric field bursts and rapid local variations in both total ion flux and differential electron flux. The simplest interpretation is that Ogo 5 had traversed a standing shock within the sheath.

Scarf, F. L.↗