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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Boundary of the Distribution of Solar Wind Proton Beta versus Temperature Anisotropy

Abstract The frequency distribution of solar wind protons, measured in the vicinity of Earth’s orbit, is customarily plotted in ( β ∥ , T ⊥ / T ∥ ) phase space. Here, T ⊥ / T ∥ is the ratio of perpendicular and parallel temperatures, and β ∥ = 8 π nT ∥ / B 2 is the ratio of parallel thermal energy to background magnetic field energy, the so-called “parallel beta,” with ⊥ and ∥ denoting directions with respect to the ambient magnetic field. Such a frequency distribution, plotted as a two-dimensional histogram, forms a peculiar rhombic shape defined with an outer boundary in the said phase space. Past studies reveal that the threshold conditions for temperature anisotropy–driven plasma instability partially account for the boundary on the high- β ∥ side. The low- β ∥ side remains largely unexplained despite some efforts. Work by Vafin et al. recently showed that certain contours of collisional relaxation frequency, ν pp , when parameterized by T ⊥ / T ∥ and β ∥ , could match the overall shape of the left-hand boundary, thus suggesting that the collisional relaxation process might be closely related to the formation of the left-hand boundary. The present paper extends the analysis by Vafin et al. and carries out the dynamical computation of the collisional relaxation process for an ensemble of initial proton states with varying degrees of anisotropic temperatures. The final states of the relaxed protons are shown to closely match the observed boundary to the left of the ( β ∥ , T ⊥ / T ∥ ) phase space. When coupled with a similar set of calculations for the ensemble in the collective instability regime, it is found that the combined collisional/collective effects provide the baseline explanation for the observation.

Astronomy & Astrophysics↗
NASA NTRS1967

Energy conversion research

Energy conversion research on alkali metal vapor, large nonequilibrium generator, and plasma instability

ENERGY CONVERSION↗
NASA NTRS1969

Consequences of a magnetospheric plasma.

Magnetospheric plasma instabilities, discussing pitch angle diffusion instabilities, auroral precipitation boundary location, radial diffusion and maximum dissipation limit

Kennel, C. F.↗
NASA NTRS1972

The OPGT/MJS plasma wave science team

Some properties of a model magnetosphere for Saturn were studied in order to determine the bounds that can be set on surface field strength and trapped particle population. The primary observational constraint was that nonthermal radiation similar to the Jovian radio emissions must be undetectable from Earth. It is argued that for a Saturn surface field of approximately one gauss, particles that are energized as they diffuse in from the magnetopause with conservation of magnetic moment will produce synchrotron radiation levels that are undetectable at a range of 9.5 AU. The plasma instabilities that heat the oncoming wind particles at the bow shock and others that can limit the stably-trapped flux levels are also discussed.

Scarf, F. L.↗
NASA NTRS1971

Symposium on Uranium Plasmas: Research and Applications, 2nd, Atlanta, Ga., November 15-17, 1971, Collection of Technical Papers.

Results of theoretical and applied research related to fissioning uranium plasmas. Topics examined include uranium plasma instabilities, diagnostic techniques, radiant heat transfer characteristics, nuclear pumping of lasers, and various fission engine concepts. Engineering aspects considered for open-cycle gas core engines include effects of buoyancy on fuel containment, flow and criticality problems, effects of injection conditions, and radiation hazards. The nuclear light bulb engine, the mini-cavity reactor, the dust-bed reactor, and the colloid core reactor are also examined in terms of design and control considerations. Individual items are abstracted in this issue.

Source record↗
NASA NTRS1973

Study of artificially generated and natural auroras

The feasibility of generating artificial auroras by injecting electrons into the upper atmosphere was investigated by using an electron accelerator aboard an Aerobee 350 rocket. Four of the artificial auroral rays were detected and recorded by two geophysical sites separated enough to enable the spatial coordinates of the rays to be determined by triangulation. It was found that (1) the beam remained well collimated; (2) most of the initial beam energy was deposited in the atmosphere; (3) plasma instabilities did not play a significant role; and (4) the orientations of the rays were determined with sufficient accuracy to improve the knowledge of the earth's magnetic field over the Virginia coast. The publications resulting from this research are listed.

Davis, T. N.↗
NASA NTRS1972

A new cosmological model - Formation of organic molecules, planets, and comets.

A new model is proposed based on studies of plasma instabilities in a magnetic field, which suggests that the inside region of a star is quantized into smaller regions, each of which is rotating in the magnetic field of a central rotating stellar core. Numerous applications of such a model are explored and some, such as the earth, evaluated in detail.

Johnson, F. M.↗
NASA NTRS1973

Some comments on the magnetosphere and plasma environment of Saturn.

Some properties of a model magnetosphere for Saturn are studied in order to determine the bounds that can be set on the surface field strength and the trapped particle population. The primary observational constraint is that nonthermal radiation similar to the Jovian radio emissions must be undetectable from earth. It is argued that for a Saturn surface field of approximately one gauss, those particles that are energized as they diffuse in from the magnetopause with conservation of magnetic moment will produce synchrotron radiation levels that are undetectable at a range of 9.5 AU. The plasma instabilities that heat the oncoming wind particles at the bow shock and others that can limit the stably-trapped flux levels are also discussed briefly.

Scarf, F. L.↗
NASA NTRS1973

Field-aligned currents, plasma waves, and anomalous resistivity in the disturbed polar cusp.

During the magnetic storm of November 1, 1968, the Ogo 5 spacecraft encountered the polar cusp region at low magnetic latitudes. We show that the region just outside the last closed field lines contained a warm magnetosheath plasma, magnetic field perturbations interpretable as field-aligned current layers, and electrostatic waves possibly due to plasma instabilities driven by these currents. Estimates of anomalous resistivity extrapolated along the field lines due to these electrostatic waves lead to estimates of field-aligned potential drops between Ogo 5 and the ionosphere on the order of 2 kV.

Fredricks, R. W.↗
NASA NTRS1974

Simulation of colliding solar wind streams with multifluid codes

The description of a multifluid code with anomalous transport coefficients due to plasma instabilities self consistently followed in space and time is given. As an example, simulations of colliding solar wind streamers are presented. The results compare favorably with the observations.

Papadopoulos, K.↗
NASA NTRS1974

Acceleration of solar cosmic rays during chromospheric flares

Using the Fokker-Planck equation, an examination is made of the acceleration of charged particles by fluctuational electric fields caused by the propagation of intense radio emission in the long-wave range. Correlation functions of electric fields near the boundary of plasma instability were computed. The interaction of charged particles with these fields is examined. It is shown that due to the interaction of particles with fluctuational fields, solar cosmic rays can be accelerated to energies of E=100 to 1000 MeV.

Dorman, L. I.↗
NASA NTRS1974

Solar particles /observations, relationship to the sun acceleration, interplanetary medium/

The major features of the propagation of flare particles in the interplanetary medium are discussed in terms of the classic well-behaved flare having unique impulsive injection and a smooth time profile. Topics include flare events, their frequency of occurrence, development of a typical event, energy spectra, proton and electron types, charge and isotopic composition, solar flares and particle accelerations, radio and X-ray observations, the Fermi mechanism, the betatron mechanism, acceleration models, plasma instabilities, two-stage acceleration, propagation mechanisms, the anisotropic stage, the diffusive stage, and the convection and energy loss stage.

Mcdonald, F. B.↗
NASA NTRS1975

Development of solar wind shock models with tensor plasma pressure for data analysis

The development of solar wind shock models with tensor plasma pressure and the comparison of some of the shock models with the satellite data from Pioneer 6 through Pioneer 9 are reported. Theoretically, difficulties were found in non-turbulent fluid shock models for tensor pressure plasmas. For microscopic shock theories nonlinear growth caused by plasma instabilities was frequently not clearly demonstrated to lead to the formation of a shock. As a result no clear choice for a shock model for the bow shock or interplanetary tensor pressure shocks emerged.

Abraham-Shrauner, B.↗