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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 379 records · Page 21
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NASA NTRS1977

A statistical formulation of one-dimensional electron fluid turbulence

A one-dimensional electron fluid model is investigated using the mathematical methods of modern fluid turbulence theory. Non-dissipative equilibrium canonical distributions are determined in a phase space whose co-ordinates are the real and imaginary parts of the Fourier coefficients for the field variables. Spectral densities are calculated, yielding a wavenumber electric field energy spectrum proportional to k to the negative second power for large wavenumbers. The equations of motion are numerically integrated and the resulting spectra are found to compare well with the theoretical predictions.

Fyfe, D.↗
NASA NTRS1976

Radial diffusion in Jupiter's magnetosphere

Radial phase-space density profiles for equatorially mirroring particles are computed from data obtained by Pioneer 10. The profiles are consistent only with radial diffusion subject to nonadiabatic losses. It is suggested that these losses are due to pitch-angle scattering by whistler turbulence.

Baker, D. N.↗
NASA NTRS1977

The signature of parallel electric fields in a collisionless plasma

The presence of a parallel electric field in the magnetosphere should be apparent through its effect on particles. An analysis is made of particle trajectories in phase space for a steady state collisionless plasma. The analysis utilizes the concepts of distribution function, total energy, and magnetic moment because all three quantities are conserved in a steady state situation in the absence of collisions. Two methods are presented for using particle data to gain information on the potential distribution. The first method involves the use of measurements of both ion and electron distribution functions and invokes the principle of quasi-neutrality. The second method involves the observation of discontinuities in velocity space which can be interpreted in terms of the effect of the electric field on the apparent loss or source cone.

Whipple, E. C., Jr.↗
NASA NTRS1976

The development of the Poincare-similar elements with true anomaly as the independent variable

In reference 1, the Hamiltonian of the unperturbed two-body problem in extended phase space is established. Depending on the type of time transformation, eight canonical elements were developed with the true anomaly or the eccentric anomaly as the independent variable. These two new sets, DS(phi) and DS(u), however contain singularities for small eccentricities and inclinations. In reference 2, these singularities are removed by a transformation from DS(u) to eight canonical PS(u) elements. In reference 3, the DS(phi) variables are transformed to the PS(phi) elements to remove the singularities. However, no direct relation was established between the eight canonical PS(phi) elements and the Cartesian coordinates. It is the purpose of this report to establish those relations and to develop the perturbed equations of motion in the PS(phi) space. This report also demonstrates the accuracy of this new set when it is applied to numerical orbit prediction problems.

Mueller, A.↗
NASA NTRS1978

Experimental observations of strong double layers

A computer simulation is applied to the production of strong electric potential double layers (DL) in a triple plasma device. The simulation is intended to represent DL in the low magnetosphere above the auroral zones. The DL are described as standing electrostatic shocks with different energy coefficients in their strong and weak forms. The strong DL was generally found to be unstable, but stability could be imparted if a population of trapped electrons was presented. Stability increased with the length of the system. A schematic for the system is presented, and a phase-space plot of electrons (indicating system stability) is graphed.

Coakley, P.↗
NASA NTRS1978

Statistical formulation of one-dimensional electron fluid turbulence

A one-dimensional electron fluid model is investigated using the mathematical methods of modern fluid turbulence theory. Nondissipative equilibrium canonical distributions are determined in a phase space whose coordinates are the real and imaginary parts of the Fourier coefficients for the field variables. Spectral densities are calculated, yielding a wavenumber electric field energy spectrum proportional to 1/k squared for large wavenumbers. The equations of motion are numerically integrated and the resulting spectra are found to compare well with the theoretical predictions.

Fyfe, D.↗
NASA NTRS1977

Recursive analytical solution describing artificial satellite motion perturbed by an arbitrary number of zonal terms

An analytical first order solution has been developed which describes the motion of an artificial satellite perturbed by an arbitrary number of zonal harmonics of the geopotential. A set of recursive relations for the solution, which was deduced from recursive relations of the geopotential, was derived. The method of solution is based on Von-Zeipel's technique applied to a canonical set of two-body elements in the extended phase space which incorporates the true anomaly as a canonical element. The elements are of Poincare type, that is, they are regular for vanishing eccentricities and inclinations. Numerical results show that this solution is accurate to within a few meters after 500 revolutions.

Mueller, A. C.↗
NASA NTRS1977

Quantum statistical theory of semiconductor junctions in thermal equilibrium

Free carrier and electric field distributions of one-dimensional semiconductor junctions are evaluated using a quantum mechanical phase-space distribution and its corresponding Boltzmann equation. Attention is given to quantum and exchange corrections in cases of high doping concentrations when carrier densities become degenerate. Quantitative differences between degenerate and classical junction characteristics, e.g., maximum electric field and built-in voltage and carrier concentration within the transition region, are evaluated numerically.

Von Roos, O.↗
NASA NTRS1978

On the formation and evolution of clumps of galaxies in an expanding universe

Results are derived for the development of phase-space clumps of mass points in a background spectrum of gravitational-potential fluctuations. The Vlasov equation and the pair correlation equation (in the weak coupling limit) are solved exactly in an Einstein-de Sitter cosmology, and the plasma-clumping theory is used to identify terms that yield important collective effects. Various astrophysical implications are discussed, including the formation of large-scale inhomogeneity and the enhanced generation of correlations in the distribution of galaxies.

Norman, C. A.↗
NASA NTRS1979

Radial diffusion of Io-injected plasma

The paper reexamines the problem of particle injection by Io and subsequent radial diffusion by flux tube interchange using a proper phase space density formulation. The mathematical formalism is developed, and the theoretical results are compared with the observations, taking into account the pitch angle and energy coverage of the detector on Pioneer 10. Two objectives are pursued: (1) to test the hypothesis of Siscoe and Chen (1977) that Io is the source for all of the plasma observed by Frank et al. (1976) inside 10 R(J); and (2) to describe a simple but flexible method intended to analyze the observations of any other plasma instrument flown through the inner Jovian magnetosphere, e.g., those on Voyager 1 and 2 and Galileo.

Goertz, C. K.↗
NASA NTRS1979

A laser accelerator

It is shown that a laser can efficiently accelerate charged particles if a magnetic field is introduced to improve the coupling between the particle and the wave. Solving the relativistic equations of motion for an electron in a uniform magnetic field and superposed, circularly polarized electromagnetic wave, it is found that in energy-position phase space an electron traces out a curtate cycloid: it alternately gains and loses energy. If, however, the parameters are chosen so that the electron's oscillations in the two fields are resonant, it will continually accelerate or decelerate depending on its initial position within a wavelength of light. A laboratory accelerator operating under these resonant conditions appears attractive: in a magnetic field of 10,000 gauss, and the fields of a 5 x 10 to the 12th W, 10 micron wavelength laser, an optimally positioned electron would accelerate to 700 MeV in only 10 m.

Colson, W. B.↗
NASA NTRS1980

A general time element using Cartesian coordinates: Eccentric orbit integration

A general time element, valid with any arbitrary independent variables, and used with Cartesian coordinates for the integration of the elliptic motion in orbits, is examined. The derivation of the time element from a set of canonical elements of the Delaunay type, developed in the extended phase space, is presented. The application of the method using an example of a transfer orbit for a geosynchronous mission is presented. The eccentric and elliptic anomaly are utilized as the independent variable. The reduction of the in track error resulting from using Cartesian coordinates with the time element is reported.

Janin, G.↗
NASA NTRS1980

Permanent magnetic trapping

It is shown that the global nature of trapped particle motion in phase space makes it entirely plausible that particles with pitch angles near 90 deg are trapped for extremely long times, probably indefinitely. The long observed lifetimes of trapped particles can immediately be accounted for by this former population. For particles with low pitch angles an 'overstability' develops which serves to produce rapid variations in pitch angle and, presumably, random walk into the loss cone.

Michel, F. C.↗
NASA NTRS1980

Rocket-borne wave measurements in the dayside auroral oval

VLF and ELF waves were measured on two rocket payloads launched into the dayside auroral oval on Dec. 18, 1974, and on Jan. 11, 1975. The correlation of the VLF hiss intensity with the fluxes of precipitating electrons above 500 eV on short spatial and time scales was often poor, even when a positive slope existed in the electron phase space density. During the flight in 1975, distinct features were observed at the lower hybrid frequency; the frequency of this emission was used together with an independent density measurement to determine the relative concentration of O(+) to the heavier ions NO(+) and O2(+). It was found that the density of NO(+) or O2(+), which could not be distinguished, is enhanced over expected values between 150 and 400 km altitude. Broadband electrostatic and electromagnetic waves were observed after the barium-shaped charged explosion in 1975; the observed lowering of the auroral VLF hiss cutoff due to the barium is consistent with either ducting of VLF hiss emissions along the enhanced density duct produced by the barium or with local generation VLF hiss during the barium injection.

Temerin, M.↗
NASA NTRS1980

The polarization and directivity of solar-flare hard X-ray bremsstrahlung from a thermal source

The polarization and directivity of hard X-ray bremsstrahlung from a thermal source consisting of a region in which a thermal flux drives a pair of steel collisionless conduction fronts were evaluated. The conduction fronts are symmetrically driven from a central region, heated by the flare energy dissipation process. By comparing results with similar calculations based on a nonthermal thick-target electron beam model of the source, it was aimed to determine the degree to which the observed polarization and directivity of solar flare hard X-rays favor either model. Results which exhibit significant polarization and directivity of the hard X-ray radiation emitted by the source are produced by using Maxwellian electron-phase-space distribution functions modified to take into account a directional heat flux and a steady direct current in the X-ray source, and a fully relativistic treatment of the bremsstrahlung emission process. The results are consistent with solar hard X-ray anisotropy and polarization observations to date, although these observations are too crude to be conclusive.

Emslie, A. G.↗
NASA NTRS1981

Energetic oxygen and sulfur ions in the Jovian magnetosphere

Observations of 1 to 20 MeV/nuc oxygen, sodium, and sulfur ions in the Jovian magnetosphere are reported. Measurements made by the cosmic ray subsystem on Voyager 1 and 2 were used to calculate abundances and energy spectra in the region from 5 to 20 Jovian radii. The phase space density of the oxygen ions calculated from the spectra has a positive radial gradient between 6 and 17 Jovian radii, indicating an inward diffusive flow. The diffusion coefficient upper limit at 9 Jovian radii is approximately 10 to the -5 power/s. This limit, combined with the analysis of Voyager plasma observations by Siscoe et al.1981, implies an upper limit to the mass loading rate near Io of approximately 10 to the 28th power ions/s. The energetic oxygen lifetime is within an order of magnitude of the strong pitch-angle diffusion lifetime in this region, with the largest total number of particles lost between 7.5 and 12.5 Jovian radii. It is shown that the losses are not due to geometric absorption by Io, absorption by dust grains, or energy loss in the plasma of the inner magnetosphere, and it is therefore postulated that the primary loss mechanism is pitch-angle scattering into the loss cone.

Gehrels, N.↗
NASA NTRS1980

Sources and sinks of energetic electrons and protons in Saturn's magnetosphere

The paper deals with some results of continuing analysis and interpretation of energetic particle observations made onboard Pioneer 11 during its August-September 1979 encounter with Saturn. Source strength estimates and the radial dependence of the phase space density of protons of energies above 80 MeV indicate with some confidence that the cosmic-ray neutron albedo from the planets atmosphere and rings is the source of these particles.

Van Allen, J. A.↗
NASA NTRS1980

Charged particle diffusion and acceleration in Saturn's radiation belts

In the present paper, an attempt is made to determine, from the observed intensity profiles for protons and electrons in the region of L smaller than 4, whether population of Saturn's innermost trapped radiation zones from an external source is possible. It is found that if diffusion proceeds in an episodic rather than a steady-state manner (long periods of quiescence interrupted by brief periods of rapid diffusion), the basic features of the observed phase space density profiles are qualitatively reproduced for both the trapped protons and electrons.

Mckibben, R. B.↗