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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
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NASA NTRS1974

Galactic arm structure and gamma-ray astronomy

In an attempt to explain the observed unexpectedly high-energy gamma-radiation over a broad region of the galactic plane in the general direction of the galactic center, a model is proposed wherein the galactic cosmic rays are preferentially located in the high-matter-density regions of galactic arm segments, as a result of the weight of the matter in these arms tying the magnetic fields and hence the cosmic rays to these regions. The presently observed longitudinal distribution of galactic gamma-rays can be explained with the current estimate of the average galactic matter density, if the average ratio of arm to interarm matter is 5:1 for the major arm segments toward the galactic center from the sun, and if the cosmic-ray density normalized to its local value is assumed to be directly proportional to the matter density.

Bignami, G. F.↗
NASA NTRS1974

Observation and explanation of a 0.3% sunward radial streaming of 1 to 5 GV cosmic radiation

A high-energy proton telescope on board the HEOS-1 satellite obtained quiet-time anisotropy data between December 1968 and April 1970. Analysis of the data showed an integral radial streaming component towards the sun of 0.3% for particles of rigidity greater than 1 GV. This value is not explicable in terms of any experimental defect, the effect of the earth's magnetosphere or energy loss effects under spherical symmetry in the solar cavity. An explanation in terms of a falling off ecliptic gradient in cosmic ray density most affecting the 1-5 GV range would seem to be the most compelling.

Dyer, C. S.↗
NASA NTRS1976

Energetic electrons in the Jovian magnetosphere

Results are reported for a detailed analysis of Pioneer 10 data on energetic particle species in the magnetodisk region of Jupiter's magnetosphere. It is shown that the observed counting rates in the magnetodisk (beyond 20 Jupiter radii) were caused primarily by electrons with energies exceeding 0.06 MeV. Absolute omnidirectional electron intensities in the magnetodisk are presented for five integral energy ranges, and a model electron differential energy spectrum is found to fit the intensities throughout most of the encounter trajectory. It is suggested that the observed spectral shape results from losses of high-energy electrons by pitch-angle scattering. Observed equatorial energy spectra are used to compute distribution functions for several values of the first adiabatic invariant, mu. The radial profiles of the functions are found to have maxima at about 50 Jupiter radii inbound as well as at about 90 radii outbound and to diminish strongly for lesser radii. The large decreases in density are shown to require strong losses, and resonant electron whistler-mode pitch-angle scattering is suggested as a loss mechanism.

Baker, D. N.↗
NASA NTRS1976

Iron line emission from a high-temperature plasma in Cassiopeia A

The letter reports a measurement of the X-ray spectrum of Cas A with a proportional counter on board OSO-8. The high-energy data (greater than 7 keV) are found to agree equally well with a power law having a number index of about 4.5 and with a thermal spectrum having kT of about 3.9 keV. A narrow iron line predicted by the thermal model is also observed; this line is centered at about 6.67 keV and has an equivalent width of approximately 1270 eV. The low-energy data (below 6 keV) are not fully accounted for by the above thermal spectrum, but are fitted well by an additional low-temperature thermal component with kT not exceeding 0.7 keV and an atomic hydrogen column density of approximately 10 to the 22nd power per sq cm. The iron abundance in the plasma at an electron temperature of 40 keV is estimated from the observed line-to-continuum ratio, and it is shown that a normal cosmic iron abundance is adequate to explain the observation.

Pravdo, S. H.↗
NASA NTRS1977

A comparison between N2/+/ 4278-A emission and electron flux in the auroral zone

Visual airglow and low-energy electron experiment data from the Atmosphere Explorer D satellite are used to measure variations in N2(+) density and mixing in the nighttime auroral zone. The intensity of the 4278-A N2(+) emission, proportional to energy flux deposited in N2 by energetic electrons, is determined by a method which corrects for ground reflection affecting the satellite data. Calculations related to electron energy flux are found to show a slight variance from the theoretical predictions of Rees and Luckey (1974). Evidence for high-energy proton precipitation on the southern edge of the aurora and for the presence of parallel electric fields in the altitude range 150 to 800 km is also discussed.

Kasting, J. F.↗
NASA NTRS1975

On the apparent diamagnetism of the lunar environment in the geomagnetic tail lobes

The reported investigation presents the magnetic observations averaged in a format that facilitates comparison with models of plasma diamagnetic effects. These models demonstrate that a decreased plasma energy density in the lunar vicinity always causes an induced dipole that increases the external field. Hence, an increased plasma energy density in the lunar environs is required to account for the observed magnetic decrease. There are several different plasma populations in the high-latitude geomagnetic tail lobes, including the lunar ions resulting from photoionization of lunar atmosphere neutrals, possible fluxes of polar-wind protons, low-energy particle events which consist of antisolar directed fluxes of 100-eV protons, photoelectrons from the dayside lunar surface, and a high-energy thermal population.

Goldstein, B. E.↗
NASA NTRS1978

High beta plasma in the dynamic Jovian current sheet

The equatorial current sheet, which Pioneer 10 repeatedly encountered on its outbound pass through the Jovian magnetosphere, frequently was associated with intense fluxes of energetic protons. Simultaneous observations of the changes in the energetic proton flux and in the magnetic-field magnitude demonstrate that the current sheet is embedded in a high-beta plasma in which high-energy (above 60 keV) ions frequently are the dominant constituents. Large differences in the plasma temperature and the thickness of this plasma sheet between encounters only 10 hours apart indicate that the Jovian plasma sheet is very dynamic on a time scale of hours. Occasional observations of significant temporal variations in the magnetic field and particle populations during periods within the plasma sheet may represent in situ observations of Jovian magnetic disturbances. Comparison with previous observations suggests that low-energy (not more than 5 keV) plasma contributes less than 3% to the current-sheet energy density.

Walker, R. J.↗
NASA NTRS1978

Comparison of high energy gamma rays from absolute value of b greater than 30 deg with the galactic neutral hydrogen distribution

High-energy gamma-ray (energy above 35 MeV) data from the SAS 2 satellite have been used to compare the intensity distribution of gamma rays with that of neutral hydrogen (H I) density along the line of sight, at high galactic latitudes (absolute values greater than 30 deg). A model has been constructed for the case where the observed gamma-ray intensity has been assumed to be the sum of a galactic component proportional to the H I distribution plus an isotropic extragalactic emission. A chi-squared test of the model parameters indicates that about 30% of the total high-latitude emission may originate within the Galaxy.

Ozel, M. E.↗
NASA NTRS1979

Some initial ISEE-1 results on the ring current composition and dynamics during the magnetics storm of December 11, 1977

On December 11, 1977 the ISEE-1 spacecraft traversed the equatorial magnetosphere in the prenoon and dawn sectors during the early recovery phase of a magnetic storm with peak DST of -125 gamma. Along the dayside leg O(+) was comparable to or exceeded H(+) in number density in the energy range 0.1-17 keV. The velocity distribution of O(+) showed a characteristic dispersion, consistent with the ions being transported to the dayside from the dusk to midnight sector. The high-energy slope of the H(+) and O(+) distribution functions showed different radial dependence, with the slope of H(+) being consistent with a harder component carrying most of the energy density.

Lennartsson, W.↗
NASA NTRS1980

Evaluation of high-energy lithium thionyl chloride primary cells

An advanced commercial primary lithium cell (LiSoCl2) was evaluated in order to establish baseline data for improved lithium batteries for aerospace applications. The cell tested had nominal capacity of 6 Ah. Maximum energy density at low rates (less than C/30, where C is the cell capacity in amp-hrs and 30 corresponds to a 30 hr discharge time) was found to be near 300 Wh/kg. An equation which predicts the operating voltage of these cells as a function of current and state of charge is presented. Heat generation rates of these cells were determined as a function of current in a calorimeter. It was found that heat rates could be theoretically predicted with some degree of accuracy at currents less than 1 amp or the C/6 rate. No explosions were observed in the cells during the condition of overdischarge or reversal nor during high rate discharge. It was found, however, that the cells can vent when overdischarge currents are greater than C/30 and when discharge rates are greater than 1.5C.

Frank, H. A.↗
NASA NTRS1981

The diffuse galactic gamma radiation - The Compton contribution and component separation by energy interval and galactic coordinates

The diffuse high-energy galactic gamma radiation to be expected from cosmic ray interactions with matter and photons is considered with particular emphasis on the contribution of Compton radiation from cosmic ray electrons. The intensity, spectrum and spatial distribution of the expected galactic gamma radiation are estimated based on models of the matter, cosmic ray and photon distributions to take into account the contributions of bremsstrahlung, high-energy cosmic-ray nucleon and interstellar matter interactions as well as Compton interactions between cosmic ray electrons and background photons. Results suggest that the Compton gamma ray contribution from cosmic ray electron interactions with galactic visible and infrared photons is substantially larger than previously believed. Analysis of the energy spectra and latitude dependence of the various sources reveals that the Compton radiation, bremsstrahlung and nuclear cosmic ray-matter interaction radiation should be separable, with Compton radiation dominating at energies from 10 to 100 MeV at galactic latitudes greater than several degrees. Results demonstrate the potential of gamma ray observations in studies of galactic structure, cosmic ray electrons and galactic photon density.

Kniffen, D. A.↗
NASA NTRS1981

The ionization state in a gas with a non-Maxwellian electron distribution

The inferred degree of ionization of a gas is often used in astrophysics as a diagnostic of the gas temperature. In the solar transition region and corona, in the outer atmospheres of cool stars, and in some portions of the interstellar medium), photoionization can be neglected, and the ionization state is fixed by the balance between ion-electron collisional ionization and dielectronic and/or radiative recombination. Under these conditions, higher degrees of ionization result from higher energy ion-electron collisions which are common in a high temperature gas. Actually, ionization occurs through collisions with electrons that have kinetic energies greater than the ionization potential of the given ion, and so the ionization rate depends on to the number of such high-energy electrons in the tail of the electron velocity distribution. High-velocity electrons move across large distances between effective coulomb collisions, and, in a strong temperature or density gradient, the tail can be overpopulated relative to Maxwell-Boltzmann distribution of equivalent energy density. Thus, the ionization rate can also be greatly increased. These effects for a parameterized form of the electron distribution function with an enhanced high-velocity tail, namely the kappa distribution are illustrated.

Owocki, S. P.↗
NASA NTRS1983

Eikonal phase shift analyses of carbon-carbon scattering

A high-energy double-folding optical potential approximation to the exact nucleus-nucleus multiple-scattering series is used in determining eikonal phase shifts for carbon-carbon scattering at 204.2, 242.7, and 288.6 MeV. The double-folding potentials are derived by folding the energy-dependent free nucleon-nucleon interaction with densities for the projectile and target; these latter are obtained by unfolding the finite nucleon charge density from harmonic-well carbon charge distributions. The charge parameters for these distributions are taken from the results of electron scattering experiments. Predictions are made for total, reaction, and elastic differential cross sections using standard partial wave analysis for the scattering of identical particles and are then compared with recent experimental results. Excellent agreement is obtained despite the absence of arbitrarily adjusted parameters in the theory.

Townsend, L. W.↗
NASA NTRS1986

Parallel electric fields in extragalactic jets - Double layers and anomalous resistivity in symbiotic relationships

After examining the properties of Coulomb-collision resistivity, anomalous (collective) resistivity, and double layers, a hybrid anomalous-resistivity/double-layer model is introduced. In this model, beam-driven waves on both sides of a double layer provide electrostatic plasma-wave turbulence that greatly reduces the mobility of charged particles. These regions then act to hold open a density cavity within which the double layer resides. In the double layer, electrical energy is dissipated with 100 percent efficiency into high-energy particles, creating conditions optimal for the collective emission of polarized radio waves.

Borovsky, J. E.↗
NASA NTRS1988

Estimating Rates Of Single-Event Upsets

Mathematical model yields estimates of upper and lower bounds on rates of single-event upsets (SEU's) in logic circuits. SEU's are reversible changes in logic states, caused by single high-energy ions. Energetic ions passed through device along tracks perpendicular to surface, to determine parameters of model. Used to estimate rates caused by ions of various energies incident at arbitrary angles. Useful in design of integrated circuits as high-density memories for minimal susceptibility to bit errors.

Zoutendyk, John A.↗
NASA NTRS1987

Voyager 2 plasma ion observations in the magnetosphere of Uranus

Positive ion measurements in the magnetosphere of Uranus have been made by the Voyager 2 plasma science experiment. The paper presents an overview of the entire data set and a detailed analysis of the observations from the inner magnetosphere which complements and extends results reported elsewhere. Densities and temperatures are obtained from an analysis which incorporates details of the instrumental response. These results are then used to calculate flux tube particle and energy content to support the hypothesis that the plasma transport is controlled by a solar wind-driven magnetospheric convection system. Variations in the flux tube content suggest both a local source of plasma, produced from the neutral hydrogen corona of Uranus, and a nonlocal source, convected inwared and heated by adiabatic compression. In each case a proton composition is inferred. Sharp boundaries in the high-energy (approximately 1 keV) plasma population are interpreted in terms of the spatial extent of the magnetospheric convection, with significant shielding of the convection electric field. The convection theory is also used in a simulation of the low-energy (approximately 10 eV) ion component using the neutral hydrogen source, resulting in distribution functions which qualitatively agree with the observations.

Selesnick, Richard S.↗
NASA NTRS1987

The magnetotail of Uranus

The paper describes the characteristics of Uranus' magnetic tail as deduced from Voyager 2 magnetic field and plasma observations, both low energy in the plasma science investigation and high-energy in the low-energy charged particle investigation. The large-scale geometry of the tail is illustrated and the structure and characteristics of the plasma sheet are considered. Included is a discussion of the geometry of the current sheet embedded in the plasma sheet and an estimate of cross-tail current density in the neutral sheet region.

Behannon, K. W.↗
NASA NTRS1988

Hard X-ray emission from a type 2 Seyfert galaxy (NGC 1068)

Exosat observations of the type 2 Seyfert galaxy NGC 1068 have detected a source in the 2-10 KeV range with a flux density at 2 keV of 0.6 micron-Jy. It has a flat power-law spectrum similar to type 1 Seyferts. Combined with Low Energy Exosat filter data and Einstein IPC observations, these data show that spectral curvature is necessary, flattening the X-ray spectrum to high energies. The spectrum can be decomposed into two components: a steep low-energy part and a flat high-energy part. Any intrinsic absorption is small. There is no evidence for variability within or between any of the observations, which sample time scales from 30 minutes to 4 yr. These data support the 'obscuration' model of type 2 Seyfert galaxies in which the nucleus is seen only in flux scattered from above a 'wall' of material that completely blocks the direct view.

Elvis, Martin↗