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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 631 records · Page 35
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NASA NTRS1973

Possibility of Saturnian synchrotron radiation

Several synchrotron spectra are computed for a hypothetical Saturnian radiation belt. A monoenergetic distribution of relativistic electrons is assumed to exist in a toroidal volume in a dipole magnetic field aligned with the rotation axis. When synchrotron emission is added to the thermal component implied by observations at wavelengths shorter than 50 cm, the upturn in the total emission spectrum can become gradual to quite sharp depending on the critical wavelength and the number density of radiating electrons. As an example, the ranges of magnetic field intensity, and electron energy and density are tabulated for an estimate of the nonthermal component at the longest decimetric wavelength observation. The present observations are insufficient to determine the critical wavelength; but, for several estimates of the magnetic field loading factor, the minimum surface magnetic field intensity and minimum electron number density are computed.

Luthey, J. L.↗
NASA NTRS1974

Dissipation of energy in model experiments

Interaction studies of a plasma stream with a magnetic dipole have shown that the thickness of the plasma/field interlayer is considerably greater than the characteristic plasma dimension c/omega sub 0. Broadening of the layer is due to the formation of a collisionless shock wave. To demonstrate collisionless dissipation, the Joulean losses were calculated using the conductivity value obtained from the skin layer thickness. Analysis of the various physical processes showed that the hypothesis of collisionless dissipation of the directional plasma flow is justified.

Podgornyy, I. M.↗
NASA NTRS1975

The motion of a proton in the equatorial magnetosphere

In a time-independent model of the magnetosphere including a dipole magnetic field, a convection electric field (deduced from polar orbit observations), and an electric field due to the earth's rotation, the motion of a proton in the equatorial plane is analyzed. By means of the Hamiltonian of the motion, three regimes of motion are identified. A method is then developed for determining for any given observation point which arrival energies correspond to trapped particles and which represent 'open' trajectories.

Stern, D. P.↗
NASA NTRS1974

Lunar Science Conference, 5th, Houston, Tex., March 18-22, 1974, Proceedings. Volume 1 - Mineralogy and petrology. Volume 2 Chemical and isotope analyses. Organic chemistry. Volume 3 - Physical properties

Numerous studies on the properties of the moon based on Apollo findings and samples are presented. Topics treated include ages of the lunar nearside light plains and maria, orange material in the Sulpicius Gallus formation at the southwestern edge of Mare Serenitatis, impact-induced fractionation in the lunar highlands, igneous rocks from Apollo 16 rake samples, experimental liquid line of descent and liquid immiscibility for basalt 70017, ion microprobe mass analysis of plagioclase from 'non-mare' lunar samples, grain size and the evolution of lunar soils, chemical composition of rocks and soils at Taurus-Littrow, the geochemical evolution of the moon, U-Th-Pb systematics of some Apollo 17 lunar samples and implications for a lunar basin excavation chronology, volatile-element systematics and green glass in Apollo 15 lunar soils, solar wind nitrogen and indigenous nitrogen in Apollo 17 lunar samples, lunar trapped xenon, solar flare and lunar surface process characterization at the Apollo 17 site, and the permanent and induced magnetic dipole moment of the moon. Individual items are announced in this issue.

Gose, W. A.↗
NASA NTRS1975

The plasma sheet boundary and Kp

The paper studies data obtained by the suprathermal ion detector aboard the ATS-1 geostationary satellite in order to establish a relation between the local time occurrence of the plasma sheet at the geostationary orbit (6.6 earth radii) and the Kp index. This relation is then used along with Alfven and Falthammer's (1963) equation for the drift path of an electron moving under the combined influence of a homogeneous electric field and a dipole magnetic field to derive an expression that shows the manner in which the inner boundary of the plasma sheet can be expected to vary radially with Kp along the midnight meridian for Kp less than about 4.

Freeman, J. W.↗
NASA NTRS1975

Note on the electric splitting of drift shells

A nonrelativistic analysis is presented for the deviation of a particle from its dipole magnetic drift shell in the presence of an electric field. An alternative definition of weak shell splitting is introduced in which the corotation drift velocity need not be small with respect to the azimuthal magnetic drift velocity. Approximate explicit solutions are obtained for the asymmetry of drift shells in the strong shell splitting case, i.e., for the case where the cross-magnetosphere potential drop is not small compared to particle kinetic energy. Upper limits to drift shell asymmetry are obtained from considerations of the Alfven layer.

Kivelson, M. G.↗
NASA NTRS1975

Approximations for the study of drift boundaries in the magnetosphere

An approximate relation between energy and equatorial radial distance for a particle of given equatorial pitch angle moving adiabatically in a dipole magnetic field is used to describe the Alfven layer for particles of arbitrary pitch angle. The convection electric field is assumed to be uniform in the equatorial plane of the magnetosphere, and magnetic field lines are taken to be equipotentials in the region traversed by the magnetospheric particles being studied. Approximate solutions in the high- and low-energy limits are given in a form directly applicable to the interpretation of measurements at fixed particle energy and pitch angle. These results are particularly useful for electrons, since the approximations provide lower bounds to the exact solutions. The results are used to interpret recent Explorer 45 electron measurements of Williams et al. (1974).

Kivelson, M. G.↗
NASA NTRS1976

Trajectory Traces of Charged Particles in the Magnetosphere

The characteristic enhancements of ring current particles with energies of about 1 to 100 keV, associated with magnetospheric substorms, were observed by Explorer 45 around the plasmapause in the afternoon to midnight region, and showed the characteristic structure called a 'nose' in the proton spectrograms. The motion of these particles in the equatorial magnetosphere, under a recently proposed convection electric field and a dipole magnetic field is described. Approximate equations of a bounce period, a second adiabatic invariant, and a bounce-average azimuthal velocity are given with inaccuracies less than about 0.001 for all pitch angles. The complete set of flow patterns of 90 deg pitch angle particles is also presented by means of stagnation lines through which radial drifts and/or azimuthal drifts change their directions. The particle tracings in the magnetosphere give a basic concept to explain the observed nose characteristics.

Ejiri, M.↗
NASA NTRS1975

Flux limit on cosmic ray acceleration by strong spherical pulsar waves

The study investigates the acceleration of cosmic rays by superrelativistic plasma waves. The pulsar wave field imposed upon the particles is that of a magnetic dipole wave including azimuthal dependence and near field terms. The refractive index of the plasma is assumed to be constant everywhere. Two distinct zones appear: in the near zone spherical effects dominate, particles may be decelerated; in the far zone the results for the motion differ noticeably from the vacuum case. From a WBK-like treatment for a spherical S wave, it is concluded that for a wave solution to be valid even near the light cylinder, the wave can carry a sufficiently small particle flux.

Asseo, E.↗
NASA NTRS1976

The magnetic moment of Venus - Venera-4 measurements reinterpreted

Venera-4 magnetic-field measurements made during that spacecraft's descent through the atmosphere of Venus are reexamined using three models for the interaction of the solar-wind with the planet. The first model assumes the existence of just the interplanetary and planetary magnetic fields; the second admits the presence of a magnetosheath and a current layer, but assumes that the magnetosheath field is spatially uniform between the planet and the bow shock; the third assumes shielding of the planetary field from the magnetosheath field by a current layer. All three models are found to yield a strong altitude dependence for the magnitude of the planetary field, suggesting that the intrinsic magnetic dipole moment of Venus may exceed that of both Mars and Mercury. It is concluded that a Venusian surface field of 30 gammas is a plausible interpretation of the Venera-4 measurements.-

Russell, C. T.↗
NASA NTRS1976

Intensity measurements for the /2, O/ gamma-band of O2, b 1Sigma-g/+/ - X 3Sigma-g/-/

Line intensities for the P sub P and P sub Q branches of the (2-O) vibrational band of the magnetic dipole electronic transition for the oxygen red system at 6280 A were measured, and the sum of the R sub R and R sub Q branch intensities was taken. A large number of repetitive spectral scans were required for accuracy, because of low absorption values even at optical path lengths from 300 to 600 m. A total of 557 individual measurements of P-branch lines yielded an intensity value for the P-branches, and equivalent widths for 24 spectral scans yielded an intensity value for the R-branch. R-branch to P-branch intensity ratios were taken for the A-band, B-band, and gamma-band (respectively, O-O at 7620 A, 1-O at 6880 A, and 2-O at 6280 A). Intensities for some rotational lines are found, and effects of combined rotation-vibration interaction are probed.

Miller, J. H.↗
NASA NTRS1976

Injection boundary dynamics during a geomagnetic storm

A series of proton and electron injections were observed by Explorer 45 associated with several substorms during the main phase of the Feb. 24, 1972 geomagnetic storm. The 1- to 290-keV protons and 1- to 560-keV electrons were observed in the evening quadrant up to L of about 5.2. A model distorted dipole magnetic field and McIlwain's E3 convection electric field were used to backtrack the energy-dispersed electron and proton fluxes to their source at the time of injection. The source turns out to be a region extending over several earth radii outside an injection boundary. In the night magnetosphere, the inferred injection boundary is displaced inward with each successive substorm. The energy dispersion plot of the particles injected during orbit 314 indicates that as the energy of the observed particles decreases there is a smooth transition to the position of the plasmapause. This suggests that for that substorm the injection boundary and the plasmapause were one and the same. The proton 'noses' reported by Smith and Hoffman (1974) are discussed.

Konradi, A.↗
NASA NTRS1976

Hercules X-1: Spectral Variability of an X-Ray Pulsar in a Stellar Binary System

A cosmic X-ray spectroscopy experiment onboard the Orbiting Solar Observatory 8 (OSO-8), observed Her x-1 continuously for approximately 8 days. Spectral-temporal correlations of the X-ray emission were obtained. The major results concern observations of: (1) iron band emission, (2) spectral hardening (increase in effective x-ray temperature) within the X-ray pulse, and (3) a transition from an X-ray low state to a high state. The spectrum obtained prior to the high state can be interpreted as reflected emission from a hot coronal gas surrounding an accretion disk, which itself shields the primary X-ray source from the line of sight during the low state. The spectral hardening within the X-ray pulse was indicative of the beaming mechanism at the neutron star surface. The hardest spectrum by pulse phase was identified with the line of sight close to the Her x-1 magnetic dipole axis, and the X-ray pencil beam become harder with decreasing angle between the line of sight and the dipole axis.

Pravdo, S. H.↗
NASA NTRS1976

Forbidden transition probabilities for ground terms of ions with p or p5 configurations

Forbidden transition probabilities are given for ground term transitions of ions in the isoelectronic sequences with outer configurations 2s2 2p (B I), 2p5 (F I), 3s2 3p (Al I), and 3p5 (Cl I). Tables give, for each ion, the ground term interval, the associated wavelength, the quadrupole radial integral, the electric quadrupole transition probability, and the magnetic dipole transition probability. Coronal lines due to some of these ions have been observed, while others are yet to be observed. The tales for the Al I and Cl I sequences include elements up to germanium.

Kastner, S. O.↗
NASA NTRS1976

On the source of the ancient lunar magnetic field

Analysis of the returned samples, surface observations, and the orbital surveys reveal the presence of a widespread magnetism on the lunar surface but no global field. In the light of Runcorn's proof that internally generated fields do produce magnetization patterns in a spherical crust whose magnetic field lines are confined to within the crust, the above fact is explained in terms of an ancient lunar dynamo which magnetized the lunar crust and then disappeared. The possibility of ancient uniform magnetization by an external field is ruled out, for such magnetization would have been erased as the moon warmed up due to radioactive decay. Although the terrestrial field model is consistent with the measurements, this possibility is also ruled out, because the moon would have had to remain close to earth for about one billion years. The direction of the present magnetization is not predominantly north-south, but is radial and east-west, a fact explained by the assumption that the ancient lunar magnetic dipole moment was not along the present rotation axis.

Russell, C. T.↗
NASA NTRS1977

Observations at the planet Mercury by the plasma electron experiment - Mariner 10

Two nightside encounters with Mercury's magnetosphere by Mariner 10 revealed bow shock and magnetosheath signatures in the plasma electron data that are entirely consistent with the geometry expected for an interaction between a planet-centered magnetic dipole and the solar wind. The geometrically determined distance between the planet's center and the solar wind stagnation point is 1.4 plus or minus 0.1 R sub M. Both diffuse and sharp shock crossings were observed on the two magnetosphere encounters.

Ogilvie, K. W.↗
NASA NTRS1978

Magnetosphere of Saturn

Models of the Saturnian magnetosphere based on the application of magnetospheric scaling relations to a spin-aligned planetary magnetic dipole, that produces a surface equatorial field strength in the range 0.5 to 2 gauss, exhibit the following properties: (1) The orbit of Titan lies inside of the magnetosphere essentially all of the time, even when variations in the size of the magnetosphere resulting from solar wind pressure changes are taken into account; (2) the Brice-type planetary plasmasphere reaches a peak density of about 10 protons cm/3 at L approximately 7 (L = planetocentric distance in units of planetary radii); (3) Saturn's rings have a profound effect on the energetic particle population and the plasmaspheres derived from interstellar neutrals and Titan's torus; (4) the model calculation suggests that the Titan-derived plasmasphere may be self-amplifying with a feed-back factor greater than unity, which implies the possibility of a non-linearly saturated, highly inflated Saturnian magnetosphere; and (5) this same source can have important eroding effects on the outer edge of the rings determined by Brown-Lauzerotti sputtering rates.

Siscoe, G. L.↗
NASA NTRS1979

The 63 micron radiation field in the earth's thermosphere and its influence on the atomic hydrogen temperature

The thermal escape of hydrogen from the earth's atmosphere is strongly affected by its temperature at the exobase. It has been suggested recently that the hydrogen temperature might be significantly lower than the thermospheric temperature as a result of a collisional exchange of energy with atomic oxygen. The tendency is to cool the hydrogen since the energy of the excited 3P1 level of oxygen can be lost from the atmosphere via magnetic dipole emission of the micron line (3P2-3P1). A detailed calculation of the net cooling effect as a function of altitude throughout the thermosphere is presented. The calculations have been performed for both day and night conditions and for periods of maximum and minimum solar activity conditions. It is found that its effect on Delta T/T varies from a very small value to a maximum of about 3%. The theoretical framework for describing deviations of the 63 micron emission from local thermodynamic equilibrium is given and it is shown that these effects can cause the emission to be reduced by as much as 40% near 500 km.

Durrance, S. T.↗