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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1968

Nonlinear oscillations in a cold plasma.

Nonlinear large amplitude electrostatic and electromagnetic oscillations in cold plasma having one dimensional spatial variations and fixed neutralized ion background

Davidson, R. W. C.↗
NASA NTRS1972

Biological cycling of atmospheric trace gases

A detailed critical review was conducted of present knowledge of the influence of biological processes on the cycling of selected atmospheric gas constituents--methane, carbon monoxide, and gaseous compounds of nitrogen (nitrous oxide, ammonia, nitric oxide, and nitrogen dioxide) and sulfur (hydrogen sulfide and sulfur dioxide). The identification was included of biological and other sources of each gas, a survey of abundance measurements reported in the literature, and a review of the atmospheric fate of each contituent. Information is provided on which to base conclusions regarding the importance of biological processes on the atmospheric distribution and surface-atmosphere exchange of each constituent, and a basis for estimating the adequacy of present knowledge of these factors. A preliminary analysis was conducted of the feasibility of monitoring the biologically influenced temporal and spatial variations in abundance of these gases in the atmosphere from satellites.

Hitchcock, D. R.↗
NASA NTRS1972

Explorer 33 and 35 plasma observations of magnetosheath flow.

Mapping of the magnetosheath flow in the region -60 earth radii less than or equal to X sub SE less than or equal to -20 earth radii by using plasma data from the MIT plasma experiments on the earth-orbiting Explorer 33 and the lunar-orbiting Explorer 35. Temporal and spatial variations in the flow are separated by using 309 hours of simultaneous data from the two spacecraft, one spacecraft being in the solar wind and the other spacecraft in the magnetosheath. The overall flow pattern agrees well with the predictions of a simplified hydrodynamic theory. The measured ratio of magnetosheath to solar-wind densities is shown to have some dependence on the observed solar-wind sonic Mach number. This density ratio is consistently less than 1 in the region adjacent to the magnetotail boundary and thus reflects the irreversible nature of the flow across the bow shock.

Howe, H. C., Jr.↗
NASA NTRS1972

The derivation of temperature gradient and electron density maps from EUV spectroheliograms.

We discuss spatial variations in electron density at the base of the corona and in the temperature gradient in the chromospheric-coronal transition layer as determined from analysis of maps constructed from Mg X and O VI spectroheliograms. Both the mapping techniques and results of analyzing EUV spectra from OSO 6 observations are presented. Comparisons of these maps with photospheric magnetograms and spectroheliograms made in chromospheric EUV lines and continua indicate that the electron density and temperature gradient in the transition layer tend to be enhanced in areas where the photospheric magnetic field and chromospheric EUV emission are enhanced. Relationships among the coronal electron density, transition-layer temperature gradient, chromospheric emission, and photospheric magnetic field strength are derived.

Withbroe, G. L.↗
NASA NTRS1972

The relationship of theory and experiment in the D-region.

To monitor the descriptive parameters of the lower ionosphere and construct a model which predicts their temporal and spatial variations is a particularly difficult task. In a given situation simultaneous measurements should be conducted of ionization sources, the altitude distribution of all neutral atmospheric constituents, the identification, number density, and altitude distribution of different species of positive and negative ions and electrons. These results are compared with theoretical predictions to serve as boundary conditions and guides to modification of the theory. It has not been possible to realize this goal in lower ionosphere research because of the large number of parameters and since certain parameters, such as positive ion species distribution and nitric oxide, can only be measured with the aid of sounding rockets. To illustrate the difficulty, recent positive ion composition measurements are compared with predictions utilizing clustering of ions and neutrals to form hydrated ions.

Aikin, A. C.↗
NASA NTRS1973

Simultaneous particle and field observations of field-aligned currents

Simultaneous measurements of low energy precipitating electrons and magnetic fluctuations from the low altitude polar orbiting satellite OGO-4 have been compared. Analysis of the two sets of experimental data for isolated events led to the classification of high latitude field-aligned currents as purely temporal or purely spatial variations. Magnetic field disturbances calculated using these simple current models and the measured particle fluxes were in good agreement with measured field values. While fluxes of greater than 1 keV electrons are detected primarily on the nightside, magnetometer disturbances indicative of field-aligned currents were seen at all local times, both in the visual auroral regions and dayside polar cusp. Thus electrons with energies less than approximately 1 keV are the prime charge carriers in high latitude dayside field-aligned currents. The satellite measurements are in good agreement with previously measured field-aligned current values and with values predicted from several models involving magnetospheric field-aligned currents.

Berko, F. W.↗
NASA NTRS1973

Observations of the He II 304-A radiation in the night sky.

The intensity and spatial variations of the He II 304-A radiation in the night sky were measured to an altitude of 264 km from a sounding rocket launched from Thumba, India, on Mar. 10, 1970. The data obtained are presented in the form of an all-sky map and are compared with theoretical predictions. The data are not consistent either with diffusive equilibrium models of exospheric helium or with plausible models of helium in the interplanetary medium. The data can be fit with a constant-density plasmasphere model bounded at the magnetic shell L = 4 in combination with a tenuous gas of helium ions in the plasma sheet. Numerical results obtained with this model are compared with in situ satellite observations.

Paresce, F.↗
NASA NTRS1973

On the structure of the magnetotail current sheet.

A self-consistent tail current sheet model described by an exact analytic solution of the time-independent Vlasov-Maxwell equations is presented. The model has a 'slingshot' field configuration with field lines outside the plasma sheet slightly flared in the antisolar direction. It is pointed out that when the model parameters are adjusted to agree with the spatial variation along the tail the required thickness of the neutral sheet must be about 2.5 earth radii, instead of less than or equal to 1 earth radius, as indicated by observations. Furthermore, it is shown qualitatively that a considerable velocity shear must be present in the tail current sheet if the plasma sheet is indeed much thicker than the neutral sheet.

Kan, J. R.↗
NASA NTRS1973

Magnetospheric modulation effects on solar cosmic rays from simultaneous OGO 1 and 3 ion chamber data in 1968 and 1969

Simultaneous observations by identical ionization chambers aboard the satellites OGO-1 and OGO-3 are utilized to investigate spatial variations in particle intensity near and inside the magnetosphere during the solar cosmic ray events of September 1966. Cross-correlation of the absolute proton flux computed from the chamber rate during three solar particle events shows good agreement with the measurements by the IMP-F Solar Proton Monitor during the same events. The chamber has a dynamic range of over six orders of magnitude. Before launch it was calibrated in the laboratory with radiation dosages in the range 1 R/hr-6000 R/hr. The OGO-1 and OGO-3 chambers, which were normalized in the laboratory prior to the launch, are found to maintain their normalization within approximately equal to 1 per cent during their flight. The high sensitivity and absolute inter-comparability of the instruments allow small intensity differences to be detected and it is established that the observed differences can be explained by a magnetospheric screening effect when an anisotropic beam of particles is present in space. Evidence is presented to show that the screening is at times complete for a duration of as much as 110 min in the tail of the magnetosphere so that during this period the solar cosmic rays (E approximately equal to 15 MeV) have virtually no access to that region of the magnetosphere. Small intensity fluctuations of a temporal nature observed and found to be subjected to a damping effect inside the magnetosphere.

Hofmann, D. J.↗
NASA NTRS1974

Observations of He I 584 A nighttime radiation - Evidence for an interstellar source of neutral helium

The intensity and spatial variations of the He I 584 A radiation in the night sky were measured to an altitude of 264 km from a sounding rocket launched from Thumba, India. The flux varied in intensity with look angle from a high of 16 plus or minus 5 rayleighs to a low of less than 1 rayleigh. The data obtained are presented in the form of an all-sky map. Since the peak flux levels observed are approximately two orders of magnitude larger than that expected from geocoronal resonant scattering, we have compared our results with those expected from two interplanetary sources of neutral helium: the penetration of the local interstellar medium into the solar neighborhood and the dust deionization of solar-wind alpha particles. The dust deionization-model predictions using currently accepted input parameters appear to be inconsistent with the observations. The interstellar helium source is compatible with the data to within the uncertainties of the models.

Paresce, F.↗