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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Model development of supersonic trough wind with shocks.

The time-dependent one dimensional hydrodynamic equations describe the evolution of the thermal plasma flow along closed magnetic field lines outside of the plasmasphere. The convection of the supersonic polar wind onto a closed field line results in the assumed formation of collisionless plasma shocks. These shocks move earthward as the field line with its 'frozen-in' plasma remains fixed or contracts with time to smaller L coordinates. The high equatorial plasma temperature (of the order of electron volts) produced by the shock process decreases with time if the flow is isothermal, but it will increase if the contraction is under adiabatic conditions. Assuming adiabaticity a peak in the temperature forms at the equator in conjunction with a depression in the ion density. After an initial contraction, if the flux tube drifts to higher L coordinates, the direction of the shock motion can be reversed so that the supersonic region will expand along the field line toward the state characterizing the supersonic polar wind.

Grebowsky, J. M.↗
NASA NTRS1975

The equatorial helium ion trough and the geomagnetic anomaly

The latitudinal characteristics of He+ in the equatorial region are compared with those of O+ and H+. These ions, in different altitude regions, exhibit certain features which are characteristics of the ionospheric geomagnetic anomaly. It is shown that the latitudinal distributions of these ions are related to their vertical distribution at the equator via their respective scale heights and the geomagnetic dipole geometry. To a first order, the positions of the latitudinal maxima of a given ion may be related to its peak altitude at the equator by a proposed expression.

Chandra, S.↗
NASA NTRS1980

Conceptual design study of concentrator enhanced solar arrays for space applications. Performance evaluation of 5 KW and 20 KW systems in Si and GaAs at 1 AU employing a flat plate trough concentrator

A simple, efficient and very lightweight preliminary design for a 5 KW and 20 KW BOL output concentrated array evolved and is described by drawings. The relative effectiveness of this design, as compared to an unconcentrated planar array of equal power output, was measured by comparing power to mass performance of and the solar cell area required by each. Improvements in power to mass performance as high as 42% together with array area size reduction of 57% are possible in GaAs systems. By contrast, when the same concentrator design is applied to silicon systems, no improvement in power to mass can be obtained although array area reductions as high as 35% are obtainable.

Source record↗
NASA NTRS1983

Characteristics of thermal and suprathermal ions associated with the dayside plasma trough as measured by the dynamics explorer retarding ion mass spectrometer

The thermal and suprathermal ion populations present in the refilling regions after a magnetic storm are examined using retarding ion mass spectrometer (RIMS) data from the Dynamics Explorer 1 spacecraft. The RIMS instrument is described, and data are presented and discussed in detail for the outer plasmasphere, plasmapause, depleted dayside magnetosphere, and dayside cusp. Three distinct populations were observed: thermal ions, warm anisotropic plasma, and the polar wind. The characteristics of these populations are considered, including the densities, temperatures, and density ratios. Aspects of the ionospheric plasma outflow are discussed, including the field-aligned flow speed, the ionospheric plasma escape flux, plasmaspheric refilling, and wave-particle phenomena.

Sojka, J. J.↗
NASA NTRS1983

Characteristics of low-energy plasma in the plasmasphere and plasma trough

Initial results of studies of low-energy plasma using the light ion mass spectrometer (LIMS) on the SCATHA satellite are presented. Results are discussed primarily for plasma flux in the noon to midnight local time sector, examining the behavior of the plasma with geomagnetic activity and local time. Measurements of the ion mass composition in this region for the energy ranges of the LIMS instrument are presented. Results of temperature measurements are given and a possible explanation for the difference between the whistler and OGO 5 plasmapause positions is suggested. The observed pitch angle distributions are presented, limited to a broad characterization of the plasma population. The effects of the spacecraft potential on the low-energy plasma measurements are considered.

Reasoner, D. L.↗
NASA NTRS1989

VLF emission bursts in the terrestrial and Venusian nightside troughs

It is shown here that the 100-Hz emission bursts in the Venusian nightside ionosphere are remarkably similar to those of the terrestrial VLF saucer emissions in terms of their spatial and temporal characteristics and the properties of their magnetoplasma environment. It is proposed that the generation mechanism for such VLF sources should be considered as a viable alternative to lightning as a source of Venusian ionospheric whistler-mode emissions.

Maeda, Kaichi↗
NASA NTRS1993

Cirrus cloud development in a mobile upper tropospheric trough: The November 26th FIRE cirrus case study

The period from 18 UTC 26 Nov. 1991 to roughly 23 UTC 26 Nov. 1991 is one of the study periods of the FIRE (First International Satellite Cloud Climatology Regional Experiment) 2 field campaign. The middle and upper tropospheric cloud data that was collected during this time allowed FIRE scientists to learn a great deal about the detailed structure, microphysics, and radiative characteristics of the mid latitude cirrus that occurred during that time. Modeling studies that range from the microphysical to the mesoscale are now underway attempting to piece the detailed knowledge of this cloud system into a coherent picture of the atmospheric processes important to cirrus cloud development and maintenance. An important component of the modeling work, either as an input parameter in the case of cloud-scale models, or as output in the case of meso and larger scale models, is the large scale forcing of the cloud system. By forcing we mean the synoptic scale vertical motions and moisture budget that initially send air parcels ascending and supply the water vapor to allow condensation during ascent. Defining this forcing from the synoptic scale to the cloud scale is one of the stated scientific objectives of the FIRE program. From the standpoint of model validation, it is also necessary that the vertical motions and large scale moisture budget of the case studies be derived from observations. It is considered important that the models used to simulate the observed cloud fields begin with the correct dynamics and that the dynamics be in the right place for the right reasons.

Mace, Gerald G.↗
NASA NTRS1994

Topography of Valles Marineris: Implications for erosional and structural history

Compilation of a simplified geologic/geomorphic map onto digital terrain models of the Valles Marineris permitted an evaluation of elevations in the vicinity of the troughs and the calculation of depth of troughs below surrounding plateaus, thickness of deposits inside the troughs, volumes of void spaces above geologic/geomorphic units, and volumes of deposits. The central troughs north Ophir, north and central Candor, and north Melas Chasmata lie as much as 11 km below the adjacent plateaus. In Ophir and Candor chasmata, interior layered deposits reach 8 km in elevation. If the deposits are lacustrine and if all troughs were interconnected, lake waters standing 8 km high would have spilled out of Coprates Chasma onto the surrounding plateaus having surface elevations of only 4-5 km. On the other hand, the troughs may not have been interconnected at the time of interior-deposit emplacement; they may have formed isolated ancestral basins. The existence of such basins is supported by independent structural and stratigraphic evidence. The ancestral basins may have eventually merged, perhaps through renewed faulting, to form northern subsidiary troughs in Ophir and Candor Chasmata and the Coprates/north Melas/Ius graben system. The peripheral troughs are only 2-5 km deep, shallower than the central troughs. Chaotic terrain is seen in the peripheral troughs near a common contour level of about 4 km on the adjacent plateaus, which supports the idea of release of water under artesian pressure from confined aquifers. The layered deposits in the peripheral troughs may have formed in isolated depressions that harbored lakes and predated the formation of the deep outflow channels. (If these layered deposits are of volcanic origin, they may have been emplaced beneath ice in the manner of table mountains.) Areal and volumetric computations show that erosion widened the troughs by about one-third and that deposits occupy one-sixth of the interior space. Even though the volume eroded is larger than the volume deposited, topographic and geologic considerations imply that material eroded from trough walls was probably part of the interior layered deposits but not their sole source. Additional material may have come from subterranean piping, from reworking of local disintegration products on the floors, such as chaotic materials, or from eolian influx. But overall it is likely that the additional material is volcanic and that it forms mostly the upper, more diversely bedded layers of the interior deposits.

Lucchitta, B. K.↗
NASA NTRS1993

Fault geometries and extension in the Valles Marineris, Mars

The central troughs of the Valles Marineris system on Mars are generally regarded to be of tectonic origin because they are linear and bounded by faults. Their radial orientation to the Tharsis rise suggests that at least their incipient formation was influenced by the formation of the rise, but the exact role of Tharsis is not yet well understood. Collapse and erosion may have significantly modified the original tectonic troughs. To better understand the magnitude and mechanism of crustal extension across the Valles Marineris, the attitudes of trough-wall faults that parallel the long axes of the troughs were studied. Our results will help to determine if the extension is related to the Tharsis rise, to a local arch along which the troughs lie, or to other mechanisms. Fault-plane attitudes were obtained by performing a photogrammetric study of fault traces in the walls of Candor and Melas Chasmata. If the exposed wall faults are not major trough-bounding faults, it is assumed that these major faults are buried at the base of the walls and have similar geometries to the exposed faults. Three dimensional coordinates of several points along each fault trace were obtained and three-point solutions to their geometries were constructed. As expected, the results show that the faults dip toward the interior of the troughs, suggesting that they are indeed normal faults associated with trough formation.

Chadwick, D. J.↗