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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Substorm effects observed in the auroral plasma

The effects of substorm temporal development on high-latitude particle precipitation and ionospheric convection patterns near midnight were studied with the aid of data from Atmosphere Explorer C. During quiet periods generally Maxwellian electron precipitation is observed from the central plasma sheet, which is completely contained within the sunward flow region. As substorms grow and begin to recover, a strong sunward flow appears within the high latitude ionospheric electron trough, equatorward of the central plasma sheet electron precipitation. Intense inverted-V electron structures consistent with strong electrostatic acceleration appear near the Harang discontinuity and extend poleward to the polar cap boundary. Then the trough flow weakens, the Harang discontinuity becomes a gradual reversal, and the electron inverted-V precipitation becomes localized at the polar cap boundary.

Burch, J. L.↗
NASA NTRS1977

The geology of the Viking Lander 2 site

Models are discussed of several competitive geologic histories that can be hypothesized for the Viking Lander 2 site, none of which is uniquely persuasive. The craft landed on a flat plain of fine-grained sediment overlain by dispersed evenly distributed boulders. The fine-grain material appears to be part of a high-latitude mantle comprising material swept south of the pole regions. The boulders, which are covered by distinctive deep pits, or vesicles, may be the residue of an ejecta deposit from the crater Mie. Alternatively, they may be the remnants of lava flows which formerly covered the region. Polygonal sediment-filled cracks may have been formed by ice wedging, similar to the process that occurs in terrestrial permafrost regions. The possibility that they are desiccation polygons may not be excluded.

Mutch, T. A.↗
NASA NTRS1978

Helium ion outflow from the terrestrial ionosphere

For situations where ion outflow occurs from the topside ionosphere, steady-state solutions for the He(+) continuity, momentum, and energy equations have been obtained self-consistently, yielding density, velocity, and temperature profiles of He(+) from 200 to 2000 km altitude. The study indicates that the outflowing He(+) has density profiles of similar shape to those of H(+), for basically different reasons; the effect of the perpendicular electric field differs considerably for H(+) and He(+); the fractional heating of He(+) due to the He(+)-O(+) relative flow is not as effective in heating He(+) as the flow is in heating H(+); during magnetospheric disturbances the He(+) peak density decreases only by approximately a factor of 2; and the He(+) escape flux over the winter pole is approximately a factor of 20 greater than the He(+) escape flux over the summer pole. The possibility of interhemispheric He(+) flux from winter to summer on high-latitude closed field lines is considered.

Raitt, W. J.↗
NASA NTRS1978

Mariner 9 television limb observations of dust and ice hazes on Mars

Results are presented for a statistical analysis of over 3000 Mariner 9 television reflectance profiles of the planetary limb of Mars for the period from the decaying phase of a global dust storm (southern summer) to southern winter solstice. It is shown that during the decaying phase of the storm, the dust is maintained aloft to high elevations by vertical mixing primarily in the equatorial zone, apparently by the direct or indirect action of the diurnal tide; the result is that the dust decay is much faster in high-latitude regions than near the equator. Significant dust remains aloft in Martian equatorial regions long after the major dust storms have subsided. At the top of the dusty atmosphere, a region exists where temperatures relax toward values expected for a dust-free CO2 atmosphere; this is therefore a region of convective overturning topped by thin condensation hazes resembling terrestrial noctilucent clouds, thereby showing occasionally gravity wave structures.

Anderson, E.↗
NASA NTRS1978

The flute instability as the trigger mechanism for disruption of cometary plasma tails

The sporadic disruption of the plasma tails of some comets has recently been explained to be caused by magnetic-field-line reconnection in the cometary ionospheres due to magnetic-sector-boundary traversals. An alternative model is proposed in which the tail disruption is the end result of compression of the cometary ionosphere by high-velocity solar-wind streams, triggering the flute instability in the marginally stable tangential-discontinuity surface which separates the cometary ionosphere from the solar-wind plasma. According to the proposed model, the tail-disruption events could occur at all heliographic latitudes, whereas the Niedner-Brandt (1978) model should predict that these events are restricted to low heliographic latitudes in view of the present understanding of the sector structure of the heliosphere. Consequently, the high-latitude disruption events observed seem to present a difficulty for the latter model.

Ip, W.-H.↗
NASA NTRS1978

Some characteristics of electric field momentum coupling with the neutral atmosphere

A three-dimensional model has been developed to describe momentum coupling between high-latitude electric fields, neutral winds, temperature, and composition. The Hall drag is found to be the main source for atmospheric winds and the small divergence component of winds is due to the Pedersen drag and the Hall drag. Adiabatic heat transfer is responsible for the back pressure which damps the divergence field and for the reversal in circulation of the divergence field at higher altitudes. Back pressure causes a decrease in total wind velocity of about 10% at exospheric heights and by a factor of about 2 at 120 km. The wind field with the pressure feedback may be simulated by neglecting pressure variations and the Coriolis force. Density variations of Ar, N2, O, and He, induced by the momentum source, are in phase above 120 km and out of phase with the temperature amplitude above 150 km. The electrostatic field momentum source is ineffective for directly inducing density and temperature variations in the upper thermosphere.

Mayr, H. G.↗
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

Relationships between particle precipitation and auroral forms

The paper discusses recent measurements pertaining to the relationship between high-latitude particle (electron) precipitation and auroras. The discussion covers three topics: the large-scale relationships between auroral forms and the particle populations of the magnetosphere as determined from satellite measurements; (2) the relationship between satellite and sounding-rocket observations, particularly field-aligned pitch-angle distributions and upward field-aligned currents measured in the vicinity of auroral forms; and (3) recent results on the interaction of auroral electrons with the atmosphere.

Burch, J. L.↗
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 NTRS1978

A review of the near-earth radiation environment

The spatial volume surrounding the earth out to 30 earth radii has been divided into the five regions known as the interplanetary medium, magnetosheath, plasma sheet, high-latitude magnetotail, and inner magnetosphere. In each region, the primary attributes of the particle populations and available models are described, and integral energy spectra covering the range from 10 to 10 billion eV are shown. The effects of the solar cycle on future projections are discussed.

Sawyer, D. M.↗
NASA NTRS1979

A possible 2-day oscillation near the tropical stratopause

An examination of daily meteorological rocket data taken during January and February 1977 at Kwajalein, Marshall Islands (9 deg N, 168 deg E) suggests the presence of a large oscillation in the meridional wind with a period near 2 days. Some rocket data taken concurrently at other stations is also presented. The Canal Zone station (9 deg N, 80 deg W) suggests a possible 2-day oscillation, while middle- and high-latitude stations show variability with periods ranging from 2-5 days.

Coy, L.↗
NASA NTRS1979

Observations pertaining to the dynamics of the plasma sheet

Plasmas on the surface of the plasma sheet at its interface with high-latitude lobes are studied at about 30-40 earth radii (Re) in the tail of the earth's magnetosphere with Lepedea plasma instrumentation on board the earth-orbiting Imp 7 and Imp 8 satellites. Protons at this interface are frequently found to be flowing toward earth with velocities greater than 400 km/s. Proton bulk speeds measured near the plasma sheet surface are typically greater than those at locations deeper within the plasma sheet. Ten of the twenty cases studied exhibit plasma sheet cooling. Typical plasma sheet conditions are observed to prevail deep within the plasma sheet coincident with the earthward streaming at the boundary of the plasma sheet. A three-parameter model is described that explains the velocity distributions measured for the earthward-jetting plasma.

Decoster, R. J.↗
NASA NTRS1979

Faint extragalactic objects and the unidentified high latitude X-ray sources

Classes of extragalactic objects that have been identified with faint high-galactic-latitude X-ray sources in the Fourth Uhuru and Ariel 5 Catalogs are examined. Sources with declinations of at least -30 deg, galactic latitudes of at least 20 deg (absolute value), and error boxes of 1.0 sq deg are considered. It is shown that clusters of galaxies constitute the most numerous class of extragalactic sources and that Seyfert galaxies are the next largest class. Unidentified high-latitude X-ray sources are discussed. Preliminary results obtained with the A-1 instrument aboard HEAO 1 are reported which indicate that a substantial fraction of unidentified sources are highly variable and may be identified with active galaxies.

Shulman, S.↗
NASA NTRS1979

ISEE 1 and 2 particle observations of outer plasma sheet boundary

Observations of particle structures by a medium-energy particle experiment on the ISEE 1 and 2 spacecraft at a distance of about 20 earth radii in the geomagnetic tail are presented. Comparison of these data with plasma data indicates the existence of a layer of energetic electrons and ions just outside the plasma sheet. The region outside the plasma sheet in the high-latitude lobe is permeated with low-intensity low-energy (about 1.5 KeV) ions. These particle structures have velocities of a few kilometers per second to at least about 60 km/s. Large-scale motions are observed with onset and recovery of substorms. The dimensions of the particle structures are estimated to range from about 200 to 10,000 km at 20 earth radii. The particle structures are dependent upon the energy as well as the species of the particles.

Parks, G. K.↗
NASA NTRS1979

An experimental search for causal mechanisms in sun/weather-climatic relationships

The paper presents a description of and preliminary results from an ongoing program designed to study mesospheric and stratospheric responses to specific corpuscular radiations induced by solar activity. Satellite data are used to map correlations between O3 variability and high-latitude energetic phenomena. Two rocket/balloon programs have already been conducted to measure local changes of O3 and electrical parameters in situ, while simultaneously studying the parent electron distributions responsible for the incoming radiations. Plans for mapping the global input of electron precipitation events from the Spacelab are also discussed.

Goldberg, R. A.↗
NASA NTRS1979

Overview of NASA solar physics programs

The program of solar physics missions for the 1980's will include earth-orbiting and solar-orbiting free flying satellites as well as Shuttle sorties carrying large facility instruments and smaller PI-class investigations. Individual missions will have specific, unifying objectives in contrast to the exploratory nature of missions of the 1960's and 70's. The Solar Maximum Mission will study solar flares in 1980 and 1981. The International Solar Polar Mission will swing past Jupiter and traverse the Sun's polar caps in 1986, measuring the high-latitude solar wind. Three of the early Shuttle flights will carry PI-class solar experiments, and the Solar Optical Telescope, to fly in about 1984, will provide extremely high spatial resolution of solar features. Possible future missions include the Solar Cycle and Dynamics Mission to study the Sun's magnetic cycle, and the Solar Probe, which will pass within 4 solar radii of the Sun's surface.

Chipman, E.↗
NASA NTRS1979

A quasi-static model of global atmospheric electricity. II - Electrical coupling between the upper and lower atmosphere

The paper presents a model of global atmospheric electricity used to examine the effect of upper atmospheric generators on the global electrical circuit. The model represents thunderstorms as dipole current generators randomly distributed in areas of known thunderstorm frequency; the electrical conductivity in the model increases with altitude, and electrical effects are coupled with a passive magnetosphere along geomagnetic field lines. The large horizontal-scale potential differences at ionospheric heights map downward into the lower atmosphere where the perturbations in the ground electric field are superimposed on the diurnal variation. Finally, changes in the upper atmospheric conductivity due to solar flares, polar cap absorptions, and Forbush decreases are shown to alter the downward mapping of the high-latitude potential pattern and the global distribution of fields and currents.

Roble, R. G.↗
NASA NTRS1979

Chorus, energetic electrons and magnetospheric substorms

The paper investigates possible chorus generation mechanisms by means of simultaneous OGO-5 measurements of chorus, energetic (79 + or - 23 keV) electron fluxes and pitch angle distributions, and ambient magnetic fields. Further, the solar wind data during high-latitude dayside chorus events are examined. It is reported that the highly eccentric orbit had an apogee of 24 earth radii and an inclination of 30 deg to the geographic equator.

Tsurutani, B. T.↗