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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

A probable 1970 hard X-ray outburst by 4U0041+32

Balloon observations of a hard X-ray burst in 1970 most likely associated with the highly variable high-latitude X-ray source 4U 0041+32 are reported. The observation of X-ray flux at a density of about 0.06 photons/sq cm per sec from a previously unknown source at r.a. O h 45 min, dec 33 + or - 3 deg was made by a scintillation telescope on February 4, 1970. The spectrum was found to be very hard between 25 and 300 keV, with radiation in the form of a well-collimated beam causing the excess counting rate over a period of 30 min. Further observations on September 25, 1970 indicated the object had faded to an intensity below 0.01 photons/sq cm per sec. The power law spectrum obtained during the February burst is observed to differ from those of other hard transients and hard compact binary X-ray sources by the fact that it extends to 300 keV, its apparent lack of pulsation and its not being associated with an early-type giant or supergiant companion.

Laros, J. G.↗
NASA NTRS1980

The oxygen polar corona

At high-latitude regions, energetic oxygen atoms are produced by a nonthermal mechanism associated with precipitated energetic atomic oxygen ions during disturbed periods. The upward moving nonthermal atoms can redistribute themselves at higher altitudes. For the storm of December 17, 1971, assuming the energetic O(+) ions are uniformly precipitated between 50 deg and 70 deg magnetic latitudes, the nonthermal oxygen atoms become dominant over the ambient at about 700 km on the dayside and at about 600 km on the nightside at 60 deg magnetic latitude. Globally, a high-number-density atomic oxygen corona appears between 50 deg and 70 deg magnetic latitudes above the exobase, and the maximum is located at a few degrees poleward from the center of the band (63 deg magnetic latitude).

Yee, J. H.↗
NASA NTRS1980

Field-aligned currents and large scale magnetospheric electric fields

D'Angelo's model of polar cap electric fields (1977) was used to visualize how high-latitude field-aligned currents are driven by the solar wind generator. The region 1 and region 2 currents of Iijima and Potemra (1976) and the cusp field-aligned currents of Wilhjelm et al. (1978) and McDiarmid et al. (1978) are apparently driven by different generators, although in both cases the solar wind is their ultimate source.

Dangelo, N.↗
NASA NTRS1980

The behavior of ozone near the stratopause from two years of BUC observations

Two years of Nimbus 4 backscattered ultraviolet data have been recalibrated and reprocessed. A Laplace transform inversion was applied to radiances at 2876 A and below for 560,000 individual scans for the period April 1970-May 1972. The behavior of ozone near 50 km as a function of time, latitude, and longitude is presented. The high-latitude 1-mbar ozone mixing ratio is maximum at the winter solstice, about 10 microgram/g and is minimum at the summer solstice, about 4 microgram/g. Below 30 deg latitude the ozone is fairly constant at 4 microgram/g. Ozone variability is large in winter and spring and small in summer and fall.

Mcpeters, R. D.↗
NASA NTRS1980

Discovery of low-redshift X-ray selected quasars - New clues to the QSO phenomenon

The identification of six X-ray sources discovered by the Einstein Observatory with X-ray quasars is reported, and the properties of these X-ray selected quasars are discussed. The four high-latitude fields of 1 sq deg each in which the Einstein imaging proportional counter detected serendipitous X-ray sources at intermediate exposures of 10,000 sec were observed by 4-m and 1.5-m telescopes, and optical sources with uv excesses and emission line spectra typical of many low-redshift quasars and Seyfert 1 galaxies were found within the 1-arcsec error boxes of the X-ray sources. All six quasars identified were found to be radio quiet, with low redshift and relatively faint optical magnitudes, and to be similar in space density, colors and magnitude versus redshift relation to an optically selected sample at the same mean magnitude. X-ray luminosity was found to be well correlated with both continuum and broad-line emission luminosities for the known radio-quiet quasars and Seyfert 1 galaxies, and it was observed that the five objects with the lowest redshifts have very similar X-ray/optical luminosity ratios despite tenfold variations in X-ray luminosity. It is concluded that photoionization by a continuum extending to X-ray energies is the dominant excitation mechanism in radio-quiet quasars.

Grindlay, J. E.↗
NASA NTRS1980

Observations of diffuse galactic gamma rays

Observations of 35 MeV to several GeV diffuse gamma radiation from the galaxy are available from the SAS-2 and COS-B instruments. This paper gives a brief review of the experimental problem, a discussion of the high-latitude (local) galactic component, and a study of the more distant low-latitude emission from the galactic plane. Finally, the emerging observations in other energy ranges are mentioned.

Simpson, G. A.↗
NASA NTRS1980

Mars atmosphere pressure periodicities from Viking observations

The first Martian year of pressure data taken by the Viking landers on Mars is subjected to power spectrum analysis. The analysis suggests that strong periodicities are present in the Martian atmosphere, especially at the high-latitude (48 deg N) site of the second lander. Most of these periodicities are probably due to the passage of baroclinic waves. Inspection of individual segments of data shows that the periodicities of the dominant waves vary significantly with time of year. This may be related to the amount of dust in the atmosphere since the dominant frequencies of the waves during times of major dust storms are quite different than at other times.

Sharman, R. D.↗
NASA NTRS1981

Electron temperature anisotropy in the polar wind

The steady state flow of a fully ionized H(+)-O(+)-electron plasma along geomagnetic field lines in the high-latitude topside ionosphere is investigated theoretically, with emphasis on the electron temperature anisotropy and heat flow in the polar wind. The 13-moment system of transport equations developed by Schunk (1975, 1977), which contains a continuity, momentum, internal energy, stress tensor and heat flow equation for each species, is employed to represent the electrons, with a simplified set of transport equations used for the ions, and the transport equations are solved at altitudes from 1500 to 12,000 km for both subsonic and supersonic H(+) outflows. For subsonic H(+) outflows, the electron gas is found to remain collision dominated to high altitudes. For supersonic H(+) outflows, the electron gas is also found to be collision dominated at altitudes below 2500 km, with an anisotropy in electron temperature distribution developing such that the temperature of the perpendicular electrons is greater than that of the parallel electrons at higher altitudes. In addition, the magnitude of downward electron heat flux at 1500 km is shown to have a dramatic effect on the individual parallel and perpendicular electron temperatures.

Schunk, R. W.↗
NASA NTRS1981

A statistical study on characteristics of high latitude Pi 3 pulsations

The latitude and magnetic local time distributions of Pi 3 pulsations relative to polarization and the position of maximum intensity are presented using data from the high-latitude North American International Magnetospheric Study magnetometer network. These distributions are compared with those of Pc 5 and Pi 2 pulsations. The locus of Pi 3 maximum amplitude and the corresponding curve for Pc 5 are similar in general shape, but the former is located at considerably lower geomagnetic latitudes than the latter. For Pi 2 pulsations, the latitude of maximum amplitude is found to agree well with the auroral oval, whereas the locus of Pi 3 amplitude maximum deviates from the auroral oval appreciably in the dawn and dusk regions and is near the poleward border of the auroral oval in the premidnight region where the equatorward boundary of the oval is lowest in latitude. It is concluded that dayside Pi 3 pulsations may have a different generation mechanism from that for nightside Pi 3 events.

Suzuki, A.↗
NASA NTRS1981

Anomalous heating of the polar E region by unstable plasma waves. II - Theory

It is found that anomalous electron temperatures in the disturbed high-latitude E region can be quantitatively explained in terms of heating by unstable plasma waves. The electron temperatures at 110 km have been measured to be as high as 1500 K instead of the expected value of about 300 K. It is shown that by using quasi-linear theory there is an ample source of heat in the unstable waves and that the measured electron temperature profiles have a shape very similar to what is expected from plasma wave heating by the modified two-stream instability. It is found that there is even more heating going to the ion gas, but that the resulting effect on the ion temperature may be difficult to measure. The best estimate of the wave heating rates leads to the conclusion that wave heating can be as much as 50% of the Joule heating for dc electric field strengths of the order of 45 mV/m or greater.

St.-Maurice, J. P.↗
NASA NTRS1981

Measurement of stratospheric sulfur constituents

New measurements of mixing ratios of OCS in the lower stratosphere at midlatitude (Northern California) and high-latitude (Alaska) locations are reported which are in essential agreement with previous results. Weak signals due to stratospheric SO2 have been detected, and the estimated mixing ratios ranged from 36 to 51 pptv at altitudes 15.2 to 20.3 km. A very weak signal observed in the analysis is thought to be due to CS2 and, if this identification is correct, an upper limit concentration is estimated to be 1 pptv.

Inn, E. C. Y.↗
NASA NTRS1981

A meteor-ablation model of the sodium and potassium layers

Recent results on meteor ablation are used as input to a model in which ablation (or evaporation) is the source and deposition on dust particles is the sink. The dust comes from recondensation of the rest of the meteor vapor. An excellent match is found to the observed characteristics of the sodium layer. It is argued that the high-latitude winter maximum of abundance (and layer height) is due to the much lower rate of ionization there and over the polar cap. The computations show the required factor of 4-5 and also match the height variation. To keep the ion density from being too large, downward electrodynamic transport at about 50 cm/sec must be invoked. The different behavior and low abundance of potassium require an additional sink. The one proposed is Penning ionization by metastable excited O2. Inherent in the model is that sodium and its compounds reside almost entirely on dust particles below 80 km. Large abundances in the free form at stratospheric heights are very unlikely and are not a good explanation of observed ambient ions.

Hunten, D. M.↗
NASA NTRS1981

A magnetospheric signature of some F layer positive storms

Calculations of electron density distributions in the global thermosphere-ionosphere system perturbed by high-latitude thermospheric heating are presented which indicate a link between the heating and magnetospheric plasma disturbances near the equator. The calculations were made using a self-consistent model of the global sunlit thermosphere-ionosphere system describing the evolution of equatorial plasma disturbances. The heat input is found to cause electron density enhancements that propagate along magnetic field lines from the F2 maximum over mid-latitudes to the equator in the magnetosphere and which correspond to the positive phase of an F layer storm. The positive phase is shown to be generated by the induction of equatorward winds that raise the mid-latitude F layer through momentum transfer from neutral atoms to ionospheric ions, which ions pull electrons with them. Model results are used to identify plasma signatures of equatorward winds and an intensified magnetospheric electric field in Explorer 45 and Arial 4 measurements taken during the positive phase of an F layer storm.

Miller, N. J.↗
NASA NTRS1981

Particle and Joule heating of the neutral polar thermosphere in cusp region using atmosphere Explorer-C satellite measurements

It is pointed out that thermospheric heating in the auroral zone and polar cap is of great importance to the variations in the high-latitude neutral wind and the resulting global temperature and densities. The considered investigation is concerned with relating in a quantitative manner the energy inputs from the Joule heating and particle inputs with the thermospheric responses, taking into account the cusp region, and the region of the eastward auroral electrojet. The data used in the investigation were obtained by the Atmosphere Explorer C satellite in late December 1974. Attention is given to electric fields derived from ion drift measurements, electric field strength and particle energy flux measured by the low energy electron experiment for AE-C orbit 4708, electron density contours, Joule heating contours, and height integrated Joule heating and particle energy flux.

Griffis, M.↗
NASA NTRS1981

A laboratory experiment on EM backscatter from Farley-Buneman and gradient drift waves

Results of laboratory experiment on Bragg backscatter of 3-cm microwaves by turbulent waves driven by the Farley-Buneman and gradient drift instabilities are reported. It is noted that the study is the third in a series of laboratory experiments performed to test, under controlled conditions, prevalent ideas on EM scattering by equatorial and high-latitude ionospheric waves and irregularities. It is shown through separate backscattering from fast and slow ion beam modes that a beam of EM radiation actually provides, in backscatter, information on the spectral content of the scattering medium.

Alport, M. J.↗
NASA NTRS1981

A simple model of the Lagrangian-mean flow produced by dissipating planetary waves

A simple equation for the Lagrangian-mean flow induced by damped planetary waves is derived. The flow computed for stationary planetary waves of a beta-plane is found to be generally poleward and downward during winter and appears to be about twice as strong as the diabatic circulation in the lower stratosphere. An important factor in determining the high-latitude Lagrangian-mean flow field is the subtropical jet stream which blocks planetary wave propagation toward the equatorial regions. Computations using two types of Lagrangian-mean boundary conditions at the surface show that incorrect orographic forcing distorts the Lagrangian-mean flow up to three scale heights or more above ground.

Schoeberl, M. R.↗
NASA NTRS1981

Wind induced composition effects at high latitudes

The temperature and compositional structure of the upper atmosphere are discussed in relation to the impacts of wind-induced diffusion processes. Seasonal variations in thermospheric temperature and composition are explained by energy and mass transport from the summer to the winter hemisphere induced by preferential heating, with the winter oxygen bulge participating in a feedback mechanism which acts to dampen wind velocities and increase temperature contrast. Changes in the eddy diffusion coefficient are considered as a complementary mechanism of producing the seasonal anomalies. The role of winds induced by high-latitude heating by particles and Joule dissipation during magnetic storms and substorms in accounting for thermospheric density increases and N2 and Ar enhancements and O and He depletions at high latitudes are discussed, and the rather weak compositional signature of E x B momentum coupling is distinguished from the effects of Joule dissipation.

Mayr, H. G.↗
NASA NTRS1981

Electric fields and electrostatic potentials in the high latitude ionosphere

Recent interpretive studies of electric field-driven ionospheric plasma convection data from the AE-C satellite are described, where the instruments employed include an ion drift meter and an ion-retarding potential analyzer. Electrostatic potential curves are derived from ion drift velocity measurements for high-latitude segments of the satellite's orbit. The potential curves are shown to be useful in determining the character of the global electrostatic potential pattern, with emphasis on the separation of convective cells. Results are given for six orbits, with attention to the mid-day auroral region.

Banks, P. M.↗