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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 541 records · Page 30

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NASA NTRS1977

Time delay occultation data of the Helios spacecrafts and preliminary analysis for probing the solar corona

S-band time delay measurements were collected from the spacecrafts Helios A and B during three solar occultations in 1975/76 within heliocentric distances of about 3 and 215 solar radii in terms of range, Doppler frequency shift, and electron content. A description is given concerning some characteristic features of the methods of measurement and data processing. Typical data sets are discussed to probe the electron density distribution near the sun (west and east limb as well) including the outer and extended corona. Steady-state and dynamical aspects of the solar corona are presented and compared with earth-bound K-coronagraph measurements. Using a weighted least squares estimation 3 parameters of an average coronal electron density profile are derived in a preliminary analysis to yield electron densities of about 130 billion; 100 million; 7 million/cu m at r?3; 65; 215 solar radii. Transient phenomena are discussed and a velocity of propagation v approximately 900 km/s for plasma ejecta from a solar flare is determined from an extraordinary set of Helios B electron content measurements on April 30/May 1, 1976.

Edenhofer, P.↗

NASA NTRS1987

The auroral kilometric radiation from Uranus and its magnetospheric implications

The Gulkis and Carr (1987) emission beam model for the kilometric radio emission from Uranus and types of information regarding the Uranian inner magnetosphere that may be derivable from its application are discussed. A modeled electron density profile is presented. The manner in which the hollow-cone beam from each element of the distributed auroral-zone source varies with frequency is determined. It is suggested that the observed effects might be due to refraction by a smooth component of the electron density variation with distance, together with multiple small refractions by electron density inhomogeneities along the ray path.

Carr, Thomas D.↗

NASA NTRS1974

Measurement of plasma temperature and density using radiation absorption

A light beam of predetermined wavelength, preferably monochromatic, is directed through a plasma to be measured. The absorption of the light by the plasma is detected for deriving an absorption coefficient of the plasma. Knowing the absorption coefficient of the plasma and independently measuring either the electron density or temperature of the plasma allows solution of an equation to derive the other unknown quantity, i.e. either electron density or temperature. In a preferred method, the absorption coefficient of the plasma is derived simultaneously for two probing light beams of substantially different predetermined wave-lengths. Knowing these two coefficients allows solution of two simultaneous equations to derive the electron density and temperature of the plasma.

Kenneth W Billman↗

NASA NTRS1977

Determination of the N2 recombination rate coefficient in the ionosphere

Measurements of aeronomic parameters made by the Atmosphere Explorer-C satellite are used to determine the recombination rate coefficient of N2(+) in the ionosphere. The rate is found to increase significantly with decreasing electron density. Values obtained range from approximately 1.4 x 10 to the -7th to 3.8 x 10 to the -7th cu cm/sec. This variation is explained in a preliminary way in terms of an increase in the rate coefficient with vibrational excitation. Thus, high electron densities depopulate high vibrational levels reducing the effective recombination rate, whereas, low electron densities result in an enhancement in the population of high vibrational levels, thus, increasing the effective recombination rate.

Orsini, N.↗

NASA NTRS2012

Global Characteristics of the Correlation and Time Lag Between Solar and Ionospheric Parameters in the 27-day Period

The 27-day variations of topside ionosphere are investigated using the in-situ electron density measurements from the CHAMP planar Langmuir probe and GRACE K-band ranging system. As the two satellite systems orbit at the altitudes of approx. 370 km and approx. 480 km, respectively, the satellite data sets are greatly valuable for examining the electron density variations in the vicinity of F2-peak. In a 27-day period, the electron density measurements from the satellites are in good agreements with the solar flux, except during the solar minimum period. The time delays are mostly 1-2 day and represent the hemispherical asymmetry. The globally-estimated spatial patterns of the correlation between solar flux and in-situ satellite measurements show poor correlations in the (magnetic) equatorial region, which are not found from the ground measurements of vertically-integrated electron content. We suggest that the most plausible cause for the poor correlation is the vertical movement of ionization due to atmospheric dynamic processes that is not controlled by the solar extreme ultraviolet radiation.

Global Characteristics↗

NASA NTRS1997

Polar coronal hole density and its solar wind consequences using LASCO observations

The electron density of the north polar coronal hole was determined using the Mark 3 coronameter and large angle spectrometric coronagraph (LASCO) C2 and C3 observations from 1.2 and 8.0 solar radii. The electron density results were compared to the analysis of the Spartan 201-03 data. The implications on solar wind modeling are discussed. The Solar and Heliospheric Observatory (SOHO) investigations confirm those from Spartan 201-03: the high speed solar wind from the polar coronal holes seem to be accelerated much closer to the sun than it was supposed to be. The velocity of polar solar wind agrees with the data from Ulysses observations.

Guhathakurta, M.↗

NASA NTRS1995

Morphology of solar wind fluctuations and structure in the vicinity of the Sun from radio propagation measurements

Radio propagation measurements represent a powerful means for remote probing of electron density and solar wind speed in the acceleration region of the solar wind not yet explored by in situ measurements. Recent investigations based on radio propagation measurements have led to considerable progress in our knowledge of the general morphology of solar wind fluctuations and structure, especially in terms of their relationship to solar wind properties that have been observed directly by fields and particles measurements, and to coronal features observed in white-light measurements. The purpose of this paper is to present an overview of the latest results on quasi-stationary structure covering the large scale variation of solar wind speed over the streamer belt and coronal hole regions, coronal streamers (source of slow solar wind) and their associated small-scale electron density structure, plumes, density and fractional or relative density fluctuations, and the spectral characteristics of the electron density fluctuations. The radio propagation measurements not only reveal new information on the structure near the Sun, but also show that the structure appears to undergo substantial evolution on its way to 0.3 AU, the closest radial distance for which direct in situ spacecraft measurements are available.

Woo, R.↗

NASA NTRS1986

Millisecond radio spikes from the dwarf M flare star AD Leonis

Arecibo radio observations of millisec bursts of radio signals at 1415 MHz from AD Leonis are reported. The observed burst had an ellipticity of 0.95, 50-100 percent circular polarization, and a flux density maximum of 30 mJy. The 50 sec burst featured five quasi-periodic oscillations with a mean periodicity of about 3.2 sec. A second, less intense burst that occurred 20 sec later was 100 percent circularly polarized. The area emitting the bursts covered an estimated 0.005 of the radius of AD Leonis and had an electron density of 6 billion/cu cm and a longitudinal magnetic field strength of 250 gauss, if the source was an electron-cyclotron maser. A coherent plasma source would require, for the first harmonic, an electron density of 20 billion/cu cm and a magnetic field much less than 500 gauss. A second harmonic of the plasma frequency would require an electron density of 6 billion/cu cm and a field strength much less than 250 gauss. The possibility that the source was periodic oscillations in coronal loops is discussed.

Lang, K. R.↗

NASA NTRS1966

Density measurements with electron beams.

Electron beam density measurements, discussing effect of elevated rotational and vibrational temperatures

DENSITY MEASUREMENT↗

NASA NTRS1962

THE VLF ADMITTANCE OF A DIPOLE IN THE LOWER IONOSPHERE

The admittance of a dipole in the lower ionosphere has been calculated for very low frequencies. Both the real and reactive parts of the admittance are found to be related to the ion sheath which forms about the dipole and are functions of electron density and temperature of the ionosphere. An electron density profile is estimated based upon measurements reported in an earlier rocket flight.

DIPOLE↗

NASA NTRS1962

THE V. L. F. ADMITTANCE OF A DIPOLE IN THE LOWER IONOSPHERE

DIPOLE↗

NASA NTRS1972

Solar wind maintenance of the nighttime Venus ionosphere

An attempt is made to establish an ionization source capable of maintaining the nighttime Venus ionosphere. The corpuscular ionization and heating caused by the penetration of solar wind plasma into the nightside ionosphere was suggested as a possible source. Theoretical tests, using an interacting solar wind model, were made of the electron density and the results compared with observed electron density profiles. Results indicate the solar wind could maintain the nighttime ionosphere of Venus.

Hartle, R. E.↗

NASA NTRS2001

Detection of Chamber Conditioning by CF4 in the GEC Cell

During oxide etch processes, buildup of fluorocarbon residues on reactor sidewalks can cause to drift and will necessitate time for conditioning and cleaning of the reactor. Various measurements in CF4 and Ar plasmas are made in an attempt to identify a metric able to indicate the chamber condition. Mass spectrometry and a Langmuir probe shows that the buildup of fluorocarbon films on the reactor surface causes a decrease in plasma floating potential, plasma potential, and ion energy in argon plasmas. This change in floating potential is also observed in CF4 plasma operation, and occurs primarily during the first hour and a half of plasma operation. A slight rise in electron density is also observed in the argon plasmas. Because the change is seen in an argon plasma, it is indicative of altered physical, not chemical, plasma-surface interactions. Specifically, the insulating films deposited on metal surfaces alter the electromagnetic fields seen by the plasma, affecting various parameters including the floating potential and electron density. An impedance probe placed on the inductive coil shows a slight reduction in plasma impedance due to this rising electron density. The optical emission of several species, including CF, C2, atomic Si and atomic C, is also monitored for changes in density resulting from the buildup of film on the chamber wall. Changes in the optical emission spectrum are comparable to the noise levels in their measurement.

Cruden, Brett A.↗

NASA NTRS1976

Coincident observations of ionospheric troughs and the equatorial plasmapause

Electron-density observations made in the topside ionosphere by the Ariel 4 and Isis 2 satellites are examined in conjunction with results obtained by Explorer 45 when it traversed the near-equatorial plasmapause with one hour (both UT and MLT) of the Ariel and Isis traversals of the same L coordinate. Both dusk and night observations are analyzed, and an attempt is made to show that depressions in ionospheric electron density occur in the vicinity of the plasmapause field line. It is concluded that the electron distributions observed in the electron-density troughs at 550 km near dusk by Ariel and at 1400 km near midnight by Isis do not always parallel variations in the light-ion distribution inferred from the Explorer plasmapause traversals and that there appears to be no specific feature of the main ionospheric trough which can be used to identify the plasmapause field line except in a statistical sense.

Grebowsky, J. M.↗

NASA NTRS1990

A test of convection models for IMF Bz north

The Utah State University Ionospheric Model was run to obtain diurnally reproducible ionospheric densities and temperatures for summer and winter conditions using both distorted two-cell and three-cell convection patterns. Differences due to the different convection patterns manifest themselves in the depth and location of polar holes in the F-region electron density. While the total depth of the model holes is a characteristic of the diurnally reproducible pattern, the features appear and are recognizable within 0.5 h. Langmuir probe data from 41 DE-2 passes, during which the IMF Bz component was northward, have been qualitatively checked against the model predictions. The cross polar cap electron density profiles of a large majority of the passes more closely conform to the distorted two-cell runs for both polarities of the IMF By component. This test can be generalized to rule out proposed convection patterns based on the presence/absence and position of polar electron density holes.

Maynard, N. C.↗

NASA NTRS1989

The ionosphere of Neptune

Limited knowledge of ionospheric processes of the outer planets and practically no information on the upper atmosphere of Neptune result in a range of possible ionospheres for Neptune. Various cases are investigated in order to establish a theoretical framework of the ionospheric structure against which the radio occultation measurements can be evaluated. The peak electron densities could range from 1000/cu cm to 10 to the 6th/cu cm depending on ion loss processes and particle ionization processes. The scale height could also range from 300 km to 2000 km depending on the exospheric temperature. Although various assumptions must be made, it is predicted that an auroral ionosphere with large electron densities and a large scale height will be observed by the ingress radio occultation measurement, and that a compressed ionosphere with small electron densities will be seen during the egress measurement.

Shinagawa, H.↗

NASA NTRS1980

Spatial distribution of plasma in the Io torus

In situ measurements of ion densities and temperatures have been analyzed to produce profiles of these plasma parameters along the Voyager 1 inbound trajectory between 7 and 5 Jupiter radii. The temperature profile shows a sharp decrease by a factor of 50 between 5.8 and 5.2 Jupiter radii corresponding to a temperature gradient of 7 x 10 to the 5th per Jupiter radius. The electron density profile, inferred from the ion density measurements, has two maxima at 5.7 and 5.3 Jupiter radii. A two-dimensional model of the spatial distribution of various ionic species in the Io plasma torus has been constructed. Using this model a contour map of electron density in a meridional plane has been made, it exhibits a well-defined inner edge to the torus at 5.6 Jupiter radii. The contour map of S(+) ion density indicates that most of the S(+) ions are concentrated close to the centrifugal symmetry surface and radially inward of the larger electron density maximum near 5.7 Jupiter radii.

Bagenal, F.↗

NASA NTRS1983

Short wavelength laser calculations for electron pumping in neon-like krypton (Kr XXVII)

Calculations of electron impact collision strengths and spontaneous radiative decay rates are made for neon-like krypton (Kr XXVII) for the 2s2 2p6, 2s2 2p5 3s, 2s2 2p5 3p, and 2s2 2p5 3d configurations. From these atomic data, the level populations as a function of the electron density are calculated at two temperatures, 1 x 10 to the 7th K and 3 x 10 to the 7th K. An analysis of level populations reveals that a volume of krypton in which a significant number of the ions are in the Kr XXVII degree of ionization can produce a significant gain in transition between the 2s2 2p5 3s and 2s2 2p5 3p configurations. At an electron density of 1 x 10 to the 19th/cu cm the plasma length has to be of the order of 1 m; at a density of 1 x 10 to the 21st/cu cm the length is reduced to approximately 0.5 cm; and at an electron density of 1 x 10 to the 22nd/cu cm the length of the plasma is further reduced to approximately 1 mm.

Feldman, U.↗