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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Line formation in the solar chromosphere. II - An optically thick region of the chromosphere-corona transition region observed with OSO 8

The University of Colorado ultraviolet spectrometer aboard the Orbiting Solar Observatory 8(OSO 8) has measured self-reversed profiles of the resonance line of C IV lamda 1548.2 at the limb passage of an active region. The degree of the self-reversal together with the absolute intensity of the line profile determine the electron density in the active region at 10 to the 10th/cu cm at temperatures where the C IV line is formed. The nonthermal component of the broadening velocity is no more than 14km/s, and the physical thickness of an equivalent plane-parallel slab in hydrostatic equilibrium that would give rise to the observed line profiles is about 430 km.

Lites, B. W.↗
NASA NTRS1987

Transverse diffusion of electrons in a magnetoplasma

Plasma density and temperature profiles were measured for plasma electrons which were generated by a plasma source and ionization from a 1 kev electron beam. Electron plasma parameters were measured with a cylindrical Langmuir probe which was moved perpendicular to the axis of the beam and field. Electron densities decreased exponentially from the beam center and the decay constant varied with magnetic field in accordance with the Bohm theory of cross field diffusion. This enhanced diffusion effect due to instabilities generated by the electron beam is orders of magnitude larger than that due to particle collisions.

Mcintyre, Bernard↗
NASA NTRS1995

One-Dimensional Hybrid Satellite Track Model for the Dynamics Explorer 2 (DE 2) Satellite

A one-dimensional hybrid satellite track model has been developed to calculate the high-latitude thermospheric/ionospheric structure below the satellite altitude using Dynamics Explorer 2 (DE 2) satellite measurements and theory. This model is based on Emery et al. satellite track code but also includes elements of Roble et al. global mean thermosphere/ionosphere model. A number of parameterizations and data handling techniques are used to input satellite data from several DE 2 instruments into this model. Profiles of neutral atmospheric densities are determined from the MSIS-90 model and measured neutral temperatures. Measured electron precipitation spectra are used in an auroral model to calculate particle impact ionization rates below the satellite. These rates are combined with a solar ionization rate profile and used to solve the O(+) diffusion equation, with the measured electron density as an upper boundary condition. The calculated O(+) density distribution, as well as the ionization profiles, are then used in a photochemical equilibrium model to calculate the electron and molecular ion densities. The electron temperature is also calculated by solving the electron energy equation with an upper boundary condition determined by the DE 2 measurement. The model enables calculations of altitude profiles of conductivity and Joule beating rate along and below the satellite track. In a first application of the new model, a study is made of thermospheric and ionospheric structure below the DE 2 satellite for a single orbit which occurred on October 25, 1981. The field-aligned Poynting flux, which is independently obtained for this orbit, is compared with the model predictions of the height-integrated energy conversion rate. Good quantitative agreement between these two estimates has been reached. In addition, measurements taken at the incoherent scatter radar site at Chatanika (65.1 deg N, 147.4 deg W) during a DE 2 overflight are compared with the model calculations. A good agreement was found in lower thermospheric conductivities and Joule heating rate.

Deng, Wei↗
NASA NTRS1978

Effects of applied dc radial electric fields on particle transport in a bumpy torus plasma

The influence of applied dc radial electric fields on particle transport in a bumpy torus plasma is studied. The plasma, magnetic field, and ion heating mechanism are operated in steady state. Ion kinetic temperature is more than a factor of ten higher than electron temperature. The electric fields raise the ions to energies on the order of kilovolts and then point radially inward or outward. Plasma number density profiles are flat or triangular across the plasma diameter. It is suggested that the radial transport processes are nondiffusional and dominated by strong radial electric fields. These characteristics are caused by the absence of a second derivative in the density profile and the flat electron temperature profiles. If the electric field acting on the minor radius of the toroidal plasma points inward, plasma number density and confinement time are increased.

Roth, J. R.↗
NASA NTRS1965

A microwave probe for plasma plumes.

Swinging-arm microwave probe to measure electron density and collision frequency profiles transverse to plasma jet plumes

MICROWAVE PLASMA PROBE↗
NASA NTRS1973

Tracking Data Relay Satellite System (TDRSS) VHF propagation study

A study performed to investigate the use of the Bent Ionospheric Model in computing corrections to the range and range rate measurements of the TDRSS satellites is documented. Several orbital configurations between the two satellites are discussed as to their effects on total electron content along the radio path between the satellites. Problem areas in the accurate computation of total electron content and range rate corrections are also discussed. The Bent Ionospheric Model gives the electron density versus height profile as a function of latitude, longitude, height, time, season, and solar flux.

Schleicher, L. A. H.↗
NASA NTRS1976

Post sunset behavior of the 6300 A atomic oxygen airglow emission

A theoretical model of the 6300 A OI airglow emission was developed based on the assumptions that both the charged and neutral portions of the Earth's upper atmosphere are in steady state conditions of diffusive equilibrium. Intensities of 6300 A OI emission line were calculated using electron density true height profiles from a standard C-4 ionosonde and exospheric temperatures derived from Fabry-Perot interferometer measurements of the Doppler broadened 6300 A emission line shape as inputs to the model. Reaction rate coefficient values, production mechanism efficiencies, solar radiation fluxes, absorption cross sections, and models of the neutral atmosphere were varied parametrically to establish a set of acceptable inputs which will consistently predict 6300 A emission intensities that closely agree with intensities observed during the post-sunset twilight period by an airglow observatory consisting of a Fabry-Perot interferometer and a turret photometer. Emission intensities that can only result from the dissociative recombination of molecular oxygen ions were observed during the latter portion of the observational period. Theoretical calculations indicate that contamination of the 6300 A OI emission should be on the order of or less than 3 percent; however, these results are very sensitive to the wavelengths of the individual lines and their intensities relative to the 6300 A OI intensity. This combination of a model atmosphere, production mechanism efficiencies, and quenching coefficient values was used when the dissociative photoexcitation and direct impact excitation processes were contributing to the intensity to establish best estimates of solar radiation fluxes in the Schumann--Runge continuum and associated absorption cross sections. Results show that the Jacchia 1971 model of the upper atmosphere combined with the Ackerman recommended solar radiation fluxes and associated absorption cross sections produces theoretically calculated intensities that more closely agree with the observed intensities than all the other combinations.

Smith, R. E.↗
NASA NTRS1979

Description and charging results from the RSPM

Representative satellite materials, to be flown on STP-78-2 in 1979 on the SSPM instruments, were included as part of the AFGL Rocket payload flown from White Sands Missile Range on January 21, 1978. Potentials as high as + 1100 volts on the conductor and + or - 400 volts on the insulator were recorded by the RSPM near the minimum in the electron density vs altitude profile. In addition to the charging potentials measured during ion gun operation, sample charging currents also were recorded with time resolutions near 30 milliseconds. These results demonstrate the validity of the experiment concept of the SSPM on SCATHA.

Mizera, P. F.↗
NASA NTRS1979

Characteristics of trough region auroral patches and detached arcs observed by Isis 2

All of the data presented in this paper were obtained from the Isis 2 satellite, which was launched into a 1400-km near-circular polar orbit in April 1971. Instruments used in this study include the topside sounder for providing vertical profiles of the electron density, the Langmuir probe for measuring electron temperature and concentration, and the auroral scanning photometer for detecting optical emissions at 5577 A and 3914 A. Two distinct types of auroras (east-west-aligned oval-shaped 'patches', and isolated east-west 'detached arcs') are observed in the trough region (almost exclusively in the Northern Hemisphere) equatorward of the diffuse auroral boundary. Attention is given to comparison of patches and detached arcs, relation to magnetic indices, and relation to detached plasma and ELF hiss.

Moshupi, M. C.↗
NASA NTRS1979

Plasma property and performance prediction for mercury ion thrusters

The discharge chambers of mercury ion thrusters are modelled so the principal effects and processes which govern discharge plasma properties and thruster performance are described. The conservation relations for mass, charge and energy when applied to the Maxwellian electron population in the ion production region yield equations which may be made one-dimensional by the proper choice of coordinates. Solutions to these equations with the appropriate boundary conditions give electron density and temperature profiles which agree reasonably well with measurements. It is then possible to estimate plasma properties from thruster design data and those operating parameters which are directly controllable. By varying the operating parameter inputs to the computer code written to solve these equations, perfromance curves are obtained which agree quite well with measurements.

Longhurst, G. R.↗
NASA NTRS1980

F region airglow - Are ground-based observations consistent with recent satellite results

The Atmosphere Explorer photochemistry is used to interpret simultaneous observations made at the Arecibo Observatory of the OI (6300 A) and NI (5200 A) airglow surface brightness and electron density and temperature profiles measured by incoherent scatter radar. It was found that the theory and the experiment agree for the 5200-A emission; however, it was not possible to obtain to a complete agreement for the 6300-A nightglow. It is suggested that the source of the discrepancy results from one of the parameters used to calculate the production rate of O(lD); the data show evidence of an asymmetrical behavior of the ionosphere between times when the F layer is descending and when it is ascending, with asymmetry probably reflecting the effects of transport on molecular ion densities in the bottom side of the F region.

Cogger, L. L.↗
NASA NTRS1986

Neutral oxygen and sulfur densities in the Io torus

Ultraviolet spectra (1150-1750 A) of the Io torus, obtained using a rocket-borne telescope and spectrometer in May 1981, show emissions of neutral sulfur and neutral oxygen, as well as ionic emissions of S II, S III, and S IV. The emissions are observed almost 180 deg from the location of the satellite Io and imply the existence of an extended neutral atomic cloud associated with the torus. In the present work, neutral densities and ion mixing ratios are derived by modeling the observations using torus electron temperature and density profiles proportional to those at the time of the Voyager 1 encounter. The model includes the effects of photoexcitation, which can be considerable if the neutral cloud is large enough. At the time of the observation, substantial densities of neutral oxygen and neutral sulfur are found in regions of the torus far from Io. These lower limits on the neutral densities are compared to theoretical models of the neutral source, and the ion mixing ratios are compared to IUE observations of the torus obtained over a period of 5 yr. Arguments that tend to rule out Europa as the source of the neutral emission are also presented.

Skinner, T. E.↗
NASA NTRS1987

Energetic ion and electron phase space densities in the magnetosphere of Uranus

Proton and electron phase space density profiles are constructed from an analysis of Voyager 2 low-energy charged particle data from the magnetosphere of Uranus. The Uranus proton profiles reveal an approximately exponential decline with decreasing radius for L less than about 9 in a relatively dense thermal plasma region with intense plasma wave activity. Among the distributed loss mechanisms at Uranus are satellite sweeping, wave-particle interactions, and charge exchange of protons with an extended hydrogen corona.

Cheng, Andrew F.↗
NASA NTRS1991

High-precision timing of millisecond pulsars. II - Astrometry, orbital evolution, and eclipses of PSR 1957 + 20

Pulse time-of-arrival measurements have been acquired for PSR 1957 + 20 on 61 days over a 2.7 yr interval, including the times of 44 eclipse disappearance or reappearance events. The timing data provide a reliable measurement of the pulsar's proper motion, 29 +/- 3 mas/yr, at position angle 216 +/- 6 deg; this direction is in excellent agreement with that suggested by the cometlike shape of a surrounding optical emission nebula. The rate of change of the orbital period has been measured: a surprisingly large (-3.9 +/- 0.9) x 10 exp -11, implying that significant orbital evolution must take place on a time scale of 30 Myr. Finally, the present observations extend the eclipse measurements to higher frequencies and provide better statistics for these highly variable phenomena. The eclipse data are used to compute a column-density profile of free electrons in the outer parts of the eclipsing region, and thereby provide an important glimpse into the material being ablated from the companion star.

Ryba, M. F.↗