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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Soft X-ray spectrum of a hot plasma

The spectrum of radiation emitted by a hot optically thin plasma with abundances and equilibrium ionization balance appropriate to interstellar conditions has been calculated. The results at wavelengths shorter than 200 A are discussed for material in the electron-temperature range from 160,000 to 100 million K.

Raymond, J. C.↗
NASA NTRS1996

NASA's Technical Handbook for Avoiding On-Orbit ESD Anomalies Due to Internal Charging Effects

This paper describes NASA-HDBK-4002, "Avoiding Problems Caused by Spacecraft On-Orbit Internal Charging Effects". The handbook includes a description of internal charging and why it is of concern to spacecraft designers. It also suggests how to determine when a project needs to consider internal spacecraft charging, it contains an electron penetration depth chart, rationale for a critical electron flux criterion, a worst-case geosynchronous electron plasma spectrum, general design guidelines, quantitative design guidelines, and a typical materials characteristics list. Appendices include a listing of some environment codes, electron transport codes, a discussion of geostationary electron plasma environments, a brief description of electron beam and other materials tests, and transient susceptibility tests. The handbook will be in the web page, hftp://standards.nasa.gov. A prior document, NASA TP2361 "Design Guidelines for Assessing and controlling Spacecraft Charging Effects", 1984, is in use to describe mitigation techniques for the effects of surface charging of satellites in space plasma environments. HDBK-4002 is meant to complement 2361 and together, the pair of documents describe both cause and mitigation designs for problems caused by energetic space plasmas.

Whittlesey, Albert↗
NASA NTRS2000

Emission Lines of O III in The Optical and Ultraviolet Spectra of Planetary Nebulae

Recent R-matrix calculations of electron impact excitation rates in 0 III are used to calculate electron temperature and density-dependent emission line ratios R (sub 1) = I(4363 Angstroms)/ I(4960 Angstroms + 5007 Angstroms), R (sub 2) = I(1661 Angstroms + 1667 Angstroms)/ I(4960 Angstroms + 5007 Angstroms) and R (sub 3)= I(2322 Angstroms)/ I(1661 Angstroms + 1667 Angstroms), for a range of electron temperatures (7500 less than or equal to Te less than or equal to 30 000 K) and densities (10 (exp 4) less than or equal to N (sub e) less than or equal to 10 (exp 7) per cubic centimeters) applicable to gaseous nebulae. The ratio-ratio diagrams (R (sub 1), R (sub 2)) and (R (sub 1), R (sub 3)) should, in principle, allow the simultaneous determination of T (sub e) and N (sub e) from measurements of the 0 III features in a spectrum. Plasma parameters derived for a sample of high-excitation planetary nebulae from (R (sub 1), R (sub 2)) and (R (sub 1), R (sub 3)) measurements, produced using a combination of ultraviolet spectra obtained with the International Ultraviolet Explorer (IUE) and optical data from a number of observing runs, are found to show excellent internal consistency. They also show, in general, good agreement with the values of Te and Ne estimated from other line ratios in the nebulae, therefore providing observational support for the accuracy of the theoretical ratios and hence the atomic data adopted in their derivation.

Crawford, F. L.↗
NASA NTRS1981

The Voyager 1 EUV spectrum of the Io plasma torus

The Voyager 1 EUV spectrum of the hot Io plasma torus obtained before encounter in 1979 at a range of 4,800,000 km is analyzed in terms of a collisional model with improved collision strengths. Model calculations are based entirely on steady-state equilibrium between electron excitation-deactivation and radiative decay in the subspecies structure, and plasma temperature and species number densities are derived by fitting model spectra to the observations. Lines of S II, S III, S IV, O II, and O III are found to be dominant in the plasma torus, at torus half width densities of 44, 160, 220, 50, and 340/cu cm, respectively, and lines of S V and K III may also be present. An effective electron temperature of 80,000 K is estimated for the central dense region near 6 Jupiter radii. Model calculations are in substantial agreement with other spectroscopic observations of the hot torus; however, the observations exhibit strong morphological differences with recent ground-based observations of S II emission, and calculated ion densities differ from in situ Voyager 1 plasma science measurements.

Shemansky, D. E.↗
NASA NTRS1984

Atomic mean excitation energies for stopping powers from local plasma oscillator strengths

The stopping of a charged particle by isolated atoms is investigated theoretically using an 'atomic plasma' model in which atomic oscillator strengths are replaced by the plasma frequency spectrum. The plasma-frequency correction factor for individual electron motion proposed by Pines (1953) is incorporated, and atomic mean excitation energies are calculated for atoms through Sr. The results are compared in a graph with those obtained theoretically by Inokuti et al. (1978, 1981) and Dehmer et al. (1975) and with the experimental values compiled by Seltzer and Berger (1982): good agreement is shown.

Wilson, J. W.↗
NASA NTRS1987

Laser magnetic resonance in supersonic plasmas - The rotational spectrum of SH(+)

The rotational spectrum of v = 0 and v = 1X3Sigma(-)SH(+) was measured by laser magnetic resonance. Rotationally cold (Tr = 30 K), vibrationally excited (Tv = 3000 K) ions were generated in a corona excited supersonic expansion. The use of this source to identify ion signals is described. Improved molecular parameters were obtained; term values are presented from which astrophysically important transitions may be calculated. Accurate hyperfine parameters for both vibrational levels were determined and the vibrational dependence of the Fermi contact interaction was resolved. The hyperfine parameters agree well with recent many-body perturbation theory calculations.

Hovde, David C.↗
NASA NTRS1990

Faraday rotation measure variations in the Cygnus region and the spectrum of interstellar plasma turbulence

Linear polarization observations were made of eight double-lobed radio galaxies viewed through the galactic plane in the Cygnus region. These observations have been used to determine intra- and intersource rotation measure differences; in some cases, unambiguous rotation measures have been extracted. The rotation measures are dominated by foreground magnetoionic material. The differences in rotation measure between pairs of sources correlate with angular separation for separations from 10 arcsec to 1.5 deg. These rotation measure fluctuations are consistent with a model in which the electron density varies on roughly 0.1-200 pc scales. The amplitudes of these variations are, in turn, consistent with those electron density variations that cause diffractive interstellar scattering on scales less than 10 to the 11th cm.

Lazio, T. Joseph↗
NASA NTRS1978

Extreme ultraviolet spectrum of a hot interstellar plasma

The EUV (100-1000 A) spectrum of an optically thin plasma over the temperature range 100,000-10 million K is calculated, and the effects of free-free, free-bound, and two-photon continuum radiation are considered. The resulting spectra are presented in graphical form, with a separate tabulation of intensities for the emission lines. Results in the 100-200 A region are compared with those of other workers, and the major sources of uncertainty in this type of calculation are discussed. The applicability of the results to EUV observations of the interstellar medium are also mentioned.

Stern, R.↗
NASA NTRS2016

Heating and Acceleration of Solar Wind Ions by Turbulent Wave Spectrum in Inhomogeneous Expanding Plasma

Near the Sun (< 10Rs) the acceleration, heating, and propagation of the solar wind are likely affected by the background inhomogeneities of the magnetized plasma. The heating and the acceleration of the solar wind ions by turbulent wave spectrum in inhomogeneous plasma is studied using a 2.5D hybrid model. The hybrid model describes the kinetics of the ions, while the electrons are modeled as massless neutralizing fluid in an expanding box approach. Turbulent magnetic fluctuations dominated by power-law frequency spectra, which are evident from in-situ as well as remote sensing measurements, are used in our models. The effects of background density inhomogeneity across the magnetic field on the resonant ion heating are studied. The effect of super- Alfvenic ion drift on the ion heating is investigated. It is found that the turbulent wave spectrum of initially parallel propagating waves cascades to oblique modes, and leads to enhanced resonant ion heating due to the inhomogeneity. The acceleration of the solar wind ions is achieved by the parametric instability of large amplitude waves in the spectrum, and is also affected by the inhomogeneity. The results of the study provide the ion temperature anisotropy and drift velocity temporal evolution due to relaxation of the instability. The non-Maxwellian velocity distribution functions (VDFs) of the ions are modeled in the inhomogeneous solar wind plasma in the acceleration region close to the Sun.

Ofman, Leon↗