Ion velocity distributions in a partially ionized plasma.
Steady state ion velocity distribution functions for partially ionized gas not in thermal equilibrium, noting small distortion
Banks, P. M.↗
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Correlation effects in semi-infinite plasmas
Pair correlations in ionized gas combined to half space by perfectly reflecting boundary
Guernsey, R. L.↗
Experimental observation of low-frequency oscillations described by the plasma continuity equations.
Electron number density LF oscillations for ionized gas identified with periodic solutions to neutral and charged particle plasma continuity equations
Roth, J. R.↗
A theory of moving striations based on the continuity-equation plasma oscillation.
Moving striations as plasma oscillations arising from transit time delays of neutral and charged particles moving through ionized gas, using continuity equation
Roth, J. R.↗
Electron-ion recombination - A critical review of theories and experimental results for an argon plasma
Partially ionized gas electron-ion recombination rate coefficients calculation methods compared with Ar plasma data
Clark, K. J.↗
The cosmic helium abundance
Cosmic helium abundance was studied through the interior structure of young stars, profiles of helium absorption lines in the photospheric spectra of hot young stars, and emission-line spectrum of ionized gas. It is concluded that helium occurred before galaxies were formed. Inconsistencies found in the quasar spectra are briefly mentioned.
Searle, L.↗
Absence of Lyman-alpha emission from the Coma cluster of galaxies.
The redshifted L alpha flux from the Coma cluster of galaxies is determined to be less than 6000 photons per cm sq per sec, leading to severe (and perhaps fatal) new restrictions on hot ionized gas models for the gravitational binding of the cluster.
Henry, R. C.↗
The influence of the ionized medium on synchrotron emission in interstellar space.
The effect of the ionized gas on synchrotron emission in the interstellar medium is investigated. A detailed calculation of the synchrotron emissivity of cosmic electrons, assumed to have an isotropic pitch-angle distribution in a uniform magnetic field, is made as a function of frequency and observation angle with respect to the field. The results are presented both as a local emissivity and as an intensity, the latter obtained by neglecting free-free absorption in the interstellar medium and by assuming that the emissivity is constant along the line of sight. The comparison of these results with previous studies on the nature of the low-frequency turnover of the galactic nonthermal radio background reveals that, except if the component perpendicular to the line of sight of the interstellar magnetic field is small (less than 1 microgauss), or if the cosmic-ray electron spectrum is cut off at energies below a few hundred MeV, the suppression of synchrotron emission by the ambient electrons has in general a lesser effect than free-free absorption by these electrons, and that in some cases this suppression effect is almost entirely negligible.
Ramaty, R.↗
Near infra-red magnitudes of 248 early-type emission-line stars and related objects.
Nearly 250 early-type emission-line stars have been observed in the near infrared; approximately two thirds of these are found to exhibit excess radiation at these wavelengths. Two distinct mechanisms may contribute to the infra-red excesses: thermal radiation from circumstellar dust, and electron bremsstrahlung originating in a shell of ionized gas. It is not currently possible to distinguish between these two alternatives using infra-red photometry alone.
Allen, D. A.↗
Microwave conductivity of slightly ionized gases and electromagnetic scintillations
Two areas of research are briefly summarized. The first is concerned with calculating the conductivity of a slightly ionized gas. A method is proposed which involves an expansion of the Boltzmann collision operator (of the electron distribution function, involving the neutral gas-electron interactions) in powers of the electron-gas mass ratio. The second area of investigation focuses on the problem of a radio wave propagating through the interplanetary medium, taking account of the decreasing plasma density with distance from the sun.
Mintzer, D.↗
New infrared sources associated with H II regions
The H II regions studied have generally been those which contain OH or H2O maser sources and which have been shown to contain compact condensations of ionized gas which may be connected with star formation processes. A brief account of two such sources, W3 and NGC 7538, is given. On the basis of the reported observations it is concluded that in general H II condensations are infrared sources in the range from 3 to 20 microns. The condensations are hidden optically by large quantities of obscuring matter.
Wynn-Williams, C. G.↗
Helium abundance at the galactic center
We suggest that the low abundance of ionized helium in H II regions at the galactic center can be explained by selective absorption of helium-ionizing photons by dust within the ionized gas. This model requires an extrapolation to 500 A of the rapid increase of the extinction measured between 1500 A and 1000 A with the Copernicus satellite, and it assumes that the dust absorbs most of the Lyman continuum.
Jura, M.↗
Far-infrared emission from H II regions. II - Multicolor photometry of selected sources and 2.2 min resolution maps of M42 and NGC 2024
Medium- and broad-bandwidth photometric measurements have been made of seven compact H II regions at wavelengths between 30 and 650 microns. The results are consistent with the hypothesis that the far-infrared flux is continuum radiation from dust grains. Color temperatures range from 33 to 85 K. For most of the sources, the infrared flux is low enough so that the dust could conceivably be mixed with the ionized gas. In at least one case, however, the far-infrared spectrum and luminosity of the source cannot be reconciled with reasonable grain models unless the far-infrared flux comes from a shell surrounding the H II region. M42 (Orion) and NGC 2024 (Orion B) have been mapped at 90 microns with a resolution (half-power beam diameter) of 2.2 min. Although the peak far-infrared brightness in M42 occurs at the position of the Kleinmann-Low infrared nebula, most of the flux originates in a more extended (about 6 x 8 min) source. The energy for the diffuse component could be supplied by the stars in the Trapezium cluster. However, the single early-type star visible in NGC 2024 is not luminous enough to account for either the infrared flux or the observed free-free flux.
Harper, D. A.↗
Dust in H2 regions
The effects of dust inside H2 regions were studied by means of theoretical models of dusty nebulae. Infrared observations were analyzed and clear evidence was found that the emitting dust is mostly mixed with the ionized gas. Some information about the amount, distribution, and properties of dust grains was also derived.
Panagia, N.↗
Spectral and spatial resolution of the 12.8 micron Ne 2 emission from the galactic center
High-resolution spectra of the Ne II 12.8 micron fine-structure line in emission from the galactic center cloud Sgr A West show a line-center LSR radial velocity of + 75 + or - 20 km/sec. and a velocity dispersion of about 200 km/sec. The line has been observed with spectral resolution as high as 0.10/cm and spatial resolution as high as 8 sec. This appears to provide a direct measurement of conditions in the 45 sec. ionized region at the galactic center. The radial velocity and dispersion are more-or-less independent of position and indicate that events as recent as the last 4 million years have given the ionized gas a systematic motion with respect to the massive stellar component of material at the galactic center. An upper limit for the mass approximately equal to four million times the solar mass was obtained from the velocity distribution, with the mass located within 0.8 parsecs of the galactic center.
Wollman, E. R.↗
Spectral and spatial resolution of the 12.8 micron Ne II emission from the galactic center
High-resolution spectra of the Ne II 12.8-micron fine-structure line in emission from the galactic-center cloud Sgr A West show a line-center LSR radial velocity of +75 (+ or - 20) km/s and a velocity dispersion of about 200 km/s. The line has been observed with spectral resolution as high as 0.10 micron/cm and spatial resolution as high as 8 arcsec. This appears to provide a direct measurement of conditions in the 45-arcsec ionized region at the galactic center. The radial velocity and dispersion are more or less independent of position and indicate that events as recent as the last 10,000 years have given the ionized gas a systematic motion with respect to the massive stellar component of material at the galactic center. An upper limit of the order of 4 million solar masses for the mass within 0.8 pc of the galactic center is obtained from the velocity dispersion.
Wollman, E. R.↗
Plasma igniter for internal-combustion engines
Hot ionized gas (plasma) ignites air/fuel mixture in internal combustion engines more effectively than spark. Electromagnetic forces propel plasma into combustion zone. Combustion rate is not limited by flame-front speed.
Breshears, R. R.↗
A scaling law for energy transfer by inelastic electron-molecule collisions in mixtures
The equation governing the electron energy distribution in the presence of a spatially uniform electric field in a weakly ionized gas was reformulated into an integral equation for the logarithmic slope of the distribution function. For gas mixtures in which the dominant electron energy loss mechanism is by vibrational excitation of the molecules, this equation is suitable for approximate analysis and exact numerical solution by iteration. Superelastic collisions are easily included in this formulation, and do not seriously effect the convergence of the numerical scheme. The approximate analytical results are only qualitatively correct, but suggest appropriate parameters which correlate the exact numerical results very well. The distribution function as well as certain gross properties such as net energy transfer into vibration, mean energy, and drift velocity depend primarily on a single nondimensional parameter involving only E/N and the cross sections.
Bienkowski, G. K.↗