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  • 1
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    Zeeman observations of W Sgr (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A new precise method for measuring magnetic fields on Zeeman plates of the southern Cepheid 'W Sgr' is reviewed. Ten plates over the 7.6(d) period of pulsation show two extrema in the measured values of the effective magnetic field. The method has a precision of + or - 0.4 microns in the Zeeman shift corresponding to + or - 50 Gauss (g). A negative spike of -220 g occurred at the time of arrival of the compressional wave of pulsation at the stellar surface. A positive field of +270 g occurred at the phase of most rapid contraction near the temperature minimum of the pulsation cycle.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 57-67
    Format: application/pdf
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  • 2
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    Infrared scans of Jupiter (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Spatial scans at eight wavelengths between 7.8 and 24 microns along Jupiter's meridian and along the Equatorial Zone, the North Equatorial Belt, and the South Tropical Zone are considered. Some features of these scans are differences in brightness temperatures between the Great Red Spot and the surrounding South Tropical Zone, a higher temperature at high northern latitudes than high southern latitudes, equal or possibly higher temperatures of zones than belts at 7.8 microns in contrast to higher temperatures of belts at other observed wavelengths, very strong limb darkening at 8.9 microns possibly due to a large scale height or a nonuniform distribution of solid NH3 particles, and inhomogeneities within belts and zones.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 42; Apr. 198
    Format: text
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  • 3
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    Infrared scans of Saturn (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Scans are presented at five wavelengths between 7.8 and 25 microns north-south along Saturn's central meridian and east-west parallel to the equator through the subearth point. The brightening of Saturn's South Pole at 12.7 microns was more enhanced in 1977 than in 1978 due to the 5 deg greater declination of the polar axis in 1977. There is a plateau in the Southern Hemisphere between -30 and -60 deg latitude in the 7.8 and 12.7 micron scans. The apparent temperature of the rings decreased as Saturn approached the equinox. It is found generally that the strongest ring emission arises from the C ring.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 42; May 1980
    Format: text
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  • 4
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    Five-micrometer measurements of Uranus and Neptune (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Five-micron brightness temperatures and brightness temperature upper limits for Uranus and Neptune have been obtained which are substantially lower than those of Jupiter and Saturn and which correspond to a geometric albedo of approximately 0.01, in agreement with results reported by Gillett and Rieke (1977). Phosphine and CH3D, which are observed at 5 microns on Jupiter and Saturn, are discussed as possible sources of opacity at 5 microns in the atmospheres of Uranus and Neptune.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 42; Apr. 198
    Format: text
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  • 5
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    Pioneer Venus plasma wave observations - The solar-wind-Venus interaction (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The Pioneer Venus plasma wave instrument is described with a discussion of wave observations throughout the typical near-noon and near-midnight orbits. This is followed by a comparison of the bow shock turbulence characteristics at earth and at Venus. The wave-particle interactions detected near the dayside ionopause are analyzed showing that the whistler mode Landau damping develops when the B field direction changes so that the whistler becomes oblique.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
    Format: text
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  • 6
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    Some fluid-dynamical problems in galaxies (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Galaxies are examined through their primary components of gas and stars. The normal spiral and barred spiral galaxies have gaseous and stellar constituents in a thin disk, with a prominent nuclear bulge in the inner parts. The gaseous disk of matter is considered as a large-scale motion of the interstellar medium in the presence of the collective gravitational field of the massive stellar component in normal and spiral galaxies. The stellar component is viewed from a fluid-dynamical perspective; finally the asymptotic theory, dynamical mechanisms, and modal maintenance are discussed.
    Keywords: ASTROPHYSICS
    Format: text
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  • 7
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    A cloud/particle model of the interstellar medium - Galactic spiral structure (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A cloud/particle model for gas flow in galaxies is developed that incorporates cloud-cloud collisions and supernovae as dominant local processes. Cloud-cloud collisions are the main means of dissipation. To counter this dissipation and maintain local dispersion, supernova explosions in the medium administer radial snowplow pushes to all nearby clouds. The causal link between these processes is that cloud-cloud collisions will form stars and that these stars will rapidly become supernovae. The cloud/particle model is tested and used to investigate the gas dynamics and spiral structures in galaxies where these assumptions may be reasonable. Particular attention is given to whether large-scale galactic shock waves, which are thought to underlie the regular well-delineated spiral structure in some galaxies, form and persist in a cloud-supernova dominated interstellar medium; this question is answered in the affirmative.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 245
    Format: text
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  • 8
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    Lightning on Venus - Orbiter detection of whistler signals (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Taylor et al. (1979) presented preliminary evidence for lightning on Venus, based on Pioneer Venus orbiter detection of whistler mode signals as the spacecraft first traversed the nightside ionosphere near periapsis. The initial periapsis eclipse season for the orbiter has been completed, and the plasma wave instrument obtained low-altitude nightside data for about 100 orbits. An analysis is presented of the impulsive whistler mode signals measured during these orbits, and the connection with atmospheric lightning is discussed. It is shown that the signals are detected in the 100-Hz channel when the local magnetic field is sufficiently strong and steady and when the field is oriented to point down below the ionosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
    Format: text
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  • 9
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    A comparative study of computational methods in cosmic gas dynamics (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Many theoretical investigations of fluid flows in astrophysics require extensive numerical calculations. The selection of an appropriate computational method is, therefore, important for the astronomer who has to solve an astrophysical flow problem. The present investigation has the objective to provide an informational basis for such a selection by comparing a variety of numerical methods with the aid of a test problem. The test problem involves a simple, one-dimensional model of the gas flow in a spiral galaxy. The numerical methods considered include the beam scheme, Godunov's method (G), the second-order flux-splitting method (FS2), MacCormack's method, and the flux corrected transport methods of Boris and Book (1973). It is found that the best second-order method (FS2) outperforms the best first-order method (G) by a huge margin.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 108; 1, Ap; Apr. 198
    Format: text
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  • 10
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    Spiral structure and star formation. I - Formation mechanisms and mean free paths (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The wide variety of optical appearances observed in spiral galaxies has encouraged the growth of two theoretical approaches to explain the spiral patterns exhibited by such young objects as OB associations, giant H II regions, and dark dust lanes. These approaches are related to the density wave theory of spiral structure and 'stochastic, self-propagating star formation'. Levinson and Roberts (1981) tried to reconcile these two theoretical approaches, and considered a disk filled with discrete gas clouds. The present investigation is concerned with refinements and extensions of the model of Levinson and Roberts. Attention is given to gravitational forces and dynamical propagation, cloud-cloud collisions, supernova interactions, computational models, a theory concerning the interactions of the gas cloud and stellar association systems, the time evolution of the gas cloud-stellar association systems, and aspects of collisionally triggered star formation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 277; 744-767
    Format: text
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