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  • ASTROPHYSICS  (6)
  • PLASMA PHYSICS  (3)
  • *Anaphase
  • Life Sciences (General)
  • 1995-1999
  • 1980-1984  (9)
  • 1982  (9)
  • 1
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    Observational dispersion relations (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Pulse propagation in plasmas has been widely studied in relation to instabilities and their classification as convective or absolute. Such analyses emphasize the importance of considering the summation of a spectrum of modes, rather than simply making deductions from Brillouin dispersion relations plotted either for real frequency and complex wavenumber, or for complex frequency and real wavenumber. In particular, erroneous conclusions may be drawn about the magnitude and direction of propagation of a transient pulse. In this paper, the point of view is taken that an observer remote from the source would measure an 'observational dispersion relation'. The nature of this dispersion relation is examined for absorbing or convectively unstable plasmas by asymptotic analysis, and for different source waveforms. Illustrative results are presented for propagation in cold plasmas and for beam-plasma interaction.
    Keywords: PLASMA PHYSICS
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  • 2
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    Astrophysical tests for radiative decay of neutrinos and fundamental physics implications (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-20098)
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 257
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  • 3
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    A new view of baryon symmetric cosmology based on grand unified theories (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: (Previously announced in STAR as N82-10969)
    Keywords: ASTROPHYSICS
    Type: In: Progress in cosmology; Sep 14, 1981 - Sep 18, 1981; Oxford
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  • 4
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    The evolution of structure in the universe from axions (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A scenario where axions provide the dark matter in the universe is considered. Fluctuations in the axion field density produced by domain walls and strings cause the appearance of axion clumps of masses of order 10 to the 6th power solar mass which most likely collapse to black holes by or at the time that the universe becomes axion dominated at T is approximately 10 eV. These objects form the building blocks for a clustering hierarchy theory of galaxy and supercluster formation on scales up to approximately 10 Mpc and approximately 10 to the 15th power solar mass.
    Keywords: ASTROPHYSICS
    Type: NASA-TM-84963 , NAS 1.15:84963 , REPT-660
    Format: application/pdf
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  • 5
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    A model of a comet coma with interstellar molecules in the nucleus (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The coma of a comet is modeled assuming the icy nucleus contains interstellar molecules. This composition overcomes discrepancies between observation and earlier model predictions for CN, C2, C3, and NH2 abundances. It is found that the abundances of CN, C2, and C3-bearing compounds in the nucleus must be constrained to trace amounts in order to account for the observed column densities. NH3 also cannot be abundant by more than about 1%. The model gives good agreement with observed relative ranges of neutral species in the coma as well as with their observed relative intensity dependence on heliocentric distance. The size of the nucleus and the heliocentric ranges considered are relevant to comet Halley.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 108; 2, Ap; Apr. 198
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  • 6
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    Photochemical processes in the inner coma (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Models for the inner-coma chemistry of comets are reviewed. The physics relevant to the coma's chemistry is summarized, and the interaction of solar radiation with the coma is described, along with photolytic and chemical processes. The formation and destruction of several observed species are traced through a chemical reaction network, and model results are compared with observations. The species considered include CN, C2, C3, NH2, CH, CO, CO(+), OH, H2O, HCO, C2H4, and C2H3. The models most consistent with observations are shown to indicate that only trace amounts (2% in all) of molecules bearing CN, C2, C3, and NH2 can be present in the nucleus of a comet.
    Keywords: ASTROPHYSICS
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  • 7
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    Transient effects in beam-plasma interactions in a space simulation chamber stimulated by a fast pulse electron gun (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Interest in the interaction of electron beams with plasma generated by ionization caused by the primary electron beam was stimulated by the need to develop special vacuum tubes to operate in the kMHz frequency region. The experiments of Getty and Smullin (1963) indicated that the interaction of an energetic electron beam with its self-produced plasma resulted in the emission of wave energy over a wide range of frequencies associated with cyclotron and longitudinal plasma instabilities. This enhanced the thermal plasma density in the vicinity of the beam, and the term Beam-Plasma Discharge (BPD) was employed to described this phenomenon. The present investigation is concerned with some of the transient phenomena associated with wave emission during the beam switch-on and switch-off periods. Results are presented on the changes in electron energy spectra on a time scale of tens of milliseconds following beam switch-on. The results are discussed in terms of the beam plasma discharge phenomenon.
    Keywords: PLASMA PHYSICS
    Type: Artificial particle beams in space plasma studies; Advanced Research Institute; Apr 21, 1981 - Apr 26, 1981; Geilo; Norway
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  • 8
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    Studies of beam plasma interactions in a space simulation chamber using prototype Space Shuttle instruments (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: In March, 1981, electron beam experiments were conducted in a large space simulation chamber using equipment destined to be flown aboard NASA's Office of Space Science-1 pallet (OSS-1). Two major flight experiments were involved. They include the Vehicle Charging and Potential (VCAP) experiment and the Plasma Diagnostics Package (PDP). Apparatus connected with VCAP included a Fast Pulse Electron Gun (FPEG), and a Charge and Current Probe (CCP). A preliminary view is provided of the results obtained when the electron emissions were held steady over relatively long periods of time such that steady state conditions could be obtained with respect to the electron beam interaction with the neutral gases and plasma of the vacuum chamber. Of particular interest was the plasma instability feature known as the Beam Plasma Discharge. For the present experiments the FPEG was used in a dc mode with a range of currents of 2 to 80 mA at a beam energy of 970 eV. Attention is given to the emissions of VLF and HF noise associated with the dc beam.
    Keywords: PLASMA PHYSICS
    Type: Artificial particle beams in space plasma studies; Advanced Research Institute; Apr 21, 1981 - Apr 26, 1981; Geilo; Norway
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  • 9
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    Far-infrared sources in Cygnus X - An extended emission complex at DR 21 and unresolved sources at S106 and ON 2 (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A new map of 90 micron emission with 15 arcmin resolution is presented of a complex of sources approximately centered on DR 21. The emission is primarily from diffuse sources. Comparison of the 90 micron map with maps at 20 microns and 2.7 GHz leads to a model for diffuse sources in which there are at least two components of interstellar dust, one at 40 K and one at 165 K, responsible for the 90 micron and 20 micron emission respectively. Both components and the ionized gas must be mixed together; dust in an outer neutral shell is relatively unimportant for these sources. The diffuse sources have small infrared excesses and weak temperature gradients. Unresolved, probably compact, sources were observed at S106 and ON 2 and are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 261
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