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  • 1
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    Negative ions in the coma of Comet Halley (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The detection of negatively charged cometary ions in the inner coma of Comet Halley is reported. These ions are observed in three broad mass peaks at 7-19, 22-65, and 85-110 AMU, with densities reaching greater than about 1/cu cm, about 0.05/cu cm, and about 0.04/cu cm, respectively, at a distance of about 2300 km from the nucleus. The ion species thought to be present include O(-), OH(-), C(-), CH(-), CN(-) and heavier complex CHO molecular ions. As negative ions are easily destroyed by solar radiation at about 1 AU, an efficient production mechanism, so far unidentified, is required to account for the observed densities. The detection of negative ions in the coma near 1 AU implies that negative ions should also be present in similar neutral gas and dust environment farther away from the sun. If the negative-ion densities are large enough, they could play an important part in physical processes such as radiative transfer or charge exchange.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 349; 393-396
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  • 2
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    The composition of heavy molecular ions inside the ionopause of Comet Halley (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The RPA2-PICCA instrument aboard the Giotto spacecraft obtained 10-210 amu mass spectral of cold thermal molecular ions in the coma of Comet Halley. The dissociation products of the long chain formaldehyde polymer polyoxymethylene (POM) have recently been proposed as the dominant complex molecules in the coma of Comet Halley; however, POM alone cannot account for all of the features of the high resolution spectrum. An important component of the dust at Comet Halley is particles highly enriched in carbon, hydrogen, oxygen, and nitrogen relative to the composition of carbonaceous chondrites. Since this dust could be a source for the heavy molecules observed by PICCA, a search was conducted for other chemical species by determining all the molecules with mass between 20 and 120 amu which can be made from the relatively abundant C, H, O, and N, without regard to chemical structure.
    Keywords: ASTROPHYSICS
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 451-452
    Format: application/pdf
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  • 3
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    The upstream region, foreshock and bow shock wave at Halley's Comet from plasma electron measurements (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Halley plasma electron parameters from 2.7 million km from the comet nucleus to the bow shock wave at 1.1 million km and beyond are surveyed. The features of the electron foreshock lying outside the shock to a distance of 230,000 km are described. It is a region of intense solar wind-comet plasma interaction in which energetic electrons are prominent. Several spikes of electrons whose energies extend to 2.5 keV appear in front of the shock. These energetic electrons may be accelerated in the same way electrons are accelerated at the Earth's bow shock to energies of 1 to 10 keV. The direction of the electron bulk flow direction changes abruptly between 1920 and 1922 UT, and the flow speed begins a sharp decline at the same time. It is suggested that the spacecraft entered the bow shock wave between 1920 and 1922 UT. Electron density variations at Halley are very much smaller than those at Giacobini-Zinner.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 1: Plasma and Gas; p 259-261
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  • 4
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    Radial variations of flow parameters and composition of cold heavy ions within 50,000 km of Halley's nucleus (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Composition and flow parameter of cold heavy ions from the PICCA instrument on Giotto within a cometocentric distance of 50,000 km are presented. A distinct boundary at about 27,000 km, where the flow parameters changed abruptly, is identified and its physical significance is discussed. Radial profiles of heavy ion groups and abundance ratios are given.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 1: Plasma and Gas; p 199-201
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  • 5
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    Derivation of heavy (10-210 AMU) ion composition and flow parameters for the Giotto PICCA instrument (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The Giotto heavy ion analyzer RPA2-PICCA was designed to identify the composition and distribution of heavy thermal positive ions in the coma of comet Halley. The instrument is an electrostatic analyzer which takes advantage of the large relative flyby velocity and the fact that the ions in the inner coma should be cold and predominantly singly charged. A method of deconvolving E/Q measurements to yield ion mass composition, temperature, and flow velocity is presented. The measurements are used to investigate the dynamic behavior of the ions and variations in mass composition as a function of cometary distance.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 1: Plasma and Gas; p 203-205
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  • 6
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    A stable particle component 30 to 400 keV in interplanetary space (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Res. in the Space Sci., v. 2; 21 p
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  • 7
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    Energetic particles in space (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A review is presented of observations of suprathermal particles in the interplanetary medium along with new data on low energy particles from experiments aboard the ISEE spacecraft. Energy spectra of protons in the near earth atmosphere are plotted in the rest frame of the solar wind noting that at energies above 10 to the 9th eV, the galactic cosmic ray electron component has an unattenuated access into the heliosphere. Solar transient events such as flares accelerate and release energetic particles into the interplanetary medium; flare particle fluxes generate shock waves propagating past 1 AU following the event. It is concluded that the energy spectra for shock wave accelerations show a characteristic shape in accordance with the power law with a rapid steepening at high energies.
    Keywords: ASTROPHYSICS
    Type: Solar Physics; 67; Sept
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  • 8
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    Lunar particle shadows and boundary layer experiment: Plasma and energetic particles on the Apollo 15 and 16 subsatellites (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The lunar particle shadows and boundary layer experiments aboard the Apollo 15 and 16 subsatellites and scientific reduction and analysis of the data to date are discussed with emphasis on four major topics: solar particles; interplanetry particle phenomena; lunar interactions; and topology and dynamics of the magnetosphere at lunar orbit. The studies of solar and interplanetary particles concentrated on the low energy region which was essentially unexplored, and the studies of lunar interaction pointed up the transition from single particle to plasma characteristics. The analysis concentrated on the electron angular distributions as highly sensitive indicators of localized magnetization of the lunar surface. Magnetosphere experiments provided the first electric field measurements in the distant magnetotail, as well as comprehensive low energy particle measurements at lunar distance.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-140371 , SSL-SER-15-ISSUE-31
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  • 9
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    A kinky heliospheric current sheet - Cause of CDAW-6 substorms (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Two magnetospheric substorms and the intensification of the second are caused by interplanetary magnetic field and ram pressure changes associated with a kinky heliospheric current sheet (KHCS). The responsible interplanetary features occur in a highly compressed region between a solar flare-associated shock wave and the cold driver gas. The possibility that the interplanetary structure is a 'magnetic cloud' is ruled out.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 11; 339-342
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  • 10
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    Complex organic ions in the atmosphere of Comet Halley (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The ordered series of broad mass groups in thermal ion mass spectra from the coma of Comet Halley obtained with the Positive Ion Cluster Composition analyzer is examined. It is found that the series is characteristic of molecules rich in H, C, N, and O, and does not necessarily imply the presence of a long chain polymer, such as polyoxymethylene. It is suggested that the spectra resemble those of singly-bonded CH2, NH, O, and H units which are similar to the molecules detected in laboratory analogs of icy interstellar dust grains.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 9; 2 19; 35-39
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