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  • ASTROPHYSICS  (13)
  • INSTRUMENTATION AND PHOTOGRAPHY  (7)
  • 1
    Publikationsdatum: 2011-08-19
    Beschreibung: The observation of one of the largest magnetic clouds ever observed at a distance of 1 AU, with a diameter of greater than about 0.4 AU, is reported. The cloud is shown to be almost unchanged structurally by interaction with the earth bow shock. The first observations are reported of an auroral activity response to the passage of a magnetic cloud, with a nearly immediate increase in auroral activity when the IMF theta(B) angle reversed polarity to negative near the cloud center. The results provide strong evidence that turbulent magnetic fields behind interplanetary shocks are a possible cause of Forbush decreases, but contest the idea that relatively smooth, strong fields in clouds are a cause of such decreases. The cloud field modeling supports the existence of magnetic force-free fields in describing cloud structure.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 96; 9425-943
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2011-08-19
    Beschreibung: The observations by the ion composition instrument (ICI) on the ICE spacecraft made during the encounter with comet P/Giacobini-Zinner (Ogilvie et al., 1986) are discussed in detail. Solar wind He-4(2+) kinetic temperatures, densities, and velocities before, during, and after the encounter are presented. These data combined with He-4(2+) velocity distributions provide evidence for the existence of a thick diffuse shock. Relative abundances of water group ions and CO(+) are derived along with an estimate of the abundance of an ion with M/Q = 24 + or - 1 amu/e. The ICI data are compared with electron data from two other experiments (Bame et al., 1986; Meyer-Vernet et al., 1986) and found to be in reasonable agreement in the region outside the tail. Spectroscopic data for several neutral and ionic species are compared with the ICI results for the water group ions and CO(+). The spectroscopic data are also used to eliminate Mg(+) and CN(+) as candidates for the M/Q = 24 peak. The two most likely candidates are C2(+) and Na(+), but neither photoionization of parent neutrals nor sputtering from dust grains is sufficient to explain the observed abundance relative to H2O(+).
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 92; 39-46
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2011-08-19
    Beschreibung: During the crossing of the ICE spacecraft through the coma of the comet Giacobini-Zinner, ions with a mass/charge ratio 24 + or - 1 were unexpectedly found. Na(+) and/or Mg(+) would fit into this mass range. Processes that could lead to high metal ion abundances in cometary comas are discussed and it is concluded that evaporation or sputtering from silicate grains are not likely to be responsible. A remaining possibility is the occurrence of alkali metals in the icy phase as a result of either cometary differentiation or cocondensation of these elements with the icy component prior to the accretion of cometary bodies.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 166; 1-2,; L1-L4
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    In:  Other Sources
    Publikationsdatum: 2011-08-19
    Beschreibung: The paper reviews results on the plasma regime at Comet Giacobini-Zinner obtained by the International Cometary Explorer. The observations are consistent with the existence of a weak shock which may be pulsating, but do not exclude the suggestion that the shock, though present around the subsolar point, is an the process of decaying to a wave on the flanks. 'The pick-up' of cometary ions leads to ion cyclotron, mirror, beam, and electrostatic instabilities which cause strong turbulence in the inner coma.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 5; 12, 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    In:  Other Sources
    Publikationsdatum: 2011-08-16
    Beschreibung: The performance of an upconversion system is examined for observation of astronomical sources in the low to middle IR spectral range. Theoretical values for the performance parameters of an upconversion system for astronomical observations are evaluated in terms of the conversion efficiencies, spectral resolution, field of view minimum detectable source brightness, and source flux. Experimental results of blackbody measurements and molecular absorption-spectrum measurements using a lithium niobate upconverter with an argon-ion laser as the pump are presented. Estimates are given of the expected optimum sensitivity of an upconversion device that may be built with presently available components.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Applied Optics; 15; Apr. 197
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2011-08-16
    Beschreibung: Black body measurements and absorption spectra of methane near 3.3 microns are presented and used as examples in a discussion of upconversion spectrometry for astrophysical application. Factors determining the system conversion efficiency and the minimum detectable flux for a typical system are presented. The spectrometer described uses an Argon-ion laser and a temperature turned LiNbO3 crystal in a CW mode. Satisfactory agreement between measured and calculated performance parameters is obtained. An estimate of the highest performance parameters attainable using current technology is given.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Format: text
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  • 7
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    In:  Other Sources
    Publikationsdatum: 2011-08-17
    Beschreibung: Two plasma regimes were observed in the Venus wake, one characterized by negative-going anisotropies accompanied by high bulk speeds and low magnetic variance, and the other characterized by positive-going anisotropies accompanied by low bulk speeds and high magnetic variance. The two modes alternate in time in a stochastic bimodal fashion as interplanetary magnetic field discontinuities propagate past Venus and switch on the positive anisotropies. The positive mode probably represents enhanced planetary ion pickup which results in instabilities, the damping of which energizes the electrons in the distant wake.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research; 83; Apr. 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 2011-08-19
    Beschreibung: The International Cometary Explorer spacecraft passed through the coma of comet Giacobini-Zinner about 7800 kilometers antisunward of the nucleus on September 11, 1985. The ion composition instrument was sensitive to ambient ions with mass-to-charge ratios in the ranges 1.4 to 3 atomic mass units per electron charge (amu/e) and 14 to 33 amu/e. Initial interpretation of the measurements indicates the presence of H2O(+), H3O(+), probably CO(+) and HCO(+), and ions in the mass range 23 to 24; possible candidates are Na(+) and Mg(+) and Mg(+). In addition to these heavy ions, measured over the velocity range 80 to 223 kilometers per second, the instruments measured He(2+) of solar wind origin over the range 237 to 463 kilometers per second. The heavy ions have a velocity distribution which indicates that they have been picked up by the motional electric field, whereas the light ions are steadily decelerated as the comet tail axis is approached. These results are in agreement with the picture of a comet primarily consisting of water ice, together with other material, that sublimes, streams away from the nucleus, becomes ionized, and interacts with the solar wind.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Science (ISSN 0036-8075); 232; 374-377
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 2019-06-28
    Beschreibung: The cometary bow wave of P/Giacobini-Zinner has been analyzed using the complete set of ICE field and particle observations to determine if it is a shock. Changes in the magnetic field and plasma flow velocities from upstream to downstream have been analyzed to determine the direction of the normal and the propagation velocity of the bow wave. The velocity has then been compared with the fast magnetosonic wave speed upstream to derive the Mach number and establish whether it is supersonic, i.e., a shock, or subsonic, i.e., a large amplitude wave. The various measurements have also been compared with values derived from a Rankine-Hugoniot analysis. The results indicate that, inbound, the bow wave is a shock with M = 1.5. Outbound, a subsonic Mach number is obtained, however, arguments are presented that the bow wave is also likely to be a shock at this location.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA-CR-180515 , NAS 1.26:180515 , DE87-005121 , LA-UR-87-40 , CONF-8610207-7
    Format: application/pdf
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  • 10
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    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2018-12-01
    Beschreibung: Triaxial electron detector differential energy analyzer for use in sounding rockets
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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