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  • LUNAR AND PLANETARY EXPLORATION  (6)
  • Chemical Engineering
  • 1975-1979  (6)
  • 1
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    Comparison of calculated and measured ion densities on the dayside of Venus (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Data from the Pioneer Venus ion mass spectrometers are compared with model calculations of the ion density distributions appropriate for daytime conditions. The model assumes diffusive equilibrium upper boundary conditions for the major ions (O2(+), O(+), CO2(+), He(+), and H(+)); the agreement between the calculated and measured gross behavior of these ions is reasonably good except for H(+), which may be influenced strongly by convective transport processes. The distributions of five minor ions (C(+), N(+), NO(+), CO(+), and N2(+)) are also calculated for the chemically controlled region (less than approximately 200 km); the agreements are, in general, poor, an indication that the present understanding of the Venus minor ion chemistry is still incomplete.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 205; July 6
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 2
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    The energetics of the ionosphere of Venus - A preliminary model based on Pioneer Venus observations (1979)
    In:  Other Sources
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    Publikationsdatum: 2019-06-27
    Beschreibung: A model of the energy balance of the dayside ionosphere of Venus is presented. The coupled energy equations for electrons and ions are solved numerically and the calculated temperatures are compared with temperatures measured by instruments on the Pioneer Venus Orbiter. Neutral and ion density profiles consistent with those measured by various Pioneer Venus experiments are used in the model. It was found that using standard EUV sources and thermal conductivities the calculations produce temperatures that are much lower than the measured ones. Consequently, further calculations were performed in which (1) the thermal conductivities were inhibited by means of an almost horizontal magnetic field and/or (2) heat inflow into both the electron and ion gas at the top of the ionosphere was assumed due to the solar wind interaction. It was found that the calculated and measured temperatures were in reasonably good agreement if the thermal conductivities were inhibited by a near horizontal field of about 10 gammas and if the electron and ion heat fluxes were taken to be 4 x 10 to the 9th eV/sq cm/sec and 10 to the 7th eV/sq cm/sec, respectively.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geophysical Research Letters; 6; May 1979
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
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    The ionosphere and airglow of Venus - Prospects for Pioneer Venus (1978)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The paper presents model calculations for the Cytherean nighttime and daytime ionosphere. It is shown how some of the proposed mechanisms can be tested with the aid of the Pioneer Venus observations scheduled for December 1978. Theoretical calculations of the energetics of the Cytherean ionosphere are performed, and it is concluded that the Project Venus measurements will find elevated ion and electron temperatures, resulting primarily from energy fluxes associated in some manner with the solar wind. According to this model, the energy flux will act directly on the ion gas. Ultraviolet dayglow intensities were calculated, and it is anticipated that hundreds of kR's of CO2-related emission features such as the CO Cameron bands will be observed. Nightside ionosphere calculations were made assuming the precipitation of energetic electrons as an ionization source, and the intensities of some of the resulting emission features are calculated.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geophysical Research Letters; 5; July 197
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    A comprehensive model of the Venus ionosphere (1978)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: Coupled time-dependent continuity-momentum and energy balance equations for the Venus ionosphere were simultaneously solved for CO2(+), O2(+), O(+), He(+), and H(+) densities and electron and ion temperatures for an altitude range of 120-500 km. Values of the solar zenith angle varied from 0 deg (subsolar point) to 90 deg (terminator). The calculations include the horizontal bulk transport of ions by neutral winds but not the horizontal diffusion. The two-stream photoelectron transport method was used to find the heating rates for the ambient electrons. Different boundary conditions were considered, and a nightside ionosphere was calculated. The results of these model calculations are in good agreement with measurements in the region of maximum electron density. Characteristics of topside and nightside densities and temperatures are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research; 83; Mar. 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Electron temperatures in the Jovian ionosphere (1976)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The daytime electron temperature profile of the Jovian ionosphere was calculated, taking into account the effects of thermal conduction and heat inflow from the plasmasphere. The photoelectron fluxes and electron heating rates were determined by using the two-stream approach of Banks and Nagy (1970) and Nagy and Banks (1970). The calculated electron temperatures were found to follow the neutral temperature up to an altitude slightly above the electron density peak, while at higher altitudes they were significantly enhanced above the assumed neutral temperature value.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research; 81; Nov. 1
    Format: text
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  • 6
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    The Martian ionosphere in light of the Viking observations (1978)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: A theoretical model has been constructed in which the ion density and the ion and electron temperature distributions are calculated by solving the coupled continuity-momentum equations and the coupled energy equations. The latest experimental results from the Viking 1 and 2 landers are used to vary some of the parameters in the model in order to obtain agreement between the theoretical and experimental results. It is found that solar EUV radiation alone is not able to maintain the observed high ion temperatures. It was also established that the energy coupling between the electron and ion gas is insufficient to account for the measured ion temperatures even in the presence of very large electron temperatures. Direct heat input to the ion gas, probably due to solar wind-ionosphere interactions, can result in ion temperature values in reasonable agreement with the observations. The ion densities calculated with the present model agree well with the Viking observations in the chemically controlled region, but at higher altitudes, dynamic transport processes need to be invoked to achieve consistency among the observed and calculated temperature and density values.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research; 83; Aug. 1
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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