ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1985-1989  (11)
  • 1
    facet.materialart.
    Unknown
    CO2impact ionization-driven plasma instability observed by Pioneer Venus Orbiter at periapsis (1985)
    American Geophysical Union
    Details
    Publication Date: 1985-01-01
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    Observations of energetic ions on the nightside of Venus (1987)
    American Geophysical Union
    Details
    Publication Date: 1987-01-01
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Wavelike perturbations observed in the neutral thermosphere of Venus (1988)
    American Geophysical Union
    Details
    Publication Date: 1988-01-01
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    Wavelike perturbations observed in the neutral thermosphere of Venus (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Wavelike perturbations are evident in the neutral thermosphere measurements of He, N, O, N2, and CO2 by the Pioneer Venus orbiter neutral mass spectrometer. In the wavelength range from 100 to 600 km, the amplitudes of the various species are comparable in magnitude, with CO2 having the largest amplitude, and with helium out of phase with respect to the heavier species. On the dayside, the small-scale variations of CO2 and N2 increase with increasing altitude from 170 to 210 km, with CO2 having the largest slope. Simple and complex wave structures are observed, including wave trains and pulselike events. There is more activity during nighttime than during daytime, and larger values of the activity occur in the vicinity of the predawn and postdusk terminator sectors. Below 160 km, the standard deviation of the CO2 density on the nightside is 12 percent, about 3 times the daytime value. The data are consistent with the interpretation that the density perturbation are due to gravity waves propagating upward from the lower thermosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 93; 11237-11
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    Empirical model of the composition of the Venus ionosphere Repeatable characteristics and key features not modeled (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: In-situ measurements of positive ion composition of the ionosphere of Venus are combined in an empirical model which is a key element for the Venus International Reference Atmosphere (VIRA) model. The ion data are obtained from the Pioneer Venus Orbiter Ion Mass Spectrometer (OIMS) which obtained daily measurements beginning in December 1978 and extending to July 1980 when the uncontrolled rise of satellite periapsis height precluded further measurements in the main body of the ionosphere. For this period, measurements of 12 ion species are sorted into altitude and local time bins with altitude extending from 150 to 1000 km. The model results exhibit the appreciable nightside ionosphere found at Venus, the dominance of atomic oxygen ions in the dayside upper ionosphere and the increase in prominence of atomic oxygen and deuterium ions on the nightside. Short term variations, such as the abrupt changes observed in the ionopause, cannot be represented in the model.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 9, 19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 6
    facet.materialart.
    Unknown
    CO2 impact ionization-driven plasma instability observed by Pioneer Venus Orbiter at Periapsis (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Observations of enhanced ac electric field noise about Pioneer Venus periapsis are shown to be related to spacecraft-generated impact ionization of the ambient CO2. The frequency of the electric field noise is found to peak in the vicinity of the CO2(+) ion plasma frequency and to closely follow the form of the neutral CO2 density profile. When the electric field noise in all channels is normalized by the square root of the CO2 number density, the ratio is constant. Since the impact electron density measured by the Pioneer Venus Langmuir probe, is observed to scale directly with the neutral CO2, the growth of the electric field amplitude is found to be linear in time with a growth rate proportional to the CO2(+) ion plasma frequency. On the basis of these results the impact ionization-driven instability is shown to be the ion acoustic instability. Implications for the lack of observations by Pioneer Venus of reflected-O(+)-driven instabilities, as have been proposed for the space shuttle, are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 6631-663
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unknown
    On the diurnal variations in the temperature and composition - A three-dimensional model with superrotation (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An improved (Mayr et al., 1980) three-dimensional multiconstituent spectral model of the Venus thermosphere dynamics is presented, which describes the diurnal variations in the atmospheric composition (in terms of O, CO, and CO2 densities obtained by ONMS and OIMS, temperature, and wind fields on the basis of simplified theoretical interpretations of data obtained by the Pioneer Venus mission. The improved model accounts for nonlinear processes, includes higher order tidal elements, and describes the major gases in self-consistent form. Also presented is a self-consistent, nonlinear solution from a two-dimensional quasi-axisymmetric spectral model which describes the four-day superrotation in the lower atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 9, 19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 8
    facet.materialart.
    Unknown
    Observations of energetic ions on the nightside of Venus (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Ions with energy greater than 40 eV have been measured on the nightside of Venus by the Pioneer Venus orbiter neutral mass spectrometer (ONMS). For periapsis altitudes beyond 1500 km, they are confined to solar zenith angles greater than 120 deg. The nightside energetic ion composition at 2000 km resembles the nightside thermal ion composition occurring at 1000 km with the dominant species being O(+). Postflight laboratory calibrations performed on the ONMS backup unit have been used to estimate the energetic O(+) ambient flux and density. The direction from which the energetic ions appear to be coming can be determined because the ONMS is mounted at an angle with respect to the spin axis of the spacecraft. Both tailward and antitailward components of the apparent ion flow are exhibited when projected into the ecliptic plane. The major component of the apparent ion flow is observed perpendicular to the ecliptic plane.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 291-298
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 9
    facet.materialart.
    Unknown
    Fast O(sup +) ion flow observed around Venus at low altitudes (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Pioneer Venus Orbiter Neutral Mass Spectrometer (ONMS) has observed fast O(+) ions with an energy exceeding 40 eV in the spacecraft reference frame. The orbit of the spacecraft is nearly polar with periapsis near the equator. The ONMS is mounted at an angle to the spin axis which, in turn, is perpendicular to the ecliptic plane. From the spin modulated data the direction of the ion flow in that plane can be determined. Data from the first 11 diurnal cycles (orbits 1 to 2475) are vector averaged in order to display the general flow pattern. Plots of the averaged data are presented. On the dayside and near the terminators, where fast O(+) is observed near the ionopause, the directions are more or less parallel to the planet's surface with evidence of an asymmetry about the Sun-Venus line. On the nightside below 2000 km and near the equator there is a preferred dawn to dusk direction while at higher altitudes (lower solar zenith angles and higher latitudes) the flow direction is more antisunward. The averaged flux for this time period is 8x10 to the 5th/sq cm/s with a maximum of 5x10 to the 8th.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-100717 , REPT-89B0053 , NAS 1.15:100717
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 10
    facet.materialart.
    Unknown
    In situ results on the variation of neutral atmospheric hydrogen at Venus (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The concentrations of neutral hydrogen, n(H), in the Venus atmosphere were derived from an ion and neutral charge exchange relationship involving O(+), H(+), O, and CO2, which were measured by OIMS and ONMS on board the Pioneer Venus for the period 1979-1980 covering three diurnal cycles of Venus. There was a persisting dawn bulge in the diurnal distribution of n(H), which peaked at levels near 5 x 10 to the 7th/cu cm at altitudes below 165 km. Large day-to-day variations of up to a factor of 5 in n(H) were frequently encountered, in addition to some local time variations in the bulge location. Although the appreciable short-term variability in n(H) makes precise assessment of the interannual variations difficult, no distinct evidence for interannual variation in n(H) was found. These results were confirmed by the facts that no significant interannual differences in n(H3) measured directly by ONMS were detected, and that only small (not more than 10 percent, decline) variations in the solar EUV flux were found in the 1979-1980 period.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 9, 19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...