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| Titel |
The oxygen nightglow emissions of Venus: vertical distribution and role of collisional quenching |
| VerfasserIn |
J.-C. Gérard, L. Soret, A. Migliorini, G. Piccioni, P. Drossart |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063309
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| Zusammenfassung |
| Three-body recombination of atomic oxygen produces O2 molecules excited in different
electronic states such as a 1Δg, b 1 -
g+, A 3 -
u+, c 1 -
uand A’ 3Δu, each with a specific
quantum efficiency. When they radiate, optical transitions are observed in a wide range of
wavelengths extending from the ultraviolet to the near infrared. In planetary atmospheres,
spontaneous radiative deexcitation compete with collisional quenching with ambient
molecules and atoms. As a consequence, the corresponding airglow emission profiles
may significantly differ from each other in brightness and altitude of the emitting
layer.
We model the volume emission rates and limb profiles of the O2 Atmospheric Infrared (a
1Δ-X 3 -
), Herzberg I (A 3 --X 3
-
), Herzberg II (c 1 -
-X 3 -
), Chamberlain (A’ 3Δ-a
1Δ) bands expected on the Venus night side. The quenching rates are taken from laboratory
and observational planetary data and we apply two different methods to determine the
oxygen and CO2 density profiles. One is based on recent analysis of data collected by
instruments on board the Venus Express mission. The second one uses a one-dimensional
chemical-diffusive model where the free parameters are the strength of turbulent transport
and the downward flux of O atoms. Both approaches indicate that the calculated
intensities of each transition range over several orders of magnitude and that differences
are expected in the altitude of the maximum emission. These predictions will be
compared with VIRTIS/Venus Express limb observations, which make it possible to
derive the vertical distribution of the O2 emissions in the visible and infrared. These
measurements suggest that no difference is observed between the altitude of the
peak of the IR Atmospheric and Herzberg II bands. Conclusions will be drawn
about the validity of the current set of quenching coefficients used in the model. |
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