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| Titel |
Understanding of the Venus upper atmosphere dynamics with O2(a¹Δ) Venus Express observations |
| VerfasserIn |
L. Soret, J.-C. Gérard, 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 |
250063220
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| Zusammenfassung |
| The O2(a1Δ) nightglow emission at 1.27 μm may be used as a tracer of the dynamics
prevailing in the Venusian upper mesosphere. This emission has thus been observed with
ground-based telescopes and from space with instruments such as VIRTIS on board Venus
Express. Observations have shown that the emission maximum is statistically located close to
the antisolar point at ~96 km. As originally suggested by Connes et al. (1979), such an
emission results from the production of oxygen atoms on the Venus dayside by
photodissociation and electron impact dissociation of CO2 and CO, which are then
transported to the nightside by the subsolar to antisolar general circulation, where they
recombine to create excited O2(a1Δ) molecules. Their radiative deexcitation produces the
O2(a1Δ) nightglow with a maximum near the antisolar point. However, VIRTIS observations
indicate that the O2(a1Δ) nightglow emission is highly variable, both in intensity and
location. Actually, when considering individual observations, the patch of bright
emission is rarely located at the antisolar point and the brighter area around this point
is the result of statics accumulation. Also, when considering several individual
observations acquired in a short period of time, it is possible to follow an individual
emission patch and to deduce its displacement and its brightness variation due to
activation or deactivation. In this study, we analyze several sequences of VIRTIS
observations in order to understand the Venus upper mesosphere dynamics. We
show that the intensity can vary by several megaRayleighs in a couple of hours
with effective lifetimes on the order of several hours. The horizontal motion of
the spots leads to the conclusion that winds in the 95-100 km region are in the
range of 25 to 150 m s-1, in good agreement with the study by Hueso et al. (2008). |
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