 |
| Titel |
Retrieving exospheric temperatures from dayglow emissions at Mars |
| VerfasserIn |
Cyril Simon Wedlund, Guillaume Gronoff, Stephen Bougher |
| Konferenz |
EGU General Assembly 2011
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053643
|
|
|
|
|
|
| Zusammenfassung |
| The Martian dayglow has been recorded by the UV spectrometer SPICAM onboard Mars
Express since 2004. A new data analysis of the SPICAM limb dataset is presented following
the description of Simon et al. (2009), with emphasis on the main emissions such as the CO
Cameron bands, the CO2+(B - X) ultraviolet doublet and OI (2972Å) as well as their
discretisation versus solar longitude, solar zenith angle and latitude. These emissions depend
on photoexcitation, electron impact excitation and dissociation processes, and could be good
tracers of the CO2 density profiles.
Exospheric temperatures are then retrieved from the individual dayglow altitude profiles
using two different techniques. The first one uses a direct fit of the emission profiles by a set
of barometric, Chapman-beta and Epstein functions to derive a scale height and hence an
associated temperature. The second technique uses a forward kinetic transport model, called
aeroplanet, in combination with inverse techniques to reproduce the emissions: the CO2
densities are then adjusted dynamically and an exospheric temperature is derived from
them.
Results suggest that the CO2+ emission is the best candidate for an accurate
retrieval of exospheric temperatures and that, at the altitudes considered between
120 and 180 km, the isothermal behaviour of the atmosphere may not always be
reached.
Variations with solar longitude of the exospheric temperatures are investigated by the
MTGCM global circulation model and compared with the observations. Good agreement
with observations is found for solar longitudes ranging from 140° and 300°, for solar
minimum to moderate conditions. |
|
|
|
|
|
|