Unpublished conference/Abstract (Scientific congresses and symposiums)
The altitude of Saturn’s aurora: implications for the auroral electron energy and location of the polar homopause
Gérard, Jean-Claude; Bonfond, Bertrand; Gustin, Jacques et al.
2008European Planetary Science Congress 2008
 

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Keywords :
Saturn; Aurora
Abstract :
[en] The Space Telescope Imaging Spectrograph (STIS) and the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST) have been used to study the characteristics of Saturn’s FUV aurora, which is dominated by the Lyman and Werner bands of H2 and the H Lyman-α line. Images have been analyzed to determine the altitude of the emission above the limb and infer the characteristic energy of the auroral electrons. Our study shows that the peak of the emission is located 1000-1300 km above the limb, indicating that the precipitated electrons are mostly in the 0.1-1 keV energy range, that is significantly less than on Jupiter. Another source of information on the electron energy are the FUV spectra obtained with Voyager UVS (Sandel et al., 1982) and the HST-STIS (Gérard et al., 2004) and Cassini-UVIS spectrographs which only occasionally show a signature of absorption by hydrocarbons. Consequently, the emission is located above but close to the methane homopause. Finally, EUV spectra collected with the FUSE satellite (Gustin et al., 2008) provide information on the H2 column overlying the aurora through analysis of self-absorption and rotational temperature of the emitting layer from the intensity distribution among the H2 lines. If Moses et al. (2000)’s low latitude model is used to convert altitudes into pressure levels, H2 and hydrocarbon columns and temperature, discrepancies appear between the observed temperature, ultraviolet colour ratio and geometric altitude of the emission. One possibility is that the temperature near the homopause sharply increases at a pressure level higher than in the equatorial regions.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Gérard, Jean-Claude  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Bonfond, Bertrand  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Gustin, Jacques ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Grodent, Denis  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Clarke, John T.
Language :
English
Title :
The altitude of Saturn’s aurora: implications for the auroral electron energy and location of the polar homopause
Publication date :
23 September 2008
Event name :
European Planetary Science Congress 2008
Event organizer :
Europlanet
Event place :
Münster, Germany
Event date :
du 21 septembre 2008 au 26 septembre 2008
Audience :
International
Available on ORBi :
since 01 December 2011

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