“Characteristics of Saturn’s polar atmosphere ... FUSE and Cassini/UVIS spectra” by Gustin et al,

“Characteristics of Saturn’s polar atmosphere and auroral electrons derived from HST/STIS,
FUSE and Cassini/UVIS spectra” by Gustin et al,
Ultraviolet spectra of Saturn's aurora obtained with the Hubble Space Telescope Imaging
Spectrograph (STIS), the Cassini Ultraviolet Imaging Spectrograph (UVIS) and the Far
Ultraviolet Spectroscopic Explorer (FUSE) have been compared to synthetic spectra of electronexcited H2 in order to derive various auroral characteristics, such as the energy of the primary
precipitating electrons and the H2 temperature at the altitude of the aurora. Two physical
processes have been exploited: the absorption by hydrocarbons in the FUV and H2 selfabsorption in the EUV.
We find energies in the range 10-18 keV, which locates Saturns’s aurora between 0.1 and 0.3
µbar. We also determined that the auroral H2 emission is characterized by a temperature of
~400K, consistent with temperatures measured in the infrared, but much higher than what is
expected from equatorial atmospheric models. These new results bring valuable constraints on
both polar atmospheric models and theoretical studies of the ionosphere-magnetosphere coupling.
Gustin, J., J.-C. Gérard, W. Pryor, P.D. Feldman, D. Grodent and G. Holsclaw