Saturn temperature and H2 profiles from Solar EUV occultations Jacques Gustin Jacques Gustin – UVIS team meeting – Boulder June 27-29

 What can be learned from Solar occs in EUV?  which absorbing species attenuate the emission in EUV? Jacques Gustin – UVIS team meeting – Boulder June 27-29

Absorption dominated by H2 in <1120 Å, HC >1120 Å In 1046-1113 Å: H2 bands (Greathouse et al., 2010 stellar occ jupiter New Horizons) transmission in 1046-1113 Å informs on H2 structure and T structure Jacques Gustin – UVIS team meeting – Boulder June 27-29

Method:  Create a synthetic T profile: T0: asymptotic T high P T: asymptotic T low P Zm: altitude of max gradient : ~ gradient dT/dz Derive H2 density profile from T profile assuming hydrostatic equilibrium. Last parameter needed: nH2(z*) Jacques Gustin – UVIS team meeting – Boulder June 27-29

Application to the observations: S, n2(s),T(s) LOS UVIS abs. Spec. Unabs. Spec. MRH 1 bar start with unabsorbed solar spectrum and T, H2 profiles from start values of the 5 parameters for each MRH: total tau =  = (H2(s), T) ; (H2LW)  templates for all J of v"=0 get an absorbed spectrum for each MRH (= transmission curve) parameters vary until min 2 Jacques Gustin – UVIS team meeting – Boulder June 27-29

 Observations: Jacques Gustin – UVIS team meeting – Boulder June 27-29

 8 cases: medium lat. high lat. 250 km

 Results: Jacques Gustin – UVIS team meeting – Boulder June 27-29

Jacques Gustin – UVIS team meeting – Boulder June 27-29

 Best parameters: Jacques Gustin – UVIS team meeting – Boulder June 27-29

ACS FUSE FUSE

Jacques Gustin – UVIS team meeting – Boulder June 27-29

Conclusions: - Exospheric T higher than expected - Exospheric T not higher for high lats - T & H2 profiles different for high/med. lats (from T gradient) - Variability with latitude & seasons Next: - sensitivity study - apply method to Voyager occs - simulate HC profiles with these T profiles (implication for auroral studies) Jacques Gustin – UVIS team meeting – Boulder June 27-29