Analysis of Extreme and Far Ultraviolet Observations of Saturn’s Atmosphere Christopher D. Parkinson Cassini UVIS Team Meeting January 09, 2014

Analysis studies address the following unresolved issues of Saturn's atmosphere: (1) are there temporal variations in eddy mixing at Saturn? (2) is there evidence for enhanced mixing in the auroral regions of Saturn (as was done for Jupiter (Parkinson et al., 2006) and what is its relationship (if any) to the observed polar vortex? (3) do possible longitudinal asymmetries in the Saturnian He 584 Å and H Lyman-α brightnesses exist, how do they compare to the observed asymmetries at Jupiter, and what are the implications?

Differences between V1/V2 and Cassini Epoch Observations Possible causes could be shadowing of the northern/southern hemisphere of the planet by the rings, which wasn't the case during the Voyager measurements seasonal variations, viz., the data examined from the start of Cassini mission falls approximately 24 and 23 years following the V1 and V2 encounters respectively differences in the solar flux

Data analysis Looking for H Lyman- and He 584 Å longitudinal asymmetries as well as other non-longitudinal airglow cases He 584 A line IS present with sunlit disk averaged brightness of 0.6 +/- 0.1 R obtained (5-sigma detection) H Lyman- present at 1 kR with large S/N

He 584 Å line is definitely present with a sunlit disk averaged brightness of 0.6 +/- 0.1 R obtained (5-sigma detection) It would appear that the Cassini He 584 brightness for this sample is lower than during the Voyager epoch with the corresponding effects on Kh

Small timescale observations with shorter integration times

Compare ~ 1 R for Cassini to the Voyager values shown in Figures 4 and 5 in Parkinson et al., 1998 For their standard parameters, Kh would be ~3x107 cm2s-1, and using the EUVT94 model solar flux, ~3x106 cm2s-1 for Cassini measurements. C C

Spatial representation: edge of planet clearly at row 16 and 46 for both EUV and FUV Ring shadow effects In the northern hemisphere? S N

The north-south profile of the He 584 Å emission for Jupiter, measured on 14-15 December 2000 at a spatial resolution of 0.25 Rj. Increasing detector row corresponds to a south to north direction.