Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsm33a1553s&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SM33A-1553
Physics
[2704] Magnetospheric Physics / Auroral Phenomena, [2776] Magnetospheric Physics / Polar Cap Phenomena, [5706] Planetary Sciences: Fluid Planets / Aurorae, [6275] Planetary Sciences: Solar System Objects / Saturn
Scientific paper
Observations of Saturn's infrared aurorae have shown that in addition to the main auroral oval, which is believed to be associated with the solar wind, there are significant polar emissions. Ground-based infrared observations of Saturn have been able to show that there is a general level of raised emission across the entire polar region, in a similar way to that seen at Jupiter. However, with direct observations of the aurora made from orbit around Saturn by the Cassini-VIMS instrument, this aurora was shown to be more than a relative generalised brightening in the infrared. Instead, a unique auroral feature was observed to occur, appearing as a large region of bright polar emission, positioned poleward of 82 degrees latitude. This Bright Polar Aurora emission is significantly different from the recently observed subrotating Q-branch auroral emission seen in both the ultraviolet and infrared, as it is separated from the main auroral oval by a region of low emission. This effectively produces a cap of bright aurora inside the main auroral oval, surrounded by a dark ring that separates the two aurorae. Here, we take a more detailed look at this cap of emission and examine the way the auroral feature develops with time. Bright Polar Aurora emission has been observed in two separate VIMS images. A more detailed analysis of the polar emission shows that each of these images in fact differs in structure; the first has auroral emission across the whole polar cap >82 degrees, but within the second the emission is concentrated on the dusk side. While the dramatic in-filling of the polar cap is not seen within any UV observations, the Hubble Space Telescope has observed transitory duskward auroral features within the polar cap, in a similar location to the duskward feature seen in the infrared. Using ground-based infrared observations, which allow a Bright Polar Aurora event to be broken into shorter timescale steps, it is possible analyse the progression of the infrared auroral emission with time, connecting the morphology seen within the two VIMS images with those in the ultraviolet.
Badman Sarah V.
Brown Harvey R.
Grodent Denis C.
Lystrup Makenzie B.
Melin Henrik
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