Auroral storm on Saturn

Discovery of an auroral storm on Saturn. The images, in a false-orange brightness colour code, were taken with the Space Telescope Imaging Spectrograph (STIS) onboard HST at 11:30 UT on 7 December 2000 (a), and 10:00 UT on 8 December (b). The exposure time is 480 s, during which Saturn rotated by 5 degrees.

The north pole region is hidden behind the ring system owing to the large tilt of Saturn's rotation axis at that time. Conversely, the whole region limited by the southern auroral oval is visible from Earth. Note the similarity in geometry and the differences in nightside brightness between the auroral oval on both days, but especially the very bright feature visible poleward of the dawnside oval on 7 December. This feature has totally disappeared on 8 December (image and text: Nature 432 78)

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