Cassini UVIS Observations of Jupiter's Auroral Variability

In the December 2000 Cassini flyby of the Jupiter system, the Cassini Ultraviolet Imaging Spectrograph (UVIS) monitored Jupiter's auroral emissions from day 275 of 2000 to day 81 of 2001. Much of the auroral variability can be explained simply in terms of the rotation of Jupiter's auroral arcs (measured by Hubble Space Telescope) with the planet. However, several brightening events were seen in which the global auroral output increased by a factor of 2-4. These events persisted over a number of hours and are tied to large solar coronal mass ejection events. The auroral UV emissions from these bursts also correspond to hectometric radio emission increases reported by the Galileo and Cassini Radio and Plasma Wave experiments. The 2 largest events were on 2000 day 280 and on 2000 day 325-326. We will look at these events in some detail, and compare them with corresponding information on the interplanetary magnetic field, solar wind conditions, and energetic particle environment to try to understand the cause of these auroral brightness increases.