LOCATION AND MAGNETOSPHERIC MAPPING OF SATURN'S MID-LATITUDE INFRARED AURORAL OVAL

Previous observations of Saturn's infrared aurorae have shown that a mid-latitude aurora exists significantly equatorward of the main auroral oval. Here, we present new results using data from four separate observing runs in 1998, 2003, 2008, and 2010. When combined, these provide a view of the mid-latitude aurora under a considerable range of viewing conditions, allowing the first calculation of the latitudinal position of this aurora to be made. This has shown that the mid-latitude aurora is located at the magnetic footprint of the region within the magnetosphere where the initial breakdown in corotation occurs, between 3R(S) and the orbit of Enceladus (similar to 3.95R(S)). We also confirm that this aurora is a continuous stable feature over a period of more than a decade and that an oval morphology is likely. When combined, these results indicate that the mid-latitude auroral oval is formed by currents driven by the breakdown process within the magnetosphere, in turn caused by mass loading from the torus of Enceladus, analogous with the volcanic moon Io's dominant role in the formation of Jupiter's main auroral oval.