Jupiter's Polar Cap Aurora

The morphology of Jupiter’s ultraviolet aurora is commonly described in terms of components located inside (poleward of) or outside (equatorward of) the main oval emission. These components may also be discriminated by their temporal behaviour, where the narrowest parts of the main “oval” remain relatively stable over time periods of several hours, and the satellite footprints show large variability with timescales of minutes. Inside the main emission the so-called polar aurora, presumably corresponding to the polar cap mixing open and closed magnetic field lines, is characterized by rapid motions taking the form of swirls, giving rise to the “swirl region” and by intermittent brightenings in the “active region”. Coarse analysis of these motions suggests that they are too fast to respond to an equatorial magnetospheric forcing. Instead, they appear to be related to processes taking place in or above the ionosphere where distances travelled by plasma waves match those of the subtended auroral emission. Here, we present a preliminary improved analysis of the auroral motion in the polar region based on the application of an iterative “Advection Corrected Correlation Image Velocimetry” (ACCIV) method (Asay-Davis et al., 2009). This method allows one to build velocity fields quantifying local and overall auroral motions which may then be used to constrain their origin.