Properties of Jupiter’s auroral acceleration region inferred with HST-STIS spectral images

Jupiter’s dynamic auroral region is the signature of magnetosphere-ionosphere coupling. Precipitating auroral electrons are part of a current system which transports angular momentum from the planetary atmosphere to sub-corotating magnetospheric plasma. The magnitude of the currents and hence precipitating energy flux, are sensitive to the characteristics of the high-latitude magnetosphere, in particular the location of the auroral acceleration region (AAR) and the density and temperature of the high-latitude electron population. We use HST STIS observations of Jupiter’s aurora (Gustin et al. [2016]) to infer the location of the AAR and the properties of the precipitating auroral electrons. To do this, we determine the energy of the precipitating electrons and incident energy flux for the two distinct regions within the main aurora and within flare regions. The resulting relationships between energy flux and electron precipitation energy for the main auroral emission are then compared to the theoretical relationship derived by Lundin & Sandahl [1978], in order to derive the location of the AAR and the temperatures and densities of the electrons at the top of the AAR prior to acceleration. We find that that each emission region is best reproduced using a multiple auroral acceleration regions with different properties, rather than a single auroral acceleration region with a varying potential drop strength.