Auroral oxygen precipitation at Jupiter

The Jovian aurora is much more powerful than the terrestrial aurora, and some of the auroral energy deposition is thought to come from energetic oxygen and sulfur precipitation. Auroral oxygen and sulfur ions deposit their energy in the atmosphere by means of ionization, dissociation, and heating processes. Energetic oxygen precipitation at Jupiter was previously modeled with the lowest four charge states (O, O + , O 2+ , and O 3+ ) (Horanyi et al., 1988). In this paper, the model will be extended to include all the charge states of oxygen from neutral oxygen up to fully stripped oxygen. The energy deposition by incident ions with energies in excess of about 200 keV/amu is largely determined by the higher charge states. The model extension is also needed to study auroral X ray emission by energetic highly charged ions. In this paper we estimate that a total auroral X ray power of about 10 8 W is produced by highly charged excited oxygen ions, which is in agreement with the X ray power observed at Jupiter by the Röntgen satellite (ROSAT; Waite et al., 1994). We also construct a “predicted” X ray energy spectrum for sulfur and oxygen ions which agrees rather well with the spectrum measured by ROSAT. Our calculations support the assertion made by Waite et al. (1994) that the Jovian X ray emission observed by ROSAT can be explained by energetic ion precipitation.