ROSAT observations of the Jupiter aurora

Abstract

Röntgen satellite (ROSAT) high‐resolution imager (HRI) and position sensitive proportional counter (PSPC) observations of Jupiter obtained in April 1991 and May 1992 reveal soft X ray emissions apparently associated with Jupiter's aurora and similar to X ray emissions observed earlier by the Einstein Observatory. The HRI images show emission mainly from Jupiter's northern hemisphere at all Jovian longitudes observed, and there is some indication of a longitudinal modulation of the emission in phase with the well‐known ultraviolet modulation of the northern aurora. The PSPC data reveal a very soft spectrum. Comparison of the observed spectrum with models for both electron bremsstrahlung radiation and line emission from S and O ions indicates that the line spectrum gives a much better statistical fit to the observed spectrum. The X ray observations presented here therefore support the hypothesis that ion precipitation is the most likely cause of the Jovian X ray emissions, a result first suggested by the Einstein results [ Metzger et al. , 1983].