Jovian sulfur nebula

We present further results of our observations of the nebula of singly ionized sulfur in the magnetosphere of Jupiter. We have calculated the occupation numbers of the five lowest energy levels of ionized sulfur and have used their results together with our observed intensities to evaluate the number density of ionized sulfur. The results are consistent with the existence near Io orbit of a plasma characterized by an electron temperature of 10 eV and a number density of 500 ions/cm³, of which roughly 25% are sulfur. The nebula is shown to be a semidisc with a void near Io, a radius of 6R, and a thickness of 2R. We discuss some of the implications of these findings.