Modeling Jupiter's magnetospheric currents using Pioneer data - Evidence for a low-latitude cusp

The Jovian magnetospheric field measured by Pioneer 10 and 11 can be well modeled by a combination of current systems composing an azimuthally symmetric current disk, a dusk-dawn current sheet in both the dayside and the nightside magnetosphere, and an image dipole to represent the effects of currents on the magnetopause. The inclusion of a dusk-dawn current sheet in the dayside magnetosphere allows observations obtained both inbound and outbound to be simultaneously fit by an azimuthally symmetric current disk (i.e., without the need for local time dependent current densities). Similar disk current intensities are found to describe both Pioneer 10 and Pioneer 11 encounters. During the Pioneer 10 inbound passage the magnetopause was rapidly pushed inside the spacecraft position by a solar wind compression event. The changes that occurred in the magnetospheric field at this time can be described by relatively simple changes in the model parameters. The most striking feature of the models is that they suggest that the Jovian cusp is at much lower latitudes than is the case with the earth's magnetosphere.