Ulysses observations of corotation lags in the dayside Jovian magnetosphere: An evaluation of the hinged magnetodisc and magnetic anomaly models

Abstract

Ulysses observations during the inbound leg of the February 1992 encounter with Jupiter offer the opportunity to evaluate both the hinged magnetodisc and the magnetic anomaly models currently used to describe the Jovian magnetospheric corotation lag. Particle and field detectors on board Ulysses measure signatures of the current and plasma sheets. The locations of these sheets in radius and system III longitude are then used as inputs to the models. It is shown that the hinged magnetodisc model is able to explain some characteristics of the data but unable to explain others. The magnetic anomaly model appears to account for the overall nature of the magnetospheric corotational lag; however, it, too, cannot fully account for the Ulysses data. A modification of the magnetic anomaly model is offered which adequately explains the Ulysses data and, with the assumption of a sufficiently significant, time-dependent Iogenic plasma source, explains data from previous Jupiter encounters as well.