Global Structure and Thickness of Jovian Current Sheet

The field and plasma measurements in the magnetosphere of Jupiter from the Galileo spacecraft have helped us characterize a rotationally driven magnetosphere over a long period and under a range of solar wind conditions. The magnetic field observations in particular show that the Jovian magnetosphere displays strong temporal and local time variations. One of the strongest local time asymmetries in the magnetosphere is observed in the structure and thickness of the Jovian current sheet which is the main repository of its magnetospheric plasma. Variations in the thickness and therefore the plasma content of the current sheet with radial distance and local time are poorly understood because thickness determination requires a knowledge of the motion of the current sheet relative to the observing spacecraft which is hard to get. Consequently, no systematic studies have been performed so far that characterize the behavior of Jupiter's current sheet thickness in space and time.

By using a new technique that can determine the instantaneous motion of Jupiter's current sheet relative to the spacecraft, we can now quantitatively model the magnetic field and electron density dataset in terms of Harris current sheet type equilibria. The resulting estimates of the thickness and plasma content of the Jovian current sheet over all local times and radial distances show that the Jovian current sheet has a strong local time asymmetry being at its thinnest in the dawn sector and the thickest in the dusk sector. The current sheet thickness on the dayside is comparable to that in the dusk sector whereas the nightside current sheet thickness is intermediate between the dawn and dusk sector values. A comparison of the particle density and magnetic field profiles over different local times reveals that the plasma sheet (as defined by the electron density data) and the current sheet have very similar extents in various local time sectors.

We will discuss the insights provided by this new analysis into the generation and loss of plasma in Jupiter's magnetosphere. We will also discuss how various external and internal processes operating in the magnetosphere help transport and redistribute plasma in Jupiter's magnetosphere.