Global current systems in the magnetosphere of Mercury.

Abstract

The global current systems of a planet represent electrodynamic interactions between its different parts, and between its magnetosphere and the ambient solar wind. Although some local currents of Mercury's magnetosphere have already been revealed by previous observational studies, the global picture of current systems in Mercury's magnetosphere remains unknown. Here we reconstruct the global current systems in the Mercury's magnetosphere, using five years magnetic field and plasma measurements made by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. It reveals a complex picture: a magnetopause current, cross-tail current, inner and outer equatorial ring currents and an unexpected polar ring current. The equatorial ring currents and the polar ring current agree with the prediction of the plasma drifting model in a region with a pressure gradient. These ring currents could reshape Mercury's magnetosphere and reveal new dynamics and energy transfer processes in Mercury.