Electric Fields in Mercury's Magnetosphere

Returning to Mercury with the BepiColombo mission will provide a unique opportunity to obtain in situ information on the electric field in Mercury's magnetosphere. The electric field plays a crucial role for plasma transport in the magnetoshere, for transfer of energy between different parts of the system, and for propagation of information. Measuring the electric field we will be able to better understand plasma motion and wave propagation in Mercury's magnetosphere. Together with knowledge of the magnetic field a better understanding will be derived of the magnetospheric current systems and their closure at or near the planetary surface. Further insight into substorms at Mercury will be gained. We summarize the scientific case for electric field measurements on BepiColombo and outline the instrument design which, because of the harsh environment, is a challenging task.