Investigation of magnetospheric interactions with the Hermean surface

The magnetosphere of Mercury is populated by trapped particles, of which a significant proportion, certainly the Sodium and Potassium components, are generated by sputtering of the surface by solar UV, solar wind and by the trapped particles themselves. The surface is extensively modified by these processes, so that for Mercury studies of the surface and the magnetosphere form a single linked problem. The available evidence on the relationship between Mercury's surface and magnetosphere is described. We therefore consider new instrumental approaches to address directly the coupling of the radiation environment with the surface. One such instrument would be a neutral atom imager. Since neutrals travel on ballistic trajectories, but can have kinetic energies large compared to escape energy, it is possible to relate the information obtained about the surface to geographically well defined regions. Different energies yield information on different coupling processes. We can also obtain information on the global energy inputs to the system. The intense level of the radiation observed by Mariner suggests that the auroral zone, where the energetic radiation interacts with the surface, is a potential strong source of X-rays. We estimate the fluxes. The solar wind may also contribute to X-ray generation, particularly if it can reach the surface during highly excited periods.