Spacecraft charging in flowing plasmas; numerical simulations

The density and potential variations at and in the vicinity of a spacecraft in flowing plasmas are studied by numerical simulations. The spacecraft charging, wake formation, and their role for the diagnostics of the ambient plasma are addressed. It is demonstrated that the wake features, such as ion focusing, can be altered by photoemission due to directed sunlight. For multiple ion species, the wakes for ions with different ion masses can be separated, with light ions contributing to the ion focus, and heavy ions giving a geometrical shape of the wake. As a specific case, the Cassini spacecraft approaching Saturn is considered. The simulations are carried out with DiP2D and DiP3D codes, the two-and three-dimensional particle-in-cell codes.