3-D Fully Kinetic Particle-in-Cell Simulations of Small Asteroid Charging in the Solar Wind

This paper presents a 3-D, fully kinetic particle-in-cell (PIC) simulation study of plasma charging for small, irregularly shaped, composite asteroids in the solar wind. Three types of asteroid internal structures are considered: 1) a homogeneous composition of regolith; 2) a single hard rock; and 3) a composite of hard rock core covered with a regolith outer layer. The simulation model resolves the plasma flow field, asteroid surface differential charging, and asteroid internal electric field self-consistently. The results show that while the ambient plasma condition and surface property determine surface charging, the internal composition substantially affects the subsurface electric field inside an asteroid.