Inward diffusion and acceleration of particles driven by turbulent fluctuations in magnetosphere

Abstract

Charged particles in a magnetosphere are spontaneously attracted to a planet while increasing their kinetic energy via the inward diffusion process. A constraint on particles' micro-scale adiabatic invariants restricts the class of motions available to the system, giving rise to a proper frame on which particle diffusion occurs. We investigate the inward diffusion process by numerical simulation of particles on a constrained phase space. The results reveal the emergence of the inhomogeneous density gradient and anisotropic heating, which is consistent with spacecraft observations, experimental observations, and the recently formulated diffusion model on the constrained phase space.