Heuristic Description of Perpendicular Transport

Abstract

Abstract The problem of the transport of energetic particles across a mean magnetic field is known since more than 50 years. Previous attempts to describe perpendicular transport theoretically were either based on complicated non-linear theories or computationally expensive simulations. In either case it remained unclear how particles really experience perpendicular transport. In this paper I will present a heuristic approach to solve this problem. Simple arguments will lead to several formulas for the perpendicular diffusion coefficient. These formulas include well-known cases such as compound sub-diffusion and the field line random walk limit but also newer cases such as the collisionless Rechester and Rosenbluth limit. Furthermore, analytical theories such as NLGC and UNLT theories contain a correction factor a2 which is often assumed to be 1/3. The heuristic approach discussed in this article explains this value as well.