The influence of adiabatic focusing on particle diffusion is an important topic in space and plasma physics. In the past several authors have explored the influence of along-field adiabatic focusing on parallel diffusion of charged energetic particles. In this paper by using the Unified NonLinear Transport (UNLT) theory by Shalchi (SH2010) and the method of He and Schlickeiser (HS2014) we derive a new nonlinear perpendicular diffusion coefficient for non-uniform background magnetic field. This formula demonstrates that particle perpendicular diffusion coefficient is affected by along-field adiabatic focusing. And we also find that perpendicular diffusion coefficient is dependent on the sign of adiabatic focusing. For the diverging background magnetic field along-field adiabatic focusing makes spatial perpendicular diffusion coefficient $\kappa_\bot$ increase, that is, more particles diffuse across the diverging mean field than that in the uniform mean field. For converging case the spatial perpendicular diffusion coefficient $\kappa_\bot$ decreases for the reason of adiabatic focusing.
J. Wang, G. Qin, Q. Ma, et. al.
Wed, 8 Mar 17