Cosmic ray transport in partially turbulent space plasmas with compressible magnetic turbulence

TL;DR

This paper extends a cosmic ray transport theory to include compressible magnetic turbulence in space plasmas, deriving new Fokker-Planck coefficients and diffusion limits for more realistic plasma conditions.

Contribution

It generalizes previous incompressible plasma models to compressible cases, allowing for arbitrary gyrophase deviations and deriving new transport coefficients.

Findings

Derived gyro-phase averaged Fokker-Planck coefficients for compressible turbulence.

Established upper limits for diffusion coefficients in the plasma.

Extended the theoretical framework to more realistic plasma conditions.

Abstract

Recently a new transport theory of cosmic rays in magnetized space plasmas extending the quasilinear approximation to the particle orbit has been developed for the case of an axisymmetric incompressible magnetic turbulence. Here we generalize the approach to the important physical case of a compressible plasma. As previously obtained in the case of an incompressible plasma we allow arbitrary gyrophase deviations from the unperturbed spiral orbits in the uniform magnetic field. For the case of quasi-stationary and spatially homogeneous magnetic turbulence we derive in the small Larmor radius approximation gyro-phase averaged cosmic ray Fokker-Planck coefficients. Upper limits for the perpendicular and pitch-angle Fokker-Planck coefficients and for the perpendicular and parallel spatial diffusion coefficients are presented.