Pitch-angle scattering in pure two-dimensional and two-component turbulence

Abstract

Aims. It has been demonstrated that quasilinear theory is inappropriate for describing pitch-angle scattering and parallel spatial diffusion, if a turbulence model with a strong two-dimensional component is assumed. We aim to revisit this problem using a more systematic and reliable approach.Methods. We consider particle transport in pure two-dimensional turbulence, by using a vector-potential description of pitch-angle scattering.Results. It is demonstrated that pitch-angle scattering in pure two-dimensional turbulence behaves subdiffusively and, thus, parallel scattering is expected to behave superdiffusively. In the slab/2D composite model, the total pitch-angle Fokker-Planck coefficient reaches the slab limit when very long timescales are considered.. © 2008 ESO.