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

¹ Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany e-mail: andreasm4@yahoo.com
² Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA

Received: 19 November 2007
Accepted: 25 February 2008

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.