On Astrophysical Turbulence

Abstract

Particle scattering in turbulent magnetic systems such as the solar wind or the inter- stellar medium depends on the properties of the turbulent fields ýB_i. In this chapter, it is demonstrated that the turbulence geometry, the wave spectrum, and the tem- poral behavior of these fields have to be specified. For the geometry, we employ the so-called slab/2D composite model, which is often used to approximate solar wind turbulence. Correlation functions for slab, pure 2D, and composite turbu- lence models are calculated, as well as field line diffusion coefficients. Although for slab geometry, the field line random walk can be described linearly, for more realistic models, a nonlinear formulation has to be applied. In this chapter, dif- ferent approaches to describe field line random walk linearly and nonlinearly are discussed. These results are the basis to describe theoretically particle transport in partially turbulent magnetic systems.