Propagation of Alfvén waves in ion-sound turbulent plasma

Abstract

The propagation of low-frequency, large-scale (compared to the ion Larmor frequency Ωi and radius Ri), oblique Alfvén waves in a turbulent plasma is investigated in the framework of kinetic theory. The turbulent field is the statistical average of one-dimensional ion-sound waves of very high frequency and short wavelength (ω ≫ ΩiRe≫ λ). In the absence of resonant particle effects, and to first order in a finite Larmor radius expansion, it is shown that the turbulence can lead either to spatial diffusion (damping) or anti-diffusion (growth), with Bohm scaling, of the low frequency wave. Finite Larmor radius and frequency effects in the propagation of oblique Alfvén waves are simultaneously obtained for arbitrary β plasma; the results can easily be generalized, merely by deforming certain integration contours, to obtain the corresponding Landau decrement.