Nonlinear Evolution of a Resonant Interchange Mode

Abstract

A resonant instability due to the presence of a small number of superthermal particles with an adverse spatial gradient in a hydromagnetically stable well configuration is examined. It is found that resonant diffusion leads to a stable quasilinear plateau in the distribution function. Wave scattering redistributes the wave spectrum from the linearly unstable region to a region of lower wavenumber, at the same time transferring energy to the particles. The nonlinear wave particle scattering leads to a diffusion equation in which only electrons can interact resonantly. In addition, there is a nonresonant contribution to diffusion due to the adiabatic response of electrons and ions to the time changing wave spectrum after stabilization. The net result is that ions and electrons diffuse at an equal rate with no charge separation developed.