Zonal flow and field generation by finite beta drift waves and kinetic drift-Alfvén waves

Abstract

A study of the generation of zonal flows and zonal magnetic fields by finite beta drift waves and kinetic drift-Alfvén waves is presented. The analysis is a generalization of recent investigations of the modulational instability for zonal flow generation by electrostatic drift waves to finite beta drift waves and kinetic drift-Alfvén waves. The drift wave driven unstable zonal flows/fields are stabilized by finite β below a critical value, due to the finite beta modification of the drift wave pump and the drift sidebands. They are, however, destabilized by coupling to the zonal field for larger β. The drift-Alfvén branch driven zonal flows/fields are found to be completely stable below a critical β, and are destabilized for larger β. These new results can find applications in a variety of laboratory and space plasma situations.