Nonlinear decay of a large-ampitude ion-acoustic wave

This paper studies the nonlinear coupling between an ion—acoustic wave and two Alfvén waves. On the basis of the MHD equations, this three-wave interaction is described within the coupled normal-mode theory. It is shown that a largeamplitude acoustic wave can decay into a pair of Alfvén waves in a high-β plasma. Calculations of the threshold condition and the maximum growth rate suggest that this decay process may occur both in the laboratory and in the ionospher