SOLITARY KINETIC ALFVEN WAVES ON THE ION-ACOUSTIC VELOCITY BRANCH IN A LOW-BETA PLASMA

Starting with an exact nonlinear equation governing solitary kinetic A lfven waves (SKAWs), a new type of SKAW on the ion-acoustic velocity b ranch is obtained in a low-P plasma. It propagates in a direction obli que to the ambient magnetic field, has a dispersion originating from t he finite perpendicular wavelength, and is accompanied by a density hu mp soliton similar to that of the SKAWs on the Alfven velocity branch in the case of 1 much greater than beta much greater than m(e)/m(i). I t has a perturbed electric field with the same order as that of the la tter SKAWs, but its perturbed magnetic field is weaker by a factor of (beta/2)(1/2), and in the small amplitude limit, the analytical result also lends to the Korteweg-de Vries soliton. (C) 1996 American Instit ute of Physics.