An analytical solution of finite-amplitude solitary kinetic Alfven waves

An analytical solution of finite-amplitude solitary kinetic Alfven waves (SKAWs) in a low-β (β much-lt me/mi much-lt 1) plasma is presented. This solution has been compared with the solution of the Korteweg--de Vries (KdV) equation in the small-amplitude limit. It is found that the KdV soliton solution is valid only for the maximum relative density perturbation Nm<0.1. For the larger Nm, the exact analytical solution shows that the SKAWs have a much wider structure and much stronger perturbed fields than the KdV solitons with the same Nm. Moreover, the relations between the width and the amplitude of SKAWs are also considerably different from that of the KdV solitons. In addition, the possibility for applying these results to some events observed from the Freja scientific satellite is discussed. (The Freja is a Swedish--German scientific project for the investigation of ionospheric and magnetospheric plasmas, and the Freja satellite was launched on a Long-March II rocket of China on October 6, 1992.) copyright 1995 American Institute of Physics