AN ANALYTICAL SOLUTION OF FINITE-AMPLITUDE SOLITARY KINETIC ALFVEN WAVES

An analytical solution of finite-amplitude solitary kinetic Alfven wav es (SKAWs) in a low-beta (beta much less than m(e)/m(i) much less than 1) plasma is presented. This solution has been compared with the solu tion of the Korteweg-de Vries (KdV) equation in the small-amplitude li mit. It is found that the KdV soliton solution is valid only for the m aximum relative density perturbation N-m<0.1. For the larger N-m, the exact analytical solution shows that the SKAWs have a much wider struc ture and much stronger perturbed fields than the KdV solitons with the same N-m. Moreover, the relations between the width and the amplitude of SKAWs are also considerably different from that of the KdV soliton s. In addition the possibility for applying these results to some even ts observed from the Freja scientific satellite is discussed. (The Fre ja is a Swedish-German scientific project for the investigation of ion ospheric and magnetospheric plasmas, and the Freja satellite was launc hed on a Long-March II rocket of China on October 6, 1992.) (C) 1995 A merican Institute of Physics.