Parametric study of kinetic Alfven solitons in a two electron temperature plasma

The nonlinear regime of the kinetic Alfven wave is studied in a collisionless low-beta plasma that is composed of a cold ion population and of two electron populations. In the one electron population plasma, it is known that solitary kinetic Alfven waves (SKAW) propagate either at the Alfven velocity nu(A) or at the ion-acoustic velocity c(s). In this latter case, only plasma compressions exist. In the two electron population plasma, rarefactions, as well as compressions, may exist at this velocity. Furthermore, when the electron-acoustic mode exists and when nu(A) > nu(ea) (nu(ea) is the electron-acoustic velocity), the inertia of the cold electron component allows for the existence of compressive SKAW which propagate with a velocity lying in a limited interval above nu(ea),. When nu A < nu(ea), these solitons are rarefactive and continuously evolve from classical SKAW moving at nu(A) to electron-acoustic-like SKAW moving at nu(ea). The possibility of applying these results to some astrophysical plasma observations is investigated. (C) 1999 American Institute of Physics. [S1070-664X(99)00302-X].