SOLITARY KINETIC ALFVEN WAVES IN THE 2-FLUID MODEL

Employing the two-fluid model, a generalized Sagdeev equation governin g solitary kinetic Alfven waves (SKAWs) and the criterion for the exis tence of SKAWs, which are valid for different ranges of plasma pressur e parameter beta, are presented. In the limit cases of beta much great er than m(e)/m(i) and beta much less than m(e)/m(i), the present resul ts correspond, respectively, with conclusions obtained by Hasegawa ct al. [Phys. Rev. Lett. 37, 690 (1976)] and by Shukla et al. [J. Plasma Phys. 28, 125 (1982)], that is, SKAWs accompanied by, respectively, hu mp and dip density solitons for beta much greater than m(e)/m(i) and b eta much less than m(e)/m(i). However, for the case of beta similar to m(e)/m(i), the present results show that SKAWs accompanied by both hu mp and dip density solitons are possible, and lead to KdV solitons in the small amplitude limit. In addition, the possibility for applying t hese results to electromagnetic spikes observed by the Freja scientifi c satellite is discussed [detailed information about the Freja satelli te experiments can be found in serial papers presented in Space Sci. R ev. 70, Nos. 3/4 (1994)]. (C) 1996 American Institute of Physics.