Nonlinear kinetic model for lower-hybrid solitary structures

Abstract

Nonlinear drift-kinetic theory is proposed for lower-hybrid solitary structures in near-Earth plasmas, based on a two time scale kinetic description of nonlinear interactions between the lower-hybrid and dispersive Alfvén waves. The detailed derivation of the nonlinear coupling terms in an arbitrary geometry is presented, that include the ponderomotive potential, non-curl-free component of the perpendicular electron velocity, and the electron diffusion in velocity space. It is shown that the resonant particles are trapped by the combined effects of the slow and ponderomotive potentials, and that their density is further modified by their diffusion in velocity space, yielding a new type of coherent structure, which is identified as an electron hole, coupled with a nonlinear Schrödinger-type soliton. A numerical solution is found in the form of train of soliton-like lower-hybrid spikes, trapped inside a weakly two-dimensional slab electron hole.