Interaction of suprathermal electron fluxes with lower hybrid waves

Abstract

Several in situ measurements performed in the terrestrial magnetosphere and in the solar wind have evidenced the simultaneous presence of whistlers or lower hybrid waves with suprathermal fluxes or beams of electrons. The so-called fan instability, which can be driven by an anisotropy of the energetic electron velocity distribution along the ambient magnetic field, can play an essential role in space plasmas where energetic electron fluxes are ubiquitous. By destabilizing waves at the anomalous cyclotron resonance, this instability can modify drastically the shape of the parallel velocity distribution and give rise to bumps in the tail. This paper presents a new theoretical model which allows one to describe the nonlinear interaction of a packet of lower hybrid waves with a nonequilibrium electron distribution function. This Hamiltonian self-consistent model, which is based on a semianalytical approach, provides an efficient and original tool to point out new physical features, especially in what concerns the nonlinear stage of the fan instability and its implications for space physics.