Whistler Wave Instabilities in the Collisionless Current Sheet

Whistler wave instabilities in the collisionless current sheet have been studies in the present paper by solving general dispersion relation obtained from the 2.5-dimenssional and incompressible MHD model (Physical model A) of the paper [4]. In this MHD model, the electron pressure tensor is used in the generalized Ohm's law. The results show that whistler waves can be directly excited by the collisionless current sheet. At the neutral sheet (z/d_i=0), whistler waves are basically stable in a broad range of wave number. Inside the ion inertial region (z/d_i < 1), obliquely propagating whistler waves are unstable. At the edge of ion inertial region (z/d_ii=1), obliquely propagating whistler waves have larger growth rate and higher frequency range. Besides, waves propagating towards the neutral sheet (k_zd_i < 0) have larger growth rate than that propagating away from the neutral sheet (k_zd_i > 0). There are two kinds of whistler waves:one with the parallel wave number larger and the other with the parallel wave number smaller than the perpendicular wave number.