ELECTROMAGNETIC INSTABILITIES IN A GYROTROPIC AND NONGYROTROPIC HYBRID SOLAR-WIND-LIKE PLASMA

We study the stability of electromagnetic waves for nongyrotropic velo city distribution functions in a solar-wild-like plasma. The dispersio n relation is solved numerically in dosed form. On the basis of recent ly reported observations of such plasma distribution functions in the solar wind at 1.3 AU, we study the instabilities of transverse electro magnetic waves propagating in the direction of an external magnetic fi eld driven by ion beams and thermal anisotropies. We show that electro magnetic waves have three instability bands in the frequency range, 0 < omega < Omega(p), Omega(p) < omega < 2 Omega(p), and 2 Omega(p), < o mega < 3 Omega(p). Our results are illustrated by using parameters con sistent with observed nongyrotropic plasma distribution function ill t he solar wind.