Anisotropic Temperature Plasma Instabilities

An anisotropic plasma exhibits a transverse instability due to the mutual attraction of the microscopic current elements. A detailed study is made of this instability in an electron-ion plasma without any external magnetic field. The system is characterized by a temperature tensor and described by a quasi-Maxwellian distribution function. The dielectric tensor for such a system is calculated and then the dispersion relation is considered. It is found that there are two unstable modes: (i) a purely transverse mode and (ii) a coupled or transverse-longitudinal mode. The latter separates into two branches: (a) the first is an essentially unstable quasitransverse mode, (b) the second is the quasi-longitudinal ion acoustic mode driven into instability through its interaction with the quasitransverse mode. Growth rate, k and angular dependence, domain of instability, and polarization are analyzed in detail.