Kelvin-Helmholtz Instability in an Anisotropic Plasma

The instability arising due to a tangential discontinuity of velocity in an unbounded, anisotropic plasma subject to a uniform magnetic field is investigated using the Chew, Goldberger, and Low approximation. Formal conditions for monotonic instability and the growing-wave instability are written. It is found that monotonic instability is possible, for a range of relative speeds, only if the plasma is characterized by the condition 2p∥ > p⊥. For 2p∥ < p⊥ the configuration is, however, overstable for relative speeds less than a certain critical value. The bearing of the results on the stability of the magnetospheric boundary and the coronal streamers is discussed and it is suggested that a possible fine structure in the solar wind may satisfy the requirement for instability and thus produce irregularities of plasma properties and the magnetic field in the medium.