Instability of interpenetrating plasma flows bounded by a magnetic field

A linear stage of two-stream instability of interpenetrating and collisionless plasmoids containing no magnetic field and sharply limited by an external longitudinal magnetic field is considered. Both kinetic and hydrodynamic models of instability are analysed in the supposition that electrons are cold. Conditions for instability development, results of numerical calculations of increments and mode images are given. It is shown that instability is aperiodic and it has a long wave limit (and in kinetics - short wave), characteristic increments of the order of vT/a, where vT is the thermal velocity of ions, and a is the lateral size of plasmoids