Two-stream instability with a growth rate insensitive to collisions in a dissipative plasma jet

Abstract

The two-stream instability (Buneman instability) is traditionally derived as a collisionless instability with the presumption that collisions inhibit this instability. We show here via a combination of a collisional two-fluid model and associated experimental observations made in the Caltech plasma jet experiment, that in fact, a low frequency mode of the two-stream instability is indifferent to collisions. Despite the collision frequency greatly exceeding the growth rate of the instability, the instability can still cause an exponential growth of electron velocity and a rapid depletion of particle density. High collisionality nevertheless has an important effect as it enables the development of a double layer when the cross-section of the plasma jet is constricted by a kink-instigated Rayleigh-Taylor instability.