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. Nevertheless, high collisionality 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.

Evolution of the electron phase space of the two-stream and bump-on-tail instabilities in collisional plasma

“…Hao et al 32 showed that as the background plasma density increases, a current-driven instability is first attenuated and then enhanced by collisions, but the two-stream instability (TSI) is always damped by collisions. However, with a two-fluid collisional theory, Zhou and Bellan 33 recently found that in some situations, the TSI cannot be mitigated by collisions even if the collision frequency is larger than the growth rate of the instability.…”