Kinetic plasma instabilities due to charge exchange and elastic collisions

Abstract

With numerical particle-in-cell simulations, we study kinetic plasma instabilities induced by collisions between plasma particles and neutral background in magnetized drifting plasmas. We consider the role of charge exchange as well as elastic collisions in the evolution of the system. Charge exchange collisions can give rise to velocity distributions in the form of loss- cone or ring shaped distributions that can become linearly unstable. Elastic collisions also lead to the instability, but in this case the principal mechanism may be attributed to the generalized two-stream instability. We investigate the growth rates and saturation levels for instabilities associated with these collisional processes, and find higher saturation levels and stronger fluctuations for the case with charge exchange collisions. Characteristics of the studied system are similar to the E- and F-regions of the Earth's ionosphere. Our results are relevant for explaining some of the low frequency oscillations observed in the lower parts of the Earth's ionosphere, and are also relevant for some laboratory experiments.