Microphysics of Cosmic Plasmas: Hierarchies of Plasma Instabilities from MHD to Kinetic

Abstract

In this article, we discuss the idea of a hierarchy of instabilities that can rapidly couple the disparate scales of a turbulent plasma system. First, at the largest scale of the system, L, current carrying flux ropes can undergo a kink instability. Second, a kink instability in adjacent flux ropes can rapidly bring together bundles of magnetic flux and drive reconnection, introducing a new scale of the current sheet width, ℓ, perhaps several ion inertial lengths (δi) across. Finally, intense current sheets driven by reconnection electric fields can destabilize kinetic waves such as ion cyclotron waves as long as the drift speed of the electrons is large compared to the ion thermal speed, vD≫vi. Instabilities such as these can couple MHD scales to kinetic scales, as small as the proton Larmor radius, ρi.