Proton-cyclotron and firehose instabilities in inhomogeneous plasmas

Abstract

By combining the kinetic-fluid model for macroscopic quantities and quasilinear kinetic theory for microscopic plasma instabilities, the present paper investigates quasi-stationary spatial distribution and characteristics of the electromagnetic proton-cyclotron and parallel firehose instabilities in inhomogeneous plasma, as well as their influence on macroscopic variables. The present paper considers diverging magnetic field along a flux tube, as well as the associated density model, with various source region boundary conditions, in order to investigate the spatial locations at which the excitation, saturation, and damping of the proton-cyclotron and firehose instabilities occur in a medium with field-aligned inhomogeneity. Potential application may be on the solar wind model in which the temperature anisotropy threshold rigorously follows as a result of quasilinear relaxation process. Key Points Quasilinear theory of EMCI and firehose instabilities in inhomogeneous plasmaDescribes solar wind from source region to near EarthAnisotropy-beta boundary naturally explained