Unstable Plasma Modes Amplified by Cosmic Rays in the Upstream of Collisionless Shock

Abstract

Abstract—Nonequilibrium distributions of cosmic rays accelerated by the Fermi mechanism are formed by multiple interactions with magnetic fluctuations in the upstream region of a collisionless shock. The shock ram pressure is transferred to accelerated cosmic rays, which may in turn amplify the magnetic turbulence. A short-wave plasma instability induced in the upstream region of a collisionless shock caused by the interaction between cosmic rays and the background plasma is discussed.