Structure of Cosmic Ray-modified Perpendicular Shocks

TL;DR

This paper explores how cosmic rays modify perpendicular shocks through charge non-neutrality, turbulence generation, and particle acceleration, providing a kinetic perspective on shock-cosmic ray interactions.

Contribution

It presents a kinetic analysis of cosmic ray effects on perpendicular shocks, highlighting turbulence and electron heating mechanisms.

Findings

Cosmic ray diffusion induces charge non-neutrality.

Turbulence from instabilities enables Fermi acceleration.

Electrons can be heated in the cosmic ray precursor.

Abstract

Kinetic diffusion of cosmic rays ahead of perpendicular shocks induces charge non-neutrality, which is mostly, yet not completely, screened by the bulk plasma via polarization drift current. Hydrodynamic shear instabilities as well as modified Buneman instability of the polarization current generate the turbulence necessary for a Fermi-type acceleration. Thus, similar to the case of parallel shocks, in perpendicular shocks the diffusing cosmic rays generate unstable plasma currents that in turn excite turbulence. This allows a self-consistent evolution of a shock-cosmic rays system. In the kinetic regime of the modified Buneman instability, electrons may be heated in the cosmic ray precursor.