Physics of collisionless shocks - theory and simulation

TL;DR

This paper reviews the theory and simulation of collisionless shocks, focusing on their formation, types, and particle acceleration mechanisms in space and astrophysical contexts.

Contribution

It provides a comprehensive overview of electromagnetic and electrostatic collisionless shocks, highlighting recent theoretical insights and simulation results.

Findings

Electromagnetic shocks are mediated by Weibel instability.

Electrostatic shocks involve electron trapping and ion reflection.

Simulations support the mechanisms of particle acceleration in shocks.

Abstract

Collisionless shocks occur in various fields of physics. In the context of space and astrophysics they have been investigated for many decades. However, a thorough understanding of shock formation and particle acceleration is still missing. Collisionless shocks can be distinguished into electromagnetic and electrostatic shocks. Electromagnetic shocks are of importance mainly in astrophysical environments and they are mediated by the Weibel or filamentation instability. In such shocks, charged particles gain energy by diffusive shock acceleration. Electrostatic shocks are characterized by a strong electrostatic field, which leads to electron trapping. Ions are accelerated by reflection from the electrostatic potential. Shock formation and particle acceleration will be discussed in theory and simulations.