Particle acceleration in interstellar shocks

TL;DR

This review explains how interstellar shock waves, especially from supernova remnants, accelerate particles to high energies via the Fermi mechanism, with a focus on diffusive shock acceleration.

Contribution

It provides a detailed overview of the first order Fermi acceleration process in the context of supernova remnant shocks, highlighting its role in cosmic-ray production.

Findings

Supernova remnants are the primary sites for efficient particle acceleration.

Diffusive shock acceleration explains the origin of high-energy cosmic rays.

Strong shocks in supernova remnants are most effective in accelerating particles.

Abstract

This review presents the fundamentals of the particle acceleration processes active in interstellar medium (ISM), which are essentially based on the so-called Fermi mechanism theory. More specifically, the review presents here in more details the first order Fermi acceleration process -- also known as diffusive shock acceleration (DSA) mechanism. In this case, acceleration is induced by the interstellar (IS) shock waves. These IS shocks are mainly associated with emission nebulae (HII regions, planetary nebulae and supernova remnants). Among all types of emission nebulae, the strongest shocks are associated with supernova remnants (SNRs). Due to this fact they also provide the most efficient manner to accelerate ISM particles to become {high energy particles}, i.e.~cosmic-rays (CRs). The review therefore focuses on the particle acceleration at the strong shock waves of supernova remnants.