Shock acceleration with oblique and turbulent magnetic fields

TL;DR

This paper explores how turbulence and magnetic field amplification caused by density inhomogeneities influence shock acceleration, affecting particle spectra and efficiency in astrophysical environments.

Contribution

It demonstrates that upstream density fluctuations and turbulent dynamo effects significantly impact shock acceleration processes and outcomes.

Findings

Magnetic field amplification enhances acceleration efficiency.

Shock obliquity variations affect particle energy gain.

Spectral indices depend on turbulence and magnetic field conditions.

Abstract

We investigate shock acceleration in a realistic astrophysical environment with density inhomogeneities. The turbulence induced by the interaction of the shock precursor with upstream density fluctuations amplifies both upstream and downstream magnetic fields via the turbulent dynamo. The dynamo-amplified turbulent magnetic fields (a) introduce variations of shock obliquities along the shock face, (b) enable energy gain through a combination of shock drift and diffusive processes, (c) give rise to various spectral indices of accelerated particles, (d) regulate the diffusion of particles both parallel and perpendicular to the magnetic field, and (e) increase the shock acceleration efficiency. Our results demonstrate that upstream density inhomogeneities and dynamo amplification of magnetic fields play an important role in shock acceleration, and thus shock acceleration depends on the condition of the ambient interstellar environment. The implications on understanding radio spectra of supernova remnants are also discussed.