Cosmic ray acceleration at oblique shocks

TL;DR

This paper investigates how particle acceleration at oblique shocks in supernova remnants deviates from traditional models, revealing the importance of anisotropies in shaping the energy spectra.

Contribution

It demonstrates the breakdown of the diffusion approximation at oblique shocks and highlights the role of higher order anisotropies in spectral index variations.

Findings

Diffusion approximation fails at typical supernova remnant shock velocities.

Anisotropies influence spectral index, flattening at quasi-parallel shocks.

Spectral indices observed align with anisotropic theoretical predictions.

Abstract

We show that the diffusion approximation breaks down for particle acceleration at oblique shocks with velocities typical of young supernova remnants. Higher order anisotropies flatten the spectral index at quasi-parallel shocks and steepen the spectral index at quasi-perpendicular shocks. We compare the theory with observed spectral indices.