Cosmic ray acceleration in young supernova remnants

TL;DR

This paper explores how magnetic field amplification driven by cosmic ray escape currents in supernova remnants depends on shock velocity and environment, identifying conditions that favor acceleration to PeV energies.

Contribution

It introduces a model linking cosmic ray escape currents to magnetic field amplification and identifies young dense remnants as prime accelerators to PeV energies.

Findings

Young remnants in dense environments can accelerate cosmic rays to ~PeV energies.

Magnetic field amplification is quenched in about 1000 years for typical conditions.

SN1006 is marginally capable of accelerating cosmic rays to high energies.

Abstract

We investigate the appearance of magnetic field amplification resulting from a cosmic ray escape current in the context of supernova remnant shock waves. The current is inversely proportional to the maximum energy of cosmic rays, and is a strong function of the shock velocity. Depending on the evolution of the shock wave, which is drastically different for different circumstellar environments, the maximum energy of cosmic rays as required to generate enough current to trigger the non-resonant hybrid instability that confines the cosmic rays follows a different evolution and reaches different values. We find that the best candidates to accelerate cosmic rays to ~few PeV energies are young remnants in a dense environment, such as a red supergiant wind, as may be applicable to Cassiopeia A. We also find that for a typical background magnetic field strength of 5 microG the instability is quenched in about 1000 years, making SN1006 just at the border of candidates for cosmic ray acceleration to high energies.