Cosmic ray acceleration and escape from supernova remnants

TL;DR

This paper models how cosmic rays are accelerated and escape from supernova remnants, emphasizing the role of magnetic field amplification and predicting the maximum energies and spectra of escaping cosmic rays.

Contribution

It introduces a charge-based model for CR escape that predicts maximum energies and spectra, providing insights into the conditions needed for CR acceleration to PeV energies.

Findings

Historical SNRs may not currently accelerate CR to the knee.

Magnetic field amplification is crucial for reaching PeV energies.

The model predicts the energy spectrum of escaping cosmic rays.

Abstract

Galactic cosmic ray (CR) acceleration to the knee in the spectrum at a few PeV is only possible if the magnetic field ahead of a supernova remnant (SNR) shock is strongly amplified by CR escaping the SNR. A model formulated in terms of the electric charge carried by escaping CR predicts the maximum CR energy and the energy spectrum of CR released into the surrounding medium. We find that historical SNR such as Cas A, Tycho and Kepler may be expanding too slowly to accelerate CR to the knee at the present time.