Magnetic Field Amplification and Rapid Time Variations in SNR RX J1713.7-3946

TL;DR

This paper investigates how magnetic field amplification in supernova remnants, driven by cosmic ray acceleration, affects the maximum energy of protons, using Monte Carlo simulations to account for nonlinear effects.

Contribution

It introduces a steady-state Monte Carlo simulation to analyze the impact of nonlinear cosmic ray effects on magnetic field amplification and proton energy limits in SNRs.

Findings

Nonlinear effects reduce maximum proton energy compared to test-particle predictions.

Magnetic field amplification is linked to efficient cosmic ray production.

High magnetic fields inferred from electron radiation may overestimate proton energy limits.

Abstract

Evidence is accumulating suggesting that collisionless shocks in supernova remnants (SNRs) can amplify the interstellar magnetic field to hundreds of microgauss or even milli-gauss levels, as recently claimed for SNR RX J1713.7-3946. If these fields exist, they are almost certainly created by magnetic field amplification (MFA) associated with the efficient production of cosmic rays by diffusive shock acceleration (DSA) and their existence strengthens the case for SNRs being the primary source of galactic cosmic ray ions to the `knee' and beyond. However, the high magnetic field values in SNRs are obtained exclusively from the interpretation of observations of radiation from relativistic electrons and if MFA via nonlinear DSA produces these fields the magnetic field that determines the maximum ion energy will be substantially less than the field that determines the maximum electron energy. We use results of a steady-state Monte Carlo simulation to show how nonlinear effects from efficient cosmic ray production and MFA reduce the maximum energy of protons relative to what would be expected from test-particle acceleration.