Cosmic-ray escape from supernova remnants

Abstract

Supernova remnants are known to accelerate cosmic rays for their non-thermal emission of radio waves, X-rays, and gamma-rays. Although there are many models for the acceleration of cosmic rays in supernova remnants, the escape of cosmic rays from this sources is yet understudied. We use our time-dependent acceleration code to study the acceleration of cosmic rays and their escape from supernova remnants. We carry out spherically symmetric 1-D simulations in which we simultaneously solve the transport equations for cosmic rays, magnetic turbulence, and the hydrodynamical flow of the thermal plasma. The transport equations for cosmic-rays and magnetic turbulence are coupled via the cosmic-ray gradient and the spatial diffusion coefficient of the cosmic rays, while the cosmic-ray feedback onto the shock structure is ignored. Our simulations span 100000 years, thus covering the free-expansion, the Sedov-Taylor and the radiative phase of the remnant evolution. During this time we keep all cosmic rays in the simulation domain. At later stages of the evolution cosmic-rays in a wide energy-band are able to escape the remnant. We compare the results with common analytic estimates for the escape-spectra.