On the escape and propagation of high-energy protons near young supernova remnants

Abstract

The escape and propagation of high-energy protons near young supernova remnants (SNRs) are investigated in the frame of non-linear diffusive shock acceleration (NLDSA) model by using two methods. In the first method, the particle diffusion is assumed to be different inside and outside the absorbing boundary of the particles accelerated in the SNR shock, and the proton spectra at a given distance of the outer region and corresponding pi(0) decay gamma-ray spectra can be calculated if a molecular cloud is assumed to be at the distance. In the second method, the total spectrum of high-energy protons escaping from an absorbing boundary during the SNR evolution time is treated as injection rate of the protons and the proton spectrum is calculated in the accumulative diffusion model. Our results show that (1) the spectrum of high-energy protons escaping from a young SNR does not have a power-law form and the protons concentrate on high-energy region and (2) the escaping proton spectra and corresponding pi(0) decay gamma-ray spectra predicted in both methods are different, indicating that the second method overestimates the propagation effect. We may conclude that the first method is a more realistic description of the escape and propagation of high-energy protons near SNRs.