Spectrum of Cosmic Rays Produced in Supernova Remnants

Abstract

Nonlinear kinetic theory of cosmic-ray (CR) acceleration in supernova remnants is employed to calculate CR spectra. The magnetic field in SNRs is assumed to be significantly amplified by the efficiently accelerating nuclear CR component. It is shown that the calculated CR spectra agree in a satisfactory way with the existing measurements up to the energy 1017 eV. The power-law spectrum of protons extends up to the energy 3 × 1015 eV with a subsequent exponential cutoff. It gives a natural explanation for the observed knee in the Galactic CR spectrum. The maximum energy of the accelerated nuclei is proportional to their charge number Z. Therefore, the break in the Galactic CR spectrum is the result of the contribution of progressively heavier species in the overall CR spectrum so that at 1017 eV the CR spectrum is dominated by iron group nuclei. It is shown that this component plus a suitably chosen extragalactic CR component can give a consistent description for the entire Galactic CR spectrum.