Spectrum of cosmic rays, produced in supernova remnants

TL;DR

This paper uses nonlinear kinetic theory to model cosmic ray spectra from supernova remnants, explaining the observed knee in the Galactic cosmic ray spectrum and the dominance of heavy nuclei at high energies.

Contribution

It provides a detailed theoretical model linking supernova remnant acceleration processes to the observed cosmic ray spectrum features, including the knee and composition changes.

Findings

CR spectra agree with measurements up to 10^{17} eV

Proton spectrum extends to 3×10^{15} eV with cutoff

Heavy nuclei dominate above 10^{17} eV

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 $10^{17}$ eV. The power law spectrum of protons extends up to the energy $3\times 10^{15}$ 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 $10^{17}$ 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.