Nearby supernova remnants and the cosmic-ray spectral hardening at high energies

TL;DR

This paper proposes that nearby supernova remnants significantly influence the observed spectral hardening of cosmic rays at high energies, explaining recent experimental data through a model of rigidity-dependent cosmic-ray escape.

Contribution

It introduces a model where nearby supernova remnants cause the spectral hardening, aligning with observations and explaining species-dependent energy differences.

Findings

Nearby remnants can cause spectral hardening in cosmic rays.

The model explains the lower energy hardening of helium compared to protons.

Spectral hardening does not extend beyond 20-30 TeV energies.

Abstract

Recent measurements of cosmic-ray spectra of several individual nuclear species by the CREAM, TRACER, and ATIC experiments indicate a change in the spectral index of the power laws at TeV energies. Possible explanations among others include non linear diffusive shock acceleration of cosmic-rays, different cosmic-ray propagation properties at higher and lower energies in the Galaxy and the presence of nearby sources. In this paper, we show that if supernova remnants are the main sources of cosmic rays in our Galaxy, the effect of the nearby remnants can be responsible for the observed spectral changes. Using a rigidity dependent escape of cosmic-rays from the supernova remnants, we explain the apparent observed property that the hardening of the helium spectrum occurs at relatively lower energies as compared to the protons and also that the spectral hardening does not persist beyond $\sim (20-30)$ TeV energies.