Cosmic ray spectral hardening due to dispersion of source injection spectra

TL;DR

This paper explains the observed spectral hardening in cosmic rays as a result of source spectral dispersion, supporting the supernova remnants origin hypothesis and offering an alternative explanation for ultra high energy CR features.

Contribution

It introduces a model where spectral dispersion of sources accounts for cosmic ray spectral hardening, aligning with gamma-ray observations of SNRs and explaining high-energy CR features.

Findings

Spectral hardening explained by source dispersion.

Injection parameters consistent with gamma-ray SNR observations.

Provides an alternative explanation for the ultra high energy CR spectrum features.

Abstract

The cosmic ray (CR) energy spectra measured with ATIC, CREAM and PAMELA showed that there is remarkable hardening for rigidity of several hundred GV. We propose that this hardening is due to the superposition of spectra from a population of sources, e.g., supernova remnants (SNRs), whose injection spectral indices have a dispersion. Adopting proper model parameters the observational data can be well explained. It is interesting that the injection source parameters are similar with that derived from gamma-ray observations of SNRs, which may support the SNR-origin of CRs. Furthermore this mechanism provides an alternative explanation of the "ankle-cutoff" structure of the ultra high energy CR spectra.