Cosmic ray spectral hardening due to dispersion in the source injection spectra

TL;DR

This paper explains the observed spectral hardening in cosmic rays as a result of dispersion in source injection spectra, supporting supernova remnants as their origin and potentially explaining features in ultra high energy cosmic rays.

Contribution

It introduces a dispersion-based model to reproduce cosmic ray spectral features, linking source variability to observed spectral hardening and the ankle in ultra high energy cosmic rays.

Findings

Reproduces cosmic ray spectra using source dispersion parameters.

Supports supernova remnants as primary cosmic ray sources.

Provides a potential explanation for the ultra high energy CR ankle.

Abstract

Recent cosmic ray (CR) experiments discovered that the CR spectra experience a remarkable hardening for rigidity above several hundred GV. We propose that this is caused by the superposition of the CR energy spectra of many sources that have a dispersion in the injection spectral indices. Adopting similar parameters as those of supernova remnants derived from the Fermi $\gamma$-ray observations, we can reproduce the observational CR spectra of different species well. This may be interpreted as evidence to support the supernova remnant origin of CRs below the knee. We further propose that the same mechanism may explain the "ankle" of the ultra high energy CR spectrum.