Revisiting the hardening of the cosmic-ray energy spectrum at TeV energies

TL;DR

This paper investigates the hardening of the cosmic-ray energy spectrum at TeV energies, attributing it to nearby supernova remnants and extending analysis to heavier nuclei with detailed modeling and comparison to other models.

Contribution

It provides an improved, detailed model of cosmic-ray spectrum hardening due to nearby supernova remnants, including heavier nuclei and comprehensive comparisons with existing models.

Findings

Hardening explained by nearby supernova remnants effects.

Consistent treatment of background and source parameters.

Results align with some existing models and can be tested by future measurements.

Abstract

Measurements of cosmic rays by experiments such as ATIC, CREAM, and PAMELA indicate a hardening of the cosmic-ray energy spectrum at TeV energies. In our recent work (Thoudam & H\"orandel 2012a), we showed that the hardening can be due to the effect of nearby supernova remnants. We showed it for the case of proton and helium. In this paper, we present an improved and detailed version of our previous work, and extend our study to heavier cosmic-ray species such as boron, carbon, oxygen, and iron nuclei. Unlike our previous study, the present work involves a detailed calculation of the background cosmic rays and follows a consistent treatment of cosmic-ray source parameters between the background and the nearby components. Moreover, we also present a detailed comparison of our results on the secondary-to-primary ratios, secondary spectra, and the diffuse gamma-ray spectrum with the results expected from other existing models, which can be checked by future measurements at high energies.