Origin of hardening in spectra of cosmic ray nuclei at a few hundred GeV using AMS-02 data

TL;DR

This paper analyzes cosmic ray nuclei spectra from AMS-02 data, finding that the spectral hardening at a few hundred GV is best explained by the superposition of different sources rather than primary acceleration or propagation alone.

Contribution

It demonstrates that the superposition of various sources can naturally explain the spectral features observed in cosmic ray nuclei spectra, challenging simpler models.

Findings

Spectral break and index differences vary among nuclei

Simple primary or propagation models cannot reproduce the data

Superposition of sources provides a consistent explanation

Abstract

Many experiments have confirmed the spectral hardening in a few hundred GV of cosmic ray (CR) nuclei spectra, and 3 different origins have been proposed: the primary source acceleration, the propagation, and the superposition of different kinds of sources. In this work, the break power law has been employed to fit each of the AMS-02 nuclei spectra directly when the rigidity greater than 45 GV. The fitting results of the break rigidity and the spectral index differences less and greater than the break rigidity show complicated relationships among different nuclei species, which could not been reproduced naturally by a simple primary source scenario or a propagation scenario. However, with a natural and simple assumption, the superposition of different kinds of sources could have the potential to explain the fitting results successfully. CR nuclei spectra from one single experiment in future (such as DAMPE) will provide us the opportunity to do cross checks and reveal the properties of the different kinds of sources.