Hybrid origins of the cosmic-ray nuclei spectral hardening at a few hundred GV

Abstract

Many experiments have confirmed the spectral hardening at a few hundred GV of cosmic-ray (CR) nuclei spectra, and three general different origins have been proposed: the primary source acceleration, the propagation, and the superposition of different kinds of sources. The AMS-02 CR nuclei spectra of He, C, N, O, Ne, Mg, Si, and B (which including B and its dominating parents species) are collected to study the necessity of employing a break in diffusion coefficient and independent breaks in primary source injection spectra to reproduce the spectral hardening at a few hundred GV. For comparison, three different schemes are introduced to do the global fitting. The fitting results show that both the break in diffusion coefficient and the independent breaks in primary source injection spectra are needed, which are corresponding to the spatial dependent propagation and the superposition of different kinds of sources, respectively. Consequently, the nuclei spectral hardening in a few hundred GV should have hybrid origins. Moreover, the CR spectral indices of He and Ne show large deviations to other species in low-rigidity region, which indicates their different CR origins.