Testing the consistency of proapgation between light and heavy cosmic ray nuclei

Abstract

One of the fundamental issues in cosmic ray physics is to explain the nature of cosmic ray acceleration and propagation mechanisms. Thanks to the precise cosmic ray data measured by recent space experiments, we are able to investigate the cosmic ray acceleration and propagation models more comprehensively and reliably. In this paper, we combine the secondary-to-primary ratios and the primary spectra measured by PAMELA, AMS02, ACE-CRIS and Voyager-1 to constrain the cosmic ray source and transport parameters. The study shows that the $Z>2$ data yield a medium-energy diffusion slope $\delta_{2}\sim\left(0.42, 0.48\right)$ and a high-energy slope $\delta_{3}\sim\left(0.22, 0.34\right)$. The $Z\leq2$ species obtain a looser constraint on $\delta_{2}\sim\left(0.38, 0.47\right)$, but a tighter constraint on $\delta_{3}\sim\left(0.21, 0.30\right)$. The overlaps infer that the heavy and light particles can give compatible results at medium to high energies. Besides, both the light and heavy nuclei indicate a consistent diffusion slope variation $\Delta\delta_{H}$ around $200\sim300$~GV. At low energies, significant disagreements exist between the heavy and light elements. The B/C ratio requires a much larger diffusion slope shift $\Delta\delta_{L}$ around 4 GV or a stronger \textit{Alfv$\acute{e}$n velocity} $v_{A}$ than the low-mass data. This indicates that the heavy and light particles may suffer different low-energy transport behaviors in Galaxy. However, better understanding on the consistency/inconsistency between the heavy and light cosmic rays relies on more precise cross-sections, better constraints on correlations in systematic errors of data, more accurate estimation on Galaxy halo size and more robust description for Solar modulation during the reversal period of HMF.