Understanding the High-energy Hardening in Cosmic Ray Spectra

Abstract Recently, precise measurements on cosmic rays have been provided by various space experiments. A hardening at a few hundred GV has been observed in cosmic ray spectra both for primary and secondary particles. However, the reason for this hardening remains unclear. In this work, we employ the data measured by PAMELA, AMS02, ACE-CRIS and VOYAGER-1 to investigate this question. We study two different scenarios: the diffusion-reacceleration (DR) framework and the diffusion-convection (DC) framework. For each configuration, we investigate both the injection effects and the transport properties which may relate to the hardening. At the low-to-medium energy range, the diffusion slope δ L are estimated to be 0.41 to 0.48. It is found that the value of δ L estimated in the DR model is lower than that in the DC model. This infers that the reacceleration mechanism can result in steeper shapes in the (Li, Be, B)/C ratios than the convection process. At high energies, a variation in diffusion slope with Δδ ∼ −0.16 is favoured to explain the high-energy hardening structures observed in (Li, Be, B)/C ratios. Recent B/C data measured by DAMPE infers an even stronger high-energy diffusion break with Δδ ∼ −0.19.