Super-knee cosmic rays from interacting supernovae

TL;DR

This paper proposes a model where supernovae interacting with dense circumstellar media accelerate nuclei to very high energies, potentially explaining the origin of super-knee cosmic rays and their composition observed by recent measurements.

Contribution

It introduces a comprehensive model including magnetic field amplification and composition-dependent acceleration, explaining super-knee cosmic-ray flux and composition from supernova interactions.

Findings

IIn supernovae can account for the dominant super-knee cosmic-ray flux.

The model aligns with recent LHAASO measurements above the CR knee.

It explains the heavy nuclear composition increase in this energy range.

Abstract

There is increasing evidence that, in the very late phase of stellar evolution before core collapse, massive stars have winds with large mass loss rates that give rise to a dense circumstellar medium (CSM) surrounding the progenitor star. After core collapse, a shock wave forms when the supernova ejecta interacts with this CSM. In such an interaction, the nuclei in the CSM can undergo diffusive shock acceleration and reach very high energies. We consider such a model, which includes magnetic field amplification from the non-resonant streaming instability, enhancement to the abundance of heavy-ions, and composition-dependent acceleration. Applying this to several supernova subclasses, we find that IIn supernovae can supply a dominant fraction of the observed super-knee cosmic-ray (CR) flux from $\sim{\rm few}\times10^{15}\,{\rm eV}$ to $\sim{\rm few}\times10^{17}\,{\rm eV}$ and is consistent with recent LHAASO measurements above the CR knee. This systematic model also explains the increasingly heavy nuclear composition in this energy range.