Interactions of UHE cosmic ray nuclei with radiation during acceleration: consequences on the spectrum and composition

TL;DR

This study examines how interactions with photon backgrounds affect the acceleration, spectrum, and composition of ultra-high-energy cosmic-ray nuclei and protons, revealing different dominant processes depending on acceleration conditions.

Contribution

It provides a detailed analysis of how interaction processes influence cosmic-ray acceleration and composition, considering various astrophysical parameters and constraints.

Findings

Protons reach higher energies in interaction-limited scenarios.

Nuclei attain higher energies in confinement-limited scenarios.

Results inform the nature of astrophysical accelerators and cosmic-ray observations.

Abstract

In this paper, we study the diffusive shock acceleration of cosmic-ray protons and nuclei, taking into account all the relevant interaction processes with photon backgrounds. We investigate how the competition between protons and nuclei is modified by the acceleration parameters such as the acceleration rate, its rigidity dependence, the photon density and the confinement capability of the sources. We find that in the case of interaction-limited acceleration processes protons are likely to be accelerated to higher energies than nuclei, whereas for confinement-limited acceleration nuclei are accelerated to higher energies than protons. Finally, we discuss our results in the context of possible astrophysical accelerators, and in the light of recent cosmic-ray data.