Particle acceleration by supernova shocks and spallogenic nucleosynthesis of light elements

TL;DR

This review reassesses supernova remnants as sources of galactic cosmic rays, explores light element nucleosynthesis by cosmic rays, and evaluates models explaining observed Be abundances, favoring the superbubble model.

Contribution

It critically evaluates existing cosmic ray models for light element synthesis and advocates for the superbubble model as the most consistent with observations.

Findings

Supernova remnant paradigm is challenged by recent Voyager 1 data.

Standard models struggle to explain Be abundances in low-metallicity stars.

Superbubble model offers the most satisfactory explanation for light element evolution.

Abstract

In this review, we first reassess the supernova remnant paradigm for the origin of galactic cosmic rays in the light of recent cosmic-ray data acquired by the Voyager 1 spacecraft. We then describe the theory of light element nucleosynthesis by nuclear interaction of cosmic rays with the interstellar medium and outline the problem of explaining the measured Be abundances in old halo stars of low metallicity with the standard model for the galactic cosmic ray origin. We then discuss the various cosmic ray models proposed in the literature to account for the measured evolution of the light elements in the Milky Way, and point out the difficulties that they all encounter. Amongst all possibilities, it seems to us that the superbubble model provides the most satisfactory explanation for these observations.