Confinement of relativistic particles in the vicinity of accelerators: a key for understanding the anomalies in secondary cosmic rays

TL;DR

This paper proposes that cosmic rays spend significant time near their sources, propagating more slowly in these regions, which explains recent anomalies in secondary cosmic ray measurements within the standard Galactic CR paradigm.

Contribution

It introduces a model where cosmic rays are confined near their sources, accounting for anomalies without abandoning the standard CR paradigm.

Findings

Explains B/C ratio measurements by DAMPE.

Accounts for diffuse gamma rays observed by LHAASO.

Uses minimal model parameters for consistency.

Abstract

Recent cosmic ray (CR) measurements have revealed unexpected anomalies in secondary CRs, namely deviations from the predictions of the so-called standard Galactic CR paradigm regarding the composition and energy spectra of the products of interactions of primary (accelerated) CRs with interstellar gas: (i) antiparticles (positrons and antiprotons), (ii) light elements of the (Li, Be, B) group, and (iii) diffuse gamma rays. We argue that the new measurements can still be explained within the standard CR paradigm but with an additional assumption that CRs spend a significant part of their lifetime near their formation sites. The latter can be realized if CRs propagate more slowly in these localized regions than in the interstellar medium (ISM). Postulating that CRs accumulate on average energy-independent "grammage" of $0.7 \ \rm g/cm^2$ near the major contributors to galactic CRs, one can explain self-consistently the new measurements of the B/C ratio by DAMPE and the diffuse ultra-high-energy gamma-rays by LHAASO, involving a minimal number of model parameters: the energy-dependent "grammage" in the interstellar medium $\rm \lambda \approx 8 (E/10 \ GeV)^{-0.55}~\rm g/cm^{2}$ and the average CR acceleration (sourcee) spectrum, $\rm Q(E) \propto E^{-2.3}$.