Nearby SNR: a possible common origin to multi-messenger anomalies in spectra, ratios and anisotropy of cosmic rays

TL;DR

This paper proposes that nearby supernova remnants combined with spatially-dependent cosmic ray propagation can explain multiple observed cosmic ray anomalies, including spectral hardening, ratios, and anisotropy, in a unified physical scenario.

Contribution

It introduces a model incorporating a nearby SNR and dense molecular cloud interactions to simultaneously explain various cosmic ray anomalies and spectral features.

Findings

Reproduces spectral hardening and ratios of cosmic rays.

Predicts spectral break-offs at specific energies for different particles.

Provides testable predictions for future space experiments like HERD.

Abstract

The multi-messenger anomalies, including spectral hardening or excess for nuclei, leptons, ratios of $\bar p/p$ and B/C, and anisotropic reversal, were observed in past years. AMS-02 experiment also revealed different spectral break for positron and electron at 284 GeV and beyond TeV respectively. It is natural to ask whether all those anomalies originate from one unified physical scenario. In this work, the spatially-dependent propagation (SDP) with a nearby SNR source is adopted to reproduce above mentioned anomalies. There possibly exists dense molecular cloud(DMC) around SNRs and the secondary particles can be produced by pp-collision or fragmentation between the accelerated primary cosmic rays and DMC. As a result, the spectral hardening for primary, secondary particles and ratios of $B/C$ and $\bar p/p$ can be well reproduced. Due to the energy loss at source age of 330 kyrs, the characteristic spectral break-off for primary electron is at about 1 TeV hinted from the measurements. The secondary positron and electron from charged pion take up $5\%$ energy from their mother particles, so the positron spectrum has a cut-off at $\sim$250 GeV. Therefore, the different spectral break for positron and electron together with other anomalies can be fulfilled in this unified physical scenario. More interesting is that we also obtain the featured structures as spectral break-off at 5 TV for secondary particles of Li, Be, B, which can be served to verify our model. We hope that those tagged structures can be observed by the new generation of space-borne experiment HERD in future.