Nearby SNR: A Possible Common Origin of Multi-messenger Anomalies in the Spectra, Ratios, and Anisotropy of Cosmic Rays

Abstract

Multi-messenger anomalies, including spectral hardening or excess of nuclei, leptons, ratios of $\bar{p}/p$ and B/C, and anisotropic reversal, have been observed in past years. The AMS-02 experiment also revealed different spectral breaks for positrons and electrons at 284 GeV and beyond tera electron volts, 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 supernova remnant (SNR) source is adopted to reproduce the abovementioned anomalies. There possibly exists a 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 and secondary particles and ratios of B/C and $\bar{p}/p$ can be well reproduced. Due to the energy loss at the source age of 330 kyr, the characteristic spectral break-off for a primary electron is at about 1 TeV as hinted at by the measurements. The secondary positrons and electrons from charged pion take up 5% of energy from their mother particles, so the positron spectrum has a break-off at ∼250 GeV. Therefore, the different spectral breaks for positrons and electrons 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-offs at 5 TeV for secondary particles of Li, Be, and B, which can be used to verify our model. We hope that those tagged structures can be observed by the new generation of spaceborne experiment HERD in the future.

Keywords

• Cosmic ray sources
• Secondary cosmic rays
• Cosmic anisotropy
• Supernova remnants