GeV-TeV cosmic-ray spectral anomaly as due to re-acceleration by weak shocks in the Galaxy

Abstract

Recent cosmic-ray measurements have found an anomaly in the cosmic-ray energy spectrum at GeV-TeV energies. Although the origin of the anomaly is not clearly understood, suggested explanations include effect of cosmic-ray source spectrum, propagation effects, and the effect of nearby sources. In this paper, we propose that the spectral anomaly might be an effect of re-acceleration of cosmic rays by weak shocks in the Galaxy. After acceleration by strong supernova remnant shock waves, cosmic rays undergo diffusive propagation through the Galaxy. During the propagation, cosmic rays may again encounter expanding supernova remnant shock waves, and get re-accelerated. As the probability of encountering old supernova remnants is expected to be larger than the younger ones due to their bigger sizes, re-acceleration is expected to be mainly due to weaker shocks. Since weaker shocks generate a softer particle spectrum, the resulting re-accelerated component will have a spectrum steeper than the initial cosmic-ray source spectrum produced by strong shocks. For a reasonable set of model parameters, it is shown that such re-accelerated component can dominate the GeV energy region while the non-reaccelerated component dominates at higher energies, explaining the observed GeV-TeV spectral anomaly.

12 pages, A&A accepted

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Cited by in corpus (22)

• Measurement of the cosmic ray helium energy spectrum from 70 GeV to 80 TeV with the DAMPE space mission
• Indications for a high-rigidity break in the cosmic-ray diffusion coefficient
• Observation of Spectral Structures in the Flux of Cosmic-Ray Protons from 50 GeV to 60 TeV with the Calorimetric Electron Telescope on the International Space Station
• Direct Measurement of the Cosmic-Ray Carbon and Oxygen Spectra from 10 GeV$/n$ to 2.2 TeV$/n$ with the Calorimetric Electron Telescope on the International Space Station
• Measurement of the Iron Spectrum in Cosmic Rays from 10 GeV$/n$ to 2.0 TeV$/n$ with the Calorimetric Electron Telescope on the International Space Station
• Direct Measurement of the Cosmic-Ray Helium Spectrum from 40 GeV to 250 TeV with the Calorimetric Electron Telescope on the International Space Station
• Cosmic Ray Acceleration by a Versatile Family of Galactic Wind Termination Shocks
• On the spectrum of stable secondary nuclei in cosmic rays
• Testing the universality of cosmic-ray nuclei from protons to oxygen with AMS-02
• Effects of reacceleration and source grammage on secondary cosmic rays spectra
• Systematic study of the uncertainties in fitting the cosmic positron data by AMS-02
• Direct Measurement of the Nickel Spectrum in Cosmic Rays in the Energy Range from 8.8 GeV/n to 240 GeV/n with CALET on the International Space Station
• Cosmic-Ray Lithium Production at the Nova Eruption Followed by a Type Ia Supernova
• A Three-component Model for Cosmic-ray Spectrum and Dipole Anisotropy
• R-process Element Cosmic Rays from Neutron Star Mergers
• A common origin of multi-messenger spectral anomaly of galactic cosmic rays
• Evidence of fresh cosmic ray in galactic plane based on DAMPE measurement of B/C and B/O ratios
• The Local Bubble in the interstellar medium and the origin of the low energy cosmic rays
• Potential of Constraining Propagation Parameters of Galactic Cosmic Rays with the High Energy cosmic-Radiation Detection facility onboard China's Space Station
• Transport parameters from AMS-02 F/Si data and fluorine source abundance
• A possible origin of gamma rays from the Fermi Bubbles
• Between the cosmic-ray `knee' and the `ankle': Contribution from star clusters