DAMPE proton spectrum indicates a slow-diffusion zone in the nearby ISM

Abstract

The hardening and softening features in the DAMPE proton spectrum are very likely to be originated from a nearby supernova remnant (SNR). The proton spectrum from the nearby SNR is required to be very hard below $\approx 10$ TeV. To reproduce this feature, we illustrate that anomalously slow-diffusion zone for cosmic rays (CRs) must be existed in the local interstellar medium (ISM) after also taking the dipole anisotropy of CRs into account. Assuming that the diffusion coefficient is homogeneous in the nearby ISM, we show that the diffusion coefficient is constrained to the magnitude of $10^{26}$ cm${}^2$ s${}^{-1}$ when normalized to 1 GeV, which is about 100 times smaller than the average value in the Galaxy. We further discuss the spatial distribution of the slow diffusion and find two distinct possibilities. In one case, the SNR is several hundred of parsecs away from the solar system, meanwhile both the SNR and the solar system are required to be included in a large slow-diffusion zone. The homogeneous diffusion belongs to this case. In the other case, the SNR is very close with a distance of $\sim 50$ pc and the slow-diffusion zone is only limited around the SNR. The required diffusion coefficient is further smaller in the latter case. This work provides a new way of studying the CR diffusion in the local ISM.

8 pages, 5 figures, 1 table

References in corpus (5)

• Extended gamma-ray sources around pulsars constrain the origin of the positron flux at Earth
• Measurement of the cosmic-ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite
• Northern sky Galactic Cosmic Ray anisotropy between 10-1000 TeV with the Tibet Air Shower Array
• Plasma turbulence in the interstellar medium
• Fermi-LAT Observations of High- and Intermediate-Velocity Clouds: Tracing Cosmic Rays in the Halo of the Milky Way

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• Implications of a Possible Spectral Structure of Cosmic-ray Protons Unveiled by the DAMPE
• Explanation of nearby SNRs for primary electron excess and proton spectral bump
• Transport parameters from AMS-02 F/Si data and fluorine source abundance
• Deciphering the spectral bumps of Galactic cosmic rays through gamma-ray observations of nearby molecular clouds