Understanding the spectral hardenings and radial distribution of Galactic cosmic rays and Fermi diffuse gamma-rays with spatially-dependent propagation

Abstract

Recent direct measurements of Galactic cosmic ray spectra by balloon/space-borne detectors reveal spectral hardenings of all major nucleus species at rigidities of a few hundred GV. The all-sky diffuse gamma-ray emissions measured by the Fermi Large Area Telescope also show spatial variations of the intensities and spectral indices of cosmic rays. These new observations challenge the traditional simple acceleration and/or propagation scenario of Galactic cosmic rays. In this work we propose a spatially-dependent diffusion scenario to explain all these phenomena. The diffusion coefficient is assumed to be anti-correlated with the source distribution, which is a natural expectation from the charged particle transportation in turbulent magnetic field. The spatially-dependent diffusion model also gives a lower level of anisotropies of cosmic rays, which are consistent with observations by underground muons and air shower experiments. The spectral variations of cosmic rays across the Galaxy can be properly reproduced by this model.

accepted by PRD

References in corpus (17)

• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• Discrepant hardening observed in cosmic-ray elemental spectra
• Spectral breaks as a signature of cosmic ray induced turbulence in the Galaxy
• Anisotropy and Corotation of Galactic Cosmic Rays
• Cosmic-ray propagation with DRAGON2: I. numerical solver and astrophysical ingredients
• Origin of the Cosmic Ray Spectral Hardening
• Measurement of boron and carbon fluxes in cosmic rays with the PAMELA experiment
• Indications for a high-rigidity break in the cosmic-ray diffusion coefficient
• A common solution to the cosmic ray anisotropy and gradient problems
• Northern sky Galactic Cosmic Ray anisotropy between 10-1000 TeV with the Tibet Air Shower Array
• ARGO-YBJ Observation of the Large-scale Anisotropy During the Solar Minimum between Cycles 23 and 24
• GeV-TeV cosmic-ray spectral anomaly as due to re-acceleration by weak shocks in the Galaxy
• A signature of anisotropic cosmic-ray transport in the gamma-ray sky
• The Connection Between the Positron Fraction Anomaly and the Spectral Features in Galactic Cosmic-Ray Hadrons
• Anomalous distributions of primary cosmic rays as evidence for time-dependent particle acceleration in Supernova remnants
• Cosmic Rays in a Galactic Breeze
• Molecular Clouds as the Origin of the Fermi Gamma-Ray GeV-Excess

Cited by in corpus (42)

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• Measurement of ultra-high-energy diffuse gamma-ray emission of the Galactic plane from 10 TeV to 1 PeV with LHAASO-KM2A
• Cosmic-ray transport from AMS-02 B/C data: benchmark models and interpretation
• Combined analysis of AMS-02 (Li,Be,B)/C, N/O, 3He, and 4He data
• Probing the "Sea" of Galactic Cosmic Rays with Fermi-LAT
• Indication of nearby source signatures of cosmic rays from energy spectra and anisotropies
• Revisiting Spatial-Dependent Propagation Model with Latest Observations of Cosmic Ray Nuclei
• Implications on cosmic ray injection and propagation parameters from Voyager/ACE/AMS-02 nucleus data
• Studies on cosmic ray nuclei with Voyager, ACE and AMS-02: I. local interstellar spectra and solar modulation
• Anisotropies of different mass compositions of cosmic rays
• Galactic diffuse gamma-ray emission from GeV to PeV energies in light of up-to-date cosmic ray measurements
• Nearby source interpretation of differences among light and medium composition spectra in cosmic rays
• Measurement of Very-high-energy Diffuse Gamma-ray Emissions from the Galactic Plane with LHAASO-WCDA
• Implications on the origin of cosmic rays in light of 10 TV spectral softenings
• Constraints on the spatially dependent cosmic-ray propagation model from Bayesian Analysis
• Interpretations of the cosmic ray secondary-to-primary ratios measured by DAMPE
• Probing the Cosmic Ray density in the inner Galaxy
• Geminga SNR: Possible candidate of local cosmic-ray factory
• Diffuse Ultra-High-Energy Gamma-Ray Emission From TeV Halos
• Prospects for detection of a Galactic diffuse neutrino flux
• Ultrahigh-energy diffuse gamma-ray emission from cosmic-ray interactions with medium surrounding acceleration sources
• Bayesian analysis of the hardening in AMS-02 nuclei spectra
• Statistically study the optimal local sources for cosmic ray nuclei and electron
• Prospects for a Multi-TeV Gamma-ray Sky Survey with the LHAASO Water Cherenkov Detector Array
• Test of the superdiffusion model in the interstellar medium around the Geminga pulsar
• Possible bump structure of cosmic ray electrons unveiled by AMS-02 data and its common origin along with the nuclei and positron
• Two-sided constraints on Lorentz Invariance violation from Tibet-AS$\gamma$ and LHAASO Very-High-Energy photon observations
• Evidence of fresh cosmic ray in galactic plane based on DAMPE measurement of B/C and B/O ratios
• Implications of a Possible Spectral Structure of Cosmic-ray Protons Unveiled by the DAMPE
• Some new hints on cosmic-ray propagation from AMS-02 nuclei spectra
• Origin of hardening in spectra of cosmic ray nuclei at a few hundred GeV using AMS-02 data
• Hybrid origins of the cosmic-ray nuclei spectral hardening at a few hundred GV
• Large-scale anisotropy of Galactic cosmic rays as a probe of local cosmic-ray propagation
• Injection spectra of different species of cosmic rays from AMS-02, ACE-CRIS and Voyager-1
• Galactic diffuse emission from radio to ultra-high-energy gamma rays in light of up-to-date cosmic ray measurements
• Potential of Constraining Propagation Parameters of Galactic Cosmic Rays with the High Energy cosmic-Radiation Detection facility onboard China's Space Station
• X-ray Binaries: a potential dominant contributor to the cosmic ray spectral knee structure
• A New Census of the Universe's Entropy
• Quantitative study of the hardening in the Alpha Magnetic Spectrometer nuclei spectra at a few hundred GV
• Constraining the position of the knee in the galactic cosmic ray spectrum with ultra-high-energy diffuse $\gamma$-rays
• Joint constraint on the propagation origin of the cosmic-ray spectral knee from energy spectrum and anisotropy observations
• Constraining the cosmic ray propagation halo thickness using Fermi-LAT observations of high-latitude clouds