A Three-component Model for Cosmic-ray Spectrum and Dipole Anisotropy

Abstract

Using a three-component, multi-scale diffusion model, we show that the cosmic-ray (CR) proton and helium spectra and the dipole anisotropy can be explained with reasonable parameters. The model includes a nearby source associated with the supernova remnant (SNR) that gave rise to the Geminga pulsar, a source at the Galactic center, and a component associated with the Galactic disk. The CR flux below TeV is dominated by the disk component. The center source with a continuous injection of CRs starting about 18 Myr ago is needed to explain the anisotropy above 100 TeV. With the assumption of universal CR spectra injected by all SNRs, the nearby source can produce a TeV spectral bump observed at Earth via slow diffusion across the interstellar magnetic field, which needs to have an angle $\theta \approx 5^{\circ }$ between the field line and the line of sight toward the source, and have weak magnetic turbulence with the Alfvén Mach number $M_{\text{A}}\approx 0.1$. Considering the modulation of the Galactic-scale anisotropy by this magnetic field, in a quasi-local approach the field may be directed at a right ascension about $-90^{\circ }$ and a declination about $-7.4^{\circ }$ in the equatorial coordinate system.

Submitted to MNRAS

References in corpus (15)

• 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
• Spectral breaks as a signature of cosmic ray induced turbulence in the Galaxy
• Measurements of cosmic-ray secondary nuclei at high energies with the first flight of the CREAM balloon-borne experiment
• Origin of the Cosmic Ray Spectral Hardening
• Measurement of the Anisotropy of Cosmic Ray Arrival Directions with IceCube
• Evolution of the cosmic ray anisotropy above 10^{14} eV
• Observation of Cosmic Ray Anisotropy with the IceTop Air Shower Array
• 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
• The Milagro anticenter hot spots: cosmic rays from the Geminga supernova ?
• Fermi-LAT Observations of High- and Intermediate-Velocity Clouds: Tracing Cosmic Rays in the Halo of the Milky Way
• Anomalous distributions of primary cosmic rays as evidence for time-dependent particle acceleration in Supernova remnants
• Cosmic Rays in a Galactic Breeze