Large-scale anisotropy of Galactic cosmic rays as a probe of local cosmic-ray propagation

TL;DR

This paper investigates how local magnetic fields and anisotropic diffusion influence large-scale cosmic ray anisotropy, providing insights into cosmic ray origins and propagation, especially below 100 TeV.

Contribution

It introduces a unified model linking cosmic ray spectra and anisotropy, emphasizing the role of local magnetic fields and anisotropic diffusion in shaping observations.

Findings

Dipole anisotropy aligns with local magnetic field when perpendicular diffusion is small.

The phase of anisotropy above 100 TeV depends on local diffusion evolution.

Current measurements above 100 TeV are limited, highlighting the need for more data.

Abstract

Recent studies have shown that the anisotropy is of great value to decipher cosmic rays' origin and propagation. We have built an unified scenario to describe the observations of the energy spectra and the large-scale anisotropy and called attention to their synchronously evolution with energy. In this work, the impact of of the local regular magnetic field (LRMF) and corresponding anisotropic diffusion on large-scale anisotropy have been investigated. When the perpendicular diffusion coefficient is much smaller than the parallel one, the dipole anisotropy points to the LRMF and the observational phase below $100$ TeV could be reproduced. Moreover we find that the dipole phase above $100$ TeV strongly depends on the evolution of local diffusion. But the current measurements at that energy are still scarce. We suggest that more precise measurements at that energy could be carried out to unveil the local diffusion and further the local turbulence.