Are EeV cosmic rays isotropic at intermediate scales?

TL;DR

This study investigates the anisotropy of cosmic rays in the 0.2-1.4 EeV energy range at intermediate scales, revealing significant deviations from isotropy and an energy-dependent evolution, which could inform understanding of galactic magnetic fields.

Contribution

It provides the first evidence of intermediate-scale anisotropy in cosmic rays within this energy range using Pierre Auger data, suggesting a potential transition from galactic to extragalactic origins.

Findings

Deviations from isotropy at >3 sigma significance.

Anisotropy evolves with energy.

Potential implications for galactic magnetic field structure.

Abstract

We study anisotropy of cosmic rays in the energy range 0.2-1.4 EeV at intermediate angular scales using the public data set of the Pierre Auger Observatory. At certain scales, the analysis reveals a number of deviations from the isotropic distribution with the statistical significance above three standard deviations. It also demonstrates that the anisotropy evolves with energy. If confirmed with the complete Auger or Telescope Array data sets, the result can shed new light on the structure of galactic magnetic fields and the problem of transition from galactic to extragalactic cosmic rays.