The large-scale anisotropy and flux (de-)magnification of ultra-high-energy cosmic rays in the Galactic magnetic field

TL;DR

This study models how the Galactic magnetic field influences the observed distribution and anisotropy of ultra-high-energy cosmic rays, revealing significant effects on flux magnification and source visibility.

Contribution

Introduces new Galactic magnetic field models that alter predictions of UHECR arrival directions and anisotropies, improving understanding of cosmic ray propagation.

Findings

The dipole amplitude of UHECR flux is significantly reduced with new GMF models.

Flux demagnification affects the visibility of certain cosmic ray sources.

The anisotropy sensitivity to GMF models can probe source distribution and magnetic fields.

Abstract

We calculate the arrival direction distribution of ultra-high-energy cosmic rays (UHECRs) with a new suite of models of the Galactic magnetic field (GMF), assuming sources follow the large-scale structure of the Universe. Compared to previous GMF models, the amplitude of the dipole component of the UHECR arrival flux is significantly reduced. We find that the reduction is due to the accidentally coinciding position of the peak of the extragalactic UHECR flux and the boundary of strong flux demagnification due to the GMF toward the central region of the Galaxy. This serendipitous sensitivity of UHECR anisotropies to the GMF model will be a powerful probe of the source distribution as well as Galactic and extragalactic magnetic fields. Demagnification by the GMF also impacts visibility of some popular source candidates.