Propagation of Ultrahigh Energy Nuclei in the Magnetic Field of our Galaxy

TL;DR

This paper uses detailed simulations to study how ultra-high energy heavy nuclei propagate through the Galactic Magnetic Field, revealing complex deflections and flux magnifications that challenge cosmic ray source identification.

Contribution

It provides the first comprehensive simulation-based analysis of UHE heavy nuclei propagation considering recent GMF models, highlighting the effects on source detection and sky images.

Findings

No direct correlation between arrival directions and sources for UHE heavy nuclei.

Magnetic lensing can significantly demagnify source fluxes, making some sources undetectable.

Sources in about 20% of the sky may be too demagnified for detection.

Abstract

In this work, we present detailed simulations for propagation of ultra-high energy (UHE) heavy nuclei, with E > 60 EeV, within recent Galactic Magnetic Field (GMF) models. We investigate the impacts of the regular and turbulent components of the GMF. We show that with UHE heavy nuclei, there is no one-to-one correspondence between the arrival directions of cosmic rays (CR) measured at Earth and the direction of their extragalactic sources. Sources can have several distorted images on the sky. We compute images of galaxy clusters and of the supergalactic plane in recent GMF models and show the challenges, and possibilities, of "UHECR astronomy" with heavy nuclei. Finally, we present a quantitative study of the impact of the GMF on the (de-)magnification of source fluxes, due to magnetic lensing effects. We find that for 60 EeV iron nuclei, sources located in up to about one fifth of the sky would have their fluxes so strongly demagnified that they would not be detectable at Earth, even by the next generation of UHECR experiments.