Distortion of the ultrahigh energy cosmic ray flux from rare transient sources in inhomogeneous extragalactic magnetic fields

TL;DR

This paper explores how inhomogeneous extragalactic magnetic fields can distort the observed flux of ultrahigh energy cosmic rays from rare transient sources, affecting anisotropy studies in future experiments.

Contribution

It introduces a new model for flux distortion caused by magnetic field inhomogeneity and source rarity, with implications for future cosmic ray anisotropy analyses.

Findings

Distortion affects future large-scale experiments with hundreds of events.

Current experiments are not significantly impacted by this distortion.

Flux modulation depends on source visibility probability over experiment lifetime.

Abstract

Detecting and characterizing the anisotropy pattern of the arrival directions of the highest energy cosmic rays are crucial steps towards the identification of their sources. We discuss a possible distortion of the cosmic ray flux induced by the anisotropic and inhomogeneous distribution of extragalactic magnetic fields in cases where sources of ultrahigh energy cosmic rays are rare transient phenomena, such as gamma-ray bursts and/or newly born magnetars. This distortion does not involve an angular deflection but the modulation of the flux related to the probability of seeing the source on an experiment lifetime. To quantify this distortion, we construct sky maps of the arrival directions of these highest energy cosmic rays for various magnetic field configurations and appeal to statistical tests proposed in the literature. We conclude that this distortion cannot affect present experiments but should be considered when performing anisotropy studies with future large-scale experiments that record as many as hundreds of events above 6x10^19 eV.