On the anisotropy in the arrival directions of ultra-high-energy cosmic rays

TL;DR

This study uses detailed four-dimensional simulations to analyze the anisotropy in the arrival directions of ultra-high-energy cosmic rays, predicting a strong dipolar pattern consistent with recent observations and providing a basis for future research.

Contribution

It introduces a realistic astrophysical simulation framework that accurately reproduces observed anisotropy patterns in UHECRs and predicts higher-order angular contributions.

Findings

Pronounced dipolar anisotropy in UHECR arrival directions

Weak higher-order angular contributions in the power spectrum

Simulation results align with recent Pierre Auger Observatory data

Abstract

We present results of elaborate four-dimensional simulations of the propagation of ultra-high-energy cosmic rays (UHECR), which are based on a realistic astrophysical scenario. The distribution of the arrival directions of the UHECR is found to have a pronounced dipolar anisotropy and rather weak higher-order contributions to the angular power spectrum. This finding agrees well with the recent observation of a dipolar anisotropy for UHECR with arrival energies above 8 EeV by the Pierre Auger Observatory and constitutes an important prediction for other energy ranges and higher-order angular contributions for which sufficient experimental data are not yet available. Since our astrophysical scenario enables simulations that are completely consistent with the available data, this scenario will be a very useful basis for related future studies.