Mapping UHECRs deflections through the turbulent galactic magnetic field with the latest RM data

TL;DR

This paper links observed rotation measure variances to cosmic ray deflections caused by the turbulent Galactic magnetic field, creating a map that estimates deflections of ultra high-energy cosmic rays across the sky.

Contribution

It introduces a method to estimate cosmic ray deflections using rotation measure data without detailed magnetic field modeling.

Findings

Most of the sky shows deflections under 2 degrees for 40 EeV protons.

Deflections can reach up to 5 degrees near the Galactic plane.

The method constrains deflections based on electron density spectrum parameters.

Abstract

We study the influence of the random part of the Galactic magnetic field on the propagation of ultra high-energy cosmic rays. Within very mild approximations about the properties of the electron density fluctuations in the Galaxy we are able to derive a clear and direct relation between the observed variance of rotation measures and the predicted cosmic ray deflections. Remarkably, this is obtained bypassing entirely the detailed knowledge of the magnetic properties of the turbulent plasma. Depending on the parameters of the electron density spectrum, we can either directly estimate the expected deflection, or constrain it from above. Thanks to the latest observational data on rotation measures, we build a direction-dependent map of such deflections. We find that over most of the sky the random deflections of 40 EeV protons do not exceed 1 to 2 degrees, and can be as large as 5 degrees close to the Galactic plane.