The Galactic Magnetic Field and UHECR Optics

TL;DR

This paper reviews the Galactic magnetic field model, emphasizing its importance for cosmic ray studies, and presents new findings on how the GMF lensing affects ultra-high-energy cosmic rays, showing multiple images and variable magnification.

Contribution

It provides a review of the Jansson-Farrar 2012 GMF model and introduces new results on UHECR lensing effects caused by the GMF.

Findings

Evidence for a N-to-S directed, spiraling halo field.

Multiple images and magnification variations of UHECRs due to GMF lensing.

Dependence of lensing effects on source direction and CR rigidity.

Abstract

A good model of the Galactic magnetic field is crucial for estimating the Galactic contribution in dark matter and CMB-cosmology studies, determining the sources of UHECRs, and also modeling the transport of Galactic CRs since the halo field provides an important escape route for by diffusion along its field lines. We briefly review the observational foundations of the Jansson-Farrar 2012 model for the large scale structure of the GMF, underscoring the robust evidence for a N-to-S directed, spiraling halo field. New results on the lensing effect of the GMF on UHECRs are presented, displaying multiple images and dramatic magnification and demagnification that varies with source direction and CR rigidity.