The Galactic Magnetic Field and Ultrahigh-Energy Cosmic Ray Deflections

TL;DR

This paper reviews the current understanding of the Galactic magnetic field, discusses the Jansson and Farrar model, and explores its implications for ultrahigh-energy cosmic ray deflections, highlighting areas for future improvement.

Contribution

It provides an overview of the JF12 GMF model, assesses its robustness, and discusses its application to UHECR deflections, proposing directions for enhanced modeling.

Findings

The JF12 model constrains key features of the GMF.

Current models can inform UHECR deflection estimates.

Identifies critical data and theoretical needs for future GMF modeling.

Abstract

Our understanding of the Galactic magnetic field (GMF) has increased considerably in recent years, while at the same time remaining far from adequate. By way of illustration, the Jansson and Farrar (2012) (JF12) GMF model is described, emphasizing how it is constrained and which features are robust or likely to change, as modelling and constraining data improve. The most urgent requirements for the next phase of modelling are a more realistic model for the relativistic electron distribution (in order to reduce the systematic error associated with interpreting synchrotron data) and a better theoretical understanding of the origin of the large-scale coherent field (in order to develop a better phenomenological parameterization of the field). Even in its current stage of development, the JF12 model allows some important conclusions about UHECR deflections in the GMF to be formulated.