The Coherent Magnetic Field of the Milky Way
Michael Unger, Glennys R. Farrar

TL;DR
This paper develops and tests models of the Milky Way's magnetic field using observational data, providing insights into its structure, strength, and implications for cosmic phenomena.
Contribution
The study introduces divergence-free parametric models of the Galactic magnetic field fitted to recent observational data, exploring various configurations and their implications.
Findings
Local magnetic pitch angle is 11+/-1 degrees.
Inconclusive evidence for a grand-design spiral magnetic field.
Toroidal and poloidal halo fields are of similar magnitude within 10%.
Abstract
We present a suite of models of the coherent magnetic field of the Galaxy (GMF) based on new divergence-free parametric functions describing the global structure of the field. The model parameters are fit to the latest full-sky Faraday rotation measures of extragalactic sources (RMs) and polarized synchrotron intensity (PI) maps from WMAP and Planck. We employ multiple models for the density of thermal and cosmic-ray electrons in the Galaxy, needed to predict the skymaps of RMs and PI for a given GMF model. The robustness of the inferred properties of the GMF is gauged by studying many combinations of parametric field models and electron density models. We determine the pitch angle of the local magnetic field (11+/-1 deg.), explore the evidence for a grand-design spiral coherent magnetic field (inconclusive), determine the strength of the toroidal and poloidal magnetic halo fields below…
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Taxonomy
TopicsSolar and Space Plasma Dynamics · Stellar, planetary, and galactic studies · Magnetic and Electromagnetic Effects
