New knowledge of the Galactic magnetic fields

TL;DR

This paper reviews recent advances in understanding the Galactic magnetic fields, highlighting new measurements and insights into their structure, strength, and dynamo mechanisms in the Milky Way.

Contribution

It summarizes recent observational findings on the large-scale magnetic field structure and dynamo processes in the Galactic disk and halo.

Findings

Large-scale magnetic fields delineated along spiral arms.

Opposite directions of halo toroidal fields above and below the plane.

Magnetic field strength increases exponentially towards the Galactic center.

Abstract

The magnetic fields of our Milky Way galaxy are the main agent for cosmic rays to transport. In the last decade, much new knowledge has been gained from measurements of the Galactic magnetic fields. In the Galactic disk, from the RMs of a large number of newly discovered pulsars, the large-scale magnetic fields along the spiral arms have been delineated in a much larger region than ever before, with alternating directions in the arm and interarm regions. The toroidal fields in the Galactic halo were revealed to have opposite directions below and above the Galactic plane, which is an indication of an A0 mode dynamo operating in the halo. The strength of large-scale fields obtained from pulsar RM data has been found to increase exponentially towards the Galactic center. Compared to the steep Kolmogorov spectrum of magnetic energy at small scales, the large-scale magnetic fields show a shallow broken spatial magnetic energy spectrum.