Magnetic fields in our Galaxy: How much do we know? III. Progress in the last decade

Abstract

A decade ago, there was very limited knowledge of magnetic fields of our Galaxy. The local fields in the Solar vicinity were known to be directed towards a Galactic longitude $l\sim~90^{\circ}$ with reversed directions at smaller Galacto-radii. The regular field strength was found to be about 2~$μ$G. The filaments near the Galactic Center show the possible poloidal fields there. There was no information about the magnetic fields in the Galactic halo. In last decade, there has been significant progress on measurements of the Galactic magnetic fields. In the Galactic disk, from the RMs of a large number of newly observed pulsars, large-scale magnetic fields along the spiral arms have been delineated in a much larger region then 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 A0 dynamo operating in the halo. The strength of large-scale fields also has been found from pulsar RM data to exponentially increase at smaller Galacto-radii. 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.