Structure in the Magnetic Field of the Milky Way Disk and Halo traced by Faraday Rotation

Understand

Magnetic fields in the ionized medium of the disk and halo of the Milky Way impose Faraday rotation on linearly polarized radio emission.

• We compare two surveys mapping the Galactic Faraday rotation, one showing the rotation measures of extragalactic sources seen through the Galaxy (from Hutschenreuter et al 2022), and one showing the Faraday depth of the diffuse Galactic synchrotron emission from the Global Magneto-Ionic Medium Survey.
• Comparing the two data sets in 5deg x 10deg bins shows good agreement at intermediate latitudes, 10 < |b| < 50 deg, and little correlation between them at lower and higher latitudes.
• Where they agree, both tracers show clear patterns as a function of Galactic longitude: in the Northern Hemisphere a strong sin(2 x longitude) pattern, and in the Southern hemisphere a sin(longitude + pi) pattern.