The turbulent magnetic Milky Way, deriving a turbulent field scale height from POSSUM data

Abstract:

Using broadband polarimetric observations from the ASKAP POSSUM survey, I investigate the turbulent magnetised interstellar medium of the Milky Way through Faraday complexity in more than 37,000 polarised extragalactic radio sources. By applying QU-fitting to the Stokes Q and U spectra, I measure Faraday broadening, which traces fluctuations in the line-of-sight magnetic field and thermal electron density. I examine the Galactic latitude dependence of turbulence and interpret the results using the exponential disk model. The results also suggest a possible north–south asymmetry in the turbulent foreground, potentially linked to Galactic structure, spiral arms, warp, or the Magellanic system. I discuss the role of turbulence correlation length assumptions, comparisons with pulsar scintillation and RM structure-function studies, and ongoing work using RM structure functions to constrain the physical scales of turbulence probed by POSSUM.