Power spectra of the primordial Faraday depth Φ for magnetic field strengths of 100 (solid line), 10 (dotted line), and 1 nG (dashed line), the Galactic Faraday depth from the all-sky Faraday map of Oppermann et al. (2015) (blue dashed line), the Galactic Faraday depth from Oppermann et al. (2015) at 45° latitude (green dashed line), the Galactic Faraday depth derived from Galactic emission at 1.4 and 23 GHz (red circles), and the Galactic Faraday depth for a Galactic magnetic field model (black crosses).