Primordial galactic magnetic fields from domain walls at the QCD phase transition

We propose a mechanism to generate large-scale magnetic fields with correla tion Lengths of 100 kpc. Domain walls with QCD-scale internal structure for m and coalesce, obtaining Hubble-scale correlations while aligning nucleon spins. Because of strong CP violation, the walls are ferromagnetic, which i nduces electromagnetic fields with Hubble-size correlations. The CP violati on also induces a maximal helicity (Chern-Simons) which supports an "invers e cascade," allowing the initial correlations to grow to 100 kpc today. We estimate the generated electromagnetic fields in terms of the QCD parameter s and discuss the effects of the resulting fields.