Primordial magnetic field from chiral plasma instability with sourcing

In an electron-positron plasma, an imbalance in the number of right- and left-chiral particles can lead to the growth of a helical magnetic field through a phenomenon called the chiral plasma instability (CPI). In the early Universe, scattering reactions that violate chirality come into thermal equilibrium when the plasma cools below a temperature of approximately 80 TeV. Since these reactions tend to relax any preexisting chiral asymmetry to zero as the system approaches equilibrium, the standard lore is that primordial magnetogenesis via the CPI is not viable below 80 TeV. In this work, we propose that the presence of a source for chirality can allow the CPI to operate even below 80 TeV, we explore the implications of this scenario, and we derive predictions for the resultant magnetic field helicity using a combination of analytical methods and direct numerical simulation.