Generation of magnetic field in the pre-recombination era

We study the possibility of generating magnetic fields during the evolution of electron, proton and photon plasma in the pre-recombination era. We show that a small magnetic field can be generated in the second order of perturbation theory for scalar modes with adiabatic initial conditions. The amplitude of the field is 10 -30 G at the present epoch for scales from subkiloparsec to 100 Mpc.