Generation of large scale magnetic fields at recombination epoch

It is argued that large scale cosmic magnetic field could be generated in the primeval plasma slightly before hydrogen recombination. Non-zero vorticity, necessary for that, might be created by the photon diffusion in the second order in the temperature fluctuations. The resulting seed fields at galactic scale would be only 4 orders of magnitude smaller than the observed ones and with a mild galactic dynamo amplifying the seed fields by the factor $\sim 10^4$ an existence of coherent magnetic fields in galaxies may be explained.