Magnetic field generation by resonance absorption of light

We consider the self-generated dc magnetic fields due to resonant excitation of plasma waves by intense laser light. From Ampere's law we show that the time scale associated with the growth of the magnetic field is essentially the same as the time scale for the growth of the plasma wave. Further, we obtain a simple expression for the steady-state magnetic fields arising from a steady-state current derived in terms of the high-frequency excited fields. Computer simulations verify the theoretical conclusions on both the time variation and the steady-state value of the magnetic field. Difficulties of earlier calculations based on the so-called stress-tensor approach are discussed, and it is shown that the proper use of this method requires the use of a self-consistent kinetic theory for the plasma which takes into account the convection of momentum out of the resonance region.