THE ORIGIN OF INTERGALACTIC MAGNETIC-FIELDS DUE TO EXTRAGALACTIC JETS

We study the large-scale magnetization of intra- and intercluster media due to electric current-carrying extragalactic jets generated by active periods of galactic nuclei. The Lorentz force acting on the return current path has an expansive character which is responsible for the generation of a growing magnetic cocoon surrounding the associated jet. It is shown that such growing cocoons can be the source of intergalactic magnetization. The everlasting character of currents generated in the highly conductive protogalactic or generic intergalactic media provides the long-term action of such an electrodynamic expansion, and the large-scale character of this magnetization process. The model is specifically applied to: (i) Cygnus A, NGC 6251, 3C 465, and M84, where several peculiar features of magnetic nature have been observed; and (ii) the formation of large-scale cells of intergalactic magnetic field. Cosmogonic implications associated with the model are briefly discussed. The model can account, both qualitatively and quantitatively, for several previously unsolved large-scale magnetic features.