Cosmological magnetic field generation by the Weibel instability

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The processes leading to the magnetization of the intergalactic medium are not yet known. Large-scale structures in the universe, like filaments and sheets of galaxies, evolve by the gravitational collapse of initially overdense regions giving rise to an intense relative motion of fully ionized gaseous matters and strong gaseous shock structures. It is proposed to investigate the conditions under which magnetic fields in the intergalactic medium may be generated due to the Weibel-type instabilities involving interpenetrating electron streams. Because of the hot temperatures of the intergalactic medium the investigation of the Weibel instability will be based on the now available covariantly correct dispersion theory of linear waves, and thus improve significantly on the existing non-relativistic treatments in the literature. These primordial Weibel magnetic fields may serve as cosmological seed fields for even stronger magnetic fields in cosmological sources. The existence of magnetic fields is a mandatory requirement for the onset of most nonthermal phenomena in cosmological sources especially gamma-ray burst sources and relativistic jet sources. According to current understanding the formation of relativistic jets in centers of galaxies, powered by accretion onto a supermassive black hole, is due to a fast super-Alfvenic MHD wind from the rotating accretion disk where the magnetic field anchored in the accretion disk is crucial for the jet collimation. Relativistic magnetized shock waves form when e.g. a faster wind overtakes the slower wind giving rise to intense acceleration of charged particles by diffusive shock acceleration and subsequent Doppler beamed and superluminal nonthermal radiation components. Studying the nonthermal history of our Universe is closely linked to the understanding of the cosmological magnetization processes.