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We investigate the generation processes of magnetic fields around first stars. Since first stars are expected to form anisotropic ionization fronts in the surrounding clumpy media, magnetic fields are generated by the effects of radiation force, as well as the Biermann battery effect. We calculated the amplitude of the magnetic field generated by the effects of radiation force around the first stars in a preceding paper but the Biermann battery effects were not taken into account. In this paper, we calculate the generation of magnetic fields by the Biermann battery effect as well as the effects of radiation force, utilizing radiation hydrodynamics simulations. As a result, we find that the generated magnetic field strengths are ~10-19 G - 10-17 G at ~ 100 pc-1 kpc scale, an order of magnitude larger than the results of our previous study mainly as a result of the Biermann battery effect. We also find that this result is insensitive to various physical parameters including the mass of the source star and the distance between the source and the dense clump, unless we take unlikely values of these parameters. [ABSTRACT FROM AUTHOR]

We study the dissipation process of magnetic fields in the metallicity range 0-1 Z☼ for contracting prestellar cloud cores. By solving non-equilibrium chemistry for important charged species, including charged grains, we evaluate the drift velocity of the magnetic-field lines with respect to the gas. We find that the magnetic flux dissipates in the density range 1012 cm–3 ≲ nH ≲ 1017 cm–3 for the solar-metallicity case at the scale of the core, which is assumed to be the Jeans scale. The dissipation density range becomes narrower for lower metallicity. The magnetic field is always frozen to the gas below metallicity ≲ 10–7-10–6Z☼, depending on the ionization rate by cosmic rays and/or radioactivity. With the same metallicity, the dissipation density range becomes wider for lower ionization rates. The presence of such a dissipative regime is expected to cause various dynamical phenomena in protostellar evolution such as the suppression of jet/outflow launching and the fragmentation of circumstellar disks depending on the metallicity. [ABSTRACT FROM AUTHOR]