Magnetic fields in primordial accretion disks

Magnetic fields are considered a vital ingredient of contemporary star formation and may have been important during the formation of the first stars in the presence of an efficient amplification mechanism. Initial seed fields are provided via plasma fluctuations and are subsequently amplified by the small-scale dynamo, leading to a strong, tangled magnetic field. We explore how the magnetic field provided by the small-scale dynamo is further amplified via the alpha-Omega dynamo in a protostellar disk and assess its implications. For this purpose, we consider two characteristic cases, a typical Pop. III star with 10 M-circle dot and an accretion rate of 10(-3) M-circle dot yr(-1), and a supermassive star with 10(5) M-circle dot and an accretion rate of 10(-1) M-circle dot yr(-1). For the 10 M-circle dot Pop. III star, we find that coherent magnetic fields can be produced on scales of at least 100 AU, which are sufficient to drive a jet with a luminosity of 100 L-circle dot and a mass outflow rate of 10(-3.7) M-circle dot yr(-1). For the supermassive star, the dynamical timescales in its environment are even shorter, implying smaller orbital timescales and an efficient magnetization out to at least 1000 AU. The jet luminosity corresponds to similar to 10(6.0) L-circle dot and a mass outflow rate of 10(-2.1) M-circle dot yr(-1). We expect that the feedback from the supermassive star can have a relevant impact on its host galaxy.