Speaker: Professor Jungyeon Cho, Chungnam National University, Korea
Abstract: In usual astrophysical circumstances, magnetic diffusivity is very low and, as a result, magnetic fields lines are tied to fluid elements. Therefore random turbulence motions can efficiently stretch magnetic field lines, which results in amplification of magnetic field. This turbulence dynamo is believed to play important roles in the origin of cosmic magnetism. For turbulence dynamo, a weak seed magnetic field is required. If the seed field has a primordial origin, it could be regarded as uniform (or homogeneous) at the scale of galaxy clusters. On the other hand, if the seed field is ejected from an astrophysical body, it could be highly localized in space at the beginning. In this talk I'll discuss growth of uniform and localized seed magnetic fields in turbulence. I will demonstrate that growth of both uniform and localized seed magnetic fields in clusters of galaxies is very similar. Therefore, it is difficult to tell whether or not the seed magnetic field has a cosmological or an astrophysical origin in clusters of galaxies. However, I'll show that it is possible to tell the difference in filaments. I’ll also claim that turbulence dynamo models favor an astrophysical origin of cosmic magnetism, rather than a primordial origin.