Physics and Astronomy Calendar

It is believed that magnetic fields in tenuous plasmas can be amplified by turbulent motions through stretching of field lines. Recently, we have suggested that turbulence could be produced by cascade of the vorticity generated behind cosmological shocks, and that the intergalactic magnetic fields (IGMFs) could be amplified by such turbulence in the large-scale structure (LSS) of the Universe Ryu et al., Science 320 (2008) 909.
Cosmological shocks are induced by gravitational clustering of nonlinear structures and they heat and ionize the intergalactic medium. Using a high-resolution, cosmological N-body/hydrodynamic simulation, we first estimate the spatial and temporal distributions of the vorticity and turbulent kinetic energy density in the LSS. We then estimate the fraction of turbulent energy that is converted to magnetic field energy by employing the results from magnetohydrodynamic simulations of the
turbulence dynamo. Applying a conversion factor to the aforementioned LSS simulation, we estimate that the mean strength of the IGMFs at the present universe could be on the order of microG inside clusters and groups and ~10 nanoG in filaments, whereas it should be much lower in sheetlike structures and voids.