Evolution and structure of magnetic fields in simulated galaxy clusters

We use cosmological magneto-hydrodynamic simulations to study the evolution of magnetic fields in galaxy clusters in two different cosmological models, a standard-CDM and a Lambda-CDM model. We show that the magnetic field strength profiles closely follow the cluster density profiles outside a core region of radius similar to200 h(-1) kpc. The magnetic field has a correlation length of order 50 h(-1) kpc and reverses on scales of similar to100 h(-1) kpc along typical lines-of-sight. The power spectrum of the magnetic field can well be approximated by a steep power law with an exponent of similar to-2.7. The mean magnetic field in the cluster cores grows roughly exponentially with decreasing redshift, Bsimilar to10(-2.5z) muG. Merger events have a pronounced effect on magnetic field evolution, which is strongly reflected in measurable quantities like the Faraday rotation. The field evolution in the two different cosmologies proceeds virtually identically. All our cluster models very well reproduce observed Faraday rotation measurements when starting with nG seed fields.