Abstract: The universe is magnetized, from stars like the Sun, to the large-scale coherent magnetic fields detected in galaxies and galaxy clusters. The standard picture for the origin of fields in all astrophysical systems involves turbulent dynamo amplification of a weak seed magnetic field. The simplest of such dynamos are fluctuation dynamos, where turbulentmotions in conducting plasma amplify the random fields under fairlygeneric conditions. They would be relevant for the generation of magneticfields in galaxy clusters and the first magnetic fields in young galaxies.We review the basic idea behind such dynamos and the main challenges they encounter. While it is relatively easy for magnetic energy to grow, explaining the observed degree of spatio-temporal coherence of the observed magnetic fields remains challenging.
Kandaswamy is a Cluster guest. Local host: Torsten Ensslin (MPA)