Abstract: Astrophysical systems like stars and galaxies host large-scale magnetic fields, whose coherence scales are larger than the turbulence scales in these systems. We review the basic idea behind the large-scale dynamo and the challenges they face. First, they need to get rid of small scale magnetic helicity which naturally arises during the generation of large-scale fields. Second they have to come to terms with the more rapid generation of small-scale fields by the fluctuation dynamo. We discuss how both these problems are potentially overcome. In relation to the second challenge, we present evidence for a unified large/small scale dynamo in helical turbulent systems.
Kandaswamy is a Cluster guest. Local host: Torsten Ensslin (MPA)