The Cosmic Dynamo

This IAU-symposium was the first which was entirely dedicated to dynamo processes, which are fundamental on all cosmical scales. Dynamo theory concerns one of the few truly key questions of recent cosmic physics. There is increasing evidence for the magnetic character of most short-term activity phenomena in astrophysics. Obviously, the tria. ngle "gravil;y, nuclea. r power, magnetism" dictates cosmic evolution over a very broad scale of magnitudes. A complicated interplay of rotation, magnetism and turbulence, that is hard to resolve, determines stellar and galactic activity for almost all the short and medium time­ scales. Behind these multiform phenomena, the cosmic dynamo works in various guise. . "I, all involving inductive and dissipative equilibria in rotating turbulent cosmic plasmas. The Sun, representing the cosmic dynamo par excellence, stands from the be­ ginning at the centre of interest for those who followed the dynamo idea. Even the first models were able to present an explanation of the typical structural appear­ ance of the solar magnetic field, i. e. a 22 year cycle, activit. y belts and their zonal migration, antisymmetry of t. he magnetic polarity. However, the solar dynamo still provides topics of further discussions, since confrontation with recent observational data raised and stoill raises new questions, nOll of whicll have yet found a plausible answer. These questions represent a challenge for the development of the basic the­ ories: Understanding of turbulence, especially Ilsing methods of modern nonlinear physics. Numerical simulations arc promising in the ncar future.