Dynamo threshold in a turbulent medium

We study the magnetic self-generation in a turbulent conducting fluid by means of a stochastic equation. Both the effect of the mean flow and that of the turbulent fluctuations are considered. A quantitative criterion for the existence of a dynamo instability in the presence of turbulence is derived. This criterion is expressed in terms of an average over the possible orientations of the magnetic field. However, it can give insight about the influence of noise on the dynamo threshold