Magnetic Helicity and Turbulent Dynamos

The generation of large scale magnetic fields in highly conducting, turbulent fluids is a common and important process in astrophysics. Mean field dynamo theory conventionally relies on an intrinsic kinetic helicity in the underlying turbulence. Here we show how differential rotation drives a magnetic helicity flux embedded in small scale structures. This in turn leads to the large scale dynamo. We note that this process always dominates over the kinematic dynamo. Balancing this process against buoyant losses and turbulent mixing, we can naturally predict the dependence stellar magnetic fields on stellar rotation rates.