Feedback of a small-scale magnetic dynamo - art. no. 016408

We develop a WKB approach to the rapid distortion theory for magnetohydrody namic turbulence with large magnetic Prandtl number. Within this theory, we study the growth of small-scale magnetic fluctuations in a large-scale vel ocity field being initially a pure strain. We show that the magnetic Lorent z force excites a secondary flow in the form of counterrotating vortices on the periphery of the magnetic spot. Those vortices slow down stretching of the magnetic spot and thus provide a negative feedback for a small-scale m agnetic dynamo.