Magnetic induction by coherent vortex motion

We investigate experimentally the advection of a magnetic field by a flow o f conducting fluid, at moderate magnetic Reynolds numbers. More specificall y, we study the influence of a large scale intense vortex on an externally applied field. We show that at large scales the magnetic field lines are di storted in a way that is consistent with a scenario of magnetic field expul sion by vorticity. Measurements at small scales show that the magnetic fluc tuations are also quite sensitive to the large scale vortex motion.