Magnetic Field Amplification at the Maximum Torque State in a 1000 Rm Spherical Couette Experiment.*

The search for a spherical Couette magnetic dynamo in the laboratory continues. The dynamo action is the process through which a magnetic field is amplified and sustained by electrically conductive flows. This is an ubiquitous phenomenon in nature: Galaxies, stars and planets, all exhibit magnetic field amplification by their conductive constituents. At the University of Maryland our 3-m diameter spherical Couette experiment uses liquid sodium between concentric spheres to mimic some of the dynamics of these flows. We are now progressing from the previous amplified magnetic fields toward a possible dynamo state based on adding baffles to the inner sphere. While the modifications take place we focus our attention on previous unpublished experimental runs with a smooth inner sphere that achieved substantial amplification of the magnetic field but without dynamo generation. We present magnetic field amplification as a function of the different experimental parameters including Reynolds  and Rossby numbers. Thanks to recent studies in a hydrodynamic scale model, we can bring a better insight into these results and propose locations in the parameter space of the experiment as possible candidates for a dynamo generation given the forthcoming modifications that are currently taking place.