β-plane magnetohydrodynamic turbulence in the solar tachocline

This Letter discusses the role of a weak toroidal magnetic field in modifying the turbulent transport properties of stably stratified rotating turbulence in the tachocline. A local two-dimensional beta-plane model is investigated numerically. In the absence of magnetic fields, nonlinear interactions of Rossby waves lead to the formation of strong mean zonal flows. However, the addition of even a very weak toroidal field suppresses the generation of mean flows. We argue that this has serious implications for angular momentum transport in the lower tachocline.