Normalized azimuthal velocity averaged over one cycle as a function of depth. The red line corresponds to an hydrodynamical viscous steady state without magnetic field. The blue curve shows results with the toroidal component set to zero at the top of the tachocline, as in FDP01. The green lines are cases with oscillating poloidal and toroidal magnetic fields, with different phase lags. Corresponding model parameter values are listed in Table 1.