Breaking Taylor-Proudman Balance by Magnetic Fields in Stellar Convection Zones

We carry out high-resolution calculations for the stellar convection zone. The main purpose of this Letter is to investigate the effect of a small-scale dynamo on the differential rotation. The solar differential rotation deviates from the Taylor-Proudman state in which the angular velocity does not change along the rotational axis. To break the Taylor-Proudman state deep in the convection zone, it is thought that a latitudinal entropy gradient is required. In this Letter, we find that the small-scale dynamo has three roles in the deviation of the stellar differential rotation from the Taylor-Proudman state. 1) The shear of the angular velocity is suppressed. This leads to a situation where the latitudinal entropy gradient efficiently breaks the Taylor-Proudman state. 2) The perturbation of the entropy increases with the suppression of the turbulent velocity between upflows and downflows. 3) The convection velocity is reduced. This increases the effect of the rotation on the convection. The second and third factors increase the latitudinal entropy gradient and break the Taylor-Proudman state. We find that an efficient small-scale dynamo has a significant impact on the stellar differential rotation.