No anti-solar: Solar-type stars always have solar-like differential rotation

For more than 45 years, scientists have believed in the existence of two classes of differential rotation (DR), solar-like and anti-solar. The Sun rotates differentially with a fast equator and slow poles, called solar-like DR. Theoretical studies suggest that this DR becomes anti-solar in slowly rotating stars, where the poles rotate faster. The DR topology significantly affects the stellar magnetic activity and long-time stellar evolution. According to recently reported observations, however, there are inconsistencies with this solar-like and anti-solar idea in several aspects. We carry out unprecedentedly high-resolution magnetohydrodynamic simulations for the slowly rotating solar-type stars. The simulated solar-type stars always show solar-like DR even with significantly slow rotation rates in our simulations. Here we show that no anti-solar DR is achieved. The strong magnetic field maintains the solar-like DR in all cases. The rotation has a less significant influence on the magnetic field strength than that on the turbulence anisotropy. Our results show that the magnetic field monotonically decreases over the stellar lifetime, indicating a weakening of the magnetic braking. This trend is also consistent with recent observational results of the stellar rotation evolution.