从太阳到反太阳廓线过渡附近磁控恒星的差异旋转
Magnetically controlled stellar differential rotation near the transition from solar to anti-solar profiles
摘要：
晚型恒星的旋转差异，由于各向异性湍流在其外部对流区。当赤道旋转最快时，这种旋转被称为类日旋转（SL），否则称为反日旋转（AS）。流体动力学模拟表明，从SL到AS旋转的旋转对流的影响减少，但相反的过渡发生在参数空间中的不同点。该系统是可扩展的，即，SL和AS旋转轮廓都可以是稳定的。我们研究了发电机产生的磁场对大尺度流动的影响，特别是对差动旋转的扰动行为的可能性。我们解决了磁流体方程数值旋转球壳的一组不同的辐射传导率控制对流的相对重要性。与早期的研究结果相一致，我们的模型显示SL旋转配置文件时，对流的旋转影响是强大的和过渡到AS时，旋转的影响减少。我们发现，发电机产生的磁场有助于产生SL差分旋转相比，流体动力学模拟。我们没有观察到任何微分转动的双态。在AS的情况下，我们得到了连贯的单细胞单细胞循环，而在SL的情况下，我们得到多细胞模式。在这两种情况下，我们得到的极地环流的表面附近的大小接近在太阳中观察到的。此外，差旋和纬向环流都有显著的磁循环相关变化，其强度与太阳相似。差分旋转和旋转环流的Pendulum流体动力学模拟被证明是有限的相关性的磁场，自洽产生的发电机行动，显着影响的流量。
英文摘要：
Late-type stars rotate differentially owing to anisotropic turbulence in their outer convection zones. The rotation is called solar-like (SL) when the equator rotates fastest and anti-solar (AS) otherwise. Hydrodynamic simulations show a transition from SL to AS rotation as the influence of rotation on convection is reduced, but the opposite transition occurs at a different point in the parameter space. The system is bistable, i.e., SL and AS rotation profiles can both be stable. We study the effect of a dynamo-generated magnetic field on the large-scale flows, particularly on the possibility of bistable behavior of differential rotation. We solve the hydromagnetic equations numerically in a rotating spherical shell for a set of different radiative conductivities controlling the relative importance of convection. In agreement with earlier findings, our models display SL rotation profiles when the rotational influence on convection is strong and a transition to AS when the rotational influence decreases. We find that dynamo-generated magnetic fields help to produce SL differential rotation compared to the hydrodynamic simulations. We do not observe any bistable states of differential rotation. In the AS cases we get coherent single-cell meridional circulation, whereas in SL cases we get multi-cellular patterns. In both cases, we obtain poleward circulation near the surface with a magnitude close to that observed in the Sun. Moreover, both differential rotation and meridional circulation have significant magnetic cycle-related variations that are similar in strength to those of the Sun. Purely hydrodynamic simulations of differential rotation and meridional circulation are shown to be of limited relevance as magnetic fields, self-consistently generated by dynamo action, significantly affect the flows.
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