From solar-like to antisolar differential rotation in cool stars
From solar-like to antisolar differential rotation in cool stars
复制标题
DOI：
10.1093/mnrasl/slt162
复制
发表时间：
2014-02-01
影响因子：
4.8
通讯作者：
Wicht, J.
中科院分区：
文献类型：
--
作者：
Gastine, T.;Yadav, R. K.;Wicht, J.
恒星的微分自转可以分为两种主要模式：类太阳模式，即赤道的自转速度快于两极；反太阳模式，即两极的自转速度快于赤道。我们用旋转球壳的三维数值模拟来研究这两种状态之间的转变。我们进行了系统的参数研究，其中也包括来自不同研究小组的模型。我们发现，微分旋转的方向是由力平衡中科里奥利力的贡献决定的，与模型设置（磁场的存在、对流层的厚度、密度分层）无关。具有小罗斯比数的快速旋转模型产生类似太阳的微分旋转，而弱旋转模型维持反太阳的微分旋转。接近跃迁时，两种微分旋转是两种可能的双稳态。该研究为具有大罗斯比数的冷恒星存在反太阳微分旋转提供了理论支持。
Stellar differential rotation can be separated into two main regimes: solar-like when the equator rotates faster than the poles and antisolar when the polar regions rotate faster than the equator. We investigate the transition between these two regimes with 3D numerical simulations of rotating spherical shells. We conduct a systematic parameter study which also includes models from different research groups. We find that the direction of the differential rotation is governed by the contribution of the Coriolis force in the force balance, independently of the model setup (presence of a magnetic field, thickness of the convective layer, density stratification). Rapidly rotating cases with a small Rossby number yield solar-like differential rotation, while weakly rotating models sustain antisolar differential rotation. Close to the transition, the two kinds of differential rotation are two possible bistable states. This study provides theoretical support for the existence of antisolar differential rotation in cool stars with large Rossby numbers.