论文标题
完全对流恒星的恒星模拟
Star-in-a-box simulations of fully convective stars
论文作者
论文摘要
（删节）上下文：主序列的后期型恒星小于$ 0.35 m_ \ odot $是完全对流的。目的：目的是研究对流，差异旋转和发电机作为完全对流恒星中旋转的功能。方法：使用恒星式盒子模型，其中使用球形恒星浸入笛卡尔立方体内，其中三维流体动力学和磁流体动力学模拟模拟。该型号对应于$ 22万美元的\ odot $ m5矮人。探索了4.3至430天之间的旋转期（$ p _ {\ rm rot} $）。结果：$ p _ {\ rm rot} = 430 $天的缓慢旋转模型与缓慢的赤道和快速杆一起产生反 - 极差异旋转，以及主要是轴对称准稳态的大规模磁场。对于中间旋转（$ p _ {\ rm rot} = 144 $，$ 43 $ days）差速旋转是太阳能（快速赤道，慢速杆），大规模磁场主要是轴对称性，并且是准平台或循环。后者以类似的参数状态出现，与球形壳中的其他数值研究相似，并且周期周期类似于完全对流的恒星中观察到的周期，具有可比的$ p _ {\ rm rot} $。在快速旋转方案中，差速器旋转较弱，大规模磁场越来越非轴对称，并且$ m = 1 $模式。这个大尺度的非轴对称场也表现出方位角发动力。结论：恒星中的A-A-Box模型的结果与球形壳中部分对流的晚期恒星的模拟一致，因为差异旋转和发电机状态的过渡以类似的旋转状态出现在Coriolis（反Rossby）数字上。部分和完全对流的星星之间的相似性表明，产生差异旋转和大规模磁性的过程对恒星的几何形状不敏感。
(abridged) Context: Main-sequence late-type stars with masses less than $0.35 M_\odot$ are fully convective. Aims: The goal is to study convection, differential rotation, and dynamos as functions of rotation in fully convective stars. Methods: Three-dimensional hydrodynamic and magnetohydrodynamic numerical simulations with a star-in-a-box model, where a spherical star is immersed inside of a Cartesian cube, are used. The model corresponds to a $0.2M_\odot$ M5 dwarf. Rotation periods ($P_{\rm rot}$) between 4.3 and 430 days are explored. Results: The slowly rotating model with $P_{\rm rot}=430$ days produces anti-solar differential rotation with a slow equator and fast poles, along with predominantly axisymmetric quasi-steady large-scale magnetic fields. For intermediate rotation ($P_{\rm rot}=144$ and $43$ days) differential rotation is solar-like (fast equator, slow poles) and large-scale magnetic fields are mostly axisymmetric and either quasi-stationary or cyclic. The latter occurs in a similar parameter regime as in other numerical studies in spherical shells, and the cycle period is similar to observed cycles in fully convective stars with comparable $P_{\rm rot}$. In the rapid rotation regime the differential rotation is weak and the large-scale magnetic fields are increasingly non-axisymmetric with a dominating $m=1$ mode. This large-scale non-axisymmetric field also exhibits azimuthal dynamo waves. Conclusions: The results of the star-in-a-box models agree with simulations of partially convective late-type stars in spherical shells in that the transitions in differential rotation and dynamo regimes occur at similar rotational regimes in terms of the Coriolis (inverse Rossby) number. This similarity between partially and fully convective stars suggests that the processes generating differential rotation and large-scale magnetism are insensitive to the geometry of the star.
