Formation of starspots in self-consistent global dynamo models: Polar spots on cool stars
Formation of starspots in self-consistent global dynamo models: Polar spots on cool stars
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自洽全球发电机模型中星黑子的形成：冷恒星上的极地黑子
DOI：
10.1051/0004-6361/201424589
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Reiners
中科院分区：
文献类型：
--
作者：
Gastine;Christensen;Reiners
对冷恒星的观测揭示了它们表面上的黑点状特征。这些恒星黑子可以比太阳黑子更广泛，覆盖恒星表面的大面积。虽然太阳黑子只出现在低纬度地区，但在极地地区也可以发现星斑，特别是在快速旋转的恒星上。传统的通量管模型已被调用来解释星点的属性。然而，这些模型使用了几种简化，到目前为止，在恒星磁对流的自洽模拟中还没有产生太阳黑子和星黑子。目的我们的目标是澄清对流驱动恒星发电机数值模型中自发形成黑点所需的条件。方法假设滞弹性近似，我们模拟了快速旋转球壳中的对流和磁场产生。高分辨率的模拟进行了使用全谱magnetohydrodynamic codes.ResultsWe证明了第一次，一个自洽的分布式发电机可以自发地产生高纬度的暗点。当对流区的大部分产生的大规模磁场与表面附近的流动相互作用并局部淬灭时，就会产生暗斑。足够强的密度分层和快速旋转的先决条件，在model.ConclusionsOur模型中形成相当大的暗斑提出了一种替代方案的星点形成分布式发电机行动。我们的研究结果也有力地支持了这样一种观点，即快速旋转恒星内部的发电机可能与太阳内部的发电机根本不同。
ContextObservations of cool stars reveal dark spot-like features on their surfaces. These starspots can be more extended than sunspots and cover a large area of the stellar surface. While sunspots appear only at low latitudes, starspots are also found in polar regions, in particular on rapidly rotating stars. Conventional flux-tube models have been invoked to explain starspot properties. However, these models use several simplifications, and so far, neither sunspots nor starspots have been generated in a self-consistent simulation of stellar magnetic convection.AimsWe aim to clarify the conditions necessary for the spontaneous formation of dark spots in numerical models of convection-driven stellar dynamos.MethodsWe simulated convection and magnetic field generation in rapidly rotating spherical shells assuming anelastic approximation. The high-resolution simulations were performed using a fully spectral magnetohydrodynamic code.ResultsWe demonstrate for the first time that a self-consistent distributed dynamo can spontaneously generate high-latitude dark spots. Dark spots are generated when a large-scale magnetic field, generated in the bulk of the convection zone, interacts with and locally quenches flow near the surface. Sufficiently strong density stratification and rapid rotation are prerequisites for the formation of sizeable dark spots in the model.ConclusionsOur models present an alternative scenario for starspot formation by distributed dynamo action. Our results also lend strong support to the idea that dynamos in the interiors of rapidly rotating stars might be fundamentally different from the solar one.