Three-dimensional simulations of near-surface convection in main-sequence stars - III. The structure of small-scale magnetic flux concentrations
Three-dimensional simulations of near-surface convection in main-sequence stars - III. The structure of small-scale magnetic flux concentrations
复制标题
主序星近地表对流的三维模拟-III 小尺度磁通量集中结构
DOI：
10.1051/0004-6361/201525788
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发表时间：
2015
影响因子：
6.5
通讯作者：
Reiners
中科院分区：
文献类型：
--
作者：
Schüssler;Cameron;Reiners
背景冷主序星的对流包层蕴藏着具有复杂的全局和局部结构的磁场。这些场以多种方式影响近地表对流和外部恒星大气，并导致可观测到的恒星磁活动。目的我们的目的是了解具有中等平均磁通密度的单极区域的局部结构。这些对应于在高磁活动期间覆盖太阳表面（也可能还包括其他类日恒星表面）的大部分的浅滩区域。方法我们分析了 18 个局部盒磁流体动力学模拟的结果，这些模拟覆盖了对流区的上层和光谱类型 F 到早期 M 的冷主序星的光球层。这些模拟中的平均垂直场范围从 20 到 500 G。结果我们发现了不同光谱类型的主序星之间的表面磁对流特性。由于通量管对流塌陷效率降低，M矮星在中等场强的单极区域缺乏明亮的磁结构。速度和磁场之间的空间相关性以及磁性结构的寿命及其相对于颗粒的尺寸沿着恒星类型的模型序列显着变化。
ContextThe convective envelopes of cool main-sequence stars harbour magnetic fields with a complex global and local structure. These fields affect the near-surface convection and the outer stellar atmospheres in many ways and are responsible for the observable magnetic activity of stars.AimsOur aim is to understand the local structure in unipolar regions with moderate average magnetic flux density. These correspond to plage regions covering a substantial fraction of the surface of the Sun (and likely also the surface of other Sun-like stars) during periods of high magnetic activity.MethodsWe analyse the results of 18 local-box magnetohydrodynamics simulations covering the upper layers of the convection zones and the photospheres of cool main-sequence stars of spectral types F to early M. The average vertical field in these simulations ranges from 20 to 500 G.ResultsWe find a substantial variation of the properties of the surface magnetoconvection between main-sequence stars of different spectral types. As a consequence of a reduced efficiency of the convective collapse of flux tubes, M dwarfs lack bright magnetic structures in unipolar regions of moderate field strength. The spatial correlation between velocity and the magnetic field as well as the lifetime of magnetic structures and their sizes relative to the granules vary significantly along the model sequence of stellar types.