Three-dimensional simulations of near-surface convection in main-sequence stars III. The structure of small-scale magnetic flux concentrations (cid:2)
Three-dimensional simulations of near-surface convection in main-sequence stars III. The structure of small-scale magnetic flux concentrations (cid:2)
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 (cid:2)
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
M. Schüssler
中科院分区：
文献类型：
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作者：
B. Beeck;R. Cameron;A. Reiners;M. Schüssler
上下文冷的主序星的对流包层包含具有复杂的全局和局部结构的磁场。这些磁场在许多方面影响着近地表对流和外部恒星大气，并对可观测到的恒星磁场活动负责。目标。我们的目标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相当大一部分（也可能是其他类太阳恒星的表面）的谱斑区域。方法.我们分析了18个局部箱磁流体动力学模拟的结果，覆盖了对流区的上层和光谱类型为F到早期M的冷主序星的光球。这些模拟中的平均垂直场范围从20到500 G。结果我们发现不同光谱类型的主序星之间的表面磁对流性质有很大的变化。由于质子束管对流坍缩的效率降低，M矮星在中等场强的单极区域缺乏明亮的磁性结构。速度和磁场之间的空间相关性，以及磁结构的寿命和它们相对于颗粒的大小，都沿着恒星类型的模型序列有着显著的变化。
Context. The convective envelopes of cool main-sequence stars harbour magnetic fields with a complex global and local structure. These fields a ff ect the near-surface convection and the outer stellar atmospheres in many ways and are responsible for the observable magnetic activity of stars. Aims. Our 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. Methods. We 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. Results. We find a substantial variation of the properties of the surface magnetoconvection between main-sequence stars of di ff erent spectral types. As a consequence of a reduced e ffi ciency 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.