MAGNETIC STRUCTURE OF RAPIDLY ROTATING FK COMAE-TYPE CORONAE
MAGNETIC STRUCTURE OF RAPIDLY ROTATING FK COMAE-TYPE CORONAE
复制标题
快速旋转FK彗星型冕的磁结构
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
T. Gombosi
中科院分区：
文献类型：
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作者：
O. Cohen;J. Drake;V. Kashyap;H. Korhonen;D. Elstner;T. Gombosi
我们用磁流体力学模型对FK Com类型快速旋转的G巨星的日冕进行了三维模拟，该模型最初是为日冕而开发的，目的是为了捕捉到更真实的非势日冕结构。我们用FK Com系统的恒星发电机模型得到的径向磁场的表面图来驱动模拟。这使我们能够获得代表不同时间段的不同场拓扑的日冕结构。我们发现，这样一颗类FK Com恒星的日冕，包括大尺度的日冕环，是由一个很强的环向磁场分量主导的。这是由于部分磁场被径向外流拖曳，而另一部分仍然附着在快速旋转的恒星表面上。磁场的这种缠绕，除了径向流动分量的减少外，还导致日冕内部气体密度分布随距离变平。三维模拟提供了日冕结构的全局视图。结果的某些方面，如磁场的环形包裹，一般也应该适用于快速自转上的日冕，我们的研究表明，这可能与研究得很好、观测得很好的日冕有很大的不同。研究这种日冕的全球结构还应有助于更好地了解它们的相关恒星过程，如耀斑和日冕物质抛射，尤其应有助于更好地了解此类系统的质量损失和角动量损失。
We present a three-dimensional simulation of the corona of an FK Com-type rapidly rotating G giant using a magnetohydrodynamic model that was originally developed for the solar corona in order to capture the more realistic, non-potential coronal structure. We drive the simulation with surface maps for the radial magnetic field obtained from a stellar dynamo model of the FK Com system. This enables us to obtain the coronal structure for different field topologies representing different periods of time. We find that the corona of such an FK Com-like star, including the large-scale coronal loops, is dominated by a strong toroidal component of the magnetic field. This is a result of part of the field being dragged by the radial outflow, while the other part remains attached to the rapidly rotating stellar surface. This tangling of the magnetic field, in addition to a reduction in the radial flow component, leads to a flattening of the gas density profile with distance in the inner part of the corona. The three-dimensional simulation provides a global view of the coronal structure. Some aspects of the results, such as the toroidal wrapping of the magnetic field, should also be applicable to coronae on fast rotators in general, which our study shows can be considerably different from the well-studied and well-observed solar corona. Studying the global structure of such coronae should also lead to a better understanding of their related stellar processes, such as flares and coronal mass ejections, and in particular should lead to an improved understanding of mass and angular momentum loss from such systems.