天体球的MHD激波结构：类造父星球$λ$
MHD-shock structures of astrospheres: $λ$ Cephei-like astrospheres
摘要：
解释最近观测到的弓形激波周围的O-星和创建相应的模型需要详细了解相关的（磁）流体动力学结构。我们的研究基于三维数值磁流体动力学模型，使用动态相关参数，特别是（磁）音速马赫数进行分析。将HD和MHD的解析Rankine-Hugoniot关系与数值模型得到的结果进行了比较。在这种情况下，我们还表明，唯一的距离，可以近似确定的是终止冲击，如果它是一个流体动力学冲击。对于MHD激波，驻点一般不位于流入线上，流入线是平行于流入矢量并穿过恒星的线。因此，如在HD情况下那样经由伯努利方程的估计通常是不可能的。我们还表明，在O-星天体层，不同的区域存在的快速，慢速，Alfvénic，和声波的马赫数变得低于一，这意味着亚慢磁声以及亚快和亚音速流。然而，解析的MHD Rankine Hugoniot关系可以用于湍流和宇宙线调制的进一步研究。
英文摘要：
The interpretation of recent observations of bow shocks around O-stars and the creation of corresponding models require a detailed understanding of the associated (magneto-)hydrodynamic structures. We base our study on three-dimensional numerical magneto-)hydrodynamical models, which are analyzed using the dynamically relevant parameters, in particular, the (magneto)sonic Mach numbers. The analytic Rankine-Hugoniot relation for HD and MHD are compared with those obtained by the numerical model. In that context we also show that the only distance which can be approximately determined is that of the termination shock, if it is a hydrodynamical shock. For MHD shocks the stagnation point does not, in general, lie on the inflow line, which is the line parallel to the inflow vector and passing through the star. Thus an estimate via the Bernoulli equation as in the HD case is, in general, not possible. We also show that in O-star astrospheres, distinct regions exist in which the fast, slow, Alfvénic, and sonic Mach numbers become lower than one, implying sub-slow magnetosonic as well as sub-fast and sub-sonic flows. Nevertheless, the analytic MHD Rankine Hugoniot relations can be used for further studies of turbulence and cosmic ray modulation.
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