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arXiv 1105.1271astro-ph.EP
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CoRoT-7b系外行星内部深层的物理状态

Physical State of the Deep Interior of the CoRoT-7b Exoplanet

F. W. Wagner, F. Sohl, T. Rückriemen, H. Rauer

摘要:

本研究将CoRoT-7 b系外行星作为大质量类地行星的模拟物,以调查液体核心中可以维持固有磁场的条件。我们研究了深度依赖性输运参数的影响(例如,地幔岩石的活化体积)对行星热结构的影响以及与之相关的穿过核幔边界的热通量。对于质量比地球大的类地行星,我们的计算表明,地幔最低层的很大一部分处于缓慢的对流状态,主要是由于压力对粘度的影响。因此,我们发现更高的核心温度比以前报道的参数化对流模型。我们还讨论了在杂质存在下熔点降低的影响(例如,硫),并比较相应的熔化关系计算的热结构。由于杂质效应在CoRoT-7 b内部深处普遍存在的高压和高温条件下变得不那么重要,富铁的核心可能是固体,这意味着不存在自持磁场。

英文摘要:

The present study takes the CoRoT-7b exoplanet as an analogue for massive terrestrial planets to investigate conditions, under which intrinsic magnetic fields could be sustained in liquid cores. We examine the effect of depth-dependent transport parameters (e.g., activation volume of mantle rock) on a planet's thermal structure and the related heat flux across the core mantle boundary. For terrestrial planets more massive than the Earth, our calculations suggest that a substantial part of the lowermost mantle is in a sluggish convective regime, primarily due to pressure effects on viscosity. Hence, we find substantially higher core temperatures than previously reported from parameterized convection models. We also discuss the effect of melting point depression in the presence of impurities (e.g., sulfur) in iron-rich cores and compare corresponding melting relations to the calculated thermal structure. Since impurity effects become less important at the elevated pressure and temperature conditions prevalent in the deep interior of CoRoT-7b, iron-rich cores are likely solid, implying that a self-sustained magnetic field would be absent.

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