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arXiv 1201.4483astro-ph.EPastro-ph.SR
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巨行星内部的新视野：双扩散对流的影响

A new vision on giant planet interiors: the impact of double diffusive convection

Jérémy Leconte, Gilles Chabrier

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Accepted for publication in Astronomy and Astrophysics
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摘要：

传统的木星和土星的内部模型是基于一个简单的假设，一个固体核心所包围的均匀的气体信封，我们推导出新的模型与不均匀分布的重元素，即梯度的组成，在这些行星。这样的成分分层阻碍了大规模对流，变成双扩散对流，产生内部的热分布，从传统上假设的绝热内部，影响这些行星的热含量和冷却历史。为了解决这个问题，我们开发了一个分层的双扩散对流的分析方法，并将这种形式主义的太阳系气态巨行星内部。这些模型满足所有观测约束，并为我们的气态巨星产生了比以前认为的大30%至60%的金属富集。这些模型还限制了行星内对流层的大小。由于重元素倾向于在气体包层内重新分布，模型预测土星和木星内部的中心核心比通常的小，后者可能没有核心。这些模型打开了一扇新的窗户，并提出了新的挑战，我们的理解巨大的（太阳和太阳系外）行星的内部结构，特别是在确定其重物质含量，一个关键的诊断行星形成理论。

英文摘要：

While conventional interior models for Jupiter and Saturn are based on the simplistic assumption of a solid core surrounded by a homogeneous gaseous envelope, we derive new models with an inhomogeneous distribution of heavy elements, i.e. a gradient of composition, within these planets. Such a compositional stratification hampers large scale convection which turns into double-diffusive convection, yielding an inner thermal profile which departs from the traditionally assumed adiabatic interior, affecting these planet heat content and cooling history. To address this problem, we develop an analytical approach of layered double-diffusive convection and apply this formalism to Solar System gaseous giant planet interiors. These models satisfy all observational constraints and yield a metal enrichment for our gaseous giants up to 30 to 60% larger than previously thought. The models also constrain the size of the convective layers within the planets. As the heavy elements tend to be redistributed within the gaseous envelope, the models predict smaller than usual central cores inside Saturn and Jupiter, with possibly no core for this latter. These models open a new window and raise new challenges on our understanding of the internal structure of giant (solar and extrasolar) planets, in particular on the determination of their heavy material content, a key diagnostic for planet formation theories.

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