The phase diagram of water and the magnetic fields of Uranus and Neptune
The phase diagram of water and the magnetic fields of Uranus and Neptune
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DOI：
10.1016/j.icarus.2010.08.008
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发表时间：
2011-01-01
期刊：
影响因子：
3.2
通讯作者：
French, Martin
中科院分区：
文献类型：
--
作者：
Redmer, Ronald;Mattsson, Thomas R.;French, Martin
巨行星的内部可以提供有关行星系统形成和演化过程的有价值的信息。然而，天王星和海王星的内部和演化仍然是未知的。在本文中，我们比较了这些行星的富水三层结构模型与来自磁场模型的壳结构预测。天王星和海王星具有与地球相反的不寻常的非偶极磁场。Stanley和Bloxham（Stanley，S.，Bloxham，J. [2004年]。Nature 428，151-153）已经指出，这样的磁场产生于位于富H/He外壳下方的最多0.3行星半径的相当薄的壳和流体但稳定分层的导电核中。内部模型依赖于行星材料的状态方程数据，这些材料在高压域中通常具有相当大的不确定性。我们提出的天王星和海王星的内部模型是基于从头算的氢，氦和水的状态数据方程作为所有较重的元素或冰的代表。根据水的详细高压相图，我们可以确定内包层中应存在超离子水的区域。该超离子区域与发电机模型中发现的稳定分层区域的位置密切相关。因此，我们认为水的相图对天王星和海王星磁场的产生有重大影响。(C)2010年爱思唯尔公司All rights reserved.
The interior of giant planets can give valuable information on formation and evolution processes of planetary systems. However, the interior and evolution of Uranus and Neptune is still largely unknown. In this paper, we compare water-rich three-layer structure models of these planets with predictions of shell structures derived from magnetic field models. Uranus and Neptune have unusual non-dipolar magnetic fields contrary to that of the Earth. Extensive three-dimensional simulations of Stanley and Bloxham (Stanley, S., Bloxham, J. [2004]. Nature 428, 151-153) have indicated that such a magnetic field is generated in a rather thin shell of at most 0.3 planetary radii located below the H/He rich outer envelope and a conducting core that is fluid but stably stratified. Interior models rely on equation of state data for the planetary materials which have usually considerable uncertainties in the high-pressure domain. We present interior models for Uranus and Neptune that are based on ab initio equation of state data for hydrogen, helium, and water as the representative of all heavier elements or ices. Based on a detailed high-pressure phase diagram of water we can specify the region where superionic water should occur in the inner envelope. This superionic region correlates well with the location of the stably-stratified region as found in the dynamo models. Hence we suggest a significant impact of the phase diagram of water on the generation of the magnetic fields in Uranus and Neptune. (C) 2010 Elsevier Inc. All rights reserved.