Fully determined scaling laws for volumetrically heated convective systems, a tool for assessing habitability of exoplanets
Fully determined scaling laws for volumetrically heated convective systems, a tool for assessing habitability of exoplanets
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DOI：
10.1016/j.pepi.2017.02.001
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发表时间：
2017-05-01
影响因子：
2.3
通讯作者：
Kaminski, Edouard
中科院分区：
文献类型：
--
作者：
Vilella, Kenny;Kaminski, Edouard
一颗行星的长期可居住性取决于它通过部分融化和火山活动产生和维持大气层的能力。这个问题主要是在板块构造的框架下解决的，这可能过于具体，不适用于广泛的内部动力学预期的系外行星，甚至早期地球的热演化。在这里，我们提出了一个更一般的对流理论方法，建立一个制度图，给出部分熔化发生的条件，在行星体，作为一个函数的关键参数，可以估计为系外行星，它们的大小和内部加热速率。为了这个目的，我们介绍了一个精致的视图中的热边界层（TBL）从内部加热的对流系统，其重点是温度和厚度的TBL在顶部的最热的温度分布，沿着部分熔化应首先发生。这种“最热的热边界层”（HotTBL）的特点是首先使用完全理论的比例定律的基础上的动态热边界层。这些法律是第一个在文献中提出的，不依赖于经验确定的无量纲常数，适用于低瑞利和高瑞利对流制度。我们表明，尺度定律可以成功地应用到行星机构的预测比较完整的数值模拟月球。然后，我们使用的比例定律，建立一个制度图系外行星。结合对系外行星内部加热的估计，状态图预测，在可居住区，比地球年轻的行星会发生部分熔化。(C)2017爱思唯尔B.V.保留所有权利。
The long-term habitability of a planet rises from its ability to generate and maintain an atmosphere through partial melting and volcanism. This question has been mainly addressed in the framework of plate tectonics, which may be too specific to apply to the wide range of internal dynamics expected for exoplanets, and even to the thermal evolution of the early Earth. Here we propose a more general theoretical approach of convection to build a regime diagram giving the conditions for partial melting to occur, in planetary bodies, as a function of key parameters that can be estimated for exoplanets, their size and internal heating rate. To that aim, we introduce a refined view of the Thermal Boundary Layer (TBL) in a convective system heated from within, that focuses on the temperature and thickness of the TBL at the top of the hottest temperature profiles, along which partial melting shall first occur. This "Hottest Thermal Boundary Layer" (HotTBL) is first characterized using fully theoretical scaling laws based on the dynamics of thermal boundary layers. These laws are the first ones proposed in the literature that do not rely on empirical determinations of dimensionless constants and that apply to both low Rayleigh and high Rayleigh convective regimes. We show that the scaling laws can be successfully applied to planetary bodies by comparing their predictions to full numerical simulations of the Moon. We then use the scaling laws to build a regime diagram for exoplanets. Combined with estimates of internal heating in exoplanets, the regime diagram predicts that in the habitable zone partial melting occurs in planets younger than the Earth. (C) 2017 Elsevier B.V. All rights reserved.