COLLABORATIVE RESEARCH: Numerical studies of double-diffusive convection in the interior of giant planets

AST-0807672/0806431 Garaud/Radko不稳定的热梯度和稳定的成分梯度（即双扩散对流）的竞争效应在巨行星的结构和演化中起着重要作用。 它们与天王星观测到的低热通量、天王星和海王星包层的高金属丰度、木星和土星核心的侵蚀以及一些观测到的凌日系外行星的大半径有关。 在全球海洋混合的背景下进行广泛的研究是不适用的，因为在这两种情况下的控制参数之间的差异很大。 该合作项目将在相关参数范围内对双扩散对流进行最先进的三维高分辨率数值模拟，对其进行分析以提取实用的通量参数化，并修改现有的行星演化代码（CEPAM）以考虑影响。 然后，这种改进的技术将用于解决两个特定的问题：（i）修改后的热通量定律如何影响行星的热演化和结构，以及（ii）化学元素如何在其成分界面上混合。 这方面的进展将是朝着更好地理解全球各地巨行星演化迈出的宝贵一步。这项工作是地球物理学和天体物理学流体动力学之间的跨学科研究，自然会使两个学科受益，并培养一名研究生。 Radko博士出版的关于双扩散过程的专著将加强对科学界的传播。

AST-0807672/0806431Garaud/RadkoThe competing effects of destabilizing thermal gradients and stabilizing compositional gradients (i.e. double-diffusive convection) play a major role in the structure and evolution of giant planets. They relate to the low observed heat flux of Uranus, the high metallicity of the envelopes of Uranus and Neptune, the erosion of the cores of Jupiter and Saturn, and the large radii of some observed transiting exoplanets. Extensive studies in the context of global oceanic mixing are not applicable because of the wide discrepancy between the governing parameters in the two cases. This collaborative project will perform state-of-the-art three-dimensional high-resolution numerical simulations of double-diffusive convection in the relevant parameter regime, analyze them to extract practical flux parameterizations, and modify an existing planetary evolution code (CEPAM) to account for the effects. This improved technique will then be used to address two particular questions: (i) How do the revised heat flux laws affect the thermal evolution and structure of the planets, and (ii) How are chemical elements mixed across their compositional interfaces. Progress here would be an invaluable step towards a better understanding of the global evolution of giant planets everywhere.This work is interdisciplinary between geophysical and astrophysical fluid dynamics, and will naturally benefit both subjects, as well as training a graduate student. Dissemination to the scientific community will be enhanced by publication of a monograph on Double-Diffusive Processes by Dr.Radko.