Effects of Density Stratification on Convective Turbulence and Dynamo Action

密度分层对对流湍流和发电机作用的影响

• 批准号: 169802547
• 负责人: Dr. Stephan Stellmach
• 金额: --
• 依托单位: Institut für Geophysik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/169802547?language=en
• 关键词: Effects; Density; Stratification; Convective; Turbulence

The magnetic fields of the planets in our solar system are generated by turbulent convective flows in the planetary interiors. In most numerical simulations of this process the convection is modelled in the framework of the Boussinesq approximation. Typically, the density field however varies considerably with radius in planetary dynamo regions. Such background density variations have a large impact on the interior flow dynamics and are completely neglected in Boussinesq models. We plan to study the effects of density stratification on turbulent magnetohydrodynamic convection in an anelastic framework which filters out fast time scales caused by sound waves. Compared to a simple Boussinesq approach, anelastic models allow for additional dynamical effects like fluid expansion and contraction, weakening of the Taylor-Proudman Theorem by local fluid compression, generation of mean flows by a local mechanism independent of boundary effects and magnetic buoyancy instabilities. In contrast to global simulations targeted at reproducing observable features of planetary magnetic fields as closely as possible, our approach is aimed at investigating the details of (magneto)-convective turbulence in small sub-sections of the global domain, thus channelling all available computational resources into the numerical resolution of highly turbulent states. Different from previous studies which have been carried out in the context of solar applications, we will focus on flows which are strongly influenced by rotation. Methodically, we will use a mixed pseudo-spectral, finite-difference code well adapted to massively parallel computers. We believe that the proposed work will provide new results applicable to dynamos in terrestrial planets, gas and ice giants as well as to rapidly rotating stars.

太阳系中行星的磁场是由行星内部的湍流对流产生的。在该过程的大多数数值模拟中，对流都是在 Boussinesq 近似的框架中建模的。然而，通常情况下，行星发电机区域的密度场随半径变化很大。这种背景密度变化对内部流动动力学有很大影响，并且在 Boussinesq 模型中完全被忽略。我们计划在滞弹性框架中研究密度分层对湍流磁流体动力对流的影响，该框架滤除声波引起的快速时间尺度。与简单的 Boussinesq 方法相比，滞弹性模型允许额外的动力学效应，例如流体膨胀和收缩、通过局部流体压缩削弱泰勒-普劳德曼定理、通过独立于边界效应和磁浮力不稳定性的局部机制生成平均流。与旨在尽可能重现行星磁场的可观测特征的全局模拟相反，我们的方法旨在研究全局域小部分中（磁）对流湍流的细节，从而引导所有可用的计算资源进入高度湍流状态的数值分辨率。与之前在太阳能应用背景下进行的研究不同，我们将重点关注受旋转强烈影响的流动。我们将有条不紊地使用非常适合大规模并行计算机的混合伪谱有限差分代码。我们相信，拟议的工作将提供适用于类地行星、气体和冰巨星以及快速旋转恒星的发电机的新结果。