Models of sub-grid scale turbulence in the Earth's core and the geodynamo

地核和地球发电机中的次网格尺度湍流模型

• 批准号: 0509893
• 负责人: Bruce Buffett
• 金额: $ 12.62万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0509893&HistoricalAwards=false
• 关键词: Models; sub; grid; scale; turbulence

Numerical models of the geodynamo have become an increasingly important tool for studying the dynamics of the Earth's core. These models have successfully reproduced important features of the Earth's magnetic field, including the dipole dominance and the episodic reversal of polarity. However, it is generally acknowledged that the models are unrealistic in many respects. All of the current models use physical parameters that are very far from Earth-like values. As a consequence, the nature of the dynamics is altered and the potential to address important geophysical questions is limited. We propose a 2-year study to improve the reliability of numerical geodynamo models by making two important departures from current approaches. First, we will employ a finite-element method, which is better suited to parallel computing than conventional spectral methods. Second, we will develop a more sophisticated method for dealing with the effects of unresolved turbulence, based on the scale-similarity model. These models will be developed and tested initially in a plane-layer dynamo model for computational efficiency. However, we plan to adapt the model geometry to the more relevant case of a spherical shell by the end of Year 1.Observations of the geomagnetic field provide a unique probe of the Earth's interior. Even the persistence of the field depends on the nature of convection in the mantle and, possibly, on the existence of plate tectonics at the surface. Better models for the geodynamo are needed to interpret the geological record and to better understand the evolutionary path that brought the Earth to its current state. The development of new research tools will open new lines of inquiry that are not currently possible.

地球发电机的数值模型已经成为研究地核动力学的一个越来越重要的工具。 这些模型成功地再现了地球磁场的重要特征，包括偶极优势和极性的幕式反转。然而，人们普遍承认，这些模式在许多方面是不现实的。目前所有的模型使用的物理参数都与类似地球的值相差甚远。因此，动力学的性质被改变，解决重要地球物理问题的潜力受到限制。 我们提出了一个为期2年的研究，以提高数值地球发电机模型的可靠性，使两个重要的偏离目前的方法。首先，我们将采用有限元方法，这是更适合于并行计算比传统的谱方法。其次，我们将发展一个更复杂的方法来处理未解决的湍流的影响，基于尺度相似模型。 为了提高计算效率，这些模型最初将在平面层发电机模型中进行开发和测试。然而，我们计划在第一年年底之前将模型几何结构调整到更相关的球壳情况。地磁场的观测提供了对地球内部的独特探测。甚至磁场的持久性也取决于地幔中对流的性质，可能还取决于地表板块构造的存在。需要更好的地球发电机模型来解释地质记录，并更好地理解将地球带到当前状态的进化路径。新的研究工具的开发将开辟目前不可能的新的调查途径。