Investigating the Influence of the Magnetostrophic Magnetorotational Instability on the Dynamo Action in Planetary Interiors and their Exterior Field

研究磁养磁转不稳定性对行星内部及其外部场发电机作用的影响

• 批准号: 169835518
• 负责人: Professor Dr. H. Hubertus Klahr
• 金额: --
• 依托单位: Max-Planck-Institut für Astronomie (MPIA)
• 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 2013-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/169835518?language=en
• 关键词: Investigating; Influence; Magnetostrophic; Magnetorotational; Instability

A simple, modified version of the magnetorotational Instability (MRI) can, in principle, develop in the Earth’s outer liquid core if even a small amount of differential rotation is present (Petitdemange, Dormy, Balbus, GRL,35, 2008). We refer to this instability as the Magnetostrophic MRI (MS-MRI). (``Magnetostrophic’’ refers to a dominant balance between the Coriolis and Lorentz forces as the instability develops.) We have found that as angular momentum is transported outward, the MS-MRI saturates primarily by reducing the magnitude of the initial shear profile. It is therefore possible that the MS-MRI may constrain planetary shear profiles. For example, in Jupiter-like planets, the magnetic field may destabilize, and ultimately regulate, the conducting zone of this planet. We propose to extend our non-linear simulations of planetary interiors, using the PARODY code (Dormy et al. 1998), to three dimensions. We will place these simulations on an observational footing by extracting the observable features from our calculations. These include gross dynamo properties (e.g., whether dynamo activity is present in the solar system planets, the magnetic history of the earth, and whether small scale or large fields dominate), and the shapes of isorotational surfaces. Thus, this proposal is an essential part of the “synergistic interdisciplinary approach” of the Priority Program “Planetary Magnetism”, in combining a recently discovered physical effect with newly developed tools for data acquisition and analysis via computer simulations of planetary interiors and dynamos.

一个简单的，修改版本的磁旋转不稳定性（MRI），原则上，可以发展在地球的外部液体核心，即使是少量的差异旋转（Petitdemange，Dormy，Balbus，GRL，35，2008）。我们将这种不稳定性称为磁致旋转MRI（MS-MRI）。（“地转”是指随着不稳定性的发展，科里奥利力和洛伦兹力之间的主导平衡。我们已经发现，随着角动量向外传输，MS-MRI饱和主要是通过降低初始剪切分布的幅度。因此，MS-MRI可能会限制行星切变剖面。例如，在类木星行星中，磁场可能会破坏并最终调节行星的传导带。我们建议扩展我们的行星内部的非线性模拟，使用的PARODY代码（Dormy等。1998），三维。我们将通过从计算中提取可观察的特征，将这些模拟置于观察的基础上。这些包括总发电机特性（例如，发电机活动是否存在于太阳系行星中，地球的磁历史，以及是小尺度还是大磁场占主导地位），以及等旋面的形状。因此，这项建议是优先方案“行星磁性”的“协同跨学科方法”的一个重要组成部分，将最近发现的物理效应与新开发的通过计算机模拟行星内部和发电机进行数据采集和分析的工具相结合。