Geodynamo a-effect from box simulations of magnetoconvection

磁对流箱模拟的地球发电机 a 效应

• 批准号: 5370119
• 负责人: Dr. Udo Ziegler
• 金额: --
• 依托单位: Leibniz-Institut für Astrophysik Potsdam (AIP)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2002
• 资助国家: 德国
• 起止时间: 2001-12-31 至 2006-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5370119?language=en
• 关键词: Geodynamo; effect; box; simulations; magnetoconvection

Employing the code NIRVANA (Ziegler 1998, 1999) a local model of weakly compressible, rotating magnetoconvection for the outer core of the Earth is developed. The d-effect correlating the turbulent electromotive force due to small-scale motions with the large-scale magnetic field is estimated. The d-effect is fundamental in mean-field dynamo theory and should exist in a rotating, stratified turbulent fluid. Since the density stratification in the Earth's core is much smaller than in stellar convection zones it is, however, not clear whether its magnitude is sufficiently high to allow dynamo action. The present project contributes to our understanding of the geodynamo phenomenon in that it provides a parametrization of the d-effect on the strength of the mean magnetic field and on the position given by the latitudinal angle the Cartesian computational box is placed tangentially on the sphere. The characteristic properties of the geodynamo d-effect (amplitude, anisotropy, quenching behavior) are investigated. Strong magnetic fields are considered consistent with the idea of a magnetically-dominated outer core.

采用 NIRVANA 代码（Ziegler 1998，1999），开发了地球外核的弱可压缩旋转磁对流局部模型。估计了小尺度运动引起的湍流电动势与大尺度磁场相关的 d 效应。 d 效应是平均场发电机理论的基础，应该存在于旋转、分层的湍流流体中。然而，由于地核中的密度分层比恒星对流区小得多，因此尚不清楚其大小是否足够高以允许发电机作用。本项目有助于我们理解地球发电机现象，因为它提供了对平均磁场强度的 d 效应的参数化，以及对笛卡尔计算盒切向放置在球体上的纬度角给出的位置的参数化。研究了地球发电机 d 效应的特性（振幅、各向异性、淬火行为）。强磁场被认为与磁主导外核的想法一致。