Studies of geomagnetic variations using 3D mean-field dynamo models based on spectral filtering

地磁主场的变化，如漂移、漂移或反转，反映了地核运动的复杂性。这些变化的观察特征应该建立在对地核发电机过程的充分详细模拟的基础上，该过程包括磁场与由热或其他不稳定引起的流体运动的非常复杂的相互作用。尽管在这方面取得了令人印象深刻的进展，但对这些过程的模拟仍然缺乏对这些过程的模拟，这些过程的材料参数真正接近地核的参数。我们的项目旨在更简单的平均场发电机模型水平上研究地球发电机的时间行为。然而，使用了一个新的平均场概念，平均场是通过过滤原始场的多极子谱来定义的。它避免了传统概念的缺点，传统概念的应用使其在地核的应用相当成问题。在我们的模型中，使用了源自模拟的对流运动模式，这些条件对于假设地核的情况是现实的。我们期望这项拟议工作的主要结果是有助于理解地磁场的时间变化及其与地核流体运动的联系。

The variations of the geomagnetic main field such as drifts, excursions or reversals reflect the complex nature of the motions in the Earth's core. The observed features of these variations should be understood on the basis of sufficiently detailed simulations of the dynamo process in the Earth's core, which consists in very complex interactions of the magnetic field with fluid motions caused by thermal or other instabilities. Despite very impressive progress in this respect, simulations of these processes with material parameters really close to those of the Earth's core are still missing. Our project aims to study the time behavior of the geodynamo on the simpler level of mean-field dynamo models. However, a new mean-field concept is used, with mean fields defined by filtering of the multipole spectra of the original fields. It avoids shortcomings of the traditional concept, which made its application to the Earth's core rather problematic. In our models patterns of the convective motions are used originating from simulations under conditions which are realistic for the situation to be assumed in the Earth's core. The main result we expect from the proposed work is a contribution to understanding the time variations of the geomagnetic field and their connection with the fluid motions in the Earth's core.