A defining characteristic of the recent geomagnetic field is its dominant axial dipole which provides its navigational utility and dictates the shape of the magnetosphere. Going back through time, much less is known about the degree of axial dipole dominance. Here we use a substantial and diverse set of 3D numerical dynamo simulations and recent observation-based field models to derive a power law relationship between the angular dispersion of virtual geomagnetic poles at the equator and the median axial dipole dominance measured at Earth’s surface. Applying this relation to published estimates of equatorial angular dispersion implies that geomagnetic axial dipole dominance averaged over 10⁷–10⁹ years has remained moderately high and stable through large parts of geological time. This provides an observational constraint to future studies of the geodynamo and palaeomagnetosphere. It also provides some reassurance as to the reliability of palaeogeographical reconstructions provided by palaeomagnetism.

最近的地磁场的一个主要特征是其主要的轴向偶极子，这提供了它的导航作用并决定了磁层的形状。时光倒流，人们对轴向偶极子支配度的了解还很少。在这里，我们使用大量多样的3D数值发电机仿真和最近的基于观测的场模型来得出在赤道处虚拟地磁极的角弥散与在地球表面测得的中位轴向偶极子优势之间的幂律关系。将这种关系应用于已发布的赤道角色散估计值意味着，地磁轴向偶极子支配力平均超过10 ⁷ –10 ⁹在大部分地质时期中，多年以来一直保持较高水平并保持稳定。这为大地发电机和古大气圈的未来研究提供了观测约束。它也为古磁性提供的古地理重建的可靠性提供了一定的保证。