Department of Earth, Ocean and Ecological Sciences, University of Liverpool, Liverpool, L69 7ZE, UK.
Department of Geological Sciences, University of Florida, PO Box 112120, Gainesville, FL, 32611-2120, USA.
Nat Commun. 2020 Nov 30;11(1):6100. doi: 10.1038/s41467-020-19794-7.
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 10-10 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.
近期地磁场的一个显著特点是其主导的轴向偶极子，这为地磁场提供了导航实用性，并决定了磁层的形状。回溯过去，人们对地磁场轴向偶极子主导程度的了解要少得多。在这里，我们使用大量多样化的三维数值发电机模拟和最近基于观测的场模型，得出了在赤道处虚拟地磁极点的角分散度与在地球表面测量到的轴向偶极子中位数主导程度之间的幂律关系。将此关系应用于已发表的赤道角分散度估计值，意味着在地壳历史的大部分时间里，10-10 年平均的地磁场轴向偶极子主导程度保持在较高且稳定的水平。这为未来的地发电机和古磁层研究提供了观测限制。这也为古磁法提供的古地理重建的可靠性提供了一些保证。
