The geomagnetic field is generated by a dynamo process in the Earth’s core and is characterized by a predominant dipole component that has been steadily decreasing in the last few centuries. The physical drivers behind the fluctuations of the geomagnetic dipole field remain poorly understood. One of the possible explanations rely on the interaction between the dipole mode and other multipole terms of the geomagnetic field. To test this hypothesis, we used two millennial scale models based on spherical harmonic fitting of paleomagnetic data, which allowed to reconstruct the geomagnetic field of the past. By performing causality and information statistical analysis, we found significant interactions between the dipole and smaller scale harmonics (quadrupole and octupole) of the geomagnetic field. In particular, both data sets agree that the spherical harmonic \(Y_2^2\) acts as a source term, whereas the axial dipole term \(Y_1^0\) consists of the term with least information loss. The results suggest a possible control of core–mantle boundary inhomogeneities on the interaction between the components of the geomagnetic field. Our results also show a net information flux from larger to smaller scales, which is compatible with a direct turbulent cascade view of the geodynamo.

地磁场由地核中的发电机过程产生，其特征是主要偶极子分量在过去几个世纪中一直在稳步下降。地磁偶极场波动背后的物理驱动因素仍然知之甚少。一种可能的解释依赖于偶极子模式与地磁场的其他多极项之间的相互作用。为了验证这一假设，我们使用了两个基于古地磁数据球谐拟合的千年比例模型，该模型可以重建过去的地磁场。通过进行因果关系和信息统计分析，我们发现地磁场的偶极子和较小尺度的谐波（四极子和八极子）之间存在显着的相互作用。特别是，\(Y_2^2\)作为源项，而轴向偶极项\(Y_1^0\)由信息损失最少的项组成。结果表明，地磁场成分之间的相互作用可能控制地核-地幔边界的不均匀性。我们的结果还显示了从较大尺度到较小尺度的净信息通量，这与地球发电机的直接湍流级联视图兼容。