Thermal interactions between Earth’s core and mantle provide the power that maintains the geomagnetic field. However, the effect of these interactions and, in particular, the thermochemical piles at the base of the mantle on magnetic field behaviour remains uncertain. Here we present numerical dynamo simulations with strong lateral variations in heat flow imposed at the core–mantle boundary to reproduce conditions within Earth and indicate how the mantle controls core dynamics. Comparing these simulations to recent global magnetic field models, based on observational data spanning tens of thousands of years, they successfully reproduce the morphology and secular variation of Earth’s modern field and the inferred large-scale flow structure at the top of the core. These simulations reveal that the long-term geomagnetic signatures of thermal core–mantle interactions are evident in the longitudinal structure of the geomagnetic field as equatorial patches of reverse flux, rather than the high-latitude patches suggested by less Earth-like simulations. Comparison of these simulations with the field models also suggests that the amplitude of the present-day longitudinal hemispheric imbalance in secular variation is anomalously large, indicating our present-day geomagnetic field may be unusual.

地核和地幔之间的热相互作用提供了维持地磁场的能量。然而，这些相互作用的影响，特别是地幔底部的热化学堆对磁场行为的影响仍然不确定。在这里，我们提出了数值发电机模拟，在地核-地幔边界处施加了强烈的热流横向变化，以重现地球内部的条件，并表明地幔如何控制地核动力学。将这些模拟与最近的全球磁场模型进行比较，基于跨越数万年的观测数据，他们成功地再现了地球现代磁场的形态和长期变化以及推断的核心顶部的大规模流动结构。这些模拟表明，热核-地幔相互作用的长期地磁特征在地磁场的纵向结构中是明显的，作为反向通量的赤道斑块，而不是不太像地球的模拟所暗示的高纬度斑块。将这些模拟与场模型进行比较还表明，当今长期变化的纵向半球不平衡幅度异常大，表明我们今天的地磁场可能不寻常。