近日，美国加州大学洛杉矶分校Jonathan M. Aurnou团队研究了地球基底岩浆海洋中高能量的发电机作用。这一研究成果发表在2025年11月3日出版的《美国科学院院刊》杂志上。

前人对地幔底部早期岩浆海的电导率和热演化的研究发现，基底岩浆海（BMO）对流可能产生了古代地磁场。

通过高分辨率发电机建模的进展，研究组发现在薄的BMO类球壳中对流能够产生强磁场，包括类似于当前日场结构的轴向偶极场。然而，将他们的发电机结果与改进的热演化模型结合起来，并将行星的快速旋转考虑到使用旋转对流湍流模型，这意味着BMO不太可能产生类似地球的磁场，这一发现与古代古地磁特征的解释、地球的全球尺度动力学和长期行星演化有关。

很大的不确定性仍然存在，需要改进地球深部热过程和矿物学过程的模型，准确确定对流标度定律中的前因子，以及完全耦合的岩心-BMO发电机模拟。尽管如此，该工作强调了BMO型发电机本质上比核心型发电机需要更大的电导率和速度乘积，并且它们同样受到旋转约束，因此与非旋转估计相比，速度显著降低。

附：英文原文

Title: Energetically expensive dynamo action in Earth’s basal magma ocean

Author: Schaeffer, Nathanal, Labrosse, Stéphane, Aurnou, Jonathan M.

Issue&Volume: 2025-11-3

Abstract: Previous studies focusing on the electrical conductivity and thermal evolution of an early magma ocean at the base of Earth’s mantle have found that basal magma ocean (BMO) convection could have produced the ancient geomagnetic field. By advances in high-resolution dynamo modeling, we find that convection in a thin BMO-like spherical shell is able to sustain strong magnetic fields, including axial dipolar fields similar to current day field structure. However, integrating our dynamo results with improved thermal evolution models and taking the planet’s rapid rotation into account using rotating convective turbulence models implies that an Earth-like magnetic field was unlikely to have been generated in the BMO, a finding relevant to the interpretation of ancient paleomagnetic signatures, Earth’s global-scale dynamics, and long-term planetary evolution. Large uncertainties still remain, calling for refined models of deep Earth thermal and mineralogical processes, accurate determination of prefactors in convective scaling laws, and fully coupled core-BMO dynamo simulations. Nonetheless, our work highlights that BMO-type dynamos intrinsically require a larger product of electrical conductivity and velocity than core-type dynamos, and that they are similarly rotationally constrained, so that velocities are significantly reduced compared to nonrotating estimates.

DOI: 10.1073/pnas.2507575122

Source: https://www.pnas.org/doi/abs/10.1073/pnas.2507575122