Mercury's anomalous magnetic field caused by a symmetry-breaking self-regulating dynamo
Mercury's anomalous magnetic field caused by a symmetry-breaking self-regulating dynamo
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由对称破缺的自调节发电机引起的水星异常磁场
DOI：
10.1038/s41467-018-08213-7
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发表时间：
2019
影响因子：
16.6
通讯作者：
Hideo Tsunakawa
中科院分区：
文献类型：
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作者：
Futoshi Takahashi;Hisayoshi Shimizu;Hideo Tsunakawa
水星不同寻常的轴对称、轴向偏移的偶极磁场的发现揭示了行星磁场的一个新机制。尽管已经提出了一些奇异的模型，但偏移偶极子的原因仍有待解决。破译水星为什么有这样一个异常场不仅对于理解行星的内部动力学，进化历史和起源至关重要，而且对于建立一般发电机理论也至关重要。在这里，我们提出了数值发电机模型，核心对流驱动的热成分，双扩散对流包围热稳定分层。我们表明，目前的模型产生的磁场相似的形态和强度的水星。发电机产生的磁场作用于气流，迫使赤道对称分量和反对称分量之间相互作用，导致南北不对称螺旋度。这种破坏水星的磁反馈导致水星流产生并维持水星轴向偏移的偶极场。
The discovery of Mercury’s unusually axisymmetric, anomalously axially offset dipolar magnetic field reveals a new regime of planetary magnetic fields. The cause of the offset dipole remains to be resolved, although some exotic models have been proposed. Deciphering why Mercury has such an anomalous field is crucial not only for understanding the internal dynamics, evolutionary history and origin of the planet, but also for establishing the general dynamo theory. Here we present numerical dynamo models, where core convection is driven as thermo-compositional, double-diffusive convection surrounded by a thermally stably stratified layer. We show that the present models produce magnetic fields similar in morphology and strength to that of Mercury. The dynamo-generated fields act on the flow to force interaction between equatorially symmetric and antisymmetric components that results in north-south asymmetric helicity. This symmetry-breaking magnetic feedback causes the flow to generate and maintain Mercury’s axially offset dipolar field.