Generation of a strong magnetic field using uniform heat flux at the surface of the core
Generation of a strong magnetic field using uniform heat flux at the surface of the core
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DOI：
10.1038/ngeo643
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发表时间：
2009-11-01
影响因子：
18.3
通讯作者：
Roberts, Paul H.
中科院分区：
文献类型：
--
作者：
Sakuraba, Ataru;Roberts, Paul H.
地球的主磁场被认为是由地球流体外核的运动产生的，这导致了类似于发电机的效应（1-3）。最近的高分辨率数值模拟只产生一个非偶极（4）或偶极但相对较弱的磁场（5，6），与地球不同。旧的模型确实产生了一个强大的，类似地球的领域需要使用不切实际的高粘度的核心流体（7-10）。大多数模型的共同点是假设横向均匀的芯-表面温度。在这里，我们使用一个低粘度的地球发电机模型来评估一个不同的和更现实的边界条件的影响，一个均匀的热通量在表面的核心模拟地球一样的磁场。我们的研究结果表明，当表面温度横向均匀，只有一个弱磁场产生，因为行星尺度的流体环流被抑制。相反，在核心的表面横向均匀的热通量导致大规模的对流，和一个比较强的偶极型磁场。与以前的工作（11，12）相反，我们认为，在核心表面的热条件对低粘度地球发电机模型有很强的影响。
The Earth's main magnetic field is thought to be generated by motions in the planet's fluid outer core, which lead to an effect similar to that of a dynamo(1-3). Recent high-resolution numerical simulations produce only a non-dipolar(4) or a dipolar but comparatively weak magnetic field(5,6) unlike that of the Earth. Older models that did generate a strong, Earth-like field needed to use unrealistically high viscosities for the core fluid(7-10). Common to most of the models is the assumption of a laterally uniform core-surface temperature. Here we use a low-viscosity geodynamo model to evaluate the effect of a different and more realistic boundary condition-a uniform heat flux at the surface of the core-on the simulation of an Earth-like magnetic field. Our results show that when the surface temperature is laterally uniform, only a weak magnetic field is generated because planetary-scale fluid circulations are suppressed. In contrast, a laterally uniform heat flux at the core's surface leads to large-scale convective flows, and a comparatively strong dipole-type magnetic field. Contrary to previous work(11,12), we suggest that thermal conditions at the core surface have a strong effect on low-viscosity geodynamo models.