Japan Agency for Marine-Earth Science and Technology, Yokohama, 236-0001, Japan.
Nature. 2010 Feb 11;463(7282):793-6. doi: 10.1038/nature08754.
Zonal jets are very common in nature. Well-known examples are those in the atmospheres of giant planets and the alternating jet streams found in the Earth's world ocean. Zonal flow formation in nuclear fusion devices is also well studied. A common feature of these zonal flows is that they are spontaneously generated in turbulent systems. Because the Earth's outer core is believed to be in a turbulent state, it is possible that there is zonal flow in the liquid iron of the outer core. Here we report an investigation at the current low-viscosity limit of numerical simulations of the geodynamo. We find a previously unknown convection regime of the outer core that has a dual structure comprising inner, sheet-like radial plumes and an outer, westward cylindrical zonal flow. We numerically confirm that the dual-convection structure with such a zonal flow is stable under a strong, self-generated dipole magnetic field.
带状流在自然界中非常常见。著名的例子有巨行星大气层中的带状流和地球世界海洋中交替出现的喷射流。核聚变装置中的带状流形成也得到了很好的研究。这些带状流的一个共同特点是它们在湍流系统中自发产生。由于外核被认为处于湍流状态，因此在外核的液态铁中可能存在带状流。在这里，我们报告了在地球动力学数值模拟的当前低粘度极限下的一项研究。我们发现了一种以前未知的外核对流模式，它具有双层结构，包括内部的片状径向羽流和外部的向西的圆柱状带状流。我们通过数值模拟证实，在一个强的、自生成的偶极磁场下，具有这种带状流的双重对流结构是稳定的。
