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Zonal flow formation in the Earth’s core

Abstract

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 ocean1. Zonal flow formation in nuclear fusion devices is also well studied2. 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.

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Figure 1: Pattern changes of the thermal convection in the rotating outer core.
Figure 2: Dual-convection structure in case j in Table 1 .
Figure 3: Convection in the outer core in case j at t = 1,140.
Figure 4: Dual-convection structure in the outer core, with the inner plume sheets and outer zonal flow, in case j at t = 1,140.

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Acknowledgements

This work was supported by KAKENHI (17540404) and The Mitsubishi Foundation.

Author Contributions T.M. was involved in running the simulations, code development, data analysis and manuscript preparation. A.K. was involved in project planning, simulation-code development, running the simulations, data analysis and manuscript preparation. T.S. was involved in project planning and manuscript preparation.

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Correspondence to Akira Kageyama.

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Miyagoshi, T., Kageyama, A. & Sato, T. Zonal flow formation in the Earth’s core. Nature 463, 793–796 (2010). https://doi.org/10.1038/nature08754

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