Planetary Core‐Style Rotating Convective Flows in Paraboloidal Laboratory Experiments
Planetary Core‐Style Rotating Convective Flows in Paraboloidal Laboratory Experiments
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DOI：
10.1029/2022je007356
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
T. L. Lonner;Ashna Aggarwal;J. Aurnou
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文献类型：
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作者：
T. L. Lonner;Ashna Aggarwal;J. Aurnou
这里使用热驱动的自由表面抛物面实验室环来模拟行星外核中的湍流对流。我们表明，自由表面抛物面环中的快速旋转对流动力学与行星球壳几何形状中的快速旋转对流动力学相似。三个实验案例分别以每分钟 35 转 (rpm)、50 和 60 rpm 的转速进行。在流体自由表面的全盘热成像图像中检测到热罗斯贝波。超声波流速测量揭示了多个方位（区域）射流的存在，在较高旋转速率的情况下逐渐形成更多的射流。喷流的圆柱形径向范围与莱茵河尺度非常接近。随着时间的推移，纬向射流迁移到更大的径向位置，迁移速率与先前的理论估计非常一致。我们的结果表明，行星核心旋转对流将由其他湍流地球物理流体动力系统中发现的流动结构组成：对流湍流在小尺度流场中占主导地位，并且还将能量流入更大规模、缓慢演化的层流结构。行星核心环境中的环境磁场如何影响这种湍流仍然是一个悬而未决的问题。
Turbulent convection in a planet's outer core is simulated here using a thermally‐driven, free surface paraboloidal laboratory annulus. We show that the rapidly rotating convection dynamics in free‐surface paraboloidal annuli are similar those in planetary spherical shell geometries. Three experimental cases are carried out, respectively, at 35 revolutions per minute (rpm), 50 and 60 rpm. Thermal Rossby waves are detected in full disk thermographic images of the fluid's free surface. Ultrasonic flow velocity measurements reveal the presence of multiple azimuthal (zonal) jets, with successively more jets forming in higher rotation rate cases. The jets' cylindrical radial extent is well approximated by the Rhines scale. Over time, the zonal jets migrate to larger radial position with migration rates in good agreement with prior theoretical estimates. Our results suggest that planetary core rotating convection will be comprised of flow structures found in other turbulent geophysical fluid dynamical systems: convective turbulence dominates the small‐scale flow field, and also act to flux energy into larger‐scale, slowly evolving zonal flow structures. How the ambient magnetic fields in planetary core settings affect such turbulent flows remains an open question.