标题： 地球 tangent cylinder 实验模型中的旋转对流模式 显示英文标题

标题： Regimes of rotating convection in an experimental model of the Earth's tangent cylinder

摘要： 地球的快速旋转施加了泰勒-普劳德曼约束，该约束阻碍了流体穿过称为切线圆柱体(TC)的想象圆柱面的运动，该圆柱体是通过沿旋转方向延伸固态内核的赤道周长并延伸到地核-地幔边界(CMB)而获得的。然而到目前为止，这一边界的影响力尚不清楚，这阻碍了我们对地核极地区域流动的理解。我们实验再现了TC的几何结构，其中CMB被建模为一个冷的圆柱形容器，内部有一个热的圆柱体作为固态内核。容器中装有水，以便在与地球相似的关键性和旋转约束条件下，光学映射速度场。我们发现，主要的新机制来自于容器冷侧边界附近的位势梯度，它在TC外边界驱动惯性，就像地球地核赤道区域的对流一样。TC外部的位势梯度抑制了固体圆柱体中发现的经典壁模式，而那里的惯性导致TPC在TC边界处早期破裂。即使在临界性$\Rt=191$时，流动仍主要由科里奥利力主导，但由于TC边界附近的惯性，地转湍流出现的临界性比其他情况下要低得多。随着TPC变弱，热量通过TC边界逸出越来越多。因此，由TC外部位势梯度驱动的惯性提供了一种便捷的途径来达到地转湍流，这在实验中通常难以实现。这些结果还强调了一个过程，即TC外部的对流可能控制其内部的湍流并绕过轴向热传递。最后，我们讨论了地球的条件，特别是其磁场如何改变这一过程在地球地核内的作用。 显示英文摘要

摘要： Earth's fast rotation imposes the Taylor-Proudman Constraint that opposes fluid motion across an imaginary cylindrical surface called the Tangent Cylinder (TC) obtained by extruding the equatorial perimeter of the solid inner core along the rotation direction, and up to the core-mantle boundary (CMB). To date however, the influence of this boundary is unknown and this impedes our understanding of the flow in the polar regions of the core. We reproduce the TC geometry experimentally, where the CMB is modelled as a cold, cylindrical vessel, with a hot cylinder inside it acting as the inner solid core. The vessel is filled with water so as to optically map the velocity field in regimes of criticality and rotational constraint consistent with those of the Earth. We find that the main new mechanism arises out of the baroclinicity near the cold lateral boundary of the vessel, which drives inertia at the outer boundary of the TC, as convection in the equatorial regions of the Earth's core does. The baroclinicity just outside the TC suppresses the classical wall modes found in solid cylinder and the inertia there causes an early breakup of the TPC at the TC boundary. The flow remains dominated by the Coriolis force even up to criticality $\Rt=191$, but because of inertia near the TC boundary, geostrophic turbulence appears at much lower criticality than in other settings. The heat flux escapes increasingly through the TC boundary as the TPC becomes weaker. Hence inertia driven by baroclinicity outside the TC provides a convenient shortcut to geostrophic turbulence, which is otherwise difficult to reach in experiments. These results also highlight a process whereby the convection outside the TC may control turbulence inside it and bypass the axial heat transfer. We finally discuss how Earth's conditions, especially its magnetic field may change how this process acts within the Earth's core.