作用在椭球地幔上的扭转Alfvén模的压力矩
Pressure torque of torsional Alfvén modes acting on an ellipsoidal mantle
摘要：
我们研究了在快速旋转的行星核中，磁流体动力学模式引起的流体核和固体地幔之间的压力扭矩。一个二维简化模型的核心流体动力学的发展，以考虑非球形的核幔边界。这种准地转模式的简化是建立在流体速度沿旋转轴的赤道分量不变性的假设上的。我们使用这个模型来调查和量化的线性模式的轴向扭矩，专注于扭转Alfvén模式（TM）在一个椭球体。我们验证了这些模式的周期不依赖于旋转频率。此外，它们具有角动量，导致作用在地幔上的净压力扭矩。这个扭矩与赤道椭圆率成线性比例。我们估计，TM计算这里的地形耦合到地幔是太弱，占地球的日长的变化。
英文摘要：
We investigate the pressure torque between the fluid core and the solid mantle arising from magnetohydrodynamic modes in a rapidly rotating planetary core. A two-dimensional reduced model of the core fluid dynamics is developed to account for the non-spherical core-mantle boundary. The simplification of such a quasi-geostrophic model rests on the assumption of invariance of the equatorial components of the fluid velocity along the rotation axis. We use this model to investigate and quantify the axial torques of linear modes, focusing on the torsional Alfvén modes (TM) in an ellipsoid. We verify that the periods of these modes do not depend on the rotation frequency. Furthermore, they possess angular momentum resulting in a net pressure torque acting on the mantle. This torque scales linearly with the equatorial ellipticity. We estimate that for the TM calculated here topographic coupling to the mantle is too weak to account for the variations in the Earth's length-of-day.
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