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地震观测表明:在过去30～50年间,内核比地幔的旋转速率要快。这种差异旋转能在地幔上产生巨大的重力转矩。如果不能被其他转矩平衡,那么随着地幔旋转速率的变化,这种重力转矩应当能被检测到。我们对比了内核旋转的地震估计和由日长(LOD)观测结果通过重力耦合模型反演出来的估计。模型预测取决于几个参数,但对参数值的期望范围,相对旋转的地震估计至少要比由日长数据预测的大一个数量级。此外,在过去30～50年间的日长数据预测了内核与地幔角准线的振荡,而地震数据似乎要求有稳定旋转的分量。我们认为内核的稳定旋转导致作用在地幔上一个稳定的转矩。由于这种转矩并不对地幔旋转速率起加速作用,因此,它需要有另一种相反的转矩来平衡。这一所需的转矩与由于地核顶部的西向流动而在幔基上产生的摩擦电磁应力是一致的。
Seismic observations show that in the past 30 to 50 years, the core rotates faster than the mantle. This differential rotation produces a huge gravitational torque on the mantle. If this can not be balanced by other torques, this gravitational torque should be detectable as the rate of mantle rotation changes. We compare the estimates of core rotation earthquake estimates and those derived from the LOD observations through the gravity coupling model. The model predictions depend on several parameters, but for the expected range of parameter values, the relative rotation is estimated to be at least an order of magnitude larger than predicted by the Japanese long-run data. In addition, the long-term data over the past 30 to 50 years predicted the oscillation of the core and mantle-quark corners, whereas the seismic data appeared to require a steady-rotating component. We believe that a steady rotation of the core results in a steady torque acting on the mantle. Since this torque does not accelerate the mantle’s spin rate, it needs another counter-torque to balance it. This required torque is consistent with the tribological electromagnetic stress generated on the mantle base due to the westward flow at the top of the core.