A 6-year westward rotary motion in the Earth: Detection and possible MICG coupling mechanism
A 6-year westward rotary motion in the Earth: Detection and possible MICG coupling mechanism
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地球6年向西旋转运动：探测和可能的MICG耦合机制
DOI：
10.1016/j.epsl.2018.05.009
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发表时间：
2018-08-01
影响因子：
5.3
通讯作者：
Chao, Benjamin F.
中科院分区：
文献类型：
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作者：
Ding, Hao;Chao, Benjamin F.
为了寻找地球日长变化（Delta LOD）中类似于六年振荡（SYO）的周期性的地球物理解释，我们利用OSE（最优序列估计）的阵列处理技术分析了全球GPS位移和地磁数据，并找到了6年信号的明确证据，该信号表现为2阶2次扇形球谐模式（Y-22）的向西旋转传播波。基于三个数据集之间表现出一致同步性的周期、空间模式、振幅和估计相位，我们提出以下方案：地幔-内核引力（MICG）耦合引起内核的6年轴向扭转振动，受扇形Y-22密度异常或赤道椭圆率控制，在内核和（下）地幔中，其间的角动量交换表现出作为 Delta LOD 中的 SYO。它迫使压力波通过流体外核每 6 年循环 2 次，进而产生相应的 GPS 和地磁变化。我们的研究结果提供了对地球深处动力学的深入了解，并证实了下地幔大低剪切速度省的正密度异常。 (C) 2018 Elsevier B.V. 保留所有权利。
Seeking geophysical explanations for the periodic similar to six-year oscillation (SYO) previously found in the Earth's length-of-day variation (Delta LOD), we analyze the global GPS displacement and geomagnetic data using the array processing technique of OSE (Optimal Sequence Estimation), and find clear evidences of the 6-yr signals which manifest as a westward rotary propagating wave of the sectoral spherical-harmonic pattern of degree-2 order-2 (Y-22). Based on the period, the spatial pattern, and the amplitudes and the estimated phases that exhibit consistent synchronicity among the three datasets, we propose the following scenario: The mantle-inner core gravitational (MICG) coupling gives rise to a 6-yr axial torsional libration of the inner core controlled by the sectoral Y-22 density anomalies, or the equatorial ellipticities, in the inner core and the (lower) mantle, the angular momentum exchange between which manifests as the SYO in Delta LOD. It forces into action a pressure wave-2 cyclic in 6 yr through the fluid outer core, which in turn produces the corresponding GPS and geomagnetic variations. Our findings provide insight into the dynamics of the deep Earth, and corroborate a positive density anomaly for the lower-mantle Large Low-Shear-Velocity Provinces. (C) 2018 Elsevier B.V. All rights reserved.