Reassessment of electromagnetic core-mantle coupling and its implications to the Earth’s decadal polar motion

作     者：Weijia Kuang Benjamin F.Chao Jianli Chen 

作者机构：Geodesy and Geophysics LaboratoryNASA Goddard Space Flight CenterGreenbeltMD20771USA Institute of Earth SciencesAcademia SinicaTaipeiTaiwanROC Center for Space ResearchUniversity of TexasAustinUSA 

出 版 物：《Geodesy and Geodynamics》 (大地测量与地球动力学（英文版）)

年 卷 期：2019年第10卷第5期

页      面：356-362页

学科分类：070904[理学-构造地质学] 0709[理学-地质学] 07[理学] 

基　　金：supported by NASA Earth Surface and Interior (ESI) Program (W.K.and J.C.) NASA Geomagnetic Infrastructure Fund NASA GSFC SEEC Fund (W.K.) NASA GRACE Project (J.C.) Taiwan Ministry of Science and Technology via grant 106-2116-M-001-013(B. F. Chao) NASA GSFC fellowship program IES of Academia Sinica for support of visiting tenure 

主　　题：Polar motion Electromagnetic core-mantle coupling Geomagnetic field Geodynamo 

摘      要：The observed Earth’s polar motion on decadal time scales has long been conjectured to be excited by the exchange of equatorial angular momentum between the solid mantle and the fluid outer core,via the mechanism of electromagnetic(EM)core-mantle ***,past estimations of the EM coupling torque from surface geomagnetic observations is too weak to account for the observed decadal polar *** recent estimations from numerical geodynamo simulations have shown the *** this paper,we re-examine in detail the EM coupling mechanism and the properties of the magnetic field in the electrically conducting lower mantle(characterized by a thin D -layer at the base of the mantle).Our simulations find that the toroidal field in the D -layer from the induction and convection of the toroidal field in the outer core could be potentially much stronger than that from the advection of the poloidal field in the outer *** former,however,cannot be inferred from geomagnetic observations at the Earth’s surface,and is missing in previous EM torque estimated from geomagnetic *** deduction suggests further that this field could make the actual EM coupling torque sufficiently strong,at approximately 5×1019 Nm,to excite,and hence explain,the decadal polar motion to magnitude of approximately 10 mas.