核幔耦合对地球自由核章动的激发影响  

Influence of core-mantle coupling on the excitation of free core nutation

作　　者：崔小明[1] 孙和平 徐建桥[1] 周江存[1] 陈晓东[1] CUI XiaoMing;SUN HePing;XU JianQiao;ZHOU JiangCun;CHEN XiaoDong(State Key Laboratory of Geodesy and Earth′s Dynamics,Institute of Geodesy and Geophysics, Chinese Academy of Sciences,Wuhan 430077,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院测量与地球物理研究所大地测量与地球动力学国家重点实验室,武汉430077 [2]中国科学院大学,北京100049

出　　处：《地球物理学报》2018年第9期3584-3591,共8页Chinese Journal of Geophysics

基　　金：国家重点基础研究发展计划(2014CB845902);国家自然科学基金(41321063;41304058;41774092;41374084和41574072)共同资助

摘　　要：地球自由核章动(FCN)是地幔与液核相互作用的重要动力学现象,其激发机制涉及地表流体层、地幔和地核等圈层之间的耦合,此前研究多利用地表流体层角动量数据单独研究其对FCN的激发,对核幔耦合的影响考虑不足.本文基于角动量守恒理论分析了核幔耦合对FCN周期及振幅的影响,并结合多个大气及海洋角动量函数时间序列首次估算了核幔耦合在FCN激发过程中的贡献.结果表明核幔耦合对FCN周期产生的固定和时变影响对FCN激发的作用均不可忽视,尤其时变影响可达几十个微角秒,对于进一步解释FCN时变特征非常重要;核幔耦合对FCN振幅的直接影响是地表流体层的激发与实测FCN不相符的主要原因,黏滞、电磁和地形等耗散耦合的存在对地表流体的激发振幅有67%左右的减弱效果.The Earth′s free core nutation(FCN)is an important dynamic phenomenon of the interaction between the mantle and liquid core.Its excitation mechanism involves coupling between surface fluid layers,mantle and core.Previous studies have used the angular momentum functions of surface fluids alone to study the excitation of FCN,and the impact of the core-mantle couplings was not considered.Based on the theory of conservation of angular momentum,this paper analyzes the influence of core-mantle coupling on the period and amplitude of FCN,and firstly estimates the contributions of core-mantle coupling in the FCN excitation process according to multiple atmospheric and oceanic angular momentum function time series.The results indicate that the fixed and time-varying effects of core-mantle coupling on the FCN excitation cannot be ignored,especially the time-varying effect can reach dozens of microarcseconds,which is very important for further explaining the time-varying characteristics of FCN signal;The direct influence of the core-mantle coupling on the FCN amplitude is supposed to be the main reason that the excitation of the surface fluid layer is inconsistent with the observed FCN signal.The existence of viscous,electromagnetic and topographic coupling has about an attenuation effect by about 67%on the excitation of the surface fluid.

关 键 词：自由核章动 核幔耦合 地表流体层 激发 

分 类 号：P227[天文地球—大地测量学与测量工程]