地球物理学进展 ›› 2018, Vol. 33 ›› Issue (5): 1854-1861.doi: 10.6038/pg2018BB0442

• 固体地球物理及空间物理学(大气、行星、地球动力学、重磁电及地震学、地热学) • 上一篇    下一篇

核幔耦合引起的十年尺度日长变化研究

叶庆东1(),贺伟光2,毛远凤1   

  1. 1. 中国地震局第一监测中心,天津 300180
    2. 格勒诺布尔阿尔卑斯大学,格勒诺布尔 38400,法国
  • 收稿日期:2017-11-29 修回日期:2018-08-31 出版日期:2018-10-20 发布日期:2019-01-11
  • 作者简介:叶庆东,男,1984年生,工程师,博士,研究方向为微震震源参数确定与背景噪声成像.
  • 基金资助:
    中国地震局测震台网青年骨干专项(20170629);国家自然科学基金(41504073)

Study on the decadal fluctuations in length of day caused by the core-mantle couplings

YE Qing-dong1(),HE Wei-guang2,MAO Yuan-feng1   

  1. 1. The First Monitoring and Application Center, China Earthquake Administration, Tianjin 300180,China
    2. University of Grenoble Alpes, ISTerre, Grenoble 38400, France
  • Received:2017-11-29 Revised:2018-08-31 Online:2018-10-20 Published:2019-01-11

摘要:

核幔电磁耦合、地形耦合、引力耦合是影响十年尺度日长变化的主要因素.本文简要阐述了这三大耦合的机制,并收集了前人的一些资料和数据,分别估算了这三种耦合的周期、力矩幅度及可能引起的日长变化幅度.结果表明:核幔电磁耦合周期约为10.3年,力矩约为3.1×10 17 Nm,引起的日长变化幅度约为0.27 ms;核幔地形耦合的周期约为10年,力矩约为1.7×10 18 Nm,引起的日长变化幅度约为1.4 ms.引力耦合引起的日长变化是否是十年尺度的仍存在争议,采用不同内核三轴椭球模型,日长变化的周期从亚十年尺度(3.5年、4.6年)到十年尺度(18.4年)变化.由于地核与地幔相对运动状态未知,无法确切估算引力耦合的力矩,但在假定引起耦合引起的日长变化幅度为4 ms的极限情况下,引力耦合的力矩约在10 18(十年尺度)~10 19 Nm(亚十年尺度)的量级,低于前人的计算结果.

关键词: 电磁耦合, 地形耦合, 引力耦合, 十年尺度日长变化

Abstract:

Electromagnetic Core-mantle Coupling (ECC), Topographic Core-mantle Coupling (TCC) and Gravitational Core-mantle Coupling (GCC), these three types of core-mantle coupling are the main factors to influence the decadal fluctuations in the Length of Day (LOD). In this study, we make a briefly review of the three types of couplings mechanisms, and then we use the data collected in the previous study to estimate the periods and amplitudes of the three types of coupling torques, as well as the amplitudes of variation in the LOD caused by the coupling torques. The results show that the period and the torque amplitude of ECC is about 10.3 year and 3.1×10 17 Nm, respectively, which may cause the variation in the LOD about 0.27 ms. The period and the moment amplitude of TCC is about 10 year and 1.7×10 18 Nm, respectively; which lead to the variation in the LOD about 1.4 ms. Because the LOD oscillation period depends on the choice of triaxiality model for the Earth’s inner core, whether the fluctuation caused by the GCC is decadal or sub-decadal is still controversial. Based on different triaxiality model, the LOD varies between sub-decadal (3.5 and 4.6 year) and decadal (18.4) fluctuation. Due to the lack of the detailed information about the motion of the Earth’s core related to the mantle, we are not able to extract the amplitude of GCC. However, based on the assumption the upper limit of fluctuation in the LOD is no more than 4 ms, we find that the order of magnitude of the torque of GCC is about 10 18(corresponding to decadal fluctuation)~10 19 Nm (corresponding to sub-decadal fluctuation), which is less than the previous study.

Key words: electromagnetic coupling, topographic coupling, gravitational coupling, decadal fluctuation in length of day

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