ON THE THEORY OF ELECTROMAGNETIC INDUCTION IN THE EARTH BY OCEAN CURRENTS
ON THE THEORY OF ELECTROMAGNETIC INDUCTION IN THE EARTH BY OCEAN CURRENTS
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DOI：
10.1029/jb088ib04p03531
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发表时间：
1983-01-01
影响因子：
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通讯作者：
CHAVE, AD
中科院分区：
文献类型：
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作者：
CHAVE, AD
将电磁感应理论推广到必须显式考虑驱动电流的情况。从麦克斯韦方程的准静态形式直接导出了独立极向磁(PM)和环向磁(TM)模的微分方程组。通过推导恒定深度海洋中两个模式的格林函数，将它们应用于海洋中运动源场的感应。PM和TM模式作为海洋速度场动力学和地球电导率结构的函数，表现出非常不同的方式。TM模与水流的科里奥利力偏转和海岸线效应密切相关，海岸线效应将源流限制在洋盆内。PM模式是由完全包含在海洋中的非发散电流诱导的。详细研究了表面重力波和开尔文波。对Larsen(1968)的Kelvin波结果进行了重新评价，由于上岩石圈被模拟为绝缘体，因此忽略了TM模，导致了其磁感值的显著误差。TM模磁场对岩石圈电导率的敏感性表明，利用潮汐感应电磁场探测地球的电导率结构。
The theory of electromagnetic induction is extended to the case where the driving electric currents must be considered explicitly. Differential equations for independent poloidal magnetic (PM) and toroidal magnetic (TM) modes are derived directly from the governing quasistatic form of the Maxwell equations. They are applied to induction by motional source fields in the ocean by deriving Green functions for the two modes in a constant depth ocean. PM and TM modes are shown to behave in very different ways as a function both of the ocean velocity field dynamics and of the electrical conductivity structure of the earth. TM modes are closely associated with the Coriolis force deflection of water currents and with coastline effects that limit the source currents to the ocean basin. PM modes are induced by nondivergent electric currents that are fully contained within the ocean. Surface gravity waves and a Kelvin wave are examined in detail. The Kelvin wave result of Larsen (1968) is reevaluated, and because the upper lithosphere was modeled as an insulator, significant errors in his magnetic induction values, caused by neglect of the TM mode, are revealed. The sensitivity of the TM mode magnetic field to lithospheric electrical conductivity suggests the use of tidal induced electromagnetic fields to probe the earth's conductivity structure.