| 摘要: |
| 海水是一种高电导率的流体，根据电磁感应定律，运动的海水切割地磁场会在海水中产生感应电流，从而产生感应电磁场。本文从麦克斯韦方程出发，推导出一维速度场海水运动感应电磁场偏微分方程，利用电磁场水平分量在海表面和海底面上的连续性条件，得到海水运动感应电磁场表达式，并编写了Fortran计算程序。计算了常速度海水运动感应电磁场，并与格林函数法计算结果进行了对比，两种方法的计算结果一致。计算了变速度（即海水运动速度随深度变化）海水运动感应电磁场，并讨论了海水运动周期和海底介质电导率对海水运动感应电磁场的影响。计算结果表明：海水运动周期和海底介质电导率对常速度海水运动和变速度海水运动感应电磁场都有影响，但影响程度不同。在本文所述模型和参数条件下，海水运动感应电场和感应磁场振幅分别可达6μV/m和10nT，这与海洋大地电磁响应的量级相当。因而在处理海洋大地电磁数据时，海水运动感应电磁响应是不可忽略的噪音干扰，需要采用必要的压制手段。 |
| 关键词: 一维海水运动 感应电磁场 变速度 海水运动周期 海底介质电导率 |
| DOI：10.11693/hyhz20180700186 |
| 分类号:P733.6 |
| 基金项目:青岛海洋科学与技术实验室“问海计划”项目，2017WHZZB0201号。 |
附件 |
|
| NUMERICAL SIMULATION OF THE ELECTROMAGNETIC FIELD INDUCED BY SEAWATER MOVEMENT |
|
ZHOU Chun1, LI Yu-Guo1,2, ZHANG Bao-Qiang3
|
|
1.College of Marine Geosciences, Ocean University of China, Qingdao 266100, China;2.Evaluation and Detection Technology Laboratory of Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266100, China;3.National Ocean Technology Center, Tianjin 300112, China
|
| Abstract: |
| Conductive seawater moves in the Earth's magnetic field and generates electromagnetic (EM) field variations. We derived partial differential equations of seawater movement induced EM (EMswi) field from the Maxwell equations, in which the continuous condition of tangential component of the electric and magnetic fields on both the air-sea interface and the seafloor is used. We calculated the EMswi field in constant seawater velocity model and compared the results with that obtained using the Green's function method; both agree very well. Meanwhile, we simulated the EMswi field in a variable seawater velocity model. The result shows that the EMswi responses are affected by the seawater movement period and the seafloor conductivity on different scales. It is shown that seawater movement can generate an electric potential difference of 6μV/m and a magnetic field of 10nT at the seafloor, which are almost in the same order of magnitude to the marine magnetotelluric signal. Therefore, EMswi field shall be taken into consideration in marine Magnetotelluric Sounding (MT) data processing. |
| Key words: 1D seawater movement electromagnetic field variable seawater velocity period seafloor conductivity |
