The magnetic field induced by ocean swell moving in the geomagnetic field is an important electromagnetic noise in the ocean environment for magnetic anomaly detection, and it is calculated in this work accounting into the fact that the conductivities of the ocean are inhomogeneous vertically, which is ignored in the former works, and the results are verified by comparing with those obtained by the former models. The swell-induced magnetic fields at 2 locations in the ocean are calculated and analyzed based on the statistical seawater conductivity data sets and the International Geomagnetic Reference Field. Taken the model developed here as a correct reference, the error of the former model is estimated firstly, and it reveals that the error is lower in shallow water and decreases with the wave period. It is further concluded that both the amplitude and vertical distribution range of the induced magnetic field increase with the wave period. The spectra of swell-induced magnetic field calculated with ocean wave spectrum under different wind scales are evaluated, and the impact ranges of ocean wave magnetic noise are evaluated at the sensitivity of a marine magnetometer. In the end, after examining the variation of the induced magnetic field at sea surface due to the change of geomagnetic field and seawater conductivity, it reveals that the annual variation presents a clear periodic change pattern which mainly depends on the annual variation of the conductivity near the sea surface, and the amplitude of the induced magnetic field changes in strong positive correlation with the intensity of geomagnetic field. The studies in this work are significant for applications such as magnetic anomaly detection of marine targets.

海洋涌浪在地磁场中运动引起的磁场是海洋环境中磁异常探测的重要电磁噪声，本文考虑了海洋电导率垂直不均匀的情况进行计算，忽略了这一点在前人的工作中，并通过与前人模型获得的结果进行比较来验证结果。根据统计海水电导率数据集和国际地磁参考场，计算和分析了海洋中两个地点的膨胀感应磁场。以本文建立的模型为正确参考，首先估计了前模型的误差，结果表明，浅水区误差较低，且随着波浪周期的增加而减小。进一步得出结论，感应磁场的幅值和垂直分布范围均随波周期的增加而增大。评估了不同风级下海浪频谱计算的膨胀感应磁场频谱，并在海洋磁力计的灵敏度下评估了海浪磁噪声的影响范围。最后，考察了由于地磁场和海水电导率变化引起的海面感应磁场的变化，发现年变化呈现出明显的周期性变化规律，主要取决于附近电导率的年变化。海面，感应磁场的振幅变化与地磁场的强度呈强正相关。这项工作的研究对于海洋目标磁异常检测等应用具有重要意义。