Energy Evolution of the Ocean Wave Spectrum and Distribution of the Induced magnetic Field Intensity

The performance of marine electromagnetic detection is significantly affected by the ambient electromagnetic noise in the ocean, among which the magnetic field induced by ocean waves moving through the Earth's magnetic field constitutes a core noise source. To further investigate the formation mechanism, distribution characteristics, and patterns of this wave-induced magnetic field, this study employs the Pierson-Moskowitz wave spectrum combined with the Weaver's electromagnetic theory framework. The dynamic characteristics of a two-dimensional sea surface under varying wind speeds were simulated using the Monte Carlo random sampling method, and the wave-induced magnetic field was formulated analytically via Maxwell's equations. The research focus was to simulate the three-dimensional spatial distribution and spectral properties of the induced magnetic field under different wind scenarios. Simulation results indicate that as wind speed increases, wave evolution progresses from a low-amplitude, underdeveloped state to a complex and fully developed condition. Concurrently, the magnetic induction intensity exhibits a positive correlation with wave activity. Spectrally, the induced magnetic field demonstrates a narrowband concentration characteristic. With increasing wind speed, the dominant frequency shifts towards the lower frequency domain, accompanied by energy aggregation near the primary frequency. In the frequency band below the dominant frequency, the magnetic field intensity increases approximately linearly with frequency, while in the band above the dominant frequency, it decays exponentially with increasing frequency. The findings of this study provide theoretical and simulation support for noise modeling and signal extraction in the field of marine electromagnetic detection.