Simulation of Ocean Wave-Generated Magnetic Field Disturbance Observed above Sea-Surface Based on Directional Spectrum

Abstract

Ocean wave have a magnetic field disturbance, caused by the motional induction of sea water moving in the steady main field of Earth. Mass experiment indicates ocean wave-generated magnetic field disturbance can be a major limitation on the performance of airborne magnetic anomaly detection. To check the character of such disturbance observed above sea-surface, a harmonic ocean wave-generated magnetic field disturbance mathematical model based on Weavers monochromatic wave-generated magnetic field model and ocean wave directional spectrum is proposed. Algorithm is presented for real-time simulation of ocean wave-generated magnetic field disturbance corresponding to the proposed mathematical model. Numerical simulations of ocean wave-generated magnetic field disturbance are sampled above sea-surface by a stationary magnetometer and an airborne magnetometer moving steadily along a rectilinear path. Spectrum analysis of the samples is performed. Simulations results indicate that the proposed harmonic ocean wave magnetic field disturbance mathematical model can well-simulate the real sea conditions. Numerical simulations also reveal that there is a Doppler frequency shift with the increase of magnetometer flight speed. Moreover, energy of the magnetic field disturbance is more dispersed and frequency band is wider with the increase of magnetometer flight speed.