Detection of the electromagnetic field induced by the wake of a ship moving in a moderate sea state of finite depth

Abstract

The wake of a ship and ambient sea waves induce disturbances in the Earth’s geomagnetic field. Numerical simulations are used to examine the feasibility of detecting these disturbances for moderate sea states. It is assumed that the electromagnetic disturbances are sampled by an air-borne magnetometer moving steadily along a rectilinear path. Spectral analysis of the samples is performed. Numerical simulations indicate that the magnetic field induced by the noisy sea environment and that by the wake of a moving ship have different spectral characteristics. Typically, the peak of the body-induced magnetic-field spectrum is located in the range of frequencies where the corresponding value of the wind wave’s spectrum is less significant. It is illustrated that the feasibility of electromagnetic detection of a ship’s wake depends strongly on the ship’s depth-based Froude number.