The low frequency electromagnetics signatures of conducting objects in the ocean

The utility of the physical optics approximation is explored for the computation of electromagnetic fields of dipole sources in the neighborhood of conducting bodies of diverse shape in a lossy environment such as the ocean. Excellent agreement with previous exact results is obtained for spheres down to one skin depth diameter with source-detector separation up to one skin depth. Only when the sphere size is reduced to one-tenth skin depth do errors in excess of three decibels begin to appear. Such comparisons have confirmed the accuracy of the method for application to non-spherical body shapes. The computer program allows investigation of the response for orthogonally oriented source and detection dipoles in the presence of smooth, curved, conducting bodies in a homogeneous lossy medium. Results are given for spheres, infinite cylinders, prolate spheroids and super-elliptic spheroids exposed to magnetic dipole sources.