Horizontal and Vertical Electric Dipoles in a Two-Layer Conducting Medium

Measurements of low-frequency magnetic fields produced by horizontal and vertical electric current dipoles in shallow seawater are compared to Weaver model estimates. A periodic chirp covering the band 20 to 500 Hz was transmitted to enable coherent detection. Transmission losses were measured over ranges exceeding 700 m between the source antennas and an underwater tri-axial magnetometer. The magnetic field amplitudes are in good agreement with the Weaver model.