Excitation of quasi-static magnetic fields with axial structure

A quasistatic magnetic field excited in air above the sea surface by a quasisteady alternating electric current flowing through an insulated conductor in water, with water serving as the return path, was found to have not a dipole structure as in the case of a closed current loop but an axial structure as in the case of a straight wire. The intensity of such a magnetic field in air, beyond the water surrounding the conductor, is determined by the current in the conductor only and does not depend on the current in water. Measurements confirm theoretical calculations very closely, that the magnetic field intensity decreases with increasing distance from the conductor according to the inverse square rather than the inverse cube relation. This can be of practical significance for radiating stronger quasistatic magnetic fields especially at low frequencies.