Excitation of a conducting half-space by a toroidal coil

The possibility exists that a non-contacting “vertical-electrical dipole”source could be devised, to excite both horizontal and vertical currents in the subsurface. The scheme is quite simple, but it seems to have been overlooked or, at least, not disclosed, hitherto. The idea is to employ a toroidal coil carrying an alternating current, which is located in or just above the air/earth interface. As shown, when the diameter of the toroid is small compared to the distance to the observer, the effective source is effectively a vertical-electric dipole. This may be obvious to some, but the situation has some interesting complications, because of the presence of the interface. The pertinent analysis is outlined