The transient electric fields about a loop on a halfspace

Abstract

The transient electric field excited by a step current in a loop of radius a on the surface of a ground of conductivity s and permeability m0 are concentrated in a toroidal zone. At early times the zone moves slightly inward from the loop and down but at later time the field maximum moves along a cone dipping at 30° away from the loop. At later times the maximum occurs beneath a point on the surface at radius R where R2 » 2.56 t/sm0. At this maximum the time rate of change of the radial magnetic induction is zero.