Transient current density waveforms on a perfectly conducting sphere

The time-dependent surface current density waveforms at various points on the surface of a perfectly conducting sphere illuminated by a plane electromagnetic wave are presented. The incident plane wave has an impulsive or shock-type time dependence. Current density waveforms in the E-plane (strong creeping wave) and H-plane on both the lit and shadowed sides of the sphere are shown. On the illuminated side of the sphere, removal of the Kirchhoff or physical optics approximation for the surface current density permits a detailed examination of the deficiencies of this approximation for short times (high frequencies). From these results the form of a first order correction to the Kirchhoff current is suggested. On the shadowed side of the sphere, the changing character of the current waveform is noted.