TIME-DOMAIN 3-DIMENSIONAL DIFFRACTION BY THE ISOREFRACTIVE WEDGE

The extension of the Biot-Tolstoy exact time domain solution to the el ectromagnetic isovelocity or isorefractive wedge is described. The TM field generated by a Hertzian electric dipole can he represented by a vector potential parallel to the apex of the wedge and a scalar potent ial necessitated by the three dimensionality of the magnetic field. Th e derivation of the former is exactly that of the pressure in the corr esponding acoustic situation [1], and a more efficient version of the lengthy details is presented herein. A Lorentz gauge determines the sc alar potential from the vector potential, and the diffracted field con tains impulsive and ''switch-on'' terms that cannot be evaluated in cl osed form. The ratio of arrival times, at a given point, of the geomet rical optics and diffracted fields provides a convenient parameter, in addition to the usual metric-related variable, for graphically displa ying this scalar potential.