Abstract
The finite-difference time-domain (FDTD) technique is used to model the 1D surface impedance of a lossy Earth plane having discontinuities in 2D and 3D. Using a horizontal magnetic field aperture source located five cells from an absorbing boundary and 35 cells above the lossy Earth plane, the surface impedance was accurately modeled at a distance of lambda0/5000 from the source using both grazing and normal incidence. The technique was validated by comparison with a number of 2D analytical models. The surface impedance profile in the vicinity of a vertical conductive water filled shaft that extends from the Earth's surface to a conductive basement is presented. Unlike modeling in the frequency domain, a single FDTD solution yields accurate multifrequency surface impedance data, provided a number of standard cell size constraints are met. For common Earth electrical constants, the FDTD approach is limited to frequencies above 500 Hz. (Author)