An analysis of a staked dipole probe on a lossy Earth plane using the finite-difference time-domain method

Using the finite-difference time-domain (FDTD) method, an electrically short, staked, grounded horizontal probe is shown to have an open circuit voltage directly related to the horizontal electric field at the Earth's surface providing the surface coupling is subtracted from the output. This result is valid not only for an infinitely deep Earth plane but also for one which is horizontally layered. The effective length of a staked probe is found to be dependent on the conductivity of the upper layer of the Earth, its depth, the length of the stakes, and also the frequency of measurement. The effect is significant at very low frequency (VLF) for ice, permafrost and dry sand-covered regions.