Local High-Resolution Technique in FDTD Modeling of ELF Propagation in the Earth–Ionosphere Cavity

In this letter, a local high-resolution technique (LHRT) of three-dimensional finite-difference time-domain (3D-FDTD) method is presented for the extremely low-frequency (ELF) electromagnetic (EM) wave propagation in the Earth-ionosphere cavity. This new model is useful for the analysis of the ELF EM wave propagating in a specific region, where the required space interval of the grid-cell is extremely fine. Once the length of the required space interval in the specific region and the cutoff frequency of the source are determined, the model of Earth-ionosphere cavity can be established automatically. It is verified that the simulation results of the new technique are as accurate as those of the traditional methods.