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3-D FDTD modeling of ULF/ELF propagation within the global Earth-ionosphere cavity using an optimized geodesic grid

We discuss an emerging application of finite-difference time-domain (FDTD) computational electrodynamics: modeling transient ultra-low frequency (ULF) and extremely low frequency (ELF) propagation within the global Earth-ionosphere cavity. This permits for the first time a direct, three-dimensional, time-domain calculation of round-the-world ULV/ELF propagation accounting for arbitrary horizontal as well as vertical geometrical and electrical inhomogeneities and anisotropies of the excitation, ionosphere, lithosphere, and oceans.