Analysis of ELF Propagation Along the Earth Surface Using the FDTD Model Based on the Spherical Triangle Meshing

In this letter, we have introduced a meshing method that uses the spherical triangle grid units to model the Earth-ionosphere system and applied it to simulate the impulsive extremely low frequency (ELF) electromagnetic (EM) wave propagation employed by the finite-difference time domain (FDTD) method. We have also studied the properties of the spherical triangle meshing with different resolutions. Our work focused on the application and comparison of different FDTD methods modeling the ELF EM wave propagation along the Earth surface. Our comparison has been done with the longitude-latitude FDTD algorithm and the spherical hexagon and pentagon algorithm, and the comparison results showed our algorithm has many advantages. In the end, to prove the correctness of the algorithm, a real three-dimensional (3D) model extended from ideal two-dimensional (2D) model has been built, and the Schumann resonances have been calculated.