ELF/SLF Electromagnetic Modeling And Analysis Of Earth-ionosphere Waveguide System Using FDTD Method

In this thesis, spherical-coordinate FDTD method is used to the modeling and analysis of ELF/SLF electromagnetic (EM) wave propagating in Earth-ionosphere waveguide system. The main contribution and contents are as follows:1. For spherical-coordinate FDTD method, we have designed 2D/3D geometric models for the waveguide system. Based on the geometric models, we deduce the iterative equations and formulas of stability conditions, which we have verified in different practical simulations.2. The simulation speed of traditional spherical-coordinate FDTD method is quite slow. So we use a grid-cell combined technique merging grid-cells near the Poles to deal with this problem. It can largely reduce the density of grid-cells approaching to the Poles and increase the time step of FDTD method. The technique can accelerate the simulation greatly.3. We have proposed two techniques, for the local high resolution modeling using Cartesian-coordinate and spherical-coordinate non-uniform FDTD method. According to the high accuracy requirement of the practical measurement, the density of grid-cells in selected regions can be adjusted easily, with the help of the two local high resolution techniques. It is flexible for users to gather the changing characters of EM field in these regions.4. We have merged the geographic information system (GIS) data, accepted conductivities of land-ocean and conductivities of ionosphere in the EM modeling of Earth-ionosphere waveguide system. The simulation results indicate that the EM propagation characters of the entire Earth-ionosphere waveguide system are more realistic.5. We have used high performance computing technique to accelerate the simulation of ELF/SLF EM wave propagation. The parallel computing environment based on MPI technique has been built. And the region segmenting technique of spherical-coordinate parallel FDTD method has been proposed.6. We have designed the ELF/SLF EM simulation software. The entire computing system has a friendly interactive interface, and it can output the results and figures automatically. Various parameters can be set conveniently according to the requirement of different users.