The Simulation And Modeling Of Electromagnetic Wave Propagation In The Earth-ionosphere Waveguide

It has been confirmed by numerous seismic cases that ionospheric anomalieswould occur before an earthquake，and the anomaly detection is expected to becomean effective short-term earthquake prediction methods．The three-dimensional modelof the Earth’s ionosphere waveguide system is built based on the FDTD (FiniteDifference Time Domain method) method to analyze the characteristics ofelectromagnetic wave．The earthquake-ionosphere coupling mechanism is studiedby introducing the actual source of thunderstorms and the earthquake observed intothe FDTD model.Firstly， the three-dimensional spherical coordinates electromagnetic wavepropagation iterative equations and the discontinuous iterative equation at north andsouth poles are derived by the FDTD method．Secondly，we simulate the Schumannresonance in the model with three sources of thunderstorms on Earth．The resultsshow that the frequency of SR is10.6Hz，18.4Hz，26Hz，33.5Hz and41.1Hz in thelossless cavity． However， the cavity is lossy and the conductivity model isintroduced in the model to simulate the SR which frequency is7.8Hz，14Hz，20.2Hz，26.5Hz and32.5Hz just be consistent with the observed results．In this paper，the SR characteristics and the interference characteristics areanalyzed based on the above model and the SR skin depth is calculated with thequality factor which is used to modify the radius of the planet in theory．Thediffraction in the cavity is discussed based on the interference and the results showthat diffraction does exist which is the directed waves and the scattered waves tointerference at the point of receiving station．In this paper we will discuss the90degree phase transition at the spherically symmetric points when theelectromagnetic arrive．At last we know that diffraction， phase transition and thespherical distance between the direct wave and the scattered wave determine theinterference，which directly affect the resonant amplitude of the cavity． Thesimulations of SR anomaty are conducted by introducing the irregularities in theepicenter． The results show that SR anomaties which characterized by third andfourth order resonance frequency shifted and amplitude enhanced will occur beforeearthquake．However，the amplitude reduced is also observed．...