A New Numerical Model for Radio Atmospherics Propagation in the Earth-Ionosphere Waveguide Based on Layered gyrotropic anisotropic Green's Functions

A new frequency domain numerical model is proposed to simulate the lightning-generated electromagnetic wave (radio atmospherics) propagation in the ionospheric D region. The D region exponential electron density and collision frequency profiles are divided into several thin layers with the constant parameters in each layer. The frequency domain Dyadic Green's functions for layered gyrotropic anisotropic media is first derived by decomposing the spherical waves from an infinitesimal dipole into a series of planes waves in the spectral domain subject to multilayer reflection and transmission and later transformed back to the spatial domain. The line source model of the lightning return stroke channel in the computation is dealt with by the integration of current moment in the vertical direction. The results are verified by the finite element method performed in a commercial software. Then, the earth curvature effect is corrected by modifying the wave transmission and reflection index inside the gyrotropic anisotropic magnetized plasma for each plane wave component in the spectra domain. The final simulation results in the very low frequency (VLF, 3-30 kHz) band are verified by comparisons with Long Wave Propagation Capability (LWPC) computation and field measured radio atmospherics.