3D-FEM simulation model of the Earth-ionosphere cavity

Radio waves of extremely low frequencies (5-40Hz) propagate in a special way. Since their wavelengths correspond to the Earth's radius, global resonances are found inside the cavity bounded by the Earth's surface and the lower ionosphere. These so-called Schumann resonances form a system of standing waves around the planet. They can be a powerful tool for investigating the electrical processes occurring in the lower ionosphere. This paper describes finite element method (FEM) simulations in the frequency domain of Schumann eigenmodes in 3D inhomogeneous Earth-ionosphere cavity. Such an approach provides result independence from source configuration and allows to separate ionosphere configuration influence on Schumann resonances. Also the approach visually reproduces line splitting in the global resonances. The ionosphere was modeled by a simple conventional vertical conductivity profile and by means of a complex 22-species plasmachemical model. Obtained simulation results are compared with the experiment and discussed.