The calculation of theQfactors and frequencies of Earth-ionosphere cavity resonances for a two-layer ionosphere model

The equation describing the earth-ionosphere cavity resonance phenomenon is formulated in terms of reduced variables for the particular case of a two-layer model ionosphere. Solutions for the resonance frequencies and Q factors of the resonator are given for a practical range of parameter values of the lower ionosphere and, by comparing the theoretically predicted characteristics of the resonances with experimental observations, a specific model that explains world-wide propagation at extremely low frequencies is derived.