An Analytical Model of ELF Radiowave Propagation in Ground-Ionosphere Waveguides With a Multilayered Ground

A planetary crust with a low electric conductivity has a strong influence on extremely low frequency (ELF) radiowave propagation in the ground-ionosphere waveguide due to the penetration of the ground by the wave's electromagnetic field. The amount of influence it has depends on the actual structure of the ground. Accurate models of radiowave propagation in the ELF range are essential in the study of atmospheric discharges and remote sensing applications. Analytical models are still of primary interest when trying to find inverse solutions and when dealing with large objects such as spherical waveguides that consists of a planetary ground and ionosphere. In this paper, we analyze the influence of a multilayered finite conductivity ground on the propagation of ELF electromagnetic waves in the ground-ionosphere waveguide. We have developed equations that enable us to include different ground models in propagation equations using the concept of complex altitudes, and applied them to the study of ELF electromagnetic field pulses on Mars. This study shows that the structure of the ground and its electrical conductivity has a strong influence on the observed waveforms. Therefore, ELF pulses can serve as a tool for probing planetary grounds. The presented model can also be used to study Schumann resonances.