The study of extremely low frequency electromagnetic waves in the ionospheric cavities of planets and satellites surrounded by atmospheres follows an approach similar to that developed for Earth. It contributes to the characterization of the atmospheric electric circuit and associated energy sources, and to the identification of the cavity boundaries. A finite element model is developed and applied to those bodies, with the aim of studying, in particular, the Schumann resonance. The validity of a model of Titan's cavity is checked against the measurements performed by the PWA analyzer, onboard the Huygens Probe. The discovery of an ionized layer at low altitude and the evaluation of the surface dielectric properties, after touchdown, are also addressed. The acquired experience is applied to the design of novel instruments, ARES and SP2, to study the atmosphere and the ground of the planet Mars, in the forthcoming ExoMars mission, and of other celestial bodies in future space missions.
