Electromagnetic resonances in the polar ionosphere

The utilization of resonant oscillations for ionospheric modification experiments and ionospheric diagnosis, based on plasma physics and non-linear electrodynamics, is discussed. The spectra of resonant oscillations of natural and artificial origin in the polar ionosphere and the excitation of these oscillations and their development are analysed. The thermal instabilities in weakly ionized heterogeneous magnetoactive ionospheric plasma, due to plasma heating, are illustrated. The circle of resonant situations in the polar area is expanded essentially due to intense current systems in this region.