ELECTROMAGNETIC UHF RESPONSE OF THE IONOSPHERE TO THUNDERSTORMS AND TYPHOONS

Abstract

The appearance of a resonant spectral structure (RSS) – multiband spectra of electromagnetic noise in the range of the first Hz, observed on the Earth’s surface at night, is usually associated with the excitation of the ionospheric Alfvén resonator (IAR) in the upper ionosphere. The proposed review discusses various ideas about the specific mechanisms of excitation of IAR by lightning discharges: (1) the generation of a set of eigenmodes of the IAR, (2) the formation of an echo pulse by the primary pulse reflected from the upper boundary of the IAR, (3) the presence of isolated pulses with a certain duration. The arguments for and against each proposed mechanism are considered. Qualitative representations of how the pulse structure of the response to a thunderstorm discharge should be visible in the data of low-orbit satellites are formulated. The response of an ionospheric magnetosonic waveguide to volcanic thunderstorm activity is considered. The detection of «magnetic ripples» over typhoons in the upper ionosphere – fluctuations of small amplitude with a period of 5–10 seconds caused by small-scale longitudinal currents, which are apparently generated by acoustic waves in the lower ionosphere, is discussed. The unsolved problems of electromagnetic coupling between the atmosphere and the ionosphere in the IAR range have been formulated.