Краткое описание

Application of the records of global electromagnetic (Schumann) resonance in the Earth-ionosphere cavity attracts the permanent attention, as it allows the assessment of the global characteristics of the lower ionosphere and the dynamics of planetary thunderstorms by using a single or a small number of observatories. Solutions of the inverse problem are based on different approaches. We use a simple model of a point source in the present study. The 'knee" model describes the vertical profile of the atmosphere conductivity. The source-observer distance and its variations were evaluated from the first Schumann resonance peak frequency observed in the horizontal components of the magnetic field, since this frequency is proportional to the distance from the source. After estimating the source range, one can obtain the seasonal changes in their intensity by using the observed energy of oscillations. We process a fragment of the records at the Ukrainian Antarctic station "Akademik Vernadsky". We show that the seasonal latitudinal drift of global thunderstorms is estimated by 20°, and annual changes in the level of global lightning activity reach the factor of 1.5. The unequal duration of the "electromagnetic seasons" is confirmed: the summer (the farthest northern position of global thunderstorms) lasts for 120 days, while the winter is about 60 days. The duration of spring is shorter than that of the fall. The estimates obtained reasonably agree with the Schumann resonance data, with the climatology data, and optical observations of lightning flashes from the Earth's orbit. We also note that experimental results have an alternative interpretation, which implies the changes in the effective height of the lower ionosphere by a few kilometers. The most realistic mechanism of the observed changes must comprise both the latitudinal drift of global thunderstorms and the variations of the height of the ionosphere. Both the processes are caused by variations in the solar activity. It is also noted that the inter-annual trends in the resonance intensity might be linked to the trends in the surface temperature of the planet. Relevant estimate is given.