COMPARISON OF LONG-TERM ANTARCTIC OBSERVATIONS OF THE SCHUMANN RESONANCE WITH COMPUTATIONS ON THE BASIS OF A TWO-COMPONENT OTD-DMM MODEL

摘要

Continuous Schumann resonance (SR) observations open the wide possibilities for permanent monitoring of the lower ionosphere and global thunderstorm activity. The existing methods for monitoring the thunderstorms with the help of SR were developed in detail only for the point source models. However, such customary models describe the sources of radiation in a too simplistic manner. In this connection, the development of semi-empirical source models becomes important, in which the distribution of lightning intensity in global thunderstorms is picked from the data of satellite observations. The paper compares the long-term experimental SR data accumulated at the "Akademik Vernadsky" Ukrainian Antarctic station with the computation results obtained in the two-component OTD-DMM model. It is shown that in spite the detailed OTD distributions of the global lightning activity deduced from the optical observations from space, the model is only partially consistent with the experiment. On the daily time scale, the two-component OTD-DMM model correctly reflects position of the main maximum of the global thunderstorms and their intensity. However, position of individual sources is inexact, and it does not allow for adequate diurnal variations in the SR peak frequencies. The model rather closely describes seasonal and inter-annual variations of peak frequency of the horizontal magnetic components H_y. It is shown that the inter-annual variations of peak frequencies might be attributed to the change in the ionosphere height combined with the north-south drift of sources from year to year, while the long-term drift of the peak frequency is associated most probably with modification of the lower ionosphere during the solar cycle.