The structure of extremely low frequency field reflected by the ionosphere

The amplitudes of variations in the magnetic and electric fields at extremely low frequencies were studied on the Kola Peninsula during a five-day-long experiment under different geophysical conditions. These studies demonstrated that the influence of the ionosphere is distinguishable at frequencies of <10 Hz and the structure of field variations reflected by the ionosphere is similar to that of the transverse wave. It is established that the ratio between semimajor axes of polarization ellipses of the electric and magnetic fields is independent of the state of the ionosphere and is likely determined by the deep structure of the crust beneath the site of the experiment.