Variability of averaged annual impedances of the Earth and their spatial gradients in Europe
© Semenov V.Yu., Petrishchev M.S.
Secular variations of the Earth's impedance for periods from several hours till month have been detected by
two kinds of induction sounding methods. The analysis is based on the dynamic spectra of the 30-70 year data series
observed at eight geomagnetic observatories in Central Europe. The apparent resistivities obtained by the generalized magnetovariation
sounding method have been averaged for annual intensity taking into account coherence values. These annual variations are correlated with
the intensity of the Sun activity. Besides, the Earth's apparent resistivities have some quasi-linear trends. Five groups of observatories have
been analyzed to estimate the lateral gradients of response functions. The most brightly changes of the induction vectors have been established
for imaginary arrow Cv near the years 1969-1972. The obtained results have been used to estimate possible variability of the Earth's
conductance. The peculiarities of this phenomenon are discussed.