Geophysical processes and biosphere: article

Аnnotation: The study results of the temporal and spatial variability of the geomagnetic and telluric fields driven by anomalous space weather in the central and eastern parts of the Fennoscandian shield are presented. Data from the Scandinavian network of geomagnetic observations IMAGE are analyzed together with the measurements of the geomagnetically induced currents (GIC) in nearby electric power lines. For the synthesis of telluric fields from the observed geomagnetic variations, we used magnetotelluric impedance estimates obtained in the frames of BEAR electromagnetic sounding experiment in Fennoscandia. A comparison of geomagnetic, telluric, and GIC variations’s spectral composition in various sites and for various space weather events has identified, that time derivative of geomagnetic field (dB/dt), usually used as a measure of GIC-disturbances, does not fully control the latter. The analyzed telluric fields and observed GIC demonstrate a significant dependence on the induction response of the electrically conducting Earth interiors, the character of which varies greatly in the various geological domains of the Fennoscandian shield. The regional spatial variations of the telluric field and the GIC, due to the geoelectric structure heterogeneity, are superimposed on the regular decreasing trend in their amplitudes with increasing distance from auroral latitudes. Based on magnetotelluric sounding data, estimates of the extreme values of telluric fields during geomagnetic storms and substorms are obtained for different sites - the key information for predicting GIC in regional power lines.