Study of interaction of ELF–ULF range (0.1–200 Hz) electromagnetic waves with the earth’s crust and the ionosphere in the field of industrial power transmission lines (FENICS experiment)

This article is devoted to describing the theory, technique, and first experimental results of a control source electromagnetic (CSEM) study of the Earth’s crust and ionosphere with the use of two mutually orthogonal industrial transmission lines 109 and 120 km in length in the frame of FENICS (Fennoscandian Electrical Conductivity from Natural and Induction Control Source Soundings) experiment. The main part of the measurements is executed on the territory of the Fennoscandian shield at distances from the first hundreds kilometers up to 856 km from the source with the purpose of the deep electromagnetic sounding of the Earth’s crust and upper mantle. According to the results of these studies clarifying the parameters of “normal” (standard) geoelectric section of the lithosphere to a depth of 60–70 km, the anisotropy parameters are evaluated and a geothermal and rheological interpretation in conjunction with the analysis of the seismic data is executed. Furthermore, to study the propagation of ELF–LLF waves (0.1–200 Hz) in an “Earth–Ionosphere” waveguide, the measurements are carried out apart from Fennoscandian shield at distances up to 5600 km from the source (in Ukraine, Spitsbergen, Poland, Kamchatka, and other areas). According to the results of these studies, the experimental estimates of the influence of the ionosphere and of the displacement currents on the propagation of ELF–ULF waves in the upper half-space at the different azimuths generation of the primary field are obtained.