ИСТИНА

In this study we examine the features of the influence of geomagnetic substorms on the generation of geomagnetically induced currents (GICs) recorded in electric power lines of Kola Peninsula and Karelia (Russia). The continuous registrations of GICs in this system are performed since 2010. The registration system includes 5 stations elongated in the north-south direction. The GIC observations are augmented by the magnetometer data from near-by IMAGE stations and information on impedance tensors of the Eastern Fennoscandian Shield from the electromagnetic deep sounding array BEAR. We compare the spectral content of geomagnetic, telluric, and GIC variations. The frequency-dependent geoelectric response of the crust results in the suppression of high-frequency component in the GIC spectrum as compared with dB/dt variations. It was commonly believed that the auroral electrojet is a main driver of GIC at high latitudes. On the base of this notion it is considered that GIC is dangerous only for the east-west elongated technological systems. However, more detailed analysis of the GIC, B, and dB/dt variations shows that a dominant contribution to bursts of GIC is provided by small-scale vortex-type ionospheric current structures. So, the GIC are dangerous for the technological systems elongated in north-south direction as well. Contrary to common point of view, it is found for some substorms that noticeable GICs are better correlated with geomagnetic field variations B than with variations of dB/dt. Large GIC values may be caused not only by the temporal variations of the geomagnetic field but also by the spatial variation of the vortex-like ionosphere current systems driven by magnetospheric field-aligned currents. The analysis of the spatial distribution of the geomagnetic field variations and dB/dt shows that its maximums do not coincide in latitude-MLT coordinated. The maximum amplitude of the geomagnetic field disturbances does not match the maximum of GIC.