Geomagnetically induced currents (GICs) represent a significant challenge for society on a stable electricity supply. Space weather activates global electromagnetic and plasma processes in the near-Earth environment, however, the highest risk of GICs is related not directly to those processes with enormous energy yield, but too much weaker, but fast, processes. Here we consider several typical examples of such fast processes and their impact on power transmission lines in the Kola Peninsula and in Karelia: interplanetary shocks; traveling convection vortices; impulses embedded in substorms; and irregular Pi3 pulsations. Geomagnetic field variability is examined using data from the IMAGE (International Monitor for Auroral Geomagnetic Effects) magnetometer array. We have confirmed that during the considered impulsive events the ionospheric currents fluctuate in both the East-West and North-South directions, and they do induce GIC in latitudinally extended electric power line. It is important to reveal the fine structure of fast geomagnetic variations during storms and substorms not only for a practical point of view but also for a fundamental scientific view.

The strongest event of geomagnetically induced currents (GIC) detected by the North‐West Russian GIC network occurred during the main phase of the magnetic storm on 28 and 29 June 2013. Extremely high value, 120 A, was recorded in the 330 kV transformers on Kola Peninsula in the 04–07 magnetic local time (MLT) sector. The Defense Meteorological Satellite Program (DMSP) spacecraft took a sequence of ultraviolet (UV) auroral images in the southern hemisphere and observed multiple omega bands. The ionospheric equivalent electric currents based on the International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network reveal a sequence of current vortex pairs moving eastward with the speed of 0.5–2.5 km/s that fits to the electrodynamics scheme of omega bands. Although the temporal variations of the associated current system are slow, the omega bands can be responsible for strong magnetic variations and GIC due to fast propagations of currents in the azimuthal direction.

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<p>The strongest event of geomagnetically induced currents (GIC) detected by the North-West Russian GIC network occurred during the main phase of the magnetic storm on June 28-29, 2013. Extremely high values, 120 A, were recorded in the 330 kV transformers on Kola Peninsula in the 04--07 magnetic local time (MLT) sector. The Defense Meteorological Satellite Program (DMSP) spacecraft took a sequence of ultraviolet (UV) auroral images in the southern hemisphere and observed multiple omega bands. The ionospheric equivalent electric currents based on the International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer network reveal a sequence of current vortex pairs moving eastward with the speed of 0.5-2.5 km/s, that fits to the electrodynamics scheme of omega bands. Although the temporal variations of the associated current system are slow, the omega bands can be responsible for strong magnetic variations and GIC due to fast propagations of currents in the azimuthal direction.  The first steps towards the statistica study of the highest GIC recorded at Vykhodnoy transformer show that about 50% of events have properties similar to the comprehensively studied 29 June 2013 case.</p>

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