Physics of auroral phenomena : proceedings of the 40th annual seminar, Apatity, 13-17 March, 2017 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2017. - 143 с. : ил., табл.

The magiieticfield variability and geomagnetically induced currents in electric power lines RB = 1 Z cos, a Here the vector orientation cosines are: cosxa = ДХУ|ДВ|; cosy a = ДУ/(ДВ|апс1 modulus of geomagnetic disturbance: AB = у/AX2 + A Y 2. The parameter RB does not depend on magnitude of geomagnetic disturbance. If RB-> 1 a vector field experiences chaotic variations in all directions, while RB ->0 denotes that a field varies in magnitude only, but not in direction. 4. Event on March 17, 2013. The magnetic storm on March 17, 2013 started with arrival of interplanetary shock on 06 UT. During the shock solar wind velocity jumped from ~400 km/s to -650-700 km/s. IMF Bz turned southward providing a permanent energy supply into the magnetosphere. SYM-H index gradually dropped till -100 nT and remained on this level. The AE index shows several activations at auroral latitudes: just after SC till ~1100 nT at 08 UT, after -12 UT with maximum -1000 nT, and most intense increase up to -2500 nT at -17 UT. Geomagnetic field variations at IMAGE stations during this storm (Fig. 1) in X component are more intense than in Y component, that is |X |»|Y |. This fact seemingly supports the notion about a dominant role of the westward electrojet fluctuations for GIC generation. I NOR , X Q9Z!- . ; : : % 4 I ! : : i 1 I ivox . r : .lO.lOt- : : ! • IVA. X Figure 1. Geomagnetic field variations [in 104nT] at latitudinal array of stations NOR, IVA, PEL, OUJ, HAN from IMAGE array during magnetic storm on March 17, 2013, 05-24 UT: left-hand panel shows X component, right- hand panel shows Y component. The vertical scale is the same for all stations and components. The GIC recording stations recorded several significant bursts of GIC intensity (Fig. 2) reaching -70 A at VKH. A growth of AE index during each activation generally corresponds to bursts of |dB/dt| (up to 250 nT/min) and GIC intensity (at -06-08 UT, -16 UT, and -18 UT) (Fig. 4). However, there are non one-to-one correspondence between the substorm intensity characterized by AE index and GIC magnitude. For example, AE index during the activation on -13 UT is comparable to the index during the activation on -08 UT, but the GIC intensity during the latter activation is much weaker. At the same time, intense GIC bursts occurred at -19-20 UT and at -2130-2330 UT, when AE index was somewhat decreased. We have applied the vector diagram method to the available mid-latitude IMAGE magnetometer data (Fig. 3.). The diagram shows that during the storm not only the magnitude of magnetic disturbance varied, but its orientation as well. These variations are caused by rapid changes of regional ionospheric current direction. The observed pivot of equivalent ionospheric currents on—08 UT, -16 UT, and~19UT correspond to localized vortex-like current structures moving across the magnetometer array. 35