ИСТИНА

The geomagnetically induced current (GIC) intensity is determined by variations of geomagnetic field. Predominantly geomagnetic field disturbances are oriented in the N–S direction, and produced by the E–W ionospheric currents. Thus, such disturbances seemingly will not induce any significant GIC in a latitudinally oriented system. However, during magnetic storms GIC in power systems elongated in the N–S direction were quite significant. The relative contribution of geomagnetic disturbances into GIC enhancements are examined using data from GIC-recording system deployed by Polar Geophysical Institute. We apply to the IMAGE magnetometer data for the geomagnetic storm 17 March 2013 various techniques to characterize the geomagnetic field variability: vector mapping of time series, and a measure of time variations of vector angle cosines. This technique has shown that ionospheric currents fluctuate not just in E–W direction, but chaotically in both E–W and N–S directions. So these fluctuations cannot be described only by variations of the auroral electrojet intensity but the model of the GIC estimation must take into account small scale current systems in the ionosphere.