Latitudinal dependence of geomagnetically induced currents during geomagnetic storms

Abstract

Major geomagnetic storms drive rapid intensification and variability of magnetospheric and iono- spheric current systems that give rise to large ground-induced currents (GIC). Space weather as- sociated GIC pose a serious threat to the reliability of power-transmission systems and other elec- trically conducting infrastructure such as oil and gas pipelines. The most severe effects are ob- served at high latitudes due to ionospheric currents associated with the aurora. However, as power transmission grid and pipeline infrastructure continues to grow at middle and low-latitudes, GIC hazards are no longer just concerns of high-latitude regions. We investigate how GIC amplitude varies in latitude during six major geomagnetic storms that occurred between 1989 and 2004. Due to limited direct GIC measurements, a proxy of the geoelectric field is used, i.e. the GIC index. This is calculated for the selected geomagnetic storms using 25 magnetic observatories relatively uniformly distributed in geomagnetic latitude, 14 magnetic observatories with longitudes varying within a range of 45 degrees as well as for the 7 November 2004 storm using 104 observatories. In addition, we suggest a possible way to follow the latitudinal displacement of the auroral oval dur- ing geomagnetic storms through the maximum value of GIC index, estimated over 2-hour inter- vals on a wide number of magnetic observatories.