Geomagnetically induced currents during intense storms driven by coronal mass ejections and corotating interacting regions

Geomagnetically induced currents (GIC) flowing in ground‐based conductor systems during large geomagnetic storms are one of the most significant space weather phenomena that affect our ground‐based technological systems. Here we show that GIC activity in subauroral latitudes depends on the storm phase and on the interplanetary drivers, such as coronal mass ejections (CMEs) and corotating interacting regions (CIRs). For example, it is shown that GIC amplitudes are relatively small during CIR storms in comparison to CME storms. However, Pc3‐5 pulsation activity during CIR storms drives long‐lasting GIC in the local prenoon sector. Despite of the differences between CME and CIR storms, the relationship between GIC and the time derivative of the horizontal ground magnetic field is always the same. A novel power law equation is derived to accurately characterize the relation.