Measured GICs and geomagnetic field in mid-Norway during the 3 November 2021 storm: the transformer neutral current (red) ideally should be zero but peaked near 60 A around 21:40 UT, coinciding with a nearby transformer trip. The ~1000 nT geomagnetic variation (green), a rare event, highlights the storm’s intensity and strong ionospheric currents. (Credit: SINTEF Energy Research and Dr. Kristian Solheim Thinn.)