Abstract
<jats:p>Geomagnetically induced currents (GICs) pose a significant threat to technological infrastructure during geomagnetic storms. We investigate two successive GIC enhancements during the 11–12 November 2025 geomagnetic storm using direct GIC measurements, ground, geosynchronous magnetic field observations, and upstream solar wind data. The first GIC enhancement was triggered by an interplanetary dynamic pressure pulse within the ICME sheath, which produced a nearly simultaneous intensification of ground magnetic field variations over broad latitude range extending from higher-mid to low latitudes. In contrast, the second enhancement occurred in the absence of significant upstream solar wind variability and coincided with the development of a substorm current wedge, resulting in magnetic fluctuations that remained largely confined to higher-mid latitudes. Despite producing comparable GIC amplitudes, the two events exhibited different spatial signatures, revealing that similar GIC levels can arise from different physical mechanisms. This distinction is essential for accurately assessing geomagnetic hazards during space weather events. Plain Language Summary Geomagnetic storms can induce electric currents in power grids, known as GICs, which may damage transformers and disrupt power systems. During the 11–12 November 2025 “Ugly Duckling” geomagnetic storm, we observed two large GIC events that occurred less than two hours apart. Although the currents measured in power networks were similar, they were produced by different physical processes. The first event resulted from a sudden increase in solar wind pressure that disturbed the Earth’s magnetic field over a wide range of latitudes. The second was caused by a substorm within the Earth’s magnetosphere and affected mainly auroral and higher-mid latitude regions. By combining satellite observations, ground magnetometers, and power network measurements, we show that similar GICs can have very different geographical impacts depending on the physical process that generates them. These results improve our understanding of how space weather affects technological systems and can help improve forecasts of regions most vulnerable to GIC hazards.</jats:p>