Solar cycle 25 geomagnetic storms' impact on Germany's power grid

Kurzfassung

The current transition of solar cycle (SC) 25 into maximum phase provides an apt opportunity to investigate the impact of space weather on critical infrastructure, particularly in subauroral regions. This contribution focuses on the modeling of Geomagnetically Induced Currents (GICs) in the German high-voltage transmission grid (380kV) for recent geomagnetic storms of SC 25. The modeling rests on geomagnetic disturbance maps deduced from INTERMAGNET observatory data which is combined with 3-D surface impedance tensors extracted from a dedicated conductivity model to give the induced geoelectric field in the period range ~10-10000s. The latter then interfaces with our transmission grid model in the form of additional voltage sources placed in power lines connecting grounded transformers to drive GICs. Among the modeled events are the 23-24 April 2023 geomagnetic storm, for which we compare our results to direct GIC measurements from a substation in northwestern Germany, and the severe 10-12 May 2024 storm. We investigate the obtained GIC amplitudes across the country, incentivizing further direct GIC monitoring in areas of increased GIC risk.