GIC–Related Observations During the May 2024 Geomagnetic Storm in the United States

The May 2024 geomagnetic storm was one of the most severe in the past twenty years. Understanding how large geomagnetic disturbances (GMDs) impact geomagnetically induced currents (GICs) within power grid networks is key to ensuring their resilience. We have assembled and synthesized a large and diverse set of GMD-related data, compared model predictions with measurements, and identified empirical relationships between measured GICs in the contiguous United States. Measurement data include GIC data from 47 sites and magnetometer data from 17 magnetometer sites. Model data include computed GIC by the Tennessee Valley Authority (TVA) power system operators at four sites, ΔB at all measurement sites from the Multiscale Atmosphere-Geospace Environment Model (MAGE), Space Weather Modeling Framework (SWMF), and Open Geospace General Circulation Model (OpenGGCM) global magnetosphere models, β scaling factors derived from magnetotelluric (MT) transfer functions at ~5,000 MT sites, and predicted GICs from the Tennessee Valley Authority electric power utility and a Reference Model. GIC measured and modeled by TVA had a correlation coefficient >0.8 and a prediction efficiency between 0.4 and 0.7. The horizontal magnetic field, ΔBH, predicted had a correlation that ranged from 0.49 to 0.51 for MAGE and 0.58 to 0.60 for SWMF. Two empirical relationships were considered: (1) how the correlation between measured GIC site pairs depended on differences in site separation distance, β scaling factor, and latitude, and (2) a regression model that predicts the standard deviation and max GIC at each site given inputs of site latitude and β. Presented at GEM/CEDAR in Des Moines, IA on 24 June, 2025