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 20 years. Understanding how large geomagnetic disturbances (GMDs) impact geomagnetically induced currents (GICs) within electrical power grid networks is key to ensuring their resilience. We have assembled and synthesized a large and unique set of GMD-related data, compared model predictions with measurements, and identified empirical relationships for GICs in the contiguous United States for this storm. Measurement data include GIC data from 47 sites and magnetometer data from 17 sites. Model data include GIC computed by the Tennessee Valley Authority (TVA) power system operators at 4 sites, GIC computed using a reference model at 47 sites, and the difference in the surface magnetic field from a baseline (Formula presented.) computed at 12 magnetometer sites from three global magnetospheric models—the Multiscale Atmosphere-Geospace Environment Model (MAGE), Space Weather Modeling Framework (SWMF), and Open Geospace General Circulation Model (OpenGGCM). GIC measured and computed by TVA had a correlation coefficient (Formula presented.) and a prediction efficiency between 0.4 and 0.7. The horizontal magnetic field perturbation from a baseline, (Formula presented.), computed by MAGE, SWMF, and OpenGGCM had a correlation r from 0.21 to 0.65. Two empirical relationships were considered: (a) how the correlation between measured GIC site pairs depended on differences in site separation distance, (Formula presented.) scaling factor (related to ground conductivity), and geomagnetic latitude; and (b) a regression model for the maximum (Formula presented.) magnitude at each site given the product of (Formula presented.) (related to magnetic latitude) and (Formula presented.).