Analysis of the Mother’s Day Storm Effects on Equatorial Power Grids Near the Equatorial Electrojet Region

Abstract. Power transmission lines are susceptible to geomagnetic risks known as geomagnetically induced currents (GICs). These currents arise from rapid variations in the geomagnetic field at Earth’s surface, which induce geoelectric fields in the ground and drive GICs into the grounded neutral points of conductive infrastructure such as power transmission networks. In this study, we analyzed the behavior of two equatorial transmission lines —where the Equatorial Electrojet (EEJ) exerts a strong influence on electromagnetic variations —using measured current and voltage records from these lines, along with magnetic data from the geomagnetic superstorm of 10–11 May 2024, one of the most intense events of the past two decades. Magnetic observatories at Tatuoca (TTB), Kourou (KOU), and São Luís (SLZ) were selected to characterize regional field variations via the time derivative of the horizontal geomagnetic component (dH/dt). We then computed Pearson correlation coefficients between two distinct storm phases and the electrical parameters of the lines. The dH/dt proxy for GIC activity exceeded ±36 nT/min at all sites and peaked above 65 nT/min at TTB and SLZ. Strong to very strong correlations emerged during the storm’s initial and main phases (first period analized), while correlations weakened to moderate levels during recovery. These findings provide a solid foundation for future studies and inform the development of preventive measures by power-grid operators under intense geomagnetic activity.