Abstract The May and October 2024 geomagnetic storms represent two of the most intense space weather events of Solar Cycle 25. While differing in global intensity, both storms produced extreme ionospheric disturbances, including equatorward auroral expansion to mid‐latitudes and rapid geomagnetic variations (). Using 1‐min data from 73 INTERMAGNET observatories, we analyze the horizontal and vertical field components and reconstruct equivalent ionospheric currents to compare their electrodynamic responses. Both storms exhibited significant auroral current expansion, but with distinct temporal evolution: the May storm maintained elevated and perturbations throughout its prolonged recovery phase, while the October storm showed faster contraction of disturbances. This resulted in a substantially extended duration of elevated geoelectric hazard potential for the May event. Our results provide further evidence that for storms of comparable severity, the global SYM‐H index alone cannot fully capture regional ground‐level impacts. Phase‐resolved monitoring of ionospheric currents is therefore essential for accurate space weather risk assessment.
Michelis et al. (Sun,) studied this question.
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