Abstract This study investigates the global ionospheric and thermospheric responses to the 31 December 2024–3 January 2025 geomagnetic storm using Global Navigation Satellite System (GNSS) receivers, Digisondes, and ground‐based magnetometers across the American, European‐African, and Asian‐Australian sectors. GNSS‐derived vertical total electron content (GNSS VTEC) measurements revealed the highest enhancements (exceeding 170%) during the main phase in the American sector. The correlation coefficients () between critical frequency at F2‐layer (foF2) and GNSS VTEC consistently exceeded 0.83 at most stations, indicating that their fundamental relationship remained robust despite significant geomagnetic disturbances. Magnetometer stations tracked strongest disturbances in ionospheric current systems (Sq), reaching up to ∼100 nT and prompt penetration electric field () amplitudes reaching up to ∼352 nT in the American sector. The strongest disturbances in the dynamo effects () is also observed in the European‐African sector. The storm's evolution showed prompt penetration electric field (PPEF) effects dominating initial phases, particularly in equatorial regions, while persistent disturbance dynamo electric field (DDEF) influences controlled recovery‐phase dynamics. These storm‐time electric fields actively suppressed equatorial ionospheric irregularities by inhibiting the crucial pre‐reversal enhancement (PRE), shown on the decreased of Rate of TEC index (ROTI) below the threshold values at American low latitude station during the main phase. Hemispherically asymmetric thermospheric composition changes (O/) further modulated the responses. Consequently, sector‐specific patterns emerged: the American sector exhibited both large plasma enhancements and mid‐latitude depletion, the Asian‐Australian sector showed the most pronounced positive storms, and European‐African stations displayed strong nighttime ionization increases and distinct dynamo signatures.
Tariku et al. (Mon,) studied this question.