Dynamics of Equatorial Ionization Anomaly Merging during 19-20 January 2026 Geomagnetic Storm

The Equatorial Ionization Anomaly (EIA) is characterized as two bands of increased plasma density on both sides of the magnetic equator and a reduced plasma density region near the magnetic equator. During the geomagnetic storm (SYM-H reached -251 nT) on 19-20 January 2026, the GOLD observation revealed a single crest EIA near geomagnetic equator in South American region 3 hours after commencement. We will use a comprehensive set of measurements (e.g., incoherent scattering radar, ionosonde, TEC maps, in-situ satellite) to analyze the mechanism of the EIA merging. The coupled GITM-SAMI3 model will also be employed to investigate the role of neutral winds, vertical drift, prompt penetration electric field, diffusion, and chemical processes on formation and evolution of this single crest EIA. This study contributes to the understanding of dynamics of the single crest EIA phenomenon.