Unique Signatures of Meridional Wind Variations on the Electron Density Distribution Over the Dip Equator

We investigate unusual daytime enhancement and undulations observed in Vertical Total Electron Content (VTEC) during the extreme G5 geomagnetic storm on 11 May 2024 over the dip equatorial station Trivandrum, India using a physics-based ionospheric model. To isolate the effects of storm-induced electric fields and neutral wind perturbations, we solve the ion continuity and momentum equations for seven ion species using a dipole geomagnetic field approximation. Our results show that fluctuating prompt penetration electric fields primarily drive the strong VTEC enhancement, while storm-time meridional wind reversals cause prominent undulations. The model reproduces the VTEC obtained by a co-located Digisonde. However, both the model and Digisonde underestimate GPS-derived VTEC in the post-noon sector, suggesting additional plasmaspheric contributions. This study demonstrates, for the first time, the coupled influence of electric fields and meridional winds in shaping ionospheric responses to severe storms over the Indian dip equatorial region.