Unusual Propagation of MSTIDs Observed on 31 January 2017: Evidence of Complex Electrodynamical Modulation Over Low‐Latitude Ionosphere

Abstract This study investigates the interaction between Equatorial Plasma Bubbles (EPBs) and Medium Scale Traveling Ionospheric Disturbances (MSTIDs) observed on 31 January 2017 over low‐latitude India using a multi‐instrumental approach. OI Nightglow images from Panhala (16.48°N, 74.6°E, and 11.1°N MLAT) and Gadanki (13.5°N, 79.2°E; ∼6.6°MLAT), ionosonde measurements from Tirunelveli, GPS TEC measurements from Hyderabad & Bangalore and geomagnetic data from India were analyzed to examine how MSTIDs influence EPB morphology, drift, and evolution. EPBs, typically drifting eastward after post‐sunset pre‐reversal enhancement of the zonal electric field via Rayleigh‐Taylor instability, exhibited modulation by a south to north‐westward propagating MSTID observed simultaneously at both ASI locations. This MSTIDs, induced elongation, intensification, and in some cases, dissipation of EPBs depending on their phase alignment. Keograms from both sites revealed consistent plasma perturbations, with Gadanki data confirming the presence and propagation of the same MSTID front, even near the magnetic equator. The h’F obtained from Canadian Advanced Digital Ionosonde observations from Tirunelveli (8.73°N, 77.7°E, and 1.6°N MLAT) supported strong PRE‐driven vertical uplift coinciding with EPB onset. Dual‐frequency GPS‐TEC analysis over Hyderabad (HYDE) and Bangalore (IISC) revealed quasi‐periodic MSTIDs signatures with northwestward propagation indicating large‐scale ionospheric disturbances likely driven by gravity waves. These results confirm MSTID‐induced modulation of EPBs, validating gravity wave seeding as one of the key mechanism influencing equatorial ionospheric irregularities. The findings underscore the value of coordinated optical and radio measurements for understanding the horizontal and vertical coupling processes occurring at ionospheric altitudes.