Dynamics of EPBs and MSTIDs interaction during the post-midnight sector over the Indian low-latitude region

Abstract

We present evidence of the merging of Equatorial Plasma Bubbles (EPBs) with Medium-Scale Travelling Ionospheric Disturbances (MSTIDs) during the post-midnight sector over the Indian region, observed on the night of 28th January 2011, a typical spread F event. The wavefront of the MSTIDs was aligned from northwest to southeast, propagating southwestward. In this study, we analyze airglow data from OI 630.0 nm emission recorded by an all-sky imager (ASI) located at Kolhapur (16.8°N, 74.2°E). The onset of EPBs was observed around 13:30 UT. Notably, eastward-moving EPBs began to merge with the dark wavefronts of MSTIDs around 19:50 UT, with the process completing by 21:45 UT. During this merging process, the drift velocity of EPBs decreased from 100 m/s to 50 m/s which later merged with the dark fronts of MSTIDs, as noted in OI 630.0 nm images. This interaction resulted in structural changes to the eastward drifting EPBs. The electrodynamics associated with this novel event is elaborated in this paper.