Optical Observation of Ionospheric Plasma Blobs Merging, Bifurcation and Disconnection at the Equatorial Region Over Brazil: Possible Influence of Thermopheric Winds.

Plasma blobs, characterized as nocturnal ionospheric irregularities, remain a phenomenon with an unknown generation mechanism. Despite numerous observations shedding light on their morphology and dynamics, a definitive link to a recognized mechanism is lacking. This study scrutinizes OI 630.0 nm emission images from March and October 2019 and 2020, periods of minimum solar activity, utilizing a ground-based all-sky imager located at ZF-2 (2.58° S, 60.22° W) in the Amazon region of Brazil. Unique to this investigation is the rarely documented occurrence of plasma blob merging, bifurcation, and disconnection. Examining the evolutionary dynamics of plasma blobs, our observations reveal distinct phenomena exhibiting unique properties. We attribute the merging of plasma blobs to the "wind reversion effect" (WRE), triggered by a shift in the zonal thermospheric wind direction from east to west. In some cases, slower-drifting plasma blobs may merge with their faster counterparts. Additionally, we observed cases where blobs initially bifurcated at the topside, later dividing into two separate blobs. The polarized electric field activity within the plasma bubble, aligned along magnetic field lines, is probably responsible for blob bifurcation. However, to understand the underlying physics of plasma blobs' merging, bifurcation, and disconnection, simulation-based investigations may provide further insights into these interesting features of ionospheric irregularities.