Airglow Imaging Observations of Plasma Blobs: Merging and Bifurcation during Solar Minimum over Tropical Region

Plasma blobs are night-time ionospheric irregularities whose generation mechanism is still under investigation. A large number of observations highlighted several aspects of their morphology and dynamics. However, the plasma blobs have not been attributed convincingly to a known mechanism. We analyzed the OI 630.0 nm emission images during March and October of 2019 and 2020 (minimum solar activity) using the ground-based all-sky imager at ZF-2 (2.58 degrees S, 60.22 degrees W) in the Amazon region of Brazil. The novelties of the present study are the rarely reported observation of both plasma blob merging and bifurcation. We studied the evolutional dynamics of plasma blobs and observed that blobs are distinct phenomena with unique properties. We attribute the merging of plasma blobs to the "wind reversion effect" (WRE) mechanism caused by a change in the direction of the zonal thermospheric wind from east to west. In some cases, the slower-drifting plasma blobs may merge with the faster ones. Moreover, blobs were observed initially bifurcating at the topside and later divided into two. The activity of the polarized electric field inside the plasma bubble mapping along the magnetic field lines is possibly responsible for the blob's bifurcation. Subjecting the two features of ionospheric plasma blobs to simulation may reveal further the physics of blobs' merging and bifurcation.