Simultaneous occurrence of three non-interacting characteristically different ionospheric plasma structures over the geomagnetic low-mid latitude transition region

An unusual event of three characteristically different plasma structures on a geomagnetically quiet night (Ap = 4) of 08 July 2018 has been investigated in this paper using an all-sky imager installed at Hanle, Leh Ladakh (32.7°N, 78.9°E; Mlat. ̃24.1°N), India. These structures include a freshly generated electrified MSTID (EMSTID), ambiguous plasma depletions, and a northward propagating non-electrified MSTID. One of the most fascinating aspects of this event was the lack of mutual interaction between the three structures, even though they existed simultaneously and propagated in different directions. They individually underwent evolution, distortion, and dissipation separately. One of the structures was an EMSTID, which got generated within the imager’s field-of-view (FOV) and evolved with time. As time progressed, different strip-like structures travelled southwestward, merged with each other to form the EMSTID and disappeared later. The second structure was plasma depletions which appeared in the southeastern part of the FOV. They eventually merged into a single band. The merged band evolved with time, extended further northward, and dissipated later. Along with these, a very rare non-electrified MSTID structure with east-west aligned fronts was observed which propagated northward. Its fronts underwent distortion, became curved and dissipated. In this study, we have explored the role of electrodynamics and neutral dynamics behind the observed unique features of the three plasma structures.