Abstract:
This paper reports a rare interaction between two fronts of nighttime medium scale traveling
ionospheric disturbances (MSTIDs) and associated phenomena observed over geomagnetic low-mid latitude
transition region on a geomagnetically quiet night (Ap = 5) of 21 May 2020. The event was observed for nearly
8 hours in O(1
D) 630.0 nm airglow images captured by an all-sky imager installed at Hanle (32.7°N, 78.9°E;
Mlat. ∼24.1°N), Leh Ladakh, India and supplemented by a digisonde and a global positioning system receiver
located within the imager's field of view (FOV). The images revealed a slow-moving MSTID front being
followed by a fast-moving MSTID front, both traveling southwestward. The third front of the MSTID caught
up with the second one, initiating the interaction. As a consequence, a plasma channel was created during the
interaction and the MSTIDs' fronts began decaying. Subsequently, they became thin strips and later dissipated
within the FOV of the imager. The polarization electric field of the merged region of the two interacting
MSTIDs' fronts played a key role in creating the plasma channel. In the later hours of the night, another MSTID
with a rotating front was observed, which is a rarely reported phenomenon. The horizontal gradient in the
westward wind is a plausible reason for the observed rotation. This study elucidates the complex nature of
geomagnetic low-mid latitude transition region.
