Northward propagation of medium scale traveling ionospheric disturbances over Srinagar, J and K India

Abstract We report some interesting medium scale travelling ionospheric disturbances (MSTIDs) observed during the night of September 20, 2020 through an all sky CCD imager installed in Kashmir University (KU), Srinagar, India (34.08° N geographic latitude, 74.79° E and 25.91° N geomagnetic latitude). Three different MSTID events including a post-sunset MSTID, a mid-night MSTID and a pre-dawn MSTID are recorded in the airglow images during this night. The post-sunset and pre-dawn MSTIDs are seen to propagate northward while the MSTID observed near midnight time propagates towards west. As the MSTIDs during the night times over the northern hemisphere generally propagate southwestward, the northward propagation of nighttime MSTIDs over Srinagar makes this result an interesting one. More importantly, three different MSTIDs are observed at different times during the single night whose directions of propagation are not same either. We provide the detailed characteristics and evolution processes of these MSTIDs in this paper. The unusual northward motion of the MSTIDs over the Srinagar region is also addressed. The upward propagation of atmospheric gravity waves during this night is believed to be the responsible candidates for such unusual propagation direction of nighttime MSTIDs over the northern hemisphere.