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.

我们报告了在 2020 年 9 月 20 日夜间通过安装在印度斯利那加克什米尔大学 (KU)（地理纬度 34.08°，东经 74.79°和 25.91 ° N 地磁纬度）。当晚的气辉图像中记录了三种不同的 MSTID 事件，包括日落后 MSTID、午夜 MSTID 和黎明前 MSTID。可以看到日落后和黎明前的 MSTID 向北传播，而在午夜时分观察到的 MSTID 向西传播。由于北半球夜间MSTIDs通常向西南传播，夜间MSTIDs在斯利那加上空向北传播使这一结果变得有趣。更重要的是，在单个夜晚的不同时间观察到三种不同的 MSTID，其传播方向也不相同。我们在本文中提供了这些 MSTID 的详细特征和演变过程。斯利那加地区上空的 MSTID 不寻常的向北运动也得到了解决。这一夜大气重力波的向上传播被认为是北半球夜间MSTIDs这种不寻常传播方向的原因。