Evidence for simultaneous occurrence of periodic and single dark band MSTIDs over geomagnetic low-mid latitude transition region

We report a unique simultaneous occurrence of two plasma structures using a 630.0 nm all-sky airglow imager in Hanle, India. The characteristics indicate that the observed structures are Medium Scale Travelling Ionospheric Disturbances (MSTIDs) of different types, namely periodic and single dark band. Based on previous understandings of Perkins instability, we explore the role of polarization electric field within MSTIDs using complementary observations from a nearby digisonde. We propose that the MSTIDs involve different seeding processes. This study provides crucial information in elucidating the generation of MSTIDs and helps in understanding the F-region electrodynamics over geomagnetic low-mid latitude transition region.