First Results on Characteristics of Nighttime MSTIDs Observed Over South Africa: Influence of Thermospheric Wind and Sporadic E

This paper reports the climatology of medium-scale traveling ionospheric disturbances (MSTIDs) observed between September 2018 and August 2019 in nighttime redline airglow intensity measurements from an all-sky imager located Sutherland, South Africa (32.4°S, 20.8°E; magnetic latitude: 40.7°S). The MSTIDs appeared as either single or multiple dark bands, commenced mostly before midnight, predominantly occurred during southern winter solstice. They primarily propagated westward with speeds 31–127 m/s. periods wavelengths multi-band were ranges 26–155 min 134–578 km, respectively, while temporal spatial scales band 11–30 43–143 respectively. Analysis neutral wind a co-located Fabry-Perot interferometer showed that thermospheric was northeastward evenings MSTID occurrence favored propagation least restricted direction by background wind. Based on data nearby ionosondes, accompanied sporadic E spread-F structures. From seasonal occurrences well prevalent directions, it is concluded Perkins instability most likely source majority MSTIDs, remainder may be seeded gravity waves.