Dr. Zama Katamzi-Joseph will give a lecture as part of the CLASP Seminar Series. Please join us!

Title: “Climatology of Thermospheric Neutral Winds and TIDs over South Africa: Observations from 630 nm Fabry-Perot Interferometer and All-sky Imager”

Abstract: Nighttime traveling ionospheric disturbances are detected from 630 nm airglow measurements from an all-sky imager in Sutherland, South Africa (geographic coordinates: 32.4° S, 20.8° E; magnetic latitude: 40.7° S). To understand the influence of the background winds on the propagation of the TIDs, we used wind data from a co-located Fabry-Perot interferometer. For this study the measurements used were taken during the period of September 2018 and August 2019. A total of 52 TIDs were identified, the majority occurring during the local winter season. The overall speed, azimuth, wavelength and periods of the majority of these TIDs were 50 – 200 m/s, 0 – 338 degrees, 150 – 400 km, 19 – 106 minutes, respectively. There was no detected seasonal trend on their characteristics. The TIDs propagated mostly in the west direction regardless of the season. Analysis of the FPI wind data revealed that the mean background zonal winds varied between -72 and 126 m/s and were strongly eastward before midnight. They reversed flow direction to westward around local midnight in summer whereas in winter the reversal occurs closer to local sunrise. In addition, zonal winds have lower (higher) magnitudes in summer (winter). Meanwhile the mean background meridional winds are mostly equatorward for most of the year until around winter where they flow poleward in early evening and then reverse direction around 22 UT (00 LT). The meridional winds varied between -52 and 109 m/s, and contrary to the zonal winds their amplitudes were higher in summer and lower in winter. The dominance of westward propagating TIDs is explained by the fact that the TIDs mostly had higher velocities and/or propagate against or perpendicular to the background wind.