New Findings Relating Tidal Variability and Solar Activity in the Low Latitude MLT Region

摘要

Mesospheric winds have been measured by meteor radar at Cachoeira Paulista (22.7°S; 45°W) since April 1999. The tidal components were analyzed over about 21 years of available data exhibiting an annual and semi-annual variation. Amplitudes of meridional diurnal (semidiurnal) tide are on averaged 30% (28%) and the zonal ones are 14% (20%) stronger at solar minimum than at solar maximum. The anticorrelation between F10.7 cm solar flux and amplitudes of the semiannual oscillation of diurnal and semidiurnal tides is presented. Additionally, the sporadic E (Es) layers occurrence has an anti-correlation with solar activity due to the tidal wind variation. A discussion about the physical mechanism is performed in terms of the particle precipitation during High-Speed Stream (HSS) events according to the solar cycle. Finally, a superposed epoch analysis of the tidal amplitudes during the HSS events in 2018 is presented. And a slight increase in all tidal components is seen when the structure reached the Earth and in the following days showing that indeed the electron precipitation during HSS events affect the tidal amplitudes.