Signature of the 27-day oscillation in the MLT tides and its relation with solar radiation at low latitudes

The modulation of the dominant atmospheric tides (i.e. diurnal, semidiurnal and terdiurnal) in the mesosphere and lower thermosphere (MLT) is investigated using long-term meteor wind database from three Southern hemispheric low-latitude locations, São João do Cariri (7.4° S, 36.5° W), Cachoeira Paulista (22.7° S, 45° W) and Santa Maria (29.7° S, 53.7° W). The spectral analysis reveals an evident and intermittent signature of a 27-day oscillation in the tidal amplitudes. Relationship between the 27-day tidal modulation in the MLT and solar rotation is looked into utilizing solar UV flux (Lyman-α) that indicates a conspicuous linkage of the tides with the solar short-term variability. The strong correlation between the solar variability and tidal modulation in the concerned period with positive lags at certain intervals may indicate predominate solar influence on the MLT tides. Potential involvement of the lower, middle and upper atmospheric dynamics and chemistry to support the observed oscillation feature is deemed plausible. [graphic not available: see fulltext]