Terdiurnal signatures in sporadic E layers at midlatitudes

Global Positioning System radio occultation measurements by the FORMOsa SATellite mission3/Constellation Observing System for Meteorology, Ionosphere and Climate satellites were used to analyse the behaviour of the signature of the terdiurnal tide in sporadic E (ES) layers at midlatitudes (43–63 N). According to theory, the occurrence of ES is expected when the vertical zonal wind shear, which is mainly owing to solar tides, is negative. 4 yr means, based on 3-monthly running mean zonal means from December 2006–November 2010, were constructed for the terdiurnal oscillation in the occurrence frequency of ES. Comparison of the results with VHF meteor radar observations of the terdiurnal tide and the 8 h oscillation in the vertical zonal wind shear at Collm, Germany (51.3 N, 13 E) shows a clear correspondence between the 8 h in ES and in wind shear signature.