Terdiurnal signatures in sporadic E layers at midlatitudes

Abstract. Global Positioning System radio occultation measurements by the FORMOsa SATellite mission-3/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 (E_S) layers at midlatitudes (43–63° N). According to theory, the occurrence of E_S 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 E_S. 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 E_S and in wind shear signature.