Abstract/Summary

We present observations during the interval 2006-2014 of 27-day and 13.5-day periodic oscillations in the ionospheric sporadic E (Es) layer. This is a thin, dense layer composed of metallic ions in the Earth's upper atmosphere between 90 and 130 km. Lomb-Scargle spectral and wavelet analyses reveal that these pronounced periodicities observed from ground-based ionosondes and GPS/GNSS radio occultations are associated with high-speed solar winds generated from persistent coronal holes on successive 27-day solar rotations. The 27-day and 13.5-day oscillations in the Es layers are dependent on latitude, showing a higher magnitude of periodicities at low-latitudes between 0 {15 and high-latitudes between 45 {90 (10%{14%) than those at mid-latitudes between 15 {45 (4%{10%). The 27-day and 13.5-day oscillations in the high-latitude Es layers correlate well with the geomagnetic activity Dst and Ap indices, and these periodic oscillations become more signi cant at the solar maximum (2000{2003, and 2011{2014) than the solar minimum.