Tides Signature Detection in Global Sporadic E Occurrence Rate, Using FORMASAT-3/COSMIC Data

Abstract:

Sporadic E (Es) is a transient phenomenon where thin layers of enhanced ion concentration appear in the ionospheric E region (90-120 km altitude). Es can influence radio propagation, and its global characteristics have been of great interest to radio communications and navigation. Atmospheric diurnal and semi-diurnal tides play an essential role in the Es layers formation by causing horizontal wind shears at E-region heights, which give rise to the vertical motions of ions and electrons. The purpose of this research is to study the role of atmospheric solar and lunar tides in characteristics of global Es occurrence. Radio occultation data from FORMASAT-3/COSMIC mission of 11 years (2007 to 2017), which provide a complete global coverage has been used.

The results show that Es occurrence is a mid-latitude phenomenon with significant seasonal dependence. The occurrence rate is highest during the local summer, reaching almost 60% in some years. Tidal modulations at periods of 12 and 24 hours are clearly identified in the Es occurrence, having a peak of 4 to 8% in the altitude range of 95 to 115 km. This study establishes the global climatology of diurnal and semi-diurnal tides in Es.