With an improved method for retrieving the equatorial F region irregularities (EFIs) from radio occultation measurements, a huge amount of S4 index profiles from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites is employed to study the solar cycle variation of global EFIs during the period of 2007 to 2017. This full solar cycle data show that impacts of the solar activity on the occurrence rates and heights of EFIs are notable and complex. The occurrence rates of EFIs at higher altitude (greater than 500 km) increase with increasing the solar activity. The mean heights ((Formula presented.)) and heights standard deviation (σh) of EFIs at higher altitudes do not show clearly the solar activity dependence. On the other hand, the occurrence rates of EFIs at entire altitudes (from 150 to 800 km) do not have clear relation with the solar activity. The (Formula presented.) and σh of EFIs at entire altitudes increase with increasing the solar activity. Moreover, the dependence of the occurrence rates of EFIs on the solar activity are the strongest in the equinoxes, weaker in winter and weakest in summer. The electric fields and corresponding seasonal variation can account for the EFIs occurrence and height variation versus solar activities, and the EFIs at low altitudes seem to be related to the seed associated with atmospheric gravity wave.
All Science Journal Classification (ASJC) codes
- Space and Planetary Science