The variability of the Earths ionosphere is driven by the sun and the magnetosphere from above and the dynamics of the Earths atmosphere from below. The variability of the low latitude region, especially the one happening after sunset that is usually called equatorial spread F ESF, is very complicated and unpredictable. This post-sunset equatorial ionospheric irregularity is a big threat for applications that depend on trans-ionospheric propagating radio waves. Observational studies have shown clear seasonal and longitudinal variability of ESF peak occurrence rate observed in the American-Atlantic-Africa sector as compared to the other regions however, the physical mechanism for the occurrence of seasonal and longitudinal variations of the irregularity is not well understood. This project is designed to address potential problems like what physical mechanism is responsible for the seasonal and longitudinal variations of the equatorial ionospheric irregularity Is it due to the electrodynamics or atmospheric gravity wave seeding differences In this project supported by EOARD grant, potential scientific problems related to the variability of equatorial ionosphere have been addressed and about sixteen papers and manuscripts are produced. In addition of the five PhD students supported by this grant one has defended his PhD thesis in February 2019.