In this work, the correlation between ROTI and S4 is investigated based on a derived mathematical model under the assumption of single screening model for trans-ionospheric signal propagation. The correlation between ROTI and S4 is strongly affected by the variability of the effective velocity, and the correlation coefficient is degraded when the variability increases.The scintillation index S4 depends on the ionospheric irregularities, the effective velocity and the radio propagation path.

Using an empirical approach put forward by Makela et al. (2001), firstly, we propose a novel technique to calibrate OI 777.4 and 630.0 nm emission intensities using COSMIC/FORMOSAT-3 electron density profiles. Next, electron density maximum (Nm) and its height (hmF2) of the F layer are derived from the information of two calibrated intensities. Sample Nm and hmF2 maps are also generated to show the usefulness of this technique in studying ionospheric processes.

The work presented in this paper was done in the frame of an ESA activity. The aim of this project was to study ionosphere disturbances liable to impact navigation systems. This project has been running over several years, allowing enough data acquisition to gain sufficient knowledge of ionosphere variability. It was launched to support the European Satellite-Based Augmented System (EGNOS), also considering a possible extension of the system over Africa.