The upper part of the atmosphere, the ionosphere, is partially ionized, and it is being crossed by many multi-frequency signals of the Global Navigation Satellite System (GNSS) satellites. This unique source of data can be acquired in real time from hundreds of permanent GNSS receivers. The real-time processing providing the distribution of the ionospheric free electrons (Global Ionospheric Maps) can be done as well in real time. We present their updated real-time assessment and combination.

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.

Using model–data analysis we emphasize a new result – formation of the positive daytime disturbances in foF2 and TEC at middle and low latitudes due to n(O)/n(N₂) enhancement during the recovery storm phase. The spatial extent of this phenomenon depends on the longitudinal sector. The positive disturbances in the electron content at heights of 800–20 000 km at high latitudes can appear simultaneously with the negative disturbances in TEC and foF2 due to electron and neutral temperature heating.

This paper presents a data-driven model of the ionospheric electron density that has been developed for the EUMETSAT Polar System - Second Generation mission, with the main goal to improve the inversion of radio occultations for neutral atmospheric sounding. This model has been developed using occultation data from the COSMIC/FORMOSAT-3 satellite, which has been inverted using a LMS-based mechanization of the Abel inversion that implements the separability hypothesis.