Maps of ionospheric F2-layer characteristics derived from GPS radio occultation observations

The Global Positioning System (GPS) radio occupation (RO) technique has been used to receive multi-channel GPS carrier phase signals from low Earth orbiting (LEO) satellites and demonstrate active limb sounding of the Earth's ionosphere. Applying Abel inversion through compensated total electron content (TEC) values, the GPS RO observations can obtain ionospheric electron density (n_e) profiles and then scale F2-layer characteristics including/o.F.2 and hmF2, especially, hmF2 that cannot be directly deduced from ionosonde observations. From the GPS/MET and FS3/COSMIC missions, we can collect on average two hundred and eighteen hundred vertical n_e profiles, respectively, within one day. The retrieved./aF2 and hmF2 results have been used to produce numerical maps representing complex properties on a world-wide scale. This paper presents a physically appealing representation of foF2 and hmF2 medians based on GPS RO data. The derived numerical maps have also been examined by ground-based ionosonde data.