The TaiWan Ionospheric Model
The TaiWan Ionospheric Model (TWIM) developed in 2008 is a three-dimensional numerical and phenomenological model of ionospheric electron density (Ne). The TWIM has been constructed from global distributed ionosonde foF2 and foE data and vertical Ne profiles retrieved from FormoSat3/COSMIC GPS radio occultation measurements.
Source: Wikipedia — The TaiWan Ionospheric Model (CC BY-SA 4.0)