Comparison of ionospheric bottomside profile parameters (B0 & B1) from FORMOSAT-7/COSMIC-2 radio occultation profiles with Digisonde and IRI-2020 model
摘要
In this paper, we present a comprehensive validation of bottomside electron density profile (EDP) thickness (B0) and shape (B1) parameters derived through least-square fitting of FORMOSAT-7/COSMIC-2 radio occultations with the coincident-colocated Digisonde EDPs at 24 locations spanning equatorial, low-, and mid-latitude regions and the default bottomside modeling option in the latest edition of the International Reference Ionosphere model (IRI-2020). These parameters are essential descriptors of the ionospheric bottomside morphology, which are critical for characterizing the vertical structure of the ionosphere and are influenced by solar flux, geomagnetic activity, and space weather dynamics. Leveraging a large dataset from COSMIC-2, we employed rigorous quality constraints through visual inspections and defined exclusion criteria to identify the most representative profiles for investigating the diurnal, seasonal, and longitudinal variations of the parameters as a function of local time during the period from 2020 to 2022, corresponding to the ascending phase of solar cycle 25. The results demonstrate that COSMIC-2 derived B0 and B1 parameters have better agreement with Digisonde observations than those predicted by IRI-2020, highlighting the significance of COSMIC-2 profile parameters towards improvement in empirical ionosphere models.