3-D Ionospheric Imaging Over the South American Region With a New TEC-Based Ionospheric Data Assimilation System (TIDAS-SA)

This study has developed a new TEC-based ionospheric data assimilation system for 3-D regional ionospheric imaging over the South American sector (TIDAS-SA) (45 degrees S-15 degrees N, 35 degrees-85 degrees W, and 100-800 km). The TIDAS-SA data assimilation system utilizes a hybrid Ensemble-Variational approach to incorporate a diverse set of ionospheric data sources, including dense ground-based Global Navigation Satellite System (GNSS) line-of-sight Total Electron Content (TEC) data, radio occultation data from the Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2), and altimeter TEC data from the JASON-3 satellite. TIDAS-SA can produce a reanalyzed three-dimensional (3-D) electron density spatial variation with a high time cadence, yielding spatial-temporal resolution of 1 degrees (latitude) x 1 degrees (longitude) x 20 km (altitude) x 5 min. This allows us to reconstruct and study the 3-D ionospheric morphology with multi-scale structures. The performance of the data assimilation system is validated against independent ionosonde and in situ measurements through an experiment for a strong geomagnetic storm event on 03-04 November 2021. The results demonstrate that TIDAS-SA can provide detailed and altitude-resolved information that accurately characterizes the storm-time ionospheric disturbances in vertical and horizontal domains over the equatorial and low-latitude regions of South America. Accurately imaging the 3-D variation of the ionosphere and monitoring its temporal evolution in key areas of interest has consistently been an essential yet challenging task. This study has developed a novel TEC-based ionospheric data assimilation system (TIDAS-SA) for ionospheric imaging over the South American sector, where the ionosphere exhibits the characteristic equatorial and low latitude anomalies. TIDAS-SA utilizes a hybrid Ensemble-Variational approach to assimilate a variety of ground-based and space-borne ionospheric measurements, which can yield high-fidelity electron density distribution with high spatial-temporal resolution to represent the regional and localized ionospheric morphology within the 3-D domain. This capability enables TIDAS-SA as a powerful tool for providing detailed, altitude-resolved information that contributes to advancing our current understanding of ionospheric disturbances during geomagnetic storms in the equatorial and low-latitude ionosphere over South America. A new TEC-based ionospheric data assimilation system is developed for regional ionospheric imaging over the South American sector High-resolution ionospheric electron density reconstruction represents characteristic equatorial 3-D ionospheric morphology and dynamics The low-latitude positive ionospheric storm over South America during the 03-04 November 2021 storm was effectively reconstructed