Developing 4-D ionospheric specification over U.S. with a new TEC-based ionospheric data assimilation system (TIDAS)

Accurately imaging and modeling the 4D spatial-temporal variation of the Earth's ionosphere has always been a challenging task in the space weather community, since the ionosphere is a highly variable nonlinear system which exhibits not only remarkable climatological variations but also significant weather disturbances. In the past decades, with the ever-increasing availability of GNSS measurements from ground-based receivers and space-borne radio occultation data such as COSMIC-1/2, remarkable progress has been made in the data assimilation technique to improve the overall accuracy of ionospheric nowcast and forecast. However, there still exists a strong need to provide retrospective specification of the storm-time sophisticated four-dimensional electron density gradient with high spatial-temporal resolution so that detailed localized ionospheric variability and weather disturbances could be better reproduced and understood. Recently, we have developed a new regional ionospheric data assimilation system to issue high-resolution (1 deg × 1 deg × 20 km × 5 min) four-dimensional electron density products over the Continental U.S., which is built upon the massive GNSS line-of-sight TEC data processed at MIT Haystack Observatory, radio occultation data from COSMIC-1/2 measurements, Millstone Hill incoherent scatter radar measurements, and JASON TEC data. This new data assimilation product specifies the occurrence and evolution of midlatitude ionosphere density gradients (e.g., storm-enhanced density, main trough) as well as other meso-scale ionospheric structures. This presentation will describe the data assimilation method, validation, as well as some preliminary results.