The Real‐Time Advanced Ionospheric Data Assimilation (AIDA) Model

Abstract The Advanced Ionospheric Data Assimilation (AIDA) is a real‐time data assimilation model of global 3D ionosphere and plasmasphere electron density. Changes in the local space environment can occur on very short timescales, particularly during disturbed geomagnetic conditions. This space weather has an impact on many modern systems including Global Navigation Satellite System (GNSS) signals and High Frequency radio communications. To provide an ionospheric specification in real‐time, AIDA ingests data streams from over 2000 GNSS receivers, along with ionosonde‐derived characteristics. These measurements are assimilated using a particle filter into the empirical NeQuick ionosphere model and Neustrelitz Plasmasphere Model. The GNSS receiver Differential Code Biases are solved self‐consistently using Rao‐Blackwellized particle filtering. AIDA consists of a real‐time Ultrarapid model and a near‐real‐time Rapid model at a 90‐min latency. These models are also forecast six hours into the future, meaning AIDA produces two separate nowcasts of the current ionospheric state (Ultrarapid and the 90‐min forecast of the Rapid product). AIDA is assessed using an operational validation program which shows that the Rapid 90‐min forecast model provides the best nowcast performance during quiet conditions, with improvements of in and root mean square error (RMSE) when compared to the background. The Ultrarapid model provides the best nowcast during disturbed conditions, with improvements of in RMSE. Both the Rapid and Ultrarapid models are also validated using in situ electron density measurements from Swarm, showing overall global improvement in electron density specification.