Assimilation of GIRO Data in IRI for Global Near Real-Time Ionospheric Specification

Accurate, prompt, and detailed global 3D ionospheric plasma specification is required for many space weather applications. The Global Ionospheric Radio Observatory (GIRO) is one of the prime suppliers of real-time measurements from a network of ground-based remote sensing radio instruments, digisondes. We present a new approach to the assimilative modeling based on GIRO data called Real-Time Assimilating Mapping (RTAM) that smoothly transforms climatology maps of the main ionospheric characteristics in the empirical International Reference Ionosphere (IRI) model so that they match available observations. The key technological component of RTAM is the elastic transformation method that preserves integrity of the IRI's empirical specification while modifying the model to match the sensor data. To accomplish the task, the transformation technique keeps intact the proven IRI formalism for ionospheric specification (specific choice of expansion base function in time and space) and computes only corrections to the expansion coefficients. Such adjustment technique provides important physics-based constraints to the challenging task of assimilating real-time data available from the limited number of GIRO locations without introducing computational artifacts of unconstrained interpolation. Early results of the RTAM prototype operation are encouraging; we will present comparison statistics and discuss practical aspects of operating RTAM infrastructure in various scenarios that require fine detail of ionospheric behavior in conditions far from average quiet-time expectations.