Enhancements and validation of the real-time optimised D-Region HF radio absorption model

The Optimised D-Region Absorption Model (ODRAM) provides global nowcasts and forecasts of ionospheric HF radio wave absorption. This results from ionisation by solar flares, Solar Energetic Particles (SEP), and auroral electron precipitation. Parameters of ODRAM are optimised in near real time by assimilating satellite measurements, geomagnetic index estimates, and direct measurements of absorption made by riometers at high latitudes.
In this presentation, we validate two new empirical models for the solar flare (shortwave fadeout) model developed from riometer measurements at 22 locations in Canada and Finland recorded during 126 X-class flares in Solar Cycle 23. We then discuss improvements to the empirical Auroral Absorption (AA) models obtained by removing artefacts in the entire measurement archive and an assessment is made of the optimal AA model driver parameters (selected from real-time geomagnetic index estimates or proxies derived from in situ solar wind/IMF measurements).
Finally, we assess the combined model performance for a period of active space weather in September 2017. Issues relating to riometer placement, measurement calibration, and artefact removal will be addressed.