On the Use of SuperDARN Ground Backscatter Measurements for Ionospheric Propagation Model Validation

Prior to use in operational systems, it is essential to validate ionospheric models in a manner relevant to their intended application to ensure satisfactory performance. For Over-the-Horizon radars (OTHR) operating in the high-frequency (HF) band (3-30 MHz), the problem of model validation is severe when used in Coordinate Registration (CR) and Frequency Management Systems (FMS). It is imperative that the full error characteristics of models is well understood in these applications due to the critical relationship they impose on system performance. To better understand model performance in the context of OTHR, we introduce an ionospheric model validation technique using the oblique ground backscatter measurements in soundings from the Super Dual Auroral Radar Network (SuperDARN). Analysis is performed in terms of the F-region leading edge (LE) errors and assessment of range-elevation distributions using calibrated interferometer data. This technique is demonstrated by validating the International Reference Ionosphere (IRI) 2016 for January and June in both 2014 and 2018. LE RMS errors of 100-400 km and 400-800 km are observed for winter and summer months, respectively. Evening errors regularly exceeding 1,000 km across all months are identified. Ionosonde driven corrections to the IRI-2016 peak parameters provide improvements of 200-800 km to the LE, with the greatest improvements observed during the nighttime. Diagnostics of echo distributions indicate consistent underestimates in model NmF2 during the daytime hours of June 2014 due to offsets of -8 degrees being observed in modeled elevation angles at 18:00 and 21:00 UT. Models of the ionized upper atmosphere, a region known as the ionosphere, must be validated using appropriate techniques prior to their use in operational systems. This is of greatest importance for Over-the-Horizon radars (OTHR) that rely on the reflection of radio waves in the 3-30 MHz band from the ionosphere for their operation. The accuracy of OTHR is largely related to the performance of the model ionosphere used to establish target positions, and so it is essential to understand how models behave under different circumstances. We introduce a new technique for validating models using measurements from the Super Dual Auroral Radar Network (SuperDARN) of research radars. Using a dominant feature present within these radar echoes, we perform an example validation of the International Reference Ionosphere (IRI) 2016 by modeling the expected path of radio waves. The performance is seen to be best during winter and typically worse in the evening. Using further information present within the measurements, we diagnose the likely cause of errors to be due to underestimates in a key model parameter. This is confirmed when we offset model parameters using direct measurements of the ionosphere and observe a significant improvement in model performance. We introduce an ionospheric model validation technique using SuperDARN ground backscatter Performance of the IRI-2016 is best during the daytime of January 2014 and 2018, whilst sporadic-E in June causes significant degradations IRI-2016 range errors are seen to be most significant near the terminator and during the nighttime