Regional ionosphere specification by assimilating ionosonde data into the SAMI2 model

Abstract This paper explains an algorithm of estimating the regional ionosphere at mid-latitude by assimilating ionosonde measured data into a first principle physics-based model (SAMI2-CNU). It has been known that many first principle models underperform due to inadequate input drivers, such as neutral winds and compositions in the background thermosphere. As a pilot study, equivalent meridional winds and electron density scale factors were derived every 15 minutes using F2 peak heights (hmF2) and densities (NmF2) obtained from Jeju ionosonde (33.43N°, 126.30 E°), and then were used as inputs to SAMI2-CNU. SAMI2-CNU is an in-house revised version of the 2- dimensional ionosphere model (SAMI2), developed at Naval Research Laboratory ( Huba et al., 2000 , Kim and Kim, 2016 ). Results are obtained at a meridional plane of 127° geographic longitude on a geomagnetically quiet day of each season in the year 2014. SAMI2-CNU was found to predict the next 15-minute hmF2s and NmF2s reasonably close to measured values at Jeju, Icheon (37.14 N°, 127.54 E°) and Okinawa (26.68 N°, 128.15 E°) (sites near the same meridional plane), showing a superior performance, compared to the original SAMI2 and the International Reference Ionosphere (IRI) 2016 model. Thus, this study demonstrates that a physic model, SAMI2-CNU, can be used as a nowcast model of the regional mid-latitude ionosphere by assimilating ionosonde data in near-real time.