Abstract
A total of 4991 ionograms recorded from April 1997 to December 2017 by the Millstone Hill Digisonde (42.6°N, 288.5°E) were considered, with simultaneous Ne(h)[ISR] profiles recorded by the co-located Incoherent Scatter Radar (ISR). The entire ionogram dataset was scaled with both the Autoscala and ARTIST programs. The reliability of the hmF2 values obtained by ARTIST and Autoscala was assessed using the corresponding ISR values as a reference. Average errors Δ and the root mean square errors RMSE were computed for the whole dataset. Data analysis shows that both the Autoscala and ARTIST systems tend to underestimate hmF2 values with |Δ| in all cases less than 10 km. For high magnetic activity ARTIST offers better accuracy than Autoscala, as evidenced by RMSE[ARTIST] < RMSE[Autoscala], under both daytime and nighttime conditions, and considering all hours of the day. Conversely, under low and medium magnetic activity Autoscala tends to estimate hmF2 more accurately than the ARTIST system for both daytime and nighttime conditions, when RMSE[Autoscala] < RMSE[ARTIST]. However, RMSE[Autoscala] slightly exceeds RMSE[ARTIST] for the day as a whole. RMSE values are generally substantial (RMSE > 16 km in all cases), which places a limit on the results obtainable with real-time models that ingest ionosonde data.
Highlights
The ionosphere is a highly variable medium affecting HF radio propagation, which is used in long-distance communication and detection
A total of 4991 ionograms recorded from April 1997 to December 2017 by the Millstone Hill Digisonde (42.6◦N, 288.5◦E) were considered, with simultaneous Ne(h)[ISR] profiles recorded by the co-located Incoherent Scatter Radar (ISR)
The various long-term models available today are based on ionosonde data with hmF2 obtained from the vertical electronic density profile Ne(h), which in turn is derived from the ionogram
Summary
The ionosphere is a highly variable medium affecting HF radio propagation, which is used in long-distance communication and detection. The various long-term models available today are based on ionosonde data with hmF2 obtained from the vertical electronic density profile Ne(h), which in turn is derived from the ionogram This was first achieved applying a polynomial inversion method that required the intervention of an operator [6], subsequently being automated [7,8,9]. In this work we consider the accuracy achieved in hmF2 estimation by two automatic systems for ionogram interpretation: ARTIST [7,8,9], and Autoscala [20,21] These data feed real-time ionospheric models and affect their performance. The same data populate international databases and constitute the measurements on which future retrospective studies will be based, at a historical moment when the huge resources necessary for manual data validation are often lacking
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