A top to bottom evaluation of IRI 2007 within the polar cap

Abstract

Monthly median values of ionospheric peak height (hmF 2 ) and density (NmF 2 ), derived from ionosonde measurements at four Canadian High Arctic Ionospheric Network (CHAIN) stations situated within the polar cap and Auroral Oval, are used to evaluate the performance of the International Reference Ionosphere (IRI) 2007 empirical ionospheric model during the recent solar minimum between 2008 and 2010. This analysis demonstrates notable differences between IRI and ionosonde NmF 2 diurnal and seasonal behavior over the entire period studied, where good agreement is found during summer periods but otherwise errors in excess of 50% were prevalent, particularly during equinox periods. hmF 2 is found to be marginally overestimated during winter and equinox nighttime, while also being underestimated during summer and equinox daytime by in excess of 25%. These errors are shown to be related to significant mismodeling of the M(3000)F 2 propagation factor. The ionospheric bottomside thickness parameter (B0) is also evaluated using ionosonde measurements. It is found that both of the IRI's internal B0 models significantly misrepresent both seasonal and diurnal variations in bottomside thickness when compared to ionosonde observations, where errors at times exceed 40%. A comparison is also presented between IRI and Resolute (74.75N, 265.00E) Advanced Modular Incoherent Scatter Radar (AMISR)-derived topside thickness. It is found in this comparison that the IRI is capable of modeling ionospheric topside thickness exceptionally well during winter and summer periods but fails to represent significant diurnal variability during the equinoxes and seasonal variations.

An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

“…This underestimation is most severe at nighttime and during solar maximum. A large discrepancy between the IRI TEC and ESR TEC during the solar maximum (1999)(2000)(2001)(2002) is consistent with the findings of Themens et al (2014) from the latest solar maximum. -An overestimation of the hmF2 occurs both during solar minimum and solar maximum, but it seems to be slightly stronger during nighttime than during daytime.…”

“…Using the ESR data allows us to evaluate the IRI model in the region where the model is known to be less accurate under various conditions. Previous studies have also used observational data to evaluate the IRI model (e.g., Themens et al, 2014;Wichaipanich et al, 2013;Kim et al, 2011;Chuo and Lee, 2008;Lei et al, 2006;Zhang and Holt, 2004), but few of these have evaluated the model at latitudes as high as the auroral zone or the polar cap, or with long enough time series to evaluate the model at different parts of the solar cycle. Brum et al (2011) and Lei et al (2006) used data from ISRs in their studies.…”

“…As expected due to the poor data coverage at high latitudes, they found that the model performed best at midlatitudes. Lei et al (2006) In a study by Themens et al (2014) data from four ionosonde stations located within the polar cap were used to evaluate the hmF2, peak density (NmF2), M(3000)F2 and the bottomside thickness parameter B0 predicted by the IRI-2007 model during the latest extended solar minimum from 2008 to 2010. In addition, data from the Resolute Advanced Modular ISR were used to evaluate the IRI-predicted topside thickness.…”

“…Although Lei et al (2006), Oyeyemi et al (2010) and Themens et al (2014) have compared the IRI model with highlatitude data, such comparisons have mainly been made at midlatitudes. It is therefore highly relevant to evaluate the IRI model for the high-latitude region, and in this study we compare the IRI model with the ESR data from the polar cap and cusp.…”

Resolute Bay Incoherent Scatter Radar observations of plasma structures in the vicinity of polar holes

“…The data on the electron density, ion and electron temperatures, and ion drift velocity are obtained from the measured power spectra using a standard incoherent scatter radar (ISR) technique involving iterative nonlinear least squares fitting and calibration [Evans, 1969;Rishbeth and Williams, 1985;Nicolls et al, 2007]. The RISR-N calibration involves plasma line measurements during summer daytime periods or ionosonde measurements at Resolute during other periods [Bahcivan et al, 2010;Themens et al, 2014]. The noise and system constants are estimated and accounted for during the calibration process [Nicolls et al, 2007].…”