A Top to Bottom Evaluation of IRI 2007 within the Polar Cap

Abstract

Monthly median values of ionospheric peak height (hmF2) and density (NmF2), 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 NmF2 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. hmF2 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)F2 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.

Key Points

• IRI 2007 is evaluated within the polar cap region
• Diurnal and seasonal variations in the IRI 2007 F2 peak are poorly represented
• IRI 2007 topside thickness demonstrates notable agreement on the annual mean