High-latitude ion temperature climatology during the International Polar Year 2007-2008

This article presents the results of an ion temperature climatology study that examined ionospheric measurements from the European Incoherent SCATter (EISCAT) Svalbard Radar (ESR: 78.2° N, 16.0° E) and the Poker Flat Incoherent Scatter Radar (PFISR: 65.1° N, 212.6° E) during the year-long campaign of the International Polar Year (IPY) from March 2007 to February 2008. These observations were compared with those of the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM), as well as the International Reference Ionosphere 2012 (IRI-2012). Fairly close agreement was found between the observations and TIE-GCM results. Numerical experiments revealed that the daily variation in the high-latitude ion temperature, about 100-200 K, is mainly due to ion frictional heating. The ion temperature was found to increase in response to elevated geomagnetic activity at both ESR and PFISR, which is consistent with the findings of previous studies. At ESR, a strong response occurred during the daytime, which was interpreted as a result of dayside-cusp heating. Neither TIE-GCM nor IRI-2012 reproduced the strong geomagnetic activity response at ESR, underscoring the need for improvement in both models at polar latitudes.