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

Y Yamazaki,M.J Kosch,Y Ogawa,D.R Themens

doi:10.1051/swsc/2016029

Abstract

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.

Highlights

Incoherent scatter radars are very powerful remote-sensing tools for upper atmospheric studies
The present study focused on the ion temperature climatology in the polar region during the International Polar Year (IPY)
The ESR ion temperature climatology is presented in Figure 1: (a), (d), and (g) for winter; (b), (e), and (h) for equinox; and (c), (f), and (i) for summer

Summary

Introduction

Incoherent scatter radars are very powerful remote-sensing tools for upper atmospheric studies. Sojka et al (2011) presented the ion temperature climatology at 300 km using ESR and PFISR measurements during the IPY They compared the observations with the International Reference Ionosphere 2007 (IRI-2007) (2012) pointed out that the discrepancy between quiettime ESR ion temperature and NRLMSISE-00 neutral temperature can be up to 250 K, arguing that there are significant heat sources that are not taken into account They attempted to identify the heat source using the general circulation model introduced by Miyoshi & Fujiwara (2003), but had difficulties in reproducing the observations, as their model did not include a self-consistent ionosphere. General Circulation Model (TIE-GCM), which considers mutual coupling of the thermosphere and ionosphere (Richmond et al 1992; Qian et al 2014) This provided us with the first opportunity to evaluate various physical processes contributing to the ion temperature in the polar region, such as electron heating and ion-neutral frictional heating.

Incoherent scatter radars

TIE-GCM

IRI-2012

Results and discussion

Summary and conclusions