[P-EM13] 太陽地球系結合過程の研究基盤形成

[PEM13-08] Temperature variations in the D- and E-region polar ionosphere during stratospheric sudden Warming

*小川 泰信¹、野澤 悟徳²、堤 雅基¹、冨川 喜弘¹、Hall Chris⁴、Haggstrom Ingemar³ (1.国立極地研究所、2.名古屋大学宇宙地球環境研究所、3.EISCAT HQ、4.UiT The Arctic University of Norway)

キーワード：極域電離圏、EISCAT、電離圏D層

We analyzed ion temperature and velocity observed by the European Incoherent Scatter (EISCAT) UHF radar at Tromsoe (69.6 deg N, 19.2 deg E) during a stratospheric sudden warming (SSW) that occurred in January-February, 2017. The zonal ion velocities at 85-100 km height reversed approximately 8 days earlier than the zonal wind reversal in the upper stratosphere and the ion temperature at 85-95 km decreased simultaneously with the zonal ion velocity reversal at the same altitude. We found that the time variations of ion temperature in the daytime are close to those of neutral temperature derived from the ambipolar diffusion coefficients obtained with the Nippon/Norway Tromsoe Meteor Radar (NTMR) data at the same altitude even when geomagnetic activity is moderate. This suggests that the D- and lower E-region ion temperature in the daytime is a good proxy for neutral temperature at the same altitude. We will explain the reliable ion temperature derivation in the D-region and its limitation, and also discuss relationship between ion temperature and vertical ion velocity variations at 85-95 km measured with the EISCAT UHF radar.