[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-P19] 日本3地点での長期観測に基づく中間圏・熱圏夜間大気光の磁気嵐に対する応答の研究: TIMED衛星、イオノゾンデとの比較

*堀田 雄斗¹、塩川 和夫¹、大塚 雄一¹、ユエ ジア²、西岡 未知³ (1.名古屋大学宇宙地球環境研究所、2.NASA Goddard Space Flight Center and Catholic University of America、3.情報通信研究機構)

キーワード：大気光、磁気嵐、中間圏、電離圏、熱圏

We investigated geomagnetic storm responses of six mesospheric and thermospheric nocturnal airglow intensities (OH, O2, O(557.7nm), Na(589.3nm), O(630.0nm), O(777.4nm)) and rotational temperatures of OH and O2, based on superposed epoch analysis of long-term airglow data obtained at three stations over Japan. We used airglow data obtained by the Airglow Temperature Photometers (ATPs) of Optical Mesosphere Thermosphere Imagers (OMTIs) at Rikubetsu (RIK) (43.5N, 143.8E, 2004.3.15-2023.10.31), Shigaraki (SGK) (34.8N, 136.1E, 2010.7.5-2023.10.31), and Sata (STA) (31.0N, 130.7E, 2004.1.1-2023.10.31). The responses were investigated for 46 storms with minimum Dst values less than -100 nT. We found that the intensity of O(557.7 nm) and O2 in the mesosphere and O(630.0 nm) and O(777.4 nm) in the thermosphere increased at 2 and 1 days, respectively, after the start of the storms. No noticeable variations were seen for the OH and O2 rotational temperatures in the mesopause region. One possible reason for the increase of the mesospheric airglow intensity is that the atomic oxygen produced by the dissociation of O2 molecules at high latitude auroral zone are transported to lower latitudes. We analyzed data from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) onboard the TIMED satellite to investigate changes in O mixing ratios before and after these storms. The increase in O mixing ratio tends to be observed by SABER. SABER also shows decrease of O2 volume emission rates and increase of mesospheric temperature after these storms, which were not consistent with ground-based observations. The intensity of thermospheric O(630.0 nm) and O(777.4 nm) airglow depend on the ionospheric F-region electron density. Thus, we investigated the foF2 and h'F data obtained by the ionosondes near these three airglow stations. Slight increases in foF2 were observed one day after geomagnetic storms which is consistent with the observed, increases in the intensity of O(630.0 nm) . The foF2 subsequently decreases for two days after these storms, possibly due to composition change of the middle-latitude ionosphere to cause the negative ionospheric storms. The h'F increases at 1-3 days after the storms, contradicting to the O(630.0 nm) airglow increase.