JpGU-AGU Joint Meeting 2017

講演情報

[EE] ポスター発表

セッション記号 P (宇宙惑星科学) » P-EM 太陽地球系科学・宇宙電磁気学・宇宙環境

[P-EM11] [EE] Mesosphere-Thermosphere-Ionosphere Coupling in the Earth's Atmosphere

2017年5月24日(水) 15:30 〜 17:00 ポスター会場 (国際展示場 7ホール)

コンビーナ:Chang Loren(Institute of Space Science, National Central University)、Liu Huixin(九州大学理学研究院地球惑星科学専攻 九州大学宙空環境研究センター)、齊藤 昭則(京都大学大学院理学研究科地球物理学教室)、Tzu-Wei Fang

[PEM11-P06] Long-term statistical analysis of horizontal phase velocity distribution of mesosphere and ionosphere waves in airglow images at Rikubetsu and Shigaraki, Japan

*土屋 智1塩川 和夫1竹生 大輝1藤波 初木1大塚 雄一1松田 貴嗣2江尻 省2中村 卓司2山本 衛3 (1.名古屋大学宇宙地球環境研究所、2.国立極地研究所、3.京都大学生存圏研究所)

キーワード:AGWs, MSTIDs, spectral analysis

Atmospheric gravity waves (AGWs) transport momentum from the troposphere into the mesosphere and the thermosphere. The momentum deposit through wave breaking causes the large-scale pole-to-pole circulation. The vertical propagation of AGWs depends on the horizontal phase velocity. Thus, investigation of the horizontal phase-velocity characteristics of AGWs helps us to understand the dynamical variation of middle and upper atmosphere. On the other hand, the propagation direction of medium-scale traveling ionospheric disturbances (MSTIDs) seems to be different at different latitudes. However, the cause which determines their propagation direction has not been understood.

A new spectral analysis method has been developed to obtain power spectra in the horizontal phase velocity by using the 3-D FFT technique [Matsuda et al., JGR, 2014]. Takeo et al. (submitted to JGR, 2017) studied horizontal parameters of AGWs and MSTIDs over 16 years by using airglow images at wavelengths of 557.7 nm (emission altitude: 90-100 km) and 630.0-nm (200-300 km) obtained at Shigaraki, Japan (34.8N, 136.1E) which is located at the middle part of Japan.

In this study, we have applied the same spectral analysis technique to the 557.7-nm and 630.0-nm airglow images obtained at Rikubetsu, Japan (43.5N, 143.8E), which is at the northern edge of Japan, for 16 years from 1999 to 2014. We examined similarities and differences of horizontal wave spectra between Shigaraki and Rikubetsu over 16 years to see their dependence on locations.

The propagation direction of AGWs is northeastward in summer and southwestward in winter at both Shigaraki and Rikubetsu, but yearly variation of power spectral density is different between these two stations. In summer, the propagation direction of AGWs is northeastward irrespective of the phase velocity, probably due to wind filtering of these waves by the mesospheric jet. However, in winter, low phase-velocity waves (20-100 m/s) propagate to southwest, but high phase-velocity waves (100-150 m/s) propagate to southeast at both Shigaraki and Rikubetsu, suggesting reflection of westward high-velocity waves at both stations by the mesospheric jet. For MSTIDs, there is a negative correlation between yearly variation of powers spectral density and F10.7 flux at both sites. Propagation direction is southwestward in all season at both Shigaraki and Rikubetsu. The sub-peak at northeastward MSTIDs is larger in Rikubetsu than in Shigaraki. This may suggest latitudinal dependence of northeastward-moving MSTIDs, though further analysis will be needed for data at different stations.