[P-EM13] Coupling Processes in the Atmosphere-Ionosphere System

[PEM13-P17] Relationship between the time scale of OH airglow enhancements detected at the Syowa Station and the variations of the background atmosphere.

*Satoshi Ishii¹, Hidehiko Suzuki¹, Masaki Tsutsumi^2,3, Makoto Taguchi⁴, Mitsumu K. Ejiri^2,3, Takanori Nishiyama^2,3, Akira Kadokura^5,2,3 (1.Meiji university, 2.National Institute of Polar Research, 3.SOKENDAI, 4.Rikkyo University, 5.Research Organization of Information and Systems Joint Support-Center for Data Science Research)

Keywords:OH airglow, aurora, mesopause, lower thermosphere

We have conducted OH airglow spectra observation at Syowa Station, Antarctic during the winter season (from the end of Feb. to the middle of Oct. in each year) from 2008 to 2019 by using an OH spectrometer. For optical observations from the ground, it is important to precisely know the temporal and spatial distribution of clouds to judge the data quality. To check the sky condition at the observation time, we analyzed image data taken by color digital cameras for aurora activity collocated at Syowa Station. In ground-based image observations, the elevation and azimuth angles of the field of view (FOV) are fixed. Based on the information for the observation situation (latitude, longitude, and observation time), the positions of stars in the FOV can be estimated from the star chart (star positions in an equatorial coordinate system). Then, it is possible to judge the presence or absence of clouds from night sky images, by checking the presence of star images in the predicted positions. Based on the sky condition judgment, we analyzed the OH airglow spectral data only under the clear sky condition, and we detected variations of OH airglow intensity with various timescales. In this study, we focused on the enhancement of the OH airglow intensity that occurred during a few hours and did not seem to be caused by atmospheric gravity waves. We also focused on the enhanced events that continued for a few days. The intensity of OH airglow highly depends on dynamics and photochemical reactions involving minor species in the upper mesosphere region. In particular, we used the cosmic noise absorption (CNA) observation data at Syowa Station to investigate the variation of atmospheric composition in the upper mesosphere by energetic particle precipitation (EPP). The change of the vertical profile of [O] in the upper mesosphere can cause the fluctuation of OH airglow intensity. The [CO] is a good proxy of the vertical transport in the middle atmosphere. We verified [CO] data obtained by Aura/MLS to infer the enhancement of vertical transportation. In this presentation, we show the fluctuation of OH airglow intensity for 12 years at Syowa Station and the results of the EPP events and the enhanced vertical transportation events detected from CNA and [CO] data, respectively. We discuss the relationship between the enhancements of OH airglow and the change of [O] in the upper mesosphere.