Spatial distribution of the airglow observed by the Reimei/MAC limb observations

Airglow is the phenomenon that the particles in the upper atmosphere emit light at night to release their energy excited by the solar radiation. This phenomenon is observed in the region from the mesosphere to the lower thermosphere above the mid-latitude regions. UARS/WINDII had observed airglow emission from 1991 to 1997 and found that there are large structures around the equatorial region. Spatial distributions of the airglow emission have not been clarified sufficiently because there have been few global observations. The objective of this study is to clarify the spatial distributions of the airglow emissions using the Reimei satellite Multi-spectral Auroral Camera(MAC). The data observed in 557.7nm wavelength and 670nm wavelength are used in this study. 557.7nm green line is the main spectrum of O-airglow and 670nm red line corresponds to OH-airglow. The orbit of the Reimei satellite is in 0050-1250LT plane at the 650-km altitude. Orbital period of the Reimei satellite is about 100 minutes. This satellite has observed airglow emission on the limb direction of the Earth in the region between 15N and 40N for three times a day since March 2008. Observational data from March 2008 to August 2009 are used in this study. Vertical profiles of the volume emission rate (VER) of the airglow in the two wavelengths were derived from the observational data. Uniformity of the intensity of the emission at the same altitude was assumed to obtain the vertical profiles of the airglow. The peak of VER of O-airglow observed in the 557.7-nm wavelength was 10km higher than that observed in the 670-nm wavelength in most observations. Wavy structures with 100km wavelength were observed in some events of the airglow emissions. The relations between these wavy structures and atmospheric gravity waves were discussed. Latitude and local time dependences of the intensity of the airglow were also investigated.