Study of the polar mesopause region by remote sensing of OH airglow
The OH Meinel band emissions are the brightest night airglow emissions in the near-infrared regions, and peak at mesopause altitudes. Since the intensity distribution in these vibration-rotation bands is quickly equalized to that determined by the local kinetic temperature, the OH rotational tempera...
| Main Authors: | , , |
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| Format: | Thesis |
| Language: | English |
| Published: |
2010
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| Subjects: | |
| Online Access: | https://ir.soken.ac.jp/?action=repository_uri&item_id=1680 http://id.nii.ac.jp/1013/00001654/ |
| Summary: | The OH Meinel band emissions are the brightest night airglow emissions in the near-infrared regions, and peak at mesopause altitudes. Since the intensity distribution in these vibration-rotation bands is quickly equalized to that determined by the local kinetic temperature, the OH rotational temperature can be derived from the spectrum of OH airglow. This technique has been widely used as a conventional and reliable method of temperature measurement in the mesopause region, especially in the middle- and low-latitude regions. However, it is known to be difficult to apply in the polar regions, because auroral emissions contaminate OH airglow spectra. There are a few examples of OH rotational temperature observations conducted in Antarctic for the purposes of studying the relationship between aurora activity and OH rotational temperature. However, highly energetic auroral electrons can reach altitudes just below the mesopause (～90 km) and can cause heating of the neutral atmosphere at that altitude. There are virtually no previous reports that show a quantitative relationship between auroral precipitations and OH rotational temperature. A fast high-resolution spectrometer designed specifically to observe the spectrum of the OH vibrational-rotational band in the auroral zone has been developed. The OH 8-4 band around the 950-nm wavelength region in the nightglow spectrum was selected as the most suitable vibration-rotation band for observation in polar regions, based on Arctic survey observations. Its suitability lies in the fact that it is less susceptible to contamination from strong auroral emission. The new spectrometer comprises a fast optical system, a transmission grating and a CCD camera. The operating spectral region just encompasses the OH 8-4 band (900-990 nm) and a moderate spectral resolution of 0.27 nm is realized. A back-illuminated CCD with an infrared-enhanced quantum efficiency (QE) is used as the imaging device. The sensitivity and spectral resolution of the spectrometer were calibrated at the ... |
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