摘要
The present study describes the long-term changes in Pre-midnight and Midnight airglow intensities of 557.7 nm during the period 1979-1994 over mid latitude Japanese station i.e., Kiso, Tokyo Astronomical Observatory, University of Tokyo (35.79oN, 137.63oE;1130 m), Japan. It has observed that there is a positive increasing decadal change in Midnight and Pre-midnight mesospheric airglow intensity of the range 25 - 88 R. This range is the order of 10 to 30% of the observed MARV and average night airglow intensity of 250 R. Besides this long-term trend, inter-annual monthly variation is also seen from fluctuation of yearly variation of deviation values from MARV to particular average monthly values. The present observations about the positive decadal change in night time mesospheric airglow intensity has been further linked to the reduction of mesospheric electron densities and temperature or shrinking and cooling of the lower ionosphere as established from the long-term behavior of mesospheric parameters such as a negative decadal change in thermal structure, electron density, neutral density parameters as per studies reported by other researchers.
The present study describes the long-term changes in Pre-midnight and Midnight airglow intensities of 557.7 nm during the period 1979-1994 over mid latitude Japanese station i.e., Kiso, Tokyo Astronomical Observatory, University of Tokyo (35.79oN, 137.63oE;1130 m), Japan. It has observed that there is a positive increasing decadal change in Midnight and Pre-midnight mesospheric airglow intensity of the range 25 - 88 R. This range is the order of 10 to 30% of the observed MARV and average night airglow intensity of 250 R. Besides this long-term trend, inter-annual monthly variation is also seen from fluctuation of yearly variation of deviation values from MARV to particular average monthly values. The present observations about the positive decadal change in night time mesospheric airglow intensity has been further linked to the reduction of mesospheric electron densities and temperature or shrinking and cooling of the lower ionosphere as established from the long-term behavior of mesospheric parameters such as a negative decadal change in thermal structure, electron density, neutral density parameters as per studies reported by other researchers.
