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Earth Planets Space, Vol. 63 (No. 8), pp. 941-948, 2011
doi:10.5047/eps.2011.04.006

Effects of solar cycle variations on oxygen green line emission rate over Kiso, Japan

Uma Das1, C. J. Pan1, and H. S. S. Sinha2

1Institute of Space Science, National Central University, Jhongli—32001, Taiwan
2Physical Research Laboratory, Ahmedabad—380009, India

(Received October 4, 2010; Revised April 12, 2011; Accepted April 19, 2011; Online published December 29, 2011)

Abstract: A sixteen year long dataset of mesospheric OI 557.7 nm green line nightglow emission rate, measured over Kiso (35.79°N, 137.63°E), Japan using ground-based photometers is spectrally investigated using the Hilbert-Huang Transform (HHT). The spectrograms reveal the presence of semi-annual, annual and quasi-biennial oscillations in consonance with the results obtained from wavelet analysis in an earlier study. In addition, due to the use of the HHT, we have been able to investigate the very low frequency solar cycle variation in the emission rate. It is found that there is a significant solar cycle effect on the oxygen green line emission rate. The mean amplitude of variation is approximately 20% and it is also found that it is maximum at midnight. A correlation study between the means of the emission rate and the solar radio flux at 10.7 cm also shows that the effect of solar activity on the oxygen green line emission rate is maximum at midnight.
Key words: Mesosphere, airglow, Hilbert-Huang Transform, solar cycle effects.


Corresponding author E-mail: umadas@jupiter.ss.ncu.edu.tw


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