The variability of 558 nm OI nightglow intensity measured over Adelaide, Australia

Copyright © 2007 Published by Elsevier Ltd.The intensity of the OI 558 nm nightglow emission from heights near 97 km has been routinely measured since 1995 at Buckland Park (34.9°S, 138.6°E) near Adelaide, Australia. The intensity exhibits spring and autumn enhancements, bright nights and clear seasonal and inter-annual periodicities. Like many other mid-latitude observations, the autumn enhancement is greater than the spring enhancement. A Lomb periodogram analysis of the intensity indicates the presence of annual, semi-annual, and quasi-biennial oscillations. The annual and semi-annual oscillations have about equal intensity at this latitude, with amplitudes of between 17(±5)% and 14(±5)% of the mean intensity, respectively. This is consistent with Adelaide being a transitional latitude between a dominant semi-annual oscillation observed at low latitudes and the dominant annual oscillation observed at mid-latitudes. The annual oscillation is observed to peak in summer while the semi-annual oscillation takes maximum values near equinox. The quasi-biennial oscillation has a smaller amplitude at about 5(±1)% of the mean intensity and takes a maximum value near the autumnal equinox. There is evidence of a solar cycle dependence of the intensity, with nightglow intensity tracking the solar cycle. A harmonic fit to this period yields an amplitude of about 20(±15)% of the mean intensity, but naturally, this result needs to be treated with some caution, as there is only about one period present.http://www.elsevier.com/wps/find/journaldescription.cws_home/644/description#descriptio