Mesospheric energy loss rates by OH and O₂ emissions at 23^°S

The nightglow OH(9, 4) and O2 atmospheric (0,1) band emission intensities and their rotational temperatures T(OH) and T(O2), respectively, observed at Cachoeira Paulista (23°S, 45°W), Brazil, during the period from October 1989 to December 1990, have been analyzed to study the nighttime mesospheric energy loss rates through the radiations from the vibrationally excited OH* and electronically excited O2* bands. The total emission rates of the OH Meinel bands, O2 atmospheric (0,0) and O2 infrared atmospheric (1Δg) bands were calculated using reported data for the relative band intensities I(ν'',ν')/I(9,4), IO2A(0,0)/IO2A(0,1) and IO2(1Δg)/IO2A(0,1). It was found that there is a minimum in equivalent energy loss rate by the OH* Meinel bands during December/January (equivalent energy loss rate of 0.39K/day*, where day* means averaged over the night) and maximum in equivalent energy loss rate during September (equivalent energy loss rate of 0.98K/day*). Energy loss rate by the O2* radiation, on the other hand, is weaker than that by the OH* Meinel bands, showing equivalent energy loss rates of 0.12K/day* and 0.22K/day* during January and September, respectively