Solar cycle modulation of nighttime ozone near the mesopause as observed by MLS

Solar 11-year cycle variations of nighttime ozone near the secondary ozone maximum layer are analyzed with Aura Microwave Limb Sounder (MLS) observations since 2004 that covers complete solar cycle 24. Produced primarily from the recombination of molecular oxygen (O₂) with single oxygen (O) transported from the lower thermosphere, the mesospheric nighttime ozone concentration is proportional to single oxygen density [O], of which the latter is modulated by UV solar cycle variations. MLS nighttime ozone and Solar Radiation and Climate Experiment (SORCE) Solar-Stellar Irradiance Comparison Experiment (SOLSTICE) measured UV show a positive correlation in-phase with the solar cycle. The nighttime ozone correlates strongly with temperature but not monotonously positive nor negative. The slope and sign of the correlation depend on location and season. They are positively correlated in general except for the boreal winter high latitudes.  Because the nighttime [O₃] depends strongly on [O] in the upper mesosphere, it is expected the nighttime [O₃] would follow the [O] distributions, producing similar diurnal, seasonal, and solar-cycle variations, as well as latitudinal distributions as observed in Carbon Monoxide (CO) in the upper mesosphere.