Relaxation to photochemical equilibrium of charged species within displaced air parcels in the D-region
The effects of the relaxation to photochemical equilibrium are investigated for the electrons and NO(+) ions in the upper D-region and for the electrons and several species of positive and negative ions present in the lower D-region. In the upper D-region the photochemical model includes electrons, nitric oxide, and NO(+). A self-consisting model of the equilibrium concentrations is developed for the lower D-region, which includes electrons, nitric oxide, O2(-), heavy negative and positive ions, and the oxygen species O, O3, and O2(1 delta g). At altitudes of 75 and 80 km the time dependence of the oxygen species has a significant effect on the equilibration of the electron and O2(-) concentrations. The relaxation to photochemical equilibrium proceeds by five e-folding time scales in the lower D-region, where the time required for final equilibration due to recombination is very long.