Chemistry of sprite discharges through ion-neutral reactions

[摘要] We estimate the concentration changes, caused bystreamerdischarge in sprites, of ozone and related minor species as oddnitrogen (NO_x) and hydrogen (HO_x) families in the upper stratosphere andmesosphere. The streamer has an intense electric field and high electrondensity at its head, where a large number of chemically-radical ions and atomsare produced through electron impact on neutral molecules. After itspropagation, densities of minor species can be perturbed through ion-neutralchemical reactions initiated by the relaxation of these radical products. Weevaluate the production rates of ions and atoms using an electron kinetics modeland by assuming that the electric field and electron density are in the head region. Wecalculate the density variations mainly for NO_x, O_x, and HO_x species usinga one-dimensional model of the neutral and ion composition of the middleatmosphere, including the effect of the sprite streamer. Results at thenighttime condition show that the densities of NO, O₃, H, and OH increasesuddenly through reactions triggered by the first atomic nitrogen andoxygen product, and electrons just after streamer initiation. It is shown that NO andNO₂ still remain for 1 h by a certain order of increase with theirsource-sink balance, predominantly around 60 km; for other species, increasesin O₃, OH, HO₂, and H₂O₂ still remain in the range of 40–70 km.From this affirmative result of long-time behavior previously not presented,we emphasize that sprites would have the power to impact local chemistry atnight. We also discuss the consistency with previous theoretical andobservational studies, along with future suggestions.

[学科分类] 大气科学