Abstract
Abstract. The chemical processes in daytime sprite streamers in the altitude range of 30–54 km are investigated by means of a detailed ion–neutral chemistry model (without consideration of transport). The focus lies on nitrogen, hydrogen and oxygen species, and in particular on ozone perturbations. Initial effects of the breakdown electric fields at the tip of sprite streamers include a short-term loss of ozone due to ion–chemical reactions, a production of nitrogen radicals, and a liberation of atomic oxygen. The latter leads to a formation of ozone. In terms of relative ozone change, this effect decreases with altitude. The model results indicate that the subsequent ozone perturbations due to daytime sprites streamers differ considerably from the ones of night-time events. For night-time conditions, reactive nitrogen produced at the streamer heads is rapidly converted into significantly less reactive NO2, and there is basically no ozone depletion. The situation is different for daytime conditions where NOx causes catalytic ozone destruction. As a consequence, there is significant ozone loss in sprite streamers in the daytime atmosphere, in particular at higher altitudes. At an altitude of 54 km, ozone in the streamer column has decreased by about 15% fifteen minutes after the sprite event.
Highlights
Sprites are transient luminous discharges in the mesosphere occurring above active thunderstorms
Streamers are self-sustaining plasma filaments. Once formed, they can propagate through an under-voltage regime, that is, regions where the ambient electric field is significantly smaller than the breakdown electric field
Corresponding to the first daytime sprite event detected by Stanley et al (2000), the model simulations were performed for latitude 27.5◦ N, 14 August, 16:41 LT, almost two hours before sunset
Summary
Sprites are transient luminous discharges in the mesosphere occurring above active thunderstorms. Hiraki et al (2004) have modelled the production of O(1D) in night-time and daytime sprite halos, and Evtushenko and Mareev (2011) have simulated sprite events for night-time as well as daytime conditions Both of these studies dealt with the diffuse region of sprites but not with streamers which are thought to significantly contribute to the chemical impact of sprites. The present work is devoted to the investigation of chemical effects in the streamer zone of a daytime sprite. For this purpose, an ion–neutral chemistry model has been set up. The model is applied to atmospheric conditions similar to the daytime sprites detected by Stanley et al (2000)
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