Chemical Activity of Low Altitude (50 km) Sprite Streamers

A three‐stage simulation is used to explore the chemical influence of low altitude (50 km) sprite streamers on the atmosphere, including the chemical trail after the streamer has faded away. In the first stage (streamer phase) a 2D electrodynamical streamer model quantifies the generation of NOx and N2O, and the removal of ozone (O3) by a downward propagating streamer during Δtstreamer = 80 μs. This streamer propagation leads to a distinctive region in the streamer channel, the glow, where the electric field is enhanced. In the second stage (glow phase), the computed densities of the first stage are used as initial conditions for a 0D model to study the chemical evolution of the streamer channel, where we assume a remanent field of 100 Td for the glow and 0 Td elsewhere. This stage lasts Δtglow = 85 μs, the typical glow lifetime at 50 km. Finally, in the third stage (post‐streamer phase), we use the same 0D model, switch off the field in the glow region and let the whole streamer wake evolve roughly 100 s (100 s − Δtglow). Results show a key species such as O3 is mainly depleted during the streamer phase while NOx and N2O are predominantly produced during the same phase. We also compute the local increase of NO2 by sprite streamers at ∼50 km and find out that it could account for the measurable NO2 anomaly over thunderstorms reported from satellite‐based measurements. Plain Language Summary Sprites are high‐altitude electric discharges that occur above thunderstorms and span tens of kilometers vertically and hundreds of meters horizontally. They are made of hundreds of fast‐propagating plasma filaments known as streamers. These streamers propagate due to an enhanced electric field at its tip that ionizes the air ahead, leaving behind a chemical trail in the atmosphere. In this work, we focus on the production/removal of prominent greenhouse gases such as N2O or O3 as well as nitrogen oxides accounting for the measurable impact of sprites on the low‐mesosphere chemistry as reported by satellite‐based measurements. Key Points A three‐stage approach is proposed to explore the chemical impact of sprite streamers at 50 km The main mechanism leading to N2O is associative detachment during the streamer phase and N + NO2 − >N2O + O in the long post‐streamer phase The local increase of NO2 due to sprite streamers at ∼50 km could account for the measurable chemical perturbation of NO2 over thunderstorms