NOx production in laboratory discharges simulating blue jets and red sprites

Abstract

Sources of middle atmosphere nitrogen oxides, including transport from the troposphere and production in situ by energetic electrons, are currently not well characterized. Production of nitrogen oxides (NOx) in the middle atmosphere by transient luminous events (TLEs), such as red sprites and blue jets has previously been estimated from satellite observations and modeling studies. This is the first laboratory attempt to estimate NOx production by TLEs, following studies that have confirmed electrical similarities between laboratory discharges and TLEs. A pressure‐controlled chamber and high‐voltage power supplies simulated middle atmosphere discharges. Chemiluminescence NOx analyzers sampled NOx following the completion of the chamber discharges, which was used to calculate total NOx production for each discharge as well as NOx per ampere of current and NOx per Joule of discharge energy. Three different production efficiencies in NOx/J as a function of pressure pointed to three different production regimes: one for tropospheric pressures (100–500 mb), one for stratospheric pressures (1–100 mb), and one for upper stratospheric to mesospheric pressures (no greater than 1 mb). Discharges at jet‐like pressures are measured to produce 1.7 × 1016 to 6.40 × 1017 molecules of NOx per discharge, while discharges at sprite‐like pressure produce 6.97 × 1013 to 8.57 × 1013 molecules of NOx per discharge. Blue jets were calculated to produce 1.7 × 1022 to 7.4 × 1026 molecules of NOx, while red sprites were calculated to produce 6.8 × 1023 to 6.3 × 1027 molecules of NOx. On the basis of global sprite frequency estimates global annual NOx production by sprites is estimated to be between 7 × 1023 and 2 × 1028 molecules per second.