On the rate coefficient of the N(2D)+O2→NO+O reaction in the terrestrial thermosphere

Abstract

The temperature dependence of the rate coefficient of the N(2D)+O2→NO+O reaction has been determined using ab initio potential energy surfaces (PES) and classical dynamics. The calculation agrees with the recommended rate coefficient at 300 K (∼110 km altitude). The rate coefficient is given by the expression k(T) = 6.2 × 10−12(T/300) cm3/s/molec. In contrast to the nearly temperature‐independent value of this rate coefficient previously recommended, the value given here increases by almost a factor of about four as the altitude increases from 110 to 200 km. It is also shown that even though N(2D) atoms in the thermosphere are produced with large translational energies, using the value of the rate coefficient at the local temperature introduces negligible error in the amount of NO produced. The new value of this rate coefficient will significantly increase the amount of NO computed in the aeronomic models causing a re‐evaluation of the heat budget and temperature and density structure of the thermosphere. In particular, implications of the larger rate coefficient for the recent observations of dramatically enhanced 5.3 μm emission from NO in the thermosphere due to solar storms are discussed.