Non thermal nitrogen atoms in the Earth's thermosphere. 2. A source of nitric oxide

The role of the non maxwellian nitrogen atoms in the odd nitrogen thermospheric chemistry is investigated with a numerical model. This one-dimensional model solves the continuity equation, including molecular and turbulent transport for the coupled NO-N([SUP]4[/SUP]S) system. It is shown that the very fast reaction between hot N([SUP]4[/SUP]S) atoms and O[SUB]2[/SUB] provides an additional source of nitric oxide. At equatorial latitudes, this contribution amounts to 6-30% of the other classical production sources of NO for solar minimum activity conditions. The cross section for elastic collisions with ambient gas introduces the largest uncertainty on this estimate. It is concluded that, although it does not drastically alter the conclusions of previous models of NO, the effect of hot N atoms must be considered in future models of the NO-N system chemistry.