Production of odd nitrogen in the stratosphere and mesosphere: An intercomparison of source strengths

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Abstract
This study intercompares several sources of odd nitrogen (ON) in the stratosphere and mesosphere (middle atmosphere) so as to place galactic cosmic rays (GCRs), nuclear explosions, lightning, solar proton events (SPEs), relativistic electron precipitation, meteors, and the downward diffusion of NO from the thermosphere in their proper context relative to the oxidation of nitrous oxide. Use of published measurements of O3 and N2O show that the source of ON owing to the reaction of O(1D) + N2O peaks between 25 and 35 km and is by far the largest source in an annually, globally averaged sense with a magnitude of 4.5×1034 molecules yr−1. At solar minimum the GCRs add about the same amount of ON as N2O oxidation (1.7×1033 molecules yr−1) for geographic latitudes greater than 50°. Nuclear explosions in 1961 and 1962 added 1.1 and 2.2×1034 NO molecules, respectively, to the total global ON content. SPEs produced more ON at latitudes above 50° than did N2O oxidation for the years 1958, 1959, 1960, and 1972. Analysis of available measurements shows the downward flux of NO from the thermosphere to be between 8 and 33% of the integrated N2O source. Large variations in measurements of ON should be expected at geographic latitudes above 50° where the highly variable SPE source of ON is substantial. Because of the long lifetime of ON in the middle atmosphere, significant variations in its content may also be expected to occur at mid‐latitudes.