Auroral NO concentrations?

Auroral NO chemistry is studied to determine the limits on [NO] and its production rate in steady auroral arcs. We conclude conservatively that the NO concentration cannot exceed 0.1[O2]. The precise value of this upper limit depends very sensitively on the relative yields of N(²D) and N(4S) in the reactions that are the major auroral sources of N atoms, and on the basis of the requirements of mid-latitude models for odd nitrogen, a value of 0.03[O2] is estimated. Plausible auroral [NO] enhancements are of the order of (3–6) × 108 cm−3 after 10³ s and (1–4) × 109 cm−3 after 104 for a steady IBC 2+ arc.