Middle and upper thermospheric odd nitrogen: 1. A new analysis of rocket data

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We evaluate the NRLMSISE‐00 model for calculations of odd nitrogen (NO, N(4S)) in the middle to upper thermosphere (z = 140–250 km). NRLMSISE‐00 incorporates new data on O2 that improves the agreement between odd nitrogen models and data significantly. In particular, the photochemical calculation that uses NRLMSISE‐00 predicts a NO solar cycle variation that is significantly less than previous calculations and that agrees well with the NO observations. This agreement is consistent with the inference from FUV solar occultation data that the O2 abundance above 140 km varies weakly with solar activity and that the O2 vertical profile at solar maximum is sensitive to other factors besides molecular diffusion. Residual discrepancies remain with the comparison of calculated to observed N(4S), which may be due to a combination of theoretical deficiencies and uncertainties in the observations.