Recently atomic nitrogen densities of ∼106cm−3were measured at 400 km by the open source mass spectrometer on the Atmosphere Explorer‐C satellite (AE‐C). Daytime N densities ∼5 × 107cm−3at 160 km have also been inferred from airglow and other measurements on AE‐C. We show that atomic nitrogen densities of this magnitude result in significantly lower values for the O2+concentration than those measured on AE‐C over the altitude range to 160 to 200 km, because of the removal process O2++ N k3→ NO++ O. We show that the discrepancy can be explained in terms of latitudinal variations in both the N and O2densities. We also present evidence which indicates that k3could be as low as 1 × 10−10cm−3at i