A factor of 2 reduction in theoretical F2 peak electron density due to enhanced vibrational excitation of N₂ in summer at solar maximum

We have investigated the degree to which the O + + N 2 reaction rate is increased as a result of enhanced vibrational excitation of the N 2 molecule in the thermosphere. We find that the reaction rate may be sufficiently elevated in summer at solar maximum to decrease the peak O + density by a factor of 2, but there is only a small reduction in the winter peak density. Therefore the vibrational excitation of N 2 acts to increase the magnitude of the seasonal anomaly. This work emphasizes the need for more laboratory work to clear up uncertainties in some of the key parameters. Uncertainties in the calculations arise from the lack of measurements of the key loss rates for O + to O 2 and N 2 at the temperatures encountered at solar maximum, and also to uncertainties in the cross sections for excitation and de‐excitation of N 2 vibrational quanta by electrons.