The vibrational distribution of N₂⁺ in the terrestrial ionosphere

The densities and vibrational distributions of N 2 + in the X ²Σ g + , A ²Π u , and B ²Σ u + states in the daytime terrestrial ionosphere are computed for both low and high solar activity. Altitude profiles of the relative populations of the vibrational levels of N 2 + X ²Σ g + are presented. The fraction of vibrationally excited N 2 + varies from 5% at 100 km to 50% at 450 km. Several models are examined in which loss of N 2 + (υ) is enhanced for υ > 0 and in which various assumptions are made about the vibrational distributions produced in charge transfer reactions. The N 2 + densities are significantly reduced if N 2 + (υ) reacts with O at rates which are near gas‐kinetic. Vibrational distributions of the A ²Π u and B ²Σ u + states are also presented, as well as volume emission rates and integrated overhead intensities of the major bands of the Meinel and first negative systems.