Electron impact excitation of nitric oxide under auroral conditions

Abstract

Excitation of the ground vibrational levels and nine excited electronic states in NO has been simulated for an IBC II aurora. New electron impact excitation cross sections for NO were combined with a measured IBC II auroral secondary electron energy distribution and the electronic‐vibrational populations were determined for conditions of statistical equilibrium. This model predicts an extended vibrational distribution in the NO ground electronic state produced by radiative cascade from the many higher lying doublet excited electronic states. In addition to energy storage in the vibrational population of the ground electronic state, both the a 4Π and L′ ²Φ excited electronic states are predicted to have relatively high number densities in aurora. This extended ground state vibrational distribution is predicted to emit infrared [IR] radiation from 1.3 to 8.2 µm and most IR bands are predicted to be stronger than band emission from any of the electonic transitions.