Electron-impact excitation in upper-atmosphere remote sensing

Full text: Electron-impact excitation plays a major role in emission from aurora and a minor role in the dayglow and nightglow. For some molecules, such as nitrogen and nitric oxide, electron-impact excitation can be followed by a radiative cascade through many different sets of energy levels, producing emission spectra with a large number of lines. We are investigating whether parts of this rich spectrum can be exploited for remote sensing of the atmosphere. We report on the ongoing development of a computer program which predicts the emission spectrum for nitrogen and nitric oxide in aurora and the ionosphere. This program includes the necessary atomic and molecular data such as electron-impact cross sections, Franck Condon factors, energy levels, transition probabilities, quenching rates and predissociation rates, as well as atmospheric data. The program performs a statistical equilibrium calculation to predict the spectrum of the radiation resulting from electron-impact excitation. We present sample results from this program and compare them against available measurements. The prospects for remote sensing by measurement of the spectrum of radiation resulting from electron-impact excitation are assessed