Understanding the Role of Electron-driven Processes in Atmospheric Behaviour

Abstract

Electron-impact excitation plays a major role in emission from aurora and a less significant but nonetheless crucial role in the dayglow and nightglow. For some molecules, such as N 2 , O 2 and NO, electron-impact excitation can be followed by radiative cascade through many different sets of energy levels, producing emission with a large number of lines. We review the application of our statistical equilibrium program to predict this rich spectrum of radiation, and we compare results we have obtained against available independent measurements. In addition, we also review the calculation of energy transfer rates from electrons to N 2 , O 2 and NO in the thermosphere. Energy transfer from electrons to neutral gases and ions is one of the dominant electron cooling processes in the ionosphere, and the role of vibrationally excited N 2 and O 2 in this is particularly significant. The importance of the energy dependence and magnitude of the electron-impact vibrational cross sections in the calculation of these rates is assessed.