Abstract Electron degradation serves as a significant energy source in planetary upper atmospheres. In this study, a Monte Carlo model is constructed to investigate the degradation of electrons in a pure O 2 atmosphere under the local approximation. Both elastic and inelastic collision processes between electrons and O 2 molecules are considered in the model. The yield spectra, characterizing the occurrence of various inelastic collisions for a specified pair of incident and post-collision energies, are obtained from the model. When combined with the information of e-O 2 collision cross sections, the yields of each inelastic process are then determined. Furthermore, we derive the mean energy per ion pair and the efficiencies of various inelastic processes, along with the yields of secondary (and higher-order) electrons. The calculations presented here are beneficial for understanding the ionization and heating budgets in planetary atmospheres containing a significant amount of O 2 such as Earth and Jovian icy satellites (Europa, Ganymede, and Callisto).

Monte Carlo Calculation of Electron Energy Degradation in a Pure O2 Atmosphere