Airglow from the inner comas of comets

The intensities of radiation from the inner comas of comets which are composed primarily of water and carbon monoxide have been calculated. Only 'airglow' emissions initiated by the absorption of EUV radiation have been considered. The photoionizations of H2O, CO, CO2, and N2 are the most important emission sources, although photoelectron excitation is also considered. Among the emission features for which intensities were calculated are H2O(+), CO(+) (first negative), CO (fourth positive), CO (Cameron), CO2(+), N2 (Vegard-Kaplan), N2(+) (first negative), and O I (1304 A). In the inner coma (collision region) these airglow mechanisms are shown to be possible competitors with the usually assumed resonance-scattering and fluorescence-excitation mechanisms appropriate for the outer coma and tail.