On the production of positive molecular ions in cometary comas

Abstract

Positively charged molecular ions, such as H2O+, which have been observed in cometary. comas, may be efficiently produced by the evaporation of positively charged clathrate grains of radii in the range ∼10−6–10−5 cm. Such grains may be expelled from nuclei of comets, along with gaseous molecules. Grain charging occurs via interaction with solar ultraviolet photons and/or solar wind protons. Observational data on the total quantities as well as the distributions of H2O and H2O+ in cometary comas are shown to be in accord with detailed model calculations.