Dynamics of the CO+ coma of comet 29P/Schwasmann–Wachmann 1

Abstract Comet-centaur 29P/Schwassmann–Wachmann 1 was observed in CO+ emission and continuum during 2007–2009 using the 6-m Big Telescope Alt-azimuth at the Special Astrophysical Observatory of the Russian Academy of Sciences. We analysed the morphology of the CO+ and dust coma. The distributions of dust and CO+ ions in the coma are not similar and vary depending on the level of comet activity. CO+ ions are more concentrated towards the nucleus than the dust continuum. The column density of the CO+ was derived and found to vary from 3.7 × 109 to 4.3 × 1010 ions cm–2. The production rate of CO+ was estimated to be from (7.01 ± 2.7) × 1024 to (1.15 ± 0.5) × 1026 ions s–1. We discuss possible mechanisms for the ionization of cometary material and show that impact ionization by solar wind particles is probably the main ionization mechanism at large heliocentric distances.