Ion composition and solar wind interaction: Observations of comet C/1995 O1 (Hale-Bopp)

The extraordinary brightness of comet Hale-Bopp (C/1995 O1) offered the rare opportunity to investigate its ion tail by observations over a wide range of wavelengths. For the first time, ion emission lines could be detected in the radio domain, originating from H₃O⁺, HCO⁺ and CO⁺ ions. Observations in the extreme ultraviolet range showed O⁺ emissions. Optical imaging observations show a spectacular detail of structures in the ion tail. The combined measurements of the ion spatial distribution and dynamic provide a wealth of information which needs to be understood in terms of models of the comet-solar wind interaction and ion-neutral molecule reactions in the coma.