Weighted average of the two strongest CO⁺ N = 2 − 1 lines observed in C/2016 R2 (PanSTARRS) on 24.8 January 2018. Each line has been divided by its statistical weight (9/15 and 5/15 for the F = 5∕2 − 3∕2 and F = 3∕2 − 1∕2 transitions, respectively) before averaging. Scales are as in Fig. 3. The line shows a narrow peak close to the zero velocity and a broader component mostly red-shifted indicative of antisunward acceleration of CO⁺ ions by the solar wind.