Fabry-Perot observations of Comet Halley H₂O⁺

High-resolution spectra of Comet Halley H₂O⁺ emissions, primarily the 6158.64, 6158.85 Å spin doublet, were obtained in 1985 and 1986 using the Wisconsin 150-mm Fabry-Perot scanning spectrometer at the McMath west auxiliary solar telescope on Kitt Peak. On each night of observations, spectra were obtained at several distances in the range of 0 to 2 × 10⁶ km from the comet head along the anti-Sunward direction. The outflow velocities of the cometary plasma were determined from the Doppler shifts of the emissions. The results usually but not always were consistent with constant acceleration of the plasma along the anti-Sunward direction, but the acceleration varied from night to night over a range of about 30-300 cm sec^-2. Unusual kinematics of the plasma on the nights of 14-15 December 1985 and 10 January 1986 could be related to tail disconnection activity reported by other observers.