ANALYSIS OF THE SWINGS EFFECT AND GREENSTEIN EFFECT IN COMET P/HALLEY

Spectra have been obtained of Comet P/Halley using the Image Photon Counting System (IPCS) on the Anglo-Australian Telescope in 1986 April. The CN (0, 0) violet system is analyzed to demonstrate the Swings resonance-fluorescence mechanism and multiple spectral images are used in an attempt to create a velocity map of the CN gas throughout the coma by application of the Greenstein effect. The theoretical calculations of the Swings effect are found to be in good agreement with the observed intensities of the R-branch lines of Comet P/Halley. This validates the assertion of an optically thin coma. In addition, 13 lines interspersed throughout the R-branch are identified as lines belonging to the (CN)-C-12 (1,1) band and the (CN)-C-13 (0, 0) band. The (CN)-C-13 (0, 0) isotope R(7) and R(8) lines are used to obtain the C-12/C-13 ratio in the comet. A value of 89 +/- 17 is found in agreement with the solar value. The Greenstein effect is seen observationally and velocity profiles through the coma are obtained by modeling the R(9)/R(12) ratio of the CN (0, 0) band. Changes in radial velocity as large as 1. 57 km s-1 are found to exist within spatial distances of 4500 km. Theoretical models show that gas jets emanating from the rotating nucleus can severely affect the observed Greenstein effect.