A comparison of ground-based CCD H2O(+) observations with the Giotto measurements at Comet Halley

Preliminary results from an analysis of the CCD imaging observations with H₂O⁺ ion filters taken just hours after the Giotto fly-by at comet Halley indicate that secondary peaks in the H₂O⁺ ion density might exist upstream and on the flank sides of the comet. Such structures, if indeed of plasma origin, could be related to the plasma pile-up region as detected by the Ion Mass spectrometer and Neutral Mass Spectrometer experiments on Giotto. Possibility of fast time variability for such plasma structures may also exist.