SPATIAL-DISTRIBUTION OF NEUTRAL AND IONIC CONSTITUENTS IN COMET P HALLEY/

Multislit spectra of comet P/Halley were obtained on April 10, 1986, u sing a focal reducer with a field of approximate to 0.5 degrees angula r diameter. The number and arrangement of the slits allowed a reconstr uction of the spatial distribution of principal neutral and ionic coma constituents within a frame of about 4 10(5) x 4 10(5) km(2) at the c omet. Radial profiles and two-dimensional maps for the dust continuum. CN, C-3, CH, CO+, and especially CO2+, are presented in absolute inte nsity and column density units, respectively. Scale lengths and produc tion rates for the radicals were determined within the Haser model. Th e molecular ions are not only restricted to the plasma tail but are al so present in the sunward coma. Instead of forming a peak at the nucle us like the neutral radicals the ion column densities decrease rapidly in the solar direction and form a plateau extending from the nucleus into the antisolar direction. The distribution of CO2+ shows a stronge r decrease in the tailward direction than that of CO+.