Radial Distribution of Production Rates, Loss Rates and Densities Corresponding to Ion Masses <=40 amu in the Inner Coma of Comet Halley: Composition and Chemistry

Abstract

In this paper we have studied the chemistry of C, H, N, O, and S compounds corresponding to ions of masses <=40 amu in the inner coma of the comet 1P/Halley. The production rates, loss rates, and ion mass densities are calculated using the Analytical Yield Spectrum approach and solving coupled continuity equation controlled by the steady state photochemical equilibrium condition. The primary ionization sources in the model are solar EUV photons, photoelectrons, and auroral electrons of the solar wind origin. The chemical model couples ion-neutral, electron-neutral, photon-neutral and electron-ion reactions among ions, neutrals, electrons, and photons through over 600 chemical reactions. Of the 46 ions considered in the model the chemistry of 24 important ions are discussed in this paper. The calculated ion mass densities are compared with the Giotto Ion Mass Spectrometer (IMS) and Neutral Mass Spectrometer (NMS) data at radial distances 1500, 3500, and 6000 km.