[hal-00665046] Production of neutral species in Titan's ionosphere through dissociative recombination of ions as measured by INMS

This work aims to quantify the neutrals fluxes produced by ion dissociative recombination processes (DR) in Titan's ionosphere. The calculation is based on the ion densities measured by the INMS instrument on Cassini orbiter during flyby T19 at 1200 km of altitude. The dissociative recombination exhaustive chemical model is taken from Plessis et al. [1]. Neutral fluxes are compared with those predicted by the photochemical model of Hébrard et al. [2]. The comparison shows that the neutral production rates are at least of the same order of magnitude, with neutral fluxes from DR reactions which are often even larger. This first study confirms the necessity to build coupled models for the ionosphere taking into account the respective impacts of ions on the neutrals and of neutrals on the ions budget. Moreover we show that the highly dissociative contribution of the ion-electron recombinations leads to cascade effects on the neutral budget, with significant contribution to neutral species smaller than their parent ion. This important global chemical lysis effect of the DR is missed if implementing a simplified H-loss scheme.



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