Sensitivity of a Titan ionospheric model to the ion-molecule reaction parameters

CRITICAL REVIEW OF N, N + , N + 2 , N ++ , And N ++ 2 MAIN PRODUCTION PROCESSES AND REACTIONS OF RELEVANCE TO TITAN'S ATMOSPHERE

“…However, the effect of temperature on the product branching ratios of ion-molecule reactions is much more significant. Surprisingly, Carrasco et al (2008a) showed, in a study of uncertainty propagation in a Titan's ionospheric model, that large uncertainties on branching ratios affect the calculated density of only a few major ions, but they strongly affect many minor ions. Considering the lack of experimental data on such temperature effects, uncertainty management should be an intrinsic component of atmospheric chemistry modeling.…”

“…A series of studies on the photochemical modeling of Titan's atmospheric chemistry has demonstrated that model predictions were affected by large uncertainties, due to both structural uncertainty (incompleteness of the chemical scheme) and parametric uncertainty (limited precision of physico-chemical parameters) (Carrasco et al , 2008a(Carrasco et al , 2008bDobrijevic et al 2008;Hébrard et al 2006Hébrard et al , 2007Hébrard et al , 2009Hébrard et al , 2012Plessis et al 2012). On the structural side, a lot of data are presently missing concerning the reaction rates (1) of heavier species (neutrals and ions) and the associated products (2) of excited states of primary species, (3) of isomers, and (4) of negative ions.…”

The Role of Nitrogen in Titan’s Upper Atmospheric Hydrocarbon Chemistry Over the Solar Cycle

“…At the same time, photochemical modeling is key for gaining insight into the steps of chemistry through which flux effects may cascade down from the parent species to more complex photochemical products. Unfortunately, the sometimes poorly known input parameters used and/or chemistry employed could heavily influence the resulting production, loss, and abundance profiles of photochemical species (e.g., Carrasco et al , 2008Hébrard et al 2007Hébrard et al , 2009Dobrijevic et al 2008;Plessis et al 2010Plessis et al , 2015Gans et al 2013). For instance, the efficiency of N 2 photoabsorption strongly influences the photodissociation of N 2 (Liang et al 2007), as well as CH 4 , which in turn affects the primary photodissociation and photoionization products Mandt et al 2012).…”

Dissociative recombination exalts molecular growth in N2/CH4plasmas

“…The model implements the ion chemistry database established by Carrasco et al [24] and Plessis et al [11], involving C, H and N. Oxygen chemistry has been excluded because it does not play a significant role in APSIS photochemistry [19].…”

“…The rate parameters of these processes are all uncertain (some of them unknown). They are represented by random variables with prescribed distributions, following Hébrard et al [21,22], Carrasco et al [24] and Plessis et al [11].…”