1D-coupled photochemical model of neutrals, cations and anions in the atmosphere of Titan
1D-coupled photochemical model of neutrals, cations and anions in the atmosphere of Titan
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DOI：
10.1016/j.icarus.2015.12.045
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发表时间：
2016-04-01
期刊：
影响因子：
3.2
通讯作者：
Gronoff, G.
中科院分区：
文献类型：
--
作者：
Dobrijevic, M.;Loison, J. C.;Gronoff, G.
到目前为止，已经发表了许多具有不同特征的模型来研究土卫六大气中的化学过程。有些模型只考虑平流层中的中性粒子或电离层中的离子粒子，而很少考虑整个大气中所有粒子的耦合。其中很少有人强调化学方案中不确定性的重要性，并研究其在模型中的传播。我们已经开发了一个新的泰坦大气的一维光化学模型，将中性物质与从低层大气到电离层的正离子和负离子耦合，并将我们的结果与观测结果进行了比较，以全面了解驱动泰坦平流层和电离层组成的化学过程。正离子和负离子化学，并通过引入高分辨率N2吸收截面改进了对N2光解离的描述。我们首次在完全耦合的离子-中性模型中进行了不确定性传播研究，确定了中性和离子反应速率常数的不确定性如何影响模型结果，并确定了导致这种行为的关键反应。我们发现我们的模型结果和观测结果在平流层和电离层的大多数中性化合物之间非常好的协议。我们的研究结果也与平均INMS质谱和特定的飞掠在白昼表明，我们的化学模型（中性和离子）提供了一个很好的近似土卫六的大气化学作为一个整体。我们的不确定性传播研究突出了解释质量14，31，41的INMS质谱的困难，我们确定了负责这些模糊性的关键反应。尽管在化学模型的整体改进，对一些特定的化合物（HC 3 N，C2 H5 CN，C2 H4）的分歧突出了某些物理过程可能发挥的作用（质子动力学或粘附在气溶胶上）。我们发现，一些关键的关键反应是重要的许多化合物，包括中性和离子，应优先研究，以降低剩余的模型的不确定性。需要对一些特定过程（包括光解）进行广泛的研究。(C)2016由Elsevier Inc.出版
Many models with different characteristics have been published so far to study the chemical processes at work in Titan's atmosphere. Some models focus on neutral species in the stratosphere or ionic species in the ionosphere, but few of them couple all the species throughout the whole atmosphere. Very few of these emphasize the importance of uncertainties in the chemical scheme and study their propagation in the model. We have developed a new 1D-photochemical model of Titan's atmosphere coupling neutral species with positive and negative ions from the lower atmosphere up to the ionosphere and have compared our results with observations to have a comprehensive view of the chemical processes driving the composition of the stratosphere and ionosphere of Titan.We have updated the neutral, positive ion and negative ion chemistry and have improved the description of N-2 photodissociation by introducing high resolution N2 absorption cross sections. We performed for the first time an uncertainty propagation study in a fully coupled ion-neutral model.We determine how uncertainties on rate constants on both neutral and ionic reactions influence the model results and pinpoint the key reactions responsible for this behavior. We find very good agreement between our model results and observations in both the stratosphere and in the ionosphere for most neutral compounds. Our results are also in good agreement with an average INMS mass spectrum and specific flybys in the dayside suggesting that our chemical model (for both neutral and ions) provides a good approximation of Titan's atmospheric chemistry as a whole. Our uncertainty propagation study highlights the difficulty to interpret the INMS mass spectra for masses 14, 31, 41 and we identified the key reactions responsible for these ambiguities.Despite an overall improvement in the chemical model, disagreement for some specific compounds (HC3N, C2H5CN, C2H4) highlights the role that certain physical processes could play (meridional dynamics or sticking on aerosols). We find that some critical key reactions are important for many compounds including both neutrals and ions and should be studied in priority to lower the remaining model uncertainties. Extensive studies for some specific processes (including photolyses) are required. (C) 2016 Published by Elsevier Inc.