The effects of consistent chemical kinetics calculations on the pressure-temperature profiles and emission spectra of hot Jupiters
The effects of consistent chemical kinetics calculations on the pressure-temperature profiles and emission spectra of hot Jupiters
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DOI：
10.1051/0004-6361/201628799
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发表时间：
2016-10-01
影响因子：
6.5
通讯作者：
Goyal, J.
中科院分区：
文献类型：
--
作者：
Drummond, B.;Tremblin, P.;Goyal, J.
在这项工作中，我们研究了计算非平衡化学丰度与温度结构一致对高辐照、近距离气体巨型系外行星大气的影响。化学动力学模型在文献中被广泛应用于研究热木星大气的化学成分，这些化学成分预计会通过垂直混合和光化学等过程被赶离化学平衡。到目前为止，所有这些模型都使用压力温度（P-T）曲线作为固定模型输入。这导致了化学与大气的辐射和热性质的分离，尽管事实上在自然界中它们是错综复杂地联系在一起的。我们使用一维辐射-对流平衡模型ATMO，其中包括一个复杂的化学方案来计算P-T剖面，该剖面与非平衡化学丰度完全一致，包括垂直混合和光化学。我们的主要结论是，在强化学不平衡的情况下，与假设化学平衡的P-T分布相比，一致的计算可以导致高达100 K的P-T分布差异。这种温度变化反过来会对化学丰度本身以及模拟的发射光谱产生重要影响。特别是，我们发现持续进行化学动力学计算可以减少非平衡化学对热木星可观测发射光谱的总体影响。因此，来自不一致模型的模拟观测可能产生错误的解释。我们表明，这种行为是由于不一致的模型违反了大气的能量收支平衡。
In this work we investigate the impact of calculating non-equilibrium chemical abundances consistently with the temperature structure for the atmospheres of highly-irradiated, close-in gas giant exoplanets. Chemical kinetics models have been widely used in the literature to investigate the chemical compositions of hot Jupiter atmospheres which are expected to be driven away from chemical equilibrium via processes such as vertical mixing and photochemistry. All of these models have so far used pressure temperature (P-T) profiles as fixed model input. This results in a decoupling of the chemistry from the radiative and thermal properties of the atmosphere, despite the fact that in nature they are intricately linked. We use a one-dimensional radiative-convective equilibrium model, ATMO, which includes a sophisticated chemistry scheme to calculate P-T profiles which are fully consistent with non-equilibrium chemical abundances, including vertical mixing and photochemistry. Our primary conclusion is that, in cases of strong chemical disequilibrium, consistent calculations can lead to differences in the P-T profile of up to 100 K compared to the P-T profile derived assuming chemical equilibrium. This temperature change can, in turn, have important consequences for the chemical abundances themselves as well as for the simulated emission spectra. In particular, we find that performing the chemical kinetics calculation consistently can reduce the overall impact of non-equilibrium chemistry on the observable emission spectrum of hot Jupiters. Simulated observations derived from non-consistent models could thus yield the wrong interpretation. We show that this behaviour is due to the non-consistent models violating the energy budget balance of the atmosphere.