Thermo-compositional Diabatic Convection in the Atmospheres of Brown Dwarfs and in Earth’s Atmosphere and Oceans
Thermo-compositional Diabatic Convection in the Atmospheres of Brown Dwarfs and in Earth’s Atmosphere and Oceans
复制标题
褐矮星大气以及地球大气和海洋中的热成分非绝热对流
DOI：
10.3847/1538-4357/ab05db
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
M. Stauffert
中科院分区：
文献类型：
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作者：
P. Tremblin;T. Padioleau;M. Phillips;G. Chabrier;I. Baraffe;S. Fromang;E. Audit;H. Bloch;A. Burgasser;B. Drummond;M. González;P. Kestener;S. Kokh;P. Lagage;M. Stauffert
通过将对流理论推广到任何类型的热和成分源项（非绝热过程），我们表明，地球海洋中的热盐对流，恒星大气中的指状对流和地球大气中的湿对流都来自相同的一般非绝热对流不稳定性。我们还表明，“辐射对流”所引发的CO/CH 4过渡与辐射传输的大气中的褐矮星是类似的潮湿和热盐对流。我们推导出一个广义的混合长度理论，包括在一维码的源项的效果。我们发现，CO/CH 4的“辐射”对流可以显着降低的温度梯度在大气中的棕矮星类似于地球大气中的潮湿对流，从而可能解释红褐矮星光谱。通过使用理想化的二维流体动力学模拟在勒杜不稳定制度，我们表明，成分源项确实可以引起温度梯度的降低。L/T转变可以通过绝热和非绝热对流传输之间的分歧来解释，并被视为巨大的冷却危机：液体/蒸汽-水对流中沸腾危机的模拟。这种机制，以及其他化学转变，可能存在于许多巨大的和类似地球的系外行星中。研究不同参数（有效温度、成分变化）对CO/CH 4辐射对流的影响以及与地球湿对流和热盐对流的类比，为利用褐矮星更好地了解我们地球气候中起作用的物理学的某些方面提供了可能性。
By generalizing the theory of convection to any type of thermal and compositional source terms (diabatic processes), we show that thermohaline convection in Earth’s oceans, fingering convection in stellar atmospheres, and moist convection in Earth’s atmosphere are derived from the same general diabatic convective instability. We also show that “radiative convection” triggered by the CO/CH4 transition with radiative transfer in the atmospheres of brown dwarfs is analogous to moist and thermohaline convection. We derive a generalization of the mixing-length theory to include the effect of source terms in 1D codes. We show that CO/CH4 “radiative” convection could significantly reduce the temperature gradient in the atmospheres of brown dwarfs similarly to moist convection in Earth’s atmosphere, thus possibly explaining the reddening in brown dwarf spectra. By using idealized 2D hydrodynamic simulations in the Ledoux unstable regime, we show that compositional source terms can indeed provoke a reduction of the temperature gradient. The L/T transition could be explained by a bifurcation between the adiabatic and diabatic convective transports and seen as a giant cooling crisis: an analog of the boiling crisis in liquid/steam-water convective flows. This mechanism, with other chemical transitions, could be present in many giant and Earth-like exoplanets. The study of the impact of different parameters (effective temperature, compositional changes) on CO/CH4 radiative convection and the analogy with Earth moist and thermohaline convection is opening the possibility of using brown dwarfs to better understand some aspects of the physics at play in the climate of our own planet.