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arXiv 1712.07643astro-ph.EPphysics.ao-phphysics.flu-dyn
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作为行星式热机的热行星的大气环流

Atmospheric Circulations of Hot Jupiters as Planetary Heat Engines

Daniel D. B. Koll, Thaddeus D. Komacek

摘要:

由于它们强烈的入射恒星辐射和可能的潮汐锁定自旋状态,预计热彗星的风速接近或超过声速。在这项工作中,我们开发了一个理论来解释这些风的大小。我们的模型热的制冷机作为行星热机,并表明,热制冷机总是低于一个理想的卡诺发动机的效率。接下来,我们证明了我们的预测风速匹配那些从三维数值模拟在广泛的参数范围。最后,我们使用我们的理论来评估如何以及不同的阻力机制可以匹配的风速观测到的多普勒光谱HD 189733 b和HD 209458 b。我们发现,磁阻力可能太弱,无法与HD 189733 b的观测结果相匹配,但与HD 209458 b的观测结果相一致。相反,剪切不稳定性和/或冲击与这两种观测结果是一致的。此外,这两种机制预测了比目前观察到的更热和更冷的行星的不同风速趋势。因此,我们提出,更广泛的多普勒观测可以揭示多种阻力机制在不同的热彗星。

英文摘要:

Because of their intense incident stellar irradiation and likely tidally locked spin states, hot Jupiters are expected to have wind speeds that approach or exceed the speed of sound. In this work we develop a theory to explain the magnitude of these winds. We model hot Jupiters as planetary heat engines and show that hot Jupiters are always less efficient than an ideal Carnot engine. Next, we demonstrate that our predicted wind speeds match those from three-dimensional numerical simulations over a broad range of parameters. Finally, we use our theory to evaluate how well different drag mechanisms can match the wind speeds observed with Doppler spectroscopy for HD 189733b and HD 209458b. We find that magnetic drag is potentially too weak to match the observations for HD 189733b, but is compatible with the observations for HD 209458b. In contrast, shear instabilities and/or shocks are compatible with both observations. Furthermore, the two mechanisms predict different wind speed trends for hotter and colder planets than currently observed. As a result, we propose that a wider range of Doppler observations could reveal multiple drag mechanisms at play across different hot Jupiters.

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