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arXiv 1902.00280astro-ph.EP
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类地行星大气潮汐力矩的一般频率依赖性

A generic frequency dependence for the atmospheric tidal torque of terrestrial planets

Pierre Auclair-Desrotour, Jérémy Leconte, Cyril Mergny

摘要:

热大气潮汐对类地行星的自转有很强的影响。它们可以将这些行星锁定在异步旋转的平衡状态。我们的目的是表征潮汐力矩的依赖性,从半日热潮汐潮汐的潮汐频率,行星轨道半径,和大气表面压力。潮汐扭矩计算从全三维模拟的大气气候和平均流量使用通用版本的LMDZ大气环流模式(GCM)的情况下,氮占主导地位的大气。数值结果进行了讨论的帮助下,更新的线性分析框架。功率标度律的演变与行星轨道半径和表面压力的扭矩。潮汐扭矩表现出i)在同步附近的热峰,ii)与高频范围中的兰姆模式的激发相关联的共振峰,以及iii)在这些共振之外的明确定义的频率斜率。我们的线性理论很好地解释了这些特征。无论恒星与行星之间的距离和表面压力如何,扭矩频谱--当用相关的幂律重新标度时--总是呈现出相同的行为。这使我们能够提供一个单一的和易于使用的经验公式描述的大气潮汐扭矩在整个参数空间。有了这样一个公式,大气潮汐扭矩的影响可以在行星旋转动力学的进化模型中以计算效率高且相对准确的方式实现。

英文摘要:

Thermal atmospheric tides have a strong impact on the rotation of terrestrial planets. They can lock these planets into an asynchronous rotation state of equilibrium. We aim at characterizing the dependence of the tidal torque resulting from the semidiurnal thermal tide on the tidal frequency, the planet orbital radius, and the atmospheric surface pressure. The tidal torque is computed from full 3D simulations of the atmospheric climate and mean flows using a generic version of the LMDZ general circulation model (GCM) in the case of a nitrogen-dominated atmosphere. Numerical results are discussed with the help of an updated linear analytical framework. Power scaling laws governing the evolution of the torque with the planet orbital radius and surface pressure are derived. The tidal torque exhibits i) a thermal peak in the vicinity of synchronization, ii) a resonant peak associated with the excitation of the Lamb mode in the high frequency range, and iii) well defined frequency slopes outside these resonances. These features are well explained by our linear theory. Whatever the star-planet distance and surface pressure, the torque frequency spectrum -- when rescaled with the relevant power laws -- always presents the same behaviour. This allows us to provide a single and easily usable empirical formula describing the atmospheric tidal torque over the whole parameter space. With such a formula, the effect of the atmospheric tidal torque can be implemented in evolutionary models of the rotational dynamics of a planet in a computationally efficient, and yet relatively accurate way.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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