Exoplanetology: Exoplanets & Exomoons

Thermal Tides On Rocky Planets Through A Novel Fully Analytical Solution

By Keith Cowing

Status Report

astro-ph.EP

October 22, 2024

Filed under astro-ph.EP, atmosphere, exoplanet, General Circulation Models, habitability, Precambrian, rocky exoplanet, Thermal tides, thermotidal response

Thermal Tides On Rocky Planets Through A Novel Fully Analytical Solution — Maximum reached by the imaginary part of the semidiurnal surface pressure component given by Eq. (2.4) as a function of the atmospheric opacity and radiative cooling frequency. The black solid and dashed lines define, from below, regions where the thermotidal response is sufficient to cancel the gravitational counterpart in the Precambrian (4587−538 Myr) and the late Paleozoic/early Mesozoic (350−250 Myr). The shaded areas indicate the contraints on αA and σ0 derived from observations and GCM simulations, along with the corresponding radiative timescales. The yellow and red arrows indicate the amplification factors needed to reach the Precambrian and Mesozoic/Paleozoic thresholds, respectively. The pink and green dots represent the GCM simulations of Wu et al. (2023), Fig. S4 (W23), and of Deitrick & Goldblatt (2024), Fig. 1 (DG24), respectively. Figure adapted from F24, Fig. 5. — astro-ph.EP

Thermal tides are atmospheric tides caused by variations in day-night insolation, similar to gravitational tides but with key differences.

While both result in delayed mass redistribution, energy dissipation, and angular momentum exchanges between the planet and its host star, thermal tides can drive a planet’s dynamics away from the rotational equilibrium states predicted by classical tidal theory.

In this work, we present a novel closed-form solution for the thermotidal response of rocky planets. This general solution is derived from first principles, assuming either dry or moist adiabatic temperature profiles for the planet’s atmosphere, and can be readily applied to study the long-term evolution of exoplanets in the habitable zones of their host stars.

Despite relying on a small number of parameters, the model successfully captures the key features of the thermotidal torque predicted by General Circulation Models (GCMs). It also accurately predicts Earth’s current semidiurnal thermotidal response and provides new insights into the evolution of the length of day during the Precambrian era.

Pierre Auclair-Desrotour, Mohammad Farhat, Gwenaël Boué, Russell Deitrick, Jacques Laskar

Comments: 5 pages, 2 figures, proceedings of the SF2A annual meeting
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)
MSC classes: 85-06
Cite as: arXiv:2410.16200 [astro-ph.EP] (or arXiv:2410.16200v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2410.16200
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Submission history
From: Pierre Auclair-Desrotour
[v1] Mon, 21 Oct 2024 17:01:42 UTC (704 KB)
https://arxiv.org/abs/2410.16200

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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