Atmospheric escape in hot Jupiters under sub-Alfvénic interactions
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| Format: | Preprint |
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2024
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| _version_ | 1866929538071527424 |
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| author | Presa, Andrés Driessen, Florian A. Vidotto, Aline A. |
| author_facet | Presa, Andrés Driessen, Florian A. Vidotto, Aline A. |
| contents | Hot Jupiters might reside inside the Alfvén surface of their host star wind, where the stellar wind is dominated by magnetic energy. The implications of such a sub-Alfvénic environment for atmospheric escape are not fully understood. Here, we employ 3-D radiation-magnetohydrodynamic simulations and Lyman-$α$ transit calculations to investigate atmospheric escape properties of magnetised hot Jupiters. By varying the planetary magnetic field strength ($B_p$) and obliquity, we find that the structure of the outflowing atmosphere transitions from a magnetically unconfined regime, where a tail of material streams from the nightside of the planet, to a magnetically confined regime, where material escapes through the polar regions. Notably, we find an increase in the planet escape rate with $B_p$ in both regimes, with a local decrease when the planet transitions from the unconfined to the confined regime. Contrary to super-Alfvénic interactions, which predicted two polar outflows from the planet, our sub-Alfvénic models show only one significant polar outflow. In the opposing pole, the planetary field lines connect to the star. Finally, our synthetic Ly-$α$ transits show that both the red-wing and blue-wing absorptions increase with $B_p$. Furthermore, there is a degeneracy between $B_p$ and the stellar wind mass-loss rate when considering absorption of individual Lyman-$α$ wings. This degeneracy can be broken by considering the ratio between the blue-wing and the red-wing absorptions, as stronger stellar winds result in higher blue-to-red absorption ratios. We show that, by using the absorption ratios, Lyman-$α$ transits can probe stellar wind properties and exoplanetary magnetic fields. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2410_08881 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Atmospheric escape in hot Jupiters under sub-Alfvénic interactions Presa, Andrés Driessen, Florian A. Vidotto, Aline A. Earth and Planetary Astrophysics Solar and Stellar Astrophysics Hot Jupiters might reside inside the Alfvén surface of their host star wind, where the stellar wind is dominated by magnetic energy. The implications of such a sub-Alfvénic environment for atmospheric escape are not fully understood. Here, we employ 3-D radiation-magnetohydrodynamic simulations and Lyman-$α$ transit calculations to investigate atmospheric escape properties of magnetised hot Jupiters. By varying the planetary magnetic field strength ($B_p$) and obliquity, we find that the structure of the outflowing atmosphere transitions from a magnetically unconfined regime, where a tail of material streams from the nightside of the planet, to a magnetically confined regime, where material escapes through the polar regions. Notably, we find an increase in the planet escape rate with $B_p$ in both regimes, with a local decrease when the planet transitions from the unconfined to the confined regime. Contrary to super-Alfvénic interactions, which predicted two polar outflows from the planet, our sub-Alfvénic models show only one significant polar outflow. In the opposing pole, the planetary field lines connect to the star. Finally, our synthetic Ly-$α$ transits show that both the red-wing and blue-wing absorptions increase with $B_p$. Furthermore, there is a degeneracy between $B_p$ and the stellar wind mass-loss rate when considering absorption of individual Lyman-$α$ wings. This degeneracy can be broken by considering the ratio between the blue-wing and the red-wing absorptions, as stronger stellar winds result in higher blue-to-red absorption ratios. We show that, by using the absorption ratios, Lyman-$α$ transits can probe stellar wind properties and exoplanetary magnetic fields. |
| title | Atmospheric escape in hot Jupiters under sub-Alfvénic interactions |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2410.08881 |