Space Weather & Heliophysics

The Impact Of Stellar Flares On The Atmospheric Escape of Exoplanets Orbiting M stars I: Insights From The AU Mic System

By Keith Cowing

Status Report

astro-ph.EP

March 19, 2025

Filed under astro-ph.EP, atmosphere, AU Mic, AU Mic d, exoplanet, flares, habitability, Habitable Zone, HAZMAT, heliophysics, MUSCLES, radiation, space weather, Stellar flare

The Impact Of Stellar Flares On The Atmospheric Escape of Exoplanets Orbiting M stars I: Insights From The AU Mic System — Atmospheric evolution of the planets AU Mic b (closest from the star), d (in between AU Mic b and c), and c (furthest from the star). a) XUV flux reaching the planet, b) primordial H/He envelope mass, c) planetary radius, and d) loss rate of the atmospheric mass. The shadows represent the associated errors in the results, considering the uncertainties for the current masses and radii of the AU Mic planets. — astro-ph.EP

The X-rays and Extreme Ultraviolet (XUV) emission from M stars can drive the atmospheric escape on planets orbiting them. M stars are also known for their frequent emission of stellar flares, which will increase the high-energy flux received by their orbiting planets.

To understand how stellar flares impact the primordial atmospheres of planets orbiting young M stars, we use UV spectroscopic data of flares from the Habitable Zones and M dwarf Activity across Time (HAZMAT) and Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems (MUSCLES) programs as a proxy to the XUV flare emission. Using the software package VPLanet, we simulate the young AU Mic planetary system composed of two Neptune-sized and one Earth-sized planet orbiting a 23-Myr-old M1 star.

Our findings show that the Earth-sized planet AU Mic d should be in the process of losing completely its atmosphere in the next couple million years, solely due to the quiescent emission, with flares not significantly contributing to its atmospheric escape due to the small size of AU mic d and its close-in distance from the star.

However, our results indicate that flares would play a crucial role for such planets further away, in the habitable zone (i.e. 0.2935 AU) of AU Mic-like stars during the post-saturation phase, accelerating the total atmospheric loss process by a few billion years. For planets between 0.365 AU and the HZ outer edge, the additional XUV from flares is necessary to deplete primordial atmospheres fully since the quiescent emission alone is insufficient.

Laura N. R. do Amaral, Evgenya L. Shkolnik, R. O. Parke Loyd, Sarah Peacock

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Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2503.13353 [astro-ph.EP] (or arXiv:2503.13353v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2503.13353
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Submission history
From: Laura Neves Ribeiro Do Amaral
[v1] Mon, 17 Mar 2025 16:34:20 UTC (4,332 KB)
https://arxiv.org/abs/2503.13353
Astrobiology, Space Weather,

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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