Stellar wind and photon radiation interactions with a planet can cause atmospheric depletion, which may have a potentially catastrophic impact on a planet’s habitability. While photon interactions with planetary atmospheres and outflows have been researched to some degree, studies of stellar wind interactions are in their infancy. Here, we use three-dimensional magnetohydrodynamic simulations to model the effect of the stellar wind on the magnetosphere and outflow of a hypothetical planet, modeled to have an H-rich evaporating envelope with a prescribed mass-loss rate, orbiting in the habitable zone close to a low-mass M dwarf. We take the TRAPPIST-1 system as a prototype, with our simulated planet situated at the orbit of TRAPPIST-1e. We show that the atmospheric outflow is accelerated and advected upon interaction with the wind, resulting in a diverse range of planetary magnetosphere morphologies and plasma distributions as local stellar wind conditions change along the orbit. We consider the implications of the wind–outflow interaction on potential hydrogen Lyα observations of the planetary atmosphere during transits. The Lyα observational signatures depend strongly on the local wind conditions at the time of the observation and can be subject to considerable variation on timescales as short as an hour. Our results indicate that observed variations in exoplanet transit signatures could be explained by wind–outflow interaction.

恒星风和光子辐射与行星的相互作用会导致大气损耗，这可能对行星的宜居性产生潜在的灾难性影响。虽然已经在一定程度上研究了光子与行星大气和外流的相互作用，但对恒星风相互作用的研究还处于起步阶段。在这里，我们使用三维磁流体动力学模拟来模拟恒星风对磁层和假想行星外流的影响，模拟为具有具有规定质量损失率的富含 H 的蒸发包层，在宜居带附近绕轨道运行。到一个低质量的 M 矮星。我们以 TRAPPIST-1 系统为原型，我们的模拟行星位于 TRAPPIST-1e 的轨道上。我们表明大气外流在与风相互作用时加速并平流，随着当地恒星风条件沿轨道变化，导致各种行星磁层形态和等离子体分布。我们考虑风-流出相互作用对潜在氢 Ly 的影响α在凌日期间对行星大气的观测。Ly α观测特征在很大程度上取决于观测时的当地风况，并且可能会在短至一小时的时间尺度上发生相当大的变化。我们的结果表明，观察到的系外行星凌日特征的变化可以通过风-外流相互作用来解释。