Recent observations of the Earth’s exosphere revealed the presence of an extended hydrogenic component that could reach distances beyond 40 planetary radii. Detection of similar extended exospheres around Earth-like exoplanets could reveal crucial facts in terms of habitability. The presence of these rarified hydrogen envelopes is extremely dependent on the planetary environment, dominated by the ionizing radiation and plasma winds coming from the host star. Radiation and fast wind particles ionize the uppermost layers of planetary atmospheres, especially for planets orbiting active, young stars. The survival of the produced ions in the exosphere of such planets is subject to the action of the magnetized stellar winds, particularly for unmagnetized bodies. In order to address these star–planet interactions, we have carried out numerical 2.5D ideal MHD simulations using the pluto code to study the dynamical evolution of tenuous, hydrogen-rich, Earth-like extended exospheres for an unmagnetized planet, at different stellar evolutionary stages: from a very young, solar-like star of 0.1 Gyr to a 5.0 Gyr star. For each star–planet configuration, we show that the morphology of extended Earth-like hydrogen exospheres is strongly dependent on the incident stellar winds and the produced ions present in these gaseous envelopes, showing that the ionized component of Earth-like exospheres is quickly swept by the stellar winds of young stars, leading to large bow shock formation for later stellar ages.

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围绕类太阳恒星运行的类地扩展外逸层的演化

最近对地球外逸层的观测揭示了一种延伸的氢成分的存在，它的距离可以超过 40 个行星半径。在类地系外行星周围探测到类似的扩展外逸层可以揭示宜居性方面的关键事实。这些稀薄的氢包层的存在非常依赖于行星环境，主要是来自主星的电离辐射和等离子风。辐射和快速风粒子使行星大气的最上层电离，特别是对于围绕活跃的年轻恒星运行的行星。在这些行星的外逸层中产生的离子的生存受到磁化恒星风的作用，特别是对于未磁化的物体。为了解决这些恒星-行星相互作用，我们进行了数值 2。5D 理想 MHD 模拟使用 pluto 代码研究在不同恒星演化阶段的未磁化行星的稀薄、富含氢、类地扩展外逸层的动态演化：从 0.1 Gyr 的非常年轻的类太阳恒星到5.0 陀螺星。对于每个恒星-行星配置，我们表明扩展的类地氢外逸层的形态强烈依赖于入射的恒星风和这些气体包层中存在的离子，表明类地外逸层的电离成分被迅速扫过受到年轻恒星的星风的影响，导致后来恒星时代的大弓形激波形成。从 0.1 Gyr 的非常年轻的类太阳恒星到 5.0 Gyr 的恒星。对于每个恒星-行星配置，我们表明扩展的类地氢外逸层的形态强烈依赖于入射的恒星风和这些气体包层中存在的离子，表明类地外逸层的电离成分被迅速扫过受到年轻恒星的星风的影响，导致后来恒星时代的大弓形激波形成。从 0.1 Gyr 的非常年轻的类太阳恒星到 5.0 Gyr 的恒星。对于每个恒星-行星配置，我们表明扩展的类地氢外逸层的形态强烈依赖于入射的恒星风和这些气体包层中存在的离子，表明类地外逸层的电离成分被迅速扫过受到年轻恒星的星风的影响，导致后来恒星时代的大弓形激波形成。