Stellar high-energy radiation (X-ray and extreme ultraviolet, XUV) drives atmospheric escape in close-in exoplanets. Given that stellar irradiation depends on the stellar magnetism and that stars have magnetic cycles, we investigate how cycles affect the evolution of exoplanetary atmospheric escape. Firstly, we consider a hypothetical HD209458b-like planet orbiting the Sun. For that, we implement the observed solar XUV radiation available over one and a half solar cycles in a 1D hydrodynamic escape model of HD209458b. We find that atmospheric escape rates show a cyclic variation (from 7.6 to 18.5 $\times$ 10$^{10}$ g s$^{-1}$), almost proportional to the incident stellar radiation. To compare this with observations, we compute spectroscopic transits in two hydrogen lines. We find non-detectable cyclic variations in Ly$\alpha$ transits. Given the temperature sensitiveness of the H$\alpha$ line, its equivalent width has an amplitude of 1.9 mA variation over the cycle, which could be detectable in exoplanets such as HD209458b. We demonstrate that the XUV flux is linearly proportional to the magnetic flux during the solar cycle. Secondly, we apply this relation to derive the cyclic evolution of the XUV flux of HD189733 using the available magnetic flux observations of the star from Zeeman Doppler Imaging over nearly a decade. The XUV fluxes are then used to model escape in HD189733b, which shows escape rate varying from 2.8 to 6.5 $\times$ 10$^{10}$ g s$^{-1}$. Like in the HD209458b case, this introduces variations in Ly$\alpha$ and H$\alpha$ transits, with H$\alpha$ variations more likely to be observable. Finally, we show that a strong stellar flare would enhance significantly Ly$\alpha$ and H$\alpha$ transit depths.

中文翻译：

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类太阳磁循环对系外行星大气逃逸的影响

恒星高能辐射（X 射线和极紫外线，XUV）驱动近距离系外行星的大气逃逸。鉴于恒星辐射取决于恒星的磁性，并且恒星具有磁循环，我们研究了循环如何影响系外行星大气逃逸的演化。首先，我们考虑一个假设的类 HD209458b 行星绕太阳运行。为此，我们在 HD209458b 的一维流体动力学逃逸模型中实现了一个半太阳周期内可用的观测太阳 XUV 辐射。我们发现大气逃逸率呈现出周期性变化（从 7.6 到 18.5 $\times$ 10$^{10}$ gs$^{-1}$），几乎与入射恒星辐射成正比。为了将其与观察结果进行比较，我们计算了两条氢谱线中的光谱凌日。我们在 Ly$\alpha$ 传输中发现了不可检测的循环变化。考虑到 H$\alpha$ 线的温度敏感性，它的等效宽度在整个周期内具有 1.9 mA 的幅度变化，这可以在系外行星（如 HD209458b）中检测到。我们证明了 XUV 通量与太阳周期中的磁通量成线性比例。其次，我们利用塞曼多普勒成像近十年来对该恒星的可用磁通量观测，应用这种关系来推导出 HD189733 的 XUV 通量的循环演化。然后使用 XUV 通量模拟 HD189733b 中的逃逸率，其显示逃逸率从 2.8 到 6.5 $\times$ 10$^{10}$ gs$^{-1}$ 不等。就像在 HD209458b 的情况下一样，这引入了 Ly$\alpha$ 和 H$\alpha$ 传输的变化，其中 H$\alpha$ 变化更可能被观察到。最后，