(@JohnstoneGuedel15), meaning that larger fractions of their X-ray and extreme ultraviolet emission are at the higher energy parts of the spectrum (@Guedel04; @SanzForcada11). In Fig. \[fig:XUVtracks\], I show evolutionary tracks for the X-ray emission of solar mass stars with different initial rotation rates, where the shades region shows the range of activity levels that I study in this paper. In this paper, I use the X-ray flux, $F_\mathrm{X}$, at the planet’s orbit as the measure of stellar activity because the X-ray luminosity of a star is easily measured and often available for exoplanet hosts.

To calculate the atmospheric structures and loss rates, I use The Kompot Code, recently developed by @Johnstone18 and @Johnstone19a. This is a sophisticated general-purpose first-principles physical model for the upper atmospheres of planets, developed to take into account the range of physical processes taking place in the upper atmosphere. The model has been designed such that it can be applied to any type of planet with arbitrary atmospheric compositions. In @Johnstone18, detailed descriptions of the physical model (Section 2) and numerical methods (Appendices) can be found. As in @Johnstone19a, I have simplied slightly the model presented in @Johnstone18 by removing the assumption that the neutrals, ions, 