Left: best-fit RADYN model and uncertainty region for the F1 peak spectrum, determined from all models with residuals within 100% of the best-fit value. The XUV emission driving atmospheric escape, FUV–NUV emission driving photochemistry, and TESS wavelengths are highlighted. The prediction capability degrades with distance from the NIR. Middle: RADYN SEDs enable scaling of the TESS-band flare rate into the XUV, FUV, and NUV. Right: comparison of flaring and quiescent contributions to the XUV radiation environment, where the quiescent relation is reproduced from D. P. Fleming et al. (2020). The flaring XUV activity–age relation is constructed from the present-day XUV flare rate, the estimated saturation flare rate relative to the present day (R. R. Paudel et al. 2018), and the estimated ∼4 Gyr saturation knee (D. P. Fleming et al. 2020).