Earth-like Atmosphere in the Habitable Zone of AD Leonis: Ozone Depletion, Surface UV, and Methane Stability under a Major Flare in a 1-D Photochemical–Radiative-Convective Model

To the point

Around AD Leonis (AD Leo) at 0.16 AU, an Earth-like planet would see only modest ozone loss and Earth-like surface UV during a UV-only flare, but if a proton event accompanies the flare it could wipe out most ozone within a couple of years on a planet with no magnetic field and push surface UV above Earth's at the peak, while methane stays fairly stable and upper-stratospheric water vapor drops, and a magnetic field would reduce proton entry and ozone loss though recovery and global depletion are upper-limit estimates in a simplified model; overall, a single energetic flare may not ruin habitability or biosignatures, but repeated flaring and magnetic shielding would shape atmospheric evolution and surface UV exposure.