Spectral Irradiance Variability from Sun to Stars

Solar radiation is the primary energy source for Earth’s atmosphere, and it varies across all resolved timescales. While X-rays are absorbed in the upper atmosphere, UV radiation reaches the middle atmosphere and drives chemical and physical processes that shape its photochemistry, dynamics, temperature, and composition. We investigate how variability associated with the ~27-day solar rotation and the ~11-year solar activity cycle affects Earth’s middle atmosphere. Using one- and three-dimensional chemistry–climate models, we examine the sensitivity of key species (OH, H₂O, O₃) and temperature to changes in spectral solar irradiance. We also assess how uncertainties across spectral solar irradiance data sets propagate into modeled responses and confront the simulations with atmospheric measurements. Extending beyond the Sun, we explore how stellar parameters reshape stellar UV spectra and, in turn, modulate exoplanetary ozone shielding and surface UV exposure.

Moderation: Julia Danzer