Modeling Decadal and Centennial Solar UV Irradiance Changes

Reconstructions of solar spectral irradiance-especially in the ultraviolet (UV) range-are crucial for understanding Earth's climate system. Although total solar irradiance (TSI) has been thoroughly investigated, the spectral composition of solar radiation offers a deeper insight into its interactions with the atmosphere, biosphere, and climate. UV radiation, in particular, plays a key role in stratospheric chemistry and the dynamics of stratospheric ozone. Reconstructing solar irradiance over the past centuries requires accounting for both the cyclic modulation of active-region coverage associated with the 11-year solar cycle and the longer-term secular trends, including their centennial variability. This study utilizes an empirical framework, based on a 1000-year record of open solar flux, to characterize the various temporal components of solar irradiance variability. We then combine these components to reconstruct solar UV irradiance variations in spectral bands crucial for Earth's atmospheric studies.