Description
Understanding the variability of stellar XUV irradiances is crucial due to their influence on surrounding planetary environments. The Sun provides the best laboratory for studying irradiance variability, driven by magnetic flux emergence and causing space weather effects. These variations strongly affect Earth’s ionosphere and thermosphere, influencing atmospheric expansion, satellite drag, and communication systems. However, despite continuous monitoring, solar irradiance measurements remain limited in wavelength coverage and long-term consistency, necessitating predictive modeling to reconstruct missing data.
To address this, we have developed a predictive model for spectral irradiances, initially calibrated using solar EUV/UV observations from SOHO/CDS and SDO/EVE, and correlated with solar activity proxies such as F10.7, F30, the Mg II index, and sunspot number. This model incorporates fundamental plasma parameters—chemical abundances, densities, and temperatures—using the latest atomic data from CHIANTI v.11, significantly improving irradiance predictions for transition region lines.
Extending this model to stellar atmospheres enables irradiance predictions for stars with limited or no direct measurements. Such advancements are critical for exoplanetary research, as stellar spectral energy distributions dictate planetary atmospheric chemistry, escape processes, and habitability. By bridging solar and stellar physics, this model provides a robust tool for characterizing exoplanetary environments and understanding how stellar activity influences planetary evolution.
