# Non-Equilibrium Spectrum Formation Affecting Solar Irradiance

## TL;DR

This paper reviews how non-equilibrium processes in the solar atmosphere influence the formation of spectra and affect solar irradiance, highlighting challenges in modeling ultraviolet and infrared radiation.

## Contribution

It provides a comprehensive overview of non-equilibrium effects on solar spectrum formation and discusses key obstacles in simulation-based irradiance studies.

## Key findings

- NLTE scattering complicates ultraviolet line formation
- Retarded hydrogen opacities affect infrared and millimeter radiation
- Graphical exposition clarifies spectrum formation processes

## Abstract

This is an overview of non-equilibrium aspects of the formation of solar continua and lines affecting the contributions by magnetic network and plage to spectrally resolved solar irradiance. After a brief summary of these contributions and a compact refresher of solar spectrum formation, the emphasis is on graphical exposition. Major obstacles for simulation-based irradiance studies are how to cope with NLTE scattering in the violet and ultraviolet line haze and how to cope with retarded hydrogen opacities in infrared and mm radiation.