Chapter 3 - The Sun's Atmosphere

Abstract

The solar atmosphere covers a broad range of temperatures and densities from the solar surface, via the chromosphere and transition region, and to the corona. Although one-dimensional (1D) models of the atmospheric structure have reached a high level of maturity, high–spatial resolution observations have cast some doubt on their validity. Thus, such observations have revealed a richness of highly variable spatial structure, often reaching down to the current resolution limit of 0.1 arcsec, or roughly 70km on the Sun, in the photosphere and chromosphere. These observational advances have led to a new generation of models that describe the solar atmosphere self-consistently using 3D magnetohydrodynamic approximation simulations, including 3D radiative energy transport for those that cover the lower atmosphere, while simplistically taking into account the complex magnetic structure and energy dissipation processes in the upper atmosphere. These models have achieved considerable success in explaining the best observations, although there are still a number of open questions. Nonetheless, thanks to modern advances, the solar atmosphere now provides an excellent setting to test models of stellar atmospheres critically.