One of the most remarkable properties of the Sun’s atmosphere, which, despite decades of research, is still not understood, is its thermal structure. Along with many other stars, the Sun's outer atmosphere has an extremely high temperature, rising from a surface (photosphere) temperature of 4000-6000 K, through the chromosphere and transition region to several million degrees in the outer atmosphere (corona). It has long been known that the Sun's magnetic field is responsible for the supply of energy to the atmosphere. However, how this magnetic energy is converted into thermal energy is still not understood, as models struggle to simultaneously encompass the very disparate temporal and spatial scales on which the heating has to occur.
The project aims to tackle the long-standing question of the extremely high temperatures in the Sun’s outer atmosphere (corona) by taking a comprehensive approach: forward modelling (creating synthetic observations) will be used to (i) link 3D numerical simulations of in-depth models with large scale computational experiments and (ii) provide observational diagnostics to compare models to high resolution, multi wavelength observations both qualitatively and quantitatively. This timely, multi-scale approach will achieve an innovative synergy between coronal heating and coronal seismology, where the coronal heating models will use input from, and be benchmarked against, information gained about the solar atmosphere through coronal seismology.
With this project, we aim to answer the fundamental question: Can we unambiguously identify physical heating mechanisms and determine their relative contributions, both in large-scale numerical simulations and high-resolution observations and, if so, how? In parallel, the advanced 3D computational models will provide a ‘proof of concept’ for coronal seismology, i.e. establish the robustness of the currently used simple models and how the interpretation of observed waves and oscillations in the optically thin solar atmosphere is affected by line-of-sight integration and instrument resolution.
The ultimate test for any coronal heating model would be whether (using different parameters) it could explain other hot, ‘stellar’ atmospheres. As the search for habitable exoplanets intensifies, understanding the host stars is crucial and the Sun should provide a 'benchmark' model for the study of other solar-like stars. Although we will not address stellar atmospheric heating explicitly, our multi-scale approach is a key stepping stone towards stellar heating models.
