Physics of the Solar Cromosphere

Project Title Physics of the Solar Cromosphere
Project Leader Prof. Mats Carlsson
Research Field Universe Sciences
Resources awarded 21 760 000 core-hours
Computer Systems HERMIT
Partner Institutions University of Oslo - NO
Utrecht University - NL


This project aims at a breakthrough in our understanding of the solar chromosphere by developing sophisticated radiation-magnetohydrodynamic simulations.

The enigmatic chromosphere is the transition between the solar surface and the eruptive outer solar atmosphere. The chromosphere harbours and constrains the mass and energy loading processes that define the heating of the corona, the acceleration and the composition of the solar wind, and the energetics and triggering of solar outbursts (filament eruptions, flares, coronal mass ejections) that govern near-Earth space weather and affect mankind’s technological environment.

Small-scale MHD processes play a a pivotal role in defining the intricate fine structure and enormous dynamics of the chromosphere, controlling a reservoir of mass and energy much in excess of what is sent up into the corona. This project targets the intrinsic physics of the chromosphere in order to understand its mass and energy budgets and transfer mechanisms. Elucidating these is a principal quest of solar physics, a necessary step towards better space-weather prediction, and of interest to general astrophysics using the Sun as a close-up Rosetta-Stone star and to plasma physics using the Sun and heliosphere as a nearby laboratory.

Our group is world-leading in modelling the solar atmosphere as one system; from the convection zone where the motions feed energy into the magnetic field and all the way to the corona where the release of magnetic energy is more or less violent. The computational challenge is both in simplifying the complex physics without loosing the main properties and in treating a large enough volume to encompass the large chromospheric structures with enough resolution to capture the dynamics of the system. We have developed a massively parallel code, called Bifrost, to tackle this challenge. The resulting simulations are very time-consuming but crucial for the understanding of the magnetic outer atmosphere of the Sun.