Whole Sun: Untangling the complex physical mechanisms behind our eruptive magnetic star and its twins

How does the Sun work? Why does it possess a magnetic cycle, dark spots and a dynamic hot atmosphere? These are questions that remain mostly unanswered. In the "Whole Sun" project, we aim at tackling these key questions as a coherent whole for the first time.

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Simulation of the solar dynamo that generates the magnetic field (left, simulation by the group in Saclay) and a simulation of the outer solar atmosphere (right, simulation by the group in Oslo) where the emerging field interacts with pre-existing field creating explosions and jets.

About the project

For too many years, the Sun has been split into internal and external solar physics topics and a global integrated view of its complex plasma dynamics has been lacking. For instance, dynamo simulations seeking to answer the origin of the magnetic field and of its cyclic behaviour neglect surface physics and the existence of sunspots, likewise surface models often assume the magnetic field as a given input without the detailed knowledge of the nonlinear interplay between convection, rotation and magnetic fields in the Sun’s outer envelope. The time has come to gather world leading European solar/stellar physicists to build a deeper understanding of our star and to extend it to its twins. To do so, many bottlenecks must be addressed: highly disparate spatial and temporal scales, physical interfaces of all solar layers, complex microphysics and global effects strong dynamics and how parameters such as star’s metallicity, mass and rotation influence the outcome. By gathering physicists from each side of the solar surface we aim at tackling these challenging, beyond the state-of-the-art, problems by developing a deep theoretical understanding of our star and its analogues and by building the most advanced multi-resolution solar code, in order to jointly address global/macrophysics and local/microphysics aspects of the solar dynamics. The advent of Exa-scale computers makes such a challenge within our reach, as do modern analysis methods to interpret observations and the 4-D data cubes that the project will produce or access. 


The objective is to determine over the next six years how the magnetic field is generated inside the Sun and how it creates solar spots on its surface and eruptions in its highly stratified atmosphere.

Competences and tools

Map showing the work-flow and vision behind the WHOLE SUN project.

The 4 PIs of the WHOLE SUN project consist of:

  • Sacha Brun (Commisariat à l’Energie Atomique et et aux Energies Alternatives, Saclay, France),
  • Laurent Gizon (Max Planck Institute for Solar System Research, Göttingen, Germany),
  • Vasilis Archontis (University of St Andrews, UK)
  • Mats Carlsson, (University of Oslo, Norway),

In addition, Fernando Moreno-Insertis is leading the work by the associated institution Instituto de Astrofísica de Canarias (IAC), Spain.

The team in Saclay are experts on dynamo simulations (how the solar magnetic field is generated); the team in Göttingen are experts on using helioseismology to get information from the interior of the Sun; the team in St Andrews specialises in the study of how magnetic flux emerges through the surface. The team at IAC has complementary competences in both observational solar physics and in modelling. Finally the members or RoCS are experts on the outer solar atmosphere (chromosphere and corona).

Project period

Start - finish: 2019 - 2024


This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 - EXCELLENT SCIENCE (Grant agreement ID: 810218).

Published Nov. 14, 2019 12:05 PM - Last modified Mar. 9, 2022 11:32 AM