Stellar butterfly diagrams

• Applicant: Professor Dr. Laurent Gizon
• Subject Area: Astrophysics and Astronomy ; Computer Architecture, Embedded and Massively Parallel Systems
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 530101854

The spatial distribution of sunspots as a function of time (the solar butterfly diagram) provides important constraints on solar dynamo models. In this project, we plan to show using advanced numerical simulations that the latitude of starspots can be inferred on distant stars from stellar light curves. These light curves provide two independent diagnostics of magnetic activity: (1) dark starspots and bright faculae modulate the intensity on the time scale of the rotation (~27 days for the sun) and (2) magnetic activity leads to an increase of the frequencies of the global modes of acoustic oscillation (acoustic waves travel faster in magnetic regions). In this project, we will model the perturbations in intensity and in the seismic observables due to a given distribution of spots and faculae on the solar surface. We will solve the equations of solar oscillations with rotation considering localized wave-speed perturbations near the surface. We will use a massively parallel numerical approach based on a high-order hybridized discontinuous Galerkin method. We will further couple this approach with boundary element methods to allow the treatment of solar active regions while drastically reducing the computational cost. We will the invert the seismic disturbances to retrieve the latitude of the solar active regions. The forward and inverse techniques will be validated using solar observations. This interdisciplinary project builds on an ongoing collaboration between applied mathematicians (in Pau, France) and solar physicists (in Goettingen, Germany). The results of this work will contribute to the analysis of magnetic activity for many thousands of Sun-like stars to be observed by the PLATO mission of the European Space Agency (to be launched in 2026).

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Privatdozentin Dr. Helene Barucq