New Model Will Help Researchers Find Answers to Mystery Around Evolution of Solar Rotation, Magnetic Fields

In the early 2000s, a new set of data brought down the chemical abundances on the solar surface. It was in contradiction to the numbers predicted by the traditional models used by astrophysicists. While these new abundances were frequently contested, they survived the scrutiny for several years. Though doubts lingered, these data appeared to be correct. So, it was up to the solar models to change, especially since they are used to studying other stars. Thus, an international team led by astronomers from the UNIGE has succeeded in developing a model to solve part of the solar problem.

Scientists from Switzerland's University of Geneva (UNIGE) and Belgium's Universite de Liege (UL) have found an explanation for the structure of the Sun's chemical composition by taking into account the solar rotation and magnetic fields, which have changed over time.

Gael Buldgen, a researcher at the Department of astronomy of the UNIGE and co-author of the study, explained that the standard solar model we used until now considers the Sun, our star, in a very simplified manner. However, everything worked fine until the early 2000s, when an international scientific team drastically revised the solar abundances, thanks to improved analysis. The new abundance caused deep ripples.

From then on, no model was able to reproduce the data obtained by helioseismology (the analysis of the Sun's oscillations), in particular the abundance of helium in the solar envelope.

The UNIGE team's new solar model includes not only the evolution of rotation which was probably faster in the past but also the magnetic instabilities it creates. “We must absolutely consider simultaneously the effects of rotation and magnetic fields on the transport of chemical elements in our stellar models,” said Patrick Eggenberger, a researcher at the Department of Astronomy at UNIGE and the first author of the study.

Scientists have published the results of this study in the journal Nature Astronomy.

However, the new model does not solve every challenge. The researchers hope their findings may help others find answers to the critical answers in the future.