New theoretical model takes into account the rotation of the Sun and the magnetic field

(ORDO NEWS) — In the early 2000s, a new set of data showed a chemical abundance on the surface of the Sun, which greatly contradicted the already formed ideas of astrophysicists.

Since they turned out to be correct, the solar models had to adapt. A group of astronomers from the University of Geneva, Switzerland (UNIGE), in collaboration with the University of Liege, have developed a new theoretical model that partly solves this problem: given the rotation of the Sun, which changes over time, and the magnetic fields it generates, they were able to explain the chemical structure of the Sun .

“The sun is the star that we can best describe. We have measurements of the abundance of its chemical elements, as well as measurements of its internal structure, as in the case of the Earth, thanks to seismology,” explains Patrick Eggenberger, researcher in the UNIGE Department of Astronomy and the first author of the study.

These observations should be consistent with the results predicted by theoretical models that aim to explain the evolution of the Sun.

How does the Sun burn its hydrogen at the core? How is energy generated there and then transported to the surface? How do chemical elements drift inside the Sun under the influence of rotation and magnetic fields?

The new model of the Sun, developed by the UNIGE team, includes not only the evolution of rotation, which was probably faster in the past, but also the magnetic instabilities that it creates.

In addition, the new model correctly predicts the concentration of helium in the outer layers of the Sun and reflects the concentration of lithium, which has so far defied modeling.

“The abundance of helium is correctly reproduced by the new model because the internal rotation of the sun, caused by magnetic fields, creates turbulent mixing that prevents this element from falling too quickly towards the center of the star,” explains Patrick Eggenberger.

However, the new model does not solve all the problems: thanks to helioseismology, we know with an accuracy of up to 500 km in which area the convective motions of matter begin, at a depth of 199,500 km below the surface of the Sun.

However, theoretical models predict a depth shift of 10,000 km. The new model sheds light on physical processes that can help resolve this critical discrepancy.

We will have to revise the masses, radii, and ages obtained for solar-type stars that have been studied previously. Indeed, in most cases, solar physics is carried over to case studies close to the Sun. Therefore, if the models for analyzing the Sun are changed, this update should also be done for other stars like ours.


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