A new theoretical model explains the rotation of the sun and the magnetic field

A new theoretical model explains the rotation of the sun and the magnetic field

The model developed by the scientists includes the history of the Sun’s rotation and also the magnetic instability it generates. (c) Sylvia Ekström/UNIGE

In the early 2000s, a new set of data revised the chemical abundance on the Sun’s surface, contradicting values ​​predicted by standard models used by astrophysicists. This new abundance has often been challenged by several new analyses. As they seemed to be correct, it was up to the solar models to adapt, especially as they serve as a reference for the study of stars in general. A team of astronomers from the University of Geneva, Switzerland (UNIGE) in collaboration with the University of Liège, has developed a new theoretical model that solves part of the problem: looking at the Sun’s rotation, which has changed through time, and its magnetic fields. born, they have been able to explain the chemical composition of the sun. The results of this study were published in natural astronomy.

“The Sun is the star we can best discern, so it is an essential test of our understanding of stellar physics. We have abundant measurements of it. chemical elementsbut also measurements of its internal structure, as in the case of the Earth thanks to seismology,” explains Patrick Egenberger, researcher in the Department of Astronomy at UNIGE and first author of the study.

These observations must be consistent with the results he predicted theoretical models Which aims to explain the evolution of the Sun. How does the sun burn hydrogen in the heart? How is energy produced there and then transferred toward the surface? How Chemicals Elements drifting inside the sun, affected by rotation and magnetic fields?

Solar Standard Model

“The standard solar model that we have used so far considers our star in a very simplified way, on the one hand, with regard to the transport of chemical elements in the deeper layers; on the other hand, to the rotation and internal magnetic fields that have been completely neglected until now,” explains Gail Boldgen, researcher in the Department of Astrobiology. Astronomy at UNIGE and co-author of the study.

However, all went well until the early 2000s, when an international scientific team made a drastic review of solar energy abundance thanks to improved analysis. The new abundance created deep ripples in the solar modeling waters. Since then, no model has been able to reproduce the data obtained by heliosmology (analysis of the sun’s oscillations), in particular the abundance of helium in the heliosphere.

A new model and the main role of rotation and magnetic fields

The new solar model developed by the UNIGE team includes not only the evolution of the spin that may have been faster in the past, but also the magnetic instability it created. “We must simultaneously consider the effects of rotation and magnetic fields on the transport of chemical elements in our stellar models. It is as important for the Sun as it is for stellar physics in general and has a direct impact on the chemical evolution of the universe, given the necessary chemical elements,” says Patrick Egenberger. Life on Earth is cooked up in the heart of the stars.”

The new model not only correctly predicts the concentration of helium in the outer layers of the Sun, but also reflects the concentration of lithium that has resisted modeling so far. “The abundance of helium is correctly reproduced by the new model because the internal rotation of the Sun imposed by magnetic fields generates turbulent mixing that prevents this element from falling too rapidly towards the center of the star; at the same time, an abundance of lithium is observed on the surface of the Sun is also being reproduced because this The blending itself takes it to hot spots where it gets destroyed,” explains Patrick Eggenberger

The problem has not been completely resolved

However, the new model does not solve all the challenges raised by helioscience: “Thanks to helioscience, we know within 500 km in which region convective motions of matter begin, 19,500 km below the surface of the Sun. However, theoretical models predict the Sun with a depth of 10,000 km,” says Sebastian Salmon, a UNIGE researcher and co-author of the paper. If the problem persists in the new paradigm, it opens a new door to understanding: “Thanks for the new paradigm ModelWe are shedding light on the physical processes that can help us resolve this critical difference.”

Sun-like stars update

“We will have to review the masses, radii and ages obtained for the stars of the solar type that we have studied so far,” says Gaël Buldgen, detailing the following steps. In fact, in most cases, solar physics is transferred to case studies near the Sun. Therefore, if the Sun’s analysis models are modified, this update should also be done for other stars similar to ours.

Patrick Eggenberger says: “This is particularly important if we want to better characterize planet host stars, for example within the framework of the PLATO mission.” This observatory of 24 telescopes must fly to Lagrange Point 2 (1.5 million km from Earth, opposite the Sun) in 2026 to discover and characterize minor planets and improve the properties of their host star.

The primary overshoot is limited by the absence of a convective core and some Sun-like stars

more information:
P. Eggenberger et al, The internal rotation of the Sun and its association with Li and He solar surface abundance, natural astronomy (2022). DOI: 10.1038 / s41550-022-01677-0

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the quote: A New Theoretical Model Explaining the Sun’s Rotation and Magnetic Field (2022, May 31) Retrieved May 31, 2022 from https://phys.org/news/2022-05-theoretical-accounts-sun-rotation-magnetic.html

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