The Sun has a powerful magnetic field that creates sunspots on the star’s surface and triggers solar storms, like the one that bathed much of the planet in beautiful auroras this month.
But exactly how this magnetic field is generated inside the Sun is a puzzle that has puzzled astronomers for centuries, dating back to the time of Italian astronomer Galileo Galilei, who made the first observations of sunspots in the early 1600s, and noted how they varied over time.
Researchers behind an interdisciplinary study presented a new theory in a report published Wednesday in Nature magazine. Contrary to previous research that said the Sun’s magnetic field originates inside the celestial body, they suspect the source is much closer to the surface.
The model developed by the team could help scientists better understand the 11-year solar cycle and improve space weather forecasting, which can disrupt GPS and communications satellites, as well as delight night sky watchers with auroras.
See photos of the auroras during rare solar storm in 2024
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Northern lights recorded in the sky over San Francisco, California, in the United States, on May 11, 2024
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Also known as the aurora borealis, the phenomenon lit up the sky over North Carolina, USA.
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The rare solar storm also had its effects on Europe; the sky turned a shade of purple in the Netherlands
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The Northern Lights have also been recorded in Germany
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Another record in Germany shows the mix of purple and pink in the sky
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The sky over Rochester, New York, USA, mixed blue with green after the solar storm
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The northern lights also lit up the sky in Spain; the registration was made in Barcelona
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In the United Kingdom, the sky turned into different colors
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“This work proposes a new hypothesis about how the Sun’s magnetic field is generated that better fits solar observations and, we hope, could be used to make more accurate predictions of solar activity,” said Daniel Lecoanet, assistant professor of solar science. engineering and applied mathematics at the McCormick School of Engineering at Northwestern University and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics.
“We want to predict whether the next solar cycle will be particularly strong or perhaps weaker than normal. Previous models (assuming that the solar magnetic field is generated inside the Sun) have not been able to make accurate predictions or (determine) whether the next solar cycle will be strong or weak,” he added.
Sunspots help scientists track solar activity. They are the point of origin for explosive eruptions and ejection events that release light, solar material and energy into space. The recent solar storm is evidence that the Sun is approaching “solar maximum” — the point in its 11-year cycle when it has the greatest number of sunspots.
“Because we think the number of sunspots tracks the strength of the magnetic field inside the Sun, we think the 11-year sunspot cycle is reflecting a cycle in the strength of the Sun’s internal magnetic field,” Lecoanet said.
Modeling the Sun’s magnetic field
It’s difficult to see the sun’s magnetic field lines, which curve through the solar atmosphere to form a complicated web of magnetic structures much more complex than Earth’s magnetic field. To better understand how the Sun’s magnetic field works, scientists turn to mathematical models.
The model that Lecoanet and his colleagues developed took into account a phenomenon called torsional oscillation — magnetically driven flows of gas and plasma in and around the Sun that contribute to the formation of sunspots.
In some areas, the rotation of this solar resource speeds up or slows down, while in others it remains constant. Just like the 11-year solar magnetic cycle, torsional oscillations also experience an 11-year cycle.
“Solar observations give us a good idea of how material moves inside the Sun. For our supercomputing calculations, we solve equations to determine how the magnetic field changes inside the Sun due to the observed movements,” said Lecoanet.
“No one had done this calculation before because no one knew how to perform the calculation efficiently,” he added.
The group’s calculations showed that magnetic fields can be generated about 20,000 miles (32,100 kilometers) below the surface of the Sun — much closer to the surface than previously assumed. Other models had suggested it was much deeper — about 130,000 miles (209,200 kilometers).
“Our new hypothesis provides a natural explanation for torsional oscillations that is missing in previous models,” said Lecoanet.
Astrophysical enigma
An important advance was the development of new numerical algorithms to perform the calculations, Lecoanet said. The paper’s lead author, Geoff Vasil, a professor at the University of Edinburgh in the United Kingdom, came up with the idea about 20 years ago, Lecoanet said, but it took more than 10 years to develop the algorithms and required a supercomputer from NASA. United States spacecraft) powerful to conduct the simulations.
“We used about 15 million CPU hours for this investigation,” he said. “That means if I had tried to run the calculations on my laptop, it would have taken about 450 years.”
In a commentary published alongside the study, Ellen Zweibel, a professor of astronomy and physics at the University of Wisconsin-Madison, said the initial results were intriguing and would help inform future models and research. She was not involved in the study.
Zweibel said the team added “a provocative ingredient to the theoretical mix that could be key to unlocking this astrophysical enigma.”
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