Subscribe to CNN’s Wonder Theory science newsletter. Explore the universe with news about fascinating discoveries, scientific advances and more.
CNN
—
The sun has a strong magnetic field that creates sunspots on the star’s surface and unleashes solar storms like the one that bathed much of the planet in spectacular auroras this month.
But exactly how this magnetic field is generated inside the Sun is a puzzle that has plagued astronomers for centuries, dating back to the time of the Italian astronomer Galileo, who made the first observations of sunspots in the early 17th century and noticed how they changed over time.
The researchers behind the interdisciplinary study put forward a new theory in a report published Wednesday in the journal Nature. Unlike previous research that assumed the Sun’s magnetic field came from deep within 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 forecasts of space weather, which can disrupt GPS and communications satellites, as well as dazzle night sky watchers with auroras.
“This work proposes a new hypothesis about how the Sun’s magnetic field is created that better matches observations of the Sun, and we hope it could be used to make better predictions of solar activity,” said Daniel Lecoanet, assistant professor of engineering and applied sciences. in Mathematics at Northwestern University’s McCormick School of Engineering 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 the solar magnetic field is generated deep within 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 starting point for explosive flares and ejections 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 there are the highest number of sunspots.
“Because we think that the number of sunspots follows the strength of the magnetic field in the Sun, we think that the 11-year sunspot cycle reflects a cycle in the strength of the Sun’s internal magnetic field,” Lecoanet said.
NASA/GSFC/Solar Dynamics Observatory
This view of the Sun’s magnetic field was created by NASA’s Solar Dynamics Observatory.
It is difficult to see the Sun’s magnetic field lines, which pass through the Sun’s atmosphere and create a complicated network of magnetic structures far more complex than Earth’s magnetic field. To better understand how the Sun’s magnetic field works, scientists turn to mathematical models.
In a scientific first, the model Lecoanet and his colleagues developed accounted for a phenomenon called torsional oscillations—magnetically driven flows of gas and plasma in and around the Sun that contribute to the formation of sunspots.
In some regions, the rotation of this solar body speeds up or slows down, while in others it remains stable. Like the 11-year solar magnetic cycle, torsional oscillations experience an 11-year cycle.
“Solar observations have given us a good idea of how material moves inside the Sun. For our supercomputer calculations, we solved equations to determine how the magnetic field in the Sun changes as a result of the observed motions,” said Lecoanet.
“No one had done this calculation before because no one knew how to do the calculation efficiently,” he added.
The team’s calculations showed that magnetic fields can be generated about 20,000 miles (32,100 kilometers) below the Sun’s surface — much closer to the surface than previously thought. Other models 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 from previous models,” said Lecoanet.
An important breakthrough 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 the algorithms took more than 10 years to develop and required NASA’s powerful supercomputer. simulation.
“We used about 15 million CPU hours on this investigation,” he said. “That means if I tried to do the calculations on my laptop, it would take me about 450 years.
In a commentary published along with the study, Ellen Zweibel, a professor of astronomy and physics at the University of Wisconsin-Madison, said the initial results are interesting and will help inform future models and research. She was not involved in the study.
Zweibel said the team has added “a provocative ingredient to the theoretical mix that could prove key to unraveling this astrophysical mystery.”