Researchers Trace the Origin of the Sun’s Magnetic Field, Shedding Light on Space Weather and Solar Cycles

In a new study, scientists suggest the sun’s magnetic field originates much closer to the star’s surface than previously thought, a finding that could boost predictions of solar activity

the yellow glowing sun with thin loops drawn coming off of it, concentrated around bright spots and more centered around the middle of the star, rather than its poles
An illustration of the sun's magnetic fields overlaid on an image of the sun captured by NASA's Solar Dynamics Observatory in 2016. NASA / SDO / AIA / LMSAL

The sun’s magnetic field could form much closer to the star’s surface than previously thought, according to new research published Wednesday in the journal Nature. The findings could help improve forecasts of solar activity that can affect satellites, power grids and communications systems on Earth—and produce magnificent auroras.

“This work proposes a new hypothesis for how the sun’s magnetic field is generated that better matches solar observations, and, we hope, could be used to make better predictions of solar activity,” Daniel Lecoanet, a co-author of the study and a fluid dynamicist at Northwestern University, tells CNN’s Katie Hunt.

Ellen Zweibel, an astrophysicist at the University of Wisconsin-Madison who did not contribute to findings, calls the results “intriguing” in an editorial accompanying the article. “They could well furnish an interpretative framework for more elaborate models, and they are sure to inspire future studies.”

The flow of plasma within the sun creates the star’s magnetic field. This means the sun has two magnetic poles, like the Earth—but every 11 years, these poles flip positions. As the star goes through this cycle, it gradually shifts between periods of low and high activity.

Its magnetic field plays a role in events like solar flares, explosions that shoot energy, light and high-speed particles into space, as well as coronal mass ejections, solar magnetic storms that expel gas and magnetic fields. Dark areas on the sun’s surface called sunspots are also a result of the magnetic field and are thought to be tied to solar flares, coronal mass ejections and other space weather.

Right now, the sun is nearing the end of a cycle and approaching peak activity at its “solar maximum.” It’s currently experiencing intense solar storms that result in widespread auroras—like when, earlier this month, the strongest geomagnetic storm since 2003 caused the Northern Lights to be visible across much of the United States, even Florida.

Despite the importance of the sun’s magnetic field to all these events, scientists still don’t fully grasp its structure or how it is generated.

“We still don’t understand the sun well enough to make accurate predictions” of space weather, study co-author Geoffrey Vasil, a mathematician at the University of Edinburgh in Scotland, tells Marcia Dunn of the Associated Press (AP).

The sun with dark sunspots just below its center
It may look relatively small, but the dark sunspot in the above image (taken in 2014) is more than 80,000 miles across—about ten times as wide as Earth's diameter. The presence of sunspots on the sun's surface is tied to the behavior of the star's magnetic field. NASA Goddard

In past work, researchers have assumed the magnetic field originates deep within the sun, somewhere around 130,000 miles beneath its surface. But the new study concluded the field’s origin is just 20,000 miles under the surface of the star.

To determine where the magnetic field begins, the researchers created models of the sun’s structure and ran them on a NASA supercomputer. They studied how small changes in the internal flow of plasma could lead to differences in the star’s magnetic field. When they modeled changes in the flow of plasma near the sun’s surface, the simulation produced magnetic structures in the same areas where sunspots truly occur, near the equator. Changes deeper in the sun, on the other hand, led to modeled fields near the sun’s poles, where they typically don’t occur in reality.

“Our work provides strong evidence that the solar cycle starts near the surface of the sun in the equatorial region,” Lecoanet tells Inverse’s Kiona Smith.

This conclusion goes against scientists’ conventional thoughts about the sun’s magnetic field. In the editorial, Zweibel calls the modeling “highly simplistic.”

“This is far from the final word on the problem,” says Steven Balbus, an astronomer at Oxford University in England who was not involved with the study, to MIT News’ Jennifer Chu. “However, it is a fresh and very promising avenue for further study... When the received wisdom has not been very fruitful for an extended period, something more creative is indicated, and that is what this work offers.”

Vasil tells New Scientist’s Leah Crane that it could be easier to predict the sun’s activity and study the magnetic field if it is closer to the surface. “If the magnetic fields are sitting there, then there is the most hope for actually being able to study them.”

Previous models have been unable to predict the strength of the next solar cycle. But with this information, the researchers hope they can. “We want to forecast if the next solar cycle will be particularly strong, or maybe weaker than normal,” Lecoanet tells Inverse.

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