Possible Origin of Sun’s Magnetic Field Proposed to Be Closer to Solar Surface
WASHINGTON—The sun’s magnetic field, responsible for solar storms like the recent one that created dazzling auroras on Earth, may originate closer to the surface of the star than previously believed, according to researchers.
The sun’s outer layer, covering about 30% of its structure, consists of a turbulent “ocean” of gases diving over 130,000 miles (210,000 km) beneath its surface. Their study, comparing new theoretical models with observations from the sun-watching SOHO spacecraft, strongly suggests that the magnetic field is generated near the top of this layer—within just 5% inward, roughly 20,000 miles (32,000 km)—rather than near the bottom, as previously thought.
Aside from shedding light on the sun’s dynamic activities, these findings could enhance the ability to predict solar storms and safeguard against potential harm to electricity grids, radio communications, and orbiting satellites, the researchers noted.
Most stars have magnetic fields, generated by the movement of extremely hot gases inside them. The sun’s fluctuating magnetic field leads to the formation of sunspots—shifting dark regions—on its surface and initiates solar flares that eject hot charged particles into space.
“The upper 5% to 10% of the sun experiences ideal conditions for producing abundant magnetic fields through a fascinating astrophysical process,” stated Geoffrey Vasil, a mathematics researcher at the University of Edinburgh in Scotland and the lead author of the study published in the journal Nature on Wednesday.
This process involves rotational flow patterns of super-hot ionized gases known as plasma within the sun.
Related Stories
The specific mechanisms behind how the sun generates its magnetic field—the solar dynamo, as scientists refer to it—have remained a puzzle in theoretical physics. These researchers propose that these flow patterns play a crucial role.
“If the plasma that makes up the sun were completely still, the sun’s magnetic field would diminish over time, leading to the absence of sunspots and other solar activities. However, the plasma within the sun is in motion, and this movement is capable of sustaining and generating the sun’s magnetic field,” explained Daniel Lecoanet, a theoretical physicist at Northwestern University in Illinois and a co-author of the study.
The solar magnetic field undergoes a cyclical pattern, with sunspots—regions possessing strong magnetic fields—emerging and disappearing every 11 years, turning the sun, as Vasil described it, into “a massive magnetic timepiece.”
“Yet, we have not unraveled the complete story behind this process. Complicated fluid motions (in this instance, the solar plasma) ultimately drive a dynamo, but we have not yet deciphered the specifics,” Vasil added.
In 1612, the Italian polymath Galileo conducted the first detailed observations of sunspots using telescopes he invented. In the early 20th century, American astronomer George Hale established that sunspots were magnetic.
“And we’re still trying to understand the mysteries of these pesky sunspots,” Vasil remarked.
A powerful solar storm reaching Earth recently resulted in vibrant auroras in the sky, while Earth’s technological infrastructure remained intact.
“Occasionally, a cluster of sunspots erupts, sending a billion tons of hot charged particles towards Earth, as occurred last week,” Vasil stated.
However, a severe solar storm, such as the Carrington Event in 1859, could inflict trillions of dollars in damage and leave hundreds of millions of individuals without power, the researchers warned.
“You can liken magnetic fields to rubber bands. The movements near the sun’s surface can stretch these rubber bands until they snap. The ruptured magnetic field can then propel material outward into space in what is known as a solar storm. If we’re unlucky, these storms could be directed towards Earth, causing significant harm to our satellites and power grid,” Lecoanet elaborated.
By Will Dunham
