Sun's magnetic field originates closer to surface, suggests new study

Researchers have found that the Sun's magnetic field, which triggers solar storms like the recent one that produced auroras on Earth, may originate at shallower depths within the Sun's interior than previously believed.

The Sun's outer 30% is composed of a turbulent "ocean" of churning gases extending over 130,000 miles (210,000 km) below its surface.

This new study, which compares recent theoretical models to observations by the SOHO spacecraft, indicates that the Sun's magnetic field is likely generated near the top of this turbulent zone, within 20,000 miles (32,000 km) from the surface, instead of near the bottom as previously thought.

Understanding the precise location of the magnetic field's origin can enhance predictions of solar storms and help mitigate potential disruptions to electricity grids, radio communications, and satellites.

Most stars, including the Sun, have magnetic fields generated by the movement of super-hot gases inside them. The Sun's magnetic field causes the formation of sunspots, which are shifting dark patches on its surface, and triggers solar flares that eject hot, charged particles into space.

"The top 5% to 10% of the sun is a region where the winds are perfect for making abundant magnetic fields through a fascinating astrophysical process," said Geoffrey Vasil, an applied and computational mathematician at the University of Edinburgh and the lead author of the study published in the journal Nature.

This process involves rotational flow patterns of super-hot ionized gases, called plasma, inside the Sun. The exact mechanisms of how the Sun generates its magnetic field, known as the solar dynamo, remain unresolved. Researchers hypothesize that these flow patterns are crucial to the process.

"If the plasma which constitutes the sun was completely stationary, we know the sun's magnetic field would decay in time, and before long, there would be no sunspots or other solar activity. However, the plasma in the sun is moving around, and that motion is able to regenerate and maintain the sun's magnetic field," explained Daniel Lecoanet, a theoretical physicist and study co-author from Northwestern University.

The solar magnetic field follows a distinct pattern, with sunspots appearing and disappearing every 11 years, making the Sun "a giant magnetic clock," according to Vasil. However, the full details of this process remain elusive.

Italian polymath Galileo made the first detailed observations of sunspots in 1612 using telescopes he invented, and American astronomer George Hale discovered in the early 20th century that sunspots were magnetic. Despite these historical advancements, researchers continue to investigate the complexities of sunspots and the solar magnetic field.

A recent strong solar storm caused vivid auroras visible from Earth but did not harm technological infrastructure. "Occasionally, a group of sunspots explodes and launches a billion tons of hot charged particles toward Earth, like what happened last week," Vasil noted.

However, a powerful solar storm similar to the 1859 Carrington Event could cause extensive damage, potentially costing trillions of dollars and affecting hundreds of millions of people.

"You can think of magnetic fields as being like rubber bands. The motions near the surface of the sun can stretch out the rubber bands until they break. The breaking magnetic field can then launch material outward into space in what is called a solar storm. If we're unlucky, these storms can be launched toward the Earth and can cause significant damage to our satellites and power grid," Lecoanet added.