Sunspot Formation Explained by Solar Physicists

Sunspot Formation Explained by Solar Physicists
by Clarence Oxford
Los Angeles CA (SPX) May 23, 2024

A team of solar scientists has identified the origins of the mechanism driving the sun's activity and sunspots. The discovery may solve one of the oldest unsolved problems in physics.

The "solar dynamo" might start in the sun's outer layers rather than its interior, said Benjamin Brown, a solar physicist at CU Boulder. "Galileo first observed the sunspots 400 years ago...But he couldn't figure out where they came from," Brown said. "We've struggled with the question ever since."

Led by Geoffrey Vasil of the University of Edinburgh, the researchers published their findings May 22 in Nature. Co-authors include Keith Julien, an applied mathematician from CU Boulder who recently passed away.

The sun's dynamo generates its magnetic fields, influencing solar storms that can affect human technology and create auroras. This study represents a significant milestone. "Geoff Vasil and I have been thinking about these ideas ever since we were both grad students at CU Boulder 20 years ago," Brown said.

Scientists generally agree that the solar dynamo starts in the sun's "convection zone," where hot, charged plasma rises to the surface. Unlike Earth's mostly uniform magnetic field, the sun's magnetic field resembles a bowl of noodles. Despite this, the solar dynamo's behavior is predictable, cycling every 11 years. "You could practically set a calendar to the solar dynamo," Brown said. "How is it so wild yet also so orderly?"

In the 1990s, scientists theorized the dynamo originated deep within the sun. This study suggests it starts much closer to the surface. The researchers used computer simulations to show how a "magnetorotational instability" might drive the solar dynamo in the sun's outer layers. This process could explain the 11-year cycles and occurs within 20,000 miles of the surface.

The team's work honors Julien's legacy. Vasil reflected on their collaboration: "I recall first having a 'huh, that's funny' moment about the sun's near-surface instability one morning in 2004...Keith was the first person I literally ran to tell about it. He supported ideas and gave encouragement to a generation of young researchers...He was thrilled this work happened and was to be published in Nature."

Research Report:The solar dynamo begins near the surface