Why does the sun get sunspots? Scientists may finally know
The sun may be the focal point of our solar system, but astronomers are still trying to understand some strange processes that unfold on the star, including sunspots.
Sunspots show up like dark spots on the sun’s surface. And every 11 years, the number of sunspots peaks.
New research, rooted in fusion energy research, suggests that some of the sun’s unusual features that are visible to us through telescopes actually happen in a thin layer located under the sun’s surface. A study using this new model was published Thursday in the journal Physics of Plasmas.
This layer is made up of plasma, or free-floating electrons, and magnetic flux — the measurement of a magnetic field force in a specific area.
These things flow at different speeds, which creates magnetic twists. This behavior is not unlike what happens in a fusion reactor.
“Every 11 years, the sun grows this layer until it’s too big to be stable, and then it sloughs off,” said Thomas Jarboe, study author and a University of Washington professor of aeronautics and astronautics.
This causes the magnetic field to flip and causes the exposed layer of plasma to move in a different direction.
When the flows reach the same speed, more sunspots are observed. When the flows are at different speeds, fewer sunspots are seen. Researchers believe this is what has happened during times when fewer sunspots were observed, called the “Maunder Minimum.”
“If the two hemispheres rotate at different speeds, then the sunspots near the equator won’t match up, and the whole thing will die,” Jarboe said.
Scientists previously had a different understanding of how sunspots originated.
“Scientists had thought that a sunspot was generated down at 30% of the depth of the sun and then came up in a twisted rope of plasma that pops out,” Jarboe said.
In this new model, the researchers suggest that the sunspots form within “supergranules” dotting the thin layer. The thin layer is estimated to be between 100 to 300 miles thick, which is thin when compared with the sun’s 864,240-mile diameter.
“The sunspot is an amazing thing. There’s nothing there, and then all of a sudden, you see it in a flash,” Jarboe said.
Jarboe used a spheromak reactor to model sunspot behavior, which is a sphere containing electron plasma that can arrange itself into patterns. Previous observations of the sun have suggested similar activity happens there. Jarboe believes his theory can also explain the sun’s magnetic structure.
“For 100 years, people have been researching this,” Jarboe said. “Many of the features we’re seeing are below the resolution of the models, so we can only find them in calculations. My hope is that scientists will look at their data in a new light and the researchers who worked their whole lives to gather that data will have a new tool to understand what it all means.”