Diagram of the Sun’s magnetic field
NASA/SDO/AIA/LMSAL
The Sun’s magnetic field may not be as deep as we thought. For decades, scientists thought the Sun’s dynamo (the part that generates its powerful magnetic field) was located far inside the Sun. Now, evidence suggests that the dynamo lurks just below the Sun’s surface.
The strength of the sun’s magnetic field fluctuates on an 11-year cycle. At its strongest, the cycle produces sunspots and powerful winds near the sun’s equator, as well as the outpouring of material that causes Earth’s aurora borealis. Ideas about how the magnetic field is generated have struggled to explain how all these phenomena are connected.
Essentially, he says, the sun behaves like a giant clock, with the many swirls and currents of plasma within it acting as gears to make it go. Jeffrey Vasil Researchers from the University of Edinburgh in the UK say: “No one really knows how these elements fit together, or what they are all about, unless we know how a clock starts. “I can’t explain the whole watch.”
Vassil and his colleagues suggest that the sun’s magnetic field may arise from rotational instabilities in the plasma inside the star, which may be caused by other sources, such as a disk of hot material orbiting a black hole. This phenomenon is also commonly observed in astrophysical objects. Such instability can occur in the Sun’s outermost 5 to 10 percent.
The researchers modeled how this instability stirs up the plasma that makes up the sun’s outer layers. The researchers found that sunspots can occur during periods of maximum solar activity, creating powerful winds that blow around the sun. Other magnetic phenomena were also discovered. Simulations using dynamos near the surface matched the observed magnetic patterns on the Sun better than simulations using deep dynamos.
“There are a lot of clues, and we’ve been piecing these together for nearly 20 years,” Vasil said. “It’s very satisfying to see so many things fall into place and make sense.”
If the sun’s dynamo were generated close to the surface, it could make it much easier to study the sun’s magnetic field and predict its behavior. “The best hope is that if the magnetic field is there, we can actually study it,” Vasil says.
This could help better predict the solar activity that produces spectacular aurora borealis and disrupts the Earth’s power grid.
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