New Model of Plasma Motion could explain Sunspot Cycle

A new model of plasma motion could explain the 11-year cycle behind sunspots and several other previously mysterious properties of the sun, researchers report.





The authors created a model based on their previous work with fusion energy research. The model shows that a thin layer beneath the sun’s surface is key to many of the features we see from Earth, like sunspots, magnetic reversals, and solar flow, and comparisons with observations of the sun back the model up.

“The observational data are key to confirming our picture of how the sun functions,” Jarboe says.

In the new model, a thin layer of magnetic flux and plasma, or free-floating electrons, moves at different speeds on different parts of the sun. The difference in speed between the flows creates twists of magnetism, known as magnetic helicity, that are similar to what happens in some fusion reactor concepts.

“Every 11 years, the sun grows this layer until it’s too big to be stable, and then it sloughs off,” Jarboe says. Its departure exposes the lower layer of plasma moving in the opposite direction with a flipped magnetic field.

When the circuits in both hemispheres are moving at the same speed, more sunspots appear. When the circuits are different speeds, there is less sunspot activity. That mismatch, Jarboe says, may have happened during the decades of little sunspot activity known as 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 says.

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