The sun can have a dual personality, suggest simulations

Researchers at CU Boulder have discovered clues that humanity's favorite star may have a dual personality, with intriguing divergences in its magnetic fields that may contain clues to the sun's own "internal clock".

Physicists Loren Matilsky and Juri Toomre have developed a computer simulation of the sun's interior in order to capture the inner turmoil of the star. During the process, the team spotted something unexpected: on rare occasions, the internal dynamics of the sun could come out of its usual routines and switch to another state, much like a superhero swapping cap and cap for civilian clothes.

Although the discoveries are only preliminary, said Matilsky, they could align with real observations of the sun dating back to the 19th century.

He added that the existence of such a solar alter-ego could provide physicists with new clues about the processes that govern the sun's internal clock – a cycle in which the sun rocks from the sun's ebb and flow. a period of high activity at low activity about every 11 years.

"We do not know what sets the cycle period for the sun nor why some cycles are more violent than others," said Matilsky, a JILA graduate student. "Our ultimate goal is to map what we see in the model with the sun's surface so we can then make predictions."

He will present the findings of the team at a press conference held today at the 234th meeting of the American Astronomical Society in St. Louis.

The study examines in depth a phenomenon that scientists call the "dynamo" solar, essentially a concentration of the magnetic energy of the star. This dynamo is formed by the rotation and twisting of hot gases inside the sun and can have great impacts: a particularly active solar dynamo can generate a large number of sunspots and solar flares, or of energy globes coming out of the surface.

But this dynamo is not easy to study, Matilsky said. Indeed, it is formed and evolves mainly inside the sun, far from the reach of most scientific instruments.

"We can not dive into the interior, which makes the internal magnetism of the sun far removed from some real observations," he said.

To get around this limitation, many solar physicists use massive supercomputers to try to recreate what's happening inside the sun.

The simulation of Matilsky and Toomre examines the activity in the outer third of this interior, what Matilsky likens to "a spherical pan of boiling water".

And, he said, this model has yielded interesting results. During the simulation, the researchers discovered that the solar dynamo had formed north and south of the solar equator. After a regular cycle, this dynamo is directed towards the equator and stopped, then reset in close agreement with the actual observations of the sun.

But this regular turnover did not make the whole situation. About twice every 100 years, the simulated sun did something different.

In these strange cases, the solar dynamo did not follow the same cycle but clustered in one hemisphere rather than in the other.

"This extra dynamo cycle would be sort of wandering," said Matilsky. "She would stay in one hemisphere for a few cycles, then go in. Finally, the solar dynamo would return to its original state."

This model could be a blow to the model's fate, said Matilsky, but it could also indicate a real, and previously unknown, behavior of the solar dynamo. He added that astronomers have, on rare occasions, seen sun spots gather in one hemisphere of the sun more than in the other, observation that corresponds to the findings of the CU Boulder team.

Matilsky said the group will have to develop its model further to see if the double dynamo emerges. But he said the team's findings could one day help explain the cause of peaks and troughs in the sun's activity – models that have huge implications for climate and societies on Earth.

"This gives us clues as to how the sun could shut down its dynamo and reignite itself," he said.

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