Sunspots appear听on the surface of Earth's听sun. (Credit: NASA/SDO)
Researchers at CU Boulder have discovered hints that humanity鈥檚 favorite star may have a dual personality, with intriguing discrepancies in its magnetic fields that could hold clues to the sun鈥檚 own 鈥渋nternal clock.鈥�
Physicists Loren Matilsky and Juri Toomre used a computer simulation of the sun鈥檚 interior as a means of capturing the inner roiling turmoil of the star. In the process, the team spotted something unexpected: On rare occasions, the sun鈥檚 internal dynamics may jolt out of their normal routines and switch to an alternate state鈥攂it like a superhero trading the cape and cowl for civilian clothes.
While the findings are only preliminary, Matilsky said, they may line up 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 to the processes that govern the sun鈥檚 internal clock鈥攁 cycle in which the sun switches from periods of high activity to low activity about once every 11 years.
鈥淲e don鈥檛 know what is setting the cycle period for the sun or why some cycles are more violent than others,鈥� said Matilsky, a graduate student at . 鈥淥ur ultimate goal is to map what we鈥檙e seeing in the model to the sun鈥檚 surface so that we can then make predictions.鈥�
He will present the team鈥檚 findings at a press briefing today at the in St. Louis.听
Digital sun
Computer simulations of the sun's dynamo over several hundred years. During "normal" solar cycles (top), that dynamo forms symmetrically in the sun's northern and southern hemispheres and moves steadily toward the equator, before resetting. In the "alternate" cycle (bottom), that dynamo forms strongly in one hemisphere over the other and then wanders for several years. (Credit: Loren Matilsky/Juri Toomre)
The study takes a deep look at a phenomenon that scientists call the solar 鈥渄ynamo,鈥� essentially a concentration of the star鈥檚 magnetic energy. This dynamo is formed by the spinning and twisting of the hot gases inside the sun and can have big impacts鈥攁n especially active solar dynamo can generate large numbers of sunspots and solar flares, or globs of energy that blast out from the surface.
But that dynamo isn鈥檛 easy to study, Matilsky said. That鈥檚 because it mainly forms and evolves within the sun鈥檚 interior, far out of range of most scientific instruments.
鈥淲e can鈥檛 dive into the interior, which makes the sun鈥檚 internal magnetism a few steps removed from real observations,鈥� he said.
To get around that limitation, many solar physicists use massive supercomputers to try to recreate what鈥檚 occurring inside the sun.
The simulation that Matilsky and Toomre adapted, using听software developed by Nicholas Featherstone of the CU Boulder Department of Applied Mathematics, examines activity in the outer third of that interior. Matilsky likens it to 鈥渁 spherical pot of boiling water.鈥�
And, he said, this model delivered some interesting results. When the researchers ran their simulation, they first found that the solar dynamo formed to the north and south of the sun鈥檚 equator. Following a regular cycle, that dynamo moved toward the equator and stopped, then reset in close agreement with actual observations of the sun.
Alter ego
But that regular churn wasn鈥檛 the whole picture. Roughly twice every 100 years, the simulated sun did something different.
In those strange cases, the solar dynamo didn鈥檛 follow that same cycle but, instead, clustered in one hemisphere over the other.
鈥淭hat additional dynamo cycle would kind of wander,鈥� Matilsky said. 鈥淚t would stay in one hemisphere over a few cycles, then move into the other one. Eventually, the solar dynamo would return to its original state.鈥�
That pattern could be a fluke of the model, Matilsky said, but it might also point to real, and previously unknown, behavior of the solar dynamo. He added that astronomers have, on rare occasions, seen sun spots congregating in one hemisphere of the sun more than the other, an observation that matches the CU Boulder team鈥檚 findings.
Matilsky said that the group will need to develop this model further to see if the dual dynamo pans out. But he said that the team鈥檚 results could, one day, help to explain the cause of the peaks and dips in the sun鈥檚 activity鈥攑atterns that have huge implications for climate and technological societies on Earth.
鈥淚t gives us clues to how the sun might shut off its dynamo and turn itself back on again,鈥� he said.
