Sun's Magnetic 'Heartbeat' Revealed

A simulation of magnetic fields at the time of solar maximum.

CREDIT: University of Montreal Solar Physics Research Group

A magnetic "solar heartbeat" beats deep in the sun's interior, generating energy that leads to solar flares and sunspots, according to new research.

A new supercomputer simulation, described in the April 4 edition of the journal Science, probes the sun's periodic magnetic field reversals.

Every 40 years, according to the model, the sun's zonal magnetic field bands switch their orientation, or polarity.

That cycle is about four times longer than the 11-year sunspot cycle that governs the level of solar activity. Being able to model such a regular, long-term process is remarkable, the scientists said.

The new research, led by the University of Montreal's Paul Charbonneau, describes work from both his research group and other, independent coalitions simulating the sun's interior.

Temperature variability on a model intended to approximate what goes on inside the sun.

CREDIT: University of Montreal Solar Physics Research Group

Dissipating turbulence
Modeling the sun has been a sticky problem for decades.

The first attempts in the 1980s captured only a rough approximation of the turbulence inside of the sun.

Turbulence, when it occurs, happens at both large and small scales.

The large scales are easy to simulate, but in the sun, a small feature only about tens of miles across is just as important in understanding how fluid propagates.

When energy from turbulence dissipates, the turbulence flows into smaller and smaller whirlpool shapes, called vortices.

You can see this for yourself, Charbonneau said, when swirling your hand in a full bathtub. The movement will produce a vortex in the water that will gradually break up into tinier ones that dissipate the energy.

On the sun, dissipation takes place at a scale of tens of yards. That's extremely minute, compared with the size of the sun, which is 1 million times larger than Earth. "There's no way we can capture that in a simulation," Charbonneau stated.

To approximate this process, scientists typically limit the resolution to about 6.2 miles (10 kilometers). This, however, creates an energy buildup in the simulation that will "blow up" the model before it can run for very long, Charbonneau said.