Our Neighbor the Sun

The Sun is the energy source for the entire solar system, and it will continue to kick out energy for another five billion years. Since direct observation of the Sun's interior is impossible, however, scientists have an incomplete understanding of many solar processes -- including how the Sun's energy moves from the inner core to its outer layers.
Juri Toomre co-directs the National Science Foundation large-scale turbulence grand challenge research project with James McWilliams. While McWilliams investigates atmospheric turbulence, Toomre focuses on the Sun's outer layers, where continuous overturning of hot and cool gases creates turbulence.

"We're at the mercy of the Sun," says Toomre, an astrophysicist at the University of Colorado, Boulder. "If the Sun is magnetically active, it can blast holes in our communications. Or if the Sun floods us with high-energy particles as flares go off, it would heat our atmosphere significantly. Our civilization might stop if the Sun changed its output by 1 percent either way. You sure would like to know what's operating this machine."

Toomre and his colleagues have used the CRAY C90 at Pittsburgh Supercomputing Center to simulate gas movement and energy transfer in the Sun's outer regions. These computations have revealed details about turbulence in these regions that otherwise can't be observed, and they have helped to reconcile observations with theory.

Vertical Velocity in the Convection Zone
This three-dimensional volume from simulations by Toomre and his colleague, post-doctoral research associate Nic Brummell, shows vertical velocity within the convection zone. The relatively calm granular pattern of convection cells at the surface disguises the highly turbulent interior. Dark colors represent cool, downflowing gas, and light areas are warm and upflowing.

Vorticity in the Convection Zone
This computational box represents one instant in time from simulation of the turbulent convection zone. The enstrophy, or vorticity squared, is shown as a colored region, where each value is assigned an opacity and color according to the field's intensity. While strong enstrophy is brightly colored (yellow) and opaque, weak enstrophy is dark (purple) and translucent. Distinctive vortices are present, with sheets and tubes of vortices near the top of the convection zone evolving into convection cells. In the intense turbulence at greater depths, the vortices are less organized.

Researchers: Juri Toomre and Nic Brummell, University of Colorado, Boulder.
Hardware: CRAY Y-MP C90
Software: User developed code.
Keywords: sun, solar turbulence, solar convection, astrophysics, turbulent convection.

Related Material on the Web:
Scientific papers, graphics and video animations related to this research project.
Related research: Turbulent Earth
Projects in Scientific Computing, PSC's annual research report.

References, Acknowledgements & Credits