The most true-to-life computer simulation ever made of our sun’s multimillion-degree outer atmosphere, the corona, successfully predicted its actual appearance during the March 29 solar eclipse.

The research, funded by NASA and the National Science Foundation, marks the beginning of a new era in space weather prediction. “This confirms that computer models can describe the physics of the solar corona,” said Zoran Mikic of Science Applications International Corporation, San Diego, California. The research is presented today at the American Astronomical Society’s Solar Physics Division meeting in Durham, N.H, and is the subject of a joint SPD/NASA/NSF press teleconference at 1PM EDT Monday, 26-June-2006.

The turbulent corona is threaded with magnetic fields generated beneath the visible solar surface. The evolution of these magnetic fields causes violent eruptions and solar storms originating in the corona. Like a rubber band that’s been twisted too far, solar magnetic fields suddenly snap to a new shape, blasting billions of tons of plasma into space at millions of miles per hour as a Coronal Mass Ejection (CME), or exploding with the force of up to a billion one-megaton nuclear bombs as a solar flare. When directed at Earth, solar flares and CMEs can disrupt satellites, communications, and power systems.

By accurately simulating the behavior of the corona, scientists hope to eventually predict when it will produce flares and CMEs, just like the National Weather Service uses computer simulations of Earth’s atmosphere to predict when it will produce thunderstorms or hurricanes. Such predictions will be required to undertake the vision for space exploration, because radiation from flares and CMEs is hazardous to unprotected astronauts. A prediction will allow time for astronauts to take shelter in a radiation-shielded area. The new corona simulation is the beginning of that capability, according to the team. While it can predict the large-scale appearance of the corona, it can’t yet forecast smaller, local events like flares and CMEs.

The computer model was based on spacecraft observations of magnetic activity on the sun’s surface, which affects and shapes the corona above it. The observations were made with the Michelson Doppler Imager (MDI) instrument on the Solar and Heliospheric Observatory (SOHO) spacecraft. The SAIC team released simulated “photographs” of the March 29 eclipse 13 days and again 5 days before the eclipse.

During a total solar eclipse, the moon blocks direct light from the sun, so the much fainter corona is visible. This is the only time the corona is visible from Earth without special instruments, and it resembles a white, lacy veil surrounding the black disk of the moon. Because the corona is always changing, each eclipse looks different. Just as fashion designers stake their reputations on showing the right look on the runway, the team staked its reputation on the right look for the corona — the accuracy of the simulation. The simulated photographs closely resembled actual photos of the eclipse, “providing reassurance that the model may one day be able to predict space weather events,” said Mikic.

Previous simulations were based on simplified models, so the calculations could be completed in a reasonable time by computers available then. The new simulation is the first to base its calculations on the physics of how energy is transferred in the corona. It is the most physically accurate simulation of the sun’s outer atmosphere that has ever been performed. Even with today’s powerful computers, the calculations required four days to complete on about 700 computer processors. These machines are “massively parallel” supercomputers that use many processors simultaneously to solve a problem. The researchers used NASA’s Columbia supercomputer and the National Science Foundation’s Data Star supercomputer.

Since the physics of the corona is still not completely understood, the accuracy of the simulation will improve when our understanding of how energy flows through the corona improves. More detailed measurements of magnetic activity on the solar surface, like those expected from NASA’s Solar Dynamics Observatory mission, will also improve the accuracy of the simulation.

The team includes Mikic, Jon Linker, Pete Riley, Roberto Lionello, and Viacheslav Titov, all of SAIC. For photos, refer to:

http://www.nasa.gov/vision/universe/solarsystem/corona_telecon_multimedia.html

Teleconference information:

Date/time: 26-June-2006 1:00 pm EDT
Dial: 888-396-9926
Passcode: “SPACE WEATHER”

Contacts:

Craig DeForest
AAS/SPD Press Officer
cdeforest@spd.aas.org
303-641-5769

Bill Steigerwald / Nancy Neal-Jones
NASA Goddard Space Flight Center, Greenbelt, Md.
1-301 286 5017 / 1-302-286-0039
william.a.steigerwald@nasa.gov / nancy.n.neal@nasa.gov