Supercomputer predicts shape of Sun's corona

Space 26 June 2006

New Scientist Default Image
The alignment of magnetic fields (coloured lines) in the corona dictates whether or not a solar eruption will lead to a dangerous magnetic storm around Earth

(Image: Z Mikic/Science Applications Intl)

New Scientist Default Image
Million-degree gas emits an X-ray glow in this simulated view of the Sun

(Image: Z Mikic/Science Applications Intl)

The state of the Sun’s atmosphere has been predicted with unprecedented accuracy five days in advance, using some of the world’s fastest computers. The simulation lays the foundation for better forecasts of hazardous magnetic storms around Earth.


Clouds of gas that escape from the Sun in events called coronal mass ejections (CMEs) can fry satellites and knock out power grids on Earth. The storms also pose a radiation hazard to astronauts.

But predicting these storms is difficult – not every CME that heads our way triggers a storm. The key factor appears to be the alignment of the cloud’s magnetic field. If it is lined up with Earth’s magnetic field, the local space weather is likely to be calm, while if it is lined up the opposite way, powerful magnetic storms can result.

The US National Oceanic and Atmospheric Administration issues forecasts of potential magnetic storms based on the interpretation of satellite data, but these are far from perfect.

Magnetic activity

Now, researchers led by Zoran Mikic of the company Science Applications International in San Diego, California, US, have devised a sophisticated computer model based on observations of magnetic activity on the Sun’s surface, or photosphere. This activity shapes the Sun’s wispy outer atmosphere, or corona, where the eruptions of gas originate.

They improved on simpler versions of their model by including a more accurate simulation of how energy flows through the corona. The new model worked well enough to successfully predict the shape of the entire corona when it became visible in the solar eclipse of 29 March 2006. Normally, the Sun’s surface is too bright to directly observe the corona.

“That’s a very good match,” agrees Mausumi Dikpati of the National Center for Atmospheric Research, in Boulder, US, who was not on the team. “Their model is so far the best.”

Despite the successful prediction of the corona’s appearance, Mikic says it will probably be a decade or more before space weather – and individual CMEs – can be routinely predicted using a computer model of the Sun.

Global structure

Still, their work will help pave the way for these predictions. That is because the alignment of CME magnetic fields depends on the physical state of the corona, which they have modelled.

“This kind of model we are describing could possibly do a better job in predicting how things reach the Earth,” Mikic told New Scientist. “Eventually these types of models could be used to tell if they’re going to hit the Earth or pass us by – and if they hit the Earth, what they will do.”

The model could also lead to a deeper understanding of the Sun, such as how its powerful magnetic field is generated. “If we understand global coronal structure and evolution it may give us clues to what is going on inside the Sun,” Dikpati told New Scientist.

The calculations were performed on supercomputers at NASA’s Ames Research Center and the San Diego Supercomputer Center, both in California, US.