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September 14, 2009

Sunspots Revealed

Supercomputer models help researchers solve mysteries of sunspots

Sunspots have fascinated mankind right from their first detection. Their mere existence challenged science and philosophy when it was recognized that the sun, once believed to be pure and unchanging, was indeed not.

Now, state-of-the art telescopes, combined with the muscle of a supercomputer called "Bluefire," are allowing scientists to come to a physics understanding of sunspots and to accurately model their structure and dynamics.

"Sunspots are the manifestation of very strong magnetic fields at the solar surface," said Michael Knölker, the director of the High Altitude Observatory at the National Center for Atmospheric Research (NCAR) in Boulder, Colo. "They are cooler than their surroundings. This is why we see them as dark spots on an otherwise much brighter solar disc."

Knölker and Matthias Rempel, both astrophysicists, are developing new computer models of sunspots with funding from the National Science Foundation (NSF).

Unanswered Questions

"Studying sunspots is extremely important for understanding how stars, like the sun, produce magnetic fields, which is still one of the big outstanding unanswered questions in stellar astrophysics," said Rempel.

Scientists know sunspot activity waxes and wanes on an 11-year cycle. Sunspots are associated with the release of solar flares and coronal mass ejections--events in which a massive cloud of charged particles erupts from the sun and washes out across the solar system.

"In a slow release process, slow at the beginning, a magnetic bubble pops off out of the solar atmosphere, is then accelerated very quickly and then drifts into interplanetary space," said Knölker.

Geomagnetic storms are triggered when charged particles from that bubble hit the Earth's magnetic field-- which envelops the planet like a cocoon, extending out into space.

Impacts on Earth

"With that disturbance come disruptions of short-wave radio communications, radiation exposure for astronauts and satellites in orbit, and other consequences that in modern society we are very concerned about," said Knölker.

The power grid of the U.S. and Canada is also particularly vulnerable, as more 'juice' zapping through the atmosphere can overload transformers. Maybe the only good thing about a geomagnetic storm is that it lights up the auroras, putting on a spectacular light show.

"That is the beautiful side of a geomagnetic storm and it has drawn the attention of humans since the beginning of human consciousness, we believe," said Knölker.

A flood of new data from solar telescopes, like the orbiting Japanese Hinode satellite, is helping scientists perfect their sunspot models, including what's going on inside the sun.

Seeing inside the sun

"When we do a numerical simulation, one of the main reasons we want to do it is to make the connection between what we can observe at the surface and the motions of ionized gas in the layers beneath, several thousand of kilometers beneath the surface," said Rempel.

Better understanding of sunspots also will help scientists sort out the role solar cycles play in climate change on Earth. Knölker believes what we are observing in terms of climate change over the past 30 years should clearly be chalked up to human activity. But he says there is no doubt that the sun is also playing a role over time.

"There cannot be any doubt that this research area has an obligation to humanity to pin down to what extent the solar activity variations play a role in climate," said Knölker.

And ultimately, a deeper grasp of the working of our own star will help scientists and others as we look beyond our solar system for Earth-like planets elsewhere in the cosmos. Those as-yet-unseen pale blue dots are orbiting their own suns. The more we know about our own solar system, the better prepared we'll be to understand others.

Miles O'Brien, Science Nation Correspondent
Kate Tobin, Science Nation Producer

Any opinions, findings, conclusions or recommendations presented in this material are only those of the presenter grantee/researcher, author, or agency employee; and do not necessarily reflect the views of the National Science Foundation.