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Sunspot tracking could provide 2 days' advance warning of damaging solar flare

August 19, 2011 - Washington

Stanford researchers have developed a method that can predict disruptions such as solar flares and mass eruptions one or two days in advance so that protective measures could be taken to shield vulnerable electronics before solar storms strike.

Viewed from the technological perspective of modern humans, the Sun is a seething cauldron of disruptive influences that can wreak havoc on communication systems, air travel, power grids and satellites - not to mention astronauts in space.

Now, the researchers have developed a way to detect incipient sunspots as deep as 65,000 km inside the Sun, providing up to two days' advance warning of a damaging solar flare.

Sunspots develop in active solar regions of strong, concentrated magnetic fields and appear dark when they reach the surface of the Sun. Eruptions of the intense magnetic flux give rise to solar storms, but until now, no one has had luck in predicting them.

The key to the new method is using acoustic waves generated inside the Sun by the turbulent motion of plasma and gases in constant motion. In the near-surface region, small-scale convection cells - about the size of California - generate sound waves that travel to the interior of the Sun and are refracted back to the surface.

The researchers got help from the Michelson Doppler Imager aboard NASA's Solar and Heliospheric Observatory satellite, known as SOHO. The craft spent 15 years making detailed observations of the sound waves within the Sun. It was superseded in 2010 with the launch of NASA's Solar Dynamics Observatory satellite, which carries the Helioseismic and Magnetic Imager.

Using the masses of data generated by the two imagers, Stathis Ilonidis, a Stanford graduate student in physics, was able to develop a way to reduce the electronic clutter in the data so he could accurately measure the solar sounds.

The new method enabled Ilonidis to detect sunspots in the early stages of formation as deep as 65,000 kilometers inside the Sun. Between one and two days later, the sunspots would appear on the surface.

"Researchers have suspected for a long time that sunspot regions are generated in the deep solar interior, but until now the emergence of these regions through the convection zone to the surface had gone undetected," Ilonidis said.

"We have now successfully detected them four times and tracked them moving upward at speeds between 1,000 and 2,000 kilometers per hour."

The finding has been detailed in Science.


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