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"Long before it's in the papers"
August 03, 2010


Scientists develop method to view Sun’s far side

March 15, 2006
Courtesy Stanford University 
and World Science staff

Researchers say they have developed a technique that makes the Sun’s hidden face, its far side, fully visible for the first time.

(Courtesy NOAA)

The new technology allows anyone with a computer to download images of the whole solar surface, the scientists say. 

This would be useful because potentially damaging solar storms that form on the far side could be detected days or weeks before they wreak havoc on Earth. 

“Sunspots, solar flares and other active regions on the surface of the sun emit radiation that can interfere with orbiting satellites, telecommunications and power transmission,” said Philip Scherrer, a physicist at Stanford University in Stanford, Calif. 

“This new method allows more reliable warning of magnetic storms brewing on the far side that could rotate with the sun and threaten the Earth.” 

It takes about 27 days for the sun to rotate on its axis. Stormy activity that forms on the far side can remain hidden for almost two weeks, surprising Earth-bound observers when it finally rotates into view and starts to affect us.

That’s what happened in October 2003, Scherrer said, when active regions from the back side suddenly appeared on the eastern edge, spewing X-rays, ultraviolet radiation and high-energy particles into space. 

Scherrer and colleagues study the sun using data from the Solar and Heliospheric Observatory, a satellite launched in 1995 by NASA and the European Space Agency. On board is an instrument that creates images of the sun’s interior by measuring the speed of sound waves produced by hot, bubbling gases that well up to the surface. The technique is called acoustic helioseismology. 

It’s “the same principle as medical ultrasound, which can create an image of a fetus inside a pregnant woman,” Scherrer explained. 

Positioned about 1 million miles above Earth, the satellite always faces the sun’s visible front side. In 2000 and 2001, scientists developed two techniques based on this principle that resulted in the first pictures of the sun’s back side, Scherrer explained. But both had limitations. One only produced images near the center of the far side; the other was restricted to views at the edges. 

To get a complete image, researchers would have to combine both methods, but that proved to be a major problem. 

Scherrer’s team said it overcame that last summer with a new computer program developed with Kenneth Oslund, an undergraduate at the California Institute of Technology. Their work resulted in the MDI Farside Graphics Viewer, which displays the first full images of the far side of the sun. The viewer is available online at 

“This new method is a vast improvement,” Scherrer said. “It should be especially important during the next solar maximum, which should begin in 2011, when solar activity will be at its peak.” 

He noted that during the last “solar max,” a peak period in a regular cycle of solar storms, which lasted from 2000 to 2003, these storms knocked out power in parts of northern Sweden and Canada. The storms also destroyed a satellite used to verify credit card payments at U.S. gas stations. 

Air transportation also can be disrupted when solar radiation interferes with satellites. 

“Our goal is to give pilots and air traffic controllers a day or two notice of a possible solar event,” Scherrer said, adding that missions to other planets also can be affected by solar storms. 

Last week, researchers at the National Center for Atmospheric Research in Colorado released new computer models predicting that the next solar cycle will be 30 to 50 percent stronger than last time.

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