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How SOHO Watches The Far Side Of Sun
Greenbelt, Md. (SPX) March 9 NASA researchers using the Solar and Heliospheric Observatory spacecraft said they have developed a method of seeing through the Sun to its far side, which has not been directly observable in real time by conventional means. "This new method allows more reliable advance warning of magnetic storms brewing on the far side that could rotate with the Sun and threaten the Earth," said team member Phil Scherrer of Stanford University in California. Magnetic storms resulting from violent solar activity disrupt satellites, radio communications, power grids and other technological systems on Earth. Advance warning can help planners prepare for operational disruptions. The sun rotates once every 27 days, as seen from Earth, so growing storms on the star's far side previously have not been detectable. Many solar storms originate in groups of sunspots - areas with a high concentration of magnetic fields. Knowing whether there are large active regions on the opposite side of the Sun would greatly improve the ability to forecast potential magnetic storms that could endanger satellites and astronauts on the International Space Station or in orbit. The new observation method uses SOHO's Michelson Doppler Imager instrument to trace sound waves reverberating through the Sun to build a picture of the far side. The sun is filled with many kinds of sound waves caused by the convective motion of gas in its surface layers. The new imaging method compares the sound waves that emanate from each small region on the far side with what was expected to arrive at that region from waves originating on the near side. A sunspot-active region reveals itself because its strong magnetic fields speed up the sound waves. The difference becomes evident when sound waves originating from the front side and from the back side get out of step with one another. "The original far-side imaging method only allowed us to see the central regions, about one-quarter to one-third of its total area," Scherrer explained. "The new method allows us to see the entire far side, including the poles." Scherrer said he has started an effort to use the new method to create full far-side images from archived MDI data collected since 1996. The project was completed in December 2005. "With the new far side photo album going back to 1996, we can discover identifying characteristics of active regions," said Douglas Biesecker of the National Oceanic and Atmospheric Administration's Space Environment Center in Boulder, Colo. "This will improve our ability to distinguish real active regions." Related Links SOHO
Scientists Predict Big Sunspot Cycle Coming
Boulder CO (SPX) March 6, 2006Solar scientists said Monday the next sunspot cycle could be 30 percent to 50 percent stronger than the last one, and it could begin up to a year later than expected � although other scientists dispute the timing prediction. |
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