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Solar Scientists Agree That the Sun's Recent Behavior Is Odd, but the Explanation Remains Elusive by John Matson
Friday, May 28th 2010, 4:42 AM EDT
Co2sceptic (Site Admin)
The most recent solar minimum was both long and pronounced. But why?

MIAMI—In very rough terms, the sun's activity ebbs and flows in an 11-year cycle, with flares, coronal mass ejections and other energetic phenomena peaking at what is called solar maximum and bottoming out at solar minimum. Sunspots, markers of magnetic activity on the sun's surface, provide a visual proxy to mark the cycle's evolution, appearing in droves at maximum and all but disappearing at minimum. But the behavior of our host star is not as predictable as all that—the most recent solar minimum was surprisingly deep and long, finally bottoming out around late 2008 or so.

Solar physicists here at the semiannual meeting of the American Astronomical Society this week offered a number of mechanisms to shed light on what has been happening on the sun of late, but conceded that the final answer—or more likely answers—remains opaque. Beyond scientific understanding, motivations for better solar weather forecasts include hopes to use them to safeguard against electrical grid disruptions, damage to Earth-orbiting satellites and threats to the health of space travelers posed by solar radiation flare-ups.

One researcher has looked for clues to solar weather in the meridional flow, which moves from the solar equator toward the poles, and which seems to change speed during the shifting solar cycle. Another looked at the solar "jet stream," a slow current that originates at solar mid-latitudes and pushes in a bifurcated stream toward both the equator and the poles. Another scientist examined the inner workings of the sun through the oscillation of sound waves propagating through the solar interior; yet another looked at magnetic maps to chart the shifting flux across the sun.

"I think we're almost in violent agreement that this is an interesting minimum," said David Hathaway of the NASA Marshall Space Flight Center in Huntsville, Ala. By several measures—geomagnetic activity, weakness of polar magnetic fields, flagging solar deflection of galactic cosmic rays—the minimum was the deepest on record, Hathaway said, although some of those records contain just a few cycles. Hathaway focused on shifting speeds of the meridional flow, finding that the flow was anomalously fast at the most recent minimum. But, speaking of heliophysics forecasting techniques in general, he cautioned against leaping to any conclusions based on small-number statistics. "We need to be careful about extending what we've seen in one or two cycles to all of them," he said.

Click source to read FULL report from John Matson.
Source Link: scientificamerican.com
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