Big Solar Flare Portends Sun's Return to Normal

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May 6, 2009
By Alexis Madrigal
Wired News

The sun has a new spot, and it could signal the long-awaited beginning of the next solar cycle.

Solar flares rise and fall on an 11-year cycle, and last year marked what scientists thought was the solar minimum. But through the beginning of 2009, the sun stayed unusually quiet. That changed yesterday, when a major sunspot appeared on the backside of the sun, where it was captured by NASA's STEREO instrument.

"This is the biggest event we've seen in a year or so," said Michael Kaiser, research scientist with the heliophysics division at NASA Goddard Space Flight Center. "Does this mean we're finished with the minimum or not? It's hard to say. This could be it. It's got us all excited."

People have been counting sunspots since Galileo first observed one in the early 17th century. Through the 28 cycles that have been well-documented, stretching from 1745 to today, the average cycle length has been 11 years, but shorter and longer cycles have been observed. (The polarity of solar storms also alternates, so technically, a full cycle is 22 years.)

For unknown reasons, the current solar minimum has lasted longer than normal.

"It's been a long solar minimum, the longest and deepest one through the last hundred years, but not out of the extreme ordinary," Kaiser said.

Sunspot activity causes magnetic storminess around Earth and is correlated with the total amount of energy we receive from the sun. That connection caused some speculation in the media about the implications of the extended solar minimum on climate change, like yesterday's FoxNews.com article, "Quiet Sun May Trigger Global Cooling."

If the new solar flare is indeed a sign of the resumption of the normal cycle, it should put all that to rest.

Kaiser is sure this sunspot is part of the new cycle because it appeared at about 30 degrees of latitude. This is typical early in the solar cycle when sunspots appear closer to the poles. Toward the solar minimum they show up closer to the equator. To date, a few minor sunspots have shown up in the higher latitudes, but none with the intensity or size of the new spots.

"We have seen a few events in the new cycle, but they've all been pretty timid compared to this one," Kaiser said. "In angular size, this one wasn't spectacularly big, but it was certainly pretty bright."

STEREO picked up the event around the backside of the sun, but it won't come fully into view from Earth until May 8. Still, solar photographers are already pointing their telescopes at the sun, hoping to catch a glimpse of the new event.

http://www.wired.com/wiredscience/2009/05/solarcycle/