Astronomers say the Sun has begun its next cycle of activity, part of an 11-year ebb and flow in sunspots and solar flares.
Solar activity is near the low point in the cycle now. Few sunspots appear and solar flares are rare. But on July 31, a tiny sunspot appeared and then vanished after a few hours. It was a normal event, except that it was magnetically backward.
"We've been waiting for this," said David Hathaway, a solar physicist at the Marshall Space Flight in Huntsville, Alabama. "A backward sunspot is a sign that the next solar cycle is beginning."
Two lines of evidence
Sunspots are areas of strong magnetic activity, where material wells up from below. The dark spots are like tops on a soda bottle, and sometimes they erupt and send bubbles of superheated gas, called plasma, into space.
This sunspot had a south-north orientation in a region of the Sun where spots would normally be oriented north-south.
"We're near the end of Solar Cycle 23, which peaked way back in 2001," Hathaway said. Cycle 24 should begin "any time now," he said, adding that it might have begun on July 31.
The tiny, backward sunspot was at 13-degrees south latitude. Cycle-heralding sunspots are usually closer to the Sun's midsection, between 30 degrees North and 30 degrees South. So Hathaway is not certain the new cycle has begun. "But it looks promising," he said.
Another group of researchers today announced that the cycle had indeed begun. That team, using the Synoptic Optical Long-term Investigations of the Sun (SOLIS) facility built by the National Solar Observatory at Kitt Peak, Arizona, detected small magnetic eruptions near the Sun's poles that they say signal the new cycle's stars.
Storminess ahead
The peak of Cycle 23 was not particularly noteworthy, though a record-setting solar flare came as part of a string of storms struck our planet in November of 2003-actually well past the peak of the cycle.
Astronomers think Cycle 24 could be a strong one based on historical records and computer projections.
Enhanced activity means satellites and even power grids on Earth are at risk of electrical malfunction. Solar storms spew charged particles into space, and when they interact with Earth's protective magnetic field, electrical charges can dip into the lower atmosphere and even to the ground.
It will likely be many months and perhaps years before the new cycle builds steam and serious storminess ensues.
NASA plans later this month to launch a new pair of probes, called STEREO, to better monitor solar activity through the next cycle.
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