Sun's Next Cycle of Fury Delayed

This succession of Sun images depicts our nearest star?s 11-year solar cycle. CREDIT: NOAA.

The Sun's next cycle of solar storms will brew up later than expected, though astronomers are split on just how strong the star's tempests will be.

Initially expected to begin last fall, the Sun's 11-year storm season is now pegged to begin in March 2008 and hit its peak near the end of 2011, according to a new forecast compiled by a panel of solar experts for the Space Weather Center at the National Oceanic and Atmospheric Administration (NOAA). The 12-member panel split into two equal camps, one predicting a weak season while the other expects a strong one, though both facets are not anticipating the Sun set any new records in coming years.

"By giving a long-term outlook, we're advancing a new field - space climate - that's still in its infancy," said retired U.S. Air Force Brig. Gen. David Johnson, director of NOAA's National Weather Service in Boulder, Colorado. "Issuing a cycle prediction of the onset this far in advance lies on the very edge of what we know about the Sun."

Sunspots, solar flares and intense explosions known as coronal mass ejections are hallmarks of the Sun's storm cycle, the latter two belching charged particles at such extreme intensities that they can interfere with satellite communications, power grids and Earth, and force astronauts in space to take shelter in reinforced areas of their vehicles such as the Russian segments of the International Space Station (ISS). The solar storms also amplify Earth's auroras, or the northern and southern lights, when their charged particles interact with the planet's magnetic field.

The Sun's solar cycle is measured by its maximum number of sunspots, blemishes that indicate cooler regions of strong magnetic activity. More sunspots hint at the greater likelihood of more major solar storms during a given season, though most cycles tend to range between about 75 and 155 sunspots, NOAA officials said.

One half of the Solar Cycle 24 panel predicted that the upcoming season could be moderately strong, peaking out with up to 140 sunspots, give or take 20, by October 2011. The panel's other faction, however, predicted a more serene 90-sunspot maximum, plus or minus 10, for Solar Cycle 24. Those estimates are expected to be refined the first year after the Sun's closing storm season, Solar Cycle 23, NOAA officials said.

"The panelists in each camp have clear views on why they believe in their prediction, why they might be wrong and what it would take to change their minds," said NOAA Space Environment Center scientist Douglas Biesecker, who chaired the panel, in a statement.

Biesecker said that despite the panel's division on the Sun cycle's intensity, all members have a high confidence that the season will begin in March 2008. They represent the third panel to predict an upcoming solar cycle, with previous incarnations meeting in 1989 and 1996. Included in the current panel's debate was the importance of the Sun's magnetic fields near its poles during the waning years of previous solar cycles, NOAA officials said.

"We're on the verge of understanding and agreeing on which precursors are the most important in predicting future solar activity," Biesecker added.

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