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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