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Fri Apr 24 06:07:35 CDT 2009


At the annual Space Weather Workshop held in Boulder, Colorado last
month <>, an international panel
of experts led by NOAA's Space Weather Prediction Center (SWPC)
predicted that Solar Cycle 24 will peak in May 2013 with 90 sunspots per
day on average. If the prediction proves true, Solar Cycle 24 will be
the weakest cycle since Solar Cycle 16, which peaked with 78 daily
sunspots in 1928, and ninth weakest since the 1750s, when numbered
cycles began.

The panel predicted that the lowest sunspot number between cycles -- the
solar minimum -- occurred in December 2008, marking the end of Solar
Cycle 23 and the start of Solar Cycle 24. If December's prediction holds
up <>, at 12 years and
seven months Solar Cycle 23 will be the longest since 1823 and the third
longest since 1755. Solar cycles span 11 years on average, from minimum
to minimum.

An unusually long, deep lull in sunspots led the panel to revise its
2007 prediction that the next cycle of solar storms would start in March
2008 and peak in late 2011 or mid-2012. The persistence of a quiet sun
also led the panel to a consensus that Solar Cycle 24 will be what they
called "moderately weak."

Although the peak is still four years away, a new active period of
Earth-threatening solar storms will be the weakest since 1928. Despite
the prediction, the scientists said that Earth is still vulnerable to a
severe solar storm. Solar storms are eruptions of energy and matter that
escape from the Sun and may head toward Earth, where even a weak storm
can damage satellites and power grids, disrupting communications, the
electric power supply and GPS. A single strong blast of "solar wind" can
threaten national security, transportation, financial services and other
essential functions.

The most common measure of a solar cycle's intensity is the number of
sunspots -- Earth-sized blotches on the sun marking areas of heightened
magnetic activity. The more sunspots there are, the more likely it is
that solar storms will occur, but a major storm can occur at any time.

"As with hurricanes, whether a cycle is active or weak refers to the
number of storms, but everyone needs to remember it only takes one
powerful storm to cause huge problems," said NOAA scientist Doug
Biesecker, who chaired the panel. "The strongest solar storm on record
occurred in 1859 during another below-average cycle." The 1859 storm
shorted out telegraph wires, causing fires in North America and Europe
and sent readings of Earth's magnetic field soaring. It also produced
northern lights so bright that people read newspapers by their light, he

Biesecker cited a recent report by the National Academy of Sciences that
found if a storm that severe occurred today, it could cause $1-2
trillion in damages the first year and require four to 10 years for
recovery, compared to the $80-125 billion of damage that resulted from
Hurricane Katrina

The Space Weather Prediction Center is part of the National Weather
Service and is one of the nine National Centers for Environmental
Prediction. It is the nation's official source of space weather alerts,
watches and warnings. SWPC provides real-time monitoring and forecasting
of solar and geophysical events that impact satellites, power grids,
communications, navigation and many other technological systems.

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