By Maggie Fox
Health and Science Correspondent
 WASHINGTON
(Reuters) - The sun is hot right now -- spewing electromagnetic
radiation in the midst of its most interesting storm season ever,
scientists say.
But although
the plasma and high-energy particles are making the Earth's ionosphere
light up, orbiting detectors and other equipment have helped scientists
set up an early-warning system that seems to have helped, so far,
to keep satellites and power grids safe, the scientists at NASA
and other agencies said.
``This is
the most exciting solar cycle that we have had,'' Ernest Hildner
of the National Oceanic and Atmospheric Administration (NOAA)
in Boulder, Colorado, told a news conference Thursday.
The sun goes
through 11-year cycles of sunspot activity. These sunspots have
been watched for centuries but only recently did scientists learn
they are accompanied by ejections of hot electromagnetic plasma
from the sun.
The sunspots
are invisible to the naked eye -- except when they make the Aurora
Borealis light up in northern skies. And in the 20th century they
have knocked satellites off-line and shut down power grids.
The last big
event, in 1989, shut down Quebec's power grid, plunging 6 million
customers into darkness for a day.
NASA, NOAA
and other agencies rushed to set up an early-warning system, which
is working to some degree and providing very pretty pictures,
said George Withbroe, science director of NASA's Sun-Earth connection
program.
``Our predictions
are getting better but they are not perfect,'' he said.
Withbroe and
Hildner said power operators up and down North America's east
coast responded promptly to the latest solar burp this past July,
cutting output to avoid overloads, but still circuit breakers
tripped and transformers overheated.
Global Positioning
Systems (GPS), which use satellites to tell a user where he or
she is within a few feet, became much less accurate for several
hours -- which could spell disaster if one was ever used, for
instance, to land a plane.
``These are
dramatic events. They are not subtle at all and they are affecting
us in many different ways,'' solar physicist Craig DeForest of
the Southwest Research Institute in Boulder, Colorado, told the
news conference.
``They literally
are masses of coronal material that are thrown off the sun,''
added Nicola Fox of the International Solar Terrestrial Physics
Project at NASA's Goddard Space Flight Center in Maryland. ``They
take typically three days to reach us.''
The scientists
showed images of the event in mid-July of this year, which can
be seen on the Internet at http://www.gsfc.nasa.gov/GSFC/SpaceSci/sunearth/solarmax.htm.
The Advanced
Composition Explorer (ACE) spacecraft detects the shock waves,
the leading edges of the ejections that resemble the wave that
runs in front of a boat, giving about one hour's notice.
These slap
up against the magnetosphere, the magnetic barrier that surrounds
the Earth. ``It is like striking a bell. You get vibrations that
move up and down the whole magnetosphere,'' Fox said.
Then the Imager
for Magnetosphere to Aurora Global Exploration (IMAGE) satellite
catches pictures of the effect on the Earth's aurora, which literally
lights up. ``It is a very spectacular effect,'' Fox said.
The ``main
event'' that follows -- the blob of plasma from the sun -- is
what stresses power systems and can send satellites tumbling.
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