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DAN ELLIOTT, Associated Press Writer BOULDER, Colo. (AP) ― The sun may finally be awakening from its longest
quiet period in about a century and powering up to solar maximum, when
it could fling disruptive electromagnetic storms toward Earth.
But once the sun does ramp up, it could be a relatively quiet solar
maximum, with a below-average number of eruptions, scientists say. Some researchers argue the sun has begun to enter solar maximum; others
say it's not there yet. They do agree the current quiet period, or solar
minimum, is the longest since the early 1900s, but they don't know why. "For the average person or for a technological society like ours, a
hundred years is a pretty long time," said Dan Baker, director of the
Laboratory for Atmospheric and Space Physics at the University of Colorado. A solar cycle usually lasts about 11 years, measured from one low point
to the next. The most recent started about 13 years ago, in 1996. Scientists won't declare the quiet period over until after a sustained
stretch of activity, generally about three months, said Frank Eparvier,
a scientist at the space physics lab. "We've increased a little bit and had some strong active regions,"
Eparvier said, but it hasn't been long enough to say solar maximum has
begun. The sun goes through fairly regular cycles of more and fewer eruptions,
averaging as many as 180 per day during solar maximum and dipping as low
as zero per day during solar minimum. The magnetic fields that cause the eruptions are themselves influenced
by a mix of internal solar motions, including rotation, shears,
turbulence and global circulation similar to Earth's ocean currents. Sarah Gibson, a scientist with the High Altitude Observatory at the
National Center for Atmospheric Research in Boulder, calls it "a
delicate mix of ordered and chaotic processes." The consensus prediction for the next solar maximum is a small one,
averaging about 90 or fewer sunspots a day in 2013, Eparvier said. A panel of scientists convened by NASA, the National Oceanic and
Atmospheric Administration and the International Space Environment
Service reviewed more than 100 published forecasts and eventually
coalesced around the small-maximum prediction. Solar eruptions can send billions of tons of magnetically charged
particles into space at high speed. If those particle clouds, called
plasma, collide with the Earth's magnetic field, they can create
dramatic effects ranging from a beautiful aurora borealis to a
devastating electrical blackout. The sun's volatile magnetic fields can become so severely twisted that
they snap and then reconnect, producing a flash called a solar flare and
a plasma eruption, Gibson said. If the plasma's magnetic field collides
with the Earth's own magnetic field, they connect with another powerful
snap. That can add electrical current on power lines, overtax transformers and
set off a rapid collapse of parts of the power grid. It can disrupt
radio signals, cause Global Positioning System devices to be off by the
distance of a football field and cut off communication between ground
controllers and jetliners flying over polar regions. That forces
airlines to send planes on longer routes that take more time and burn
more fuel. United Airlines diverted 26 flights from their normal polar routes in
January 2005 to avoid communications blackouts during solar storms. In March 1989, a geomagnetic storm triggered the collapse of a power
grid in Quebec, leaving an estimated 6 million people without
electricity for nine hours. And in 2006, a burst of solar radiation
disoriented virtually all GPS receivers on the lighted half of the
Earth, the National Weather Service said. Baker said radiation from solar flares could be harmful to space
travelers and even airline crews who are repeatedly exposed to it on
flights over the Earth's poles. Solar plasma can also physically compress the Earth's magnetic field so
much that it's smaller than the orbit of some satellites. Without that
magnetic field to orient themselves, those satellites can have trouble
communicating with ground stations. Baker estimated that $200 billion
worth of satellites are in orbits that leave them vulnerable to such
disruptions. Some satellites are more vulnerable to radiation damage than previous
models. During the Cold War, many satellites were "hardened" against
enemy radiation attacks, but when that threat passed, designers took
fewer protective measures.
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