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August 15, 2006: On July 31st, a tiny sunspot
was born. It popped up from the sun's interior, floated around
a bit, and vanished again in a few hours. On the sun this sort
of thing happens all the time and, ordinarily, it wouldn't be
worth mentioning. But this sunspot was special: It was backward.
 "We've
been waiting for this," says David Hathaway, a solar
physicist at the Marshall Space Flight in Huntsville, Alabama.
"A backward sunspot is a sign that the next solar cycle
is beginning."
Right:
The tiny, backward sunspot of July 31, 2006. Credit: SOHO.
[Larger
image]
"Backward"
means magnetically backward. Hathaway explains:
Sunspots
are planet-sized magnets created by the sun's inner magnetic
dynamo. Like all magnets in the Universe, sunspots have north
(N) and south (S) magnetic poles. The sunspot of July 31st
popped up at solar longitude 65o W, latitude 13o
S. Sunspots in that area are normally oriented N-S. The newcomer,
however, was S-N, opposite the norm.
A
picture is worth a 1000 words. In the magnetic map of the
sun, below, N is white and S is black. The backward sunspot
is circled:
Above: A SOHO magnetogram of the sun. July
31, 2006.
This
tiny spot of backwardness matters because of what it might
foretell: A really big solar cycle.
Solar
activity rises and falls in 11-year cycles, swinging back
and forth between times of quiet and storminess. Right now
the sun is quiet. "We're near the end of Solar Cycle
23, which peaked way back in 2001," explains Hathaway.
The next cycle, Solar Cycle 24, should begin "any time
now," returning the sun to a stormy state.
Satellite
operators and NASA mission planners are bracing for this next
solar cycle because it is expected to be exceptionally stormy,
perhaps the stormiest in decades. Sunspots and solar flares
will return in abundance, producing bright auroras on Earth
and dangerous proton storms in space: full
story.
 But
when will Solar Cycle 24 begin?
"Maybe
it already did--on July 31st," says Hathaway. The first
spot of a new solar cycle is always backwards. Solar physicists
have long known that sunspot magnetic fields reverse polarity
from cycle to cycle. N-S becomes S-N and vice versa. "The
backward sunspot may be the first sunspot of Cycle 24."
It
sounds exciting, but Hathaway is cautious on several fronts:
First,
the sunspot lasted only three hours. Typically, sunspots last
days, weeks or even months. Three hours is fleeting in the
extreme. "It came and went so fast, it was not given
an official sunspot number," says Hathaway. The astronomers
who number sunspots didn't think it worthy!
Second,
the latitude of the spot is suspicious. New-cycle sunspots
almost always pop up at mid-latitudes, around 30o
N or 30o S. The backward sunspot popped up at 13o
S. "That's strange."
These
odd-isms stop Hathaway short of declaring the onset of a new
solar cycle. "But it looks promising," he says.
Even
if Cycle 24 has truly begun, "don't expect any great
storms right away." Solar cycles last 11 years and take
time to build up to fever pitch. For a while, perhaps one
or two years, Cycle 23 and Cycle 24 will actually share the
sun, making it a hodgepodge of backward and forward spots.
Eventually, Cycle 24 will take over completely; then the fireworks
will really begin.
Meanwhile,
Hathaway plans to keep an eye out for more backward sunspots.
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Author: Dr. Tony
Phillips | Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
| More
to the story... |
| In
the story, above, we explain that the July 31st sunspot
popped up with a magnetic polarity opposite its neighbors.
That's what made it "backwards." But there's
more to the story....
 Right:
Sunspots, like bar magnets, have north and south magnetic
poles.
On
the sun, there is a grand pattern of sunspot polarities.
In the sun's northern hemisphere, all spots are S-N.
In the southern hemisphere, all spots are N-S. This
is how it has been for the past 10+ years during Solar
Cycle 23. When Cycle 24 arrives, the grand pattern will
flip. Northern sunspots will become N-S while southern
sunspots will become S-N. This flipping action occurs
every time one cycle gives way to another; it's part
of Hale's
Law.
The
July 31st sunspot, with its S-N orientation, would have
fit right in if it had popped up in the sun's northern
hemisphere. All the spots around it would've been S-N,
too. Instead, it emerged in the southern hemisphere
where N-S has held sway for a decade. This made it backwards
and a harbinger of the next solar cycle.
Trivia:
The coordinates of the July 31st sunspot were 65 W,
13 S. It if had popped up at those coordinates on Earth,
it would have been in Bolivia, making it a "South
American" sunspot.
Solar
Storm Warning (Science@NASA) -- Researchers from
the University of Colorado believe the next solar cycle
(Solar Cycle 24) will be the most intense in 50 years.
The
Vision for Space Exploration
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