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."
(bottom pic #1): The tiny, backward sunspot
of July 31, 2006. Credit: SOHO.
"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,
S-N, opposite the norm.
A picture is worth a 1000 words. In the magnetic map of the sun, (bottom
N is white and S is black. The backward sunspot is circled in this 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
Satellite operators and NASA mission planners are bracing for this next
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.
But when will Solar Cycle 24 begin?
"Maybe it already did (bottom pic #3)
-- 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.
Author: Dr. Tony Phillips | Production Editor:
Dr. Tony Phillips |
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....
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
in 50 years.