From the NASA Web page--Tom, WW5L
http://science.nasa.gov/headlines/y2006/10mar_stormwarning.htm?list801221
March 10, 2006: It's official: Solar minimum has arrived. Sunspots have
all but vanished. Solar flares are nonexistent. The sun is utterly quiet.
Like the quiet before a storm.
This week researchers announced that a storm is coming--the most intense
solar maximum in fifty years. The prediction comes from a team led by
Mausumi Dikpati of the National Center for Atmospheric Research (NCAR).
"The next sunspot cycle will be 30% to 50% stronger than the previous
one," she says. If correct, the years ahead could produce a burst of
solar activity second only to the historic Solar Max of 1958.
see caption
<http://www-istp.gsfc.nasa.gov/istp/outreach/auroras.html>That was a
solar maximum. The Space Age was just beginning: Sputnik was launched in
Oct. 1957 and Explorer 1 (the first US satellite) in Jan. 1958. In 1958
you couldn't tell that a solar storm was underway by looking at the bars
on your cell phone; cell phones didn't exist. Even so, people knew
something big was happening when Northern Lights were sighted three
times in Mexico. A similar maximum now would be noticed by its effect on
cell phones, GPS, weather satellites and many other modern technologies.
Right: Intense auroras over Fairbanks, Alaska, in 1958. [More
<http://www-istp.gsfc.nasa.gov/istp/outreach/auroras.html>]
Dikpati's prediction is unprecedented. In nearly-two centuries since the
11-year sunspot cycle was discovered, scientists have struggled to
predict the size of future maximaand failed. Solar maxima can be
intense, as in 1958, or barely detectable, as in 1805, obeying no
obvious pattern.
The key to the mystery, Dikpati realized years ago, is a conveyor belt
on the sun.
We have something similar here on Earththe Great Ocean Conveyor Belt,
popularized in the sci-fi movie The Day After Tomorrow. It is a network
of currents that carry water and heat from ocean to ocean--see the
diagram below. In the movie, the Conveyor Belt stopped and threw the
world's weather into chaos.
see caption <http://seis.natsci.csulb.edu/rbehl/ConvBelt.htm>
Above: Earth's "Great Ocean Conveyor Belt." [More
<http://seis.natsci.csulb.edu/rbehl/ConvBelt.htm>]
The sun's conveyor belt is a current, not of water, but of
electrically-conducting gas. It flows in a loop from the sun's equator
to the poles and back again. Just as the Great Ocean Conveyor Belt
controls weather on Earth, this solar conveyor belt controls weather on
the sun. Specifically, it controls the sunspot cycle.
Solar physicist David Hathaway of the National Space Science &
Technology Center (NSSTC) explains: "First, remember what sunspots
are--tangled knots of magnetism generated by the sun's inner dynamo. A
typical sunspot exists for just a few weeks. Then it decays, leaving
behind a 'corpse' of weak magnetic fields."
Enter the conveyor belt.
see caption
<http://science.nasa.gov/headlines/y2006/images/stormwarning/conveyorbelt.jpg>"The
top of the conveyor belt skims the surface of the sun, sweeping up the
magnetic fields of old, dead sunspots. The 'corpses' are dragged down at
the poles to a depth of 200,000 km where the sun's magnetic dynamo can
amplify them. Once the corpses (magnetic knots) are reincarnated
(amplified), they become buoyant and float back to the surface."
Prestonew sunspots!
Right: The sun's "great conveyor belt." [Larger image
<http://science.nasa.gov/headlines/y2006/images/stormwarning/conveyorbelt.jpg>]
All this happens with massive slowness. "It takes about 40 years for the
belt to complete one loop," says Hathaway. The speed varies "anywhere
from a 50-year pace (slow) to a 30-year pace (fast)."
When the belt is turning "fast," it means that lots of magnetic fields
are being swept up, and that a future sunspot cycle is going to be
intense. This is a basis for forecasting: "The belt was turning fast in
1986-1996," says Hathaway. "Old magnetic fields swept up then should
re-appear as big sunspots in 2010-2011."
Like most experts in the field, Hathaway has confidence in the conveyor
belt model and agrees with Dikpati that the next solar maximum should be
a doozy. But he disagrees with one point. Dikpati's forecast puts Solar
Max at 2012. Hathaway believes it will arrive sooner, in 2010 or 2011.
"History shows that big sunspot cycles 'ramp up' faster than small
ones," he says. "I expect to see the first sunspots of the next cycle
appear in late 2006 or 2007and Solar Max to be underway by 2010 or 2011."
Who's right? Time will tell. Either way, a storm is coming.
