-->Expected Solar Fireworks Could Disrupt Air Travel
Saturday, November 15, 2003
DENVER — Glowing steadily for more than 4 billion years and rising
unfailingly every morning, the sun is something even astronomers can
take for granted. Among the 100 billion stars in the Milky Way
(search), ours is rather lackluster.
But the sun certainly is demanding everyone's attention now, three
weeks into perhaps the most dramatic and unexpected chain of
eruptions ever observed venting from its seething, bubbling surface.
There have been as many as 11 salvos since Oct. 19. And the
fireworks could reach a new crescendo by Thanksgiving, the nation's
busiest holiday for air travel, just one of the things that can be
disrupted.
"There's been nothing quite like this," said Bill Murtagh, a space
weather forecaster for the National Oceanic and Space Administration
(search) in Boulder, Colo."Another big blow is not what anyone
needs."
NASA scientists compare it to a blizzard in July -- in California.
It sounds incredible, but"something like that just happened on the
sun," says David Hathaway, a solar physicist at NASA's Marshall
Space Flight Center (search) in Alabama.
The biggest solar storm to affect Earth in the recent cycle was Oct.
28. It caused little damage, largely because it was forecast, and
electric utilities and satellite companies took precautions.
Even so, it caused a blackout in Sweden, damaged two Japanese
satellites and upset radio communications and navigation systems for
jets and ships. Airlines in the northern latitudes flew lower to
protect passengers from extra doses of radiation.
It is a startling reminder of who's really in charge of the solar
system. Scientists worry that a new round of eruptions could do more
of the same or worse.
Each solar burst hurls into space huge clouds of superheated,
charged particle clouds that are 13 times the size of Earth. One
explosion on Nov. 4 ranks as the most powerful solar flare to be
recorded by orbiting instruments -- although it was pointed away
from Earth.
"This period will go into the history books as one of the most
dramatic," said Paal Brekke, deputy project scientist for SOHO, a
joint U.S.-European observatory between Earth and the sun.
What will the sun do next? Astronomers can only watch and wait.
Early civilizations from the Sumerians to the Aztecs worshipped the
sun for its life-nourishing properties. Its furious dynamics weren't
discovered until Galileo and others in the 17th century began to
directly observe the sun through the first telescopes, sacrificing
their eyesight for their discoveries.
In 1613, Galileo published three letters on sunspots, the cooler,
dark, irregular spots that resemble cancerous moles on the sun's
fiery face. By recording the sunspots' disappearance around the far
side, Galileo was the first to demonstrate that the sun rotates.
But how do sunspots form and how do they trigger solar explosions?
How do they affect Earth? Researchers still aren't entirely sure.
The sun is not solid, but a dense and torrid ball of gas. It rotates
in sections at different latitudes as if the layers of a cake were
turning at different speeds, with the equator's layer moving faster
than the poles.
This phenomenon tangles and twists the sun's magnetic field. The
migration of hot plasma from the sun's interior dynamo up to the
surface is somehow inhibited in these distortions, producing
sunspots.
Sunspots erupt and fade in 11-year cycles. But that's just an
average; some cycles last 15 years.
New studies suggest sunspots also work in longer patterns of 100 and
1,000 years. The sun's luminosity can change slightly during those
cycles, possibly affecting Earth's climate and, some argue,
contributing to global warming. If true, those details will take
years to work out.
The current 11-year solar cycle, No. 23, peaked quietly in 2000. By
late 2003 it was supposed to be on its downside. Researchers were
labeling it a dud.
Until now.
Sunspots' magnetic distortions intensify until something explodes.
Some sunspots reload and fire again. And again. That is what's
happening now with the current sunspot clusters, 484 and 486.
From 93 million miles away, they look like tiny smudges on the sun's
chin. Yet each rival Jupiter in size.
Forecasters in Boulder are analyzing past cycles to determine
whether powerful sunspots similarly have appeared late.
"In 1984, we had a bout of activity four years after the solar max
in that cycle," Murtagh said."What's different with cycle 23 is
today's events are more intense than what occurred at the cycle's
maximum."
Sunspots are best known for spawning solar flares, which are akin to
space tornadoes. They last for hours, extend for tens of thousands
of miles and reach millions of degrees.
In recent years, astronomers have identified a second and even more
powerful tempest -- the coronal mass ejection. Like a cosmic Molotov
cocktail, that is the phenomenon that has been bombarding Earth
lately.
A CME bursts from the sun's corona, the wispy, outermost and hottest
layer. Often, CMEs trigger solar flares below, too.
CMEs belch huge clouds of superheated particles at speeds exceeding
1 million mph. Earth can orbit straight into the speeding particles
and they can envelop the planet for hours.
If these incoming particles have a southward magnetic orientation,
they slice against the grain of Earth's north-pointing magnetic
field, and travel deep into the atmosphere. This causes electrical
and radio disturbances, as well as colorful aurora displays in the
night sky.
Space forecasters measure the intensity of CMEs on three scales.
Each scale is 1-5.
The G-scale measures the geomagnetic storm generated when the
particle cloud slams into Earth's magnetic field. A G5 storm can
knock out electrical power grids.
The S-scale measures radiation pulses. In an S5 storm, airline
passengers flying though the incoming fallout would receive the
equivalent dose of 100 chest X-rays.
The R-scale measures radio blackouts. At R5, the entire sunlit side
of Earth would experience a high-frequency radio blackout.
The CME on Oct. 28 measured G5-S4-R4.
"It was almost the perfect space storm," Murtagh said. Yet, because
utilities and satellite companies were ready for it, its damage was
limited.
A fourth scale measures the intensity of X-ray emissions from solar
flares.
During the current sunspot period, solar flares erupting on Oct. 19
rated X3 and X5. On Oct. 28-29, the major CME triggered a one-two
solar flare punch. The first measured X17.2 -- it was the third-
largest flare ever recorded. A day later, the second flare measured
X11.
But Sunspot 486 was just warming up.
Beginning on Nov. 3, it triggered three flares over several hours.
The final flare on Nov. 4 saturated the X-ray detectors on NASA's
GOES satellite, which produces a new image of the sun every minute.
The satellite was blinded for 11 minutes.
Luckily for Earth, the sunspot cluster was rotating off the sun's
face and out of view. Most of its fury was directed harmlessly into
space.
Officially, it is ranked as X28. But some researchers believe it
might've registered an astonishing X40.
Previously, the most intense flares were a pair of X20s.
The X-scale has been in use only since the 1970s, so historical
comparisons are difficult. But the Nov. 4 flare rivals an event in
1859 that knocked out telegraph service across in the United States.
"What is clear is that the latest flare is the strongest ever
recorded," Brekke said.
Scientists are certain sunspots 484 and 486 will surf back around
the sun's face and take aim at Earth again. Though hidden from view,
their explosiveness can be gauged by researchers much as seismic
waves from earthquakes are measured.
The SOHO observatory is also photographing clouds of gas being
thrown over and around the sun's far side by unseen explosions.
Astronomers are warning satellite and power grid operators to be
ready for more fireworks.
"Society is becoming more dependent on systems that could fail
during these events," Brekke said."People should not be afraid, but
we should learn to live with our closest star and how it is varying."
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