+ Play
Audio
|
+ Download Audio | +
Email to a friend | +
Join mailing list
May
6, 2008: At 11:18 AM on the cloudless morning of
Thursday, September 1, 1859, 33-year-old Richard Carrington—widely
acknowledged to be one of England's foremost solar astronomers—was
in his well-appointed private observatory. Just as usual on
every sunny day, his telescope was projecting an 11-inch-wide
image of the sun on a screen, and Carrington skillfully drew
the sunspots he saw.
Right:
Sunspots sketched by Richard Carrington on Sept. 1, 1859.
Copyright: Royal Astronomical Society: more.
On
that morning, he was capturing the likeness of an enormous
group of sunspots. Suddenly, before his eyes, two brilliant
beads of blinding white light appeared over the sunspots,
intensified rapidly, and became kidney-shaped. Realizing that
he was witnessing something unprecedented and "being
somewhat flurried by the surprise," Carrington later
wrote, "I hastily ran to call someone to witness the
exhibition with me. On returning within 60 seconds, I was
mortified to find that it was already much changed and enfeebled."
He and his witness watched the white spots contract to mere
pinpoints and disappear.
It
was 11:23 AM. Only five minutes had passed.
Just
before dawn the next day, skies all over planet Earth erupted
in red, green, and purple auroras so brilliant that newspapers
could be read as easily as in daylight. Indeed, stunning auroras
pulsated even at near tropical latitudes over Cuba, the Bahamas,
Jamaica, El Salvador, and Hawaii.
Even
more disconcerting, telegraph systems worldwide went haywire.
Spark discharges shocked telegraph operators and set the telegraph
paper on fire. Even when telegraphers disconnected the batteries
powering the lines, aurora-induced electric currents in the
wires still allowed messages to be transmitted.
"What
Carrington saw was a white-light solar flare—a magnetic explosion
on the sun," explains David Hathaway, solar physics team
lead at NASA's Marshall Space Flight Center in Huntsville,
Alabama.
Now
we know that solar flares happen frequently, especially during
solar sunspot maximum. Most betray their existence by releasing
X-rays (recorded by X-ray telescopes in space) and radio noise
(recorded by radio telescopes in space and on Earth). In Carrington's
day, however, there were no X-ray satellites or radio telescopes.
No one knew flares existed until that September morning when
one super-flare produced enough light to rival the brightness
of the sun itself.
"It's
rare that one can actually see the brightening of the solar
surface," says Hathaway. "It takes a lot of energy
to heat up the surface of the sun!"
Above:
A modern solar flare recorded Dec. 5, 2006, by the X-ray Imager
onboard NOAA's GOES-13 satellite. The flare was so intense,
it actually damaged
the instrument that took the picture. Researchers believe
Carrington's flare was much more energetic than this one.
The
explosion produced not only a surge of visible light but also
a mammoth cloud of charged particles and detached magnetic
loops—a "CME"—and hurled that cloud directly toward
Earth. The next morning when the CME arrived, it crashed into
Earth's magnetic field, causing the global bubble of magnetism
that surrounds our planet to shake and quiver. Researchers
call this a "geomagnetic storm." Rapidly moving
fields induced enormous electric currents that surged through
telegraph lines and disrupted communications.
"More
than 35 years ago, I began drawing the attention of the space
physics community to the 1859 flare and its impact on telecommunications,"
says Louis J. Lanzerotti, retired Distinguished Member of
Technical Staff at Bell Laboratories and current editor of
the journal Space Weather. He became aware of the
effects of solar geomagnetic storms on terrestrial communications
when a huge solar flare on August 4, 1972, knocked out long-distance
telephone communication across Illinois. That event, in fact,
caused AT&T to redesign its power system for transatlantic
cables. A
similar flare on March 13, 1989, provoked geomagnetic storms
that disrupted electric power transmission from the Hydro
Québec generating station in Canada, blacking out most of
the province and plunging 6 million people into darkness for
9 hours; aurora-induced power surges even melted power transformers
in New Jersey. In December 2005, X-rays from another solar
storm disrupted satellite-to-ground communications and Global
Positioning System (GPS) navigation signals for about 10 minutes.
That may not sound like much, but as Lanzerotti noted, "I
would not have wanted to be on a commercial airplane being
guided in for a landing by GPS or on a ship being docked by
GPS during that 10 minutes."
Right:
Power transformers damaged by the March 13, 1989, geomagnetic
storm: more.
Another
Carrington-class flare would dwarf these events. Fortunately,
says Hathaway, they appear to be rare:
"In
the 160-year record of geomagnetic storms, the Carrington
event is the biggest." It's possible to delve back even
farther in time by examining arctic ice. "Energetic particles
leave a record in nitrates in ice cores," he explains.
"Here again the Carrington event sticks out as the biggest
in 500 years and nearly twice as big as the runner-up."
These
statistics suggest that Carrington flares are once in a half-millennium
events. The statistics are far from solid, however, and Hathaway
cautions that we don't understand flares well enough to rule
out a repeat in our lifetime.
And
what then?
Lanzerotti
points out that as electronic technologies have become more
sophisticated and more embedded into everyday life, they have
also become more vulnerable to solar activity. On Earth, power
lines and long-distance telephone cables might be affected
by auroral currents, as happened in 1989. Radar, cell phone
communications, and GPS receivers could be disrupted by solar
radio noise. Experts who have studied the question say there
is little to be done to protect satellites from a Carrington-class
flare. In fact, a recent paper estimates potential damage
to the 900-plus satellites currently in orbit could cost between
$30 billion and $70 billion. The best solution, they say:
have a pipeline of comsats ready for launch.
Humans
in space would be in peril, too. Spacewalking astronauts might
have only minutes after the first flash of light to find shelter
from energetic solar particles following close on the heels
of those initial photons. Their spacecraft would probably
have adequate shielding; the key would be getting inside in
time.
No
wonder NASA and other space agencies around the world have
made the study and prediction of flares a priority. Right
now a fleet of spacecraft is monitoring the sun, gathering
data on flares big and small that may eventually reveal what
triggers the explosions. SOHO, Hinode, STEREO, ACE and others
are already in orbit while new spacecraft such as the Solar
Dynamics Observatory are readying for launch.
Research
won't prevent another Carrington flare, but it may make the
"flurry of surprise" a thing of the past.
SEND
THIS STORY TO A FRIEND
Authors: Trudy E. Bell
& Dr.
Tony Phillips | Editor:
Dr. Tony Phillips | Credit: Science@NASA
more
information |
Description
of a Singular Appearance seen in the Sun on September
1, 1859, Monthly Notices of the Royal Astronomical
Society, Vol. 20, p.13-15 -- the original report
by R.C. Carrington
An
engaging book on the history of the 1859 Carrington
flare and the detective work to sleuth its cause and
significance is Stuart Clark's The Sun Kings: The
Unexpected Tragedy of Richard Carrington and the Take
of How Modern Astronomy Began (Princeton University
Press, 2007).
One recent analysis on the effects of a potential future
solar flare of similar magnitude is "The
Carrington event: Possible doses to crews in Space from
a comparable event," by L. W. Townsend et al.,
Advances in Space Research 38 (2006): 226–231--one of
16 articles in an entire special issue devoted to the
1859 Carrington flare.
See also "The
1859 Solar–Terrestrial Disturbance and the Current Limits
of Extreme Space Weather Activity," by E. W.
Cliver and L. Svalgaard, Solar Physics (2004) 224: 407–422
(available at ) and "Forecasting
the impact of an 1859-caliber superstorm on geosynchronous
Earth-orbiting satellites: Transponder resources,"
by Sten F. Odenwald and James L. Green, Space Weather
(2007) 5: 1-16.
NASA is well aware of radiation hazards in space and
taking mitigation measures. A book-length report on
a 2005 workshop exploring the subject is Space
Radiation Hazards and the Vision for Space Exploration:
Report of a Workshop published by the National Research
Council in 2006.
NASA's
Future: US
Space Exploration Policy
|
|