- A pair of strong solar storms that hit Earth late last
week were squalls compared to the torrent of electrons that rained down
in the "perfect space storm" of 1859. And sooner or later, experts
warn, the Sun will again conspire again send earthlings a truly destructive
bout of space weather.
-
- If it happens anytime soon, we won't know exactly what
to expect until it's over, and by then some modern communication systems
could be like beachfront houses after a hurricane.
-
- In early September in 1859, telegraph wires suddenly
shorted out in the United States and Europe, igniting widespread fires.
Colorful aurora, normally visible only in polar regions, were seen as far
south as Rome and Hawaii.
-
- The event 144 years ago was three times more powerful
than the strongest space storm in modern memory, one that cut power to
an entire Canadian province in 1989. A new account of the 1859 event, from
research led by Bruce Tsurutani of NASA 's Jet Propulsion Laboratory, details
the most powerful onslaught of solar energy in recorded history.
-
- Solar Conspiracy
-
- Space storms are created when the Sun erupts, sending
charged particles racing outward, an expanding bubble of hot gas called
plasma.
-
- In 1859, four crucial events conspired at one moment,
Tsurutani told SPACE.com.
-
- "The plasma blob that was ejected from the Sun hit
the Earth," he said. That's a relatively routine event. What preceded
the strike was more unusual. "The blob came at exceptionally high
speeds. It took only 17 hours and 40 minutes to go from the Sun to Earth."
Solar storms typically take two to four days to traverse the 93 million
miles (150 million kilometers).
-
- "The magnetic fields in the blob, called a coronal
mass ejection, were exceptionally intense," Tsurutani said. "And
the fourth, most important, ingredient was that the magnetic fields of
the blob were opposite in direction from the Earth's fields."
-
- Earth's magnetic field normally protects the surface
of the planet from a continual flow of charged particles, called the solar
wind, and even does a pretty good job defending against some storms. When
a storm swept past Earth last Friday, it met up with magnetic field pointed
in such a way that it thwarted the storm's effects. That's not always the
case.
-
- In 1859, the planet's defenses were overwhelmed.
-
- That Was Then
-
- Society back then did not notice the storm the way it
would today. The telegraph was 15 years old. There were no satellite TV
feeds, no automated teller machines relying on orbiting relay stations,
and no power grids.
-
- Tsurutani said scientists can't yet accurately measure
or predict what the strength or direction of Earth's magnetic field will
be when a storm arrives. The storms themselves can be predicted. And Tsurutani
says there will eventually be another one like 1859.
-
- "It could very well be even more intense than what
transpired in 1859," he says. "As for when, we simply do not
know."
-
- Bernhard Fleck, the European Space Agency's project scientist
for the Sun-watching SOHO spacecraft, says the next super space storm will
be detectable, but that's only half the story.
-
- "A monster event of the magnitude described [by
Tsurutani] we would easily recognize as something extraordinary with SOHO
and other solar instruments," Fleck said in an e-mail interview. But,
he added, "We certainly wouldn't know its full extent until arrival."
-
- During the 1859 flare-up, solar observers logged almost
an entire minute during which the amount of sunlight doubled at the region
of the flare.
-
- "Such a strong white-light flare has never been
seen since," says Paal Brekke, SOHO deputy project scientist. "So
if this type of flare happened, yes we would know right away." But
he adds that the orientation of Earth's magnetic field would not be known.
Future space-based observatories could address this blind spot in space
weather forecasting.
-
- Meanwhile, the blind spot became clear on Friday.
-
- Forecasters at NOAA's Space Environment Center, relying
on SOHO pictures and data, warned of an impending set of storms that could
disrupt communications and might set off colorful aurora Friday and Saturday.
The forecast, along with two Jupiter-sized sunspots at the roots of the
storms, gained widespread media attention.
-
- But the first and larger of the storms passed by with
far less effect than one might have been led to expect. In fact, they were
both comparative drops in the space weather bucket.
-
- Extreme Measures
-
- To get an idea of the strength of the 1859 storm, you
have to wade into nT's for a moment.
-
- A space storm's impact is measured in nano-Teslas (nT),
Brekke explained. The lower the figure, the more powerful the storm. A
moderate storm can be around -100 nT; extreme and damaging storms have
been logged at around -300 nT.
-
- The 1989 coronal mass ejection that knocked out power
to all of Quebec, Canada measured -589 nT, Brekke said. The 1859 perfect
storm was estimated to have been -1,760 nT. Brekke used three exclamation
points in his e-mail delivering that number.
-
- People on the ground are generally safe even in the worst
space weather. But technology could be in trouble when the next super storm
hits.
-
- "In 1859, the technology was quite low in comparison
to today's technology," Tsurutani said. "However the technology
that we rely on today is much more vulnerable."
-
- A strong storm does its damage in part by inducing currents
on power and communication lines, leading to potential overloads. Obviously,
there are a lot more wires on Earth today, "so one might expect much
worse problems if it occurred today."
-
- The charged particles can also zap satellites, as has
occurred with handful of storms in recent years -- events with far fewer
charged particles than in 1859. A space storm also heats the upper level
of Earth's atmosphere, causing it to expand. That's no good for satellites
that can get caught up in air that didn't used to be there.
-
- "This can lead to enhanced satellite drag and possible
loss of these to the atmosphere," Tsurutani said.
-
- Tsurutani and his colleagues -- Walter Gonzalez of the
Brazilian National Space Institute and Gurbax Lakhina and Sobhana Alex
of the India Institute of Geomagnetism -- reviewed known observations of
the 1859 event's solar and aurora output, plus accounts from the ground.
They also used recently rediscovered historic data on Earth's magnetic
field from the Colaba Observatory in India.
-
- The findings were published in a recent issue of the
Journal of Geophysical Research.
- http://us.rd.yahoo.com/dailynews/space/sc_space/byline/SIG=6rt8b7/*http://www.space.com
- This article is part of SPACE.com's weekly Mystery Monday
series.
- Copyright © 2003 SPACE.com.
|
No comments:
Post a Comment