Any astronomer will tell you that the Sun is unpredictable. But on Jan. 20,
2005 it was dangerously so, leaving scientists to rework theories of how space
storms operate and showing that interplanetary space travel will be a deadly
serious business.
In new studies presented today, researchers detailed a solar outburst that
shocked Earth with the highest dose of radiation measured in five decades.
The tempest arrived frighteningly fast.
Other solar outbursts have provided more
dramatic pictures, more threatening X-ray
flares, and tremendous coronal mass ejections of hot gas that arrive several
hours later. But the solar event at 2 a.m. ET on that January morning created
an intense burst of energetic protons that, surprisingly, tripped radiation
monitors all over the planet within moments.
"This flare produced the largest solar radiation signal on the ground in nearly
50 years," said Richard Mewaldt of the California Institute of Technology. "But
we were really surprised when we saw how fast the particles reached their peak
intensity and arrived at Earth."
A NASA movie
based on satellite data shows gamma rays (blue) and X-rays (red) tossed
out by the flare on Jan. 20, 2005.
Danger!
Solar Storm
Is Earth's technology safe from the Sun's fiery flare-ups? Go deep
inside NOAA's Space Environment Center -- the first place on Earth to
feel the Sun's wrath.
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Mewaldt is a co-investigator on NASA's Advanced Composition Explorer (ACE)
spacecraft, which monitored the event. Several studies on the flare are being
presented this week at a meeting of the American Geophysical Union (AGU) New
Orleans.
The raging proton storm peaked in 15 minutes. Normally, the most intense part
of a proton event takes two hours or longer to build up.
"That's important because it's too fast to respond with much warning to astronauts
or spacecraft that might be outside Earth's protective magnetosphere," Mewaldt
said. "In addition to monitoring the Sun, we need to develop the ability to
predict flares in advance if we are going to send humans to explore our solar
system."
Normally, officials with NOAA's Space Environment Center notify NASA and satellite
operators when a storm is en route. Residents of the International Space Station
can take cover in a well shielded section of the ship. Managers of power systems
on Earth can avoid major grid shifts until the storm passes. Some satellites
are placed into modes of reduced operation to avoid electrical shorts that have
destroyed craft in the past.
Other researchers have previously said that before humans can be sent to Mars,
an interplanetary
radiation monitoring system will have to be installed.
Scientists are now scratching their heads over the oddity of this eruption.
"Since about 1990, we've believed proton storms at Earth are caused by shock
waves in the inner solar system as coronal mass ejections plow through interplanetary
space," said Professor Robert Lin of the University of California at Berkeley.
"But the protons from this event may have come from the Sun itself, which is
very confusing."
Lin is principal investigator for the Reuven Ramaty High Energy Solar Spectroscopic
Imager (RHESSI) satellite.
Flares emanate from sunspot groups, regions of the Sun where intense magnetic
energy caps upwelling solar material, creating cooler, darker spots. The surprising
January flare came on the heels of a series
of other very large but otherwise normal flares from the same sunspot group.
Scientists can't say why the fifth event was so unusual.
"It means we really don't understand how the Sun works," Lin said.
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