Auroras Underfoot A group of astronauts will never forget the day they
flew right through a cloud of auroras.
The lights were out and the rest of the crew were crowded around the windows. Burbank jostled in with the others and peered outside.
"It was indescribable," he says. A geomagnetic storm was raging outside, and the shuttle was flying right through it. All around were colorful auroras.
Right: The crew of the space shuttle Discovery took this picture of Southern Lights from Earth-orbit in 1991. [more]
The date was Sept. 18, 2000. Burbank was one of seven people orbiting Earth onboard the space shuttle Atlantis (STS-106). They were on a 12-day mission to prepare the space station for its first crew. Burbank and the others connected power, installed a toilet, and delivered 2,993 kilograms (6600 lbs) of supplies. There was lots to do, and no one had much time for stargazing.
But everyone paused for this: Below and around the orbiter danced glowing ribbons of orange, yellow and green light. Above, the sky was red. As Burbank looked on, "bright spots would suddenly appear and fade away again."
Cosmonaut Yuri Malenchenko, a mission specialist on STS-106, had logged more than 137 days in space--most as commander of the Russian space station Mir. He had seen it all, yet even he was amazed. "Yuri said he'd never seen anything like it," recalls Burbank.
Left: Cosmonaut Yuri Malenchenko (left) and astronaut Dan Burbank (foreground). [more]
A few days before the storm, a giant magnetic loop poking out of the Sun had collapsed. The resulting explosion hurled a coronal mass ejection (CME) toward Earth. CMEs are clouds of super-heated magnetic gas. This one raced toward our planet at 1000 km/s (two million mph) carrying 10 billion or so tons of solar material.
When the CME struck, the auroras began.
The crew was in no danger. They were deep inside the magnetosphere--a magnetic bubble about 200,000 km wide that surrounds our planet and protects us from solar storms. The cloud hit the magnetosphere, not the astronauts.
Imagine going to the refrigerator, opening the door and finding a bowl of jello. (Is it ready to eat?) You thump the surface with your finger. It jiggles. (Yes.) That's exactly what happens to Earth's magnetosphere when a CME strikes. The magnetosphere is briefly compressed; it rebounds and then it quivers, sometimes for days.
Below: Still frames from a digital movie showing how coronal mass ejections compress Earth's magnetosphere and trigger auroras. Click to view the full 800 kb Quicktime animation created by Digital Radiance, Inc.
Such "CME-thumps" shake loose electrons and protons trapped in the magnetosphere by lines of force called "magnetic bottles." They rain down on Earth's atmosphere and cause the air to glow where they hit. The process is similar to the way an electron beam paints a picture on the front of a color TV tube.
Auroras happen far above Earth's surface. The lights stretch in altitude from about 80 to 500 km. No airplane can fly through them, but the space shuttle and the International Space Station (ISS) can. Those spacecraft circle the earth about 350 km high, not far above the brightest Northern Lights.
"That's what it was like on STS-106, except we were inside the display." (Atlantis was over the southern hemisphere at the time, so the auroras were in fact "Southern Lights.")
"There was no interaction between the shuttle and the lights," adds Burbank. Precipitating electrons and protons that cause auroras are not very energetic (thousands of times less powerful than potentially hazardous cosmic rays). Neither the spacecraft nor the crew were noticeably affected--other than dropped jaws and a sudden sense of wonder.
Burbank, who happens to be an amateur astronomer, says he would love to live and work on the space station. "Shuttle missions are hectic; every minute is packed with activity. Astronauts on the ISS are busy, too, but," he points out, "they have more time to look out the window."
Indeed, the ISS is a great place for aurora watching.
Left: Astronauts onboard the ISS saw these vivid green auroras on Oct. 4, 2001. [more]
The space station soars over places as far north as Canada and as far south as New Zealand--in other words, aurora country. Because the ISS visits both hemispheres, astronauts onboard can enjoy both Northern and Southern Lights, sometimes in the same day. Few sky watchers on Earth have seen both in a lifetime.
"It would be great to go on an ISS expedition, to mount cameras in the windows and get some good exposures," says Burbank. He hasn't been assigned to the station yet, but he does have another shuttle mission next year: STS-115. Like before, he'll be doing construction work on the space station -- a hectic, busy time.
But no matter how busy things get, Burbank says, he plans to occasionally glance out the window. You never know what you might see out there.
NASA Human SpaceFlight -- (Spaceflight.nasa.gov) NASA's home page for the International Space Station and the space shuttles.
Visit spaceweather.com for more information about auroras and ongoing geomagnetic activity.
A Surprising CME -- (Science@NASA) read about the explosion that triggered the Sept. 16-18, 2000, geomagnetic storm.
STS-106 -- (Spaceflight.nasa.gov) Space Shuttle Atlantis spent nearly 12 days in orbit during September 2000, seven of which were spent docked with the International Space Station.
'tis the Season for Auroras -- (Science@NASA) Autumn is a good time to spot Northern Lights, and scientists would like to know why.
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