We're going to get hit again
Posted: October 30, 2003

Just when we thought we were through the worst of it, a second gigantic solar flare has erupted, sending another coronal mass ejection directly towards Earth. The X10-class flare was detected by an orbiting GOES satellite at 3:37 p.m. EST on Wednesday, Oct. 29th and peaked at 3:49 p.m., according to the National Oceanic and Atmospheric Administration.

"It's like the Earth is looking right down the barrel of a giant gun pointed at us by the Sun...and it's taken two big shots at us," says John Kohl, a solar astrophysicist at the Harvard-Smithsonian Center for Astrophysics (CfA) and principal investigator for the Ultraviolet Coronagraph Spectrometer on board NASA's Solar and Heliospheric Observatory (SOHO) spacecraft.

"The Sun is really churned up. The timing of two very large X-class flares aimed directly at the Earth, occurring one right after another, is unprecedented," says Kohl. " I have not seen anything like it in my entire career as a solar physicist. The probability of this happening is so low that it is a statistical anomaly."

As the faster moving particles from the second eruption catch up to the slower moving particles from the first eruption - the combined effects cannot be predicted. Kohl states, "This second blast is moving like a fast freight train that very soon will plow into the back of the slower moving freight train in front of it just as it pulls into the station. The station, in this case, happens to be the planet Earth."

The two eruptions may create a combined geomagnetic storm that could influence the Earth in a number of ways, including disrupting satellite communications and power grids. However, precautions have already been taken to minimize the potential impact. For example, power companies have reduced the line loads to allow leeway for possible surges.

People on the ground are well protected from the ongoing geomagnetic storm due to the Earth's natural shielding. Pacemakers and similar devices are not affected. Airline travel also is safe, since the Earth's magnetosphere and atmosphere block the solar radiation. The web site space.com reports that the astronauts aboard the International Space Station are taking the precaution of staying in the most shielded areas of the station during these periods of high solar activity.

A solar flare is a magnetic storm on the sun. It appears as a very bright spot, and blurps gas from the Sun's surface into space. Solar flares are classified based upon their x-ray energy output at peak burst intensity. Solar flares generally don't have much of an effect on our world.

A coronal mass ejection (CME), by contrast, can affect the Earth dramatically. A CME is a huge eruption from the Sun that blasts a billion tons of highly charged particles into space at speeds greater than a million miles per hour. When those charged particles reach the Earth, they can damage orbiting satellites. The particles also interact with the Earth's magnetosphere to create spectacular auroras known as the Northern and Southern Lights.

Solar flares and coronal mass ejections often occur together like touchdowns and field goals in football games. Astronomers see the X-rays from the solar flare first because they travel at the speed of light. Then, the slower-moving (although still blazingly fast) high-energy protons from the CME reach the Earth, and that's when the fireworks begin!

"We thought we were getting through this first major solar event relatively untouched," muses Kohl, "but now it's turned into a cliffhanger. Part two is yet to come!"

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

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