HARVARD GAZETTE ARCHIVES

This image of the Oct. 28 solar flare was taken by the Extreme ultraviolet Imaging Telescope (EIT) on board NASA's Solar and Heliospheric Observatory (SOHO) spacecraft. It shows a tremendous burst of X-ray light associated with the flare. (Photo courtesy of NASA)

The aftermath of the solar eruption kept Harvard-Smithsonian Center for Astrophysics' sun-observing instrument aboard NASA's Solar and Heliospheric Observatory spacecraft (SOHO) shuttered Wednesday even as scientists began analyzing unusual data recorded from the event.

The eruption created a monstrous solar flare - the third largest recorded since 1976 - and an associated coronal mass ejection, in which superheated gas, called plasma, streaks away from the sun at millions of miles an hour. When the plasma hits the Earth it can disrupt the planet's magnetic field, triggering a geomagnetic storm.

The geomagnetic storm associated with this event began at about 4 a.m. Wednesday and reached the highest level for such storms - G5 on a scale that starts at G1 - for about three hours before decreasing, according to John Kohl, a solar astrophysicist at the Harvard-Smithsonian Center for Astrophysics. Kohl is the principal investigator for the Ultraviolet Coronagraph Spectrometer on board SOHO.

"Presumably this [geomagnetic storm] is associated with this event," Kohl said. "It's arriving earlier than anticipated. It's a little bit surprising it got here so fast."

Kohl said the geomagnetic storm will likely wax and wane repeatedly for about 24 hours. The Earth's fluctuating magnetic field during the storm can cause electric surges that can disrupt communications, damage satellites, and cause power outages.

Kohl said the next largest recorded solar flare occurred in 1989 and was blamed for a massive power outage in Canada that left 6 million people in the dark.

A much weaker solar eruption last week struck the Earth a glancing blow, disrupting airline communications. The flare associated with Tuesday's storm is not only much larger than the one last week, rated X17.2 compared with X5, but in addition, the blast of superheated gas ejected toward the Earth is expected to make a direct hit.

"It appears to be a spectacular event - and an unlikely one - where it is perfectly positioned to have an effect on the Earth," Kohl said on Tuesday.

Kohl said the plasma cloud heading towards Earth was so large, it appeared to completely cover the sun, extending beyond its edges to create a halo. Scientists estimate it was traveling at just under 5 million miles an hour when it left the sun.

Kohl was awakened shortly after the event occurred at 5:54 a.m. on Tuesday because operators of the Ultraviolet Coronagraph Spectrometer on board SOHO feared the instrument would be damaged by the high energy particles from the eruption that were bombarding it. After taking initial measurements, Kohl's team shut the instrument down.

As of early Wednesday afternoon, Kohl said they were evaluating whether to reactivate the spectrometer.

The event could provide some insights as to the sun's magnetic nature, Kohl said. Immediately after the enormous eruption, scientists saw material not only moving toward the Earth, but also moving away from it, as if the force of the explosion blew the magnetic field back, away from the Earth, pulling some material with it.

"I think we're going to learn about magnetic fields during this event," Kohl said.

Besides disrupting communications, endangering satellites, and potentially triggering power outages, the coming storm is expected to create a showing of the aurora borealis, or northern lights, visible as far south as Florida. It poses no danger to people on Earth, who are protected by the atmosphere. It could, however, harm astronauts venturing outside the shelter of their spacecraft.

"Probably the most pleasing side of this is that the aurora borealis should be spectacular," Kohl said.