By Robert Roy Britt
Senior Science Writer
posted: 10:20 am ET
28 October 2003
Updated at 1:00 p.m. EST
The Sun today unleashed what appears to be the third most powerful flare in recorded history, a storm of charged particles that could hit Earth mid-day Wednesday with more effect than any since 1989, when an entire Canadian province had its power knocked out.
Depending on the storm's magnetic orientation, it could set off a dramatic display of colorful northern lights well into mid-latitudes of the United States and Europe.
Meanwhile, satellite operators and power grid managers are preparing to endure a potentially damaging event. And astronauts aboard the International Space Station have taken cover from heavier radiation sent out by the flare. They are not expected to be in any serious danger.
Kicked up at 6 a.m. EST (1100 UT) today, the major solar outburst comes on the heels of four other flares late last week and over the weekend. All were considered fairly severe, but the latest eruption makes the others seem like solar sneezes.
Today's blast is classified as an X17, where X denotes a major flare and larger numbers are stronger. That compares to two flare-ups over the weekend that were rated less than X2.
"The flare today may be the third strongest X-flare on record," said Paal Brekke, deputy project scientist for the SOHO spacecraft, which first spotted the event.
A slightly stronger flare on April 2, 2001 was not pointed at Earth. Today's storm is headed directly at us and could generate fantastic colorful lights in the atmosphere, known as aurora. The storm associated with the flare is called a coronal mass ejection, an expanding bubble of charged particles that race outward.
The storm is traveling quicker than most and is forecast to arrive about 30 hours after it left the Sun, Joe Kunches, lead forecaster at NOAA's Space Environment Center, said in a telephone interview. That would put the arrival at about Noon EST Wednesday (1700 UT).
"That's when it starts," Kunches said. But the storm will blow through over several hours, he said, and won't be done for up to two days.
"We may be in for some great aurora," Brekke said.
Aurora are created when the charged solar particles stream down Earth's magnetic field lines and excite oxygen and nitrogen atoms in the atmosphere. Normally the aurora are only visible from places near the poles, like Alaska. But when Earth's magnetic field is overwhelmed, the aurora can dip will into the United States and Europe.
Wednesday evening could provide the best chance to see aurora for U.S. residents. Those in the far north may see activity pick up tonight and endure into Thursday.
The storm is also potentially a serious threat to satellites and other communication systems, including power grids on Earth. Kunches said satellite operators and power grid managers are likely to take stringent measures to protect their assets. Engineers can put some satellites into hibernation modes, and power grid operators arrange for less switching and fewer large-scale power swaps.
Nobody can say in advance what will happen, though, because the result depends on the orientation of Earth's magnetic field in relation to that of the storm.
"Until we know the orientation of the magnetic field in this [storm] cloud we won't know how severe the geomagnetic storm will be," Brekke said. "If the cloud has a southward directed magnetic field it will be severe, while if it has a northward component it will not affect us that much."
The space storm is intrinsically stronger than one on March 6, 1989 that tripped a power grid in Quebec, Canada.
Lesser storms have caused satellite problems. In 1997, an AT&T Telestar 401 satellite used to broadcast television shows from networks to local affiliates was knocked out during a solar storm. In May 1998 a solar blast disabled PanAmSat's Galaxy IV. Among the casualties: automated teller machines; gas station credit card handling services; 80 percent of all pagers in the United States; news wire service feeds; CNN's airport network; and some airline weather tracking services.
The greatest solar storm on record occurred in 1859, shorting out telegraph wires and starting fires in the United States and Europe. Brekke told SPACE.com today's storm, if it hooks up with Earth in just the right way, would be about one-third as strong as the 1859 tempest. It could, he added, be either less or more powerful than the 1989 storm.
The coronal mass ejection is one in a series sent out by two huge sunspots, the largest pair to grace the Sun at one time in recent memory. Sunspot 486 was responsible for this blast. More are possible in coming days.
Astronauts take cover
Today's eruption also accelerated a high-energy proton shower. These can cause damage to satellites and can be harmful for astronauts, Brekke said. NASA is careful not to plan spacewalks during solar storms.
Aboard the International Space Station the Expedition Eight crew of Mike Foale and Alexander Kaleri adjusted their workday a bit in response to the storm. Radiation from a solar flare -- which preceded the coronal mass ejection -- arrives at light-speed and has already been detected at the orbiting outpost. Light and other radiation travels from the Sun to Earth in about 8 minutes.
Beginning at 8:49 a.m. EST Tuesday and continuing through 1:45 p.m. EST, the two-man caretaker crew confined themselves to the most heavily protected area of the station for about 20 minutes during every 90-minute orbit.
The specific times, all in EST, are 9:35 to 9:55 a.m., 10:20 to 10:45 a.m., 11:50 a.m. to 12:15 p.m. and 1:25 to 1:45 p.m.
The times coincide with when the station's orbit takes it to the farthest north and south points from the equator, areas where Earth's magnetic fields provide the least amount of natural protection from the Sun's fury.
"The crew has seen some higher levels of radiation, so that's exactly why they do this," said NASA spokesman Kyle Herring. "The flight surgeons monitor this very, very closely."
Increased solar activity also prompted the Expedition Two and Expedition Three crews to take similar precautions in April and November 2001, respectively. The safest part of the station is the far end of the Russian Zvezda service module.
The Soyuz spacecraft -- one of which returned to Earth last night with the crew of Expedition Seven -- is not as safe, as many people think because it has a heat shield, Herring said. Another Soyuz spacecraft remains docked to the station.
"The Soyuz offers probably the least amount of protection," Herring said.
-- Jim Banke, Senior Producer at SPACE.com's Cape Canaveral Bureau, contributed to this report.