Nation & World

LOS ANGELES — A massive explosion on the sun's surface has triggered the largest solar radiation storm since 2005 and has unleashed a torrent of charged plasma particles toward Earth, although the threat to satellites, power grids and other high-tech hardware is believed to be manageable, scientists said.

The National Oceanic and Atmospheric Administration detected a solar flare that peaked at 7:59 p.m. PST Sunday. NOAA satellites traced the bright flash of X-ray light to the same area on the sun's surface that had produced a weaker flare Thursday. A coronal mass ejection — which can hurl billions of tons of plasma at up to 5 million mph — quickly followed.

Radiation from the explosion arrived on Earth within hours of the flash, said Doug Biesecker, a physicist with NOAA's Space Weather Prediction Center. A burst of charged plasma particles was expected to reach Earth by 6 a.m. Tuesday. That charged plasma was traveling uncommonly fast, making the 93 million-mile trip to Earth in about 34 hours, rather than two or more days, as is usually the case, Biesecker said.

Sunday's radiation storm is the strongest since May 2005, Biesecker said.

The good news: Those looking for a light show Tuesday night might be in for a treat. NOAA research scientist Juan Rodriguez said the aurora borealis will be "a pretty amazing sight" in Canada and perhaps in parts of the continental United States, although a Seattle meteorologist said clouds likely will obscure such a show in Western Washington. Those in Eastern Washington will have a better chance of seeing the so-called northern lights, said Johnny Burg, with the National Weather Service.

The bad news: The bombardment of energetic particles can wreak havoc — potentially downing GPS systems, wiping out power grids, destroying sensitive satellite equipment in orbit and exposing astronauts to fatal doses of radiation.

As a precaution Monday, some flights were rerouted around polar regions, where the flash flood of charged plasma particles may interfere with navigation systems. Others flew at lower altitudes to reduce the risk of radiation exposure.

While it had been more than six years since the last storm of this magnitude, storms of this size are expected to become more frequent as a period of peak solar activity approaches in 2013.

"As we ramp up to the solar maximum next year," Biesecker said, "this sort of storm will become normal."

Scientists still don't know how to predict these solar events — a problem because they deliver a triple threat to technology on Earth, Stanford solar astronomer Todd Hoeksema said.

X-rays traveling at the speed of light hit Earth in about eight minutes. These can interfere with radio communications.

A burst of radiation traveling at near-light speeds begins pelting Earth 20 minutes to an hour later. This causes what are known as "single event upsets." Essentially, a high-energy proton traveling through a satellite can interfere with charges in the silicon-based hardware, which can cause it to spit out spurious signals.

The third and final attack comes from the burst of charged particles that affects Earth's magnetosphere, potentially interfering with aircraft navigation systems. This worry is expected to force rerouting of some flights during the storm.

These are not hypothetical fears, Biesecker said. The infamous October 2003 "Halloween storm" took out Japan's ADEOS-II spacecraft, among other victims, causing the approximately $600 million satellite to fail less than a year after launch.

"With all the technology of our advanced civilization, solar storms can have significant effects on communication, power, things like that," said Robert Lin, a physicist at the University of California, Berkeley.

Yet, most satellites built today should be relatively safe from midlevel storms such as the current one, NOAA's Rodriguez said. Modern satellites are built to withstand space weather as severe as a 1989 storm that caused a massive power outage in Canada's Quebec province.

Seattle Times education reporter Brian M. Rosenthal contributed to this report.