A New Kind of Solar Storm

Going to the Moon? Be careful. A new kind of solar storm can take you by surprise.

January 2005 was a stormy month - in space. With little warning, a giant spot materialized on the sun and started exploding. Between January 15th and 19th, sunspot 720 produced four powerful solar flares. When it exploded a fifth time on January 20th, onlookers were not surprised.

They should have been. Researchers realize now that the January 20th blast was something special. It has shaken the foundations of space weather theory and, possibly, changed the way astronauts are going to operate when they return to the Moon.

Sunspot 720 unleashed a new kind of solar storm.

more The Jan. 20th proton storm photographed from space by the Solar and Heliospheric Observatory (SOHO). The many speckles are solar protons striking the spacecraft's digital camera.

Scant minutes after the January 20th flare, a swarm of high-speed protons surrounded Earth and the Moon. Thirty minutes later, the most intense proton storm in decades was underway.

"We've been hit by strong proton storms before, but [never so quickly]," says solar physicist Robert Lin of UC Berkeley. "Proton storms normally develop hours or even days after a flare." This one began in minutes.

Proton storms cause all kinds of problems. They interfere with ham radio communications. They zap satellites, causing short circuits and computer reboots. Worst of all, they can penetrate the skin of space suits and make astronauts feel sick.

"An astronaut on the Moon, caught outdoors on January 20th, would have had almost no time to dash for shelter," says Lin. The storm came fast and "hard," with proton energies exceeding 100 million electron volts. These are the kind of high-energy particles that can do damage to human cells and tissue.

"The last time we saw a storm like this was in February 1956." The details of that event are uncertain, though, because it happened before the Space Age. "There were no satellites watching the sun."

According to space weather theory - soon to be revised - this is how a proton storm develops:

It begins with an explosion, usually above a sunspot. Sunspots are places where strong magnetic fields poke through the surface of the Sun. For reasons no one completely understands, these fields can become unstable and explode, unleashing as much energy as 10 billion hydrogen bombs.

From Earth we see a flash of light and X-rays. This is the "solar flare," and it's the first sign that an explosion has occurred. Light from the flare reaches Earth in only 8 minutes.