Forecasting Solar Storms

It was an eerie moment for owners of electronic pagers last May, when 45 million of the units across North America suddenly flickered and died. The blackout was caused not by some routine equipment failure but by a massive storm on the surface of the sun that shorted out an Earth-orbiting communications satellite. Such solar typhoons are not uncommon, and the damage they do can be considerable. Last week NASA announced that it may now be possible to predict the storms and take action to limit their impact.

The most violent type of solar eruption is known as a coronal mass ejection, a vast bubble of gas that bursts from the sun and releases a wave of charged particles into space. Slamming into Earth's atmosphere, CME discharges have been known to fry satellites, bathe airplanes with radiation and black out entire cities.

Recently, researchers studying satellite images of the sun have paid special attention to great, S-shaped twists of plasma called sigmoids that they now believe are an early stage of CME formation. Find a sigmoid, and within a few days you'll probably see an explosion. Since it takes an additional four days for the solar tsunami to reach Earth, you can double today's early-warning time.

That time can be well used. Satellite operators who know a cme storm front is coming can briefly shut their systems off to prevent short-circuiting. Earth-based power grids can be temporarily--if expensively--reconfigured to provide extra grounding. Astronauts planning a space walk can stay indoors until the danger passes. "Each sigmoid is like a loaded gun," says solar researcher Alphonse Sterling, who helped make the discovery. Now, it seems, humanity may have a better chance of dodging the bullet.