Solar flare portends disruption on earth

A gigantic eruption on the surface of the sun could cause one of the worst solar storms in years today, potentially disrupting satellites and power systems while exposing astronauts on the International Space Station to heightened radiation levels, as charged particles from the sun bombard the earth.

The coming geomagnetic storm, rated as severe by the National Oceanic and Atmospheric Administration, poses no direct threat to health on earth, but it could play havoc with anything that relies on electronics, from cellphones to air travel. NOAA forecasters say that the storm, forecast to hit at midday, is far more powerful than one last week that prompted warnings but did little damage other than disrupting airline communications.

"This is the real thing," said John Kohl, a solar astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge. "It's headed straight for us, like a freight train."

Despite its seemingly steady orange glow, the surface of the sun is ever changing, as sudden bursts of electromagnetic radiation called solar flares shoot into space at millions of miles an hour. The storm forecast for today began with a solar flare 13 times bigger than the earth. It is the biggest Harvard-Smithsonian solar specialists have seen in 30 years, sending enormous amounts of energy and matter directly toward our planet.

Severe solar storms cause a sudden shift in the electromagnetic field surrounding the earth, triggering power surges that can knock out satellites or blow out electric transformers on the ground. A solar storm in 1989, one of the worst on record, caused a blackout over much of Quebec Province.

Today, NOAA issues regular solar weather forecasts, allowing companies and government agencies to take precautions if a storm is coming. ISO-New England, which manages the electricity grid for this region, halted all maintenance work on transmission lines last Friday because of the risk of power surges. The agency can also lower the voltage transmitted on its lines to reduce the risk of a damaging surge.

Solar storms are especially hazardous for astronauts, who don't have the earth's atmosphere to protect them from the sun's radiation. The astronauts on the International Space Station did not detect elevated radiation during last week's storm, but radiation can be a great hazard in space. At the height of a 1989 storm, an astronaut on the surface of the moon would have faced near-lethal dose of radiation.

Harvard's Kohl said that everyone needs to pay attention to today's storm. Yesterday's "eruption was pointed directly at us and is expected to have major effects," he said.

Scott Allen can be reached at allen@globe.com.