33pc of Sun’s blasts are ’sneak attacks’ that occur without warning

WASHINGTON - Astronomers have revealed that one-third of the Sun’s blasts are “sneak attacks” that may occur without warning.

“If space weather forecasters rely on some of the traditional danger signs, they’ll miss a significant fraction of solar eruptions,” said Suli Ma of the Harvard-Smithsonian Center for Astrophysics (CfA).

Ma and her colleagues studied 34 solar eruptions over 8 months using the STEREO spacecraft, which allows us to study the Sun from two different angles simultaneously.

STEREO is ideal for studying coronal mass ejections, or CMEs. A CME is a huge eruption from the Sun that blasts a billion tons of highly charged particles into space at speeds greater than a million miles per hour.

When those charged particles reach Earth, they interact with our planet’s magnetic field, potentially creating a geomagnetic storm. Such a storm can interfere with satellite communications, disrupt power grids, or even short out orbiting satellites.

The new study revealed that 11 of the 34 CMEs observed by STEREO were “stealthy,” showing none of the usual signals. As a result, any system designed to watch for such warning signs could miss one-third of all solar blasts.

“Meteorologists can give days of warning for a hurricane, but only minutes for a tornado. Currently, space weather forecasting is more like tornado warnings,” said Smithsonian astronomer Leon Golub.

“We might know an eruption is imminent, but we can’t say exactly when it will happen. And sometimes, they catch us by surprise,” he added.

The team plans to continue looking for subtle clues that might allow us to predict an impending “stealth” CME. They caution that their study occurred during a prolonged minimum of solar activity; conditions may change as solar activity increases over the next few years.

Their findings appeared in the Oct. 10, 2010 issue of The Astrophysical Journal (ANI)