Scientists said Thursday they can now better predict when sunspots will erupt, offering earlier warning of magnetic disruptions that can cut power and interrupt communications on Earth.

The advance means astronomers will be able to know a day or two in advance when potent sunspots are expected to arise, sharpening the precision of current space weather forecasts, said the study published in the US journal Science.

The new technique could be useful in the coming years, as astronomers study what is expected to be an increase in solar activity around 2012, though some scientists have predicted the solar maximum will be delayed.

The international team of researchers, led by Stanford University physicist Stathis Ilonidis, said data from a joint NASA and European Space Agency project known as the Solar and Heliospheric Observatory has led to the breakthrough.

Potent energy bursts known as sunspots begin with magnetic fields deep inside the Sun, as many as 40,000 miles (65,000 kilometers) below the surface, it said.

Doppler observations from the observatory have shown that these forces are "much stronger than previous models had predicted," said the study.

The magnetic forces "travel from the Sun's interior at speeds between 0.19 and 0.37 miles per second (0.3 to 0.6 kilometers per second)."

The new technique allows scientists to see images of big sunspots as they form, and before they appear on the Sun's surface.

"Strong emerging flux events can now be anticipated one to two days in advance," said the study.

Solar activity tends to rise and fall every 11 years or so. The solar maximum and solar minimum each mark about half the interval of the magnetic pole reversal on the Sun, which happens every 22 years.

Solar flares and eruptions can send highly charged particles hurtling toward Earth and interfere with satellite communications, GPS systems and even airline controls.

Geomagnetic forces have been known to occasionally garble the world's modern gadgetry, and warnings were issued as recently as June when a moderate solar flare sent a fiery coronal mass ejection in the Earth's direction.