Solar activity on October 28, 2003. A solar eruption in December disrupted the Global Positioning System, a satellite-based navigational system used widely by the military, scientists and civilians, researchers reported on Wednesday.(NASA Photo)

    BEIJING, April 5 (Xinhuanet) -- The Global Positioning System (GPS) and other navigational systems were threatened by a powerful solar flares last December, a panel of U.S. scientists revealed on Wednesday.

    GPS receivers have become widely used in recent years, using satellite signals in navigating airplanes, ships and automobiles, and in using cell phones, mining, surveying and many other commercial practices.

    "Our increasingly technologically dependent society is becoming increasingly vulnerable to space weather," David L. Johnson, director of the National Weather Service, said at a briefing.

    The cause for their concern, Johnson said, was an unexpected solar radio burst on Dec. 6 that affected virtually every GPS receiver on the lighted half of Earth. Some receivers had a reduction in accuracy while others completely lost the ability to determine position, he said.

    In addition to the GPS system, the December solar flare also affected satellites and induced unexpected currents in the electrical grid, Johnson said.

    Dale Gary of the New Jersey Institute of Technology said the burst created 10 times more radio noise than the previous record.

    The difference between that burst and normal solar radio emissions "was like the difference between the noise level of a normal conversation and the noise level in the front row of a rock concert," he said.

    Solar activity rises and falls in 11-year cycles, with the next peak expected in 2011.

(Agencies)