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Scientists predicted yesterday sunspot activity will reach its peak between March and June, a phenomenon feared to cause disruption in the Earth's magnetic field and give rise to failures of satellite, telecom and electric power systems.

Researchers at the Korea Astronomy Observatory (KAO) said its solar monitoring telescope picked up a significant increase in the number of explosions on the solar surface, signaling the sun is approaching the maximum of its 11-year sunspot cycle.

A sunspot refers to an area on the sun's surface that looks darker because of its relatively low temperature in comparison to neighboring areas. The number of sunspots increases and decreases over an 11-year cycle, which is akin to the Earth's year. At the peak of the cycle, called the "solar maximum," a series of explosions erupt on the surface, each with power equivalent to 1 million hydrogen bombs.

"Recently, solar flares have been occuring five to eight times a day, compared to one or two times per month usually," said Park Yong-deuk, senior researcher of KAO.

"Solar activity is difficult to predict, but recent events suggest the peak is approaching." The massive explosions intensify the power and speed of solar wind that sends particles in the solar atmosphere into the space, creating dazzling displays in the heavens, but also posing serious disruptions.

"The solar material, traveling at a speed of 500-700 km per second, is a serious threat to satellites, astronauts, communication systems and electric power transmission," he said.

The disturbances, which experts call "geomagnetic storms," occur when high-energy solar protons buffet the Earth's magnetosphere and triggers large and rapid fluctuations of magnetic currents.

The last great magnetic storm occurred 11 years ago, March 13. It damaged power transmission systems in Quebec, Canada, leaving about 6 million people in the country and in some northern parts of the United States without power for more than nine hours.

"Signs show the next geomagnetic storms will be of an equal, or higher, level as the last one," Park said.

It is not certain whether the solar activity will directly affect Korea but the seven Korean satellites currently in orbit may undergo serious difficulties, the scientist said.

The intense ultraviolet and X-ray radiation may disturb satellite's positioning in orbit and disrupt long-distance radio signals by heightening the ion density in the Earth's upper atmosphere. The storms can also damage satellites' electronic components, shortening their life-span.

The sunspot maximum is scheduled to occur in the middle of this year, but could continue well beyond next year, he said.

"Given the disastrous results it may cause, satellite operators and power companies need to be prepared for the geomagnetic storm," he said.

The astronomy observatory monitors the sun's activity and the Earth's magnetic field with state-of-the-art telescopes and provides data to a wide variety of organizations that can be affected. The information is also available to the public at its Internet homepage (www.issa.re.kr).