WASHINGTON (AFP) – The strongest solar flare in four years disrupted radio communications in southern China, according to the China Meteorological Administration. The solar flare, a huge explosion on the sun's surface caused by magnetic activity, affected transmissions in southern China on Tuesday, Xinhua news agency reported, quoting the CMA. The US space administration NASA confirmed that Monday's solar flare was the largest in four years, and the event sparked predictions of heightened activity on the northern hemisphere of the sun. "X-class flares are the most powerful of all solar events that can trigger radio blackouts and long-lasting radiation storms," disrupting telecommunications and electric grids, NASA said. Solar flares are classified as A, B, C, M or X, with each class having a peak 10 times greater than the preceding one. NASA also said the flare caused "sudden ionospheric disturbances" in the atmosphere above China and the CMA warned there was a high probability that large solar flares would appear over the next three days. NASA's Solar Dynamics Observatory saw a large coronal mass ejection associated with the flash that is blasting toward Earth at about 560 miles per second (900 kilometers per second). Monday's flare erupted in the sun's southern hemisphere, which has so far shown less flare activity than the northern hemisphere. It followed several smaller M-class and C-class flares in recent days. A magnetic storm caused by a solar eruption in 1973 plunged six million people into darkness in Canada's eastern-central Quebec province.