Sun emits moderate solar flare

GREENBELT, Md., Nov. 13 (UPI) -- NASA said the sun emitted a mid-level M-Class solar flare Tuesday, an example of the weakest flares that can still cause some space weather effects near Earth.

While radiation from a flare cannot pass through Earth's atmosphere to affect humans on the ground, if intense enough they can disturb the atmosphere in the layer where global positioning system and communications signals travel, the space agency said.

Tuesday's flare caused some "moderate" radio signal disruptions, NASA said.

Solar flares are becoming more frequent as the sun's normal 11-year cycle is heading toward a solar maximum expected in 2013, astronomers said.

The flare was not associated with a coronal mass ejection, they said, another solar phenomenon that can send solar particles into space that can reach Earth one to three days later.