BOULDER, Colo., Oct. 30 (UPI) -- NASA says the sun emitted a significant solar flare Wednesday, its fourth X-class flare this week as it nears the maximum in its 11-year activity cycle.
Solar flares are powerful bursts of radiation. Earth's atmosphere protects humans from harmful radiation from a flare, but flares can be intense enough to disturb the atmosphere in the layer where GPS and communications signals travel, causing disruption.