The sun emitted a mid-level solar flare, peaking at 1:32 pm EDT on May 3, 2013. Solar flares are powerful bursts of radiation. Harmful radiation from a flare cannot pass through Earth’s atmosphere to physically affect humans on the ground, however — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel.
This disrupts the radio signals for as long as the flare is ongoing, and the radio blackout for this flare has already subsided.
This flare is classified as an M5.7-class flare. M-class flares are the weakest flares that can still cause some space weather effects near Earth. Increased numbers of flares are quite common at the moment, as the sun’s normal 11-year activity cycle is ramping up toward solar maximum, which is expected in late 2013.