The sun emitted a significant solar flare, peaking at 12:22 p.m. EDT on March 11, 2015. This flare is classified as an X2.2-class flare. Planet Earth is shown to scale in the small text box. X-class denotes the most intense flares, while the number provides more information about its strength. An X2 is twice as intense as an X1, an X3 is three times as intense, etc. 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.