First X-class solar flare of 2013May 13, 2013
(Phys.org) —On May 12, 2013, the sun emitted a significant solar flare, peaking at 10 p.m. EDT. This flare is classified as an X1.7, making it the first X-class flare of 2013. The flare was also associated with another solar phenomenon, called a coronal mass ejection (CME) that can send solar material out into space. This CME was not Earth-directed.
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 – the radio blackout associated with this flare has since subsided.
"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.
This flare erupted from an active region just out of sight over the left side of the sun, a region that will soon rotate into view. This region has produced two smaller M-class flares as well