First X-Class Solar Flares of 2013 – NASA
On May 12-13 the Sun erupted with an X1.7-class and an X2.8-class flare as well as two coronal mass ejections, or CMEs. Solar flares are classified as A, B, C, M or X according to the peak flux.
|Classification||Peak Flux Range at 100-800 picometre|
|B||10−7 – 10−6|
|C||10−6 – 10−5|
|M||10−5 – 10−4|