Solar Flare - Classification

Classification

Solar flares are classified as A, B, C, M or X according to the peak flux (in watts per square metre, W/m2) of 100 to 800 picometre X-rays near Earth, as measured on the GOES spacecraft.

Classification	Peak Flux Range at 100-800 picometre
	(Watts/square metre)
A	< 10−7
B	10−7 - 10−6
C	10−6 - 10−5
M	10−5 - 10−4
X	> 10−4

Within a class there is a linear scale from 1 to 9.n (apart from X), so an X2 flare is twice as powerful as an X1 flare, and is four times more powerful than an M5 flare. X class flares up to at least X28 have been recorded.(see below)