X-Ray Flare Class

In solar-terrestrial terms, rank of a flare based on its X-ray energy output. Flares are classified by the order of magnitude of the peak burst intensity (I) measured at the earth in the 1 to 8 angstrom band as follows:

Class	Intensity (in Watts/m2)
B	I < 10-6
C	10-6 <= I < 10-5
M	10-5 <= I < 10-4
X	I >= 10-4