Ranking of a solar flare is based on its
x-ray output. Flares are classified according to the order of magnitude
of the peak burst intensity (I) measured at the earth in the 0.1 to 0.8
nm wavelength band as follows:
Peak, 0.1 to 0.8 nm band
Class
(Watts/square metre)
B
I < 10-6
C
10-6 I < 10-5
M
10-5 I < 10-4
X
I 10-4
A multiplier is used to indicate the level
within each class. For example: