The intensity of the explosion determines what classification the flare belongs to. The most powerful are X-class flares, followed by M-, C- and B-class; A-class flares are the smallest.
We were suppose to have an outburst of solar activity, said we may have interruptions of some services, the big flares can cause electronic and magnetic abnormalities on earth.
“To expect defeat is nine-tenths of defeat itself. It becomes a self-fulfilling prophecy. It is best to plan for all eventualities then believe in success, and only cross the failure bridge if you come to it." Francis Marion - The Swamp Fox