The simple version of Solar flare.

A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Sun's atmosphere.

A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other eruptive solar phenomena. The occurrence of solar flares varies with the 11-year solar cycle.