a sudden, short-lived increase of intensity in the light of the sun, usually near sunspots, often accompanied by a large increase in cosmic rays, X-rays, etc. and by resultant magnetic storms
See solar flare in American Heritage Dictionary 4
noun
A sudden eruption of magnetic energy released on or near the surface of the sun, usually associated with sunspots and accompanied by bursts of electromagnetic radiation and particles. Ultraviolet and x-ray radiation from solar flares often induce electromagnetic disturbances in the earth's atmosphere.