solar flare

from The American Heritage® Dictionary of the English Language, 5th Edition.

• 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A violent explosion in the Sun's atmosphere.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a sudden eruption of intense high-energy radiation from the sun's surface; associated with sunspots and radio interference