Solar flares typically exhibit a rapid increase of X-ray and ultraviolet emissions to 10100 times their normal level. The increase takes place in tens of seconds. A slower but closely related increase is also seen in radio waves of centimeter wavelengths, and some flares also produce powerful bursts in meter wavelengths. The rapid initial rise is followed by a period of decreasing emissions that may last several hours.
Solar flares were for a long time associated with
A large flare may cover a billion sq km (386,000,000 sq mi) of the Sun's surface.
The total energy involved in radiations, relativistic particles, and thermal
plasma from a large flare may reach 10 to the 32d power
Bibliography: Culhane, J. L., and Jordan, C., eds., The Physics of Solar Flares (1992); De Cicco, Dennis, "Solar Activity on the Upswing," Sky & Telescope, February 1998; "Don't Blame Solar Flares," Sky & Telescope, June 1994; Hill, R. E., "Flares!," Astronomy, February 1992; Phillips, K. J. H., Guide to the Sun (1995); Somov, Boris V., Physical Processes in Solar Flares (1992).