The X3 Flare of 2002 July 15

An X3-class flare occurred on 2002 July 15 with white-light emission and a complex filament eruption. Observations were made in the optical continuum, Hα, UV continuum, microwave, and soft X-rays, as well as with high-cadence longitudinal magnetograms. Within the preflare phase, intense heating is observed accompanying upward motion of the filament. At the onset of the impulsive phase, filament Doppler acceleration is increased from -1.5 to -7.0 km s^-2. Flare impulsive emission is double-peaked, possibly corresponding to two magnetic reconnection events: the first occurs above the active region in the corona, while the second takes place in a thin current sheet underneath the eruptive filament. It is probable that a twisted helical flux rope, seen in C IV TRACE images, is formed during the second reconnection. The energy released by the white-light flare is ~10³³ ergs and dominates the flare emission spectra. Within the flare impulsive phase, the emission profiles show both abrupt and gradual components in white light, UV, and Hα. These variations are independently reflected in the transverse motions of flare kernels: the abrupt emission phase corresponds to a rapid kernel motion, while the gradual phase corresponds to a more modest kernel motion.