NASA has released a video of the X2-class flare of Feb. 15, seen by the Solar Dynamics Observatory, an orbiting spacecraft, in extreme ultraviolet light. The image has been enlarged and superimposed on images from another spacecraft, the Solar and Heliospheric Observatory (SOHO).
The SOHO image is made by a coronagraph, which shows the faint edge of a halo coronal mass ejection as it races away from the Sun -- it is visible as a faint ring of brigter gas. The flare itself is in the lower central part of the solar disc. The video covers about 11 hours.
Flares send bursts of X-rays and charged particles -- mostly protons -- out from the Sun's surface. They are classified according to how powerful they are, as A, B, C, M or X, with X being the most powerful.
The last big solar flare occurred in 2006, and more powerful ones have occurred in 2005 and 2003 as well. The most powerful ever recorded was in 1859 and was sufficiently strong to damage electrical equipment (at the time, telegraph cables).
When solar flares occur airliners that fly in the far northern (or far more rarely, southern) latitudes have to stay in the line of sight of the satellites that connect them to ground stations. GPS Satellites can also be affected.
During such events the Earth's magnetic field gets hit with tons of charged particles that are trapped by it, and form spectacular auroral displays that can reach as far south as the continental U.S.