A typical eruption can release the same amount of energy as millions of 100-megaton hydrogen bombs all exploding at the same time. The energy source for solar flares is the Sun's magnetic field. Whenever the magnetic field around a sunspot group becomes twisted and sheared, like a stretched and twisted rubber band, an explosive release of energy could be just around the corner. Most sunspots come in pairs with a magnetic field that looks somewhat like that of a bar magnet. The energy stored in the twisted magnetic field lines serves as fuel for solar flares and CMEs.
Eruptions occur when the fields rearrange to form a simpler, lower-energy configuration.
Anatomy of a solar flare observed by the Yohkoh Soft X-ray Telescope. The explosive release of energy occurs where the magnetic field is twisted above the sunspot. Click for a larger image . Satellites can be damaged or even destroyed when their electronics are saturated by charged particles from large flares. A large and famous space storm in 1989 induced electrical currents on the ground that caused a failure in the Hydro-Quebec electric power system.