Solar flares are sudden variations in the brightness of a surface region of the Sun. Magnetic energy builds up in the solar atmosphere, above active regions, where sunspots are located. This magnetic energy is suddenly released as radiation across the entire electromagnetic spectrum.
As the magnetic energy is being released, particles such as electrons, protons, and heavy nuclei are heated and accelerated in the solar atmosphere. The energy release is 10 million times greater than the energy release from a volcanic eruption, but less than 10% of the energy emitted by the Sun every second.
Large amounts of matter is ejected into the solar system. If this ejected material is directed towards Earth, satellite and communication systems around the globe could be destroyed. Solar flares also pose a radiation hazard to astronauts in the International Space Station.