What are solar flares?

          A solar flare is defined as a sudden intense brightening of a small part of the sun’s chromosphere near a sunspot group. The brightness of the flare may be five times that of the associated plage or facula. The flare develops in a matter of a few minutes and may last for several hours. In a large solar flare, tremendous energy to the extent of ergs is released.

          Solar flares occur only as a result of sunspot activity. Practically all sunspots produce some flares but certain spots are much more active. Their source of energy is the magnetic fields surrounding the sunspots.

          Such flares are rarely seen in white light because they are an atmospheric phenomenon, with such low density that they’re transparent. On the other hand, their temperature is so high that in the ultraviolet zone, they may equal the intensity of the entire Sun. However, because the flares are most easily observed in Ha (H-alpha) and because the Ha brightening is an extremely accurate indicator, they can be studied well.

          Solar flares emit ultraviolet radiations and X-rays. They also emit great amount of energetic particles and cosmic rays. The particles travel much slower than the light of the flare and reach the vicinity of Earth a day or two later. They pose a potential radiation hazard to human beings in space. During solar flares, jets of particles known as the solar wind, and strong radio frequency electromagnetic radiations are emitted which disrupt radio communications and cause auroras.

          Flares also produce intense streams of electrons. These travel at about one third of the speed of light.