Solar flares

A solar flare is a sudden and explosive release of energy in the solar atmosphere. This energy is released as particle acceleration, plasma heating and dramatically enhanced radiation.They may last for a minute to several hours.

NOAA AR 8100 produced an X-class flare on Monday, 4th November 1997 This was the first proton event of the current solar cycle. You can see the flare accompanied by a coronal wave in the EIT movie.The flare is the bright flash in the bottom right hand corner. The wave that follows is a dark front that moves quickly away from the flare site. This movie was taken using the Fe XII (195 Å) filter of the Extreme Ultraviolet Imaging Telescope (EIT) onboard the ESA-NASA SOHO spacecraft. Features that look bright in this image are at a temperature of approximately 1.5 million degrees. Images courtesy of SOHO/EIT consortium.

See this movie at higher resolution here! (2.06MB)

A solar flare dramatically enhances the amount of ultraviolet radiation reaching the Earth. This leads to expansion of the upper parts of the Earth's atmosphere. This is an important space weather effect for satellite operators controlling satellites in low Earth orbit. These satellites can suddenly find that the atmosphere is more dense than expected at their orbit. The increased density leads to atmopsheric drag and may reduce the satellite's lifetime if appropriate corrections cannot be made.

Accelerated flare particles are also important for space weather. They are able to escape into interplanetary space where they can propagate, be re-accelerated and finally reach the terrestrial orbit where they .may cause damage to delicate satellite electronics. In extreme cases, these particles may also pose a threat to astronauts onboard the orbiting International Space Station. There is also some research to indicate that aircrew flying frequently at high altitude and on long-haul flights might receive a radiation dose equivalent to several chest X-rays due to the arrival at the Earth of energetic flare particles.

Solar Activity

Coronal Mass Ejections