<P> Flares occur when sped up charged particles, mainly electrons, interact with the plasma medium . Scientific research suggests that the phenomenon of magnetic reconnection leads to this copious acceleration of charged particles . On the Sun, magnetic reconnection may happen on solar arcades--a series of closely occurring loops of magnetic lines of force . These lines of force quickly reconnect into a low arcade of loops leaving a helix of magnetic field unconnected to the rest of the arcade . The sudden release of energy in this reconnection is the origin of the particle acceleration . The unconnected magnetic helical field and the material that it contains may violently expand outwards forming a coronal mass ejection . This also explains why solar flares typically erupt from what are known as the active regions on the Sun where magnetic fields are much stronger on average . </P> <P> Although there is a general agreement on the source of a flare's energy, the mechanisms involved are still not well known . It is not clear how the magnetic energy is transformed into the particle kinetic energy, nor is it known how some particles can accelerated to the GeV range (10 electron volt) and beyond . There are also some inconsistencies regarding the total number of accelerated particles, which sometimes seems to be greater than the total number in the coronal loop . Scientists are unable to forecast flares, even to this day . </P> <P> The classification system for solar flares uses the letters A, B, C, M or X, according to the peak flux in watts per square metre (W / m) of X-rays with wavelengths 100 to 800 picometre, as measured at the Earth's orbital distance by the GOES spacecraft . </P> <Table> <Tr> <Th> Classification </Th> <Th> Peak Flux Range at 100 - 800 picometre </Th> </Tr> <Tr> <Th> </Th> <Th> (watts / square metre) </Th> </Tr> <Tr> <Td> </Td> <Td> <10 </Td> </Tr> <Tr> <Td> </Td> <Td> 10--10 </Td> </Tr> <Tr> <Td> </Td> <Td> 10--10 </Td> </Tr> <Tr> <Td> </Td> <Td> 10--10 </Td> </Tr> <Tr> <Td> X </Td> <Td>> 10 </Td> </Tr> </Table>

The energy released by a single solar flare