Expert: Philip Stahl - 12/22/2005

Question
Hi,
I would like some information on solar flares. What causes them?  What are the effects? Any other extra inforamtion would be great too.

Thank you.

Answer
Hello.

I don't understand why you didn't receive the original answer to this question, which was sent more than five days ago. Anyway, a truncated version follows (given the original has evidently been lost by the All experts system):

Solar flares are enormous eruptions on the Sun which can equal up to two million megatons in energy release. They can cover an area of many thousands of Earths, though much smaller flares can barely be resolved.

Solar flares can occur when the magnetic tubes or "ropes" that make up sunspots or their associated magnetic fields get very twisted (like a rubber band wound over and over until it has knots) and store magnetic energy as they do so. Eventually, this energy will reach a maximum and the magnetic "rope" will tear - releasing all or much of its
stored energy.

There are many ways the twisting that stores energy can occur, and one of the more common may be rotary motions of the ropes due to being anchored in the Sun's photosphere. Since the Sun is a fluid body- not solid - any motions of it gases (plasma) will twist the sunspot tubes or ropes. If
energy is stored during this process, then it can be released later in the form of a solar flare.

Solar flares are classed according to their energy output - often in the optical case from I to IV (highest energy) or based on x-ray emission class: C, M and X with X the most intense.  We believe the largest combination class flares (e.g. IV-X) are spawned by the greatest release of free magnetic energy stored in sunspot regions.

Solar flares are of great interest, not only as a perplexing and complex physical phenomenon in thier own right, but also because of the their effects on the terrestrial environment. These effects, which are many and varied, include: sudden ionospheric disturbances (SIDs); auroral enhancements, destruction of sensitive electronics (e.g. on satellites),  power outages, and erosion of the ozone layer.

Perhaps the best opportunity to obtain answers on *exactly* what causes flares (and in particular what triggers them) was the Solar Optical Telescope (or SOT) that was scheduled to have been launched in the late 1980s. Unfortunately, budget cuts forced its abandonment - so we still have much work to do, e.g. in terms of precisely locating the origin of the flare energy release site. Once this is done, we can have a detailed, self-consistent solar flare theory.