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Solar Flares

15 October 2010

At http://wattsupwiththat.com/2010/10/15/new-ideas-total-solar-irradiance-and-flares/ there is a post on a paper concerning solar flares – which are sudden releases of energy from the Sun. They are in some way connected to the magnetic field breaking and reconnecting – it is thought. The temperatures of solar flares can soar to millions of degrees as the particles accelerate – and much of the radiation is emitted as X-rays. Or rather, it was thought that X-rays were the major component of the radiation as X-rays and extreme ultra-violet wavelengths were used to image and study the flares, and naturally showed up as the dominant component. It is very difficult to observe and therefore analyse in visible light.

Between 1996 and 2007 there were some 20,000 flares, and four of these were very big. A French research project in Orleans has analysed the X-ray data aquired by American space satellites and they have found a significant peak in solar irradiance during flare episodes – some 100 times greater than the energy flares radiate in X-rays. Therefore, it would seem X-rays only contribute a fraction of overall output of radiation during such events.

This may impact on climate models which may underestimate the ability of solar flares to affect the atmosphere of the earth. However, more importantly, when astronomers target distant stars, many of which are far more active than our Sun and emit powerful flares, they would have been under-estimating the amount of energy being released.

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