Explosions on the surface of the Sun known as solar flares can have serious consequences on Earth. In the past solar flares have caused power cuts in major cities and last May a flare permanently disabled a $165 million satellite used by 45 million pagers in the US. Now a group of physicists has shown that it might be possible to predict when solar flares will occur by detecting unusual S-shaped patterns called sigmoids - thought to be due to twists in the magnetic field of the Sun - on the solar surface (Geophys. Res. Lett. 26 627).
Richard Canfield and David McKenzie from Montana State University in the US, and Hugh Hudson from the Solar Physics Research Corporation in Japan, analysed two years worth of images from the X-ray satellite Yohkoh. In addition to the link between sigmoids and solar flares, they also confirmed that there was a link between solar flares and sunspot activity.
Several explosions take place on the Sun’s surface every day but only a few point in the direction of the Earth. Previously, the only advance warning about the flares came from the SOHO satellite. However, SOHO could only give a few hours warning at most. The statistical relationship between sigmoids and solar flares can provide warnings days in advance.
