The sigmoids are made up of many small and distorted layers of strong electric current. When these layers mix it leads to the formation of a strong flame that can be seen and the eruption of a strong magnetic field
Sigmoids are S-shaped structures found in the Sun's outer atmosphere (the corona). They can be seen with an X-ray telescope and are an essential part of events such as solar flares. Now a group of scientists has developed the first model to understand and explain the different stages in the life of the sigmoids.
Prof. Alan Hood and Dr. Vassilis Archontis from the Institute of Mathematics at the University of St. Andrews, Scotland, presented the results of their research at the Space Science Conference held this month at the University of Hertfordshire.
The team led by Hood and Archontis used the Hinode X-ray Space Telescope to get a clear, high-resolution image of the formation and eruption stages of a sigmoid. These observations revealed that the structure of the sigmoid is complex: it is made up of many different and dynamic loops that together form two opposing J-like bundles, or more generally, an S-like structure. They also showed that at the end of its life, the sigmoid produces a fused burst.
Over the years, a series of mathematical and theoretical models have been proposed to explain the nature of the sigmoids, but so far no explanation has been found for the formation of such complex structures, their eruption and decay. The new model holds that sigmoids are made up of lots of small, distorted layers of strong electric current. When these layers mix it leads to the formation of a strong flame that can be seen and the eruption of a strong magnetic field which carries highly energetic particles into interstellar space.
"Sigmoids are used as 'mangers' or 'bulbs' for solar flares. There is a high probability that they will end in a strong eruption and other explosive events. Our models help scientists understand how this happens," says Dr. Archontis.
Prof. Hood adds that these events have real and important consequences for life on Earth, "Sigmoids are among the most interesting things for scientists trying to predict solar eruptions - events that can disrupt telecommunications, damage satellites and affect the functioning of navigation systems."