The power of solar magnetic tornadoes
A major discovery by a Europe-wide team of researchers is providing answers to one of the puzzles in modern astrophysics – why the atmosphere of a star, like the sun, is considerably hotter than its surface. Solving this heating problem is crucial for understanding the sun, including the generation of the solar wind and its impact on the Earth's atmosphere.
Team member Professor Robertus Erdélyi, Head of the University of Sheffield's Solar Physics and Space Plasma Research Centre, is one of the authors of the paper which was published in Nature in June 2012, 'Magnetic tornadoes as energy channels into the solar corona'.
The team's observation of solar magnetic tornadoes has only been made possible by combining the capabilities of a state-of-the- art, ground-based solar telescope (Swedish 1-m Solar Telescope) with a new solar space telescope (NASA's Solar Dynamics Observatory). The tornado events are rather small details of the sun. They are most visible as rotating structures in the chromosphere, the atmospheric layer between the photosphere (the 'surface') and the corona above. The chromosphere is very difficult to observe.
The tornadoes, which have a magnetic skeleton, exist in the hottest areas of the sun's atmosphere where the temperature is a few million degrees kelvin, thousands of kilometres from the sun's surface. They are also thousands of times larger and more powerful than their earthly counterparts and spin at speeds of more than 6,000mph. They operate in plasma – the fourth known state of matter beside solid, liquid and gas. It is estimated that there are as many as 11,000 of these swirling events above the sun's surface at any one time.
The team used the data from the telescope observations to create 3D-layered sequences of images of the tornadoes. These were then manipulated to simulate the tornadoes' evolution with numerical codes using the magnetic imprints detected by the telescopes, unravelling the fascinating physics of these phenomena.
The team have demonstrated that the tornadoes carry the energy from the energy reservoir below the sun's surface, called the convection zone, to the outer atmosphere in the form of magnetic waves. Professor Erdélyi said, "If we understand how nature heats up magnetised plasmas, like in the tornadoes observed in the sun, one day we may be able to use this process to develop the necessary technology and build devices on Earth that produce clean, green energy. Our collaborative research is an essential leap forward towards unveiling the secrets about an exciting problem in plasma astrophysics."