Mar. 20, 2009 Scientists at Queen's University have made a finding that will help us to understand more about the turbulent solar weather and its effect on our planet. Along with scientists at the University of Sheffield and California State University, the researchers have detected giant twisting waves in the lower atmosphere of the Sun.
The discovery sheds some light on why the Sun's corona, the region around the Sun, has a much higher temperature than its surface - something that has always puzzled scientists.
The surface of the sun, known as the photosphere, can reach temperatures of 5,000 degrees. To many it would seem logical that the temperature would lower further away from the sun. But, the outer atmosphere, known as the corona, has been shown to reach temperatures of over a million degrees.
The recent discovery by the scientists, published March 20 in the journal Science, has revealed the existence of a new breed of solar wave, called the Alfvén wave. This solar wave has been shown to transport energy into the Corona or outer layer.
The waves have been named after Hannes Alfvén who in 1942 received a Nobel Prize for his work in the area. He suggested the existence of the waves but no hard evidence was ever produced, until recently, when Professor Mihalis Mathioudakis and Dr David Jess of Queen's, made the discovery using the Swedish Solar Telescope in the Canary Islands.
The new findings reveal how the waves carry heat and why this happens. The unique magnetic oscillations spread upward from the solar surface to the Sun's corona with an average speed of 20km per second, carrying enough energy to heat the plasma to more than a few million degrees.
Professor Mihalis Mathioudakis, leader of the Queen's University Solar Group, said: "Understanding solar activity and its influence on the Earth's climate is of paramount importance for human kind. The Sun is not as quiet as many people think.
"The solar corona, visible from Earth only during a total solar eclipse, is a very dynamic environment which can erupt suddenly, releasing more energy than ten billion atomic bombs. Our study makes a major advancement in the understanding of how the million-degree corona manages to achieve this feat."
Dr David Jess, from Queen's University Belfast and lead author of the paper written on the discovery said: "Often, waves can be visualized by the rippling of water when a stone is dropped into a pond, or by the motions of a guitar string when plucked.
"Alfvén waves though cannot be seen so easily. In fact, they are completely invisible to the naked eye. Only by examining the motions of structures and their corresponding velocities in the Sun's turbulent atmosphere could we find, for the first time, the presence of these elusive Alfvén waves."
Professor Robert von Fay-Siebenburgen from the University of Sheffield's Department of Applied Mathematics, said: "The heat was on to find evidence for the existence of Alfvén waves. International space agencies have invested considerable resources trying to find purely magnetic oscillations of plasmas in space, particularly in the Sun. These waves, once detected, can be used to determine the physical conditions in the invisible regions of the Sun and other stars."
Professor Keith Mason, CEO of the Science and technology Facilities Council (STFC), who funded the work said: "These are extremely interesting results. Understanding the processes of our Sun is incredibly important as it provides the energy which allows life to exist on Earth and can affect our planet in many different ways. This new finding of magnetic waves in the Sun's lower atmosphere brings us closer to understanding its complex workings and its future effects on the Earth's atmosphere."
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- David B. Jess, Mihalis Mathioudakis, Robert Erdélyi, Philip J. Crockett, Francis P. Keenan, and Damian J. Christian. Alfven Waves in the Lower Solar Atmosphere. Science, 2009; 323 (5921): 1582 DOI: 10.1126/science.1168680
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