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VIRTUALISATION Physicists observe waves that heat Sun’s corona
VIRTUALISATION Physicists observe waves that heat Sun’s corona | Physicists observe waves that heat Sun’s corona |
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| by William Atkins | |
| Tuesday, 21 April 2009 | |
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The results of their research were published in the March 20, 2009 issue of Science under the title “Alfvén Waves in the Lower Solar Atmosphere.” The authors studying this phenomenon include David B. Jess of the Astrophysics Research Center at Queen’s University in Belfast, Northern Ireland, along with Mihalis Mathioudakis, Robert Erdélyi, Philip J. Crockett, Francis P. Keenan, and Damian J. Christian. They state in the abstract to their paper, “The flow of energy through the solar atmosphere and the heating of the Sun's outer regions are still not understood.” In fact, physicists continue to wonder why the outer atmosphere of the Sun—the corona—is millions of degrees hotter than its interior, usually called the photosphere. Dr. Jess states, “It’s counterintuitive…. When you hold your hands in front of a fire, it’s hottest closest to the flames.” [Science News: “Team spots waves that heat corona” (April 11, 2009, page 12)] The first ever viewing of these magnetic waves heating up the Sun’s cornona included a large bright-point group that was approximately 166,000 square miles (430,000 square kilometers) in area and located near the solar disk center. They state “Wavelet analysis reveals full-width half-maximum oscillations with periodicities ranging from 126 to 700 seconds originating above the bright point and significance levels exceeding 99%. These oscillations, 2.6 kilometers per second in amplitude, are coupled with chromospheric line-of-sight Doppler velocities with an average blue shift of 23 kilometers per second.” And, “A lack of cospatial intensity oscillations and transversal displacements rules out the presence of magneto-acoustic wave modes. The oscillations are a signature of Alfvén waves produced by a torsional twist of ±22 degrees. A phase shift of 180 degrees across the diameter of the bright point suggests that these torsional Alfvén oscillations are induced globally throughout the entire brightening.” Page two concludes. |
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