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Science 20 March 2009:
Vol. 323. no. 5921, pp. 1582 - 1585
DOI: 10.1126/science.1168680
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Reports

Alfvén Waves in the Lower Solar Atmosphere

David B. Jess,1,2* Mihalis Mathioudakis,1 Robert Erdélyi,3 Philip J. Crockett,1 Francis P. Keenan,1 Damian J. Christian4

The flow of energy through the solar atmosphere and the heating of the Sun's outer regions are still not understood. Here, we report the detection of oscillatory phenomena associated with a large bright-point group that is 430,000 square kilometers in area and located near the solar disk center. 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. 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. The energy flux associated with this wave mode is sufficient to heat the solar corona.

1 Astrophysics Research Centre, School of Mathematics and Physics, Queen's University, Belfast, BT7 1NN, Northern Ireland, UK.
2 Solar Physics Laboratory, NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771, USA.
3 Solar Physics and Space Plasma Research Centre, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, England, UK.
4 Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff Street, Northridge, CA 91330, USA.

* To whom correspondence should be addressed. E-mail: d.jess{at}qub.ac.uk

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Science. ISSN 0036-8075 (print), 1095-9203 (online)