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Science 7 January 2005:
Vol. 307. no. 5706, pp. 51 - 53
DOI: 10.1126/science.1105460
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Perspectives

Also see the archival list of Science's Compass: Enhanced Perspectives

ASTRONOMY:
Enhanced: How Is the Solar Corona Heated?

Robert W. Walsh

The outer atmosphere of our Sun (the corona) is a tenuous, million-degree plasma environment. Given that the corona lies above the much cooler photosphere and chromosphere, some unknown energy source must be depositing extra heat into this region. In his Perspective, Walsh reviews recent progress toward identifying this additional source. It is now believed that the magnetic field that permeates the corona is the source of the heating; the challenge is to determine how that energy can be extracted. Theoretical modeling and the latest space-based observations suggest two possible coronal heating mechanisms: Energy is released either through the dissipation of magnetohydrodynamic waves or by numerous small-scale electric current bursts.

The author is in the Department of Physics, Astronomy, and Mathematics, University of Central Lancashire, Preston, Lancashire PR1 2HE, UK. E-mail: rwwalsh{at}uclan.ac.uk

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