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Astron. Astrophys. 337, L9-L12 (1998)


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Letter to the Editor

On a source of Alfvén waves heating the solar corona

Alexander Ruzmaikin 1 and Mitchell A. Berger 2

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA (e-mail: aruzmaikin@jplsp.jpl.nasa.gov)
2 Department of Mathematics, University College London, London, WC1E 6BT, UK (e-mail: mberger@math.ucl.ac.uk)

Received 29 June 1998 / Accepted 14 July 1998

Abstract

Studies of the origin of coronal heating and acceleration of the solar wind invoke high-frequency Alfvén waves. Here we suggest a source for such waves associated with twisted magnetic loops emerging on the solar surface and reconnecting with the open field. We identify the loops with the ephemeral regions (small-scale bipoles) observed by ground-based instruments and by SOHO. To characterize the loops we employ the concept of a minimum energy state for topologically complex fields. Emerging loops release energy relaxing to the minimum state. Relaxation along the minimum state-due to a competition between footpoint twisting by photospheric motions and reconnections inside the loops- releases blinks of energy into the solar atmosphere. We estimate the power released and the range of wave frequencies.

Key words: Solar corona heating: magnetic fields

Send offprint requests to: A. Ruzmaikin

© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998

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