| Issue |
A&A
Volume 440, Number 2, September III 2005
|
|
|---|---|---|
| Page(s) | L29 - L32 | |
| Section | Letters | |
| DOI | https://doi.org/10.1051/0004-6361:200500155 | |
| Published online | 01 September 2005 | |
Letter to the Editor
Flows along penumbral flux tubes in sunspots
Instability of super-Alfvénic, serpentine solutions
Department of Mechanical Engineering and Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171, USA e-mail: thomas@me.rochester.edu
Received:
9
May
2005
Accepted:
9
July
2005
The super-Alfvénic, undulating “sea-serpent” flow configurations along thin magnetic flux tubes, proposed by Schlichenmaier (2002, Astron. Nachr., 323, 303; 2003, ASP Conf. Ser., 286, 24) to explain both the Evershed flow and moving penumbral grains in a sunspot, are shown to be gravitationally unstable. Any undulations that occur for super-Alfvénic flow speeds will form preferentially in a horizontal plane and hence will not explain Evershed downflows or outward-moving penumbral grains. Sub-Alfvénic, arched flow configurations, on the other hand, are gravitationally stable.
Key words: sunspots / Sun: magnetic fields / magnetohydrodynamics (MHD)
© ESO, 2005
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