Spectral line width decrease in the solar corona: resonant energy conversion from Alfvén to acoustic waves
Abstract
Context: .Observations reveal an increase with height of the line width of several coronal spectral lines probably caused by outwardly propagating Alfvén waves. However, the spectral line width sometimes shows a sudden decrease at a height ~0.1-0.2 R⊙, where the ratio of sound to Alfvén speeds may approach unity.
Aims: .To explain the observed line width reduction in terms of the energy conversion from Alfvén to another type of wave motion.
Methods: .Weakly non-linear wave-wave interaction in ideal MHD.
Results: .Qualitative analysis shows that the resonant energy conversion from Alfvén to acoustic waves near the region of the corona where the plasma β approaches unity may explain the observed spectral line width reduction.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2006
- DOI:
- 10.1051/0004-6361:20065805
- arXiv:
- arXiv:astro-ph/0703297
- Bibcode:
- 2006A&A...456L..13Z
- Keywords:
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- Sun: corona;
- Sun: oscillations;
- Astrophysics
- E-Print:
- 4 pages, 3 figures