Benchmarking Fast-to-Alfvén Mode Conversion in a Cold MHD Plasma. II. How to Get Alfvén Waves through the Solar Transition Region
Abstract
Alfvén waves may be difficult to excite at the photosphere due to low-ionization fraction and suffer near-total reflection at the transition region (TR). Yet they are ubiquitous in the corona and heliosphere. To overcome these difficulties, we show that they may instead be generated high in the chromosphere by conversion from reflecting fast magnetohydrodynamic waves, and that Alfvénic TR reflection is greatly reduced if the fast reflection point is within a few scale heights of the TR. The influence of mode conversion on the phase of the reflected fast wave is also explored. This phase can potentially be misinterpreted as a travel speed perturbation with implications for the practical seismic probing of active regions.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 2012
- DOI:
- 10.1088/0004-637X/751/1/31
- arXiv:
- arXiv:1203.3822
- Bibcode:
- 2012ApJ...751...31H
- Keywords:
-
- magnetohydrodynamics: MHD;
- Sun: oscillations;
- sunspots;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 13 pages, 10 figures, accepted by ApJ 17 March 2012