HR: 1340h
AN: SH13A-1162    [Abstracts]
TI: Mode Conversion in Magneto-Atmospheres
AU: * Bogdan, T J
EM: tom@ucar.edu
AF: High Altitude Observatory National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 United States
AU: Carlsson, M
EM: mats.carlsson@astro.uio.no
AF: Institute of Theoretical Astrophysics University of Oslo, P.O. Box 1029 Blindern, Oslo, N-0315 Norway
AU: Hansteen, V
EM: viggo.hansteen@astro.uio.no
AF: Institute of Theoretical Astrophysics University of Oslo, P.O. Box 1029 Blindern, Oslo, N-0315 Norway
AU: Heggland, L
EM: lars.heggland@astro.uio.no
AF: Institute of Theoretical Astrophysics University of Oslo, P.O. Box 1029 Blindern, Oslo, N-0315 Norway
AU: Leer, E
EM: egil.leer@astro.uio.no
AF: Institute of Theoretical Astrophysics University of Oslo, P.O. Box 1029 Blindern, Oslo, N-0315 Norway
AU: McMurry, A D
EM: a.d..mcmurry@astro.uio.no
AF: Institute of Theoretical Astrophysics University of Oslo, P.O. Box 1029 Blindern, Oslo, N-0315 Norway
AU: Stein, R F
EM: steinr@pa.msu.edu
AF: Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-1116 United States
AB: Numerical simulations of wave propagation in a simple magneto-atmosphere are employed to illustrate the complex nature of wave transformation and conversion taking place in solar and stellar atmospheres. An isothermal atmosphere threaded by a potential poloidal magnetic field, and a superposed uniform toroidal field, is treated in a local cartesian approximation. Spatial variations are restricted to the two poloidal dimensions, but the toroidal field ensures that all three MHD waves are present in the simulation. As in our previous purely two-dimensional simulations (Bogdan et al. ApJ 599, 626-60, 2003), mode mixing and transformation take place at surfaces where the magnetic and thermal pressures are equal. In the present case, the upward propagating acoustic-gravity (MAG) wave is converted into roughly equal parts transmitted fast, intermediate (Alfven), and slow magneto-acoustic-gravity waves in passing through this mixing layer. Unlike the fast and slow waves, the Alfven wave is weakly damped, and is able to deposit its energy and momentum in the upper chromosphere and corona. The fast and slow MAG waves are decoupled on either side of mixing layer owing to their disparate propagation speeds. Under certain fortuitous circumstances, the Alfven wave also decouples from the fast and slow MAG waves.
DE: 7507 Chromosphere
DE: 7522 Helioseismology
DE: 7524 Magnetic fields
DE: 7868 Wave/wave interactions
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting