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Numerical simulations of the conversion to Alfven waves in solar active regions | |
Auteur | Khomenko Elena |
Institution | Instituto de Astrofisica de Canarias |
Theme | Solar and stellar modelling |
| Auteur(s) supplémentaire(s) | Paul Cally |
| Institution(s) supplémentaire(s) | School of Mathematical Sciences, Monash University, Australia |
Abstract | Conversion from fast to slow magneto-acoustic waves in solar active regions is relatively well studied both from analytical theories and numerical simulations. But no generalized picture exists so far for conversion from magneto-acoustic to Alfven waves in a three-dimensional situation. Motivated by the recent study of the conversion to Alfven waves by Cally & Goossens (2008), here we attack the problem by means of 2.5D numerical simulations. In our experiment, an acoustic wave of a given frequency and wavenumber is generated below the surface. The magnetic field in the domain is assumed homogeneous and inclined. The efficiency of the conversion to Alfven waves near the layer of equal acoustic and Alfven speeds is measured calculating their energy flux. The particular amplitude and phase relations between the oscillations of magnetic field and velocity help us to demonstrate that the waves produced after the transformation and reaching upper atmosphere are indeed Alfven waves. We study the dependence of the Alfven wave energy flux on the wave frequency, wavenumber, magnetic field strength and orientation. We also investigate the possible influence of the radiative relaxation of oscillations on the conversion rate to Alfven waves. |