Influence of equilibrium flows and the atmospheric magnetic field on solar oscillation modes

The competing effects of an atmospheric magnetic field and an equilibrium Row in the internal regions of the Sun are studied on the helioseismic f- and p-modes. The Sun is modeled as a multi-layered plasma, where the upper parts, representing the chromosphere and corona, are embedded in a unidirectional though inhomogeneous magnetic field, meanwhile the lower part, representing the sub-photospheric polytropic region, is in a steady equilibrium state. The steady state sub-surface region can be considered as a first approximation of dynamic motions (e.g., convective motion, differential rotation, subsurface Rows, meridional Rows, etc.). The obtained frequency shifts of the different eigenmodes are associated with flow and magnetic effects. We also found damping of the eigenfrequencies which apparently can be associated with the universal mechanism of resonant absorption. Resonant absorption (already known as a viable heating mechanism in the solar corona) is present due to inhomogeneities in the atmosphere which give rise to Alfven and slow continua. Damping of helioseismic modes occurs when the modes are coupled into these continua. When both atmospheric magnetic field and sub-surface flows are present, a complex picture of competition of these two effects is found. The theoretically predicted frequency shifts in a steady state are in excellent agreement with the observed values. For related works see also the papers by Erdelyi & Taroyan and Varga & Erdelyi in the present Volume.