The effects of an equilibrium ow in the internal regions of the Sun are stu
died on the damping of 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 horizontally unidirectional though verticall
y inhomogeneous magnetic field, while the lower part, representing the sub-
photospheric polytropic region, is in a steady equilibrium state. The stead
y state sub-surface region can be considered as a first approximation of dy
namic motions (e.g., differential rotation, sub-surface flows, meridional f
lows, convective motion, etc.).
The frequencies and the line-widths of eigenmodes are affected by sub-surfa
ce ow and atmospheric magnetic fields. A key contribution to the effects co
mes from the universal mechanism of resonant absorption. When both atmosphe
ric magnetic field and sub-surface flows are present, a complex picture of
competition between these two effects is found. The theoretically predicted
frequency shifts in a steady state show promise of explaining the observed
effects. Changes in damping of f- and p-modes caused by changes (e.g. cycl
ic, if any) of steady state flows are predicted.