EFFECTS OF FLOW ON RESONANT ABSORPTION OF MHD WAVES IN VISCOUS MHD

The effect of an equilibrium flow on resonant absorption of linear MHD waves in cylindrical magnetic flux tubes is studied in compressible v iscous MHD. We treat the problem numerically with an application of th e FEM combined with the Galerkin technique. The singularities of the i deal MHD equations are removed by incorporating a dissipative effect, namely the classical viscosity. We show that an equilibrium shear Bow can significantly influence the absorption suffered by the incoming dr iving waves. The presence of an equilibrium flow may therefore be very determinant for resonant absorption. A parametric analysis shows that there are values of the equilibrium velocity field for which the abso rption rate becomes zero, even for rather small velocity shears. We al so found negative absorption of wave power which apparently can be att ributed to the resonant instability found by Hollweg et al. (1990). Fo r other values of the equilibrium flow we find that the resonant absor ption can be strongly enhanced, even up to total absorption of the inc oming wave.