LINEAR RESISTIVE MAGNETOHYDRODYNAMIC COMPUTATIONS OF RESONANT ABSORPTION OF ACOUSTIC-OSCILLATIONS IN SUNSPOTS

A numerical study of the resonant absorption of p-modes by sunspots is carried out in linear resistive MHD. The sunspot is idealized as a cylindrical axisymmetric flux tube stratified only in the radial direction and surrounded by a uniform unmagnetized plasma. First, the results of Lou in viscous MHD are reproduced in resistive MHD, and, hence, it is shown that the absorption efficiency is independent of the actual dissipation mechanism. Next, the parameter domain investigated by Lou is substantially enlarged to higher m-values, larger sunspots, and sunspot models with a twisted magnetic field. A parametric study reveals that the efficiency of the absorption mechanism depends significantly on both the equilibrium model and the characteristics of the p-modes. The overall picture resulting from this numerical survey of the relevant parameter domain is that the resonant absorption of p-modes is more efficient in larger sunspots with twisted magnetic fields. This is particularly true for p-modes with higher azimuthal wave numbers.