Dissipation of slow magnetosonic waves in coronal plumes

Recently, slow magnetosonic waves were identified in polar plumes, at heigh ts up to about 1.2 R. using the Extreme Ultraviolet Imaging Telescope (EIT) observations of quasi-periodic EUV intensity fluctuations, and higher in t he corona using the Ultraviolet Coronagraph Spectrometer (UVCS) white-light channel. First, we derive the linear dispersion relation for the slow wave s in the viscous plasma. Next, we derive and solve an evolutionary equation of the Burgers type for the slow waves, incorporating the effects of radia l stratification, quadratic nonlinearity, and viscosity. Finally, we model the propagation and dissipation of slow magnetosonic waves in polar plumes using one-dimensional and two-dimensional MHD codes in spherical geometry. The waves are launched at the base of the corona with a monochromatic sourc e. We find that the slow waves nonlinearly steepen as they propagate away f rom the Sun into the solar wind. The nonlinear steepening of the waves lead s to enhanced dissipation owing to compressive viscosity at the wave fronts . The efficient dissipation of the slow wave by compressive viscosity leads to damping of the waves within the first solar radii above the surface. We investigate the parametric dependence of the wave properties.