Strong Viscous Damping of Coronal Alfven Waves

Viscous damping of Alfven waves in the Sun’s corona was historically dismissed using a strict linear assumption of vanishing wave perturbations. This talk presents new findings that the former result only applies to wave amplitudes that are so small as to be of little interest, typically a wave energy of less than 1e-11 of the energy of the background magnetic field. For observed amplitudes, a nonlinear coefficient eta_A = 3 eta_0 (b/B_0)^2 dominates Braginskii viscous dissipation, making viscous damping of coronal Alfven waves around 1e+9 stronger than previously recognised. A preliminary evaluation of viscous dissipation for a polar coronal hole, using observed parameters, indicates that Alfvenic waves with p-mode frequencies deposit a substantial fraction of their energy within half a solar radius of the Sun's surface. This result also holds when viscous damping is saturated at a free-streaming limit. Based on these findings, it appears that the newly discovered viscous damping regime could be significant for coronal heating and/or solar wind acceleration.