On Alfvén wave damping in polar coronal holes

Abstract

We reexamine quantitatively the linear resistive and viscous damping of Alfven waves propagating in solar coronal holes, using recently reported observational data on the plasma density and temperature there as well as taking into account the magnetic field spreading inside the coronal hole. It is found that the latter effect results in a drastic reduction of the wave’s dissipation length, thus making linear dissipation a viable mechanism of plasma heating in coronal holes. Some simple estimates related to the reflection and trapping of Alfven waves have been also made, which show that this effect is more likely to take place under strong magnetic field relevant to the maximum phase of the solar activity cycle.