MHD Waves in Coronal Holes

Abstract

This chapter reviews the observations of magnetohydrodynamic (MHD) waves in coronal holes focusing primarily on progress made in the past few years. It also discusses on the new evidences of wave damping and highlights how such observations can be used to probe coronal conditions through seismology. Numerous observations, using imaging and spectroscopic techniques, have revealed the presence of different MHD waves in these structures that can be categorized into compressive and incompressive waves. One of the most desirable characteristics of MHD wave observations in the solar atmosphere, is their dissipation. The energy carried by these waves has to be deposited at appropriate heights to facilitate coronal heating and solar wind acceleration. It turned out that the compressive waves are easy to dissipate with the conventional physical mechanisms whereas the incompressive waves require some special conditions.