MHD waves and instabilities in non-uniform media: Theory and applications

MHD waves in non-uniform media are considered. Applications to the earth’s magnetosphere and the solar atmosphere are examined. The first part mainly deals with different types of wave–flow interactions. The concepts of wave energy and energy flux are applied to analyze the transfer of energy through the media in which the waves propagate. In the second part, theoretical and observational aspects of MHD waves in solar coronal structures are discussed. The emphasis is on standing acoustic waves in coronal loops recently detected by SoHO/SUMER. A new method is proposed for the determination of physical parameters in loop structures. The advantage of the new diagnostic method is that it does not rely on the presence of any particular types of (coherent) waves.