부산대학교 도서관

Summary: ``Evolution of three-dimensional magnetohydrodynamic (MHD)waves [fast magnetosonic (FMW), slow magnetosonic (SMW) and Alfvénwaves] is studied in unbounded parallel flows with uniform velocityshear and uniform magnetic field directed along the flow. The energy exchange between the MHD waves and background flow isexplored. This process is noticeably different for each type of waveand is characterized by the unusual (algebraic) behavior of the linearamplification processes. Another novelty is shown in the wave linearevolution process---the coupling of MHD waves and their mutualtransformations are originated in a limited time interval for a widerange of system (flow and waves) parameters. Significanttransformation of Alfvén waves into FMW may take place (depending onthe parameters of the system) if the former have been initiallygenerated in shear flow. It is possible to derive these results byemploying the nonmodal linear approach which has been extensively usedin the study of evolution of perturbations in shear flows since thebeginning of the 1990s. The change in the understanding of flowturbulence due to the coupling of the MHD modes is discussed. Namely,the usual consideration of Alfvén wave turbulence alone in someastrophysical flows is not always sufficient for a completeanalysis---not only should Alfvén waves be `ingredients' ofturbulence, but magnetosonic waves, as well. In this case MHDturbulence should be of a `mixed' type.''