Propagation of Alfvén waves in shear flows: Nature of driven longitudinal velocity and density fluctuations

Abstract

The nature of driven longitudinal velocity fluctuations and density fluctuations is studied when there is an Alfvén wave propagating in the medium characterized by an inhomogeneous velocity field. A system of governing equations that describes driven fluctuations is obtained and the properties of this system are analyzed. For some circumstances considering general properties of the Alfvén wave, the system allows us to obtain analytical solutions for driven waves that can be compared with ones obtained by numerical integration of the wave interaction equations. It is shown that for the low β plasma, the analytical solutions are in a good agreement with the numerical ones. The natural frequencies of individual wave components (“uncoupled natural frequencies”) are analyzed and how these frequencies are related to the natural frequencies of the coupled system are shown. In the summary, it is discussed where this process can be important. The possible observations in different areas where its signature can be found are outlined.