Parametric decay of Alfvén waves at parallel and oblique propagation: Kinetic effects and transverse couplings

摘要

Properties of the parametric decay of Alfvén waves in a kinetic regime is studied by means of 1-D and 2-D hybrid numerical simulations; propagation parallel and oblique with respect to the ambient magnetic field is considered. Consistently with the fluid case, parametric decay instability leads to the damping of the mother wave and the excitation of daughter backward propagating Alfvén waves and forward compressible acoustic modes. The interaction of the excited ion-acoustic fluctuations with ions and the consequent deformation of the particle distribution function are described. We focus on themain new aspects obtained in recentworks; these include the acceleration of proton secondary beams along the magnetic field and the excitation of perpendicular small scales through the decay of oblique propagating mother waves.