Action-angle representation of waves and instabilities in flowing plasmas

Hirota, Makoto

Stabilization/destabilization of plasma by flow is a key issue inrecent fusion research and astrophysics. In order to gain a general understanding of this problem, it is informative to consider the modal energy (i.e., the energy of eigenmode) in the context of the stability theory of Hamiltonian mechanics, in which the negative energy mode is associated with the source of instability. In this work, we have developed a new method for transforming general linear perturbations to the action-angle variables, which enables us to evaluate the modal energy not only for each eigenmode, but also for acontinuum mode. Our method serves to provide a Hamiltonian interpretation of various instabilities in flowing plasmas.