Phase finite time singularity: On the dissolution of a surface MHD eigenmode to the Alfvén continuum

Abstract

Phase mixing is a general mechanism of collisionless damping in magnetized plasmas. In a MHD model, the carrier of phase mixing is the Alfvén wave continuum, which is driven by the plasma inhomogeneity. In this work, we study the non-resonant conversion of a surface MHD eigenmode to the Alfvén continuum. It is shown that the finite-time-singularity of the phase of the surface mode can smear its periodic oscillation and induces the excitation of the local Alfvén waves. This type of mode conversion would enhance the collisionless dissipation of the surface eigenmode, i.e., accelerating its dissolution to the Alfvén continuum. The non-resonant mode conversion and damping mechanism explored here have potential applications to understand the physics of collisionless dissipation of various eigenmodes in magnetized plasmas.