Stability of vortex flows in magnetized plasmas. II. Boltzmann vortices

Abstract

The stability of elliptical vortex flow to the excitation of low-frequency electrostatic drift waves is investigated. It is demonstrated that finite ellipticity of flow drives the secondary instability of drift/drift-acoustic waves. When flow ellipticity is small, certain matching conditions between the rotation frequency and secondary wave frequency are needed for instability to occur. The case of large eccentricity is solved by asymptotic methods and gives a growth rate for the instability that depends logarithmically on eccentricity. Such secondary instability mechanisms can act as a sink of vortex energy (limiting the vortex condensation at the long-wavelength end) and thereby help in our understanding of nonlinear saturation of low-frequency instabilities