Degenerate mixing of plasma waves on cold, magnetized single-species plasmas

作者：Anderson M W^*; O'Neil T M; Dubin D H E; Gould R W

来源：Physics of Plasmas, 2011, 18(10): 102113.

DOI：10.1063/1.3646922

• damping
• dispersion relations
• mixing
• numerical analysis
• perturbation techniques
• plasma instability
• plasma magnetohydrodynamic waves
• viscosity

In the cold-fluid dispersion relation omega=omega(p)/[1+(k(perpendicular to)/k(z))(2)](1/2) for Trivelpiece-Gould waves on an infinitely long magnetized plasma cylinder, the transverse and axial wavenumbers appear only in the combination k(perpendicular to)/k(z). As a result, for any frequency omega <omega(p), there are infinitely many degenerate waves, all having the same value of k(perpendicular to)/k(z). On a cold finite-length plasma column, these degenerate waves reflect into one another at the ends; thus, each standing-wave normal mode of the bounded plasma is a mixture of many degenerate waves, not a single standing wave as is often assumed. A striking feature of the many-wave modes is that the short-wavelength waves often add constructively along resonance cones given by dz/dr= +/-(omega(2)(p)/omega(2) - 1)(1/2). Also, the presence of short wavelengths in the admixture for a predominantly long-wavelength mode enhances the viscous damping beyond what the single-wave approximation would predict. Here, numerical solutions are obtained for modes of a cylindrical plasma column with rounded ends. Exploiting the fact that the modes of a spheroidal plasma are known analytically (the Dubin modes), a perturbation analysis is used to investigate the mixing of low-order, nearly degenerate Dubin modes caused by small deformations of a plasma spheroid.

• 出版日期2011-10