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Influence of strong self-electric fields on the ion resonance instability in a nonneutral plasma column

1977; AIP Publishing; Volume: 20; Issue: 11 Linguagem: Inglês

10.1063/1.861813

2163-4998

Ronald C. Davidson, Hwan-sup Uhm,

Solar and Space Plasma Dynamics

The influence of strong self-electric fields on the ion resonance instability is examined for a cylindrical nonneutral plasma column immersed in a uniform axial magnetic field B0êz. The analysis is carried out within the framework of a macroscopic cold-fluid model, and electrostatic stability properties are investigated for the case of rectangular electron and ion density profiles. The parameter δ= (2ω2pe/ω2ce) (1−f) is introduced as a convenient measure of the relative strengths of the equilibrium self-electric force and the magnetic force on an electron fluid element. (Here, ω̂pe is the electron plasma frequency, ωce is the electron cyclotron frequency, f=n0i/n0e is the fractional charge neutralization, and δ=1 corresponds to the maximum allowed charge density for radial confinement of the equilibrium configuration.) An important conclusion of this study is that the equilibrium self-electric field can have a large influence on stability behavior. In particular, stability properties for δ≲1 differ substantially from those obtained when δ≪1. Moreover, for nonneutral plasma column with significant charge neutralization, it is found that the fundamental mode (l=1) is not the most unstable mode. Rather, higher harmonic perturbations have larger growth rates. However, in the limiting case where f≪1 and δ≪1, the l=1 mode can have the largest growth rate, which is consistent with the result previously obtained by Levy, Daugherty, and Buneman.