The single‐particle and collective descriptions of the anomalous Doppler resonance and the role of ion dynamics

• Published in: Physics of fluids (1994) 1986-12, Vol.29 (12), p.4040-4046
• Main Authors: Dendy, R. O., Lashmore‐Davies, C. N., Montes, A.
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Waves, oscillations, and instabilities in plasmas and intense beams
• ISSN: 0031-9171; 1070-6631; 2163-4998
• DOI: 10.1063/1.865746

The connection between three aspects—single‐particle, beam, and continuous velocity distribution—of the anomalous Doppler effect are investigated. The key quantity is the power Re(j  ⋅  E*) dissipated by electrostatic waves interacting with a non‐Maxwellian electron velocity distribution. Its spatial components describe energy flows that are the counterparts in classical electrodynamics to the quantum properties of the single‐particle anomalous Doppler effect. A complete plasma physics treatment requires the inclusion of ion dynamics. Examination of the large‐k region of wavenumber space—in contrast to the well‐known small‐k region—shows that ion Landau damping is important in stabilizing plasmas for which the electron velocity distribution considered alone is destabilizing. Finally, by choosing simple models for the superthermal electron velocity distribution, general features of the instability, and those specific to particular tail models, are identified analytically and numerically.