Nonlinear evolution of a strongly sheared cross-field plasma flow

Journal Article · Wed Sep 01 00:00:00 EDT 1993 · Physics of Fluids B; (United States)

DOI:https://doi.org/10.1063/1.860653· OSTI ID:6022302

Romero, H; Ganguli, G ^[1]

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1. Space Plasma Branch, Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375-5000 (United States)

A study is presented of the nonlinear evolution of a magnetized plasma in which a localized electron cross-field flow is present. The peak velocity of the flow is denoted by [ital V][sub 0]; [ital L][sub [ital E]] represents the flow's shear scale length; and the regime [rho][sub [ital e]][lt][ital L][sub [ital E]][lt][rho][sub [ital i]] is considered, where [rho][sub [ital i]] and [rho][sub [ital e]] denote the ion and electron Larmor radii, respectively. It is shown that if the shear frequency [omega][sub [ital s]]=[ital V][sub 0]/[ital L][sub [ital E]] is larger than the lower-hybrid frequency, [omega][sub LH], then the system dynamics is dominated by the onset of the electron--ion-hybrid (EIH) mode which leads to the formation of coherent (vortexlike) structures in the electrostatic potential of the ensuing lower-hybrid waves. The wavelength of these structures is on the order of [ital L][sub [ital E]], and correlates well with that predicted by the linear theory of the EIH mode. Since the characteristic wavelength is longer than [rho][sub [ital e]], the corresponding phase velocity is low enough that there results significant direct resonant ion acceleration perpendicular to the confining magnetic field. When [omega][sub [ital s]][gt]3[omega][sub LH], the system exhibits significant anomalous viscosity (typically an order of magnitude larger than that due to Coulomb collisions), which increases as the shear frequency is increased. As [omega][sub [ital s]] is reduced below [omega][sub LH], shear effects are no longer dominant and a smooth transition takes place in which the system dynamics is governed by the short wavelength (on the order of [rho][sub [ital e]]) lower-hybrid drift instability.

• OSTI ID: 6022302
• Journal Information: Physics of Fluids B; (United States), Vol. 5:9; ISSN 0899-8221
• Country of Publication: United States
• Language: English

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY
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