Formation of nonquasineutral vortex plasma structures with a zero net current
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INEAR PHENOMENA
Formation of Nonquasineutral Vortex Plasma Structures with a Zero Net Current A. V. Gordeev Russian Research Centre Kurchatov Institute, pl. Kurchatova 1, Moscow, 123182 Russia Received March 16, 2006; in final form, April 17, 2006
Abstract—A nonquasineutral vortex structure with a zero net current is described that arises as a result of electron drift in crossed magnetic and electric fields, the latter being produced by charge separation on a spatial scale of about the magnetic Debye radius rB = |B |/(4πene). In such a structure with a radius of r ~ rB, the magnetic field is maintained by a drift current on the order of the electron Alfvén current JAe = mec3/(2e) and can become as strong as B mec2/(er). Estimates show that, in a plasma with a density of ne = 1021–1023 cm–3 and –1
with nonzero electron vorticity driven by high-power laser radiation on a time scale on the order of ω pe , magnetic fields with a strength of B ~ 108–109 G are generated on micron and submicron scales. The system with closed current that is considered in the present paper can also serve as a model of hot spots in the channel of a Z-pinch. PACS numbers: 52.25.Xz, 52.30.-q, 52.30.Ex, 52.55.-s DOI: 10.1134/S1063780X06110067
1. In recent years, investigations have been carried out of nonquasineutral current structures whose size varies from a few microns in pinches to billions of kilometers in cosmic space and in which charges are separated on spatial scales of about the magnetic Debye radius rB = B/(4πene) and an electric field is generated due to the Hall effect—the factors that set electrons into relativistic drift motion [1–3]. An important feature of the resulting quasi-equilibrium is the onset of crossed electric and magnetic fields, |E | ~ |B |. Such structures, which are relatively stable current-carrying vortex formations, can arise at high energy input in plasmas irradiated by high-power laser pulses, as well as in Z-pinches. It is known [4, 5] that powerful laser pulses can accelerate ions to high energies. Their acceleration, however, cannot be explained by thermal effects and is attributed to charge separation and Coulomb explosion. At the same time, the structures considered in [1–3], namely, those resulting from the generation of strong electric and magnetic fields on short spatial scales, can provide efficient ion acceleration, and it should be stressed that there is a coupling between charge separation effects and the generation of strong quasistatic magnetic fields. Experimental evidence has recently been obtained on the generation of strong quasistatic magnetic fields in a plasma irradiated by laser pulses, which is accompanied by ion acceleration [6–9]. Such ion acceleration also occurs at hot spots in Z-pinches [10]. In this case, the ions are accelerated to energies of a few hundred kiloelectronvolts. Vortex structures in the relevant experiments still cannot be revealed by existing diagnostic techniques but they are well captured in
two-dimensional simulations [11]. It should also be noted that com
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