A plasma source driven predator-prey like mechanism as a potential cause of spiraling intermittencies in linear plasma devices
VELA VELA, LUIS ERNESTO
PHYSICS OF PLASMAS
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Three-dimensional global drift fluid simulations are carried out to analyze coherent plasma structures appearing in the NAGDIS-II linear device (nagoya divertor plasma Simulator-II). The numerical simulations reproduce several features of the intermittent spiraling structures observed, for instance, statistical properties, rotation frequency, and the frequency of plasma expulsion. The detailed inspection of the three-dimensional plasma dynamics allows to identify the key mechanism behind the formation of these intermittent events. The resistive coupling between electron pressure and parallel electric field in the plasma source region gives rise to a quasilinear predator-prey like dynamics where the axisymmetric mode represents the prey and the spiraling structure with low azimuthal mode number represents the predator. This interpretation is confirmed by a reduced one-dimensional quasilinear model derived on the basis of the findings in the full three-dimensional simulations. The dominant dynamics reveals certain similarities to the classical Lotka-Volterra cycle. © 2014 Euratom.
azimuthal mode number; electron pressures; full three-dimensional; parallel electric fields; quasi-linear model; resistive couplings; rotation frequencies; statistical properties; dynamics; plasma diagnostics; three dimensional; plasma sources