Wavelet characterization of 2D turbulence and intermittency in magnetized electron plasmas

Romé, M.; Chen, S; Maero, G.

doi:10.1088/0963-0252/25/3/035016

Cited by 5 publications

(23 citation statements)

References 63 publications

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“…Here, the conclusions of Refs. [51,52,53,54] are briefly reviewed, and results of new simulations and of the relevant statistical analysis are presented, that corroborate the previous findings. The attention is focused on the role on the late evolution of the system played by initial density fluctuations under the effect of a selected choice of multipolar RF drives, and by different initial conditions in the presence of a given external forcing.…”

Section: Introductionsupporting

confidence: 69%

“…The formation of coherent structures and the evolution of 2D turbulence have been subject of investigation for decades in the fluid dynamics community. In particular, the 2D turbulence in pure electron plasmas has been studied by variational principles [34,31,25], time scaling of the vortices present in the flow [32], statistical techniques [10,49,52]. The statistical theories rely on the presence of global constraints, and usually neglect the details of the early dynamical evolution of the flow.…”

Section: Discussionmentioning

confidence: 99%

“…Analogously to the integral evolution, the enstrophy spectra show similar features for all cases. Moreover, due to the smallness of the vortex patches formed at the end of diocotron instability stage, the difference in spatial scale between the coherent and incoherent parts is less distinguishable, resulting simply in a broadening of the contour ridges instead of a bifurcation 020012-6 structure as more clearly evidenced for the case of free evolution both for annular and spiral configurations [51,52]. In order to investigate complementary or additional information, the wavelet decomposition technique is applied also to the energy distribution (calculated from the density and the electrostatic potential maps).…”

Section: Influence Of Initial Conditions and Drivesmentioning

confidence: 99%

“…The iteration method takes into account the inhomogeneity of the flow [51], i.e., the fact that the vorticity field is nonzero only in a fraction of the analysis domain (in the present case, of the cells of the grid used for the discretization of the system in the PIC code). In general, the coherent component of the flow can be reconstructed using only a small fraction (typically < 2 %) of the wavelet coefficients, but it contains the greatest part (typically > 95 %) of the "energy of the signal", i.e., the enstrophy Z ≡ (1/2) rdrdθζ exception of the total number of particles), therefore including Z, as observed both in experiments and numerical simulations [21,48,52]. Depending on the initial density distribution, the evolution of the flow may be either dominated by the presence of persistent vortices (and possibly the formation of vortex crystal-like states), or by a higher turbulence level.…”

Section: Influence Of Initial Conditions and Drivesmentioning

confidence: 99%

“…In order to identify the parameters playing a major role in the early dynamics of the system, the results of numerical simulations of the 2D electron plasma dynamics starting from particular classes of initial conditions (specifically, annular and spiral distributions) have been analyzed in Refs. [51,52] in the case of free evolution and in Refs. [53,54] in the case of forced turbulence, respectively.…”

Section: Introductionmentioning

confidence: 96%

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Coherent structures and turbulence evolution in magnetized non-neutral plasmas

Romé

Chen²,

Maero

2018

AIP Conference Proceedings

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The evolution of turbulence of a magnetized pure electron plasma confined in a Penning-Malmberg trap is investigated by means of a two-dimensional particle-in-cell numerical code. The transverse plasma dynamics is studied both in the case of free evolution and under the influence of non-axisymmetric, multipolar radio-frequency drives applied on the circular conducting boundary. In the latter case the radio-frequency fields are chosen in the frequency range of the low-order azimuthal (diocotron) modes of the plasma in order to investigate their effect on the insurgence of azimuthal instabilities and the formation and evolution of coherent structures, possibly preventing the relaxation to a fully-developed turbulent state. Different initial density distributions (rings and spirals) are considered, so that evolutions characterized by different levels of turbulence and intermittency are obtained. The time evolution of integral and spectral quantities of interest are computed using a multiresolution analysis based on a wavelet decomposition of density maps. Qualitative features of turbulent relaxation are found to be similar in conditions of both free and forced evolution, but the analysis allows one to highlight fine details of the flow beyond the self-similarity turbulence properties, so that the influence of the initial conditions and the effect of the external forcing can be distinguished. In particular, the presence of small inhomogeneities in the initial density configuration turns out to lead to quite different final states, especially in the presence of competing unstable diocotron modes characterized by similar growth rates.

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Section: Introductionsupporting

confidence: 69%

Section: Discussionmentioning

confidence: 99%

Section: Influence Of Initial Conditions and Drivesmentioning

confidence: 99%

Section: Influence Of Initial Conditions and Drivesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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Coherent structures and turbulence evolution in magnetized non-neutral plasmas

Romé

Chen²,

Maero

2018

AIP Conference Proceedings

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Spectral analysis of forced turbulence in a non-neutral plasma

2017

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The paper investigates the dynamics of magnetized non-neutral (electron) plasmas subjected to external electric field perturbations. A two-dimensional (2-D) particle-in-cell code is effectively exploited to model this system with a special attention to the role that non-axisymmetric, multipolar radio frequency (RF) drives applied to the cylindrical (circular) boundary play on the insurgence of azimuthal instabilities and the subsequent formation of coherent structures preventing the relaxation to a fully developed turbulent state, when the RF fields are chosen in the frequency range of the low-order fluid modes themselves. The isomorphism of such system with a 2-D inviscid incompressible fluid offers an insight into the details of forced 2-D fluid turbulence. The choice of different initial density (i.e. fluid vorticity) distributions allows for a selection of conditions where different levels of turbulence and intermittency are expected and a range of final states is achieved. Integral and spectral quantities of interest are computed along the flow using a multiresolution analysis based on a wavelet decomposition of both enstrophy and energy 2-D maps. The analysis of a variety of cases shows that the qualitative features of turbulent relaxation are similar in conditions of both free and forced evolution; at the same time, fine details of the flow beyond the self-similarity turbulence properties are highlighted in particular in the formation of structures and their timing, where the influence of the initial conditions and the effect of the external forcing can be distinguished.

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