Adiabatic behavior of an elliptical vortex in a time-dependent external strain flow

Hurst, N. C.; Danielson, J. R.; Dubin, D. H. E.; Surko, C. M.

doi:10.1103/physrevfluids.6.054703

Cited by 8 publications

(3 citation statements)

References 69 publications

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“…Once the mode reaches saturation, damping through filamentation progresses and the excited mode will eventually collapse catastrophically, initiating a cascade to lower modes towards the final axisymmetric state. As stated in the introduction, the analysis of the decay stage is among our future goals and will not be discussed here; for the reader's convenience, we just mention that a variety of diocotron mode decay mechanisms has already been observed in the past (Driscoll & Fine 1990;Mitchell & Driscoll 1994;Kabantsev et al 2014). Notice also that mode saturation is reached already within a small-perturbation regime, as the plasma electrostatic potential at the edge of the core (r R w /2) is around 20 V, where a 1.5 V dipole drive at the trap wall drops to half its value, so that the perturbation-to-plasma potential ratio is less than 5 × 10 −2 .…”

Section: Selective Mode Excitationmentioning

confidence: 99%

“…We direct our attention in particular to the instance of non-axisymmetric isolated vortices. Recently, Hurst and coauthors have extensively studied the evolution of a deformed vortex embedded in a static or slowly evolving strain field, which in the plasma analogy is the electric field obtained by imposing suitable potentials on the azimuthally sectored cylindrical wall of the trapping volume (Hurst et al 2016(Hurst et al , 2020(Hurst et al , 2021. Rotating deformed vortices, on the contrary, can arise as a consequence of Kelvin-Helmholtz (KH) perturbations, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Resonant excitation of single Kelvin–Helmholtz high-order waves in a magnetized electron fluid vortex

Maero,

Panzeri,

Patricelli

et al. 2023

J. Plasma Phys.

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Thanks to the isomorphism between the drift-Poisson and Euler equations, inviscid two-dimensional fluid experiments can be performed in magnetized, single-component plasmas in Penning–Malmberg traps. Within this analogy, a trapped electron plasma column is equivalent to a two-dimensional vortex. Here, we focus our attention on the generation of V-states, i.e. $l$ -fold symmetric rotating vorticity patches where the deformation with respect to the circular cross-section has reached the nonlinear regime. We detail a linear theoretical analysis and devise an experimental routine to generate V-states through the precise excitation of single Kelvin–Helmholtz perturbations in a magnetized electron plasma. This technique makes use of suitable multipolar rotating electric fields, which are shown to be able to select the desired wavemode. In particular, with rotating fields, a hardware limitation in the highest accessible mode is removed and nonlinear Kelvin–Helmholtz waves of generic order $l$ can be attained, which pave the way for further investigations on the evolution and stability properties of V-states. Systematic experimental results for the selective mode growth in the linear and nonlinear regimes up to saturation and collapse are discussed.

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Section: Selective Mode Excitationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Resonant excitation of single Kelvin–Helmholtz high-order waves in a magnetized electron fluid vortex

Maero,

Panzeri,

Patricelli

et al. 2023

J. Plasma Phys.

View full text Add to dashboard Cite

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“…Trivelpiece-Gould waves (TGWs) 15 -the counterpart of Langmuir waves in nonneutral plasmas, Electron Acoustic waves (EAWs) [16][17][18] are typical longitudinal fluctuations occurring in Penning-Malmberg devices, while diocotron [19][20][21] , cyclotron 22,23 and Bernstein 24 waves oscillate in the transverse directions. The perpendicular dynamics shows also significant analogies with a two-dimensional inviscid fluid 25 , thus motivating several experimental and numerical efforts to study, for example, the vortex dynamics subject to an external strain 26,27 . More recently Penning-Malmberg devices have been exploited in experiments aimed at determining the gravitational properties of antimatter 28 .…”

Section: Introductionmentioning

confidence: 99%

Eulerian simulations of electrostatic waves in plasmas with a single sign of charge

et al. 2022

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An Eulerian, numerical simulation is used to model the launching of plasma waves in a non-neutral plasma that is confined in a Penning–Malmberg trap. The waves are launched by applying an oscillating potential to an electrically isolated sector at one end of the conducting cylinder that bounds the confinement region and are received by another electrically isolated sector at the other end of the cylinder. The launching of both Trivelpiece–Gould waves and electron acoustic waves is investigated. Adopting a stratagem, the simulation captures essential features of the finite length plasma, while retaining the numerical advantages of a simulation employing periodic spatial boundary conditions. As a benchmark test of the simulation, the results for launched Trivelpiece–Gould waves of small amplitude are successfully compared to a linearized analytic solution for these fluctuations.

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Inviscid damping of an elliptical vortex subject to an external strain flow

et al. 2022

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Inviscid spatial Landau damping is studied experimentally for the case of oscillatory motion of a two-dimensional vortex about its elliptical equilibrium in the presence of an applied strain flow. The experiments are performed using electron plasmas in a Penning–Malmberg trap. They exploit the isomorphism between the two-dimensional Euler equations for an ideal fluid and the drift-Poisson equations for the plasma, where plasma density is the analog of vorticity. Perturbed elliptical vortex states are created using [Formula: see text] strain flows, which are generated by applying voltages to electrodes surrounding the plasma. Measurements of spatial Landau damping (also called critical-layer damping) are in agreement with previous studies in the absence of an applied strain, where the damping is due to a resonance between the local fluid motion and the vortex oscillations. Interestingly, the damping rate does not change significantly over a wide range of applied strain rates. This can be accurately predicted from the initial vorticity profile, even though the resonant frequency is reduced substantially due to the applied strain. For higher amplitude perturbations, nonlinear trapping oscillations also exhibit behavior similar to the strain-free case. In principle, higher-order effects of the applied strain, such as separatrix crossing of peripheral vorticity and interactions with harmonics of the fundamental resonance, are expected to change the damping rate. However, this occurs only for conditions that are not realized in the experiments described here. Vortex-in-cell simulations are used to investigate the possible roles of these effects.

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Adiabatic behavior of an elliptical vortex in a time-dependent external strain flow

Cited by 8 publications

References 69 publications

Resonant excitation of single Kelvin–Helmholtz high-order waves in a magnetized electron fluid vortex

Resonant excitation of single Kelvin–Helmholtz high-order waves in a magnetized electron fluid vortex

Eulerian simulations of electrostatic waves in plasmas with a single sign of charge

Inviscid damping of an elliptical vortex subject to an external strain flow

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