Rotating Spokes, Ionization Instability, and Electron Vortices in Partially Magnetized 
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 Plasmas

Boeuf, Jean-Pierre; Takahashi, M.

doi:10.1103/physrevlett.124.185005

Cited by 38 publications

(31 citation statements)

References 26 publications

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“…The spoke velocity that can be deduced from this figure is around 10 km/s (in agreement with the experimental result of Ito et al 10 , as discussed in Ref. 39 ). We note that a large part of the ionization (black contours in Figure 5a) takes place on the upper side of the region of maximum plasma density, i.e.…”

Section: A General Properties Of the Retrograde Rotating Spokesupporting

confidence: 92%

“…Note also that the 0.4x10 16 m -3 plasma density of Figure 4 corresponds to a plasma density of 0.4x10 18 m -3 in the experiments of Ito et al (See Ref. 39 ). There is clearly a dominant frequency of the current oscillations corresponding to a period around 4 s.…”

Section: A General Properties Of the Retrograde Rotating Spokementioning

confidence: 63%

“…In this paper we consider conditions that are similar (in the sense of discharge similarity laws) to those of the magnetron discharge experiment of Ito et al 10 at Stanford University. The conditions of the experiments of Ito et al were simulated in a recent letter 39 . In this relatively simple experiment, Ito et al observed, with the help of a fast CCD camera, very nice and well-defined, self-organized structures rotating in the azimuthal direction of a miniature magnetron.…”

Section: A Simulation Conditionsmentioning

confidence: 99%

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New insights into the physics of rotating spokes in partially magnetized E×B plasmas

Boeuf

Takahashi

2020

Physics of Plasmas

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Regions of enhanced light emission rotating in the azimuthal direction ("rotating spokes") have been observed in different types of partially magnetized × plasma devices such as magnetron discharges and Hall thrusters. A two-dimensional Particle-In-Cell Monte Carlo Collisions (PIC MCC) model is used to study the formation of these rotating structures. The model shows that these current driven rotating structures are the results of a Simon-Hoh instability evolving into an ionization instability. The spoke is sustained by local electron heating induced by drift along a double layer separating the cathodic presheath from the plasma at a potential close to the anode potential. The PIC MCC simulations predict that spoke rotation can take place in the + × direction as well as in the − × direction depending on the magnetic field intensity.

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Section: A General Properties Of the Retrograde Rotating Spokesupporting

confidence: 92%

Section: A General Properties Of the Retrograde Rotating Spokementioning

confidence: 63%

Section: A Simulation Conditionsmentioning

confidence: 99%

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New insights into the physics of rotating spokes in partially magnetized E×B plasmas

Boeuf

Takahashi

2020

Physics of Plasmas

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“…The 2D version J-PIC has been used in several recent papers on the simulation of magnetized plasmas (see, e.g., Refs. [26][27][28][29][30][31][32] ). J-PIC is based on standard features of the electrostatic PIC-MCC method as described by Birdsall 25 .…”

Section: Pic-mcc Modelmentioning

confidence: 99%

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

Boeuf

2022

Physics of Plasmas

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A one-dimensional Particle-In-Cell Monte Carlo Collisions (PIC-MCC) method has been used to model the development and propagation of ionization waves in neon and argon positive columns. Low current conditions are considered, i.e. conditions where stepwise ionization or Coulomb collisions are negligible (linear ionization rate). This self-consistent model describes the development of self-excited moving striations, reproduces many of the well-known experimental characteristics (wavelength, spatial resonances, potential drop over one striation, electron "bunching" effect) of the ionization waves called p, r and s waves in the literature and sheds light on their physical properties and on the mechanisms responsible for their existence. These are the first fully kinetic self-consistent simulations over a large range of conditions reproducing the development of p, r and s ionization waves. Although the spatial resonances and the detailed properties of the striations in the non-linear regime are of kinetic nature, the conditions of existence of the instability can be obtained and understood from a linear stability analysis of a three-moment set of quasi-neutral fluid equations where the electron transport coefficients are expressed as a function of electron temperature and are obtained from solutions of a 0D Boltzman equation. An essential aspect of the instability leading to the development of these striations is the non-Mawellian nature of the electron energy distribution function in the uniform electric field prior to the instability onset, resulting in an electron diffusion coefficient in space much larger than the energy diffusion coefficient.

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“…The geometry size has most impact on the density gradient length, which is expected to further modify the dispersion relation. The magnetic field gradient renders new free energy to destabilize the gradient drift wave [52] and enhances the electron heating due to B drift [53].…”

Section: Discussionmentioning

confidence: 99%

Direct evidence of the gradient drift instability being the origin of a rotating spoke in a crossed field plasma

Xu,

Eremin,

Brinkmann

2021

Preprint

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A plasma rotating spoke in a crossed field discharge is studied using 2D radial-azimuthal fully kinetic Particle-In-Cell Monte Carlo Collision (PIC/MCC) simulations. The kinetic model reveals the whole perturbation spectrum of the gradient drift instability in the linear stage: Simon-Hoh, lower-hybrid and ion sound modes, providing direct evidence of the spoke of the gradient drift instability nature. The two-fluid dispersion relation of the gradient drift instability was utilized to analyze the linear development of instabilities in the simulations. The charge separation effect was incorporated in the fluid linear theory and a super-resolution signal processing method (multiple signal classification) was applied to obtain the numerical frequency spectrum. The simulated spectrum and growth rate show excellent agreement with the theoretical dispersion relation (real frequency and imaginary frequency) over investigated cases. The most linearly unstable mode was found to be the lower hybrid instability and the mode transition into the m=1 macroscopic rotating structure after saturation of the linear phase is accompanied by an inverse energy cascade. In the nonlinear stage, the pronounced spoke phenomena can occur when the heating of E θ × B electron flow channeled in the spoke front passage suffices to provide the enhanced ionization.

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Rotating Spokes, Ionization Instability, and Electron Vortices in Partially Magnetized E×B Plasmas

Cited by 38 publications

References 26 publications

New insights into the physics of rotating spokes in partially magnetized E×B plasmas

New insights into the physics of rotating spokes in partially magnetized E×B plasmas

Ionization waves (striations) in a low-current plasma column revisited with kinetic and fluid models

Direct evidence of the gradient drift instability being the origin of a rotating spoke in a crossed field plasma

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