Nonlinear structures and anomalous transport in partially magnetized E×B plasmas

Janhunen, Salomon; Smolyakov, Andrei; Chapurin, Oleksandr; Sydorenko, Dmytro; Kaganovich, Igor; Raitses, Y.

doi:10.1063/1.5001206

Cited by 68 publications

(64 citation statements)

References 50 publications

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“…They too observe modulations in the sheath, however. In our simulations, the anomalous electron transport sets at the level similar to that in our 1D simulations 21 , perhaps due to the absence of secondary emission.…”

Section: Discussionsupporting

confidence: 77%

“…Our simulations demonstrate that like in the 1D case, the instability is driven by nonlinear cy-clotron resonance modes that dominate the anomalous transport, and that the cascade to long wavelengths observed in 1D simulations is further enhanced by the linear long wavelength instabilities that occur when finite k z is allowed. Moderate values of the anomalous electron current (of the order of Ω = Ω ce /ν ef f 200 are obtained in nonlinear stage similar to the 1D case 21 . An important new result is strong parallel electron heating due to the modes with a finite k z .…”

Section: Introductionsupporting

confidence: 55%

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Evolution of the electron cyclotron drift instability in two-dimensions

et al. 2018

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The Electron Cyclotron Drift Instability (ECDI) driven by the electron E × B drift in partially magnetized plasmas is investigated with highly resolved particle-in-cell simulations. The emphasis is on two-dimensional effects involving the parallel dynamics along the magnetic field in a finite length plasma with dielectric walls. It is found that the instability develops as a sequence of growing cyclotron harmonics demonstrating wave breaking and complex nonlinear interactions, being particularly pronounced in ion density fluctuations at short wavelengths. At the same time, nonlinear evolution of fluctuations of the ion and electron density, as well as the anomalous electron current, shows cascade toward long wavelengths. Tendency to generate long wavelength components is most clearly observed in the spectra of the electron density and the anomalous current fluctuations. An intense but slowly growing mode with a distinct eigen-mode structure along the magnetic field develops at a later nonlinear stage enhancing the tendency toward long wavelength condensation. The latter mode having a finite wavelength along the magnetic field is identified as the Modified Two-Stream Instability (MTSI). It is shown that the MTSI mode results in strong parallel heating of electrons.

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Section: Discussionsupporting

confidence: 77%

Section: Introductionsupporting

confidence: 55%

Evolution of the electron cyclotron drift instability in two-dimensions

et al. 2018

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“…Although the presence of the E Â B EDI is ubiquitous in PIC simulations including the azimuthal direction under the conditions of Hall thrusters, there is no consensus on its evolution toward a modified ion acoustic instability. Using a highly resolved 1D azimuthal PIC simulation under conditions of Hall thrusters, Janhunen 21 et al showed that the level of turbulence required for the transition to the ion acoustic instability is not reached. They observe a large coherent mode driven mainly at the electron cyclotron drift resonance, and energy flow to long wavelength and low frequency modes.…”

Section: Discussionmentioning

confidence: 99%

“…7,16,18, and 19 seem to be consistent with the scaling of the ion acoustic instability and saturation by ion wave trapping. However, in the recent 1D PC simulations of Janhunen et al, 21 the authors claim that transition to the ion acoustic instability does not occur because the demagnetization condition due to nonlinear resonance broadening is not fulfilled for the electrons.…”

Section: Two-dimensionalmentioning

confidence: 99%

E × B electron drift instability in Hall thrusters: Particle-in-cell simulations vs. theory

2018

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The E Â B Electron Drift Instability (E Â B EDI), also called Electron Cyclotron Drift Instability, has been observed in recent particle simulations of Hall thrusters and is a possible candidate to explain anomalous electron transport across the magnetic field in these devices. This instability is characterized by the development of an azimuthal wave with wavelength in the mm range and velocity on the order of the ion acoustic velocity, which enhances electron transport across the magnetic field. In this paper, we study the development and convection of the E Â B EDI in the acceleration and near plume regions of a Hall thruster using a simplified 2D axial-azimuthal Particle-In-Cell simulation. The simulation is collisionless and the ionization profile is not-self-consistent but rather is given as an input parameter of the model. The aim is to study the development and properties of the instability for different values of the ionization rate (i.e., of the total ion production rate or current) and to compare the results with the theory. An important result is that the wavelength of the simulated azimuthal wave scales as the electron Debye length and that its frequency is on the order of the ion plasma frequency. This is consistent with the theory predicting destruction of electron cyclotron resonance of the E Â B EDI in the non-linear regime resulting in the transition to an ion acoustic instability. The simulations also show that for plasma densities smaller than under nominal conditions of Hall thrusters the field fluctuations induced by the E Â B EDI are no longer sufficient to significantly enhance electron transport across the magnetic field, and transit time instabilities develop in the axial direction. The conditions and results of the simulations are described in detail in this paper and they can serve as benchmarks for comparisons between different simulation codes. Such benchmarks would be very useful to study the role of numerical noise (numerical noise can also be responsible to the destruction of electron cyclotron resonance) or the influence of the period of the azimuthal domain, as well as to reach a better and consensual understanding of the physics.

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“…These instabilities are very dependent on the specific conditions or regions of a particular device. For example, in a Hall thruster, the large electric field that is present in the acceleration region (quasineutral, collisionless plasma) is responsible for the development of the Electron Cyclotron Drift Instability (ECDI) or E B Electron Drift Instability which has been the subject of many recent studies 7,8,18,19,[40][41][42][43] . This instability leads to anomalous transport but the effective Hall parameter associated with it is relatively large (larger than 100 according to the PIC-MCC simulations 43 ).…”

Section: Introductionmentioning

confidence: 99%

Micro instabilities and rotating spokes in the near-anode region of partially magnetized plasmas

Boeuf

2019

Physics of Plasmas

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Electron and ion transport in the near-anode region of a partially magnetized plasma under conditions typical of Hall thrusters or magnetron discharges is studied with fully kinetic, Particle-In-Cell Monte Carlo Collision (PIC-MCC) simulations assuming a uniform magnetic field and no ionization. We derive a simple relation that defines the magnetic field at the transition point between negative and positive sheath. For magnetic fields around or above this transition point, PIC-MCC simulations show the development of short wavelength azimuthal instabilities that cascade to longer wavelengths ("rotating spokes") as the magnetic field is increased. Both short-wavelength and large-wavelength fluctuations can coexist under some conditions. A detailed study of the fluid dispersion relation is used to analyze the PIC-MCC results. Small coherent structures can be associated with the destabilization of ion sound waves by density gradient and collisions. Longer wavelengths or rotating spokes are characteristic of the collisionless Simon-Hoh instability. The small structures are dominant for larger plasma density gradients while the larger structures correspond to smaller density gradients and larger magnetic fields. Anomalous transport associated with these instabilities can be significant, with effective collision frequencies larger than 2 × 10 7 s −1 in xenon for magnetic fields above the transition point.

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Nonlinear structures and anomalous transport in partially magnetized E×B plasmas

Cited by 68 publications

References 50 publications

Evolution of the electron cyclotron drift instability in two-dimensions

Evolution of the electron cyclotron drift instability in two-dimensions

E × B electron drift instability in Hall thrusters: Particle-in-cell simulations vs. theory

Micro instabilities and rotating spokes in the near-anode region of partially magnetized plasmas

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