Study of trapping effect on ion-acoustic solitary waves based on a fully kinetic simulation approach

Jenab, S. M. Hosseini; Spanier, F.

doi:10.1063/1.4964909

Cited by 11 publications

(5 citation statements)

References 45 publications

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“…This process and the dependency of IA solitons on the initial conditions is discussed in Ref. [43] extensively. The stability of the IA solitons against successive mutual collisions is presented in Fig.3.…”

Section: B Benchmarking Of the Simulation Codementioning

confidence: 98%

“…PIC [13] and hybrid-PIC [14] simulations have ignored the details of trapped electrons distribution function in their reports mostly due to the inherent noise of PIC which smooths out holes in the phase space. Vlasov simulation studies of the chain formation have proved the stability of self-consistent IA solitons, produced by this method, against successive mutual collisions [15], [16] and compared them to the Schamel theory [43] .…”

Section: Introductionmentioning

confidence: 99%

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Kinetic Simulation Study of Electron Holes Dynamics During Collisions of Ion-Acoustic Solitons

Hosseini-Jenab

Spanier

2017

IEEE Trans. Plasma Sci.

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Abstract-Ion acoustic (IA) solitons are accompanied by vortex-shaped nonlinear structures (e.g. hollows, plateaus or humps) in the electron distribution function, called electron holes, portraying trapped electrons. These structures appear as charged flexible clouds (shielded by the background plasma) in the phase space with their own inertia, depending on the number of trapped electrons. According to simulation studies, electron holes tend to merge in pairs until one accumulative hole remains in the simulation box. This tendency has been analytically and qualitatively explained in the frame of the energy conservation principle. However, electron holes accompanying IA solitons should not merge due to stability of IA solitons against mutual collisions. In this report based on a fully kinetic simulation approach, detailed study of the collisions of IA solitons reveals the behavior of electron holes under these two conflicting predictions, i.e. stability against mutual collisions and merging tendency. Four main results are reported here. Firstly, we find that among the three different types of collisions possible for electron holes, just two of them happen for electron holes accompanying IA solitons. We present different collisions, e.g. two large/small and large versus small holes, to cover all the these three different types of collisions. Secondly, we show that although electron holes merge during collisions of IA solitons, the stability of IA solitons forces the merged hole to split and form new electron holes. Thirdly, we reveal that holes share their trapped population during collisions. Post-collision holes incorporate some parts of the oppositely propagating before-collision holes. Finally, it is shown that the newly added population of trapped electrons goes through a spiral path inside the after-collision holes hole because of dissipative effects. This spiral is shown to exist in the early stage of the formation of the holes in the context of the IA soliton dynamics.

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Section: B Benchmarking Of the Simulation Codementioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Kinetic Simulation Study of Electron Holes Dynamics During Collisions of Ion-Acoustic Solitons

Hosseini-Jenab

Spanier

2017

IEEE Trans. Plasma Sci.

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“…the Fourier transform and by checking their respective dispersion relation. 15 . When high frequency noise are produced, with a wavelength smaller than the grid spacing in the spatial direction, the small scale structures can no longer be tracked in the simulation and this causes a small deviation in the energy conservation.…”

Section: Resultsmentioning

confidence: 99%

Head-on collision of nonlinear solitary solutions to Vlasov-Poisson equations

Jenab

Brodin

2019

Preprint

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Nonlinear solitary solutions to the Vlasov-Poisson set of equations are studied in order to investigate their stability by employing a fully-kinetic simulation approach. The study is carried out in the ion-acoustic regime for a collisionless, electrostatic and Maxwellian electron-ion plasma. The trapped population of electrons is modeled based on well-known Schamel distribution function. Head-on mutual collisions of nonlinear solutions are performed in order to examine their collisional stability. The findings include three major aspects: (I) These nonlinear solutions are found to be divided into three categories based on their Mach numbers, i.e. stable, semi-stable and unstable. Semi-stable solutions indicates a smooth transition from stable to unstable solutions for increasing Mach number. (II) The stability of solutions is traced back to a condition imposed on averaged velocities, i.e. net neutrality. It is shown that a bipolar structure is produced in the flux of electrons, early in the temporal evolution. This bipolar structure acts as the seed of the net-neutrality instability, which tips off the energy balance of nonlinear solution during collisions. As the Mach number increases, the amplitude of bipolar structure grows and results in a stronger instability. (III) It is established that during mutual collisions, a merging process of electron holes can happen to a variety of degrees, based on their velocity characteristics. Specifically, the number of rotations of electron holes around each other (in the merging phase) varies. Furthermore, it is observed that in case of a non-integer number of rotations, two electron holes exchange their phase space cores.

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“…It is also can be generally assumed that any large hole can break up into smaller holes in a process called "chain formation". It is shown that the pulses produced by this process are truly solitary waves via long-time simulation 18 and solitons by focusing on their mutual collisions [19][20][21] in the fully kinetic regime.…”

Section: B Simulation Study Of Electron Holesmentioning

confidence: 99%

A study of the stability properties of Sagdeev solutions in the ion-acoustic regime using kinetic simulations

2018

Self Cite

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The Sagdeev pseudo-potential approach has been employed extensively in theoretical studies to determine large-amplitude (fully) nonlinear solutions in a variety of multi-species plasmas. Although these solutions are repeatedly considered as solitary waves (and even solitons), their temporal stability has never been proven. In this paper, a numerical study of the Vlasov-Poisson system is made to follow their temporal evolution in the presence of numerical noise and thereby test their longtime propagation stability. Considering the ion-acoustic regime, both constituents of the plasma, i.e. electrons and ions are treated following their distribution functions in these set of fully-kinetic simulations. The findings reveal that the stability of Sagdeev solution depends on a combination of two parameters, i.e. velocity and trapping parameter. It is shown that there exists a critical value of trapping parameter for both fast and slow solutions which separates the stable from unstable solutions. In case of stable solutions, it is shown that these nonlinear structures can propagate for long periods, which confirms their status as solitary waves. Stable solutions are reported for both Maxwellian and Kappa distribution functions. For unstable solutions, it is demonstrated that the instability causes the Sagdeev solution to decay by emitting ion-acoustic wave-packets on its propagation trail. The instability is shown to take place in a large range of velocity and even for Sagdeev solutions with velocity much higher than ion-sound speed. Besides, in order to validate our simulation code two precautionary measures are taken. Firstly, the well-known effect of the ion dynamics on a stationary electron hole solution is presented as a benchmarking test of the approach. Secondly, In order to verify the numerical accuracy of the simulations, the conservation of energy and entropy are presented. *

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Study of trapping effect on ion-acoustic solitary waves based on a fully kinetic simulation approach

Cited by 11 publications

References 45 publications

Kinetic Simulation Study of Electron Holes Dynamics During Collisions of Ion-Acoustic Solitons

Kinetic Simulation Study of Electron Holes Dynamics During Collisions of Ion-Acoustic Solitons

Head-on collision of nonlinear solitary solutions to Vlasov-Poisson equations

A study of the stability properties of Sagdeev solutions in the ion-acoustic regime using kinetic simulations

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