Theory and Simulation of Electron and Ion Holes: Latest Trends and Perspectives

A special issue of Plasma (ISSN 2571-6182).

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 8779

Special Issue Information

Dear Colleagues,

The onset of localized structure formation cannot be effectively described by Landau theory in realistic e.g. noisy plasmas; this represents one of the main challenges contemporary collisionless plasma theory is faced with. Long-lived phase space vortices or "holes", triggered by tiny stimuli or seeds, are now part of every simulation of driven plasmas regardless of the strength of the drive.

On the other hand, recent advances in the theory of hole equilibria, achieved by Schamel's pseudo-potential method, show an unlimited variety of hole solutions with fine structures in the phase space that no longer can be resolved experimentally. These solutions of the current-driven Vlasov-Poisson system not only enable the investigation of particle trapping effects, but also testing of linear Vlasov equilibria (van Kampen, Landau) or completing and upgrading of nonlinear BGK solutions. The origin of this complex - and surprising, for many - departure from linearity lies in the self-consistent nature of these coherent structures and in the resonant wave-particle interaction, the chaotic nature of which is responsible for an unlimited variety of particle trapping scenarios of either perturbative or non-perturbative character.

Theoretical and computational advancements that may help further clarify this complex subject are welcome for this Special Issue. Examples may include the influence of pair correlations at resonance or asymmetric versions of holes including double layers, among other possibilities.

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Keywords

  • kinetic hole structures
  • phase space vortices
  • nonlinear trapping
  • separatrices
  • Vlasov
  • chaotic trajectories
  • intermittence

Published Papers (3 papers)

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Research

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15 pages, 11831 KiB  
Article
Structural Characteristics of Ion Holes in Plasma
by Harikrishnan Aravindakshan, Amar Kakad, Bharati Kakad and Peter H. Yoon
Plasma 2021, 4(3), 435-449; https://0-doi-org.brum.beds.ac.uk/10.3390/plasma4030032 - 02 Sep 2021
Cited by 4 | Viewed by 2438
Abstract
Ion holes refer to the phase-space structures where the trapped ion density is lower at the center than at the rim. These structures are commonly observed in collisionless plasmas, such as the Earth’s magnetosphere. This paper investigates the role of multiple parameters in [...] Read more.
Ion holes refer to the phase-space structures where the trapped ion density is lower at the center than at the rim. These structures are commonly observed in collisionless plasmas, such as the Earth’s magnetosphere. This paper investigates the role of multiple parameters in the generation and structure of ion holes. We find that the ion-to-electron temperature ratio and the background plasma distribution function of the species play a pivotal role in determining the physical plausibility of ion holes. It is found that the range of width and amplitude that defines the existence of ion holes splits into two separate domains as the ion temperature exceeds that of the electrons. Additionally, the present study reveals that the ion holes formed in a plasma with ion temperature higher than that of the electrons have a hump at its center. Full article
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7 pages, 260 KiB  
Article
Formation of Kinetics Coherent Structures in Weakly Collisional Media
by Alexander Karimov and Vladislav Bogdanov
Plasma 2021, 4(2), 359-365; https://0-doi-org.brum.beds.ac.uk/10.3390/plasma4020024 - 18 Jun 2021
Cited by 1 | Viewed by 2043
Abstract
The formation of nonlinear, nonstationary structures in weakly collisional media with collective interactions are investigated analytically within the framework of the kinetic description. This issue is considered in one-dimensional geometry using collision integral in the Bhatnagar-Gross-Krook form and some model forms of the [...] Read more.
The formation of nonlinear, nonstationary structures in weakly collisional media with collective interactions are investigated analytically within the framework of the kinetic description. This issue is considered in one-dimensional geometry using collision integral in the Bhatnagar-Gross-Krook form and some model forms of the interparticle interaction potentials that ensure the finiteness of the energy and momentum of the systems under consideration. As such potentials, we select the Yukawa potential, the δ-potential, which describes coherent structures in a plasma. For such potentials we obtained a dispersion relation which makes it possible to estimate the size and type of the forming structures. Full article

Review

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51 pages, 3297 KiB  
Review
Electrostatic Solitary Structures in Space Plasmas: Soliton Perspective
by Gurbax Singh Lakhina, Satyavir Singh, Rajith Rubia and Selvaraj Devanandhan
Plasma 2021, 4(4), 681-731; https://0-doi-org.brum.beds.ac.uk/10.3390/plasma4040035 - 21 Oct 2021
Cited by 20 | Viewed by 3400
Abstract
Occurrence of electrostatic solitary waves (ESWs) is ubiquitous in space plasmas, e.g., solar wind, Lunar wake and the planetary magnetospheres. Several theoretical models have been proposed to interpret the observed characteristics of the ESWs. These models can broadly be put into two main [...] Read more.
Occurrence of electrostatic solitary waves (ESWs) is ubiquitous in space plasmas, e.g., solar wind, Lunar wake and the planetary magnetospheres. Several theoretical models have been proposed to interpret the observed characteristics of the ESWs. These models can broadly be put into two main categories, namely, Bernstein–Green–Kruskal (BGK) modes/phase space holes models, and ion- and electron- acoustic solitons models. There has been a tendency in the space community to favor the models based on BGK modes/phase space holes. Only recently, the potential of soliton models to explain the characteristics of ESWs is being realized. The idea of this review is to present current understanding of the ion- and electron-acoustic solitons and double layers models in multi-component space plasmas. In these models, all the plasma species are considered fluids except the energetic electron component, which is governed by either a kappa distribution or a Maxwellian distribution. Further, these models consider the nonlinear electrostatic waves propagating parallel to the ambient magnetic field. The relationship between the space observations of ESWs and theoretical models is highlighted. Some specific applications of ion- and electron-acoustic solitons/double layers will be discussed by comparing the theoretical predictions with the observations of ESWs in space plasmas. It is shown that the ion- and electron-acoustic solitons/double layers models provide a plausible interpretation for the ESWs observed in space plasmas. Full article
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