Plasma Physics Highlights: Non-equilibrium Dynamics, Interfaces and Mixing

A special issue of Atoms (ISSN 2218-2004).

Deadline for manuscript submissions: closed (31 October 2024) | Viewed by 5322

Special Issue Editor


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Guest Editor
Faculty of Engineering and Mathematical Sciences, The University of Western Australia, Crawley, WA 6009, Australia
Interests: theoretical and applied physics – dynamics of plasmas, fluids, materials; applied mathematics – partial differential equations, analysis, dynamical systems, data analysis

Special Issue Information

Dear Colleagues,

We propose organizing a Special Issue: ‘Plasma Physics Highlights: Non-equilibrium Dynamics, Interfaces and Mixing’.

Non-equilibrium dynamics, interfaces and mixing play an important role in plasmas in high and low energy density regimes, at astrophysical and at atomic scales, in nature and technology. Examples include the instabilities and interfacial mixing in supernovae and in inertial confinement fusion, particle–field interactions in magnetic fusion and in imploding Z-pinches, downdrafts in stellar interior and in planetary magneto-convection, plasma thrusters, nanofabrication and magnetic flux ropes and structures in the Solar corona and plasma instabilities in the Earth ionosphere.

In some of these environments (such as stellar interiors and plasma thrusters), non-equilibrium dynamics and interfacial mixing should be enhanced; in others (for instance, in fusion and nanofabrication), they should be mitigated and tightly controlled. In all these circumstances, however, we need to achieve a better understanding of the fundamentals of non-equilibrium transport, interfaces and mixing in plasmas.

Non-equilibrium processes are exceedingly challenging to study. They usually involve sharp changes to the flow fields, high pressures and accelerations, strong magnetic fields and coupled particles and fields. They are inhomogeneous (i.e., the flow fields are essentially non-uniform, even in a statistical sense, and may involve fronts), anisotropic (i.e., their dynamics depend on the directions), non-local (i.e., plasma flows may include contributions from all the scales and sense initial and boundary conditions) and statistically unsteady (i.e., the mean values of the quantities vary with time, and there are also time-dependent fluctuations around these means). Their properties often strongly deviate from those prescribed by standard scenarios at macroscopic scales and at kinetic scales.

Despite these challenges, significant success has recently been achieved in theoretical analysis (for instance, new approaches for handling multi-scale, non-local and statistically unsteady transport, new fluid instabilities and new mechanisms for energy transport in unstable plasma flows), in large-scale numerical simulations (including Lagrangian and Eulerian methods), in experiments (for instance, in fusion facilities and in laboratory plasma devices, including possibilities for large dynamic range, high precision, high accuracy and high data acquisition rate). This opens new opportunities for the study of fundamental properties of non-equilibrium dynamics and mixing at astrophysical and at kinetic scales.

This Special Issue would provide the opportunity to bring together scientists from different areas of plasma physics, including astrophysical, laboratory and fusion plasmas. It would serve to promote the exchange of ideas, and to motivate the discussions of rigorous theoretical approaches and state-of-the-art numerical simulations along with advanced experimental techniques and technological applications. This Special Issue would be of potential interest to the general and highly professional readership of Atoms. It would also attract the attention of the interdisciplinary and international physics communities regarding the fundamentals of plasma physics.

Prof. Dr. Snezhana Abarzhi
Guest Editor

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Keywords

  • plasma physics
  • non-equilibrium dynamics
  • plasma instabilities
  • interfacial mixing
  • high energy density
  • low energy density
  • astrophysical plasmas
  • nanofabrication
  • plasma discharge

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Published Papers (4 papers)

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Research

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14 pages, 7071 KiB  
Article
Applicability of Bispectral Analysis to Causality Determination within and between Ensembles of Unstable Plasma Waves
by Renaud Stauber and Mark Koepke
Atoms 2024, 12(9), 44; https://doi.org/10.3390/atoms12090044 - 5 Sep 2024
Viewed by 598
Abstract
Turbulence implies nonlinear wave–wave coupling, and determining cause and effect of either is important to understand mixing responsible for enhanced number, momentum, or energy (NME) transport. To explain the identification of parent and daughter modes via a look-up table, we sketch the framework [...] Read more.
Turbulence implies nonlinear wave–wave coupling, and determining cause and effect of either is important to understand mixing responsible for enhanced number, momentum, or energy (NME) transport. To explain the identification of parent and daughter modes via a look-up table, we sketch the framework of bispectral analysis without repeating the mathematical formalism of earlier bispectrum researchers. We then apply this technique to a test signal and plasma fluctuation data from the WVU-Q machine, where the inhomogeneous energy density-driven spectrum exhibited a degree of coupling to lower frequencies that was absent in the case of the related, single-eigenmode, current-driven spectrum. Full article
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9 pages, 2276 KiB  
Article
Detection of Optogalvanic Spectra Using Driven Quasi-Periodic Oscillator Dynamics
by Mark Koepke
Atoms 2024, 12(8), 42; https://doi.org/10.3390/atoms12080042 - 19 Aug 2024
Viewed by 813
Abstract
The narrowband light from a scannable, single-mode dye laser influences the electrical properties of gas discharges. The variation in these properties as the laser wavelength λ is scanned yields the optogalvanic spectrum of the discharge (i.e., electrical conductivity vs. frequency). By connecting a [...] Read more.
The narrowband light from a scannable, single-mode dye laser influences the electrical properties of gas discharges. The variation in these properties as the laser wavelength λ is scanned yields the optogalvanic spectrum of the discharge (i.e., electrical conductivity vs. frequency). By connecting a neon lamp, capacitor, and power supply in parallel, an undriven relaxation oscillator is formed whose natural frequency f0 is affected by neon-resonant laser light and this λ-dependence of the relaxation oscillator frequency f0 yields a variant optogalvanic spectrum (i.e., f0 vs. frequency). In this paper, a driving force is effectively applied to an otherwise undriven oscillator when the incident light is chopped periodically at fd. For fdf0 and a sufficiently large driving force amplitude (laser intensity and the degree of neon resonance), the relaxation oscillator can be entrained so that f0 is locked on fd and is independent of λ. For the new chopped-light technique described here, fd is adjusted to be the subthreshold of the entrainment range, where the λ-dependence of f0 is advantageously exaggerated by periodic pulling, and the beat frequency |fdf0| vs. λ provides an optogalvanic spectrum with appealingly amplified signal-to-noise qualities. Beat frequency neon spectra are reported for the cases fd < f0 and fd > f0 and are compared with spectra obtained using the unchopped-light (i.e., undriven) method. Full article
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40 pages, 3865 KiB  
Article
On Rayleigh–Taylor Dynamics
by Abdul Hasib Rahimyar, Des Hill, James Glimm and Snezhana Abarzhi
Atoms 2023, 11(12), 155; https://doi.org/10.3390/atoms11120155 - 8 Dec 2023
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Abstract
In this work, we theoretically and numerically investigate Rayleigh–Taylor dynamics with constant acceleration. On the side of theory, we employ the group theory approach to directly link the governing equations to the momentum model, and to precisely derive the buoyancy and drag parameters [...] Read more.
In this work, we theoretically and numerically investigate Rayleigh–Taylor dynamics with constant acceleration. On the side of theory, we employ the group theory approach to directly link the governing equations to the momentum model, and to precisely derive the buoyancy and drag parameters for the bubble and spike in the linear, nonlinear, and mixing regimes. On the side of simulations, we analyze numerical data on Rayleigh–Taylor mixing by applying independent self-similar processes associated with the growth of the bubble amplitude and with the bubble merger. Based on the obtained results, we reveal the constituents governing Rayleigh–Taylor dynamics in the linear, nonlinear, and mixing regimes. We outline the implications of our considerations for experiments in plasmas, including inertial confinement fusion. Full article
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44 pages, 12238 KiB  
Perspective
Laser and Astrophysical Plasmas and Analogy between Similar Instabilities
by Stjepan Lugomer
Atoms 2024, 12(4), 23; https://doi.org/10.3390/atoms12040023 - 16 Apr 2024
Cited by 1 | Viewed by 1414
Abstract
Multipulse laser–matter interactions initiate nonlinear and nonequilibrium plasma fluid flow dynamics and their instability creating microscale vortex filaments, loop-soliton chains, and helically paired structures, similar to those at the astrophysical mega scale. We show that the equation with the Hasimoto structure describes both, [...] Read more.
Multipulse laser–matter interactions initiate nonlinear and nonequilibrium plasma fluid flow dynamics and their instability creating microscale vortex filaments, loop-soliton chains, and helically paired structures, similar to those at the astrophysical mega scale. We show that the equation with the Hasimoto structure describes both, the creation of loop solitons by torsion of vortex filaments and the creation of solitons by helical winding of magnetic field lines in the Crab Nebula. Our experiments demonstrate that the breakup of the loop solitons creates vortex rings with (i) quasistatic toroidal Kelvin waves and (ii) parametric oscillatory modes—i.e., with the hierarchical instability order. For the first time, we show that the same hierarchical instability at the micro- and the megascale establishes the conceptual frame for their unique classification based on the hierarchical order of Bessel functions. Present findings reveal that conditions created in the laser-target regions of a high filament density lead to their collective behavior and formation of helically paired and filament-braided “complexes”. We also show, for the first time, that morphological and topological characteristics of the filament-bundle “complexes” with the loop solitons indicate the analogy between similar laser-induced plasma instabilities and those of the Crab and Double-Helix Nebulas—thus enabling conceptualization of fundamental characteristics. These results reveal that the same rotating metric accommodates the complexity of the instabilities of helical filaments, vortex rings, and filament jets in the plasmatic micro- and megascale astrophysical objects. Full article
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