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Electrochemical Reactions at the Boundary Areas Between Cold Atmospheric Pressure Plasma, Air, and Water
Effect of Cathode Cooling in Three-Dimensional Simulations of an Atmospheric Pressure Glow Discharge
Characterization of the Plasma Generated by a Compact Theta Pinch
Effects of Spiralling Trajectories on White Dwarf Spectra: Remarks on Different Calculations

Journal Description

Plasma

Plasma is an international, open access, peer-reviewed journal covering all aspects of plasma science, published quarterly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within ESCI (Web of Science), Scopus, Inspec, CAPlus / SciFinder, and other databases.
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 26.8 days after submission; acceptance to publication is undertaken in 3.8 days (median values for papers published in this journal in the second half of 2024).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 1.9 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2571-6182

Latest Articles

17 pages, 3091 KiB

Open AccessReview

A Tutorial on One-Dimensional Numerical Simulation of Virtual Cathode Oscillation

by Weihua Jiang

Plasma 2025, 8(2), 13; https://doi.org/10.3390/plasma8020013 (registering DOI) - 1 Apr 2025

This review article is the continuation of a previous publication, by the same author, on one dimensional theory of space charge effect and virtual cathode. The virtual cathode is known to be unstable. However, the process of virtual cathode oscillation is very complicated [...] Read more.

This review article is the continuation of a previous publication, by the same author, on one dimensional theory of space charge effect and virtual cathode. The virtual cathode is known to be unstable. However, the process of virtual cathode oscillation is very complicated both physically and mathematically. No satisfactory theoretical model exists that can fully describe the oscillatory behavior of the virtual cathode. On the other hand, computer simulations allow us to numerically observe this phenomenon and establish certain relations between the electron beam parameters and the virtual cathode characteristics. This article explains the detailed procedure of numerical modeling by dealing with the one-dimensional case as an example. A sample code written in the C language is attached at the end following the main text. This article is expected to serve as a reference for young researchers and students who are interested in computer simulations of intense particle beams and high-power microwave generation. Full article

(This article belongs to the Special Issue Latest Review Papers in Plasma Science 2025)

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20 pages, 5520 KiB

Open AccessReview

Runaway Electrons in Gas Discharges: Insights from the Numerical Modeling

by Dmitry Levko

Plasma 2025, 8(1), 12; https://doi.org/10.3390/plasma8010012 - 20 Mar 2025

This paper reviews the state of the art of our understanding of the mechanisms of runaway electron generation in pressurized gases from the numerical modeling perspective. Since the energy relaxation length of these electrons is comparable to the interelectrode spacing, these electrons can [...] Read more.

This paper reviews the state of the art of our understanding of the mechanisms of runaway electron generation in pressurized gases from the numerical modeling perspective. Since the energy relaxation length of these electrons is comparable to the interelectrode spacing, these electrons can be captured only using the kinetic approach. Therefore, only the results from kinetic models are discussed here. Special attention is given to pulsed discharges, which play an important role in modern industry. It is concluded that the mechanisms of runaway electron generation are defined by the gap overvoltage and the discharge gap geometry. For small and moderate overvoltages, runaway electrons are primarily generated at the heads of fast ionization waves or streamers. Due to their long energy relaxation length, these electrons can pre-ionize the discharge gap far from their origin, accelerating ionization and starting new avalanches. At high overvoltages, cathode surface irregularities enhance the local electric field, leading to electron emission into the interelectrode space. These electrons, injected into the strong electric field, gain high energy and reach discharge walls with extremely high energies measuring tens and hundreds of electron volts. These electrons not only pre-ionize the gas but also stimulate the emission of high-energy photons, which can further contribute to the pre-ionization of the discharge gap. Full article

(This article belongs to the Special Issue New Insights into Plasma Theory, Modeling and Predictive Simulations)

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19 pages, 6382 KiB

Open AccessArticle

Quantifying Plasma Dose for Barley Seed Treatment by Volume Dielectric Barrier Discharges in Atmospheric-Pressure Synthetic Air

by Jiří Fujera, Petr Hoffer, Václav Prukner and Milan Šimek

Plasma 2025, 8(1), 11; https://doi.org/10.3390/plasma8010011 - 17 Mar 2025

Plasma-assisted treatment is a potentially interesting technology for advanced seed processing. In this work, we address the issue of defining and quantifying the plasma dose during the exposure of seeds to microdischarges formed in a barrier discharge configuration fed with synthetic air at [...] Read more.

Plasma-assisted treatment is a potentially interesting technology for advanced seed processing. In this work, we address the issue of defining and quantifying the plasma dose during the exposure of seeds to microdischarges formed in a barrier discharge configuration fed with synthetic air at atmospheric pressure. Using advanced imaging and other optoelectrical diagnostics, we identify suitable conditions for the formation of microdischarges developing exclusively between the powered electrode and the seed coat, which allows for the relatively accurate quantification of the plasma dose for an individual barley seed. In addition to determining the microdischarge energy/power consumed to treat a single seed during controlled exposure, we also provide an estimate of the electric field and gas temperature, which are key parameters that can affect seed viability. In this way, each individually exposed seed can be linked to the exact exposure time, total number, energy, and temperature of the microdischarges that came into contact with it. This is fundamentally different from conventional “averaging” approaches based on the simultaneous exposure of many seeds, which makes it virtually impossible to correlate the responses of individual seeds with the corresponding individual plasma dose. Finally, we propose a minimal treatment protocol that could allow for the more direct interpretation of the results of subsequent biological tests to reveal seed responses to specific plasma–chemical stimuli during germination and seedling growth. Full article

(This article belongs to the Special Issue Processes in Atmospheric Pressure Plasmas)

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11 pages, 1336 KiB

Open AccessArticle

Network Analysis as a Method for Identifying Operational Modes of Cold Atmospheric Plasma Jets

by Blake Haist and Richard E. Wirz

Plasma 2025, 8(1), 10; https://doi.org/10.3390/plasma8010010 - 10 Mar 2025

Network analysis is a convenient method for analyzing cold atmospheric plasma (CAP) devices across a wide range of operating conditions. By using frequency and voltage as nodes in the network, edges are formed between nodes when the combination of voltage and frequency results [...] Read more.

Network analysis is a convenient method for analyzing cold atmospheric plasma (CAP) devices across a wide range of operating conditions. By using frequency and voltage as nodes in the network, edges are formed between nodes when the combination of voltage and frequency results in an ignited plasma jet. Singular value decomposition is used to identify modalities in the network that are representative of operational modes in the plasma jet. An analysis of the spectra produced by the jet provides validation of the operational modes and shows that voltage and frequency predominately affect the operation of the jet with remarkable independence. Full article

(This article belongs to the Special Issue Processes in Atmospheric Pressure Plasmas)

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17 pages, 13969 KiB

Open AccessArticle

Combined Plasma and Laser Heating of Graphite

by Aleksey Chaplygin, Mikhail Yakimov, Sergey Vasil’evskii, Mikhail Kotov, Ilya Lukomskii, Semen Galkin, Andrey Shemyakin, Nikolay Solovyov and Anatoly Kolesnikov

Plasma 2025, 8(1), 9; https://doi.org/10.3390/plasma8010009 - 4 Mar 2025

This paper investigates a novel combined laser and plasma heating test technique. Integrating the 1.5 kW Raycus RFL-C1500 laser source into the VGU-4 Inductively Coupled Plasma Facility (IPMech RAS) allowed the study of fine-grain MPG-7 graphite ablation in the high-temperature range from 2920 [...] Read more.

This paper investigates a novel combined laser and plasma heating test technique. Integrating the 1.5 kW Raycus RFL-C1500 laser source into the VGU-4 Inductively Coupled Plasma Facility (IPMech RAS) allowed the study of fine-grain MPG-7 graphite ablation in the high-temperature range from 2920 to 3865 K under exposure to subsonic nitrogen plasma flow and combined exposure to nitrogen plasma flow and laser irradiation. Graphite nitridation and sublimation were observed. The subsonic nitrogen plasma flow was characterized by numerical modeling, probes, and spectral measurements. The proposed experimental approach is promising for simulating the entry conditions of planetary mission vehicles into different atmospheres. Full article

(This article belongs to the Special Issue Feature Papers in Plasma Sciences 2025)

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14 pages, 4074 KiB

Open AccessArticle

Characterization of Tungsten Sputtering Processes in a Capacitively Coupled Argon Plasma

by Espedito Vassallo, Miriam Saleh, Matteo Pedroni, Anna Cremona and Dario Ripamonti

Plasma 2025, 8(1), 8; https://doi.org/10.3390/plasma8010008 - 28 Feb 2025

A capacitively coupled radio-frequency argon plasma, used for tungsten sputtering deposition, is characterized using Langmuir probe measurements. Druyvesteyn’s method is used to evaluate plasma parameters through the integral of the Electron Energy Distribution Function (EEDF). In the pressure range analyzed (0.6–10 Pa), the [...] Read more.

A capacitively coupled radio-frequency argon plasma, used for tungsten sputtering deposition, is characterized using Langmuir probe measurements. Druyvesteyn’s method is used to evaluate plasma parameters through the integral of the Electron Energy Distribution Function (EEDF). In the pressure range analyzed (0.6–10 Pa), the obtained distributions are not Maxwellian, which suggests some depletion of electrons with higher energies. The obtained plasma parameters are compared with those derived from the graphical method. The electron temperature obtained via the graphical method is always lower than the effective temperatures derived from EEDFs, and vice versa, the electron density is overestimated by the graphical method. Optical Emission Spectroscopy is used to monitor the atoms sputtered in the plasma process. The behavior of excited species correlates with the plasma parameters. Full article

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8 pages, 1370 KiB

Open AccessArticle

An Implicit Flux-Corrected Transport Algorithm Used for Gas Discharge Calculations

by Richard Morrow

Plasma 2025, 8(1), 7; https://doi.org/10.3390/plasma8010007 - 28 Feb 2025

An implicit flux-corrected transport (FCT) and diffusion algorithm was developed and used in many gas discharge calculations. Such calculations require the use of a fine mesh where the electric field changes rapidly; that is, near electrodes or in a streamer front. If diffusion [...] Read more.

An implicit flux-corrected transport (FCT) and diffusion algorithm was developed and used in many gas discharge calculations. Such calculations require the use of a fine mesh where the electric field changes rapidly; that is, near electrodes or in a streamer front. If diffusion is included using an explicit method, then the von Neumann stability condition severely limits the time-step that can be used; however, this limitation does not apply to implicit methods. Further, for gas discharge calculations including space-charge effects, it is necessary to solve the continuity equations with no negative number densities nor point-by-point oscillation in the number density. This is because the electron number densities are finely balanced with the ion number densities to determine the space-charge distribution and hence the electric field which drives the motion of the particles. An efficient way to solve the particle transport equation, with the required properties, is to use FCT. The most accurate form of FCT developed by the author is implicit fourth-order FCT; hence, the method presented incorporates implicit diffusion into the implicit fourth-order FCT scheme to produce a robust algorithm that has been successfully used in many calculations. Full article

(This article belongs to the Special Issue Recent Advances of Dielectric Barrier Discharges)

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18 pages, 1488 KiB

Open AccessArticle

Plasma-Induced Abatement of Tar from Syngas Produced in Municipal Waste Gasification: Thermodynamic Modeling with Experimental Validation

by Mobish A. Shaji, Francis Eboh, Alexander Rabinovich, Liran Dor and Alexander Fridman

Plasma 2025, 8(1), 6; https://doi.org/10.3390/plasma8010006 - 16 Feb 2025

Municipal waste gasification presents a promising avenue to extract useful energy from waste through syngas. This technology’s application is limited by tar formation (long-chain hydrocarbons), which can decrease energy conversion efficiency and applications of raw syngas. Non-thermal plasma-based tar degradation is a simple [...] Read more.

Municipal waste gasification presents a promising avenue to extract useful energy from waste through syngas. This technology’s application is limited by tar formation (long-chain hydrocarbons), which can decrease energy conversion efficiency and applications of raw syngas. Non-thermal plasma-based tar degradation is a simple and cost-effective alternative to existing thermal and catalytic tar mitigation methods. While plasma stimulates tar reformation reactions like steam reformation, there are thermodynamic energy requirements associated with these endothermic processes. Determining thermodynamic energy requirements and the equilibrium composition of products during tar reformation can aid with the proper optimization of the treatment process. In the present study, thermodynamic modeling and experimental validation are conducted to study energy requirements and product formation during the plasma-assisted steam reformation of tar present in raw syngas with an inlet temperature of 300 °C and 30% moisture content. The thermodynamic study evaluated the effect of adding air into the system (to increase the temperature by oxidizing a portion of raw syngas). Results show that up to 75% of energy requirement can be brought down by adding up to 30% air; experimental validation using gliding arc discharge with 30% air addition agrees with the thermodynamic model finding. The thermodynamic model predicted an increase in H₂ and CO concentration with the degradation of tar, but experimental validation reported a reduction in H₂ and CO concentration with the degradation of tar, as syngas was consumed to increase the temperature to support oxidation, owing to the low temperature (300 °C) and significant moisture presence (~30%) of raw syngas analyzed in this study. Full article

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25 pages, 7953 KiB

Open AccessArticle

A Study of Particle Heating and Oxidation Protection in a Modified Internally Injected Ar–H₂ Atmospheric Plasma Spraying Torch

by Mahrukh Mahrukh, Sen-Hui Liu, Li Zhang, Sohail Husnain, Cheng-Chung Yang, Xiao-Tao Luo and Chang-Jiu Li

Plasma 2025, 8(1), 5; https://doi.org/10.3390/plasma8010005 - 13 Feb 2025

This study employs computational fluid dynamics (CFD) to analyze the in-flight dynamics of particles in an Ar–H₂ atmospheric plasma spray (APS) torch with a modified diverging-type nozzle. The focus is on optimizing injection parameters—plasma gas flow rates, input power, and carrier gas [...] Read more.

This study employs computational fluid dynamics (CFD) to analyze the in-flight dynamics of particles in an Ar–H₂ atmospheric plasma spray (APS) torch with a modified diverging-type nozzle. The focus is on optimizing injection parameters—plasma gas flow rates, input power, and carrier gas flow rates—to enhance coating microstructure and deposition efficiency by achieving superheated molten metal droplets. Using a discrete phase model, the heat and momentum transfer of Ni/Al/C (2 wt.% diamond) composite powders (30–110 µm) within the plasma jet were simulated. Results show that particle characteristics, such as temperature and oxidation, can be controlled by adjusting plasma jet temperature (T∞) and velocity (U∞). Smaller particles heat faster, reaching higher temperatures with increased evaporation and oxidation rates. The modified nozzle enables Ni-based alloy particles to reach ~2500 °C, reducing oxygen inclusion in the plasma jet core. This setup allows for the control of the onset of carbon and oxygen reactions, wherein carbon serves as a sacrificial element, protecting the base alloy elements (such as aluminum) from excessive oxidation. Full article

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13 pages, 1929 KiB

Open AccessArticle

An Approach to Nuclear Fusion Utilizing the Dynamics of High-Density Electrons and Neutrals, Part I

by Alfred YiuFai Wong and Chun-Ching Shih

Plasma 2025, 8(1), 4; https://doi.org/10.3390/plasma8010004 - 31 Jan 2025

An approach to achieve nuclear fusion utilizing the formation of high densities of electrons and neutrals is described. The abundance of low energy free electrons produces intense electric fields that reduce the Coulomb barrier in nuclear fusion. Meanwhile, high-density rotating neutrals provide high [...] Read more.

An approach to achieve nuclear fusion utilizing the formation of high densities of electrons and neutrals is described. The abundance of low energy free electrons produces intense electric fields that reduce the Coulomb barrier in nuclear fusion. Meanwhile, high-density rotating neutrals provide high centrifugal forces to achieve the extreme pressure gradients of electrons and consequent negative electric fields to reduce the ion repulsive Coulombic fields. These high-density neutrals also provide better stability and higher reaction rates. Ion–neutral coupling is responsible for the control of neutral dynamics. Since high-frequency excitations favor the generation of free electrons, pulsed operations are recommended to achieve fusion with higher gains. Full article

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30 pages, 11200 KiB

Open AccessArticle

Shock Waves in Ion-Beam-Depleted Spin-Polarized Quantum Plasma with Ionic Pressure Anisotropy

by Manoj K. Deka, Balaram Pradhan, Apul N. Dev, Deepsikha Mahanta, Jalil Manafian and Khaled H. Mahmoud

Plasma 2025, 8(1), 3; https://doi.org/10.3390/plasma8010003 - 8 Jan 2025

In this study, the effects of pressure anisotropy and viscosity on the propagation of shock waves in spin-polarized degenerate quantum magnetoplasma are studied under the influence of the streaming energy of ion beams. The effects of different suitable plasma parameters on the shock [...] Read more.

In this study, the effects of pressure anisotropy and viscosity on the propagation of shock waves in spin-polarized degenerate quantum magnetoplasma are studied under the influence of the streaming energy of ion beams. The effects of different suitable plasma parameters on the shock wave’s potential profile are studied using the steady state solution of the Zakharov–Kuznetsov–Burgers (Z–K–B) equation, as well as the numerical simulation of the governing non-linear Z–K–B equation. First-order analysis of the non-linear wave propagation depicted a new beam-induced stable mode whose Mach number may be subsonic or supersonic depending on the anisotropic pressure combination in the presence of different spin density polarization ratios. This is the first observation of this new beam-induced stable mode in ion beam plasma, apart from the other existing modes of ion beam plasma systems, namely, the fast beam mode, the slow beam mode, the inherent ion acoustic mode, and the coupled mode, which also has unique propagation characteristics compared to the other modes. The spin density polarization ratio of spin-up and spin-down electrons have an unprecedented effect on the polarity and the direction of propagation of different shock wave modes in such plasma systems. Apart from the spin effect, anisotropic pressure combinations, as well as the viscosity of ions and ion beams, also play an outstanding role in controlling the nature of propagation of shock waves, especially in the newly detected beam-induced stable mode, and depending on the viscosity parameters of ions and ion beams, both oscillatory and monotonic shock waves can propagate in such plasma. Full article

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7 pages, 1387 KiB

Open AccessArticle

Effects of Spiralling Trajectories on White Dwarf Spectra: Remarks on Different Calculations

by Spiros Alexiou

Plasma 2025, 8(1), 2; https://doi.org/10.3390/plasma8010002 - 3 Jan 2025

The purpose of this paper is to address conflicting results regarding a simple criterion that has been proposed as decisive in determining whether accounting for spiralling electron trajectories increases or decreases the widths of hydrogen lines in a parameter range relevant to the [...] Read more.

The purpose of this paper is to address conflicting results regarding a simple criterion that has been proposed as decisive in determining whether accounting for spiralling electron trajectories increases or decreases the widths of hydrogen lines in a parameter range relevant to the spectral lines of white dwarfs. We analyse the claims in detail and also provide explicit calculations. It is shown that the recent attempts to justify a simple theory are erroneous and miss important physics. Full article

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8 pages, 1714 KiB

Open AccessArticle

Longitudinally Resolved Terahertz Radiation Characteristics Along Two-Color Filament in Air

by Juan Long, Tiejun Wang, Fukang Yin, Yaoxiang Liu, Yingxia Wei, Chengpu Liu and Yuxin Leng

Plasma 2025, 8(1), 1; https://doi.org/10.3390/plasma8010001 - 29 Dec 2024

The evolution of the THz waveform generated from the two-color air filament was experimentally investigated by moving an iris along the plasma channel. By taking the differentiation of the measured THz waveforms, the local longitudinally resolved THz waves along a 54 mm-long filament [...] Read more.

The evolution of the THz waveform generated from the two-color air filament was experimentally investigated by moving an iris along the plasma channel. By taking the differentiation of the measured THz waveforms, the local longitudinally resolved THz waves along a 54 mm-long filament were obtained. The local THz pulse underwent periodic phase shifts. A theoretical deduction indicates that the phase shifts are mainly caused by the dispersion in the plasma channel which plays a dominant role in the evolution of the local THz waveforms. Full article

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20 pages, 9396 KiB

Open AccessArticle

Characterization of the Plasma Generated by a Compact Theta Pinch

by Sagi Turiel, Alexander Gribov, Daniel Maler and Yakov E. Krasik

Plasma 2024, 7(4), 978-997; https://doi.org/10.3390/plasma7040053 - 20 Dec 2024

Theta Pinch is one of the promising methods for the generation of hot and dense plasma. In this paper, we describe the results of experimental research on a small-scale Theta Pinch created with Helium or Hydrogen plasmas. Different plasma diagnostics, namely, optical, microwave [...] Read more.

Theta Pinch is one of the promising methods for the generation of hot and dense plasma. In this paper, we describe the results of experimental research on a small-scale Theta Pinch created with Helium or Hydrogen plasmas. Different plasma diagnostics, namely, optical, microwave cut-off, laser interferometry, visible spectroscopy, Thomson scattering, and Laser-Induced Fluorescence were used to characterize the time- and space-resolved evolution of the plasma parameters, and the specific features of these diagnostic results obtained are discussed. The measured plasma density and the electron and ion temperature evolution, obtained by these various diagnostic tools, agree to a satisfactory level. These methods will be applied for studies of the parameters of the plasma in the device that is being developed by the nT-Tao company towards fusion energy. Full article

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39 pages, 4052 KiB

Open AccessArticle

Evaluation of a New Kind of Z-Pinch-Based Space Propulsion Engine: Theoretical Foundations and Design of a Proof-of-Concept Experiment

by S. K. H. Auluck, R. Verma and R. S. Rawat

Plasma 2024, 7(4), 939-977; https://doi.org/10.3390/plasma7040052 - 19 Dec 2024

This paper explores a recently proposed scalable z-pinch-based space propulsion engine in greater detail. This concept involves a “modified plasma focus with a tapered anode that transports current from a pulsed power source to a consumable portion of the anode in the form [...] Read more.

This paper explores a recently proposed scalable z-pinch-based space propulsion engine in greater detail. This concept involves a “modified plasma focus with a tapered anode that transports current from a pulsed power source to a consumable portion of the anode in the form of a hypodermic needle tube continuously extruded along the axis of the device”. This tube is filled with a gas at a high pressure and also optionally with an axial magnetic field. The current enters the metal tube through its contact with the anode and returns to the cathode via the plasma sliding over its outer wall. The resulting rapid electrical explosion of the metal tube partially transfers current to a snowplough shock in the fill gas. Both the metal plasma and the fill gas form axisymmetric converging shells. Their interaction forms a hot and dense plasma of the fill gas surrounded by the metal plasma. Its ejection along the axis provides the impulse needed for propulsion. In a nonnuclear version, the fill gas could be xenon or hydrogen. Its unique energy density scaling could potentially lead to a neutron-deficient nuclear fusion drive based on the proton-boron avalanche fusion reaction by lining the tube with solid decaborane. In order to explore the inherent potential of this idea as a scalable space propulsion engine, this paper discusses its theoretical foundations and outlines the first iteration of a conceptual engineering design study for a proof-of-concept experiment based on the UNU-ICTP Plasma Focus facility at the Nanyang Technological University, Singapore. Full article

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19 pages, 4353 KiB

Open AccessArticle

Effect of Cathode Cooling in Three-Dimensional Simulations of an Atmospheric Pressure Glow Discharge

by Valentin Boutrouche and Juan Pablo Trelles

Plasma 2024, 7(4), 920-938; https://doi.org/10.3390/plasma7040051 - 29 Nov 2024

The Atmospheric Pressure Glow Discharge (APGD) is a relatively simple and versatile plasma source used in a wide range of applications. Active cooling of the cathode can effectively mitigate instabilities, leading to glow-to-arc transitions. This study investigates the effect of varying the degree [...] Read more.

The Atmospheric Pressure Glow Discharge (APGD) is a relatively simple and versatile plasma source used in a wide range of applications. Active cooling of the cathode can effectively mitigate instabilities, leading to glow-to-arc transitions. This study investigates the effect of varying the degree of cathode cooling in APGD with a planar cathode in helium. The plasma flow model incorporates mass conservation, chemical species transport, momentum conservation, conservation of thermal energy of heavy species and of electrons, and electrostatics. The model is applied to time-dependent simulations through a three-dimensional computational domain describing the whole discharge, without geometric symmetry or steady-state assumptions. Simulations of an experimentally characterized APGD explore the effects of electric current and cathode cooling—ranging from thermally insulated to extreme convective cooling. Results show the formation of an annular region with high electric field over the cathode surface under conditions of high current and low cooling. Full article

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16 pages, 2963 KiB

Open AccessArticle

A Mechanism for Slow Electrostatic Solitary Waves in the Earth’s Plasma Sheet

by Gurbax Singh Lakhina and Satyavir Singh

Plasma 2024, 7(4), 904-919; https://doi.org/10.3390/plasma7040050 - 27 Nov 2024

An analysis of the Magnetospheric Multiscale (MMS) spacecraft data shows the presence of slow electrostatic solitary waves (SESWs) in the Earth’s plasma sheet, which have been interpreted as slow electron holes (SEHs). An alternative mechanism based on slow ion-acoustic solitons is proposed for [...] Read more.

An analysis of the Magnetospheric Multiscale (MMS) spacecraft data shows the presence of slow electrostatic solitary waves (SESWs) in the Earth’s plasma sheet, which have been interpreted as slow electron holes (SEHs). An alternative mechanism based on slow ion-acoustic solitons is proposed for these SESWs. The SESWs are observed in the region where double humped ion distributions and hot electrons co-exist. Our theoretical model considers the plasma in the SESW region to consist of hot electrons with a vortex distribution, core Maxwellian protons drifting parallel to the magnetic field, B and beam protons drifting anti-parallel to B. Parallel propagating nonlinear ion-acoustic waves are studied using the Sagdeev pseudopotential technique. The analysis yields four types of modes, namely, two slow ion-acoustic (SIA1 and SIA2) solitons and two fast ion-acoustic (FIA1 and FIA2) solitons. All solitons have positive potentials. Except the FIA1 solitons which propagate parallel to B; the other three types propagate anti-parallel to B. Good agreement is found between the amplitudes of electrostatic potential, the electric field, the widths and speed of SIA1 and SIA2 solitons, and the observed properties of SESWs by the MMS spacecraft. Full article

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13 pages, 4072 KiB

Open AccessArticle

Electrochemical Reactions at the Boundary Areas Between Cold Atmospheric Pressure Plasma, Air, and Water

by Jamiah Thomas and Alexander G. Volkov

Plasma 2024, 7(4), 891-903; https://doi.org/10.3390/plasma7040049 - 25 Nov 2024

Cited by 1

A cold atmospheric-pressure He-plasma jet (CAPPJ) interacts with air and water, producing reactive oxygen and nitrogen species (RONS), including biologically active ions, radicals, and molecules such as NO_x, H₂O₂, HNO₃, HNO₂, and O [...] Read more.

A cold atmospheric-pressure He-plasma jet (CAPPJ) interacts with air and water, producing reactive oxygen and nitrogen species (RONS), including biologically active ions, radicals, and molecules such as NO_x, H₂O₂, HNO₃, HNO₂, and O₃. These compounds can activate interfacial redox processes in biological tissues. The CAPPJ can oxidize N₂ to HNO₃ and water to H₂O₂ at the interface between plasma and water. It can also induce the oxidation of water-soluble redox compounds in various organisms and in vitro. This includes salicylic acid, hydroquinone, and mixtures of antioxidants such as L (+)-ascorbic acid sodium salt with NADPH. It can react with redox indicators, such as ferroin, in a three-phase system consisting of air, CAPPJ, and water. Without reducing agents in the water, the CAPPJ will oxidize the water and decrease the pH of the solution. When antioxidants such as ascorbate, 1,4-hydroquinone, or NADPH are present in the aqueous phase, the CAPPJ oxidizes these substances first and then oxidizes water to H₂O₂. The multielectron mechanisms of the redox reactions in the plasma-air/water interfacial area are discussed and analyzed. Full article

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14 pages, 4583 KiB

Open AccessArticle

Gliding Arc/Glow Discharge for CO₂ Conversion: The Role of Discharge Configuration and Gas Channel Thickness

by Svetlana Lazarova, Tsvetelina Paunska, Veselin Vasilev, Khristo Tarnev, Snejana Iordanova and Stanimir Kolev

Plasma 2024, 7(4), 877-890; https://doi.org/10.3390/plasma7040048 - 21 Nov 2024

This work investigates CO₂ conversion using atmospheric pressure low-current gliding discharges (GD). The following three modifications are studied: classic GD; magnetically accelerated GD (MAGD); and magnetically retarded GD (MRGD). In the latter two, permanent magnets produce a magnetic field that either accelerates [...] Read more.

This work investigates CO₂ conversion using atmospheric pressure low-current gliding discharges (GD). The following three modifications are studied: classic GD; magnetically accelerated GD (MAGD); and magnetically retarded GD (MRGD). In the latter two, permanent magnets produce a magnetic field that either accelerates or retards the discharge downstream. The gas flow is confined between quartz plates and the electrodes, with varying channel thicknesses. The magnetic configurations improve the performance compared to the classic GD, with up to 30% higher energy efficiency and up to a 50% higher conversion rate. The highest conversion rate is 11–12% with 10% energy efficiency, while the highest efficiency is 40% with 5% conversion, achieved with MRGD and MAGD at channel thicknesses of 2 mm and 3 mm. Full article

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10 pages, 3000 KiB

Open AccessArticle

Polymerization of Sodium 4-Styrenesulfonate Inside Filter Paper via Dielectric Barrier Discharge Plasma

by Samira Amiri Khoshkar Vandani, Lian Farhadian, Alex Pennycuick and Hai-Feng Ji

Plasma 2024, 7(4), 867-876; https://doi.org/10.3390/plasma7040047 - 11 Nov 2024

Cited by 1

This work explores the polymerization of sodium 4-styrenesulfonate (NaSS) inside filter paper using dielectric barrier discharge (DBD) plasma and its application in the environmental field. The plasma-based technique, performed under mild conditions, solves common problems associated with conventional polymerization inside porous materials. The [...] Read more.

This work explores the polymerization of sodium 4-styrenesulfonate (NaSS) inside filter paper using dielectric barrier discharge (DBD) plasma and its application in the environmental field. The plasma-based technique, performed under mild conditions, solves common problems associated with conventional polymerization inside porous materials. The polymerization process was monitored using Fourier-transform infrared (FTIR) spectroscopy, which confirmed the consumption of double bonds, particularly in NaSS samples containing the optimal concentration of crosslinker divinyl benzene (DVB) (0.25% wt). Our work demonstrates the effectiveness and promise of DBD plasma as a substitute polymerization approach, especially for those in porous materials. Full article

(This article belongs to the Special Issue Recent Advances of Dielectric Barrier Discharges)

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