Cold atmospheric plasma source for surface sterilization: design and simulation H.O Coelho Júnior, J.V.R Bitencourt, J.C.M Almeida, L.M Neves, M.A Cardoso, et al. Revista Brasileira De Ensino De Fisica, 2026 Plasmas have several applications in industry, mainly in surface treatment. This work aims to apply the properties of cold atmospheric plasmas for the sterilization of surfaces, objects, and environments. For this an atmospheric plasma source has been developed using commercial-off-the-shelf (COTS), which works with high frequencies, on the order of KHz, utilizing DC-pulsed signals. This approach allowed for a low-cost prototype that can be utilized in classrooms of physics, chemistry, and biology courses. Simulations were made to evaluate the circuit behavior and then compared with the prototyped circuit. This looped interaction allowed for fine-tuning of the simulation parameters, in order to achieve a similar result between simulation and bench measurements. Freecad 0.21, an open-source CAD software, was utilized to design the structure of the prototype, with several of its parts being 3D printed, in both filament and resin printers. Preliminary results of the biocide action using Peribacillus simplex demonstrate that the plasma source has a biocidal capability after 10 minutes of exposition.
Complexity-entropy analysis of solar photospheric turbulence: Hinode images of magnetic and Poynting fluxes Abraham C.-L. Chian, Haroldo V. Ribeiro, Erico L. Rempel, Rodrigo A. Miranda, Luis Bellot Rubio, et al. Astronomy and Astrophysics, 2025 The spatiotemporal inhomogeneous-homogeneous transition in the dynamics and structures of solar photospheric turbulence is studied by applying the complexity-entropy analysis to Hinode images of a vortical region of supergranular junctions in the quiet Sun. During a period of supergranular vortex expansion lasting 37.5 min, the spatiotemporal dynamics of the line-of-sight magnetic field and the horizontal electromagnetic energy flux displayed characteristics of an inverse turbulent cascade, as evidenced by the formation of a large magnetic coherent structure via the merger of two small magnetic elements trapped by a long-duration vortex. Consistent with Hinode observations, the magnetic and Poynting fluxes both exhibited an admixture of chaos and stochasticity in the complexity-entropy plane involving a temporal transition from low to high complexity and a temporal transition from high to low entropy during the period of vortex expansion.
Comparison of the performance of a cylindrical Hall thruster with different anode voltages via numerical simulations Mathematics in Engineering Science and Aerospace, 2024
Secondary instability generated on the equatorial plasma bubbles wall due to an interaction with midnight brightness wave Cosme Alexandre Oliveira Barros Figueiredo, Rodrigo A. Miranda, Cristiano Max Wrasse, Hisao Takahashi, Diego Barros, et al. Earth Planets and Space, 2023 Interaction between Equatorial Plasma Bubbles (EPBs) and midnight Brightness wave (MBW) was observed over Bom Jesus da Lapa (13.3° S, 43.5° W; Quasi-Dipole geomagnetic latitude of 14.1° S), using OI 630 nm all-sky images. On the night of December 22nd, 2019, an EPB was seen propagating eastward in its fossil stage until it interacted with an MBW. After the interaction, the west walls of EPBs generated secondary instabilities that can be associated with gradient drift instability (GDI) and/or Kelvin–Helmholtz instabilities (KHI). We suggest that the MBW contributed to generate a shear in the EPBs walls due to changes in the thermospheric dynamics, such as neutral wind in the F layer height. Furthermore, spectral analysis of the all-sky images suggests that GDI and/or KHI generated turbulence and helped to dissipate the EPBs.Graphical Abstract
Nonlinear dynamics in space plasma turbulence: temporal stochastic chaos A. C.-L. Chian, F. A. Borotto, T. Hada, R. A. Miranda, P. R. Muñoz, et al. Reviews of Modern Plasma Physics, 2022 Intermittent turbulence is key for understanding the stochastic nonlinear dynamics of space, astrophysical, and laboratory plasmas. We review the theory of deterministic and stochastic temporal chaos in plasmas and discuss its link to intermittent turbulence observed in space plasmas. First, we discuss the theory of chaos, intermittency, and complexity for nonlinear Alfvén waves, and parametric decay and modulational wave–wave interactions, in the absence/presence of noise. The transition from order to chaos is studied using the bifurcation diagram. The following two types of deterministic intermittent chaos in plasmas are considered: type-I Pomeau–Manneville intermittency and crisis-induced intermittency. The role of structures known as chaotic saddles in deterministic and stochastic chaos in plasmas is investigated. Alfvén complexity associated with noise-induced intermittency, in the presence of multistability, is studied. Next, we present evidence of magnetic reconnection and intermittent magnetic turbulence in coronal mass ejections in the solar corona and solar wind via remote and in situ observations. The signatures of turbulent magnetic reconnection, i.e., bifurcated current sheet, reconnecting jet, parallel/anti-parallel Alfvénic waves, and spiky dynamical pressure pulse, as well as fully developed turbulence, are detected at the leading edge of an interplanetary coronal mass ejection and the interface region of two merging interplanetary magnetic flux ropes. Methods for quantifying the degree of coherence, amplitude–phase synchronization, and multifractality of nonlinear multiscale fluctuations are discussed. The stochastic chaotic nature of Alfvénic intermittent structures driven by magnetic reconnection is determined by a complexity–entropy analysis. Finally, we discuss the relation of nonlinear dynamics and intermittent turbulence in space plasmas to similar phenomena observed in astrophysical and laboratory plasmas, e.g., coronal mass ejections and flares in the stellar-exoplanetary environment and Galactic Center, as well as chaos, magnetic reconnection, and intermittent turbulence in laser-plasma and nuclear fusion experiments.
Complexity of Magnetic-field Turbulence at Reconnection Exhausts in the Solar Wind at 1 au Rodrigo A. Miranda, Juan A. Valdivia, Abraham C.-L. Chian, Pablo R. Muñoz Astrophysical Journal, 2021 Magnetic reconnection is a complex mechanism that converts magnetic energy into particle kinetic energy and plasma thermal energy in space and astrophysical plasmas. In addition, magnetic reconnection and turbulence appear to be intimately related in plasmas. We analyze the magnetic-field turbulence at the exhaust of four reconnection events detected in the solar wind using the Jensen–Shannon complexity-entropy index. The interplanetary magnetic field is decomposed into the LMN coordinates using the hybrid minimum variance technique. The first event is characterized by an extended exhaust period that allows us to obtain the scaling exponents of higher-order structure functions of magnetic-field fluctuations. By computing the complexity-entropy index we demonstrate that a higher degree of intermittency is related to lower entropy and higher complexity in the inertial subrange. We also compute the complexity-entropy index of three other reconnection exhaust events. For all four events, the B L component of the magnetic field displays a lower degree of entropy and higher degree of complexity than the B M and B N components. Our results show that coherent structures can be responsible for decreasing entropy and increasing complexity within reconnection exhausts in magnetic-field turbulence.
