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Two types of filamentary currents (FCs) were observed inside a magnetic flux rope at the magnetopause by the Magnetospheric Multiscale mission. The first FC is identified as an electron vortex, while the other is a reconnecting current sheet. Stochastic electric fields were generated within the FCs, resulting in electron acceleration up to a few keV, similar to recent simulations of electron acceleration inside vortex, which is a second‐order Fermi acceleration. Furthermore, two FCs propagated at different speeds, causing compression in the region between them. Energetic electrons up to 200 keV were detected in the compressed region and displayed a double power‐law spectrum. Observations suggest that the electrons were mainly accelerated by betatron mechanism in the compressed region. The formation, evolution, and interaction of FCs provide a novel mechanism for electron acceleration. These results clearly show the significance of electron‐scale dynamics within flux rope. Plain Language Summary Magnetic reconnection is a fundamental plasma process by which magnetic energy is converted into the kinetic energy of charged particles. Understanding the acceleration mechanisms for the energetic electrons during magnetic reconnection is a long‐standing question in the study of space and astrophysical plasmas. Using Magnetospheric Multiscale observations at Earth's magnetopause, we present in situ evidence of electron acceleration up to 200 keV between two consecutive filamentary currents (FCs) inside a magnetic flux rope. Two FCs propagate at different speeds, with the second moving faster, thus causing a compressed region between them. These results provide an important new way for electron acceleration in magnetic reconnection. Key Points Two types of filamentary currents (FCs) were observed near the center of a magnetic flux rope Stochastic electric fields were generated inside two FCs and accelerated electrons Electrons were accelerated up to 200 keV in the compressed region between two currents by the betatron mechanism

ZnO‐based varistors are today the established technology for overvoltage surge protection on all voltage levels, ranging from a few volts in electronics up to >1 MV in ultra‐high voltage power systems. All these applications are based on the highly nonlinear, fast, and reversible electrical switching characteristics of a single grain boundary with a switching voltage of ≈3.2–3.6 V in the semiconducting polycrystalline ZnO ceramics. For the many intriguing steady‐state and time‐dependent transport properties, the model of the double Schottky barrier at each grain boundary provides a solid frame for the microscopic understanding, provided the knowledge gained on the electronic bulk and interface defects states and the hot electron effects at breakdown are consistently integrated into the model. The commonalities of the many different varistor formulations in use, and the parameters to be optimized to achieve a specific target for the electrical performance, then become evident from the ‘double Schottky barrier defect’ model. Interfacial and bulk defects, characteristic for the ZnO crystal lattice, control the grain boundary potential barriers and hence the I‐V characteristics. Their densities vary with the material formulation and processing parameters, whereas their energy positions are at fixed positions within the band gap of ZnO, independent of the manufacturing parameters used. The paper describes the present state of understanding of the varistor phenomena on the micro‐, meso‐, and macroscopic length scales, which are relevant for the basic and applied research on varistor materials and their applications. Besides the single junction properties, the main technically and scientifically challenging topics needed to be understood are the filamentary current flow in real microstructures, the inhomogeneities present on all length scales and the long‐term stability. Knowing the limits in energy absorption and high current withstand stresses are key inputs for the development engineer for the design of surge arresters consisting of a few or many hundred individual varistor elements. The scientific backbone summarized in the present overview is a good basis to tackle the few remaining open questions in future varistor research.

Turbulence in fluids is a ubiquitous, fascinating, and complex natural phenomenon that is not yet fully understood. Unraveling turbulence in high density, high temperature plasmas is an even bigger challenge because of the importance of electromagnetic forces and the typically violent environments. Fascinating and novel behavior of hot dense matter has so far been only indirectly inferred because of the enormous difficulties of making observations on such matter. Here, we present direct evidence of turbulence in giant magnetic fields created in an overdense, hot plasma by relativistic intensity (1018W/cm2) femtosecond laser pulses. We have obtained magneto-optic polarigrams at femtosecond time intervals, simultaneously with micrometer spatial resolution. The spatial profiles of the magnetic field show randomness and their k spectra exhibit a power law along with certain well defined peaks at scales shorter than skin depth. Detailed two-dimensional particle-in-cell simulations delineate the underlying interaction between forward currents of relativistic energy \"hot\" electrons created by the laser pulse and \"cold\" return currents of thermal electrons induced in the target. Our results are not only fundamentally interesting but should also arouse interest on the role of magnetic turbulence induced resistivity in the context of fast ignition of laser fusion, and the possibility of experimentally simulating such structures with respect to the sun and other stellar environments.

This paper presents a practical way of using the method of evaluating the metrological properties of eddy current sensors. The idea of the proposed approach consists of employing a mathematical model of an ideal filamentary coil to determine equivalent parameters of the sensor and sensitivity coefficients of tested physical quantities. These parameters were determined on the basis of the measured value of the real sensor’s impedance. The measurements were carried out with an air-core sensor and an I-core sensor while they were positioned at different distances from the surface of tested copper and bronze plates. An analysis of the influence of the coil’s position in relation to the I core on the equivalent parameters was also carried out, and the interpretation of the results obtained for various sensor configurations was presented in a graphical form. When equivalent parameters and sensitivity coefficients of examined physical quantities are known, it is possible to compare even very different sensors with the employment of one measure. The proposed approach makes it possible to make a significant simplification of the mechanisms of calibration of conductometers and defectoscopes, computer simulation of eddy current tests, creating the scale of a measuring device, and designing sensors.

Currently, halide perovskites (HPs) are gaining traction in multiple applications, such as photovoltaics and resistive switching (RS) devices. In RS devices, the high electrical conductivity, tunable bandgap, good stability, and low-cost synthesis and processing make HPs promising as active layers. Additionally, the use of polymers in improving the RS properties of lead (Pb) and Pb-free HP devices was described in several recent reports. Thus, this review explored the in-depth role of polymers in optimizing HP RS devices. In this review, the effect of polymers on the ON/OFF ratio, retention, and endurance properties was successfully investigated. The polymers were discovered to be commonly utilized as passivation layers, charge transfer enhancement, and composite materials. Hence, further HP RS improvement integrated with polymers revealed promising approaches to delivering efficient memory devices. Based on the review, detailed insights into the significance of polymers in producing high-performance RS device technology were effectively understood.

Resistive switching memories are among the emerging next-generation technologies that are possible candidates for in-memory and neuromorphic computing. In this report, resistive memory-switching behavior in solution-processed trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) benzene–PVA-composite-based aryl acrylate on an ITO-coated PET device was studied. A sandwich configuration was selected, with silver (Ag) serving as a top contact and trans, trans-1,4-bis-(2-(2-naphthyl)-2-(butoxycarbonyl)-vinyl) benzene–PVA-composite-based aryl acrylate and ITO-PET serving as a bottom contact. The current–voltage (I–V) characteristics showed hysteresis behavior and non-zero crossing owing to voltages sweeping from positive to negative and vice versa. The results showed non-zero crossing in the devices’ current–voltage (I–V) characteristics due to the nanobattery effect or resistance, capacitive, and inductive effects. The device also displayed a negative differential resistance (NDR) effect. Non-volatile storage was feasible with non-zero crossing due to the exhibition of resistive switching behavior. The sweeping range was −10 V to +10 V. These devices had two distinct states: ‘ON’ and ‘OFF’. The ON/OFF ratios of the devices were 14 and 100 under stable operating conditions. The open-circuit voltages (Voc) and short-circuit currents (Isc) corresponding to memristor operation were explained. The DC endurance was stable. Ohmic conduction and direct tunneling mechanisms with traps explained the charge transport model governing the resistive switching behavior. This work gives insight into data storage in terms of a new conception of electronic devices based on facile and low-temperature processed material composites for emerging computational devices.

This article presents an innovative technique for detecting flaws in conductive materials by using an ideal filamentary coil. To characterize such a coil accurately and explicitly, it is sufficient to be in possession of merely two parameters: the radius of the circle within which all the turns are located and the distance of the coil from the tested surface. The mathematical model derived using the truncated region eigenfunction expansion method enables the calculation of the changes in the components of the filamentary coil impedance that are the result of positioning the coil close to the conductive material with a hole. Because of this, the air-cored coil model can be replaced with a much simpler filamentary coil model. This solution makes it is possible to detect various types of holes (internal, surface, subsurface or through) occurring in both multilayer magnetic and non-magnetic materials. The derived results were verified by means of measurements and numerical calculations based on the finite element method. Very good agreement was observed in both cases. The paper contains the source code implemented in Matlab, which is used to for calculations.