Magnetic Field Flux Research Articles

PDM Klein–Gordon oscillators in cosmic string spacetime in magnetic and Aharonov–Bohm flux fields within the Kaluza–Klein theory

In the cosmic string spacetime and within Kaluza–Klein theory (KKT) backgrounds (indulging magnetic and Aharonov-Bohm flux fields), we introduce and study position-dependent mass (PDM) Klein–Gordon (KG) oscillators. The effective PDM is introduced as a deformation/defect in the momentum operator. We show that there are four different ways to obtain KG-oscillator. Two of which are readily known and the other two are obtained as byproducts of PDM settings. Next, we provide a thorough analysis on the corresponding spectra under different parametric effects, including the curvature parameter’s effect. Such analysis is used as a reference/lead model which is used in the discussion of different PDM KG-oscillators models: a mixed power-law and exponential type PDM model that yields a pseudo-confined PDM KG-oscillator in cosmic string spacetime within KKT (i.e., the PDM KG-oscillators are confined in their own PDM manifested Cornell-type confinement), and a PDM KG-oscillator confined in a Cornell-type potential. Moreover, we extend our study and discuss a non-Hermitian PT-symmetric PDM-Coulombic-type KG-particle model in cosmic string spacetime within KKT.

The Importance of Horizontal Poynting Flux in the Solar Photosphere

Abstract The electromagnetic energy flux in the lower atmosphere of the Sun is a key tool to describe the energy balance of the solar atmosphere. Current investigations on energy flux in the solar atmosphere focus primarily on the vertical electromagnetic flux through the photosphere, ignoring the Poynting flux in other directions and its possible contributions to local heating. Based on a realistic Bifrost simulation of a quiet-Sun (coronal hole) atmosphere, we find that the total electromagnetic energy flux in the photosphere occurs mainly parallel to the photosphere, concentrating in small regions along intergranular lanes. Thereby, it was possible to define a proxy for this energy flux based on only variables that can be promptly retrieved from observations, namely, horizontal velocities of the small-scale magnetic elements and their longitudinal magnetic flux. Our proxy accurately describes the actual Poynting flux distribution in the simulations, with the electromagnetic energy flux reaching 1010 erg cm−2 s−1. To validate our findings, we extended the analysis to Sunrise/IMaX data. First, we show that Bifrost realistically describes photospheric quiet-Sun regions, as the simulation presents similar distributions for line-of-sight magnetic flux and horizontal velocity field. Second, we found very similar horizontal Poynting flux proxy distributions for the simulated photosphere and observational data. Our results also indicate that the horizontal Poynting flux in the observations is considerably larger than the vertical electromagnetic flux from previous observational estimates. Therefore, our analysis confirms that the electromagnetic energy flux in the photosphere is mainly horizontal and is most intense in localized regions along intergranular lanes.

Berry-phase interpretation of thin-film micromagnetism

Magnetic flux densities (B-fields) and field intensities (H-fields) in thin films are investigated from the viewpoints of Berry phase and topological Hall effect. The well-known origin of the topological Hall effect is an emergent B-field originating from the Berry phase of conduction electrons, but Maxwell’s equations predict the relevant perpendicular component Bz to be zero. This paradox is solved by treating the electrons as point-like objects in Lorentz cavities. These cavities can also be used to interpret magnetization measurements in the present and other contexts, but structural and magnetic inhomogeneities lead to major modifications of the Lorentz-hole picture.

Influence of External Magnetic and Aharanov-Bohm (AB) Fields on the Energy Spectra of the Modified Kratzer plus Screened Coulomb Potential

In this article, the modified Kratzer plus screened Coulomb potential is scrutinized taking into consideration the effects of magnetic and AB flux fields within the non-relativistic regime using the Nikiforov-Uvarov-Functional Analysis method (NUFA) method. The energy equation and wave function of the system are obtained in close form. We find that the totality of effects these fields result in removal of degeneracy and raising the bound state energy of the system. More so, it could be concluded that to control the energy spectra of this system, the AB-flux and magnetic field will do so greatly. The results from this study can be applied in condensed matter physics, atomic and molecular physics.

Atwood’s Machine and Electromagnetic Induction: A Real Quantitative Experiment to Analyze Students’ Ways of Reasoning

We report a research-based proposal on electromagnetic induction within the theoretical framework of the Model of Educational Reconstruction. The proposal is based on a sequence of inquiry-based experimental activities centered on hands-on materials and Real-Time quantitative experiments, through which students explore the phenomenology of electromagnetic induction. The sequence was planned to address Faraday-Neumann-Lenz law analyzing the involved physics quantities and constructing quantitative relationships between them. Our hypothesis was based on the idea that phenomenological explorations performed through online sensors promote a functional understanding of electromagnetic induction and help students to face the conceptual knots highlighted by international literature about these phenomena. The educational sequence was proposed to a sample of 87 high school students with the aim of analyzing the evolution of the educational processes employing a set of inquiry-based tutorials. The qualitative analysis of students’ answers demonstrates that students increased their knowledges in the analysis of electromagnetic induction phenomena recognizing the fundamental role of time-variation of the magnetic field flux in the Faraday-Neumann-Lenz law.

Entropy analysis in an unsteady MHD flow of a radiating fluid through a vertical channel filled with a porous medium.

This paper investigates the blended effects of thermal buoyancy, magnetic field and radiative heat flux on the unsteady flow of an electrically conducting fluid through a permeable walled passageway filled with a penetrable medium. The model non-linear partial differential equations are obtained and solved analytically using separation of variable techniques and numerical for fluid velocity and fluid temperature. The two functions are then used to obtain entropy generation rate, skin friction, Nusselt number and the Bejan number. The effects of manifold novel parameters on the overall flow structure and thermal putrefaction are displayed graphically and discussed. One of the crucial findings of the current model is that entropy generation rate diminished temporally and with an upsurge in a magnetic field but amplified with a soar in porous medium permeability, thermal buoyancy and fluid Prandtl number.

Normal Stress of a Micro–Nano Magnetorheological Elastomer

In this paper, a kind of micro-nano magnetorheological elastomer (MRE), containing nano-Fe₃O₄, is prepared, and the normal mechanical property of micro-nano MRE is analyzed. Firstly, micro-nano MRE with different contents of nano-magnetic particles is prepared, and the microscopic static analysis is carried out by establishing a microscopic force model. Secondly, in order to investigate the normal mechanical properties of micro-nano MRE, an experimental platform is built, and its magnetic field flux is simulated by the finite element analysis software ANSYS. The results show that the maximum compressive elastic modulus of micro-nano MRE, containing 10% nano Fe₃O₄ particles, is 2. 89 MPa, which is 149% of the traditional MRE under the same current. The normal stress of micro-nano MRE is significantly improved, which provides a new method for the development of high-performance MRE.

The polarization angle in the wings of Ca I 4227: A new observable for diagnosing unresolved photospheric magnetic fields

Context. When observed in quiet regions close to the solar limb, many strong resonance lines show conspicuous linear polarization signals, produced by scattering processes (i.e., scattering polarization), with extended wing lobes. Recent studies indicate that, contrary to what was previously believed, the wing lobes are sensitive to the presence of relatively weak longitudinal magnetic fields through magneto-optical (MO) effects. Aims. We theoretically investigate the sensitivity of the scattering polarization wings of the Ca I 4227 Å line to the MO effects, and we explore its diagnostic potential for inferring information on the longitudinal component of the photospheric magnetic field. Methods. We calculate the intensity and polarization profiles of the Ca I 4227 Å line by numerically solving the problem of the generation and transfer of polarized radiation under non-local thermodynamic equilibrium conditions in one-dimensional semi-empirical models of the solar atmosphere, taking into account the joint action of the Hanle, Zeeman, and MO effects. We consider volume-filling magnetic fields as well as magnetic fields occupying a fraction of the resolution element. Results. In contrast to the circular polarization signals produced by the Zeeman effect, we find that the linear polarization angle in the scattering polarization wings of Ca I 4227 presents a clear sensitivity, through MO effects, not only to the flux of the photospheric magnetic field, but also to the fraction of the resolution element that the magnetic field occupies. Conclusions. We identify the linear polarization angle in the wings of strong resonance lines as a valuable observable for diagnosing unresolved magnetic fields. Used in combination with observables that encode information on the magnetic flux and other properties of the observed atmospheric region (e.g., temperature and density), it can provide constraints on the filling factor of the magnetic field.

Borehole Magnetometry Test for Evaluating a Caisson’s Reinforced Depth: Experimental Results and Theoretical Modeling

Abstract The borehole magnetometry (BM) test was performed to evaluate the foundation reinforcement depth at a site where a telecommunication tower is supported by a single 2.3-m-diameter caisson foundation of known as-built design. An optical televiewer probe containing a three-axial fluxgate magnetometer was lowered into a vertical borehole 2.35 m distant from the center of the caisson and the profiles for the total magnetic field flux density, and its vertical component were acquired and used to generate, by subtracting the International Geomagnetic Reference Field background, the profiles for the total, BA, and vertical component, Bz,A, anomalous magnetic field. Four distinct graphical methods were used to evaluate the reinforced depth from the anomalous profiles and their first- and second-order derivatives. Two of the methods, including the one proposed in this study, based on locating the inflection points in the derivative profiles, evaluated the reinforced depth very close to the as-built depth (8.0 m). The reinforcement intensity of magnetization was then evaluated using the BA profile and a method based on the bipolar model. Theoretical modeling of BA and Bz,A and the derivative profiles was then performed using a three-dimensional prismatic model. By comparing modeled and experimental results, the induced magnetization was found to be an unsuited modeling assumption, with remanent magnetization being a better representation of the magnetic field around the caisson’s steel reinforcement, in agreement with the theory, given the high Koenigsberger ratio for steel. Also, the modeling revealed the need for a more complex representation of the magnetic sources, with added prisms to represent the effects of a magnetically-noisy environment and above-ground structures, as well as the presence of inhomogeneity and polarization changes along the reinforcement length.

ОРГАНІЗАЦІЯ АСИНХРОННОЇ КОМУТАЦІЇ ТРАНСФОРМАТОРА З УРАХУВАННЯМ ІНЕРЦІЙНОСТІ ЕЛЕКТРОМАГНІТНИХ ПРОЦЕСІВ

Transformers are an indispensable component of various types of electrical circuits. Various restrictions are imposed on the transformer switching operation, which are caused by the functional purpose of the systems, their configuration, parameters and characteristics of existing or available switching components or devices and associated transient processes.When the power transformer is switched on asynchronously, current surges in its primary winding, including in modes close to the minimum load, may exceed its nominal current by several times. Such processes are undesirable from the point of view of energy efficiency, electromagnetic compatibility, transformer reliability and the functioning of protection systems. The purpose of the study is to organize the switching of the transformer in such a way that it achieves its output to a stable mode of operation with a minimum amplitude of the input current and the duration of the transition process, without extreme manifestations in the switching process.Algebraic, graphic, and simulation-visual aspects of the analysis of the processes occurring during power transformer commutation are considered in the work. It is shown that the repeated switching on of the transformer can lead to a significantly larger current surge in the primary winding compared to the first switching on, and the reason for this phenomenon is the magnitude of the magnetic flux at the time of repeated commutation. It is shown that the value of the flux and its change depends on the amount of load on the secondary winding, and lower values of the load correspond to higher values of the rate of decline of the magnetic flux of the transformer core and vice versa. The following switching algorithm of the transformer is recommended, in which each subsequent switching on of the transformer will start with a close to zero value of the magnetic field flux

High-Efficiency Drive Method of Adjustable Field IPMSM Utilizing Magnetic Saturation

This paper describes a high-efficiency drive method of an adjustable field Interior Permanent Magnet Synchronous Motor (IPMSM) utilizing magnetic saturation. The adjustable field IPMSM can control the magnetic field flux using magnetic saturation caused by a modulation current. In general, it is said that motor efficiency is high at operating points where the copper loss and the iron loss are balanced. However, the high-efficiency drive range of a conventional PMSM is narrow because the magnetic field of the PMSM is constant. On the other hand, it is possible in the proposed adjustable field IPMSM to expand the high-efficiency drive range because the field amount can freely be adjusted by the modulation current. Therefore, this paper examines an optimal modulation current for a high-efficiency operation. To derive the optimal modulation current, losses and efficiency of the proposed adjustable field IPMSM are formulated based on the measured motor parameters. In addition, it is confirmed from several experimental tests that the high-efficiency driving range can be expanded due to the optimal modulation current.

IMPROVING THE PERFORMANCE CHARACTERISTICS OF MACHINE PARTS BASED ON THE COMBINED INFLUENCE OF STRONG MAGNETIC FIELDS

Magnetic treatment is a promising method of hardening. Metal exposed to alternating magnetic fields changes the performance properties of the surface layer of a combination of magnetic and ultrasonic effects, provides a combined method of processing and strengthening surfaces of machine parts, which eliminates the main disadvantages of magnetic and electrical hardening — instability of physical and mechanical properties of this layer with detail.
 The purpose of the work is to investigate the possibility of improving the performance of machine parts based on the combined effect of strong magnetic fields.
 The study of the use of a uniform flux of magnetic fields generated by powerful permanent magnets was performed to affect the material volume of non-grinding plates of the cutting tool CNMG_120508E-M. The effect of uniform magnetic flux is initiated as a result of resonant oscillations of the sample caused by broadband exposure of equal amplitude by means of a "white noise" generator and a piezo emitter.
 The authors found that as a result of volumetric strengthening of non-grinding plates of carbide cutting tools, by exposure to polyfrequency oscillations in the form of a broadband frequency spectrum of equal amplitudes, a significant reduction in dimensional wear of the plates is achieved. Adding mechanical vibrations to the samples in a uniform constant magnetic field allowed to achieve volumetric hardening of the samples from 150 HB to 240 ÷ 250 HB, ie 60 ÷ 65% in 10—12 minutes, which is the hardening of the samples by 5—6% in one minute.
 The work on determining the relationship of changing properties with processing time, frequency range, amplitude and other modes to find the optimal values ​​of processing parameters, has great prospects for the ability to obtain a set of performance characteristics, control external and internal properties of products.

Multi-point analysis of coronal mass ejection flux ropes using combined data from Solar Orbiter, BepiColombo, and Wind

Context. The recent launch of Solar Orbiter and the flyby of BepiColombo opened a brief window during which these two spacecraft, along with the existing spacecraft at L1, were positioned in a constellation that allowed for the detailed sampling of any Earth-directed coronal mass ejection (CME). Fortunately, two such events occurred during this time period with in situ detections of an interplanetary coronal mass ejection (ICME) by Solar Orbiter on the 2020 April 19 and 2020 May 28. These two events were subsequently observed in situ by BepiColombo and Wind as well around a day later. Aims. We attempt to reconstruct the observed in situ magnetic field measurements for all three spacecraft simultaneously using an empirical magnetic flux rope model. This allows us to test the validity of our flux rope model on a larger and more global scale. It additionally allows for cross-validation of the analysis with different spacecraft combinations. Finally, we can also compare the results from the in situ modeling to remote observations obtained from the STEREO-A heliospheric imagers, which were able to capture the interplanetary evolution of the coronal mass ejections. Methods. We made use of the 3D coronal rope ejection model (3DCORE) in order to simulate the ICME evolution and reconstruct the measured flux rope signatures at the spacecraft positions. For this purpose, we adapted a previously developed approximate Bayesian Computation sequential Monte-Carlo (ABC-SMC) fitting algorithm for the application to multi-point scenarios. This approach not only allows us to find global solutions, within the limits of our model, but to also naturally generate error estimates on the model parameters and detect potential ambiguities. Results. We show that we are able to generally reconstruct the flux rope signatures at three different spacecraft positions simultaneously by using our model in combination with the flux rope fitting algorithm. For the well-behaved April 19 ICME, our approach works very well and displays only minor deficiencies. The May 28 ICME, on the other hand, shows the limitations of our approach for less clear ICME measurements or strongly deformed shapes. Unfortunately, the usage of multi-point observations for these events does not appear to solve inherent issues, such as the estimation of the magnetic field twist or flux rope aspect-ratios due to the specific constellation of the spacecraft positions, which all lie near the ecliptic plane. As our general approach can be used for any fast-forward simulation based model, we give a blueprint for future studies using more advanced ICME models.

Exponential shock wave in perfectly conducting self-gravitating rotational axi-symmetric dusty gas with magnetic field, radiative and conductive heat fluxes

In the present paper, we study the exponential shock propagation in a self-gravitating rotational axisymmetric perfectly conducting mixture of van der Waal gas and solid particles with magnetic field either axial or azimuthal and radiative and conductive heat fluxes. In our model, the solid particles are distributed continuously in the mixture and are chemically inert, and the equilibrium conditions for flow are preserved in the entire region of flow field behind shock wave. In a thick gray gas model case, the radiation is assumed to be of diffusion type. The Fourier's heat conduction law is used to express the heat conduction. The effects of the problem parameters variations are discussed. It is shown that the density of micro size solid particles to the gas initial density ratio or the gravitational parameter or the rotational parameter or the gas adiabatic index has effects to enhance the shock wave strength. Also, it is derived that an increase in the nonidealness of the gas, Alfvén Mach number, and the mass concentration of solid particles in the mixture have decaying effects on the strength of shock wave. It is shown that the shock wave is stronger when magnetic field is axial and weaker for azimuthal magnetic field.

MHD FLOW OF A REACTING AND RADIATING NANOLIQUID PAST AN INCLINED HEATED PERMEABLE PLATE: ANALYSIS OF ENTROPY GENERATION

This paper examines the aggregate impacts of magnetic field, thermophoresis, Brownian motion, variable viscosity, chemical reaction and radiative heat flux on the thermal putrefaction and immanent irreversibility of a channelling nanoliquid film flowing along with a slanted heated permeable plate. Following Buongiorno approach, the two-phase nanoliquid nonlinear model is obtained and addressed numerically using shooting technique as well as the Runge-Kutta- Fehlberg integration scheme. Effects of various emerging parameters on the overall flow structure with heat and mass transfer characteristics including entropy generation rate and Bejan number are displayed using diagrams and discussed. It is found that the entropy generation rate lessened with an upsurge in a magnetic field but heightened with an elevation in the buoyancy forces.

Signatures of topological transitions in the spin susceptibility of Josephson junctions

We theoretically investigate how the spin susceptibility of a planar Josephson junction is affected when the system transits into the topological superconducting state. We show that the magnetic flux and magnetic field dependence of the spin susceptibility closely maps the phase diagram of the system. In the absence of an external magnetic flux the system can self-tune into the topological superconducting state by minimizing its free energy. Self-tuned topological transitions are accompanied by sharp peaks in the spin susceptibility, which can therefore be use as measurable fingerprints for detecting the topological superconducting state. Away from the peaks, the amplitude of the spin susceptibility can provide qualitative information about the relative size of the topological gap. The signatures in the spin susceptibility are robust, even in junctions with narrow superconducting leads, where critical current minima may no longer serve as an indication of topological phase transitions. Numerical simulations are complemented with simplified analytical models capable of capturing the main features predicted for the spin susceptibility behavior. The predicted results could be particularly relevant for future experiments on realization and detection of the topological superconducting state in planar Josephson junctions.

Magnetic Field and Energetic Particle Flux Oscillations and High‐Frequency Waves Deep in the Inner Magnetosphere During Substorm Dipolarization: ERG Observations

AbstractUsing Exploration of energization and Radiation in Geospace (ERG or Arase) spacecraft data, we studied low‐frequency magnetic field and energetic particle flux oscillations and high‐frequency waves deep in the inner magnetosphere at a radial distance of ~4–5 during substorm dipolarization. The magnetic field oscillated alternately between dipole‐like and taillike configuration at a period of 1 min during dipolarization. When the magnetic field was dipole‐like, the parallel magnetic component of the Pi2 waves was at trough. Both energetic ion and electron fluxes with a few to tens of kiloelectronvolts enhanced out of phase, indicating that magnetosonic waves were in slow mode. Field‐aligned currents also oscillated. These observations are consistent with signatures of ballooning instability. In addition, we found that broadband waves from the Pi1 range to above the electron cyclotron frequency tended to appear intermittently in the central plasma sheet near dipole‐like configuration.

Development of a Consequent-Pole-PM-Type Axial-Gap Motor With DC Field Winding

Permanent magnet synchronous motors for electric vehicles should meet three criteria: high maximum torque, high efficiency at low torque, and constant output in a wide speed range. However, meeting these criteria has come with a trade-off in terms of the magnitude of the field magnetic flux. We propose a consequent-pole-PM-type axial-gap motor with ferrite PMs and field windings, which has structure variable field magnetic flux. In order to examine the operational characteristics of the proposed motor, we produced and tested a prototype. Experimental results show that the proposed structure meets all of the three criteria above.

Exploring the limits of Solov'ev profiles

Solov'ev profiles, which are the simplest that allow analytic solutions for the Grad–Shafranov (G–Sh) equation, can reproduce some features of experimental equilibria when the free parameters are appropriately chosen. The purpose of this paper is to study how the freedom in the choice of the parameters and the number of terms in a series solution to the homogeneous equation affect the equilibria obtained. Keeping equatorial symmetry for simplicity, the limits of this approach are tested. The behavior of the solutions for devices with different sizes and aspect ratios, such as ITER, ST40, and MAST-U, is studied, and also examples in which physically relevant figures of merit are found. While the toroidal current density profile is necessarily limited, and cannot be realistic, some of the main features of the magnetic field flux surfaces can be obtained. Three sets of parameters are distinguished, so their roles can be better understood: (1) The geometrical parameters of the boundary conditions, which determine the last closed magnetic field flux surface, (2) The general parameters of an experiment, such as the plasma current, the major radius, and the toroidal magnetic field at the major radius, and (3) the Solov'ev parameters. The regions of acceptable values for the Solov'ev parameters, are identified, depending on the topology of the solutions.

Mechanically induced electric and magnetic fields in the bending and symmetric-shear deformations of a microstructure-dependent FG-MEE composite beam

A new FG-MEE composite microbeam model is developed using a general higher-order deformation theory (GHDT) to account for the symmetric thickness-shear and thickness-stretch deformations of a beam and a modified couple stress theory (MCST) to describe the microstructure-dependent size effect. Based on the basic assumption of field variables and Hamilton’s principle, the one-dimensional second-order coupled equations of motion and complete boundary conditions are obtained simultaneously. The present coupled equations include the microstructure dependence and higher-order extensions, which can reduce to the size-dependent Bernoulli-Euler, Timoshenko and Mindlin-Medick theories. Static problems of a simply supported beam loaded by uniform loading and a concentrated second-order moment are analytically solved by directly applying the newly developed equations. For the bending case, the numerical results show that the magnitudes of displacement, electric, magnetic, stress, electric displacement and magnetic flux fields are smaller than those predicted by classical theory. In addition, it is found that FG parameter can be used to control the electric and magnetic fields. For the concentrated second-order moment case, a new phenomenon of local electric and magnetic fields are demonstrated in the present FG-MEE composite microbeam structure. These results are useful for theoretically/numerically estimating or designing the MEMS of FG-MEE composites.