Variation Of Magnetic Field Strength Research Articles

The Lorentz Force at Work: Multiphase Magnetohydrodynamics throughout a Flare Lifespan

The hour-long, gradual phase of solar flares is well observed across the electromagnetic spectrum, demonstrating many multiphase aspects, where cold condensations form within the heated post-flare system, but a complete 3D model is lacking. Using a state-of-the-art 3D magnetohydrodynamic simulation, we identify the key role played by the Lorentz force through the entire flare lifespan, and show that slow variations in the post-flare magnetic field achieve the bulk of the energy release. Synthetic images in multiple passbands closely match flare observations, and we quantify the role of conductive, radiative, and Lorentz force work contributions from flare onset to decay. This highlights how the non-force-free nature of the magnetic topology is crucial to trigger Rayleigh–Taylor dynamics, observed as waving coronal rays in extreme ultraviolet observations. Our C-class solar flare reproduces multiphase aspects such as post-flare coronal rain. In agreement with observations, we find strands of cooler plasma forming spontaneously by catastrophic cooling, leading to cool plasma draining down the post-flare loops. As there is force balance between magnetic pressure and tension and the plasma pressure in gradual-phase flare loops, this has potential for coronal seismology to decipher the magnetic field strength variation from observations.

Analysis of Calophyllum Inophyllum Biodiesel Combustion with Variations of Magnetic Field Strength

The problems facing the world today are limited fossil fuels and increasing global warming due to fuel emissions. Therefore, there is a need to transition from fossil energy to alternative energy that is environmentally friendly and renewable. Biodiesel is an alternative material that can be used as a substitute for diesel fuel. This research aims to improve the combustion quality of calophyllum inophyllum biodiesel using the magnetic field influence method. The combustion test method uses a Bunsen burner and variations in magnetic strength of 4000 gauss, 8000 gauss and 12000 gauss are given. The equivalent ratios used in combustion analysis are 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1:1.1, and 1:1.2. The fuel and air flowing in the Bunsen pipe are heated to a constant temperature of 250°C for the fuel evaporation process. Then the resulting flame was analyzed for its combustion characteristics with RGB color variables, laminar burning velocity, and flame height. The research results show that the stronger the magnetic field effect, the more optimal the combustion quality will be. This is indicated by the increasingly strong magnetic field effect exerted on the flame, causing the red color intensity to decrease, the laminar burning velocity to increase, and the flame height to decrease. This is because the magnetic field can influence the movement of O2 molecules and cause a change in the orientation of the hydrocarbon from para to ortho. As a result, diffusion combustion becomes minimal and the combustion reaction becomes faster.

Magnetohydrodynamic hybrid nanofluid flow through moving thin needle considering variable viscosity and thermal conductivity

In modern science and technology, industrial applications that deal with the problem of continuously moving thin needle, surrounded with fluid in sectors like hot rolling, crystal growing, heat extrusion, glass fiber drawing, etc., are rapidly increasing. Such processes involve high temperatures which may affect the fluid properties that is, viscosity and thermal conductivity. So, it’s crucial to understand temperature-dependent fluid properties. Focused on these assumptions, the main objective of the current research work is to investigate how temperature-dependent fluid properties might improve the heat transfer efficiency and performance evolution of hybrid nanofluid in the presence of transverse magnetic field over a moving thin needle. Variable Prandtl number is also introduced to observe flow fluctuation, the effect of adding nanoparticles, and enhancement in heat transmission. The results are obtained for different needle thicknesses, temperature-dependent viscosity, temperature-dependent thermal conductivity, and heat generation. Moreover, Fe3O4/Graphene nanoparticles are considered to be dispersed in water. The governing partial differential equations of flow and heat transfer are transformed into a system of coupled nonlinear ordinary differential equations using analysis of similarity conversion. Subsequently, the numerical solution of the problem is attained by employing the MAPLE software. The fourth-fifth-order Runge-Kutta-Fehlberg (RFK45) approach is used by default in this MAPLE program to address the numerical problem of boundary value. The velocity and temperature field are pictured for different values of the parameters as well as physical quantities of interest such as skin friction coefficient and rate of heat transfer are visually depicted in graphs and tables. It is found that fluid motion and energy transport are highly regulated by the variation of magnetic field strength. As the volume fraction of Fe3O4 is increased, the heat generation, and thermal conductivity parameter vehemently enhance the temperature profile which leads to a rise in thermal boundary layer. A strong augmentation in the heat transfer rate has been found with the increment in the variable Prandtl number.

High-order Harmonics of a Kink Wave and a Narrow Quasiperiodic Fast-propagating Wave Train Excited Simultaneously in a Plasma Resonator

We present the observations of multimode kink waves and a narrow quasiperiodic fast-propagating (QFP) wave train in association with a jet on 2011 December 11. The jet impinged on a loop, which excited a propagating kink mode transitioning into a standing kink mode and also excited a QFP wave train away from the jet. Motion magnification is used to fit the higher harmonic standing wave oscillation profile with three periods at three different spatial locations. The periods have the ratio 6:3:2. The ratio of the fundamental mode to the second harmonic of the standing wave is about 1.95, suggesting that the magnetic field strength variation effect is strong enough to cancel out the density stratification. The differential emission measure is used to estimate the loop’s plasma property at these three points, and it found the density and the temperature are roughly constant. The magnetic field strength, B = 51 ± 16 G, is derived by the coronal seismology using the fundamental kink mode. It is striking to find that the the ratio of the second harmonic to the third harmonic of the kink wave coincides with that of the periods of the QFP wave train, and the ratio of periods is about 1.5 in both cases. We propose that the excitation of the high-order harmonics and the QFP wave train could be the nonlinear response of the steep density-gradient plasma interacting with electromagnetic field in the southwest foot region. This region, like a resonator, might play an important role in energy reservoir capture and act as a frequency filter to generate propagating waves of particular frequencies.

Thermal and phase change process analysis in a porous vented circular cavity under the impacts of inner rotating surface and inclined magnetic field during nanoliquid convection

In this study, thermal and phase change process in a circular porous vented cavity (P-VC) are numerically analyzed with finite element method considering magnetic field and inner surface rotation during nanofluid convection. The control of convective heat transfer and thermal management in porous cavities are crucial in applications for electronic cooling, heat exchangers, convective drying, and many other heat transfer devices. The numerical analysis is carried out for various values of the relevant parameters (Reynolds number—Re, rotational Reynolds number—Rew, Hartmann number—Ha, opening ratio—Ri) as follows: 500≤Re≤2000, −5000≤Rew≤5000, 0≤Ha≤80, 1≤Ri≤3. The phase change process often accelerates with higher Re when rotations are active. The rotations cause the full phase transition time (TR) to decrease by roughly 15% at the highest Re. The phase change process speeds up when both CW and CCW rotations are used at their highest values. The impacts of Ha on the TR variation is found as 33%. The thermal performances are slightly influenced by the variation of inner surface rotations and magnetic field strength. However, highest impact on thermal process and phase change is obtained when varying the inlet port size. The TR variation becomes 57% while heat transfer enhancement factor is obtained as 3.5. The optimal parameter combination to provide the highest thermal performance is (Ha, Rew, Ri) = (30.85, −4145, 2.98).

Ultrasensitive Fiber SPR Magnetic Field Sensor Using Au/TiO₂ Schottky Junction

This paper presents an ultrasensitive fiber surface plasmon resonance (SPR) magnetic field sensor using an Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Schottky junction coated on a plastic-clad multimode fiber (PMF) and immersed in the magnetic fluid (MF). The MF acts as the magnetic-sensitive material, and the Au/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film with a high dielectric constant excites SPR with high sensitivity. When the magnetic field strength applied to the MF changes, the MF’s refractive index alters accordingly, which changes the phase-matching condition of the surface plasmon polaritons, shifting the resonance dip in the fiber transmission spectrum. Therefore, the magnetic field strength can be measured by monitoring the resonance dip shift. The proposed sensor achieved a maximum magnetic sensitivity of -2.791 nm/Oe in the 5 to 35 Oe range, higher than most MF-based fiber magnetic field sensors. Additionally, the temperature response of the sensor was measured to be -0.4861 nm/°C, which has little effect on the magnetic sensing performance. The experimental results indicate that the proposed fiber SPR sensor can measure magnetic field strength variations with high sensitivity and accuracy, making it suitable for practical applications in various scenarios.

Analytical Model of Foreshock Ion Interaction With a Discontinuity: A Statistical Study

AbstractWhen a solar wind discontinuity interacts with foreshock ions, foreshock transients such as hot flow anomalies and foreshock bubbles can form. These create significant dynamic pressure perturbations disturbing the bow shock, magnetopause, and magnetosphere‐ionosphere system. However, presently these phenomena are not predictable. In the accompanying paper, we derived analytical equations of foreshock ion partial gyration around a discontinuity and the resultant current density. In this study, we utilize the derived current density strength to model the energy conversion from the foreshock ions, which drives the outward motion or expansion of the solar wind plasma away from the discontinuity. We show that the model expansion speeds match those from local hybrid simulations for varying foreshock ion parameters. Using MMS, we conduct a statistical study showing that the model expansion speeds are moderately correlated with the magnetic field strength variations and the dynamic pressure decreases around discontinuities with correlation coefficients larger than 0.5. We use conjunctions between ARTEMIS and MMS to show that the model expansion speeds are typically large for those already‐formed foreshock transients. Our results show that our model can be reasonably successful in predicting significant dynamic pressure disturbances caused by foreshock ion‐discontinuity interactions. We discuss ways to improve the model in the future.

Magnetoelastic primary resonance of an axially moving ferromagnetic plate in an air gap field

The air gap field widely exists in mechatronic systems to realize energy transfer, but the components in such systems are often regarded as rigid bodies. In this paper, elastomers in an air gap field are discussed for the first time. The magnetoelastic primary resonance of an axially moving ferromagnetic plate in an air gap field is investigated. With the magnetic wall armature as the electromagnetic source, the ferromagnetic thin plate moves axially parallel to the armature. An air gap field excited by the armature is distributed in thin air gap space between them. In addition to eddy current effects, the ferromagnetic thin plate in the air gap field will be magnetized to generate a harmonic magnetic force to excite the plate vibration, which results in the system existing nonlinear coupling characteristics between armature, plate deformation and air gap field. Considering the dynamic feedback of thin plate vibration on the air gap field by changing the air gap thickness, the magnetoelastic vibration equation of the plate is derived by the Hamilton's principle. The vibration differential equation for the simply supported plate is obtained via Galerkin method, and the static deflection of the plate under static magnetic load is solved. The multi-scale and Lyapunov methods are utilized to analyze the primary resonance under harmonic magnetic force, thus obtaining the steady-state resonance equation and the stability discriminants of stationary solutions. Through numerical simulations, the curves and three-dimensional surfaces of amplitude varying with different parameters are plotted. The variation of magnetic field strength, magnetic force, and electromagnetic torques under steady-state response is obtained. The results show that amplitude decreases with the increase of initial air gap thickness but increases with the increase of magnetic potential amplitude on the armature. Velocity has a suppression effect on system resonance, and there is an intrinsic coupling mechanism of action and reaction between the thin plate and air gap field.

Multi-spacecraft Observations of the Evolution of Interplanetary Coronal Mass Ejections between 0.3 and 2.2 au: Conjunctions with the Juno Spacecraft

We present a catalog of 35 interplanetary coronal mass ejections (ICMEs) observed by the Juno spacecraft and at least one other spacecraft during its cruise phase to Jupiter. We identify events observed by MESSENGER, Venus Express, Wind, and STEREO with magnetic features that can be matched unambiguously with those observed by Juno. A multi-spacecraft study of ICME properties between 0.3 and 2.2 au is conducted: we first investigate the global expansion by tracking the variation in magnetic field strength with increasing heliocentric distance of individual ICME events, finding significant variability in magnetic field relationships for individual events in comparison with statistical trends. With the availability of plasma data at 1 au, the local expansion at 1 au can be compared with global expansion rates between 1 au and Juno. Despite following expected trends, the local and global expansion rates are only weakly correlated. Finally, for those events with clearly identifiable magnetic flux ropes, we investigate the orientation of the flux rope axis as they propagate; we find that 64% of events displayed a decrease in inclination with increasing heliocentric distance, and 40% of events undergo a significant change in orientation as they propagate toward Juno. The multi-spacecraft catalog produced in this study provides a valuable link between ICME observations in the inner heliosphere and beyond 1 au, thereby improving our understanding of ICME evolution.

Расчет кривой Столетова конструкционных сталей по параметрам предельной петли магнитного гистерезиса

A formula has been developed for calculating the steel Stoletov curve (a graphic dependence of magnetic susceptibility χ on the magnetic field strength H in a ferromagnet) based on the results of measuring the coercive force Hc, technical saturation magnetization Ms and residual magnetization Mr. The derived formula is substantiated by a statistical analysis of a comparison between the calculation and experimental results obtained for grade SHX15 steel in its delivery and hardened states. The correlation coefficient between the calculated and measured values of χ in the entire variation range of H was 0.99, and the mean square deviation was 8.7%. By using the developed formula, it is possible to construct the dependence χ(H) and analyze it in different magnetic field strength variation ranges for any steel the measured values of Hc, Ms and Mr for which are given in the reference literature. The application of the formula is illustrated by analyzing the effect the tempering temperature of grade 30 steel after its quenching has on the steel Stoletov curves. The grade 30 steel tempering temperature has been established at which the required magnetic susceptibility value can be obtained in a given magnetic field strength variation range in a ferromagnet with its required hardness.

Interpretation of magnetic data using boundary analysis and inversion techniques: a case study from Gölcük/Isparta (Turkey) region

The Gölcük (Isparta) is on the southern side of the city of Isparta in the Mediterranean region of Turkey. The investigation of magnetic field strength variations over subterranean layers may reveal their locations on Earth?s surface and provide physical and geometrical characteristics. Magnetic studies were carried out around Gölcük caldera lake using proton magnetometers to identify subsurface volcanic structures. The acquired data were inverted using four different edge detection algorithms such as analytic signal, tilt angle, theta map, horizontal gradient. Afterwards, the results were used to determine the locations of the anomalous structures. We also used pseudo-gravity and reduction-to-pole techniques for interpretation. Additionally, the magnetic data were evaluated using the power spectrum technique and the results were compared with the 2D and 3D prismatic inversion outcomes. As a result, the boundaries and depth of the anomalous structures, such as the trachytic dome south of the Gölcük were determined for three different cross-sections and areas. The results show that the anomalous dome structures? average depth values vary between 225 m and 391 m in the region and the maximum depth of the Caldera reaches up to 1076 m.

Constraining evolution of magnetic field strength in the dissipation region of two BL Lac objects

With the assumption that the optical variability timescale is dominated by the cooling time of the synchrotron process for BL Lac objects, we estimate time dependent magnetic field strength of the emission region for two BL Lac objects. The average magnetic field strengths are consistent with those estimated from core shift measurement and spectral energy distribution modelling. Variation of magnetic field strength in the dissipation region is discovered. Variability of flux and magnetic field strength shows no clear correlation, which indicates the variation of magnetic field is not the dominant reason of the variability origin. The evolution of magnetic field strength can provide another approach to constrain the energy dissipation mechanism in jets.

The strength of the Earth’s magnetic field from Pre-Pottery to Pottery Neolithic, Jordan

Constraining secular variation of the Earth's magnetic field strength in the past is fundamental to understanding short-term processes of the geodynamo. Such records also constitute a powerful and independent dating tool for archaeological sites and geological formations. In this study, we present 11 robust archaeointensity results from Pre-Pottery to Pottery Neolithic Jordan that are based on both clay and flint (chert) artifacts. Two of these results constitute the oldest archaeointensity data for the entire Levant, ancient Egypt, Turkey, and Mesopotamia, extending the archaeomagnetic reference curve for the Holocene. Virtual Axial Dipole Moments (VADMs) show that the Earth's magnetic field in the Southern Levant was weak (about two-thirds the present field) at around 7600 BCE, recovering its strength to greater than the present field around 7000 BCE, and gradually weakening again around 5200 BCE. In addition, successful results obtained from burnt flint demonstrate the potential of this very common, and yet rarely used, material in archaeomagnetic research, in particular for prehistoric periods from the first use of fire to the invention of pottery.

Exact and Numerical Solution Using Lie Group Analysis for the Cylindrical Shock Waves in a Self-Gravitating Ideal Gas with Axial Magnetic Field

In this paper, we seek the exact and numerical solutions using Lie group analysis for one dimensional unsteady adiabatic flow in a self-gravitating ideal gas behind a cylindrical shock wave with axial magnetic field. With the help of Lie group analysis, the one-dimensional optimal system of sub-algebra is obtained for the system of equations of motion. With the help of optimal classes of infinitesimal generators, we constructed the similarity variable and transformation of the flow variables, which convert the system of partial differential equations into system of ordinary differential equations. In three particular cases, we have derived a general framework to solve the fundamental equations and exact feasible solutions are obtained. In two cases, the similarity solutions with exponential law and power law shock path are discussed. The similarity solution is obtained using numerical method in the case of power law shock path. It is obtained that the increase in the values of magnetic field strength and adiabatic index have the decaying effect on the shock wave. Also, increase in the strength of shock wave is witnessed with the rise in the gravitation parameter value. The effects of variation of magnetic field strength, adiabatic exponent and gravitational parameter on the flow variables are analyzed graphically.

Magnetogasdynamic shock wave propagation using the method of group invariance in rotating medium with the flux of monochromatic radiation and azimuthal magnetic field

Abstract The propagation of a cylindrical shock wave in rotating medium with azimuthal magnetic field under the action of monochromatic radiation using a method of group invariance is investigated. To derive similarity solutions as well as exact solutions, the group invariance technique is used. All classes of the solutions depending on the absorption coefficient are discussed by considering absorption coefficient to be variable or constant. A similarity solution is obtained, when the absorption coefficient is assumed to be variable. Two cases of solutions with a power law shock path are obtained by the different choices of arbitrary constants involving in the infinitesimal generators of the Lie group of transformations. To obtain the similarity solution in the case of the power law shock path, the density, magnetic field, axial and azimuthal velocity components are assumed to be varying and obeying power laws in the undisturbed medium. It is observed that with increase in the values of Alfven Mach number, adiabatic exponent and rotational parameter, shock strength decreases. The effects of variation of magnetic field strength, adiabatic exponent, rotational parameter and initial magnetic field variation index on the flow variables and on shock waves are analyzed graphically. Also, all classes of exact solutions are obtained by considering a constant absorption coefficient.

Micro-Structure Ring Fiber–Based Novel Magnetic Sensor with High Birefringence and High Sensitivity Response in Broad Waveband

The magnetic fluid sensor is proposed and numerically investigated by using finite-element-method (FEM) based on the photonic crystal fiber (PCF) with butterfly-shaped air holes and a ring core. Ethanol is used as a magnetic fluid that is injected in the ring core which provides unique characteristics. The goal of the proposed structure is to gain a better response to birefringence and relative sensitivity. In this work, the observed birefringence is $$1.27\times {10}^{-2}$$ ; the sensitivity responses are 40 nm/Oe, and 94047.13 nm/RIU can be gained for the variations of magnetic field strength from 50 to 200 Oe and 200 Oe, respectively. With best of knowledge, this sensitivity response is the highest response in the magnetic sensing. For better sensing performance the proposed butterfly structure can be used in the bio-optics field and nanofluidic technologies.

A Novel Class of 1 H-MRI Contrast Agents Based on the Relaxation Enhancement Induced on Water Protons by 14 N-Containing Imidazole Moieties.

This study reports the development of a completely new class of MRI contrast agents, displaying remarkable relaxation effects in the absence of paramagnetic metal ions. Their detection requires the acquisition of images at variable magnetic field strength as provided by fast field cycling imaging scanners. They contain poly-histidine chains (poly-His), whose imidazole groups generate 14 N-quadrupolar-peaks that cause a relaxation enhancement of water protons at a frequency (1.38±0.3 MHz) that is readily detectable from the frequencies associated with endogenous proteins. The poly-His quadrupolar peaks are detectable only when the polymer is in a solid-like form, that is, at pH>6.6. Above this value, their intensity is pH dependent and can be used to report on the occurring pH changes. On this basis, the poly-His moieties were conjugated to biocompatible polymers, such as polylactic and glycolic acid, in order to form stable nanoparticles able to encapsulate structured water in their core. FFC images were acquired to assess their contrast-generating ability.

A Novel Class of 1H‐MRI Contrast Agents Based on the Relaxation Enhancement Induced on Water Protons by 14N‐Containing Imidazole Moieties

AbstractThis study reports the development of a completely new class of MRI contrast agents, displaying remarkable relaxation effects in the absence of paramagnetic metal ions. Their detection requires the acquisition of images at variable magnetic field strength as provided by fast field cycling imaging scanners. They contain poly‐histidine chains (poly‐His), whose imidazole groups generate 14N‐quadrupolar‐peaks that cause a relaxation enhancement of water protons at a frequency (1.38±0.3 MHz) that is readily detectable from the frequencies associated with endogenous proteins. The poly‐His quadrupolar peaks are detectable only when the polymer is in a solid‐like form, that is, at pH&gt;6.6. Above this value, their intensity is pH dependent and can be used to report on the occurring pH changes. On this basis, the poly‐His moieties were conjugated to biocompatible polymers, such as polylactic and glycolic acid, in order to form stable nanoparticles able to encapsulate structured water in their core. FFC images were acquired to assess their contrast‐generating ability.

Modeling of hysteresis loops using rational and power functions

Simple and precise hysteresis models with a small number of parameters allowing fast calculation are required for the magnetic analysis, as the field is calculated in a very large number of points. This paper presents a new simple method for modeling the hysteresis loops of soft magnetic materials using combined rational and power functions. Three approaches are used to model the hysteresis loops analytically. In the first approach, the upper and lower curves of the hysteresis loops are estimated and are calculated separately, using combined rational and power functions. In the second approach, the hysteresis loops are calculated using the DC magnetization curve and combined rational and power functions, applying a phase shift in the magnetic field strength variations relative to the magnetic flux density. The third approach presents a novel method for modeling hysteresis loops: first, the model is fitted to the “mean curve”, which is in the middle of the measured hysteresis curve, and as a second step the phase shift is calculated as in the second approach. A solid iron sample with a rectangular cross section is used for the measurements and the hysteresis modeling. The proposed method is also applied to model the hysteresis loops of a magnetic material with high magnetic permeability and grain-oriented steel, to show the generality of the proposed methods.

Effect of TMF and AMF Components on Expansion Process in Different Ignition Modes of Vacuum Arc Between Spiral-Type TMF Contacts

The drawn vacuum arc begins with a bridge column formed from the explosion of a liquid metal bridge after separating the contacts. The expansion process of the initial arc has an effect on arc motion or diffusion. In order to deeply study the influence of transverse magnetic field (TMF) and axial magnetic field (AMF) on the drawn arc characteristics in the initial expansion stage, in this article, arc ignition mode and appearance under two groups of contacts with different AMF and TMF components were experimentally studied. It was found that simultaneously reducing TMF and AMF components would end the expansion stage earlier, and the fluctuation of the arc column pressure during the expansion was larger. When TMF and AMF components were further reduced, the arc needs to take a longer time to extend across the slot gap due to insufficient Ampere force. When TMF was basically unchanged and AMF was reduced, the arc burned more intense, the diameter of the arc column was smaller, and the arc would merge earlier in multipoint ignition mode. The characteristics of arc voltage, pressure, and duration of expansion stage were analyzed, founding that the arc with a moderate TMF and AMF components had a smaller rising slope of arc voltage, a faster reducing speed of arc pressure, and a smaller range of the duration of expansion stage. In addition, the variation of magnetic field strength in different ignition modes and contact structures during the arc expansion stage was simulated to explain the mechanism of arc behavior.