Magnetic Drag Research Articles

Comparative Planetology of Magnetic Effects in Ultrahot Jupiters: Trends in High-resolution Spectroscopy

Ultrahot Jupiters (UHJs), being the hottest class of exoplanets known, provide a unique laboratory for testing atmospheric interactions with internal planetary magnetic fields at a large range of temperatures. Thermal ionization of atmospheric species on the dayside of these planets results in charged particles becoming embedded in the planet’s mostly neutral wind. The charges will resist flow across magnetic field lines as they are dragged around the planet and ultimately alter the circulation pattern of the atmosphere. We model this process to study this effect on high-resolution emission and transmission spectra in order to identify observational signatures of the magnetic circulation regime that exist across multiple UHJs. Using a state-of-the-art kinematic MHD/active drag approach in a 3D atmospheric model, we simulate three different UHJs with and without magnetic effects. We postprocess these models to generate high-resolution emission and transmission spectra and explore trends in the net Doppler shift as a function of phase. In emission spectra, we find that the net Doppler shift before and after secondary eclipse can be influenced by the presence of magnetic drag and the wavelength choice. Trends in transmission spectra show our active drag models consistently produce a unique shape in their Doppler shift trends that differs from the models without active drag. This work is a critical theoretical step to understanding how magnetic fields shape the atmospheres of UHJs and provides some of the first predictions in high-resolution spectroscopy for observing these effects.

Up, Up, and Away: Winds and Dynamical Structure as a Function of Altitude in the Ultrahot Jupiter WASP-76b

Due to the unprecedented signal strengths offered by the newest high-resolution spectrographs on 10 m class telescopes, exploring the 3D nature of exoplanets is possible with an unprecedented level of precision. In this paper, we present a new technique to probe the vertical structure of exoplanetary winds and dynamics using ensembles of planet absorption lines of varying opacity, and apply it to the well-studied ultrahot Jupiter WASP-76b. We then compare these results to state-of-the-art global circulation models (GCMs) with varying magnetic drag prescriptions. We find that the known asymmetric velocity shift in Fe i absorption during transit persists at all altitudes, and observe tentative trends for stronger blueshifts and more narrow line profiles deeper in the atmosphere. By comparing three different model prescriptions (a hydrodynamical model with no drag, a magnetic drag model, and a uniform drag model) we are able to rule out the uniform drag model due to inconsistencies with observed trends in the data. We find that the magnetic model is slightly favored over the the hydrodynamic model, and note that this 3-Gauss kinematic magnetohydrodynamical GCM is also favored when compared to low-resolution data. Future generation high-resolution spectrographs on extremely large telescopes will greatly increase signals and make methods like these possible with higher precision and for a wider range of objects.

In-capillary magnetic separation and enrichment coupled with laser-induced fluorescence for rapid determination of biomolecules

Biomolecules are indispensable in the life activities and metabolism of various organisms, and their highly sensitive detection is of great significance for disease diagnosis and food safety. Due to the complexity of the matrix and the low concentration of the target, separation and enrichment of biomolecules prior to detection are necessary and time-consuming. Herein, a novel approach combining in-capillary magnetic separation and enrichment with laser-induced fluorescence detection method was proposed for qualitative and quantitative analysis of biomolecules. Two different sequence aptamers modified with magnetic nanoparticles and labeled with fluorescence were used as capture probes and signal probes to form sandwich structures with target molecules for detection. Under the combined influence of magnetic field force and fluid drag force, the integration of separation, enrichment and on-line detection were finished within 5min. Under optimal conditions, the developed method provided a low limit of detection as 2.7 fmol/L, 0.57 nmol/L, 3 CFU/mL for DNA, thrombin and Staphylococcus aureus, respectively. This proposed method offers a promising platform for the sensitive and rapid determination of biomolecules. It holds significant potential for future applications in fields of environmental and biochemical analysis.

하이퍼루프 초전도 전자석과 진공튜브 연결부 사이에 발생하는 자기 저항력 특성 연구

하이퍼루프 초전도 전자석과 진공튜브 연결부 사이에 발생하는 자기 저항력 특성 연구

Influence of exchange bias on spin torque ferromagnetic resonance for quantification of spin–orbit torque efficiency

Antiferromagnet (AFM)/ferromagnet (FM) heterostructure is a popular system for studying the spin–orbit torque (SOT) of AFMs. However, the interfacial exchange bias field induces that the magnetization in FM layer is noncollinear to the external magnetic field, namely the magnetic moment drag effect, which further influences the characteristic of SOT efficiency. In this work, we study the SOT efficiencies of IrMn/NiFe bilayers with strong interfacial exchange bias by using spin-torque ferromagnetic resonance (ST-FMR) method. A full analysis on the AFM/FM systems with exchange bias is performed, and the angular dependence of magnetization on external magnetic field is determined through the minimum rule of free energy. The ST-FMR results can be well fitted by this model. We obtained the relative accurate SOT efficiency ξ DL = 0.058 for the IrMn film. This work provides a useful method to analyze the angular dependence of ST-FMR results and facilitates the accurate measurement of SOT efficiency for the AFM/FM heterostructures with strong exchange bias.

Analyzing the Effect of Magnetic Drag Force on Carbon Nanotubes Suspended in Casson Fluid Within Parallel Surfaces with Heat Diffusion and Rate of Molar Reaction: An Analytical Approach

The study of hydromagnetic CNTs of Casson fluids in Poiseuille flow has significant implications for various industries and can provide valuable insights into the fundamental properties, such as viscosity and conductivity of these fluids. They can improve the heat transfer properties of fluids and enhance the overall efficiency of thermal systems and the presence of CNTs can induce a magnetic field in the fluid. The main goal of using carbon nanotubes (CNTs) in Poiseuille flow is to enhance the fluid flow properties, such as viscosity, thermal conductivity, and heat transfer and the novelty of CNTs in Poiseuille flow lies in their ability to modify the fluid flow properties by altering the structure of the fluid at the nanoscale level. The use of CNTs in Poiseuille flow has gained attention due to their unique mechanical, electrical, and thermal properties. An analytical approach to the investigation of heat transmission in hydro-magnetic forces of natural convective flow of Casson-fluid in a Poiseuille flow implanted by Darcian regime on Carbon Nanotubes with the impacts of magnetic field, heat generation, diffusion thermo, porosity, radiation and first order chemical reaction is presented. In this research, dual solutions are introduced for single-wall and multiple-wall carbon nanotubes over velocity and temperature of nanofluid by the application of various physical and they are elaborated via plane curves. The base fluid is considered for the CNTs as Engine oil. Validity of this model has established by comparing with the available previous literature and is found acceptable agreement with it. In the present study, it is found that the fluctuation in radiation and heat generation plays a significant role in CNTs. It is known that a rise in the Casson parameter and nanoparticle volume fraction enhances the fluid velocity. It is concluded that, the volume fraction of nanoparticles in Poiseuille flow can have a significant impact on the flow behaviour and properties of the fluid. This study has tremendous feasible applications in the areas related to biomedical sciences, water purification process, technology of fibers, nano-materials technology, storage of energy and various applications.

Insight into acoustic wave-driven gas bubble dynamics in Williamson's fluid

This study's motivation on the behavior of a gas bubble and surrounding fluid during the collapse phase of an acoustic wave leads to the emission of light, which can be modelled using the Rayleigh-Plesset equation. The significant contribution to the major addition to the understanding of gas bubble dynamics in viscoelastic fluids. The results of the study have the potential to impact a wide range of applications, from sonar and underwater acoustic propagation to biomedical applications and industrial operations. Understanding the dynamics of acoustic wave-driven gas bubble oscillations in non-Newtonian fluids is crucial for various applications in medical imaging, therapy, and microfluidics. The aim of this study is to discover the conditions under which these bubbles can undergo sonoluminescence, the emission of light due to the collapse of bubbles under severe sonic pressure. The complex ordinary differential equation is solved numerically, and graphs are generated to evaluates various parameters such as velocity, radius, and pressure. A comparison with the viscous case is also presented to assess the influence of Newtonian and non-Newtonian fluids. A program designed by Mathematica software (13.0) “parametric NDSolve package” is used to solve the equations. The numerical solution supports the boundary conditions, indicating stability and reliability. Notably, the study identifies distinct fluctuations in the phase and stable characteristics associated with non-Newtonian effects. Interestingly, certain fluid parameters lead to discrete group modulation of radial excursions, revealing a novel and previously unknown phenomenon. It is concluded that Higher Reynolds numbers result in turbulent flow, which causes the bubble to enlarge and increase its volume. Furthermore the pressure gradient is affected by magnetic drag force, and as size of bubble increases, required pressure gradient to counteract the drag force also increases. As the magnetic field intensity increases, the velocity of the bubble decreases. Also, considering the implications of these results, the study explores their relevance to medical ultrasonography applications.

Improved Analytical Model for the Magnetic Drag of a Dual-Conductor Plate Parallel Electric Suspension and Guiding Mechanism

The Maglev launch assist system (MLAS) has been adopted as part of a reusable launch vehicle system to lower launch costs. In this paper, a dual-conductor plate parallel electric suspension and guiding mechanism (DPESGM) serving the suspension and guidance function of the MLAS is proposed. First, the MLAS and the structure of the DPESGM are introduced. Then, a DPESGM magnetic drag analysis model is established based on the multilayer theory for the fast calculation of the magnetic drag. However, its accuracy is poor at high speed. To solve this problem, an improved analytical model suitable for the full speed range is developed, which takes the equivalent conductivity replacement approach to consider the skin effect. Finally, the improved analysis model is verified by the finite element method (FEM) and prototype experiments. The results show that the improved analytical model is highly accurate in the evaluation of the DPESGM magnetic drag from low speed to high speed. As the improved analytical model takes less computational time than 3D FEM, it is an efficient tool for the DPESGM magnetic drag calculations to complete the preliminary design of the propulsion and braking systems.

Magnetohydrodynamical Torsional Oscillations from Thermoresistive Instability in Hot Jupiters

Hot Jupiter atmospheres may be subject to a thermoresistive instability where an increase in the electrical conductivity due to ohmic heating results in runaway of the atmospheric temperature. We introduce a simplified one-dimensional model of the equatorial substellar region of a hot Jupiter that includes the temperature dependence and time dependence of the electrical conductivity, as well as the dynamical back-reaction of the magnetic field on the flow. This model extends our previous one-zone model to include the radial structure of the atmosphere. Spatial gradients of electrical conductivity strongly modify the radial profile of Alfvénic oscillations, leading to steepening and downward transport of magnetic field, enhancing dissipation at depth. We find unstable solutions that lead to self-sustained oscillations for equilibrium temperatures in the range T eq ≈ 1000–1200 K and radial magnetic field strength in the range ≈10–100 G. For a given set of parameters, self-sustained oscillations occur in a narrow range of equilibrium temperatures that allow the magnetic Reynolds number to alternate between large and small values during an oscillation cycle. With our simplified geometry, outside of this temperature window the system reaches a steady state in which the effect of the magnetic field can be approximated as a magnetic drag term. Our results show that thermoresistive instability is a possible source of variability in magnetized hot Jupiters at colder temperatures and emphasize the importance of including the temperature dependence of electrical conductivity in models of atmospheric dynamics.

Conversion of Heat into Electricity Through Natural Convection of a Single-Phase Liquid Metal in a Closed Loop with a Magnetic Field

Conventional waste heat recovery systems usually require water (e.g. to supply steam for a turbine) and imply the wearing of moving parts, to the detriment of usability in case of drought and/or in the long term. Unconventional approaches (thermoacoustic and thermoelectric conversion of heat into electricity) overcome these obstacles, but their utilization for multi Kilowatt (KW) electric power in an industrial environment is jeopardized either by large working pressure, excessive noise, the need for cooling systems or huge magnetic fields. Welander and Erhard et al. discuss the existence and the stability of steady-state convection driven by an applied temperature gradient of a fluid circulating in a tube that forms a vertical, closed loop. Convection ensures the spontaneous conversion of heat into mechanical energy through competing buoyancy, drag and heat conduction between the fluid and the walls of the tube. Crucially, their results do not depend on the nature of the drag. If the working is an electrical conductor and a magnetic field is applied, the impact of the resulting Lorenz force acts as a drag on the motion of the fluid just like viscosity; the viscous and the magnetic drag are dealt with on an equal basis. The magnetic drag transforms the mechanical energy of the convective motion of the fluid into electric energy. Since convection is driven by a temperature gradient, spontaneous, water-free conversion of heat into electricity occurs with no moving part at atmospheric pressure. Such conversion is suitable for the purposes of waste heat recovery. As an example, let a 1-cm-radius tube filled GalinstanTM (a commercially available, atoxic liquid metal alloy) be rolled up in a double helix wrapped around a 30-m-tall, 3-m-radius chimney located above a furnace. If there is a 350 K temperature difference between the bottom of the tube (near the furnace) and the top, and if permanent magnets located on the tube provide a 0.017 T magnetic field, then conservative estimates show that we obtain 2 KW DC electric power with efficiency > 2.1%. This lower bound suggests that our system is competitive with thermoacoustic and thermoelectric conversion.

Influence of Magnetic and Rheological Properties on a Leakage Channel in a Fluid Ring in Ferrofluid Seal

A ferrofluid ring can be compared to a liquid O-ring seal. This liquid ring is used in various applications, such as seals, valves, compressors, dampers, or thrust bearings. Its main advantage is that it maintains tightness and is held in a given place by a magnetic field. One of the main problems is the occurrence of leakage due to pressure differences. This affects the volume of liquid ejected outside the ferrofluid ring region and the value of the leakage itself. The research area of this publication is related to the recognition of how magnetic and rheological properties influence the mechanism of leakage channel formation in a single fluid ring. The purpose was to research basic parameters that characterize the leakage channel, such as the pressure jump value, the cross-sectional area, airflow, and leakage value. The results allow us to understand this problem better and provide insight into the behavior of magnetic particles in a colloid. Studies have shown that an increase in the number of magnetic nanoparticles increases the cross-sectional area of the leakage channel. The opposite effect is observed when a viscosity increase affects fluid resistance to deformation. The study also shows that the share of large particles does not significantly influence the leakage channel. However, the magnetic particles viscous drag affects the ability of particles to react to change.

Numerical modeling of bioconvection and heat transfer analysis of Prandtl nanofluid in an inclined stretching sheet: A finite difference scheme

The addition of nanoparticles in the base fluid increases the thermal conductivity of the fluid but the stability of the fluid gets affected due to the presence of nanoparticles in the base fluid. The addition of motile microorganisms in the nanofluid increases the stability of the nanofluid by enhancing thermal conductivity as well as mass transport. In this perspective, the current investigation deals with the study of the behavior of microorganisms in bioconvection over the fluid variables in the non-Darcy background. A two-dimensional Prandtl-nanofluid moving along an inclined stretching flat surface subject to inlet and outlet rate of flow to the surface under the action magnetic drag force normal to the surface. The non-linear partial differential equations are transmuted to ODEs through appropriate similarity transformations. The MATLAB inbuilt bvp4c solver has been employed to generate the solution of the transformed ODEs. The stability of the finite difference scheme is demonstrated by a stability test, and the influence of various parameters on the nanofluid velocity, thermal as well as concentration, and density of motile microorganisms is depicted using graphs for each of them. Additionally, interested physical quantities, shearing stresses, rate of thermal diffusion, rate of mass diffusion, and rate of motile microorganism at the surface, have been plotted by varying the controlling parameters. Growth in the shear stress as well as the rate of thermal diffusion has been detected for the increasing values of and However, the Sherwood number decays for augmented values of The findings could be utilized to increase the thermal efficiency of heat exchangers in order to maintain thermal balance management in small heat-density equipment and gadgets, as well as the thermal efficiency of microbial fuel cells, enzyme biosensors, and microfluidics devices.

Theory and experiment for a solenoid based currents and the magnetic drag

In this study, we derived formulas for the current waveforms induced by a magnet oscillating at arbitrary positions on the axis of a solenoid. We also conducted an experiment for measuring the currents induced in a solenoid by a magnet oscillating in its inner or outer region and compared the results with theoretical predictions. It was confirmed that the magnitude and shape of waveforms of induced currents that were obtained from the derived formulas fit well with experimental results. In addition, the magnetic drag force exerted on the magnet by the induced current is formulated and compared with the prediction estimated by the attenuation coefficient and velocity.

Plasma acceleration in a magnetic arch

When two magnetic nozzles with opposite polarity are placed side by side, a ‘magnetic arch’ (MA) is formed, which connects the field lines of each nozzle into a closed-line configuration. The plasma expansion and acceleration in this magnetic topology are relevant for clusters of electrodeless plasma thrusters, as well as novel, non-cylindrical thruster architectures. A collisionless, quasineutral, two-fluid model of the plasma expansion in a MA, is introduced. The plasma properties (density, electron temperature, electrostatic potential, ion velocity, electric currents) in the 2D planar and zero plasma-beta limit are analyzed, and the magnetic thrust density is discussed. It is shown that the ions coming out of the two nozzles meet on a shock-like structure to form a single beam that propagates beyond the closed lines of the applied magnetic field, generating magnetic thrust. A small magnetic drag contribution comes from the final part of the expansion. The plasma-induced magnetic field is then computed self-consistently for non-zero plasma-beta expansions, showing that it stretches the MA in the downstream direction and helps reduce that drag contribution. Finally, the limitations of the present model are discussed.

Numerical simulation of melting heat transfer in cylindrical slip flow of complex nanofluid

The heat diffusion in the cylindrical film stream of the second-grade cross nanofluid is examined numerically. In this study, solid nanoparticles of the aluminum alloys AA7072 and AA7075 are submerged in water as the base liquid. A consistent magnetic field is effective to the stream along with the nonlinear radiation, Ohmic heating, and Catteneo–Christov heat flux to inspect base fluid and composite nanofluids’ stream and thermal transport properties. The flow model is created and solved mathematically utilizing the bvp5c MATLAB scheme. Comparable outcomes for water and composite nanofluids have been delivered and explored. The present research focuses on using solar energy with parabolic trough solar collectors (PTSC). It is discovered that the thermal diffusion rate of the AA7072-AA7075-water combination is more remarkable than the base liquid. The external magnetic field's drag force can be used to moderate the flow and thermal areas. Also, radiative heat contributes to boosting the thermal transport rate of composite nanofluid without impacting the wall resistance. Therefore, AA7072-AA7075-water pumping through PTSC will help to improve heat diffusion to a higher level. The findings are original and aid in understanding how well hybrid nanomaterials function in a second-grade non-Newtonian liquid. The information from this study about the elements that contribute to the working fluid's thermal improvement is also helpful to researchers in this field and a broad audience from industries.

Influence mechanism of magnetic field direction on magnetic drag of reentry vehicle and better magnetic field direction

The magnetic field condition has a great influence on the magnetic control drag of reentry vehicle, so it is an important research topic to select appropriate magnetic field condition to control the drag force of vehicle. This paper analyzes the magnetic control drag by solving the hypersonic magnetohydrodynamic equations and combining the magnetic field working conditions, studies the influence of the axisymmetric magnetic field direction on the drag, supplements the mechanism of Lorentz force, pressure and conductivity on the axisymmetric magnetic control drag, and compares the drag value and drag composition ratio under different magnetic field directions. The problem is solved numerically for a particular model of a dipole magnetic field. Under different dipole magnetic fields, the magnitude and distribution shape of Lorentz force are different. There are several dividing lines where the Lorentz force is 0, and the Lorentz force directions on both sides are opposite, and this line divides the Lorentz force field into multiple parts. In addition, it is found that the change of the angle between the axis of the aircraft and the direction of the magnetic field will cause the change of the aircraft resistance, which will reduce or increase it.

Impact of Inclined Magnetic Force on Bio-Fluid in Permeable Bifurcated Arteries: Analytical Approach

The present article aims at presenting analytical solutions of the effects of chemical reaction and inclined magnetic force on blood flow through bifurcated arteries placed in a porous medium in association with heat source. The equations of the blood flow model are solved analytically by means of infinite series solution of convergent scheme with appropriate initial and boundary conditions. The important characteristics of the electromagnetohydrodynamic flow of bio-fluid through bifurcated arteries are distinctly highlighted by virtue of the dual solutions that are obtained for Axial velocity, Normal velocity, fluid Temperature, molar species, Skin-friction, Nusselt Number and Sherwood Number. The behaviour of the biofluid variables with individual parameters like Prandtl Number (Pr), Magnetic drag force (Md), Porosity (Kp), Heat source (Hs), Schmidt Number (Sc), Thermal Radiation (R), Chemical reaction rate (Cr), decay (ξ) are discussed in detail through graphs using MATLAB Software. Validation of this work is presented and found suitable. It is disclosed that the flow of bio-fluid is noticeably influenced by the adequate strength of externally applied inclined magnetic force and porosity. This study is essentially important in simple flow, peristaltic flow, pulsatile flow and drug delivery.

The Investigation of Vortex Motion in the YBCO Devices Manufactured Utilizing a Gaussian-shaped Optical Spot from a Continuous-wave Laser

The current report focuses on the analysis of the investigation results of the Abrikosov vortex motion in the YBa2Cu3O7-d (YBCO) device, which is a c-axis textured 0.3 ´ 50 ´ 100 µm3 (thickness ´ width ´ length) stripe of YBCO superconductor deposited on a LaAlO3 substrate. A laser beam focused in a Gaussian-shape optical spot of 5 mm in diameter modifies the stripe, initiating the oxygen out-diffusion and its uneven distribution in illuminated areas and in this way causing the appearance of a higher level of deoxygenation in the spot center and a lower level at its edges (slopes of weak superconductivity region). At temperatures below the temperature of the superconducting transition Tc, the current-self-produced magnetic field penetrates the optically modified area of the stripe in a form of Abrikosov magnetic vortices, and due to the current-self-produced Lorentz force, the vortices move toward their annihilation line resulting in energy dissipation. The vortices pinned on the slopes experience strong pinning and exert a magnetic drag force on moving vortices, which is confirmed by the stepped current-voltage dependences of the YBCO devices measured at temperatures 0.933·Tc £ T £ 0.958·Tc. Our results demonstrate the advantages of partially deoxygenated YBCO material for the development of superconducting electronic devices with electronic properties controlled by the motion of Abrikosov vortices at temperatures below Tc of the superconductor.

Emergent Spectral Fluxes of Hot Jupiters: An Abrupt Rise in Dayside Brightness Temperature Under Strong Irradiation

We study the emergent spectral fluxes of transiting hot Jupiters, using secondary eclipses from Spitzer. To achieve a large and uniform sample, we have reanalyzed all secondary eclipses for all hot Jupiters observed by Spitzer at 3.6 and/or 4.5 μm. Our sample comprises 457 eclipses of 122 planets, including eclipses of 13 planets not previously published. We use these eclipse depths to calculate the spectral fluxes emergent from the exoplanetary atmospheres, and thereby infer the temperatures and spectral properties of hot Jupiters. We find that an abrupt rise in brightness temperature, similar to a phase change, occurs on the dayside atmospheres of the population at an equilibrium temperature between 1714 and 1818 K (99% confidence limits). The amplitude of the rise is 291 ± 49 K, and two viable causes are the onset of magnetic drag that inhibits longitudinal heat redistribution, and/or the rapid dissipation of dayside clouds. We also study hot Jupiter spectral properties with respect to metallicity and temperature inversions. Models exhibiting 4.5 μm emission from temperature inversions reproduce our fluxes statistically for the hottest planets, but the transition to emission is gradual, not abrupt. The Spitzer fluxes are sensitive to metallicity for planets cooler than ∼1200 K, and most of the hot Jupiter population falls between model tracks having solar to 30× solar metallicity.

Numerical simulation on Cu–H2O nanofluid of destructive and generative reactions in a Darcian medium: application of wall suction and blowing

Application of – nanoparticles in a base fluid of water means the growth of thermal conductivity of Nanofluid. This physical behavior recommends the prospect of applying nanofluids in electronic cooling and advanced nuclear systems. The formulated leading equations are transformed to non-dimensional form by appropriate similarity transformations and finally solved numerically through Runge–Kutta Shooting method of 4th order. The novelty of the current investigation is to examine the impact of wall suction/ injection over the dual solutions by numerical simulation for time-independent, two- dimensional nanofluid flow along a semi-infinite porous stretching horizontal wall placed in a Darcian medium under the application of magnetic drag force. The significant outputs are portrayed in dual solutions for suction/injection and deliberated their salient effects of various emerging physical variables on velocity, temperature, and molar concentration of Copper nanoparticles in water base fluid. It is obtained that the nanoparticle concentration grows via larger destructive chemical reaction and lessens when generative chemical reaction is enhanced. This investigation leads to opposite behavior due to endothermic reaction. The significance of such investigation in Darcian porous medium have frequent applications in the major area of industrial and engineering technologies that covers the bio-engineering, rubber technology and material processing.