Different Values Of Magnetic Field Research Articles

Numerical experiments on granulation-generated two-fluid waves and flows in a solar magnetic carpet

ABSTRACT We consider the effects of granulation with a complex geometry of a magnetic carpet on the genesis of waves and plasma flows in a quiet-region of the solar atmosphere. Our aim is to perform numerical experiments on the self-generated and self-evolving solar granulation in a magnetic carpet representing the parts of the large-scale magnetized solar atmosphere, where waves and flows are basic inherent physical processes occurring continuously. We perform numerical experiments with the use of the joanna code which solves non-ideal and non-adiabatic two-fluid equations for ions + electrons and neutrals treated as two separate fluids. In these experiments, we assume that the plasma is hydrogen, and initially described by magnetohydrostatic equilibrium which is accompanied with a magnetic carpet. Parametric studies with different values of magnetic field show that its higher values result in larger magnitudes of ion-neutral velocity drift, thus ensuring larger heating and plasma flows. The present model addresses that in the highly dynamic solar chromosphere, waves, heating and plasma flows may collectively couple different layers of the solar atmosphere, and this entire process crucially depends on the local plasma and magnetic field properties. We suggest that waves and flows are the natural response of the granulation process in the quiet-Sun.

Study of heavy quarkonia in the presence of magnetic field by Nikiforov Uvarov method

The N-dimensional radial Schrödinger equation has been solved using the Nikiforov Uvarov (NU) method, in which we used the medium modified form of Cornell potential and quasi-particle Debye mass with strong magnetic field background. The binding energies and the mass spectra of heavy quarkonium have been studied in the N-dimensional space for different values of magnetic field, the binding energy decreases with increasing magnetic field, which shows early dissociation of heavy quarkonium system. The influence of dimensionality number has also been discussed on binding energies of [Formula: see text] and [Formula: see text] for fixed value of magnetic field. It is found that with an increase in dimensionality, the binding energy starts decreasing from a higher initial value. The results obtained are quite consistent with recent studies.

Numerical modeling of magnetohydrodynamic non‐Newtonian flow in a cross‐slot

AbstractThis study numerically investigates the characteristics of a non‐Newtonian magnetohydrodynamic flow in a cross‐slot. Numerical simulations are performed using power law, Bird–Carreau and Casson non‐Newtonian fluid models. The flow characteristics and shear viscosity behavior in the flow region are analyzed for different values of magnetic field. Additionally, the dynamic behavior of the bifurcated flow in the cross‐slot is studied in detail, and the computational results are compared with existing models. It is shown that the fluid velocity is reduced in both the inlet and outlet channels of the cross‐slot due to the magnetic field, regardless of the viscosity model. Moreover, it is found that the fluid viscosity increases along the centerline of the inlet channels and decreases in the outlet channels of the cross‐slot for all non‐Newtonian fluid models tested here. Furthermore, this study shows that the flow properties of the non‐Newtonian fluids can be controlled by changing the magnetic field strength. The results of this study will be useful for analyzing the flow behavior of blood in a microfluidic cross‐slot and other rheological fluids used in biochemical engineering and industrial processes, where higher mass transfer and mixing efficiency can be achieved by imposing an external magnetic field.Highlights Simulation of non‐Newtonian magnetohydrodynamic flow in a cross‐slot is conducted. Analysis of the flow and shear viscosity behavior for different Hartman number is performed. Flow properties were successfully controlled with the imposed external magnetic field.

Coupled influences of magnetic field and several thermal loads on vibration of thermoelastic nano-ceramic (Si3N4) beam

Our study investigates the vibration of a thermoelastic nano-ceramic (Si3N4) beam exposed to a magnetic field under the effect of a moving heat source and different types of thermal loads. These nanobeams are modeled as non-Fourier heat conduction. In our formulation, the equation of motion and the principle of energy conservation from two coupled partial differential equations have been driven. A direct approach has been used to find the solutions to the governing equations using the Laplace transform definition. Numerical Laplace transform inversion was calculated using Hoing's approximation approach. Solutions have been applied to silicon nitride (Si3N4) nanobeam ceramics. Figures show the distribution of temperature increment, lateral deflection, and stress with different values of magnetic field and several thermal load parameters. In all the studied nanobeam functions, the magnetic field and several thermal loads’s parameters have significant effects. They could be used as tuners to control the vibration and temperature increment. In the present study, a moving heat source, and different thermal loads have been applied to a non-Fourier nanobeam exposed to a magnetic field. The results have been compared with those obtained in the thermoelastic cases.

Spin-orbit interaction effect on a hydrogenic [formula omitted] centre in a three-dimensional asymmetric Gaussian GaAs quantum dot in a magnetic field

The binding energy of a hydrogenic neutral D0 complex situated in a three-dimensional asymmetric Gaussian GaAs quantum dot is studied incorporating the Rashba and Dresselhaus spin-orbit interactions and the effect of an external magnetic field by means of a variational method and its variation with respect to the quantum dot size, strength of the magnetic field, donor position and spin-orbit coupling strengths is calculated. The behavior of the magnetic susceptibility of the system is also investigated with respect to the magnetic field for different values of the quantum dot parameters.

MHD Modeling of Mass Transfer Processes in Close Binary Stars

A three-dimensional numerical model has been developed to study the flow structure in close binary systems with a magnetic field. The model uses a system of equations of modified magnetic hydrodynamics, which allows describing all the main dynamic effects associated with the magnetic field. It takes into account the processes of radiation heating and cooling, heating due to current dissipation, as well as magnetic field diffusion. The model allows calculations in a wide range of magnetic field values. Comparison of the calculation results with observational data confirms the reliability and high efficiency of the model. The paper presents the calculation results of the flow structure in a typical intermediate polar. It is shown that an accretion disk is formed in such a binary system, which has the following characteristic features: “hot line”, tidal shock waves, precession density wave, magnetospheric region, and accretion columns. In this case, the magnetic field in the disk is predominantly toroidal. The paper also presents the results of calculations for typical polars. In such systems, instead of an accretion disk, a collimated stream of matter is formed, moving along the magnetic field lines to the magnetic poles of the white dwarf. It is shown that in synchronous polars, variations of the mass transfer rate lead to a change in the spatial configuration of the flow. In asynchronous polars, changes in the flow structure for different phases of the beat period are observed as well as the processes of switching the flow between the magnetic poles of the accretor. Numerical calculations of the asynchronous system are performed under the assumption of the dipole configuration of the magnetic field for different values of the dipole offset relative to the center of the white dwarf. The paper presents a method for estimating this offset from observational light curves.

Magnetic properties of spinels Co x Zn1−x Cr2O4 systems: Green’s functions, high-temperature series expansions technique and mean-field theory

ABSTRACT Many-body Green’s function and mean-field theories have been developed for magnetic systems Co x Zn1−x Cr2O4. We apply these theories to evaluate the thermal magnetization and magnetic susceptibility for different values of magnetic field and dilution x, by considering all components of the magnetization when an external magnetic field is applied in (x-z) plane. The critical temperature of Co x Zn1−x Cr2O4 spinels have been calculated in the range 0 ≤ x ≤ 1. The Green’s function results are compared with the results of high-temperature series expansion technique and experimental magnetic measurements.

The effect of disorder on local electron temperature in quantum Hall systems

The local electron temperature distribution is calculated considering a two dimensional electron system in the integer quantum Hall regime in presence of disorder and uniform perpendicular magnetic fields. We solve thermo-hydrodynamic equations to obtain the spatial distribution of the local electron temperature in the linear-response regime. It is observed that, the variations of electron temperature exhibit an antisymmetry regarding the center of the sample in accordance with the location of incompressible strips. To understand the effect of sample mobility on the local electron temperature we impose a disorder potential calculated within the screening theory. Here, long range potential fluctuations are assumed to simulate cumulative disorder potential depending on the impurity atoms. We observe that the local electron temperature strongly depends on the number of impurities in narrow samples. The electron temperature $$T_e$$ versus position calculated for different values of the modulation potential $$V_0$$ . The calculations are done at $$T_\mathrm{L} = 0.04 \,E_F^0/k_B$$ lattice temperature considering impurity $$N_l = 6600$$ and repeated for three different values of magnetic field $$\hbar \omega _c/E_F^0 = 0.80$$ , 0.85 and 0.90. The insets show the enlarged region for the left side.

External Magnetic Field and Air Mass Effects on Carrier’s Effective Lifetime of a Bifacial Solar Cell under Transient State

This paper presents a theoretical study of the external magnetic field and the air mass effects on the carrier density, the transient open circuit voltage decay and the effective minority carrier’s lifetime in a polycrystalline silicon solar cell. From a theoretical approach based on the columnar model of the grains and the quasi-neutral base, the three-dimensional diffusion equation is established and the boundaries conditions are defined in order to use Green’s functions to solve this equation. New analytical expressions of carrier’s density and transient voltage are also found. The magnetic field and the air mass impacts on transient electrons density and transient open circuit voltage are then analyzed. The effective minority carrier lifetime is extracted from the curve versus time of transient open circuit voltage decay for different values of magnetic field and air mass.

Dilepton production rate calculation using MEQM in heavy-ion collision

It is established that a strong magnetic field is generated along with quark–gluon plasma in heavy-ion collision. This unique scenario offers an opportunity to study and analyze the impact of the magnetic field on the evolution of the plasma. We calculate the dilepton yield from quark–gluon plasma in a magnetic environment by considering a suitably modified magnetized effective quark mass (MEQM). Further, we study the dilepton yield for different values of magnetic field and different values of chemical potential with MEQM. The results obtained are very encouraging and we compare it with recently reported theoretical results.

Two-band superconducting square with a central defect: role of the deGennes extrapolation length

We present the influence of the deGennes extrapolation length on the vortex matter in a two band superconducting square with a central defect. This is determined by considering different values of the de Gennes extrapolation length b on the lateral surface of the sample. Our investigation was carried out by solving the two-dimensional time-dependent Ginzburg-Landau equations for a two-band system (2B-TDGL). We studied the density, magnetization, vorticity, and critical fields of the superconducting electrons as functions of the external applied magnetic field for different values of b on the surfaces of the sample and different sizes of the internal square defect. We show an unconventional vortex state due to the repulsive (attractive) short- (long-) range potential between the vortices. Finally, we show that at the limit of the thin film, a two-band system behaves like a three-band system.

Measurement of Some Argon Plasma Parameters Glow Discharge Under Axial Magnetic Field

This paper investigates the characteristics some of argon plasma parameters of glow discharge under axial magnetic field. The DC power supply of range (0-6000) V is used as a breakdown voltage to obtain the discharge of argon gas. The discharge voltage-current (V-I) characteristic curves and Paschen’s curves as well as the electrical conductivity were studied with the presents of magnetic field confinement at different gas pressures. The magnetic field up to 25 mT was obtained using four coils of radius 6 cm and 320 turn by passing A.C current up to 5 Amperes. Spectroscopic measurements are employed for purpose of estimating two main plasma parameters electron temperature (Te) and electron density (ne). Emission spectra from positive column (PC) zone of the discharge have been studies at different values of magnetic field and pressures at constant discharge currents of 1.5 mA. Electron temperature (Te) and its density are calculated from the ratio of the intensity of two emission lines of the same lower energy levels. Experimental results show the abnormal glow region characteristics (positive resistance). Breakdown voltage versus pressure curves near the curves of paschen and decrease as magnetic field increases due to magnetic field confinement of plasma charged particles. Also the electrical conductivity increases due to enhancing magnetic field at different gas pressures. Both temperature density of electron and the intensities of two selected emission lines decrease with increasing pressure due decreasing of mean free path of electron. Electron density increase according to enhancing magnetic field, while the intensity of emitting lines tends to decrease.

Large magnetocaloric effect, magnetic and electronic properties in Ho3Pd2 compound: Ab initio calculations and Monte Carlo simulations

The binary intermetallic Ho3Pd2, crystallize in an U3Si2-type tetragonal structure with the tP10, space group P4/mbm (no. 127). On the basis of Monte Carlo Simulations and ab initio calculations, we have studied the magnetism of the Ho3Pd2 compound. We show that the Ho3Pd2 is electronically stable. It has a ferromagnetic (FM) metallic with 84% spin polarization. The exchange energy calculated between the magnetic configurations confirms that the ground state FM is more stable than the antiferromagnetic (AFM) states. The total magnetic moment and the exchange couplings are deduced from ab initio calculations lead, using Monte Carlo simulations, to a quantitative agreement with the experimental transition temperatures. The maximum value of the magnetic entropy change was obtained near the paramagnetic (PM)-FM transition at transition temperature 9.6 k equal to 18.60 J.kg−1.K−1 for magnetic field ΔH = 5 T. These results are more consistent with the experimental results. Our results suggest that this material is a promising candidate for applications in specific technological fields at low temperatures and moderate fields. The relative cooling power and adiabatic temperature change of Ho3Pd2 compound have been calculated for different values of magnetic field. The obtained value for ΔH = 5 T is 230 J/kg. Arrott plots analysis reveals that our materials exhibit a second order magnetic phase transition.

Effect of magnetic field on specific heat and magnetic susceptibility of biased bilayer graphene: A full band approach

We have addressed the behaviors density of states and thermodynamic properties of doped biased bilayer graphene for AA stacking in the context of tight binding model hamiltonian. Specially we have studied the temperature dependence of spin susceptibility and specific heat of simple bilayer graphene in the presence of external magnetic field and bias voltage. The effects of electron doping and magnetic field on specific heat have been investigated. Green’s function approach has been implemented to find the behavior of electronic density of states and thermodynamic properties of bilayer graphene. We have found the temperature dependence of specific heat and spin susceptibility for different values of magnetic field and bias voltage in the presence of doping effects. Our results for density of states of bilayer graphene in the presence of bias voltage show the increase of magnetic field reduces the band gap width. Also there is a peak in temperature dependence of specific heat for all values of magnetic field and bias voltage. Moreover the effects of magnetic field and chemical potential on the behaviors of Pauli paramagnetic spin susceptibility have been addressed in details.

Magnetic Properties of Diluted Spinels Mg<i><sub>x</sub></i>Ni<sub>1−<i>x</i></sub>Fe<sub>2</sub>O<sub>4</sub> Systems: Are Studied by Green’s Functions and Mean Field Theories

Many-body Green's function, and mean field theories have been developed for magnetic systems MgxNi1−xFe2O4. We apply this theory to evaluate thermal magnetization and magnetic susceptibility for different values of magnetic field and dilution x, by considering all components of the magnetisation when an external magnetic field is applied in (x-z)-plane. The critical temperatures of MgxNi1−xFe2O4 systems in the range 0 ≤ x ≤ 1 have been deduced. The Green's function results are compared with the results of high temperature series expansion technique, and experimental magnetic measurements.

Magnetic field dependence of atomic collapse in bilayer graphene

The spectrum of a Coulomb impurity in bilayer graphene is investigated as function of the strength of a perpendicular magnetic field for different values of the angular quantum number $m$ and for different values of the gate voltage. We point out fundamental differences between the results from the two-band and four-band model. The supercritical instability and fall-to-center phenomena are investigated in the presence of a magnetic field. We find that in the four-band model the fall-to-center phenomenon occurs as in monolayer graphene, while this is not the case in the two-band model. We find that in a magnetic field the supercritical instability manifests itself as a series of anticrossings in the hole part of the spectrum for states coming from the low-energy band. However, we also find very distinct anticrossings in the electron part of the spectrum that continue into the hole part, which are related to the higher energy band of the four-band model. At these anticrossings, we find a very sharp peak in the probability density close to the impurity, reminiscent for the fall-to-center phenomenon. In this paper, these peculiar and interesting effects are studied for different magnetic field, interlayer coupling, and bias potential strengths.

Electron Energy Enhancement by Comparison of Linearly and Circularly Polarized Laser Pulse in Vacuum Using Different Values of Magnetic Fields

Energy enhancement by a comparison of circularly and linearly polarized laser pulse during acceleration of the electrons by a Gaussian laser pulses has been investigated. On comparison these two it is found that for the linearly polarized laser pulse the y-coordinate has a finite value and approximately zero for a circularly polarized laser pulse. It is noticed that there is a advantage of circularly polarized field. The comparison is done at high values of the magnetic field. The variation of electron energy with laser spot size, laser intensity, initial electron energy and initial phase has been studied. The maximum energy of the electrons gets enhanced for a circularly polarized in comparison to a linearly polarized laser pulse due to axial symmetry of the circularly polarized pulse. The ycomponent of the electric field of circularly polarized laser pulse contributes to the higher energy gained by the electrons.

Effect of rotating magnetic field on orientational dynamics of ferrocholesteric liquid crystals

We present numerical and analytical results describing the dynamics of a helical orientational structure of a ferrocholesteric liquid crystal, i.e., dilute suspension of ferromagnetic nanoparticles in a cholesteric liquid crystal, under the action of a rotating magnetic field. We employ the continuum theory to show how rotating magnetic field can untwist the helical ferrocholesteric structure and induce a ferrocholesteric–ferronematic transition. We analyze the non-stationary and stationary rotation regimes of the helical structure of a ferrocholesteric in a magnetic field. For weak fields, small and large rotational velocities the analytical expressions are obtained for the pitch of the ferrocholesteric helix. In the stationary rotational regime the orientational phase diagram of the ferrocholesteric–ferronematic transition is constructed for different values of magnetic field and angular velocities. It is shown that with increasing these parameters the transition field decreases. The dependence of a ferrocholesteric pitch on the magnetic field and its angular velocity at various material parameters is numerically obtained. We derive the analytical expression describing the divergence law for the pitch of a helix in the pre-transition region.

Magnetic properties of spinels GeNi2−xCoxO4 systems: Green's function and high-temperature series expansions

ABSTRACTThe Green's function theory and high-temperature series expansions technical have been developed for magnetic systems GeNi2−xCoxO4. We have applied the Green's function theory to evaluate thermal magnetization and magnetic susceptibility for different values of magnetic field and dilution x, considering all components of the magnetization when an external magnetic field is applied in (x,z)-plane. The second theory combined with the Padé approximants method for a randomly diluted Heisenberg magnet is used to deduce the magnetic phase diagram of GeNi2 − xCoxO4 systems. The critical exponents and associated with the magnetic susceptibility and the correlation length ξ, respectively, have been deduced. The theoretical results are compared with those given by magnetic measurements.

Static thermal conductivity of doped gapped graphene like structure in the presence of magnetic field

Thermal conductivity of doped monolayer graphene in the presence of gap parameter in the context of tight binding model hamiltonian has been addressed. The effect of magnetic field perpendicular to grapehene plane on thermal conductivity has been studied. Using Green's function approach, temperature dependence of thermal conductivity of grapehene plane has been found within linear response theory. We have found the temperature dependence of thermal conductivity for different values of magnetic field and gap parameter. Also a peak in the dependence of thermal conductivity on temperature has been observed. Moreover the temperature position of thermal conductivity goes to higher temperature for undoped graphene layer in the absence of magnetic field. Finally the behavior of thermal conductivity in terms of temperature for different magnetic fields has been studied in details.