Presence Of Magnetic Sources Research Articles

Determination of depths to magnetic sources within Abakaliki–Afikpo area and environs, Southeastern Nigeria: implications for mineral and hydrocarbon prospectivity

There have been repeated calls from various quarters in Nigeria for a robust examination of Abakaliki anticlinorium and Afikpo sub-basin of the Southern Benue Trough for their mineral and hydrocarbon prospects. The Southern Benue Trough is part of a linear NE-SW trending rift system whose development is related to the breakaway of Africa from South America and the subsequent opening of the South Atlantic Ocean during the Cretaceous. Detailed geophysical studies were carried out with the high resolution aeromagnetic data using analytical techniques which include spectral analysis, analytic signal (AS) evaluations, Euler deconvolution, potential field transformation and two-dimensional potential field modelling of subsurface geology. Results reveal varying depths ranging from 0.41 to 0.67 km for depths to magnetic sources, and 1.0–5.5 km for basement depths. The presence of magnetic sources within the sedimentary basins is indicated by shallow depths to the top (DTT) of magnetic sources. Euler depth estimates ranging between 1.0 and 4.8 km for the magnetic source contacts/faults concurs with depths to the basement of between 4.5 and 4.9 km realised from the 2D modelling. Euler deconvolution of the magnetic anomalies also revealed the presence of Sill and Dyke structures at Amuzu, Enyigba, parts of Abakaliki, Utampa, Abriba, Afikpo, Ugep, and Agoi Ekpo regions with varying depths of up to 3.5 km. Structures mapped around Okposi, Amuzu, Enyigba Abakaliki, and Ishieke areas present viable prospects for hydrocarbon exploration. Structures identified at the Afikpo region could best represent mineral lode within the area. The 2D modelling shows various subsurface geological structures to include faults, fractures, sill, dyke, and considerable basement intrusion within the profile. Results from this study have identified an expanse of untapped areas with higher prospectivity which could be exploited for productive and viable mineral and hydrocarbon explorations.

Dirac branes for Dirichlet branes: Supergravity actions

Nontrivial Bianchi identities with local magnetic sources are solved by recognizing that gauge potentials are sections rather than globally defined functions, but properly accounting for the source degrees of freedom requires a modification of the field strength. Following work by Teitelboim and by Cariglia and Lechner, we extend Dirac's string formalism for monopoles to D-branes in type IIA and IIB string theory. We give novel derivations of brane-induced Chern-Simons terms in the supergravity actions, including a prescription for integrating over potentials in the presence of magnetic sources. We give a noncovariant formulation of the IIB theory, keeping only the independent degrees of freedom of the self-dual 4-form potential. Finally, it is well-known that D8-branes source the mass parameter of IIA supergravity; we show that the additional couplings of the massive IIA supergravity, including on other D-brane worldvolumes, are a consequence of the corresponding Dirac branes.

Influence of localized magnetic field and strong viscosity on the biomagnetic fluid flow in a rectangular channel

In this paper biomagnetic fluid flow in a rectangular enclosure is studied under the influence of applied magnetic field and temperature-dependent viscosity. An electrically conducting magnetic fluid (blood) is considered here which also exhibits magnetization. It is assumed that the magnetization M¯ of the fluid is varying linearly with temperature T¯ and magnetic field intensity H¯. The viscosity μ¯ of biofluid is taken to be an exponential function of temperature. The mathematical model for the present problem results in a nonlinear and coupled system of equations and is given in stream function-vorticity-temperature formulation for the purpose of numerical treatment. Solutions are obtained iteratively by employing upwind scheme together with successive over relaxation method. Numerical results are presented in terms of average Nusselt number, streamlines, isotherms and vorticity function contours indicating that presence of magnetic source and viscosity variations influences the flow field considerably. It is found that the strength of the vortices and the temperature increases by magnifying the magnetic intensity and circular contours are generated extensively for the blood having variable viscosity.

Study of Fe3O4-water nanofluid with convective heat transfer in the presence of magnetic source

Influence of external magnetic source on ferrofluid convection in an enclosure with elliptic hot cylinder is studied. Governing formulae are first made dimensionless form along with the associated boundary conditions and then solved by powerful numerical method namely CVFEM. Influences of Rayleigh and Hartmann numbers and Fe3O4 volume fraction on hydrothermal behavior are presented. Results indicated that temperature gradient is an enhancing function of volume fraction of Fe3O4 and Rayleigh number but it is a reducing function of Lorentz forces. Lorentz forces cause the nanofluid velocity to reduce and augment the thermal boundary layer thickness. The role of effective parameters is illustrated through graphs and tables. Comparison of the present work is also made with the existing literature.

Ferrofluid flow and heat transfer in a semi annulus enclosure in the presence of magnetic source considering thermal radiation

In this paper, ferrofluid flow and heat transfer in a semi annulus enclosure is investigated considering thermal radiation. The enclosure has a wall with constant heat flux boundary condition. Combined effects of Ferrohydrodynamic (FHD) and magnetohydrodynamic (MHD) are considered. It is assumed that the magnetization of the fluid is varying linearly with temperature and magnetic field intensity. Control Volume based Finite Element Method (CVFEM) is applied to solve the governing equations. The calculations were performed for different governing parameters namely; the Radiation parameter, Rayleigh number, nanoparticle volume fraction, Magnetic number arising from FHD and Hartmann number arising from MHD. Results show that Nusselt number is an increasing function of Rayleigh number, nanoparticle volume fraction, magnetic number while it is a decreasing function of with Hartmann number and radiation parameter.

BEM and FEM based numerical simulations for biomagnetic fluid flow

We investigate numerically the biomagnetic fluid flow between parallel plates imposed to a magnetic source placed below the lower plate. The biomagnetic fluid is assumed to be Newtonian, viscous, incompressible, electrically nonconducting, and has magnetization varying linearly with temperature and magnetic field intensity. Both steady and unsteady, laminar, two-dimensional biomagnetic fluid flow equations taking into care the heat transfer between the plates are solved using both finite element and dual reciprocity boundary element methods. Treatment of nonlinear terms by using only the fundamental solution of the Laplace equation, and discretization of only the boundary of the region are the advantages of dual reciprocity boundary element method giving small algebraic systems to be solved at a small expense. Finite element method is capable of giving very accurate results by discretizing the region affected by the magnetic source very finely, but it results in large sized algebraic systems requiring high computational cost. The results indicate that the flow is appreciably affected with the presence of magnetic source in terms of vortices at the magnetic source area. The lengths of the vortices, and temperature increase with an increase in the intensity of the magnetic field.

Classical Electromagnetic Field Theory in the Presence ofMagnetic Sources

Using two new well-defined four-dimensional potential vectors, weformulate the classical Maxwell field theory in a form which hasmanifest Lorentz covariance and SO(2) duality symmetry in the presenceof magnetic sources. We set up a consistent Lagrangian for the theory.Then from the action principle we obtain both Maxwell's equation and theequation of motion of a dyon moving in the electromagnetic field.

ELECTROMAGNETIC DUALITY ON THE LIGHT-FRONT IN THE PRESENCE OF EXTERNAL SOURCES

We investigate the issue of electromagnetic duality on the light-front. We work with Zwanziger's theory of electric and magnetic sources which is appropriate for treating duality. When quantized on the light-front in the light-front gauge, this theory yields two independent phase space degrees of freedom, namely the two transverse field components, the right number to describe the gauge field sector of normal light-front QED and also the appropriate commutator between them. The electromagnetic duality transformation formulated in terms of them is similar in form to the Susskind transformation proposed for the free theory, provided one identifies them as the dynamical field components of the photon on the light-front in the presence of magnetic sources. The Hamiltonian density written in terms of these components is invariant under the duality transformation.

Electromagnetic Duality on Light-Front in Presence of External Sources

We investigate the issue of electromagnetic duality on the light front. We work with Zwanziger's theory of electric and magnetic sources which is appropriate for treating duality. When quantized on the light-front in the light front gauge, this theory yields two independent phase space degrees of freedom, namely the two transverse field components, the right number to describe the gauge field sector of normal light-front QED and also the appropriate commutator between them. The electromagnetic duality transformation formulated in terms of them is similar in form to the Susskind transformation proposed for the free theory, provided one identifies them as the dynamical field components of the photon on the light-front in the presence of magnetic sources. The Hamiltonian density written in terms of these components is invariant under the duality transformation.

Distinguishing buried alluvium from till by using detailed total-magnetic-field data

Total-magnetic-field and vertical-magnetic-gradient profiles are characteristically different over alluvial and glacial sediments. Positive magnetic anomalies elongated in the river-valley direction but not in the structural trend of the underlying bedrock indicate the occurrence of magnetite enrichments within the alluvium. No evidence for such anomalies is found in survey data obtained in gravel pits located in tills. The logarithm of the power of the total-field profiles over the river terraces plotted against spatial frequency is structured, which is indicative of the presence of magnetic sources of certain depth and width. However, the power spectra over till may also show similar features if high-frequency bedrock anomalies are present in the data, so these spectra are not a reliable means of distinguishing between buried alluvium and till. The results show that magnetic analysis allows the discrimination between buried tills and alluvium in which magnetite concentrations of considerable lateral extent were formed.

Magnetic sources and 3-cocycles (comment)

The argument for a 3-cocycle in the presence of magnetic sources is restated.