Low-frequency scattering from perfectly conducting spheroidal bodies in a conductive medium with magnetic dipole excitation

2009 ◽  
Vol 47 (3) ◽  
pp. 372-390 ◽  
Author(s):  
Panayiotis Vafeas ◽  
Gaële Perrusson ◽  
Dominique Lesselier
Keyword(s):  
Magnetic Dipole ◽  
Low Frequency ◽  
Conductive Medium ◽  
Dipole Excitation

scholarly journals Electromagnetic Low-Frequency Dipolar Excitation of Two Metal Spheres in a Conductive Medium

2012 ◽  
Vol 2012 ◽  
pp. 1-37 ◽  
Author(s):  
Panayiotis Vafeas ◽  
Polycarpos K. Papadopoulos ◽  
Dominique Lesselier
Keyword(s):  
Magnetic Dipole ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Low Frequency ◽  
Wave Number ◽  
Conductive Medium ◽  
Time Harmonic ◽  
Frequency Interaction ◽  
Minor Significance ◽  
Infinite Linear Systems

This work concerns the low-frequency interaction of a time-harmonic magnetic dipole, arbitrarily orientated in the three-dimensional space, with two perfectly conducting spheres embedded within a homogeneous conductive medium. In such physical applications, where two bodies are placed near one another, the 3D bispherical geometry fits perfectly. Considering two solid impenetrable (metallic) obstacles, excited by a magnetic dipole, the scattering boundary value problem is attacked via rigorous low-frequency expansions in terms of integral powers(ik)n, wheren≥0,kbeing the complex wave number of the exterior medium, for the incident, scattered, and total non-axisymmetric electric and magnetic fields. We deal with the static (n=0) and the dynamic (n=1,2,3) terms of the fields, while forn≥4the contribution has minor significance. The calculation of the exact solutions, satisfying Laplace’s and Poisson’s differential equations, leads to infinite linear systems, solved approximately within any order of accuracy through a cut-off procedure and via numerical implementation. Thus, we obtain the electromagnetic fields in an analytically compact fashion as infinite series expansions of bispherical eigenfunctions. A simulation is developed in order to investigate the effect of the radii ratio, the relative position of the spheres, and the position of the dipole on the real and imaginary parts of the calculated scattered magnetic field.

scholarly journals Quasi-Static Solution for ELF/SLF near-Zone Field of a Vertical Magnetic Dipole near the Surface of a Lossy Half-Space

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Lina He ◽  
Tong He ◽  
Kai Li
Keyword(s):  
Magnetic Dipole ◽  
Numerical Solutions ◽  
Low Frequency ◽  
Analytical Techniques ◽  
Static Solution ◽  
Static Approximation ◽  
Near Zone ◽  
Vertical Magnetic Dipole ◽  
Validity Limit ◽  
Zone Field

Dipole antennas over the boundary between two different media have been widely used in the fields of geophysics exploration, oceanography, and submerged communication. In this paper, an analytical method is proposed to analyse the near-zone field at the extremely low frequency (ELF)/super low frequency (SLF) range due to a vertical magnetic dipole (VMD). For the lack of feasible analytical techniques to derive the components exactly, two reasonable assumptions are introduced depending on the quasi-static definition and the equivalent infinitesimal theory. Final expressions of the electromagnetic field components are in terms of exponential functions. By comparisons with direct numerical solutions and exact results in a special case, the correctness and effectiveness of the proposed quasi-static approximation are demonstrated. Simulations show that the smallest validity limit always occurs for component H2z, and the value of k2ρ should be no greater than 0.6 in order to keep a good consistency.

scholarly journals New magnetic dipole excitation mode studied in the heavy deformed nucleus 156Gd by inelastic electron scattering

1984 ◽  
Vol 137 (1-2) ◽  
pp. 27-31 ◽  
Author(s):  
D. Bohle ◽  
A. Richter ◽  
W. Steffen ◽  
A.E.L. Dieperink ◽  
N. Lo Iudice ◽  
...  
Keyword(s):  
Magnetic Dipole ◽  
Electron Scattering ◽  
Inelastic Electron ◽  
Excitation Mode ◽  
Dipole Excitation ◽  
Inelastic Electron Scattering ◽  
Deformed Nucleus

Crosswell Magnetic Sensing of Superparamagnetic Nanoparticles for Subsurface Applications

SPE Journal ◽  
2015 ◽  
Vol 20 (05) ◽  
pp. 1067-1082 ◽  
Author(s):  
Amir Reza Rahmani ◽  
Steve Bryant ◽  
Chun Huh ◽  
Alex Athey ◽  
Mohsen Ahmadian ◽  
...  
Keyword(s):  
Magnetic Dipole ◽  
Low Frequency ◽  
Superparamagnetic Nanoparticles ◽  
Dipole Source ◽  
Hydrodynamic Dispersion ◽  
Magnetic Response ◽  
Induction Effect ◽  
Low Frequencies ◽  
Early Stages ◽  
Magnetic Contrast

Summary Stable dispersions of superparamagnetic nanoparticles that are already in use in biomedicine as image-enhancing agents also have potential use in subsurface applications. Surface-coated nanoparticles are capable of flowing through micron-sized pores across long distances in a reservoir, with modest retention in rock. These particles change the magnetic permeability of the flooded region, and thus one can use them to enhance images of the flood. In this paper, we model the propagation of a “ferrofluid” slug in a reservoir and its response to a crosswell magnetic tomography system. This approach to monitoring fluid movement within a reservoir is built on established electromagnetic (EM) conductivity-monitoring technology. In this work, however, we investigate the contrast between injected and resident fluids when they have different magnetic permeabilities. Specifically, we highlight the magnetic response at low frequency to the magnetic excitations generated by a vertical magnetic dipole source positioned at the injection well. At these frequencies, the induction effect is small, the casing effect is manageable, the crosswell response originates purely from the magnetic contrast in the formation, and changes in fluid conductivities are irrelevant. The sensitivity of the measurements to the magnetic slug is highest when the slug is closest to the source or receivers and lower when the slug is midway in the interwell region. At low frequencies, the magnetic response of the ferrofluid slug is largely independent of frequency. As expected for the conductive slug, the sensitivity of the inductive measurements is negligible at low frequencies whereas significant levels of detectability result at higher frequencies. We demonstrate sensitivity to the vertical boundaries of the slug by shifting the vertical position of the excitation source relative to the magnetic slug. The slug geometry plays a key role in determining the magnetic response. With a fixed volume of ferrofluid, there is an optimum slug geometry that results in the maximum magnetic response. Hydrodynamic dispersion of the slug has negligible effect on the magnetic response during early stages of the waterflood. As the slug travels farther into the formation, however, dispersion reduces the concentration of nanoparticles, and the spatial contributions of the magnetic measurements are more diffuse. We illustrate how these low-frequency excitation behaviors are consistent with the quasistatic magnetic dipole physics. The fact that the progress of the magnetic slug can be detected at very early stages of the flood, that the traveling slug's vertical boundaries can be identified at low frequencies, and that the magnetic nanoparticles can be sensed well before the actual arrival of the slug at the observer well provide significant value of the use of the magnetic-contrast agents in crosswell EM tomography.

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