Electromagnetic Field of a Dipole Source over the Spherical Surface of Multi-Layered Earth

2009 ◽  
pp. 147-163
Author(s):  
Kai Li
Keyword(s):  
Electromagnetic Field ◽  
Spherical Surface ◽  
Dipole Source ◽  
Layered Earth

scholarly journals A STUDY OF THE ELECTROMAGNETIC FIELD FROM THE MCSEM DIPOLE SOURCE IN AN ANISOTROPIC LAYERED EARTH

2015 ◽  
Vol 33 (2) ◽  
Author(s):  
Walleson Gomes Dos Santos ◽  
Cícero Roberto Teixeira Régis
Keyword(s):  
Electromagnetic Field ◽  
Finite Thickness ◽  
Electrical Anisotropy ◽  
Dipole Source ◽  
Earth Model ◽  
Electromagnetic Modeling ◽  
Technical Literature ◽  
Layered Earth ◽  
Geometric Patterns ◽  
Ocean Layer

ABSTRACT. This paper studies the electromagnetic field from a horizontal electrical dipole inside a layered earth model with TIV anisotropy, including a visualization of the geometric patterns of the field through the medium. The objective here is to present a detailed formulation of the problem, as an aid to those who have an interest in modeling data from the Marine Controlled-Source ElectroMagnetic method – mCSEM, but find it hard to follow the usually abridged, often incomplete, descriptions found in the technical literature. We present a detailed vector potential formulation, with a semi-analytical solution, that allows the calculation of the fields with the source located in a finite thickness ocean layer over N-layered earth models. As an application, we use the implemented solution to study the geometrical distribution of the electric field generated by the dipole source in anisotropic layered media.Keywords: mCSEM, TIV electrical anisotropy, 1D electromagnetic modeling. RESUMO. Este artigo estuda o campo eletromagnético de um dipolo elétrico horizontal no interior de um modelo estratificado com anisotropia TIV, incluindo uma visualização da geometria das linhas de campo através do meio. O objetivo é apresentar a formulação detalhada do problema, para aqueles que têm interesse na modelagem de dados do método eletromagnético de fonte controlada marinho – mCSEM, mas encontram dificuldades em seguir as descrições geralmente muito resumidas, diversas vezes incompletas, na literatura técnica. Apresentamos uma formulação detalhada em termos do potencial vetorial, com uma solução semi-analítica que permite o cálculo dos campos com a fonte localizada em um oceano de espessura finita sobre uma terra estratificada com Ncamadas. Como aplicações, usamos a solução implementada para estudar a distribuição geométrica do campo elétrico gerado pelo dipolo fonte em meios estratificados anisotrópicos.Palavras-chave: mCSEM, anisotropia elétrica TIV, modelagem eletromagnética 1D.

scholarly journals Conditions for a pure toroidal dipole source

2021 ◽  
Vol 2015 (1) ◽  
pp. 012027
Author(s):  
Adrià Canós Valero
Keyword(s):  
Dipole Moment ◽  
Current Distribution ◽  
Electric Dipole ◽  
Spherical Surface ◽  
Physical Significance ◽  
Dipole Source ◽  
Multipole Moments ◽  
Physical Origin ◽  
First Time ◽  
A Current

Abstract Recently, the physical significance of dynamic toroidal multipoles in the context of electrodynamics has been put under discussion. Indeed, the latter can be shown to arise simply from a Taylor series of the exact source (Cartesian) multipole moments. The split into elementary and toroidal parts was demonstrated to lead to an unphysical result were forbidden components of the momentum transform of the current could radiate into free space. In this contribution, we elaborate the conditions that a current distribution must necessarily satisfy to be considered a ‘pure’ toroidal dipole source. We demonstrate for the first time that symmetry prevents such current distribution to radiate as an elementary electric dipole moment, without leading to an unphysical result. Thus, while both elementary electric dipole and toroidal dipoles are indistinguishable outside the source, they display topologically distinct characteristics within the smallest spherical surface enclosing the source itself and have different physical origin. Based on our results, a pure ‘toroidal’ source can be designed. We believe the outcome of our investigations will help clarify further the formal meaning of the toroidal multipoles.

A Comparative Study on the Difference between the Multi-dipole Sources and Vector Synthesis Source

2020 ◽  
Vol 25 (4) ◽  
pp. 529-543
Author(s):  
Xian-Xiang Wang ◽  
Ju-Zhi Deng
Keyword(s):  
Electromagnetic Field ◽  
Near Field ◽  
Electromagnetic Response ◽  
Dipole Source ◽  
Mountainous Area ◽  
Field Zone ◽  
Specific Direction ◽  
Single Dipole ◽  
The Difference ◽  
Dipole Sources

CSAMT exploration generally adopts a single dipole as the transmitter. The single dipole source has the apparent disadvantages–there are weak areas for all components, Ey and Hx are weak in the area where Ex and Hy are reliable. Moreover, it is hard to deploy the source with a specific direction in a rugged mountainous area. Given the shortcomings of the single dipole source, multi-dipole sources are introduced into CSAMT exploration. Although the dipole sources follow the principle of vector synthesis, the length of the source in actual exploration can last for several kilometers and the offset is generally a few kilometers. In this case, the source can no longer be regarded as a single dipole in the near-field zone. The electromagnetic field in this region becomes relatively complicated. We first compare the similarities and differences of electromagnetic field generated by vector synthesis source and multi-dipole source through the Ex radiation patterns. Then, we study the factors that affect electromagnetic response due to the substitution of the double-dipole source with the vector synthesis source. The measured EM fields is affected by the source length, frequency, the source angle, the offset, and the resistivity.Finally, we apply the double-dipole source to the 1D and 3D geological model and compare the difference between the electromagnetic field generated by the double-dipole source and that generated by the vector synthesis source. Usually, the difference is very obvious in the near-field zone, and is almost negligible in the far-field zone.

scholarly journals Exact solutions for electromagnetic fields inside and outside a spherical surface with magnetic/electric dipole distributed sources

2018 ◽  
Vol 64 (2) ◽  
pp. 139
Author(s):  
E. Ley-Koo ◽  
Ch. Esparza-López ◽  
H. Torres-Bustamante
Keyword(s):  
Exact Solutions ◽  
Electromagnetic Fields ◽  
Electric Dipole ◽  
Dipole Moments ◽  
Spherical Surface ◽  
Dipole Source ◽  
Radial Coordinate ◽  
Static Case ◽  
Point Dipole ◽  
Hankel Functions

Exact solutions of the Maxwell equations for the electromagnetic fields inside and outside a spherical surface, with time alternating magnetic or electric dipole source distributions, are constructed as alternatives to the respective familiar point-dipole solutions in undergraduate and graduate books. These solutions are valid for all positions, inside and outside the sphere, including the quasi-static, induction and radiation zones; the solutions inside make the difference from the point-dipole solutions; the definitions of the dynamic dipole moments must be based on the ordinary spherical Bessel functions for the solutions outside, and on the outgoing spherical Hankel functions for the solutions inside,instead of the powers of the radial coordinate as solutions of the Laplace equation valid for the static case. The solutions for the resonating cavities are associated with the nodes of the spherical Bessel function for the TE modes of the magnetic dipole source, and with the extremes of the product of the radial coordinate times the same spherical function for the TM modes of the electric dipole source; both conditions also guarantee the vanishing of the fields outside.

Sign in / Sign up

Export Citation Format

Share Document