Electromagnetic scattering by two-dimensional inhomogeneity due to an oscillating magnetic dipole
A numerical method of computing the electromagnetic response of two-dimensional earth models to an oscillating magnetic dipole is presented. The generalized electromagnetic variational integral is reduced to a sum of two-dimensional variational integrals by Fourier transformation. Discretization of each two-dimensional integral is carried out is terms of the secondary electric fields using the finite element method. Following the variational principle, each harmonic integral is reduced to a set of simultaneous equations. From each set of electric field solutions obtained by solving the simultaneous equations, the secondary magnetic fields are computed numerically. After inversely Fourier transforming the secondary electric and magnetic fields, the total fields are finally obtained by adding and analytically calculated primary fields. In order to formulate the source vector associated with each set of simultaneous equations, both the secondary fields along the external boundary and the primary electric fields at every node must be supplied. These field values are directly computed in harmonic space using an algorithm developed for this purpose. The secondary field used in the total field with the free space dipolar field subtracted. When a horizontal magnetic dipole is located close to or on the surface of the earth, it is found that the solution obtained in the manner described is greatly in error. It is not possible to perform an absolute numerical check of the solution due to the lack of another independently developed solution against which it can be checked. As an alternative, the solutions for two dimensional models have been compared to those for some elongated three-dimensional models whose cross sections correspond to the two-dimensional models.
- Research Organization:
- California Univ., Berkeley (USA)
- OSTI ID:
- 5374978
- Country of Publication:
- United States
- Language:
- English
Similar Records
Electromagnetic induction by a finite electric dipole source over a 2-D earth
Numerical solutions of the response of a two-dimensional earth to an oscillating magnetic dipole source
Related Subjects
580203* -- Geophysics-- Geophysical Survey Methods-- (1980-1989)
DIPOLES
ELECTRIC FIELDS
ELECTROMAGNETISM
FINITE ELEMENT METHOD
FOURIER TRANSFORMATION
GEOPHYSICS
INHOMOGENEOUS FIELDS
INTEGRAL TRANSFORMATIONS
MAGNETIC DIPOLES
MAGNETIC FIELDS
MAGNETISM
MULTIPOLES
NUMERICAL SOLUTION
OSCILLATIONS
TRANSFORMATIONS
TWO-DIMENSIONAL CALCULATIONS