An analytic solution for numerical modeling validation in electromagnetics: the resistive sphere. Issue 2 (2nd August 2017)

• Record Type: Journal Article
• Authors: Swidinsky, Andrei; Liu, Lifei
• Is Part Of: Geophysical journal international. Volume 211:Issue 2(2017:Nov.)
• Page Start: 843
• Page End: 850
• Publication Date: 2017-08-02
• Subjects: Controlled source electromagnetics (CSEM) -- Electromagnetic theory -- Marine electromagnetics; Geophysics -- Periodicals; 550
• DOI: 10.1093/gji/ggx331
• Languages: English
• ISSNs: 0956-540X

Abstract

Abstract: We derive the electromagnetic response of a resistive sphere to an electric dipole source buried in a conductive whole space. The solution consists of an infinite series of spherical Bessel functions and associated Legendre polynomials, and follows the well-studied problem of a conductive sphere buried in a resistive whole space in the presence of a magnetic dipole. Our result is particularly useful for controlled-source electromagnetic problems using a grounded electric dipole transmitter and can be used to check numerical methods of calculating the response of resistive targets (such as finite difference, finite volume, finite element and integral equation). While we elect to focus on the resistive sphere in our examples, the expressions in this paper are completely general and allow for arbitrary source frequency, sphere radius, transmitter position, receiver position and sphere/host conductivity contrast so that conductive target responses can also be checked. Commonly used mesh validation techniques consist of comparisons against other numerical codes, but such solutions may not always be reliable or readily available. Alternatively, the response of simple 1-D models can be tested against well-known whole space, half-space and layered earth solutions, but such an approach is inadequate for validating models with curved surfaces. We demonstrate that our theoretical results can be used as a complementary validation tool by comparing analytic electric fields to those calculated through a finite-element analysis; the software implementation of this infinite series solution is made available for direct and immediate application.