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https://github.com/wassname/simpeg.git
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Lindsey Heagy
94 lines
2.9 KiB
ReStructuredText
94 lines
2.9 KiB
ReStructuredText
.. _api_FDEM:
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.. math::
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\renewcommand{\div}{\nabla\cdot\,}
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\newcommand{\grad}{\vec \nabla}
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\newcommand{\curl}{{\vec \nabla}\times\,}
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Frequency Domain Electromagnetics
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*********************************
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Intro Here
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Background
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==========
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Electromagnetic geophysical methods are used
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Conventions
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-----------
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In order to examine Maxwell's equations in the frequency domain, we must first define our choice of harmonic time-dependence by choosing a Fourier transform convention. We use the \\e^{i\omega t}\\ convention, so we define our Fourier Transform pair as
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.. math ::
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F(\omega) = \int_{-\infty}^{\infty} f(t) e^{- i \omega t} dt
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.. math ::
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f(t) = \frac{1}{2\pi}\int_{-\infty}^{\infty} F(\omega) e^{i \omega t} d\omega
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where \\ \omega\\ is angular frequency, \\t\\ is time, \\ F(\omega) \\ is the function defined in the frequency domain and \\ f(t) \\ is the function defined in the time domain.
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Maxwell's Equations
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===================
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In the frequency domain, Maxwell's equations are given by
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.. math::
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\curl \vec{E} = - i \omega \vec{B} \\
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\curl \vec{H} = \vec{J} + i \omega \vec{D} + \vec{J_s} \\
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\div \vec{B} = 0 \\
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\div \vec{D} = \rho_f
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where:
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- \\ \vec{E} \\ : electric field (\\V/m\\)
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- \\ \vec{H} \\ : magnetic field (\\A/m\\)
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- \\ \vec{B} \\ : magnetic flux density (\\Wb/m^2\\)
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- \\ \vec{D} \\ : electric displacement / electric flux density (\\C/m^2\\)
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- \\ \vec{J} \\ : electric current density (\\A/m^2\\)
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- \\ \rho_f \\ : free charge density
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The source term is \\ \vec{J_s} \\
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Constitutive Relations
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----------------------
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The fields and fluxes are related through the constitutive relations. At each frequency, they are given by
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.. math::
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\vec{J} = \sigma \vec{E} \\
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\vec{B} = \mu \vec{H} \\
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\vec{D} = \varepsilon \vec{E}
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where
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- \\ \sigma \\ : electrical conductivity (S/m)
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- \\ \mu \\ : magnetic permeability (H/m)
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- \\ \varepsilon \\ : dielectric permittivity (F/m)
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\\ \sigma \\, \\ \mu \\, \\ \varepsilon \\ are physical properties which depend on the material. \\ \sigma \\ describes how easily electric current passes through a material, \\ \mu \\ describes how easily a material is magnetized, and \\ \varepsilon \\ describes how easily a material is electrically polarized. In most geophysical applications of EM, \\ \sigma \\ is the the primary physical property of interest, and \\ \mu \\, \\ \varepsilon \\ are assumed to have their free-space values \\ \mu_0 = 4\pi \times 10^{-7} H/m\\, \\ \varepsilon_0 = 8.85\times 10^{-12} F/m\\
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For a more complete discussion of physical properties see `GPG <http://www.eos.ubc.ca/courses/eosc350/content/index.htm>`_
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Quasi-static Approximation
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--------------------------
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Fields from a Dipole
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--------------------
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Forward Problem
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===============
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Inverse Problem
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===============
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API
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===
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.. automodule:: simpegEM.FDEM.FDEM
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:show-inheritance:
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:members:
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:undoc-members:
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FDEM Survey
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-----------
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.. automodule:: simpegEM.FDEM.SurveyFDEM
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:show-inheritance:
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:members:
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:undoc-members:
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