Lossy Half-Space Born Approximation Modeling of Electromagnetic Wave Source and Scattering in Soil by Cross Well Radar

2005 ◽  
Author(s):  
H. Zhan ◽  
C. Rappaport ◽  
M. Farid ◽  
A. Alshawabkeh ◽  
H. Raemer
Keyword(s):  
Electromagnetic Wave ◽  
Half Space ◽  
Born Approximation ◽  
Wave Source

Inversion of slingram electromagnetic induction data using a Born approximation

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. E201-E212 ◽  
Author(s):  
Jochen Kamm ◽  
Michael Becken ◽  
Laust B. Pedersen
Keyword(s):  
Half Space ◽  
Born Approximation ◽  
High Efficiency ◽  
Three Dimensions ◽  
Background Model ◽  
Desktop Computer ◽  
Near Surface ◽  
Homogeneous Half Space ◽  
Integral Equation Formulation ◽  
Forward Operator

We present an efficient approximate inversion scheme for near-surface loop-loop EM induction data (slingram) that can be applied to obtain 2D or 3D models on a normal desktop computer. Our approach is derived from a volume integral equation formulation with an arbitrarily conductive homogeneous half-space as a background model. The measurements are not required to fulfill the low induction number condition (low frequency and conductivity). The high efficiency of the method is achieved by invoking the Born approximation around a half-space background. The Born approximation renders the forward operator linear. The choice of a homogeneous half-space yields closed form expressions for the required electromagnetic normal fields. It also yields a translationally invariant forward operator, i.e., a highly redundant Jacobian. In connection with the application of a matrix-free conjugate gradient method, this allows for very low memory requirements during the inversion, even in three dimensions. As a consequence of the Born approximation, strong conductive deviations from the background model are underestimated. Highly resistive anomalies are in principle overestimated, but at the same time difficult to resolve with induction methods. In the case of extreme contrasts, our forward model may fail in simultaneously explaining all the data collected. We applied the method to EM34 data from a profile that has been extensively studied with other electromagnetic methods and compare the results. Then, we invert three conductivity maps from the same area in a 3D inversion.

The outgoing time-harmonic electromagnetic wave in a half-space with non-absorbing impedance boundary condition

2019 ◽  
Vol 53 (1) ◽  
pp. 325-350
Author(s):  
Sergio Rojas ◽  
Ignacio Muga ◽  
Carlos Jerez-Hanckes
Keyword(s):  
Boundary Condition ◽  
Electromagnetic Wave ◽  
Asymptotic Analysis ◽  
Radiation Pattern ◽  
Half Space ◽  
Existence And Uniqueness ◽  
Radiation Condition ◽  
Impedance Boundary Condition ◽  
Impedance Boundary ◽  
Time Harmonic

We show existence and uniqueness of the outgoing solution for the Maxwell problem with an impedance boundary condition of Leontovitch type in a half-space. Due to the presence of surface waves guided by an infinite surface, the established radiation condition differs from the classical one when approaching the boundary of the half-space. This specific radiation pattern is derived from an accurate asymptotic analysis of the Green’s dyad associated to this problem.

Reflection of waves at an interface in a streaming plasma

1968 ◽  
Vol 2 (3) ◽  
pp. 381-393
Author(s):  
P. C. Clemmow ◽  
E. Ott
Keyword(s):  
Electromagnetic Wave ◽  
Half Space ◽  
Cold Plasma ◽  
Plane Electromagnetic Wave ◽  
Plasma Stream ◽  
Relativistic Velocity ◽  
Reflected Wave ◽  
First Approximation ◽  
Transmitted Waves ◽  
The Face

A uniform, unbounded, cold plasma stream, with relativistic velocity (0,U, 0), traverses a vacuum half-spacey> 0 and a dielectric half-spacey< 0. A plane electromagnetic wave in the plasma stream iny> 0 is incident obliquely on the face of the dielectric. The criterion for determining which characteristic waves are present in each half space is discussed, and it is shown that, for the polarization in which B is parallel toy= 0, there is one reflected wave and three transmitted waves. One of the latter can be an amplifying wave. A first approximation to the transmission and reflexion coefficients is found in the case when the density of the stream is low.

Sign in / Sign up

Export Citation Format

Share Document