Introduction and History Electromagnetic Wave Propagation
Velocity Wavelength Attenuation Dispersion
Rocks, Soils and Fluids: Electrical Properties
Magnetic Properties in Rocks, Soils and Fluids
![[Under Construction]](images/undercon.gif){kind=small}
Magnetic properties of most geological materials
are the same as those of vacuum, and it is common to assume the relative magnetic
permeability is equal to 1. However, the presence of iron and iron-bearing minerals
may result in significant losses due to ferromagnetic relaxation processes (Olhoeft, 1994). Ferromagnetism is the result of long range
correlation amongst electron spins. Motion (by diffusion) of magnetic domain
(regions of like spin alignment) walls results in energy dissipation. As the
magnetic permeability is a multiplier on everything else in the electromagnetic wave
propagation equation, ignoring it can result in significant errors of velocity estimation
(and hence over estimate depth) as well as over prediction of depth of investigation from
expected losses, and detectability from expected contrast (it modifies the Fresnel
reflection coefficient). Attributing all velocity, attenuation, and frequency
dependence to electrical properties alone will also result in incorrect estimation of soil
density and water content when magnetic properties are different from free space.
Magnetic properties are dominantly controlled by the presence,
volumetric abundance, and oxidation state (which can be controlled by either oxygen or
sulfur) of iron. The grain size distribution, domain size distribution, amount and
presence of titanium, and other factors may also be important. The most important
kinds of magnetic properties are those called ferromagnetism, ferrimagnetism and
superparamagnetism.
(references)
(figures)
Environmental Influences Heterogeneity, Anisotropy and Scale Radar Equation
Scattering Polarization Fresnel Reflection Snell Angle Stokes-Mueller Matrices Poincare Sphere
Antennas Coupling Near / Far Fields Waveguides Multipathing Resonance
Survey Design Contrast Geometry Resolution Depth of Investigation Orientation
Data Acquisition Data Processing Modeling Interpretation Uncertainty
Applications: Noninvasive Surface Borehole Airborne Satellite and Space