The AC/DC module in Comsol can be used to solve Maxwell's equations in the quasi-static limit for modeling the magnetotelluric response. In this effort, we present magnetotelluric models of layered Earth, uplift structures, auroral electrojets, and geomagnetically induced currents in power-line skywires using the commercial finite-element package Comsol Multiphysics.
While there are many different modeling techniques, the finite element method is most commonly used. For example, modeling a subsurface conductive body in terms of its conductivity, geometry and dipping angle would yield substantial information on the phase response and sensitivity in an MT survey. Numerical modeling of magnetotellurics is important for survey design, inversion, geological interpretation and many other aspects of geophysical studies. Magnetotellurics is an electromagnetic geophysical method that has been widely used to study structures in Earth's subsurface. Numerical calculations and comparisons with exact solutions show that SER and CIM are very accurate.
EARTH MAGNETIC FIELD CALCULATOR SERIES
The applicability of a series expansion technique (SER) and the complex image method (CIM), both of which were originally developed for other disciplines, are reviewed and summarized by giving the expressions of the electric and magnetic fields at the Earth's surface and by considering the mathematical assumptions required. We consider the exact integral expressions of the fields at the Earth's surface. The Earth is assumed to be composed of horizontal layers. In this paper, we consider an infinitely long horizontal line current, which is the basic model of an auroral electrojet and simple enough to give insight into the physics and calculation techniques.
The calculation methods should be fast enough that they can be applied to forecasting the fields and GIC, for example, by using satellite observations of the solar wind. The surface fields are also affected by currents induced within the ground and influenced by the conductivity of the Earth. For assessing the hazards it is necessary to estimate GIC magnitudes, and this requires calculations of the electric and magnetic fields produced at the Earth's surface by the ionospheric currents. The electric fields drive geomagnetically induced currents (GIC) in technological networks and may have serious impacts. 1] Space weather storms involve intense and rapidly varying electric currents in the ionosphere, which create electric and magnetic fields at the Earth's surface.
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