Abstract

An analog method can provide quick and accurate computation of gravity and magnetic anomalies arising from bodies in the form of horizontal cylinders of any arbitrary cross section and polarization. It has been possible to simulate the gravitational and magnetic fields of such a body by a current system flowing along a set of parallel wires. The underlying principle is that the magnetic field due to current in a long straight wire is mathematically similar to the gravitational field due to a line mass of uniform density. This similarity has been extended to the magnetic case, since the currents in the opposite directions reproduce the fields due to positive and negative line poles.Comparison of the simulated field for some simple bodies has been made with theoretically computed values. Generally, these agreed within less than 3 percent error. In the case of the magnetic analog it has been possible to reproduce the field for any direction of polarization perpendicular to the strike.It is also possible to simulate the effects of density changes or changes in susceptibility contrast and in permanent magnetism. The method may be extended to the measurement of magnetic field components for any direction of strike of the body. Torsion balance quantities may be simulated as well as simple field quantities.

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