Basic magnetic theory
ENVI-MAG Manual B1-5
Overview
Shape
The shape of a magnetizable body also determines the shape of the
magnetic anomaly that you can measure. Compact bodies give rise to one
shape of anomaly, while long thin bodies or flat, sheet-like bodies give rise to
others. These different magnetizable bodies can be represented as simple
assemblages of magnetic monopoles or dipoles. Figure B-6 on page B1-6
illustrates the magnetic field lines around typical dipole and monopole
bodies, and the resulting total field with the Earth’s magnetic field added. A
confined body is illustrated on the left whereas a long and infinite body is
illustrated on the right. The fall-off rates for a dipole or line of dipoles would
vary as a cube power (1⁄ r
3
), while that of a monopole or line of monopoles
would fall-off as a square power (1⁄ r
2
).
Figure B-5 Typica l t ar ge ts.
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