Magnetic Maps

Magnetic Maps

 

maps of the earth’s surface on which iso-lines (isodynamic, isogonic, and isoclinal) are used to show the distribution of the intensity of the geomagnetic field or its components.

Magnetic maps of the world and of anomalous magnetic fields are most common. World maps reflect the basic characteristics of the main geomagnetic field (the normal field), the source of which is considered to be the movement of electroconductive matter in the earth’s core. The dimensions of the structural features of the main field approximate the dimensions for the continents, so that the usual scale of the world maps is 1:10,000,000 or less. Deviations caused by irregularities in the structure of the earth’s crust, the occurrence of ore deposits, and other local factors are smoothed out on the world maps, but maps of anomalous magnetic fields reflect local deviations of the geomagnetic field from the main. These deviations are ordinarily observed in areas whose linear dimensions are on the order of dozens of km or less. Therefore, magnetic maps of anomalous fields are on a larger scale than world maps (for example, 1:200,000) and are usually compiled on the basis of aeromagnetic surveying. Magnetic maps are essential in studying the structure of the earth’s interior and in prospecting for minerals. Owing to secular changes in the earth’s magnetic field, magnetic maps go out of date and must be redone periodically (every five or ten years).

REFERENCE

lanovskii, B. M. Zemnoi magnetizm [3rd ed.], vol 1. Leningrad, 1964.

V. N. LUGOVENKO

References in periodicals archive ?
Generally, the qualitative interpretation for the magnetic maps, aims to get a clear view of the subsurface structures and an estimation of the relative depth of magnetic anomalies sources.
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Dessler of the University of Arizona in Tucson says the study indicates that magnetic maps of Jupiter generated form Voyager data are more accurate than those form Pioneer 141.
A comparison with magnetic maps of the photosphere, obtained with the Helioseismic Magnetic Imager aboard SDO, showed that the cells were centered on unipolar flux concentrations, but left doubt about whether the cellular emission was coming from the tops of closed loops near the Sun's surface, or from longer field lines that extend higher into the corona.
A visual study of magnetic maps can be fruitful for preliminary interpretation (Telford et al, 1998) Visual studies of total aeromagnetic intensity contour map (Figure 2) and the residual aeromagnetic intensity contour map (Figure 3) of Wamba and its adjoining areas revealed variations in magnetic field intensity throughout the area.
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