Magnetic Anomalies, Long Wavelength
Reference work entry
Long‐wavelength anomalies are static or slowly varying features of the geomagnetic field, and originate largely within the lithosphere. These anomalies stand in contrast to the rapidly time varying features characteristic of even longer wavelengths, which originate within the outer core. An inflection point, or change of slope, in the geomagnetic power spectrum (Figure M6) can be seen at degree 13 and is a manifestation of the relatively sharp transition from core‐dominated processes to lithospheric‐dominated processes. Long‐wavelength anomalies (Figure M7a/Plate 5c) are most easily recognized from near‐Earth satellites at altitudes of 350–750 km, and these altitudes define the shortest wavelengths traditionally associated with such geomagnetic features. The lithospheric origin of these features was firmly established by comparison with the marine magnetic record of seafloor spreading in the North Atlantic (LaBrecque and Raymond, 1985). Virtually identical features have now been...
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