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| Formato: | Artículo científico |
| Lenguaje: | en |
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Universidad Nacional Autónoma de México
2000
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| Acceso en línea: | https://www.redalyc.org/articulo.oa?id=56839403 |
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- Secular change in the location of the magnetic dip equator in the twentieth century G. K. Rangarajan L. M. Barreto Ciencias de la Tierra Dip equator westward drift magnetic center secular variation South Atlantic magnetic anomaly Using the spherical harmonic coefficients defining the International Geomagnetic Reference Field Models for the 21 epochs1900 to 2000, the geographic locations of the dip equator in different longitudes were computed. It is shown that the migratorytrends in the dip equator are widely different in the American, African and Indian sectors.The largest change is seen over 30°W to40°W while there is practically no secular movement over 100 years in the 30°E longitude. It is seen that the geographic longitudeof the dip equator farthest away from the geographic equator in the American sector shows a westward migration at the rate of~0.2°/year which compares favorably with the average westward drift of the non-dipolar field discussed in the literature. Thedistance between the magnetic center of the eccentric dipole and the Earths center, the South Atlantic Geomagnetic Anomaly(SAGA) center and the migration of the local minimum of the dip equatorial longitude in the American center are all linearlyrelated. In addition, the westward drift in the agonic line over the geographic equator in the American sector, indicative of thecontributions from non-dipolar terms, is also linearly related to the three parameters. As the observed location of the dip equatorin the American sector closely matches the model-based one, it is suggested that identification of the geographic longitude of thedip equator in the American zone based on a survey over a small area can provide useful information on several other parametersof the westward drift of the geomagnetic field. 2000 artículo científico 0016-7169 https://www.redalyc.org/articulo.oa?id=56839403 en http://www.redalyc.org/revista.oa?id=568 Geofísica Internacional application/pdf Universidad Nacional Autónoma de México Geofísica Internacional (México) Num.4 Vol.39