Publikationsdatum:
1988-01-01
Beschreibung:
Ground measurements of the geomagnetic field contain components from external sources and associated currents induced in the Earth. Some of the external sources, namely ring, magnetotail, and boundary (Chapman-Ferraro) currents, produce relatively uniform fields in the vicinity of the Earth, which approximately parallel the dipole axis of the Earth. These fields are, in part, time-varying on a scale of a fewminutes to a few days, but as long as the solar wind blows, they must also contain a quasi-steady component with a time scale of a few tens of days to several years. We develop correction equations to take into account the time-varying part of such axially symmetric external fields using the Dst index. These equations are then applied to the inclination values Im obtained from the Project MAGNET data for the interval 1957-1966. Even after A corrections are made on the difference angle Im-Ic, where c denotes the inclination computed from internal terms only, a residual field remains. We believe this residual field to be evidence for the existence of a steady part of the field that cannot be accounted for by Dst corrections, and we estimate this residual field, assuming that it is axially symmetric. The steady field thus calculated has an equatorial value of about 40nT, which corresponds to the external sphericalharmonic coefficientg g10e the same order and positive sign. The positives ign implies the steady component in the vicinity of the Earth is direction southward. © 1988, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.
Print ISSN:
0022-1392
Thema:
Geologie und Paläontologie
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