Abstract
Three new geomagnetic observatories have been established recently around the South Atlantic geomagnetic Anomaly by GeoForschungsZentrum Potsdam(GFZ), Germany, in collaboration with other institutions. In Bolivia, the collaboration is with Universidad Mayor de San Andres, LaPaz, while Hermanus Magnetic Observatory (HMO) in South Africa has assisted with a new observatory in Namibia. The third observatory was set up on the island of St. Helena with logistical support from the IDA seismological network, University of California at San Diego, USA. All these observatories are operated remotely with a minimum amount of building infrastructure and without permanent staff. People living nearby have been trained to carry out the required absolute measurements for a few hours per week. In this paper we report on our experiences, challenges and solutions in setting up nearly automated observatories in remote locations in order to obtain high quality geomagnetic data. These new data, complemented by annual repeat station surveys in southern Africa, will provide valuable geomagnetic field information on the South Atlantic Anomaly changes in this area of extremely rapid decrease of field intensity.
Highlights
The Earth’s magnetic field has a distinct dipolar structure
60% of the field strength at comparable latitudes, is known as the South Atlantic Anomaly (SAA, fig. 1a). It is caused by an increasing patch of opposite magnetic flux compared to the dipole direction at the core-mantle boundary (Bloxham and Gubbins, 1985) and its centre has moved from southern Africa to South America over the last 300 years (Mandea et al, 2007)
Traditional geomagnetic observatories are in most cases situated on relatively large properties, with several staff members working in an office building and minimum two extra buildings to record the variations and to carry out the absolute measurements, far enough away to avoid disturbances
Summary
The Earth’s magnetic field has a distinct dipolar structure. More than 90% of the field strength at the Earth’s surface can be attributed to an axial dipole currently tilted by approximately 10.2° with respect to the rotation axis. Discrete annual or bi-annual vector field measurements at additional locations, were carried out on a relatively sparse network consisting of 8 well-distributed stations in South Africa, Namibia and Botswana from 2000 to 2004 by Hermanus Magnetic Observatory (HMO). Over the last few years we have further improved monitoring the geomagnetic field around the southern Atlantic by setting up three new, remotely operated observatories They are located in Bolivia, Namibia and on the island of St. Helena. Due to a lack of an immediate possibility to increase the number of observatories even further we increased the number of annually visited repeat stations in South Africa, Namibia and Botswana This and the new Namibian observatory are collaborative efforts of GeoForschungsZentrum Potsdam (GFZ) and Hermanus Magnetic Observatory (HMO). The availability of the new data is described together with our conclusions
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