FIGURE 2.15 USArray coverage of North America including the continental
margins of the United States and potential cooperating stations in Canada and
Mexico. SOURCE: P. Shearer, University of California, San Diego, http://
mahi.ucsd.edu/shearer/USARRAY/usarray4.html .
The current understanding of geomagnetism owes much to the geomagnetic
observatories that have been maintained (in varying numbers) over the past
century. Data from these observatories have been used to explore a wide range of
physical phenomena, from the flow in the Earth’s liquid core, to the electrical
conductivity of the solid mantle, to resonant hydromagnetic oscillations in the
plasma environment of the ionosphere. From these studies much has been
learned, not only about the geomagnetic field per se, but also about
SCIENCE OPPORTUNITIES
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