Jeffrey J. Love
2008
<div class="NLM_paragraph">For centuries, navigators of the world’s oceans have been familiar with an<span> </span>effect<span> </span>of Earth’s<span> </span>magnetic field:<span> </span>It imparts a directional preference to the needle of a compass. Although in some settings magnetic orientation remains important, the modern science of<span> </span>geomagnetismhas emerged from its romantic nautical origins and developed into a subject of great depth and diversity. The<span> </span>geomagnetic<span> </span>field is used to explore the<span> </span>dynamics<span> </span>of Earth’s interior and its surrounding space environment, and<span> </span>geomagnetic<span> </span>data are used for<span> </span>geophysical<span> </span>mapping, mineral<span> </span>exploration,<span> </span>risk mitigation, and other practical applications. A global distribution of ground-based magnetic<span> </span>observatories<span> </span>supports those pursuits by providing accurate records of the magnetic-field direction and intensity at fixed locations and over long periods of time.</div><div class="NLM_paragraph"><br data-mce-bogus="1"></div><div class="NLM_paragraph">Magnetic<span> </span>observatories<span> </span>were first established in the early<span> </span>19th century<span> </span>in response to the influence of Alexander von Humboldt and Carl Friedrich Gauss. Since then, magnetic<span> </span>measurement<span> </span>has advanced significantly, progressing from simple visual readings of magnetic survey instruments to include automatic photographic<span> </span>measurement<span> </span>and modern electronic acquisition. To satisfy the needs of the scientific community,<span> </span>observatories<span> </span>are being upgraded to collect data that meet ever more stringent standards, to achieve higher acquisition frequencies, and to disseminate data in real time.</div><div class="NLM_paragraph"><br data-mce-bogus="1"></div><div class="NLM_paragraph">To appreciate why data from magnetic<span> </span>observatories<span> </span>can be used for so many purposes, one needs only to recall that the<span> </span>geomagnetic<span> </span>field is a continuum, connecting the different parts of Earth to each other and to nearby space. Beneath our feet and above our heads,<span> </span>electric currents<span> </span>generate<span> </span>magnetic fields<span> </span>that contribute to the totality of the<span> </span>geomagnetic<span> </span>field<span> </span>measured<span> </span>at an<span> </span>observatory<span> </span>on Earth’s<span> </span>surface.<span> </span>The many physical processes that operate in each<span> </span>geophysical<span> </span>domain give rise to a complicated field that exhibits a wide variety of time-dependent behavior. <span class="ref-lnk"></span>In this article I review the status of the global community of magnetic<span> </span>observatories,<span> </span>show how Earth and space can be monitored for purposes of scientific understanding and practical application, and highlight the role played by magnetic<span> </span>observatories<span> </span>in the history of<span> </span>geomagnetism<span> </span>research.</div>
application/pdf
10.1063/1.2883907
en
American Institute of Physics
Magnetic monitoring of earth and space
article