Observations and Models of the Long-Term Evolution of Earth's Magnetic Field | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Observations and Models of the Long-Term Evolution of Earth's Magnetic Field

Type de publication:

Journal Article

Source:

Space Science Reviews, Volume 155, Ticket 1-4, p.337-370 (2010)

ISBN:

0038-6308

Numéro d'accès:

ISI:000284427000012

URL:

http://www.springerlink.com/content/c11323706hx86099/

Mots-clés:

UMR 7154 ; Dynamique des fluides géologiques ; Keywords Geomagnetism - Paleomagnetism - Paleointensity - Geodynamo - Core Processes - Core-Mantle Interactions

Résumé:

<p>The geomagnetic signal contains an enormous temporal range-from geomagnetic jerks on time scales of less than a year to the evolution of Earth's dipole moment over billions of years. This review compares observations and numerical models of the long-term range of that signal, for periods much larger than the typical overturn time of Earth's core. On time scales of 10(5)-10(9) years, the geomagnetic field reveals the control of mantle thermodynamic conditions on core dynamics. We first briefly describe the general formalism of numerical dynamo simulations and available paleomagnetic data sets that provide insight into paleofield behavior. Models for the morphology of the time-averaged geomagnetic field over the last 5 million years are presented, with emphasis on the possible departures from the geocentric axial dipole hypothesis and interpretations in terms of core dynamics. We discuss the power spectrum of the dipole moment, as it is a well-constrained aspect of the geomagnetic field on the million year time scale. We then summarize paleosecular variation and intensity over the past 200 million years, with emphasis on the possible dynamical causes for the occurrence of superchrons. Finally, we highlight the geological evolution of the geodynamo in light of the oldest paleomagnetic records available. A summary is given in the form of a tentative classification of well-constrained observations and robust numerical modeling results.</p>

Notes:

Aubert, Julien Tarduno, John A. Johnson, Catherine L. Workshop on Space Science Research of International Space Science Institute (ISSI) MAR 09-13, 2009 Bern, SWITZERLAND