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9 - Spatial and Temporal Changes of the Geomagnetic Field

Insights from Forward and Inverse Core Field Models

from Part III - Spatial and Temporal Variations of the Geomagnetic Field

Published online by Cambridge University Press:  25 October 2019

By
Nicolas Gillet
Edited by
Mioara Mandea ,
Monika Korte ,
Andrew Yau  and
Eduard Petrovsky
Mioara Mandea
Affiliation:
Centre National d'études Spatiales, France
Monika Korte
Affiliation:
GeoforschungsZentrum, Helmholtz-Zentrum, Potsdam
Andrew Yau
Affiliation:
University of Calgary
Eduard Petrovsky
Affiliation:
Academy of Sciences of the Czech Republic, Prague
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Summary

Observational constraints on geomagnetic field changes from interannual to millenial periods are reviewed, and the current resolution of field models (covering archeological to satellite eras) is discussed. With the perspective of data assimilation, emphasis is put on uncertainties entaching Gauss coefficients, and on the statistical properties of ground-based records. These latter potentially call for leaving behind the notion of geomagnetic jerks. The accuracy at which we recover interannual changes also requires considering with caution the apparent periodiObservational constraints on geomagnetic field changes from interannual to millenial periods are reviewed, and the current resolution of field models (covering archeological to satellite eras) is discussed. With the perspective of data assimilation, emphasis is put on uncertainties entaching Gauss coefficients, and on the statistical properties of ground-based records. These latter potentially call for leaving behind the notion of geomagnetic jerks. The accuracy at which we recover interannual changes also requires considering with caution the apparent periodicity seen in the secular acceleration from satellite data. I then address the interpretation of recorded magnetic fluctuations in terms of core dynamics, highlighting the need for models that allow (or pre-suppose) a magnetic energy orders of magnitudes larger than the kinetic energy at large length-scales, a target for future numerical simulations of the geodynamo. I finally recall the first attempts at implementing geomagnetic data assimilation algorithms.city seen in the secular acceleration from satellite data. I then address the interpretation of recorded magnetic fluctuations in terms of core dynamics, highlighting the need for models that allow (or pre-suppose) a magnetic energy orders of magnitudes larger than the kinetic energy at large length-scales, a target for future numerical simulations of the geodynamo. I finally recall the first attempts at implementing geomagnetic data assimilation algorithms.

Keywords

geomagnetic secular variationgeodynamo simulationsinverse problemdata assimilationEarth’s core dynamics
Type
Chapter
Information
Geomagnetism, Aeronomy and Space Weather
A Journey from the Earth's Core to the Sun
 , pp. 115 - 132
Publisher: Cambridge University Press
Print publication year: 2019

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