Periods of extreme geomagnetic change such as geomagnetic excursions have frequently occurred throughout geological time. Characterizing their behaviour is essential for a full understanding of the geodynamo and the interaction of Earth's magnetic field and the space environment.

We model the global behaviour of Earth’s magnetic field between 10 and 50 ka using palaeomagnetic data. During this time the geomagnetic field showed significant variability in direction and intensity, including two well documented excursions: Laschamp and Mono Lake. No model currently exists that spans the total length of this time period, yet this period could provide great insights into the geodynamo. The ultimate goal of the project is to synthesize the results from our empirical modelling with those from numerical dynamo simulations, so that a deeper physical understanding of geodynamo processes can be gained.

We first compile all sedimentary and volcanic palaeomagnetic data coupled with geochronological data spanning this period in the GEOMAGIA.v3 database. This data is added to a community available database along with all rock magnetic and sedimentological metadata. This allows a detailed assessment of the data used in the modelling. Low quality palaeomagnetic data and erroneous age models may distort geomagnetic field structures generated by our new model and it is a key objective of this study to assess the fidelity of the palaeomagnetic and chronological data included in the modeling.

Using this data we then construct a temporally continuous global spherical harmonic geomagnetic field model through a regularized least squares inversion of the data using spherical harmonics in space and cubic B splines in time. This model enables assessment of the geomagnetic at the core-mantle boundary, the Earth’s surface and at elevated altitudes. Our key scientific objective is to determine where excursions fit into the spectrum of geomagnetic field variations and how the geodynamo processes that generate excursions differ from those that produce secular variation and reversals.

Time Frame

• 2014 - 2019

Funding

• DFG within SPP 1488, “Planetary Magnetism”

Principal Investigator

• Monika Korte (GFZ Potsdam)

Personnel

• Maxwell Brown

Project Website

• http://www.planetmag.de/index.php?site=interiors

Research Unit

• RU1 (Globale Prozesse)

Publications

• Brown, M., Korte, M. (2016): A simple model for geomagnetic field excursions and inferences for palaeomagnetic observations. - Physics of the Earth and Planetary Interiors, 254, p. 1-11.
• Brown, M., Donadini, F., Korte, M., Nilsson, A., Korhonen, K., Lodge, A., Lengyel, S. N., Constable, C. G. (2015):GEOMAGIA50.v3: 1. general structure and modifications to the archeological and volcanic database. - Earth Planets and Space, 67.
• Brown, M., Donadini, F., Nilsson, A., Panovska, S., Frank, U., Korhonen, K., Schuberth, M., Korte, M., Constable, C. G. (2015): GEOMAGIA50.v3: 2. A new paleomagnetic database for lake and marine sediments. - Earth Planets and Space, 67, 1.
• Korte, M., M. Brown, U. Frank, R. Senftleben and N. Nowaczyk (2017): Global geomagnetic field reconstructions from centuries to excursions. In Magnetic Fields in the Solar System, edited by H. Lühr, J. Wicht, S. Gilder, M. Holschneider, Astrophysics and Space Science Library 448, DOI 10.1007/978-3-319-64292-5_3, Springer
• Brown, M.C., Korte, M., Wardinski, I. & Holme, R. The behaviour of the Laschamp geomagnetic field excursion from a global model based on sediment records, Kochi Core Center, Kochi University, Japan, 30th May 2017.
• Brown, M., Korte, M., Wardinski, I. (2016): The global character of excursions: Insights from empirical and dynamo models, (Geophysical Research Abstracts, Vol. 18, EGU2016-3080-1, 2016), General Assembly European Geosciences Union (Vienna, Austria 2016).
• Korte, M., Wardinski, I., Brown, M. (2016): Global characteristics of geomagnetic excursions as seen in global empirical models and a numerical dynamo simulation - Abstracts, AGU 2016 Fall Meeting (San Francisco, USA 2016).
• Korte, M., Brown, M., Wardinski, I. (2016): Global view on the Laschamp geomagnetic field excursion - Abstract Book, 13th Symposium on the Study of the Earth's Deep Interior - SEDI 2016 (Nantes, France 2016).
• Wardinski, I., Korte, M. & Brown, M. C., Characteristics and interpretations of simulated geomagnetic field reversals, The 15th Symposium of SEDI, Study of the Earth's Deep Interior, Nantes, France, 24th-29th July 2016.
• Brown, M. C., Donadini, F., Nilsson, A., Korte, M., Panovska, S., Frank, U., Korhonen, K., Lodge, A., Lengyel, S. N., Schuberth, M. & Constable, C. G. Version 3 of the GEOMAGIA50 paleomagnetic database, American Geophysical Union Fall Meeting, San Francisco, 14th December, 2015.
• Brown, M. C., Korte, M. & Wardinski, I. Paleomagnetic interpretations of reversals and excursions in numerical dynamo simulations, American Geophysical Union Fall Meeting, San Francisco, 15th December, 2015.