Analyzing the Earth’s magnetic field: building the World Digital Magnetic Anomaly Map

A detailed global map of magnetic field recorded by continents and oceans.

(Guest post by Hirokuni Oda of Earth, Planets and Space)

The World Digital Anomaly Map (WDMAM) is a worldwide compilation of near-surface magnetic data. A candidate for the second version of the WDMAM and its characteristics are presented in the recent article published in Earth, Planets and Space.

This second version was evaluated by a group of independent reviewers and has now been adopted as the official second version of the WDMAM during the 26th general assembly of the International Union of Geodesy and Geomagnetism.

A global magnetic field model of the lithosphere (the solid outer section of the Earth) contribution has been parametrized by spherical harmonics up to degree and order 800. The model information content has been evaluated by computing local spectra.

Further, the compatibility of the anomaly field obtained for the WDMAM with induced magnetization is examined by comparison with the main field strength.

These studies allowed an analysis of the compilation in terms of strength and wavelength. They confirm the remarkably smooth and weak contribution of the magnetic field generated in the lithosphere over Western Europe possibly extending to the Northern African continent.

However, a global analysis remains difficult to complete due to the sparseness of good quality data over a very large area.

The WDMAM and related information including all the contributors can be found here.

Summarized by Hirokuni Oda

from the articles on WDMAM

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