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Enhanced Magnetic Model (EMM2010)

Difference in declination between the EMM and WMM. Declination Comparison of WMM and EMM (larger image)

The Earth's internal magnetic field is a superposition of the field generated by the geodynamo in the liquid outer core (main field) and the field of magnetized rocks in the crust and upper mantle. The main field dominates the long wavelengths, whereas the crustal field dominates at wavelengths smaller than 2500 km.

Geomagnetic field models are conveniently represented as spherical harmonic expansions of a scalar magnetic potential. Such a model can then be evaluated at any desired location to provide the magnetic field vector, its direction, and strength. The standard World Magnetic Model uses a spherical harmonic representation to degree and order 12, resolving the magnetic field at 3000 km wavelength. In contrast, the Enhanced Magnetic Model (EMM) extends to degree and order 720, resolving magnetic anomalies down to 56 km wavelength (see comparison in the figure). The higher resolution of the EMM results in significantly improved pointing accuracy.

The EMM model was compiled from satellite, marine, aeromagnetic and ground magnetic surveys (see our acknowledgement of data providers and collaborators).

Why is this important?

Many different applications utilize Earth's magnetic field,whether for navigation, resource evaluation, or research. The magnetic field experienced at or near the Earth's surface is a combination of the main magnetic field, the relatively static crustal magnetic field, and the rapidly time-varying external magnetic field (solar origin). The better we are able to define these fields, the more accurate the results.

Acknowledgments

Changes to the code

new The Enhanced Magnetic Model is now expanded to years 2000 through 2015. To extend the model from 2010 back to 2000 the EMM's main field coefficients are replaced with the first 15 degrees of the Pomme 7 model.

How to Cite These Data:

Maus, S., An ellipsoidal harmonic representation of Earth’s lithospheric magnetic field to degree and order 720, Geochem. Geophys. Geosyst., 11, Q06015, doi: 10.1029/2010GC003026, 2010

EMM - Coefficients and Grids

File

~ Size

Release Date

Description
EMM2010_Sph_Windows_Linux.zip

24.5MB

Apr 17, 2012

Enhanced Magnetic Model (EMM2010) and software using the spherical harmonic approach for Windows and Linux environments. High CPU requirements (use the faster Mesh software for large number of points), very low RAM requirement (7.5 MB). For use with years 2000 to 2015.

EMM2010_Mesh_Windows_Linux.zip

526MB

Nov 15, 2010

Enhanced Magnetic Model (EMM2010) with software with rapid field calculation using 3D mesh interpolation for Windows and Linux environments. Low CPU requirements, High (1.4 GB) RAM requirement. Only works for years 2010-2015, for 2000-2010 please download the spherical harmonic version above.

Older versions:

      
EMM2010_Dec-15-09.zip

6MB

Dec 15, 2009

Enhanced Magnetic Model (EMM2010) with software for point and grid calculation.
EMM-720_V3p0.tar.gz

719MB

Jun 17, 2009

Enhanced Magnetic Model with software for rapid field calculation using 3D mesh interpolation.
EMM-720_V3p0_static.cof.gz

2.8 MB

Jun 17, 2009

Enhanced Magnetic Model. Spherical Harmonic Coefficients of the static internal field at 2010.0 .

EMM-720_V3p0_secvar.cof.gz

1 KB

Jun 17, 2009

Enhanced Magnetic Model. Spherical Harmonic Coefficients of the estimated secular variation 2010-2015.

EMM-06.tar.gz

2.8 MB

Nov, 2006

Software for the Enhanced Magnetic Model (EMM-06), including main field, secular variation, NGDC-720-V1 crustal field, magnetospheric field, and induced field. The package includes a simple single-point program and a thread-safe multi-processor application which can be adapted to produce large grids and time series.
       

The NGDC-720 research model preceded the Enhanced Magnetic Model. The NGDC-720 will not be updated. The archived model and coefficients are provided for software evaluation and testing purposes.