Geomagnetic Models and Software
NGDC-720:
September 2006 release of version 1.0 crustal magnetic
field model. A
convenient way of representing geomagnetic fields is to expand the scalar
magnetic potential into spherical harmonic functions that can
then be evaluated at any desired location to provide the magnetic field
vector, its direction, or the anomaly of the total intensity of the field.
The NGDC-720 model provides such an expansion for the crustal field from
spherical harmonic degree 16 to 720, corresponding to the waveband of
2500 km to 56 km. The degree 720 cut-off corresponds to an angular wavelength
of 30 arc minutes, providing a 15 arc minute model resolution.
 Revised on-line
calculators for the IGRF (1900-2010), DoD
WMM (2005-2010), Declination only (1900-2010), US Historic Declination (1750-2010)
IAGA Web Image Spreadsheet Tool - display and download IAGA magnetic field maps and data from 1900 - 2005. The Wist allows the user to select the number of rows (years) and columns (magnetic elements) to display. Each "cell" of the Wist displays the appropriate map for the selected year and element and links to the PDF for a higher resolution version of the map and to the data used to create the map.
The Epoch 2005-2010 Models
Because the Earth's magnetic field
is constantly changing, it is impossible to accurately predict what the field will be at
any point in the very distant future. By constantly measuring the magnetic field, we can
observe how the field is changing over a period of years. Using this information, it is
possible to create a mathematical representation of the Earth's main magnetic field and
how it is changing. Since the field changes the way it is changing, new observations must
continually be made and models generated to accurately represent the magnetic field as it
is. NGDC participates in the development and distribution of two global main-field models,
the World Magnetic Model and the International Geomagnetic Reference Field Model. The WMM
is the standard navigation model for the U.S. and U.K. Departments of Defense and NATA. The
IGRF is the international research reference model.
Note: To learn more about these models, visit the home Web sites
for the US / UK World Magnetic Model (WMM) 2005 and
IAGA IGRF-10 .
NGDC distributes two main magnetic field models, the International Association
of Geomagnetism and Aeronomy (IAGA) International Geomagnetic Reference
Field (IGRF) model and the Department of Defense (DoD) World Magnetic Model
(WMM). You can download the models for use on your own machine, or
compute magnetic field values
online from the current IGRF model. Before using the IGRF please look
at the 'Health Warning'.
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