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12. Table of All Field Models

The ALL-IGRF.TAB file is a table of all the spherical harmonic Gauss coefficients, g and h, of the International Geomagnetic Reference Fields (IGRF) and Definitive Geomagnetic Reference Fields (DGRF) to cover the years from 1900 to 2005. This table was adopted by the Working Group 8 of IAGA Division V.

For each five-year epoch (column) the g and h Gauss coefficients (in nanotesla units) are given (in ordered rows) up to values of degree (n) 10 and order (m) 10. The SV column to the right represents the secular variation in units of nanotesla (gamma) per year and is used to extend the 2000 epoch values to the year 2005. These coefficients are used to determine the geomagnetic potential function V (from which the XYZ or HDZ field component values are derived) with the formulation

equation for computing geomagnetic potential

where a is the mean Earth radius, r is the radial distance from the center of the Earth, f is the longitude measured eastward from Greenwich, ? is the geocentric colatitude, and Pmn is the Schmidt-normalized associated Legendre polynomial of degree n and order m. The maximum number of n is N (N=10 in the table) and m is less than or equal to n.

Download this table (self-extracting zip file)

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