5.2.1 The internal field

a. IGRF 10 [RN.29] shall be used as the Internal Geomagnetic Field Model.

NOTE As a stand-alone model, the inputs required of the IGRF-10 are either position in geodetic coordinates, according to the reference ‘World Geodetic Service 84’ standard ellipsoid, or position in a geocentric system, with respect to the centre of the Earth and for which the reference Earth radius is 6 371,2 km. The coordinates are therefore geodetic or geocentric latitude in decimal degrees, longitude (same in both coordinate systems), altitude in km above the reference ellipsoid, or distance in km from the centre of the Earth. Time is input in decimal years, e.g. 2 007,5. It is recommended that geocentric data are used, to avoid errors or confusion in respect of the reference ellipsoid.

b. If a different model is an inherent part of a specific space environment model, then that specific geomagnetic field model shall be used.

NOTE An example is the AE8 and AP8 radiation flux / belt models (see Clause 9)

5.2.1.2 Application

a. For times in the past and in the future, IGRF-10 shall be used, in association with its secular variations.

NOTE 1 IGRF-10 and future versions contain revisions of models of earlier epochs.

NOTE 2 Beyond 5 years from the assumed epoch, the precision of the model is considerably reduced. IGRF-11 is expected to be issued for the epoch 2010, and can be used post 2010.