Geology Reference
In-Depth Information
Fig. 4.27
Tot al fiel d
intensity,
F
,intheIGRF
2010.0 field model (Finlay
et al.
2010
). Units are nT
Fig. 4.28
Magnetic
inclination,
I
,intheIGRF
2010.0 field model (Finlay
et al.
2010
). Units are deg
Fig. 4.29
Magnetic
declination,
D
,intheIGRF
2010.0 field model (Finlay
et al.
2010
). Units are deg
degree and order of the spherical harmonics,
N
,
is chosen so that the coefficients of the model are
reliably determined given the available coverage
and quality of observations. The model can be
used to predict the large scale features of the
internal field. The model is updated at intervals
of 5 years (
epochs
) to incorporate new data and is
available for the time interval since 1900.0 A.D.
To take into account of the secular variation, the
model also specifies a rate of variation of the
Gauss coefficients within each epoch. In the 11th
generation model, IGRF
11,
N
was chosen to
be 10 up to and including epoch 1995.0, and 13
for subsequent epochs, which included excellent
satellite data provided by the Ørsted and CHAMP
satellites (Finlay et al.
2010
). The latest IGRF
model is shown in Figs.
4.27
,
4.28
and
4.29
(total
field intensity, inclination, and declination). We
