FILENAME: igrfgen2.dat.
Coefficients of 2nd generation IGRF. Adopted at 16th General Assembly of IUGG,
Grenoble, 1975 August-September.  
REFERENCE: IAGA Division I Study Group on Geomagnetic Reference Fields, 1975.
"International Geomagnetic Reference Field 1975", J. Geomagn. Geoelectr., 27,
437-439.
The coefficients for each constituent model, as given below, are in the order
g01, g11, h11, g02, g12, h12, g22, h22, ....., gn*n*, hn*n*.
Main-field models for 1965 (same as 1st generation IGRF) & 1975.0;
secular-variation model for 1975-80 (all to n* = 8)
PROGRAM: the Fortran subroutine MAGSYN contains the 1975.0 main-field 
coefficients and the secular-variation coefficients of this 2nd generation 
IGRF, and the secular-variation coefficients of the original (1st generation) 
IGRF.  This is entirely equivalent to the 2nd generation IGRF as defined here.  
A listing of the source code of MAGSYN has been published in Malin, S. R. C. &
Barraclough, D. R., 1981.  "An algorithm for synthesizing the geomagnetic
field", Computers & Geosciences, 7, 401-405.
Main-field model for 1965.0:
 -30339.  -2123.   5758.  -1654.   2994.  -2006.   1567.    130.   1297.  -2036.
   -403.   1289.    242.    843.   -176.    958.    805.    149.    492.   -280.
   -392.      8.    256.   -265.   -223.    357.     16.    246.    125.    -26.
   -123.   -161.   -107.    -51.     77.     47.     60.    -14.      4.    106.
   -229.     68.      3.    -32.     -4.    -10.   -112.    -13.     71.    -54.
    -57.      0.    -27.     12.     -8.    -25.      9.     -9.     23.     13.
    -19.     -2.    -17.     10.      9.      3.     -3.    -13.    -12.      5.
     -4.    -17.      7.      4.     -5.     22.     12.     -3.      6.    -16.
Main-field model for 1975.0:
 -30186.  -2036.   5735.  -1898.   2997.  -2124.   1551.    -37.   1299.  -2144.
   -361.   1296.    249.    805.   -253.    951.    807.    148.    462.   -264.
   -393.     37.    235.   -307.   -204.    368.     39.    275.    142.    -20.
   -147.   -161.    -99.    -38.     74.     46.     57.    -23.     15.    102.
   -210.     88.     -1.    -43.     -8.     -9.   -114.     -4.     66.    -57.
    -68.     -7.    -24.      7.     -4.    -22.     11.     -9.     27.     11.
    -17.     -8.    -14.     11.     13.      4.      3.    -15.    -12.      2.
     -4.    -19.      6.      1.     -2.     18.      9.     -6.      1.    -19.
Secular-variation model for 1975-80:
    25.6    10.0   -10.2   -24.9     0.7    -3.0     4.3   -18.9    -3.8   -10.4
     6.9    -4.1     2.5    -4.2    -5.0    -0.2    -2.0     5.0    -3.9     0.8
    -2.1     1.7    -3.1    -1.0     0.3    -0.7     1.2     1.1     2.3    -1.6
    -2.0    -0.5     1.3     1.0     1.1     0.2     0.5    -0.5     2.0    -0.1
     2.8    -0.2     0.0    -1.3     0.9     0.7    -0.1     1.7     0.0     0.0
    -1.4     0.0    -0.1     0.6     0.3     0.9     0.3     0.3    -0.7     0.3
     0.1    -0.5     0.8     0.2     0.3    -0.2     0.0    -0.4     0.2    -0.2
    -0.4    -0.3    -0.3     0.4     0.6    -0.3    -0.3    -0.6    -0.1     0.3