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National Space Science Data Center                       Data set  MG-14G          
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NAME:  International Geomagnetic Reference Field - 10th Generation 

SOURCE:	     

Susan Macmillan
British Geological Survey
West Mains Road
Edinburgh EH9 3LA, UK
Tel: +44 131 650 0228
Fax: +44 131 668 4368
email: smac@bgs.ac.uk	

Stefan Maus
Colorado Institute for Research in the Environmental Sciences
National Geophysical Data Center
325 Broadway
Boulder, CO 80305-3328 USA
Tel: +1 303 497 6522
Fax: +1 303 497 6513

NSSDC CONTACT: 
D. Bilitza, 
GSFC/NSSDC 
code 633/Raytheon, 
Greenbelt, MD 20771, 
Fax. (301) 286-1771
bilitza@mail630.gsfc.nasa.gov

CONTENT:     
            this file                           AAREADME.DOC
	     FORTRAN source code:  
             main program (interactive driver)	 BILCAL.FOR   
             subroutines, functions             SHELLIG.FOR   
	         BILCAL user manual with examples    BILCAL.LOG   
	         All in one subroutine	 	       igrf_sub.for
		         This file includes SHELLIG.FOR and also a subroutine 
		         igrf_sub that computes IGRF parameters.

	     geomagnetic field model coefficients:
             for 1945	 DGRF45.DAT    
             for 1950	 DGRF50.DAT    
             for 1955	 DGRF55.DAT    
             for 1960	 DGRF60.DAT    
             for 1965	 DGRF65.DAT    
             for 1970	 DGRF70.DAT    
             for 1975	 DGRF75.DAT    
             for 1980	 DGRF80.DAT    
             for 1985	 DGRF85.DAT    
             for 1990	 DGRF90.DAT    
             for 1995	 DGRF95.DAT    
             for 2000	 DGRF00.DAT+    
             for 2005	 IGRF05.DAT+    
             extrapol. coeff. for 2005-2010      IGRF05S.DAT 
             
 + The original IGRF files include coefficients up to order 13. We only use 
 coefficients up to order 10 like in the earlier model generations. The full 
 set of coeffients is in files IGRF00full.DAT and DGRF05full.DAT. Use of the 
 full set requires changes to the software.
  
BRIEF DESCRIPTION:

The International Geomagnetic Reference Field (IGRF) model is the 
empirical representation of the Earth's magnetic field recommended for 
scientific use by the International Association of Geomagnetism and 
Aeronomy (IAGA). The IGRF model represents the main (core) field without 
external sources. They employ the usual spherical harmonics expansion
of the scalar potential in geocentric coordinates. The IGRF model
coefficients are based on all available data sources including geomagnetic 
measurements from observatories, ships, aircrafts and satellites. 

The model consists of coefficient sets from epoch 1945 onward in steps 
of 5 years and the first time derivatives of the coefficients for a 5-year
extrapolation into the future. During the 5-year intervals between consecutive 
models, linear interpolation is recommended. The IGRF homepage provides access
to coefficient files back to 1900. The files up to 1995 provide coefficients 
up to order 10, for 2000 and 2005 coefficients up to order 13 are provided. 
Our calculations are limited to using coefficients up to order 10 for all
files. 

In combination with the IGRF coefficient sets different subroutines have 
been used to determine the components of the magnetic field vector and the 
L-value at a given location. The NSSDC version uses the subroutines FELDG 
(magnetic field vector) and SHELLG (L shell) developed by G. Kluge at the 
European Space Operations Center (ESOC). His use of inverse cartesian co-
ordinates simplifies the computation. The IGRF subroutines were developed 
by A. Zunde of the U.S. Geological Survey (USGS). 

The program BILCAL produces tables of the geomagnetic field strength, vector 
components (B-abs., B-north, B-east, B-down, declination, inclination), 
equatorial/minimum field strength (B0), dipole moment, and L-value  in  
latitude, longitude (geodetic), altitude, or year (decimal). 

Before using the IGRF please read the 'Health Warning' at 
http://www.ngdc.noaa.gov/IAGA/wg8/igrfhw.html

AVAILABILITY:
(1) FORTRAN source code from this directory.
(2) Model parameters can be computed and plotted online on IGRFWeb at http://nssdc.gsfc.nasa.gov/space/model/ .
(3) Model homepage at http://www.ngdc.noaa.gov/IAGA/wg8/wg8.html .

REFERENCES:

Peddie, N. W., International Geomagnetic Reference Field: the third
   generation, J. Geomagn. Geoelectr. 34, 309-326, 1982.

Kluge, G., Direct computation of the magnetic shell parameter,
   Computer Phys. Communications 3, 31-35, 1972.

International Geomagnetic Reference Field Revision 1987, J. Geomag.
   Geoelectr. 39, 773-779, 1987   and    EOS Trans. 69, 559, 1988

Langel, R. A., D. R. Barraclough, D. J. Kerridge, V. P. Golovkov,
   T. J. Sabaka, and R. H. Estes, Definitive IGRF models for 1945,
   1950, 1955, and 1960, J. Geomag. Geoelectr. 40, 645-702, 1988

Langel, R. A., International Geomagnetic Reference Field, 1991 
   Revision, J. Geomag. Geoelectr. 43, 1007-1012, 1991

Barton, C.E., Revision of International Geomagnetic Reference Field
   Released, EOS Trans. 77, #16, April 16, 1996.

Barton, C.E., International Geomagnetic Reference Field: The Seventh
   Generation, J. Geom. Geoelectr. 49, 123-148, 1997.

Earth, Planets, and Space Journal, Vol. 52, No. 12, pp. 1117-1233, 2000

M. Mandea et al., International Geomagnetic Reference Field - Epoch 2000
   Revision Of The IGRF for 2000 - 2005, http://www.ngdc.noaa.gov/IAGA/wg8/igrf.html,
   26 May 2000.
 
International Geomagentic Reference Field - 2000, AGU EOS Transactions, 
   pp. 347, Aug 3, 2001
   

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National Space Science Data Center                       Data set  MG-14G
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