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Trapped Radiation ENvironment model Development


[ Name | Synopsis | Arguments | Description | Diagnostics | Common Blocks | Dependencies | See Also | Reported Bugs | Examples ]


    Subroutine UM510 - select a geomagnetic field model


      INTEGER*4      kint, kunit, ifail
      REAL*8         year
      CHARACTER*32   lbint

      CALL UM510 (kint, year, lbint, kunit, ifail)


    Index of the geomagnetic field model (-2, -1, 0, 1, 2, 3 or 4) [in]
    Epoch of the geomagnetic field calculation expressed in year [in]
    Label of the geomagnetic field model [out]
    File unit for the summary table (see note of subroutine UT990) [in]
    Error flag (see diagnostics) [out]


    The subroutine UM510 may be used to initialize the geomagnetic field description inside the common block UC140. The kint argument allows to choose between four models as listed below.

    kint Geomagnetic field model Remarks
    0DGRF/IGRF 45-95 -
    1Jensen & Cain (1962) fixed to epoch 1960
    -1Jensen & Cain (1962) fixed to epoch 1960 and corrected for the SAA westward drift
    2GSFC 12/66 -
    -2GSFC 12/66 fixed to epoch 1970 and corrected for the SAA westward drift
    3Dipole magnetic field -
    4DGRF/IGRF 45-95 use the Kluge algorithm to evaluate the geomagnetic field

    The dipole magnetic field model is obtained from the DGRF/IGRF model by a truncation to the second order of the expansion coefficient. The year argument specifies the epoch used to evaluate the geomagnetic field model. The Jensen & Cain model does not depend on time and has its epoch fixed to 1960. When kunit is greater than zero, a summary table is written by the subroutine. As result, the lbint argument contains a string with the label of the selected internal magnetic field model.

    The Jensen & Cain model has been used to produce the NASA trapped radiation belt models AP-8 MIN, AE-8 MIN and AE-8 MAX. The GSFC 12/66 model, updated to 1970, has been used to generate AP-8 MAX model. Since these NASA models were built more than twenty years ago, the location of the South Atlantic Anomaly (SAA) has shifted considerably to the West compared to its location predicted by the two old magnetic field models, due to the secular variation of the geomagnetic field distribution. When the kint argument is set to -1 or -2, the effect of this drift will be compensated by applying an eastward rotation to the geographic coordinates before the evaluation of the internal magnetic field.


  • Cain, J.C., Hendricks, S.J., Langel, R.A. and Hudson, W.V., A proposed model for the international geomagnetic reference field-1965, J.Geomag.Geoelectr. 19 (1967) 335-355
  • Heynderickx, D., Comparison between methods to compensate for the secular motion of the south atlantic anomaly, Aeronomica Acta 385 (1994)
  • Jensen, D.C. and Cain, J.C., An interim geomagnetic field, JGR 67 (1962) 3568


    In version 2.02 and earlier the string returned by argument lbint is not correctly copied in the argument mint.label of common block UC140.


    -51001, invalid geomagnetic field model index
    -51002, geomagnetic field uncorrectly loaded
    -51003, error on output device

Common Blocks

    UC140, magnetic field description
    UC160, general constants


Called by



    UM511, set the Jensen & Cain 1960 model coefficients
    UM512, set the GSFC 12/66 model coefficients
    UM513, set the DGRF/IGRF model coefficients
    UM517, transform from Schmidt to Kluge normalisation

See also

    UM520, select an external magnetic field model
    UM530, evaluate the magnetic field vector

Reported Bugs

  • Problems have been discovered in subroutine UM510 when the argument kint is set to 4 (evaluation of DGRF/IGRF by the Kluge algorithm).


    #1, evaluation of the magnetic field vector
    #2, evaluation of the (B, L) coordinates
    #3, evaluation of the third invariant
    #4, search the point with the lowest altitude on a magnetic drift shell
    #5, namelist to initialize UNILIB
    #7, iso-contour of the shell parameter
    G.06 How to start using the UNILIB library ?
    T.03 How to customize the magnetic field model used by the library ?
    T.04 Why are Roederer's L* and McIlwain's L parameters different ?