European Space Agency

European Space Agency

Royal Belgian Institute for Aeronomy

Royal Belgian Institute for Aeronomy

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um510 - select an internal field model

subroutine  um510(kint, year, lbint, kunit, ifail)
Parameters:

  • kint [integer4,in] :: index of the geomagnetic field model [-2..4]

  • year [integer4,in] :: epoch of the geomagnetic field calculation express in year

  • lbint [character32,out] :: label of the geomagnetic field model

  • kunit [integer4,in] :: file unit for the summary table (see note of ut990()

  • ifail [integer4,out] :: error flag (see Diagnostics)

Description

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 values

kint

Field Model

Remarks

kint

Geomagnetic field model

Remarks

0

DGRF/IGRF 1900-2015

1

Jensen & Cain (1962)

fixed to epoch 1960

-1

Jensen & Cain (1962)

fixed to epoch 1960 and corrected for the SAA westward drift

2

GSFC 12/66

-2

GSFC 12/66

fixed to epoch 1970 and corrected for the SAA westward drift

3

Dipole magnetic field

4

DGRF/IGRF 1900-2015

deprecated 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.

References

  • 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

History

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. In version 2.22 and earlier, problems have been discovered in subroutine um510() when the argument kint is set to 4 (evaluation of DGRF/IGRF by the Kluge algorithm). This option is now disabled

Diagnostics

  • -51001, invalid geomagnetic field model index

  • -51002, geomagnetic field uncorrectly loaded

  • -51003, error on output device

Common Blocks

Dependencies

Called by

None

Calls

See also

Reported Bugs

None

Examples

UNILIB/tags/v3.02