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Possibly incorrect Magnetic Local Time after 2015-01-01T00:00:00Z. #4

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pacesm opened this issue Apr 10, 2018 · 3 comments
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@pacesm
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pacesm commented Apr 10, 2018

When running the the quasi dipole coordinates evaluation for dates after following warning message appears:

COFRM:  DATE 2015.139 is after the last recommended for extrapolation (2015.0)

The message is generated from the Fortran code and it is only visible when running the evaluation in console.

The error is produced by the COFRM subroutine (line 780, appex.f90). This subroutine contains embedded IGRF model coefficients whose validity ends by 2015-01-01T00:00:00Z.

The extrapolation after this date gives likely incorrect results.
The criticality of this issue ("How much incorrect the results are?") needs to be assessed.

@pacesm
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pacesm commented Apr 10, 2018

UPDATE:

Closer investigation revealed that the COFRM subroutine is used only to get the coordinates of the North Geomagnetic Pole during the Magnetic Local Time calculation.

That means that the evaluation of the Quasi-Dipole Coordinates is correct.

It is technically possible to remove the dependency on the embedded outdated IGRF model and calculate the North Geomagnetic Pole from the IGRF12 model already included in the Python package.

@pacesm pacesm changed the title Possibly incorrect Quasi-Dipole Coordinates after 2015-01-01T00:00:00Z. Possibly incorrect Magnetic Local Time after 2015-01-01T00:00:00Z. Apr 24, 2018
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pacesm commented Jun 13, 2018

Following figure shows the deviations of the magnetic local time calculated from the outdated embedded IGRF11 model in the COFRM subroutine and a reference values calculated from the current IRGF12 model.

mlt_deviation_igrf11

The minor deviations before 2015 is likely caused by #10.

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pacesm commented Jan 20, 2020

The MLT deviation got further aggravated with the release of the IGRF-13 model.
qdipole-0 2 0_MLT_vs_IGRF11_IGRF12_IGRF13

The embedded IGRF coefficients in the COFRM subroutine were updated in 05efd29 and the new qdipole-0.3.0 is calculating the MLT values using the latest IGRF-13 model coefficients.

qdipole-0 3 0_MLT_vs_IGRF13

@pacesm pacesm closed this as completed Jan 20, 2020
@pacesm pacesm mentioned this issue Jan 20, 2020
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