References in mgd77magref and new coefficients

Q&A
1

In
https://docs.generic-mapping-tools.org/latest/supplements/mgd77/mgd77magref.html

references:
http://denali.gsfc.nasa.gov/cm/
http://www.iugg.org/IAGA/iaga_pages/pubs_prods/igrf.htm

It seems to be broken.

I think they should be:
https://web.archive.org/web/20111021003705fw_/http://core2.gsfc.nasa.gov/cm/CM4_A.html
or https://ftp.space.dtu.dk/pub/nio/CM4/
and https://www.ngdc.noaa.gov/IAGA/vmod/igrf.html

There are two new set of coefficients:
http://www.spacecenter.dk/files/magnetic-models/CM5/
http://www.spacecenter.dk/files/magnetic-models/CM6/

I want to see if I can adapt those coefficients to work with mgd77magref. But before I try, I just want to check if someone has already adapted it to work with GMT or has found another open source program that does the equivalent job.

2

I never understood if CM5 (and now CM6) are different programs or just new sets of coefficients. I once asked the author but never got a reply. As you know, we overcome the CM4 limitations by using IGRF for core model and updating ourselves (me and Michael) the ionospheric coefficients, which is not easy because they seem to change old coefficients from time to time.

The Ionospheric coefficients in your links do not look like what we have in the share/mgd77 files so I don’t know if they can be adapted, but please go ahead and try.

3

The paper (2015) says

To this end, a forward code will be made available soon, as well as sets of SH coefficients, etc., describing various magnetic and electric current fields. Those interested should contact the authors directly.

So I did, but as said, got no answer.