mgd77magref - Evaluate the IGRF or CM4 magnetic field models
mgd77magref [ inputfile ] [ -A[+aalt+tdate+y] ] [ -Ccm4file ] [ -DDstfile ] [ -Ef107file ] [ -Fflags ] [ -G ] [ -Sc|llow/high ] [ -V[level] ] [ -b<binary> ] [ -f<flags> ] [ -h<headers> ] [ -:[i|o] ]
Note: No space is allowed between the option flag and the associated arguments.
mgd77magref will evaluate the IGRF or the CM4 geomagnetic models at the specified locations and times.
None.
Selects output items; flags is a string made up of one or more of these characters:
r means output all input columns before adding the items below
t means list total field (nT).
h means list horizontal field (nT).
x means list X component (nT, positive north).
y means list Y component (nT, positive east).
z means list Z component (nT, positive down).
d means list declination (deg, clockwise from north).
i means list inclination (deg, positive down).
Append one or more number to indicate the requested field contribution(s):
0 means IGRF field (no combinations allowed)
1 means CM4 Core field
2 means CM4 Lithospheric field
3 means CM4 Primary Magnetospheric field
4 means CM4 Induced Magnetospheric field
5 means CM4 Primary ionospheric field
6 means CM4 Induced ionospheric field
7 means CM4 Toroidal field
9 means Core field from IGRF and other contributions from CM4. DO NOT USE BOTH 0 AND 9.
Appending several numbers (1-7) will add up the different contributions. For example -Ft/12 computes the total field due to Core and Lithospheric sources. Two special cases are allowed, which mix which Core field from IGRF and other sources from CM4. -Ft/934 computes Core field due to IGRF plus terms 3 and 4 from CM4 (but you can add others). -Ft/934 the same as above but output the field components. The data is written out in the order they appear in flags [Default is -Frthxyzdi/1].
Computes J field vectors from certain external sources.
r means output all input columns before adding the items below (all in Ampers/m).
t means list magnitude field.
x means list X component.
y means list Y component.
z means list Z or current function Psi.
Append a number to indicate the requested J contribution:
1 means Induced Magnetospheric field.
2 means Primary ionospheric field.
3 means Induced ionospheric field.
4 means Poloidal field.
If binary input files are used then absolute time are stored as time relative to the selected epoch. However, since the epoch used is not stored in the data files there can be problems decoding the correct time. The mgd77 supplement uses the Unix time system as its default; thus you should make sure that binary data files with time uses the same system (see the GMT default TIME_SYSTEM).
To get the CM4 Total field, Declination and Inclination due to all but lithospheric and toroidal field at a one point location and decimal time 2000.0, try
echo -28 38 0 2000.0 | gmt mgd77magref -A+y -Ftdi/13456
To do the same as above but at noon (Universal Time) of first May 2001, try
echo -28 38 0 2001-05-01T12:00:00 | gmt mgd77magref -Ftdi/13456
gmt, mgd77info, mgd77list, mgd77manage, mgd77track, gmt.conf
Comprehensive Modeling of the Geomagnetic Field, see http://denali.gsfc.nasa.gov/cm/
The International Geomagnetic Reference Field (IGRF), see http://www.iugg.org/IAGA/iaga_pages/pubs_prods/igrf.htm