mgd77magref(1) GMT mgd77magref(1)
NAME
mgd77magref - Evaluate the IGRF or CM4 magnetic field models
SYNOPSIS
mgd77magref [ inputfile ] [ -A[+aalt+tdate+y] ] [ -Ccm4file ] [
-DDstfile ] [ -Ef107file ] [ -Fflags ] [ -G ] [ -Sc|llow/high ] [
-V[level] ] [ -bbinary ] [ -fflags ] [ -hheaders ] [ -:[i|o] ]
Note: No space is allowed between the option flag and the associated
arguments.
DESCRIPTION
mgd77magref will evaluate the IGRF or the CM4 geomagnetic models at the
specified locations and times.
REQUIRED ARGUMENTS
None.
OPTIONAL ARGUMENTS
inputfile
Contains the moments in space-time where we want to evaluate the
magnetic reference field. The first two columns must contain
longitude and latitude (however, see -: for latitude and longi-
tude instead). Normally, the third and fourth columns must con-
tain altitude (in km) and time, respectively, but if one or both
of these are constant for all records they can be supplied via
the -A option instead and are thus not expected in the input
file. If no input file is given we read stdin. A note about
the CM4 validity domain. The core field of CM4 is valid from
1960-2002.5 but the ionospheric and magnetospheric fields are
computed after the Dst and F10.7 coefficient files. We extended
here those coefficient files up to 2006, which means that one
can compute external contributions up until 2006 but the Secular
Variation will be biased (non reliable). New indices files may
be retrieved from from:ftp://ftp.ngdc.noaa.gov/STP/GEOMAG-
NETIC_DATA/INDICES/DST/ (the Dst coefficients) and
http://umbra.nascom.nasa.gov/sdb/yohkoh/ys_dbase/indices_flux_raw/Penticton_Absolute/monthly/MONTHPLT.ABS
(The F10.7 index file is a MONTHPLT.ABS). NOTE: since the Dst
files in the a|/DST/ directory are still only up to 2006, for
GMT4.5.3 and after we extended the Dst until August 2009 by
reformatting the data in the preliminary file
Est_Ist_index_0_mean.pli, which is at
ftp://ftp.ngdc.noaa.gov/STP/GEOMAGNETIC_DATA/INDICES/EST_IST/.
But since this site is now also outdated, we now get the DST
indices from http://wdc.kugi.kyoto-u.ac.jp/dstae/index.html How-
ever, for the most recent dates those indices are aQuick Looka
(the best are the aDefinitivea type). Because the F10.7 from
the MONTHPLT.ABS file mentioned above are apparently no being
updated, we found another place where they are, which is:
ftp://ftp.ngdc.noaa.gov/STP/space-weather/solar-data/solar-features/
solar-radio/noontime-flux/penticton/penticton_absolute/listings/
listing_drao_noontime-flux-absolute_monthly.txt
-A[+aalt+tdate+y]
Adjusts how the input record is interpreted. Append +a to set a
fixed altitude (in km) that should apply to all data records
[Default expects altitude to be in the 3rd column of all
records]. Append +t to set a fixed time that should apply to
all data records [Default expects time to be in the 4th column
of all records]. Finally, append +y to indicate that all times
are specified as decimal years [Default is ISO dateTcolck for-
mat, see TIME_EPOCH].
-Ccm4file
Specify an alternate CM4 coefficient file [umdl.CM4].
-DDstfile
Specify an alternate file with hourly means of the Dst index for
CM4 [Dst_all.wdc]. Alternatively, simply specify a single index
to apply for all records.
-Ef107file
Specify an alternate file with monthly means of absolute F10.7
solar radio flux for CM4 [F107_mon.plt]. Alternatively, simply
specify a single flux to apply for all records.
-Fflags
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 con-
tribution(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 con-
tributions. 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 out-
put the field components. The data is written out in the order
they appear in flags [Default is -Frthxyzdi/1].
-G Specifies that coordinates are geocentric [geodetic].
-L 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.
-Sclow/high
Limits the wavelengths of the core field contribution to the
band indicated by the low and high spherical harmonic order
[1/13].
-Sllow/high
Limits the wavelengths of the lithosphere field contribution to
the band indicated by the low and high spherical harmonic order
[14/65].
-V[level] (more a|)
Select verbosity level [c].
-bi[ncols][t] (more a|)
Select native binary input. [Default is 4 input columns unless
-A is used].
-bo[ncols][type] (more a|)
Select native binary output. [Default is reflected by -F].
-h[i|o][n][+c][+d][+rremark][+rtitle] (more a|)
Skip or produce header record(s).
-:[i|o] (more a|)
Swap 1st and 2nd column on input and/or output.
-^ or just -
Print a short message about the syntax of the command, then
exits (NOTE: on Windows just use -).
-+ or just +
Print an extensive usage (help) message, including the explana-
tion of any module-specific option (but not the GMT common
options), then exits.
-? or no arguments
Print a complete usage (help) message, including the explanation
of all options, then exits.
TIME SETTINGS
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).
EXAMPLES
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
SEE ALSO
gmt(1), mgd77info(1), mgd77list(1), mgd77manage(1), mgd77track(1),
gmt.conf(5)
REFERENCES
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
COPYRIGHT
2017, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
5.4.2 Jun 24, 2017 mgd77magref(1)
gmt5 5.4.2 - Generated Thu Jun 29 14:31:40 CDT 2017