1MGD77MAGREF(1) Generic Mapping Tools MGD77MAGREF(1)
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6 mgd77magref - Evaluate the IGRF or CM4 magnetic field models
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9 mgd77magref [ inputfile ] [ -A[+aalt+tdate+y] ] [ -Ccm4file ] [ -DDst‐
10 file ] [ -Ef107file ] [ -Fflags ] [ -G ] [ -H[i][nrec] ] [
11 -Sc|llow/high ] [ -V ] [ -:[i|o] ] [ -b[i|o][s|S|d|D[ncol]|c[var1/...]]
12 ] [ -f[i|o]colinfo ] [ -m[i|o][flag] ]
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15 mgd77magref will evaluate the IGRF or the CM4 geomagnetic models at the
16 specified locations and times.
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19 No space between the option flag and the associated arguments.
20 inputfile
22 Contains the moments in space-time where we want to evaluate the
23 magnetic reference field. The first two columns must contain
24 longitude and latitude (however, see -: for latitude and longi‐
25 tude instead). Normally, the third and fourth columns must con‐
26 tain altitude (in km) and time, respectively, but if one or both
27 of these are constant for all records they can be supplied via
28 the -A option instead and are thus not expected in the input
29 file. If no input file is given we read stdin. A note about the
30 CM4 validity domain. The core field of CM4 is valid from
31 1960-2002.5 but the ionospheric and magnetospheric fields are
32 computed after the Dst and F10.7 coefficient files. We extended
33 here those coefficient files up to 2007, which means that one
34 can compute external contributions up until 2007 but the Secular
35 Variation will be biased (non reliable). New indices files may
36 be retrieved from:ftp://ftp.ngdc.noaa.gov/STP/GEOMAG‐
37 NETIC_DATA/INDICES/DST/ (the Dst coefficients) and
38 ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_RADIO/FLUX/ (The
39 F10.7 index file is a MONTHPLT.ABS). NOTE: since the Dst files
40 in the .../DST/ directory are still only up to 2007, for
41 GMT4.5.3 we extended the Dst till April 2010 by reformating the
42 data in the preliminary file Est_Ist_index_0_mean.pli, which is
43 at ftp://ftp.ngdc.noaa.gov/STP/GEOMAGNETIC_DATA/INDICES/EST_IST/
44 -A Adjusts how the input record is interpreted. Append +a to set a
46 fixed altitude (in km) that should apply to all data records
47 [Default expects altitude to be in the 3rd column of all
48 records]. Append +t to set a fixed time that should apply to
49 all data records [Default expects time to be in the 4th column
50 of all records]. Finally, append +y to indicate that all times
51 are specified as decimal years [Default is ISO dateTcolck for‐
52 mat].
53 -C Specify an alternate CM4 coefficient file [umdl.CM4].
55 -D Specify an alternate file with hourly means of the Dst index for
57 CM4 [Dst_all.wdc]. Alternatively, simply specify a single index
58 to apply for all records.
59 -E Specify an alternate file with monthly means of absolute F10.7
61 solar radio flux for CM4 [F107_mon.plt]. Alternatively, simply
62 specify a single flux to apply for all records.
63 -F Selects output items; flags is a string made up of one or more
65 of these characters:
66 r means output all input columns before adding the items below
67 (all in nTesla).
68 t means list total field.
69 h means list horizontal field.
70 x means list X component.
71 y means list Y component.
72 z means list Z component.
73 d means list declination.
74 i means list inclination.
75 Append one or more number to indicate the requested field con‐
76 tribution(s):
77 0 means IGRF field (no combinations allowed)
78 1 means Core field
79 2 means Lithospheric
80 3 Primary Magnetospheric field
81 4 Induced Magnetospheric field
82 5 Primary ionospheric field
83 6 Induced ionospheric field
84 7 Toroidal field
85 9 means Core field from IGRF and other contributions from CM4.
86 DO NOT USE BOTH 0 AND 9.
87 Appending several numbers (1-7) will add up the different con‐
88 tributions. For example -Ft/12 computes the total field due to
89 Core and Lithospheric sources. Two special cases are allowed,
90 wich mix which Core field from IGRF and other sources from CM4.
91 -Ft/934 computes Core field due to IGRF plus terms 3 and 4 from
92 CM4 (but you can add others). -Ft/934 the same as above but
93 output the field components. The data is written out in the
94 order they appear in flags [Default is -Frthxyzdi/1].
95 -G Specifies that coordinates are geocentric [geodetic].
97 -H Input file(s) has header record(s). If used, the default number
99 of header records is N_HEADER_RECS. Use -Hi if only input data
100 should have header records [Default will write out header
101 records if the input data have them]. Blank lines and lines
102 starting with # are always skipped.
103 -L Computes J field vectors from certain external sources.
105 r means output all input columns before adding the items below
106 (all in Ampers/m).
107 t means list magnitude field.
108 x means list X component.
109 y means list Y component.
110 z means list Z or current function Psi.
111 Append a number to indicate the requested J contribution:
112 1 means Induced Magnetospheric field.
113 2 means Primary ionospheric field.
114 3 means Induced ionospheric field.
115 4 means Poloidal field.
116 -Sc Limits the wavelengths of the core field contribution to the
118 band indicated by the low and high spherical harmonic order
119 [1/13].
120 -Sl Limits the wavelengths of the lithosphere field contribution to
122 the band indicated by the low and high spherical harmonic order
123 [14/65].
124 -V Selects verbose mode, which will send progress reports to stderr
126 [Default runs "silently"].
127 -: Toggles between (longitude,latitude) and (latitude,longitude)
129 input and/or output. [Default is (longitude,latitude)]. Append
130 i to select input only or o to select output only. [Default
131 affects both].
132 -bi Selects binary input. Append s for single precision [Default is
134 d (double)]. Uppercase S or D will force byte-swapping.
135 Optionally, append ncol, the number of columns in your binary
136 input file if it exceeds the columns needed by the program. Or
137 append c if the input file is netCDF. Optionally, append
138 var1/var2/... to specify the variables to be read. [Default is
139 4 input columns unless -A is used].
140 -bo Selects binary output. Append s for single precision [Default
142 is d (double)]. Uppercase S or D will force byte-swapping.
143 Optionally, append ncol, the number of desired columns in your
144 binary output file. [Default is reflected by -F].
145 -m Multiple segment file(s). Segments are separated by a special
147 record. For ASCII files the first character must be flag
148 [Default is '>']. For binary files all fields must be NaN and
149 -b must set the number of output columns explicitly. By default
150 the -m setting applies to both input and output. Use -mi and
151 -mo to give separate settings to input and output.
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154 If binary input files are used then absolute time are stored as time
155 relative to the selected epoch. However, since the epoch used is not
156 stored in the data files there can be problems decoding the correct
157 time. The mgd77 supplement uses the Unix time system as its default;
158 thus you should make sure that binary data files with time uses the
159 same system (see the GMT default TIME_SYSTEM).
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162 To get the CM4 Total field, Declination and Inclination due to all but
163 lithospheric and toroidal field at a one point location and decimal
164 time 2000.0, try
165 echo -28 38 0 2000.0 | mgd77magref -A+y -Ftdi/13456
167 To do the same as above but at noon (Universal Time) of first May 2001,
169 try
170 echo -28 38 0 2001-05-01T12:00:00 | mgd77magref -Ftdi/13456
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175 GMT(1) mgd77info(1) mgd77list(1) mgd77manage(1) mgd77track(1)
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178 Wessel, P., and W. H. F. Smith, 2009, The Generic Mapping Tools (GMT)
179 version 4.5.0 Technical Reference & Cookbook, SOEST/NOAA.
180 Wessel, P., and W. H. F. Smith, 1998, New, Improved Version of Generic
181 Mapping Tools Released, EOS Trans., AGU, 79 (47), p. 579.
182 Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
183 ping Tools Released, EOS Trans., AGU, 76 (33), p. 329.
184 Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Map‐
185 ping Tools Released, http://www.agu.org/eos_elec/95154e.html, Copyright
186 1995 by the American Geophysical Union.
187 Wessel, P., and W. H. F. Smith, 1991, Free Software Helps Map and Dis‐
188 play Data, EOS Trans., AGU, 72 (41), p. 441.
189 "Comprehensive Modeling of the Geomagnetic Field", see
190 http://denali.gsfc.nasa.gov/cm/.
191 "The International Geomagnetic Reference Field (IGRF)", see
192 http://www.iugg.org/IAGA/iaga_pages/pubs_prods/igrf.htm.
193GMT 4.5.6 10 Mar 2011 MGD77MAGREF(1)