1MGD77MAGREF(1) GMT 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 ] [
10 -DDstfile ] [ -Ef107file ] [ -Fflags ] [ -G ] [ -Sc|llow/high ] [
11 -V[level] ] [ -bbinary ] [ -fflags ] [ -hheaders ] [ -:[i|o] ]
12 Note: No space is allowed between the option flag and the associated
14 arguments.
15
17 mgd77magref will evaluate the IGRF or the CM4 geomagnetic models at the
18 specified locations and times.
19
21 None.
22
24 inputfile
25 Contains the moments in space-time where we want to evaluate the
26 magnetic reference field. The first two columns must contain
27 longitude and latitude (however, see -: for latitude and longi‐
28 tude instead). Normally, the third and fourth columns must con‐
29 tain altitude (in km) and time, respectively, but if one or both
30 of these are constant for all records they can be supplied via
31 the -A option instead and are thus not expected in the input
32 file. If no input file is given we read stdin. A note about
33 the CM4 validity domain. The core field of CM4 is valid from
34 1960-2002.5 but the ionospheric and magnetospheric fields are
35 computed after the Dst and F10.7 coefficient files. We extended
36 here those coefficient files up to 2006, which means that one
37 can compute external contributions up until 2006 but the Secular
38 Variation will be biased (non reliable). New indices files may
39 be retrieved from from:ftp://ftp.ngdc.noaa.gov/STP/GEOMAG‐
40 NETIC_DATA/INDICES/DST/ (the Dst coefficients) and
41 http://umbra.nascom.nasa.gov/sdb/yohkoh/ys_dbase/indices_flux_raw/Penticton_Absolute/monthly/MONTHPLT.ABS
42 (The F10.7 index file is a MONTHPLT.ABS). NOTE: since the Dst
43 files in the .../DST/ directory are still only up to 2006, for
44 GMT4.5.3 and after we extended the Dst until August 2009 by
45 reformatting the data in the preliminary file
46 Est_Ist_index_0_mean.pli, which is at
47 ftp://ftp.ngdc.noaa.gov/STP/GEOMAGNETIC_DATA/INDICES/EST_IST/.
48 But since this site is now also outdated, we now get the DST
49 indices from http://wdc.kugi.kyoto-u.ac.jp/dstae/index.html How‐
50 ever, for the most recent dates those indices are "Quick Look"
51 (the best are the "Definitive" type). Because the F10.7 from
52 the MONTHPLT.ABS file mentioned above are apparently no being
53 updated, we found another place where they are, which is:
54 ftp://ftp.ngdc.noaa.gov/STP/space-weather/solar-data/solar-features/
55 solar-radio/noontime-flux/penticton/penticton_absolute/listings/
56 listing_drao_noontime-flux-absolute_monthly.txt
57 -A[+aalt+tdate+y]
59 Adjusts how the input record is interpreted. Append +a to set a
60 fixed altitude (in km) that should apply to all data records
61 [Default expects altitude to be in the 3rd column of all
62 records]. Append +t to set a fixed time that should apply to
63 all data records [Default expects time to be in the 4th column
64 of all records]. Finally, append +y to indicate that all times
65 are specified as decimal years [Default is ISO dateTcolck for‐
66 mat, see TIME_EPOCH].
67 -Ccm4file
69 Specify an alternate CM4 coefficient file [umdl.CM4].
70 -DDstfile
72 Specify an alternate file with hourly means of the Dst index for
73 CM4 [Dst_all.wdc]. Alternatively, simply specify a single index
74 to apply for all records.
75 -Ef107file
77 Specify an alternate file with monthly means of absolute F10.7
78 solar radio flux for CM4 [F107_mon.plt]. Alternatively, simply
79 specify a single flux to apply for all records.
80 -Fflags
82 Selects output items; flags is a string made up of one or more
83 of these characters:
84 r means output all input columns before adding the items below
86 t means list total field (nT).
88 h means list horizontal field (nT).
90 x means list X component (nT, positive north).
92 y means list Y component (nT, positive east).
94 z means list Z component (nT, positive down).
96 d means list declination (deg, clockwise from north).
98 i means list inclination (deg, positive down).
100 Append one or more number to indicate the requested field con‐
102 tribution(s):
103 0 means IGRF field (no combinations allowed)
105 1 means CM4 Core field
107 2 means CM4 Lithospheric field
109 3 means CM4 Primary Magnetospheric field
111 4 means CM4 Induced Magnetospheric field
113 5 means CM4 Primary ionospheric field
115 6 means CM4 Induced ionospheric field
117 7 means CM4 Toroidal field
119 9 means Core field from IGRF and other contributions from CM4.
121 DO NOT USE BOTH 0 AND 9.
122 Appending several numbers (1-7) will add up the different con‐
124 tributions. For example -Ft/12 computes the total field due to
125 Core and Lithospheric sources. Two special cases are allowed,
126 which mix which Core field from IGRF and other sources from CM4.
127 -Ft/934 computes Core field due to IGRF plus terms 3 and 4 from
128 CM4 (but you can add others). -Ft/934 the same as above but out‐
129 put the field components. The data is written out in the order
130 they appear in flags [Default is -Frthxyzdi/1].
131 -G Specifies that coordinates are geocentric [geodetic].
133 -L Computes J field vectors from certain external sources.
135 r means output all input columns before adding the items below
137 (all in Ampers/m).
138 t means list magnitude field.
140 x means list X component.
142 y means list Y component.
144 z means list Z or current function Psi.
146 Append a number to indicate the requested J contribution:
148 1 means Induced Magnetospheric field.
150 2 means Primary ionospheric field.
152 3 means Induced ionospheric field.
154 4 means Poloidal field.
156 -Sclow/high
158 Limits the wavelengths of the core field contribution to the
159 band indicated by the low and high spherical harmonic order
160 [1/13].
161 -Sllow/high
163 Limits the wavelengths of the lithosphere field contribution to
164 the band indicated by the low and high spherical harmonic order
165 [14/65].
166 -V[level] (more ...)
168 Select verbosity level [c].
169 -bi[ncols][t] (more ...)
171 Select native binary input. [Default is 4 input columns unless
172 -A is used].
173 -bo[ncols][type] (more ...)
175 Select native binary output. [Default is reflected by -F].
176 -h[i|o][n][+c][+d][+rremark][+rtitle] (more ...)
178 Skip or produce header record(s).
179 -:[i|o] (more ...)
181 Swap 1st and 2nd column on input and/or output.
182 -^ or just -
184 Print a short message about the syntax of the command, then
185 exits (NOTE: on Windows just use -).
186 -+ or just +
188 Print an extensive usage (help) message, including the explana‐
189 tion of any module-specific option (but not the GMT common
190 options), then exits.
191 -? or no arguments
193 Print a complete usage (help) message, including the explanation
194 of all options, then exits.
195
197 If binary input files are used then absolute time are stored as time
198 relative to the selected epoch. However, since the epoch used is not
199 stored in the data files there can be problems decoding the correct
200 time. The mgd77 supplement uses the Unix time system as its default;
201 thus you should make sure that binary data files with time uses the
202 same system (see the GMT default TIME_SYSTEM).
203
205 To get the CM4 Total field, Declination and Inclination due to all but
206 lithospheric and toroidal field at a one point location and decimal
207 time 2000.0, try
208 echo -28 38 0 2000.0 | gmt mgd77magref -A+y -Ftdi/13456
210 To do the same as above but at noon (Universal Time) of first May 2001,
212 try
213 echo -28 38 0 2001-05-01T12:00:00 | gmt mgd77magref -Ftdi/13456
215
217 gmt, mgd77info, mgd77list, mgd77manage, mgd77track, gmt.conf
218
220 Comprehensive Modeling of the Geomagnetic Field, see
221 http://denali.gsfc.nasa.gov/cm/
222 The International Geomagnetic Reference Field (IGRF), see
224 http://www.iugg.org/IAGA/iaga_pages/pubs_prods/igrf.htm
225
227 2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
2285.4.5 Feb 24, 2019 MGD77MAGREF(1)