manpagez: man pages & more
man mgd77magref(1)
Home | html | info | man
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
© manpagez.com 2000-2024
Individual documents may contain additional copyright information.