Royal Belgian Institute for Aeronomy¶

Ex #1. Evaluation of the magnetic field vector¶

Description¶

Evaluation of the magnetic field vector at a given geographic location. The magnetic field is described by the combination of the DGRF/IGRF 1995 geomagnetic model and the Olson & Pfitzer dynamic model. The geographic location is provided in geodetic coordinates.

Source¶

C####################################################################################
C                                                                                   #
C (C) Copyright European Space Agency, 2020                                         #
C                                                                                   #
C This file is subject to the terms and conditions defined in file 'LICENCE.txt',   #
C which is part of this source code package. No part of the package, including      #
C this file, may be copied, modified, propagated, or distributed except             #
C according to the terms contained in the file 'LICENCE.txt'.                       #
C                                                                                   #
C This file forms part of the UNILIB application, available from the                #
C European Space Software Repository (ESSR): https://essr.esa.int/                  #
C                                                                                   #
C####################################################################################

      PROGRAM example1
C
      INCLUDE 'unilib.h'
      INCLUDE 'ext530.h'
C
      INTEGER*4    kunit, kinit, ifail, kint, kext
      CHARACTER*32 lbint, lbext
      REAL*8       year, param(10)
      TYPE(ZDAT) mdate
      TYPE(ZGEO) mgeod, mpos
      TYPE(ZVEC) mb
C
C     initialize variables
C
      DATA kunit, kinit/ 6, 1/
      DATA kint, kext/ KINT_IGRF, KEXT_OP88D/
      DATA year, param/ 1995.d0, 0.d0, -30.d0, 0.d0, 25.d0, 300.d0, 
     :                           0.d0, 0.d0, 0.d0, 0.d0, 0.d0/
C
C     initialize the library
C
C
      CALL UT990 (kunit, kinit, ifail)
      IF( ifail .LT. 0 )STOP
C
C     set the geomagnetic field model
C     (kint=0, DGRF/IGRF)
C
      CALL UM510 (kint, year, lbint, kunit, ifail)
      IF( ifail .LT. 0 )STOP
C
C     set date and time
C
      mdate%iyear   = 1995
      mdate%imonth  =    1
      mdate%iday    =    1
      mdate%ihour   =    0
      mdate%imin    =    0
      mdate%secs    =    0.0d0
C
C     compute the modified julian day
C     (based on January 1, 1950)
C
      CALL UT540 (mdate)          
C
C     set the external magnetic field model
C     (kext=6, Olson et Pfizer dynamic)
C
      CALL UM520 (kext, mdate%amjd, param,
     :           lbext, kunit, ifail)
      IF( ifail .LT. 0 )STOP
C
C     set the geographic location
C
      mgeod%radius  =  300.0d0 + 6371.2d0
      mgeod%colat   =  120.0d0
      mgeod%elong   =   30.0d0
C
C     convert from geodetic to geocentric
C
      CALL UM536 (mgeod, mpos)
C
C     evaluate the magnetic field vector
C
      CALL UM530 (mpos, mb, ifail)
      IF( ifail .LT. 0 )STOP
C
C     write the result
C
      WRITE(kunit,1000) mb%dnrm, mb%rho, mb%theta, mb%phi
C
 1000 FORMAT(
     :  /'RESULT: magnetic field',/25x,
     :               'norm =', 1pe25.15, ' Gauss',/,13x,
     :   'radial component =', 1pe25.15, ' Gauss',/,13x
     :   'along colatitude =', 1pe25.15, ' Gauss',/,14x
     :    'along longitude =', 1pe25.15, ' Gauss' )
C
      END

Results¶

                                    SPENVIS
                                 UNILIB Library
                                 Version 2.22_YCH_initPrep
                           Generated by SPENVIS team


--- Main control parameters ---

      UC160 (general constants):
                     Geoid major axis = 6378.16     km
                     Geoid minor axis = 6356.77     km
               Mean Earth radius (Re) = 6371.20     km
                  Ecliptic inclination =   23.441512 deg
               McIlwain Earth dipole =    0.311653 G/Re^3

      UC190 (field line tracing):
                     Maximum step size =  477.8      km at one Re
            Maximum "last" step size =   15.0      km
                     Minimum step size =    2.0      km
                  Altitude precision =  200.       m
            Magnetic field precision =    0.0006   %

      UC192 (magnetic field evaluation):
            Max. geomagnetic latitude =   85.0      deg
                        Minimum radius =    0.157    Re
            (drift shell tracing):
                        Precision on L =    0.10000  %
            Precision on the longitude =    0.05     deg

--- Geomagnetic field model ---

      Model ( 0): DGRF 1995                          Epoch 1995.
                           Order + 1 =   11
                     Calculation epoch = 1995.0      year
         Colatitude of the dipole pole =   10.68     deg
         Longitude of the dipole pole =  -71.42     deg
                  Earth dipole moment =    0.302151 G/Re^3
         Correction for the SAA drift =    0.00     deg

--- External magnetic field model ---

      Model (6): Olson-Pfitzer dynamic
            Storm activity index Dst =  -30.0      nT
                  Solar wind density =   25.0      1/cm^3
                  Solar wind velocity =  300.0      km/s
                     Standoff distance =    8.6      Re
         Planetary activity index Kp =    0.0      (magnetopause check)

                                 Date =  01-Jan-1995
                        Universal Time =    0.00     hrs
            Greenwich angle of equinox =  100.18     deg
         GEO direction of the Sun, X =   -0.9200
                                    Y =   -0.0129
                                    Z =   -0.3917
                     Dipole tilt angle =  -25.91     deg

-------------------------
RESULT: magnetic field
                        norm =   2.567571783908246E-01 gauss
            radial component =   2.283426241361413E-01 gauss
            along colatitude =  -1.097868129720019E-01 gauss
            along longitude =  -4.160228786123785E-02 gauss
-------------------------

UNILIB/tags/v3.03