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Revision 1.1 - (hide annotations) (download)
Thu Feb 8 00:49:33 2007 UTC (17 years, 10 months ago) by cafagna
Branch point for: MAIN, first
Initial revision

1 cafagna 1.1 c<pre>
2     c
3     c ##########################################################################
4     c # #
5     c # GEOPACK-2005 #
6     c # (MAIN SET OF FORTRAN CODES) #
7     c # #
8     c ##########################################################################
9     C
10     c
11     c This collection of subroutines is a result of several upgrades of the original package
12     c written by N. A. Tsyganenko in 1978-1979. This version is dated May 04, 2005. On that
13     c date, the IGRF coefficients were updated according to the recently published table of
14     c IGRF-10 coefficients, so that the main field model now extends through 2010 (a linear
15     c extrapolation is used for 2005 - 2010, based on the table of secular velocities). For
16     c more details, see http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html (revision of 03/22/2005).
17     c
18     c
19     c Prefatory notes to the version of April 22, 2003:
20     c
21     c This package represents an in-depth revision of the previous version, with significant
22     c changes in the format of calling statements. Users should familiarize themselves with
23     c the new formats and rules, and accordingly adjust their source codes, as specified
24     c below. Please consult the documentation file geopack-2005.doc (also available from this
25     c site) for detailed descriptions of individual subroutines.
26     c
27     c The following changes were made to the previous release of GEOPACK (of Jan 5, 2001).
28     c
29     c (1) Subroutine IGRF, calculating the Earth's main field:
30    
31     c (a) Two versions of this subroutine are provided here. In the first one (IGRF_GSM)
32     c both input (position) and output (field components) are in the Geocentric Solar-
33     c Magnetospheric Cartesian coordinates, while the second one (IGRF_GEO) uses sphe-
34     c rical geographical (geocentric) coordinates, as in the older releases.
35    
36     c (b) updating of all expansion coefficients is now made separately in the s/r RECALC,
37     c which also takes into account the secular change of the coefficients within
38     c a given year (at the Earth's surface, the rate of the change can reach 7 nT/month).
39    
40     c (c) the optimal length of spherical harmonic expansions is now automatically set
41     c inside the code, based on the radial distance, so that the deviation from the
42     c full-length approximation does not exceed 0.01 nT. (In the previous versions,
43     c the upper limit NM of the order of harmonics had to be specified by users),
44     c
45     c (2) Subroutine DIP, calculating the Earth's field in the dipole approximation:
46    
47     c (a) no longer accepts the tilt angle via the list of formal parameters. Instead,
48     c the sine SPS and cosine CPS of that angle are now forwarded into DIP via the
49     c first common block /GEOPACK1/. Accordingly, there are two options: (i) to
50     c calculate SPS and CPS by calling RECALC before calling DIP, or (ii) to specify
51     c them explicitly. In the last case, SPS and CPS should be specified AFTER the
52     c invocation of RECALC (otherwise they will be overridden by those returned by
53     c RECALC).
54    
55     c (b) the Earth's dipole moment is now calculated by RECALC, based on the table of
56     c the IGRF coefficients and their secular variation rates, for a given year and
57     c the day of the year, and the obtained value of the moment is forwarded into DIP
58     c via the second common block /GEOPACK2/. (In the previous versions, only a single
59     c fixed value was provided for the geodipole moment, corresponding to the most
60     c recent epoch).
61     c
62     c (3) Subroutine RECALC now consolidates in one module all calculations needed to
63     c initialize and update the values of coefficients and quantities that vary in
64     c time, either due to secular changes of the main geomagnetic field or as a result
65     c of Earth's diurnal rotation and orbital motion around Sun. That allowed us to
66     c simplify the codes and make them more compiler-independent.
67     c
68     c (4) Subroutine GEOMAG is now identical in its structure to other coordinate trans-
69     c formation subroutines. It no longer invokes RECALC from within GEOMAG, but uses
70     c precalculated values of the rotation matrix elements, obtained by a separate
71     c external invocation of RECALC. This eliminates possible interference of the
72     c two subroutines in the old version of the package.
73     c
74     c (5) Subroutine TRACE (and the subsidiary modules STEP and RHAND):
75     c
76     c (a) no longer needs to specify the highest order of spherical harmonics in the
77     c main geomagnetic field expansion - it is now calculated automatically inside the
78     c IGRF_GSM (or IGRF_GEO) subroutine.
79     c
80     c (b) the internal field model can now be explicitly chosen by specifying the para-
81     c meter INNAME (either IGRF_GSM or DIP).
82     c
83     c (6) A new subroutine BCARSP was added, providing a conversion of Cartesian field
84     c components into spherical ones (operation, inverse to that performed by the sub-
85     c routine BSPCAR).
86     c
87     c (7) Two new subroutines were added, SHUETAL_MGNP and T96_MGNP, providing the position
88     c of the magnetopause, according to the model of Shue et al. [1998] and the one
89     c used in the T96 magnetospheric magnetic field model.
90     c
91     c
92     c----------------------------------------------------------------------------------
93     c
94     SUBROUTINE IGRF_GSM (XGSM,YGSM,ZGSM,HXGSM,HYGSM,HZGSM)
95     c
96     C CALCULATES COMPONENTS OF THE MAIN (INTERNAL) GEOMAGNETIC FIELD IN THE GEOCENTRIC SOLAR
97     C MAGNETOSPHERIC COORDINATE SYSTEM, USING IAGA INTERNATIONAL GEOMAGNETIC REFERENCE MODEL
98     C COEFFICIENTS (e.g., http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html Revised: 22 March, 2005)
99     c
100     C
101     C BEFORE THE FIRST CALL OF THIS SUBROUTINE, OR IF THE DATE/TIME (IYEAR,IDAY,IHOUR,MIN,ISEC)
102     C WAS CHANGED, THE MODEL COEFFICIENTS AND GEO-GSM ROTATION MATRIX ELEMENTS SHOULD BE UPDATED
103     c BY CALLING THE SUBROUTINE RECALC
104     C
105     C-----INPUT PARAMETERS:
106     C
107     C XGSM,YGSM,ZGSM - CARTESIAN GSM COORDINATES (IN UNITS RE=6371.2 KM)
108     C
109     C-----OUTPUT PARAMETERS:
110     C
111     C HXGSM,HYGSM,HZGSM - CARTESIAN GSM COMPONENTS OF THE MAIN GEOMAGNETIC FIELD IN NANOTESLA
112     C
113     C LAST MODIFICATION: MAY 4, 2005.
114     C THIS VERSION OF THE CODE ACCEPTS DATES FROM 1965 THROUGH 2010.
115     c
116     C AUTHOR: N. A. TSYGANENKO
117     C
118     C
119     COMMON /GEOPACK2/ G(105),H(105),REC(105)
120    
121     DIMENSION A(14),B(14)
122    
123     CALL GEOGSM (XGEO,YGEO,ZGEO,XGSM,YGSM,ZGSM,-1)
124     RHO2=XGEO**2+YGEO**2
125     R=SQRT(RHO2+ZGEO**2)
126     C=ZGEO/R
127     RHO=SQRT(RHO2)
128     S=RHO/R
129     IF (S.LT.1.E-5) THEN
130     CF=1.
131     SF=0.
132     ELSE
133     CF=XGEO/RHO
134     SF=YGEO/RHO
135     ENDIF
136     C
137     PP=1./R
138     P=PP
139     C
140     C IN THIS NEW VERSION, THE OPTIMAL VALUE OF THE PARAMETER NM (MAXIMAL ORDER OF THE SPHERICAL
141     C HARMONIC EXPANSION) IS NOT USER-PRESCRIBED, BUT CALCULATED INSIDE THE SUBROUTINE, BASED
142     C ON THE VALUE OF THE RADIAL DISTANCE R:
143     C
144     IRP3=R+2
145     NM=3+30/IRP3
146     IF (NM.GT.13) NM=13
147    
148     K=NM+1
149     DO 150 N=1,K
150     P=P*PP
151     A(N)=P
152     150 B(N)=P*N
153    
154     P=1.
155     D=0.
156     BBR=0.
157     BBT=0.
158     BBF=0.
159    
160     DO 200 M=1,K
161     IF(M.EQ.1) GOTO 160
162     MM=M-1
163     W=X
164     X=W*CF+Y*SF
165     Y=Y*CF-W*SF
166     GOTO 170
167     160 X=0.
168     Y=1.
169     170 Q=P
170     Z=D
171     BI=0.
172     P2=0.
173     D2=0.
174     DO 190 N=M,K
175     AN=A(N)
176     MN=N*(N-1)/2+M
177     E=G(MN)
178     HH=H(MN)
179     W=E*Y+HH*X
180     BBR=BBR+B(N)*W*Q
181     BBT=BBT-AN*W*Z
182     IF(M.EQ.1) GOTO 180
183     QQ=Q
184     IF(S.LT.1.E-5) QQ=Z
185     BI=BI+AN*(E*X-HH*Y)*QQ
186     180 XK=REC(MN)
187     DP=C*Z-S*Q-XK*D2
188     PM=C*Q-XK*P2
189     D2=Z
190     P2=Q
191     Z=DP
192     190 Q=PM
193     D=S*D+C*P
194     P=S*P
195     IF(M.EQ.1) GOTO 200
196     BI=BI*MM
197     BBF=BBF+BI
198     200 CONTINUE
199     C
200     BR=BBR
201     BT=BBT
202     IF(S.LT.1.E-5) GOTO 210
203     BF=BBF/S
204     GOTO 211
205     210 IF(C.LT.0.) BBF=-BBF
206     BF=BBF
207    
208     211 HE=BR*S+BT*C
209     HXGEO=HE*CF-BF*SF
210     HYGEO=HE*SF+BF*CF
211     HZGEO=BR*C-BT*S
212    
213     CALL GEOGSM (HXGEO,HYGEO,HZGEO,HXGSM,HYGSM,HZGSM,1)
214    
215     RETURN
216     END
217     C
218     c==========================================================================================
219     C
220     c
221     SUBROUTINE IGRF_GEO (R,THETA,PHI,BR,BTHETA,BPHI)
222     c
223     C CALCULATES COMPONENTS OF THE MAIN (INTERNAL) GEOMAGNETIC FIELD IN THE SPHERICAL GEOGRAPHIC
224     C (GEOCENTRIC) COORDINATE SYSTEM, USING IAGA INTERNATIONAL GEOMAGNETIC REFERENCE MODEL
225     C COEFFICIENTS (e.g., http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html, revised: 22 March, 2005)
226     C
227     C BEFORE THE FIRST CALL OF THIS SUBROUTINE, OR IF THE DATE (IYEAR AND IDAY) WAS CHANGED,
228     C THE MODEL COEFFICIENTS SHOULD BE UPDATED BY CALLING THE SUBROUTINE RECALC
229     C
230     C-----INPUT PARAMETERS:
231     C
232     C R, THETA, PHI - SPHERICAL GEOGRAPHIC (GEOCENTRIC) COORDINATES:
233     C RADIAL DISTANCE R IN UNITS RE=6371.2 KM, COLATITUDE THETA AND LONGITUDE PHI IN RADIANS
234     C
235     C-----OUTPUT PARAMETERS:
236     C
237     C BR, BTHETA, BPHI - SPHERICAL COMPONENTS OF THE MAIN GEOMAGNETIC FIELD IN NANOTESLA
238     C (POSITIVE BR OUTWARD, BTHETA SOUTHWARD, BPHI EASTWARD)
239     C
240     C LAST MODIFICATION: MAY 4, 2005.
241     C THIS VERSION OF THE CODE ACCEPTS DATES FROM 1965 THROUGH 2010.
242     c
243     C AUTHOR: N. A. TSYGANENKO
244     C
245     C
246     COMMON /GEOPACK2/ G(105),H(105),REC(105)
247    
248     DIMENSION A(14),B(14)
249    
250     C=COS(THETA)
251     S=SIN(THETA)
252     CF=COS(PHI)
253     SF=SIN(PHI)
254     C
255     PP=1./R
256     P=PP
257     C
258     C IN THIS NEW VERSION, THE OPTIMAL VALUE OF THE PARAMETER NM (MAXIMAL ORDER OF THE SPHERICAL
259     C HARMONIC EXPANSION) IS NOT USER-PRESCRIBED, BUT CALCULATED INSIDE THE SUBROUTINE, BASED
260     C ON THE VALUE OF THE RADIAL DISTANCE R:
261     C
262     IRP3=R+2
263     NM=3+30/IRP3
264     IF (NM.GT.13) NM=13
265    
266     K=NM+1
267     DO 150 N=1,K
268     P=P*PP
269     A(N)=P
270     150 B(N)=P*N
271    
272     P=1.
273     D=0.
274     BBR=0.
275     BBT=0.
276     BBF=0.
277    
278     DO 200 M=1,K
279     IF(M.EQ.1) GOTO 160
280     MM=M-1
281     W=X
282     X=W*CF+Y*SF
283     Y=Y*CF-W*SF
284     GOTO 170
285     160 X=0.
286     Y=1.
287     170 Q=P
288     Z=D
289     BI=0.
290     P2=0.
291     D2=0.
292     DO 190 N=M,K
293     AN=A(N)
294     MN=N*(N-1)/2+M
295     E=G(MN)
296     HH=H(MN)
297     W=E*Y+HH*X
298     BBR=BBR+B(N)*W*Q
299     BBT=BBT-AN*W*Z
300     IF(M.EQ.1) GOTO 180
301     QQ=Q
302     IF(S.LT.1.E-5) QQ=Z
303     BI=BI+AN*(E*X-HH*Y)*QQ
304     180 XK=REC(MN)
305     DP=C*Z-S*Q-XK*D2
306     PM=C*Q-XK*P2
307     D2=Z
308     P2=Q
309     Z=DP
310     190 Q=PM
311     D=S*D+C*P
312     P=S*P
313     IF(M.EQ.1) GOTO 200
314     BI=BI*MM
315     BBF=BBF+BI
316     200 CONTINUE
317     C
318     BR=BBR
319     BTHETA=BBT
320     IF(S.LT.1.E-5) GOTO 210
321     BPHI=BBF/S
322     RETURN
323     210 IF(C.LT.0.) BBF=-BBF
324     BPHI=BBF
325    
326     RETURN
327     END
328     C
329     c==========================================================================================
330     c
331     SUBROUTINE DIP (XGSM,YGSM,ZGSM,BXGSM,BYGSM,BZGSM)
332     C
333     C CALCULATES GSM COMPONENTS OF A GEODIPOLE FIELD WITH THE DIPOLE MOMENT
334     C CORRESPONDING TO THE EPOCH, SPECIFIED BY CALLING SUBROUTINE RECALC (SHOULD BE
335     C INVOKED BEFORE THE FIRST USE OF THIS ONE AND IN CASE THE DATE/TIME WAS CHANGED).
336     C
337     C--INPUT PARAMETERS: XGSM,YGSM,ZGSM - GSM COORDINATES IN RE (1 RE = 6371.2 km)
338     C
339     C--OUTPUT PARAMETERS: BXGSM,BYGSM,BZGSM - FIELD COMPONENTS IN GSM SYSTEM, IN NANOTESLA.
340     C
341     C LAST MODIFICATION: MAY 4, 2005
342     C
343     C AUTHOR: N. A. TSYGANENKO
344     C
345     COMMON /GEOPACK1/ AAA(10),SPS,CPS,BBB(23)
346     COMMON /GEOPACK2/ G(105),H(105),REC(105)
347    
348     DIPMOM=SQRT(G(2)**2+G(3)**2+H(3)**2)
349    
350     P=XGSM**2
351     U=ZGSM**2
352     V=3.*ZGSM*XGSM
353     T=YGSM**2
354     Q=DIPMOM/SQRT(P+T+U)**5
355     BXGSM=Q*((T+U-2.*P)*SPS-V*CPS)
356     BYGSM=-3.*YGSM*Q*(XGSM*SPS+ZGSM*CPS)
357     BZGSM=Q*((P+T-2.*U)*CPS-V*SPS)
358     RETURN
359     END
360    
361     C*******************************************************************
362     c
363     SUBROUTINE SUN (IYEAR,IDAY,IHOUR,MIN,ISEC,GST,SLONG,SRASN,SDEC)
364     C
365     C CALCULATES FOUR QUANTITIES NECESSARY FOR COORDINATE TRANSFORMATIONS
366     C WHICH DEPEND ON SUN POSITION (AND, HENCE, ON UNIVERSAL TIME AND SEASON)
367     C
368     C------- INPUT PARAMETERS:
369     C IYR,IDAY,IHOUR,MIN,ISEC - YEAR, DAY, AND UNIVERSAL TIME IN HOURS, MINUTES,
370     C AND SECONDS (IDAY=1 CORRESPONDS TO JANUARY 1).
371     C
372     C------- OUTPUT PARAMETERS:
373     C GST - GREENWICH MEAN SIDEREAL TIME, SLONG - LONGITUDE ALONG ECLIPTIC
374     C SRASN - RIGHT ASCENSION, SDEC - DECLINATION OF THE SUN (RADIANS)
375     C ORIGINAL VERSION OF THIS SUBROUTINE HAS BEEN COMPILED FROM:
376     C RUSSELL, C.T., COSMIC ELECTRODYNAMICS, 1971, V.2, PP.184-196.
377     C
378     C LAST MODIFICATION: MARCH 31, 2003 (ONLY SOME NOTATION CHANGES)
379     C
380     C ORIGINAL VERSION WRITTEN BY: Gilbert D. Mead
381     C
382     DOUBLE PRECISION DJ,FDAY
383     DATA RAD/57.295779513/
384     C
385     IF(IYEAR.LT.1901.OR.IYEAR.GT.2099) RETURN
386     FDAY=DFLOAT(IHOUR*3600+MIN*60+ISEC)/86400.D0
387     DJ=365*(IYEAR-1900)+(IYEAR-1901)/4+IDAY-0.5D0+FDAY
388     T=DJ/36525.
389     VL=DMOD(279.696678+0.9856473354*DJ,360.D0)
390     GST=DMOD(279.690983+.9856473354*DJ+360.*FDAY+180.,360.D0)/RAD
391     G=DMOD(358.475845+0.985600267*DJ,360.D0)/RAD
392     SLONG=(VL+(1.91946-0.004789*T)*SIN(G)+0.020094*SIN(2.*G))/RAD
393     IF(SLONG.GT.6.2831853) SLONG=SLONG-6.2831853
394     IF (SLONG.LT.0.) SLONG=SLONG+6.2831853
395     OBLIQ=(23.45229-0.0130125*T)/RAD
396     SOB=SIN(OBLIQ)
397     SLP=SLONG-9.924E-5
398     C
399     C THE LAST CONSTANT IS A CORRECTION FOR THE ANGULAR ABERRATION DUE TO
400     C THE ORBITAL MOTION OF THE EARTH
401     C
402     SIND=SOB*SIN(SLP)
403     COSD=SQRT(1.-SIND**2)
404     SC=SIND/COSD
405     SDEC=ATAN(SC)
406     SRASN=3.141592654-ATAN2(COS(OBLIQ)/SOB*SC,-COS(SLP)/COSD)
407     RETURN
408     END
409     C
410     C================================================================================
411     c
412     SUBROUTINE SPHCAR (R,THETA,PHI,X,Y,Z,J)
413     C
414     C CONVERTS SPHERICAL COORDS INTO CARTESIAN ONES AND VICA VERSA
415     C (THETA AND PHI IN RADIANS).
416     C
417     C J>0 J<0
418     C-----INPUT: J,R,THETA,PHI J,X,Y,Z
419     C----OUTPUT: X,Y,Z R,THETA,PHI
420     C
421     C NOTE: AT THE POLES (X=0 AND Y=0) WE ASSUME PHI=0 (WHEN CONVERTING
422     C FROM CARTESIAN TO SPHERICAL COORDS, I.E., FOR J<0)
423     C
424     C LAST MOFIFICATION: APRIL 1, 2003 (ONLY SOME NOTATION CHANGES AND MORE
425     C COMMENTS ADDED)
426     C
427     C AUTHOR: N. A. TSYGANENKO
428     C
429     IF(J.GT.0) GOTO 3
430     SQ=X**2+Y**2
431     R=SQRT(SQ+Z**2)
432     IF (SQ.NE.0.) GOTO 2
433     PHI=0.
434     IF (Z.LT.0.) GOTO 1
435     THETA=0.
436     RETURN
437     1 THETA=3.141592654
438     RETURN
439     2 SQ=SQRT(SQ)
440     PHI=ATAN2(Y,X)
441     THETA=ATAN2(SQ,Z)
442     IF (PHI.LT.0.) PHI=PHI+6.28318531
443     RETURN
444     3 SQ=R*SIN(THETA)
445     X=SQ*COS(PHI)
446     Y=SQ*SIN(PHI)
447     Z=R*COS(THETA)
448     RETURN
449     END
450     C
451     C===========================================================================
452     c
453     SUBROUTINE BSPCAR (THETA,PHI,BR,BTHETA,BPHI,BX,BY,BZ)
454     C
455     C CALCULATES CARTESIAN FIELD COMPONENTS FROM SPHERICAL ONES
456     C-----INPUT: THETA,PHI - SPHERICAL ANGLES OF THE POINT IN RADIANS
457     C BR,BTHETA,BPHI - SPHERICAL COMPONENTS OF THE FIELD
458     C-----OUTPUT: BX,BY,BZ - CARTESIAN COMPONENTS OF THE FIELD
459     C
460     C LAST MOFIFICATION: APRIL 1, 2003 (ONLY SOME NOTATION CHANGES)
461     C
462     C WRITTEN BY: N. A. TSYGANENKO
463     C
464     S=SIN(THETA)
465     C=COS(THETA)
466     SF=SIN(PHI)
467     CF=COS(PHI)
468     BE=BR*S+BTHETA*C
469     BX=BE*CF-BPHI*SF
470     BY=BE*SF+BPHI*CF
471     BZ=BR*C-BTHETA*S
472     RETURN
473     END
474     c
475     C==============================================================================
476     C
477     SUBROUTINE BCARSP (X,Y,Z,BX,BY,BZ,BR,BTHETA,BPHI)
478     C
479     CALCULATES SPHERICAL FIELD COMPONENTS FROM THOSE IN CARTESIAN SYSTEM
480     C
481     C-----INPUT: X,Y,Z - CARTESIAN COMPONENTS OF THE POSITION VECTOR
482     C BX,BY,BZ - CARTESIAN COMPONENTS OF THE FIELD VECTOR
483     C-----OUTPUT: BR,BTHETA,BPHI - SPHERICAL COMPONENTS OF THE FIELD VECTOR
484     C
485     C NOTE: AT THE POLES (THETA=0 OR THETA=PI) WE ASSUME PHI=0,
486     C AND HENCE BTHETA=BX, BPHI=BY
487     C
488     C WRITTEN AND ADDED TO THIS PACKAGE: APRIL 1, 2003,
489     C AUTHOR: N. A. TSYGANENKO
490     C
491     RHO2=X**2+Y**2
492     R=SQRT(RHO2+Z**2)
493     RHO=SQRT(RHO2)
494    
495     IF (RHO.NE.0.) THEN
496     CPHI=X/RHO
497     SPHI=Y/RHO
498     ELSE
499     CPHI=1.
500     SPHI=0.
501     ENDIF
502    
503     CT=Z/R
504     ST=RHO/R
505    
506     BR=(X*BX+Y*BY+Z*BZ)/R
507     BTHETA=(BX*CPHI+BY*SPHI)*CT-BZ*ST
508     BPHI=BY*CPHI-BX*SPHI
509    
510     RETURN
511     END
512     C
513     c=====================================================================================
514     C
515     SUBROUTINE RECALC (IYEAR,IDAY,IHOUR,MIN,ISEC)
516     C
517     C 1. PREPARES ELEMENTS OF ROTATION MATRICES FOR TRANSFORMATIONS OF VECTORS BETWEEN
518     C SEVERAL COORDINATE SYSTEMS, MOST FREQUENTLY USED IN SPACE PHYSICS.
519     C
520     C 2. PREPARES COEFFICIENTS USED IN THE CALCULATION OF THE MAIN GEOMAGNETIC FIELD
521     C (IGRF MODEL)
522     C
523     C THIS SUBROUTINE SHOULD BE INVOKED BEFORE USING THE FOLLOWING SUBROUTINES:
524     C IGRF_GEO, IGRF_GSM, DIP, GEOMAG, GEOGSM, MAGSM, SMGSM, GSMGSE, GEIGEO.
525     C
526     C THERE IS NO NEED TO REPEATEDLY INVOKE RECALC, IF MULTIPLE CALCULATIONS ARE MADE
527     C FOR THE SAME DATE AND TIME.
528     C
529     C-----INPUT PARAMETERS:
530     C
531     C IYEAR - YEAR NUMBER (FOUR DIGITS)
532     C IDAY - DAY OF YEAR (DAY 1 = JAN 1)
533     C IHOUR - HOUR OF DAY (00 TO 23)
534     C MIN - MINUTE OF HOUR (00 TO 59)
535     C ISEC - SECONDS OF MINUTE (00 TO 59)
536     C
537     C-----OUTPUT PARAMETERS: NONE (ALL OUTPUT QUANTITIES ARE PLACED
538     C INTO THE COMMON BLOCKS /GEOPACK1/ AND /GEOPACK2/)
539     C
540     C OTHER SUBROUTINES CALLED BY THIS ONE: SUN
541     C
542     C AUTHOR: N.A. TSYGANENKO
543     C DATE: DEC.1, 1991
544     C
545     C REVISION OF MAY 3, 2005:
546     C The table of IGRF coefficients was extended to include those for the epoch 2005
547     c the maximal order of spherical harmonics was also increased up to 13
548     c (for details, see http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html)
549     c
550     C REVISION OF APRIL 3, 2003:
551     c The code now includes preparation of the model coefficients for the subroutines
552     c IGRF and GEOMAG. This eliminates the need for the SAVE statements, used in the
553     c old versions, making the codes easier and more compiler-independent.
554     C
555     COMMON /GEOPACK1/ ST0,CT0,SL0,CL0,CTCL,STCL,CTSL,STSL,SFI,CFI,SPS,
556     * CPS,SHI,CHI,HI,PSI,XMUT,A11,A21,A31,A12,A22,A32,A13,A23,A33,DS3,
557     * CGST,SGST,BA(6)
558     C
559     C THE COMMON BLOCK /GEOPACK1/ CONTAINS ELEMENTS OF THE ROTATION MATRICES AND OTHER
560     C PARAMETERS RELATED TO THE COORDINATE TRANSFORMATIONS PERFORMED BY THIS PACKAGE
561     C
562     COMMON /GEOPACK2/ G(105),H(105),REC(105)
563     C
564     C THE COMMON BLOCK /GEOPACK2/ CONTAINS COEFFICIENTS OF THE IGRF FIELD MODEL, CALCULATED
565     C FOR A GIVEN YEAR AND DAY FROM THEIR STANDARD EPOCH VALUES. THE ARRAY REC CONTAINS
566     C COEFFICIENTS USED IN THE RECURSION RELATIONS FOR LEGENDRE ASSOCIATE POLYNOMIALS.
567     C
568     DIMENSION G65(105),H65(105),G70(105),H70(105),G75(105),H75(105),
569     + G80(105),H80(105),G85(105),H85(105),G90(105),H90(105),G95(105),
570     + H95(105),G00(105),H00(105),G05(105),H05(105),DG05(45),DH05(45)
571     c
572     DATA G65/0.,-30334.,-2119.,-1662.,2997.,1594.,1297.,-2038.,1292.,
573     *856.,957.,804.,479.,-390.,252.,-219.,358.,254.,-31.,-157.,-62.,
574     *45.,61.,8.,-228.,4.,1.,-111.,75.,-57.,4.,13.,-26.,-6.,13.,1.,13.,
575     *5.,-4.,-14.,0.,8.,-1.,11.,4.,8.,10.,2.,-13.,10.,-1.,-1.,5.,1.,-2.,
576     *-2.,-3.,2.,-5.,-2.,4.,4.,0.,2.,2.,0.,39*0./
577     DATA H65/0.,0.,5776.,0.,-2016.,114.,0.,-404.,240.,-165.,0.,148.,
578     *-269.,13.,-269.,0.,19.,128.,-126.,-97.,81.,0.,-11.,100.,68.,-32.,
579     *-8.,-7.,0.,-61.,-27.,-2.,6.,26.,-23.,-12.,0.,7.,-12.,9.,-16.,4.,
580     *24.,-3.,-17.,0.,-22.,15.,7.,-4.,-5.,10.,10.,-4.,1.,0.,2.,1.,2.,
581     *6.,-4.,0.,-2.,3.,0.,-6.,39*0./
582     c
583     DATA G70/0.,-30220.,-2068.,-1781.,3000.,1611.,1287.,-2091.,1278.,
584     *838.,952.,800.,461.,-395.,234.,-216.,359.,262.,-42.,-160.,-56.,
585     *43.,64.,15.,-212.,2.,3.,-112.,72.,-57.,1.,14.,-22.,-2.,13.,-2.,
586     *14.,6.,-2.,-13.,-3.,5.,0.,11.,3.,8.,10.,2.,-12.,10.,-1.,0.,3.,
587     *1.,-1.,-3.,-3.,2.,-5.,-1.,6.,4.,1.,0.,3.,-1.,39*0./
588     DATA H70/0.,0.,5737.,0.,-2047.,25.,0.,-366.,251.,-196.,0.,167.,
589     *-266.,26.,-279.,0.,26.,139.,-139.,-91.,83.,0.,-12.,100.,72.,-37.,
590     *-6.,1.,0.,-70.,-27.,-4.,8.,23.,-23.,-11.,0.,7.,-15.,6.,-17.,6.,
591     *21.,-6.,-16.,0.,-21.,16.,6.,-4.,-5.,10.,11.,-2.,1.,0.,1.,1.,3.,
592     *4.,-4.,0.,-1.,3.,1.,-4.,39*0./
593     c
594     DATA G75/0.,-30100.,-2013.,-1902.,3010.,1632.,1276.,-2144.,1260.,
595     *830.,946.,791.,438.,-405.,216.,-218.,356.,264.,-59.,-159.,-49.,
596     *45.,66.,28.,-198.,1.,6.,-111.,71.,-56.,1.,16.,-14.,0.,12.,-5.,
597     *14.,6.,-1.,-12.,-8.,4.,0.,10.,1.,7.,10.,2.,-12.,10.,-1.,-1.,4.,
598     *1.,-2.,-3.,-3.,2.,-5.,-2.,5.,4.,1.,0.,3.,-1.,39*0./
599     DATA H75/0.,0.,5675.,0.,-2067.,-68.,0.,-333.,262.,-223.,0.,191.,
600     *-265.,39.,-288.,0.,31.,148.,-152.,-83.,88.,0.,-13.,99.,75.,-41.,
601     *-4.,11.,0.,-77.,-26.,-5.,10.,22.,-23.,-12.,0.,6.,-16.,4.,-19.,6.,
602     *18.,-10.,-17.,0.,-21.,16.,7.,-4.,-5.,10.,11.,-3.,1.,0.,1.,1.,3.,
603     *4.,-4.,-1.,-1.,3.,1.,-5.,39*0./
604     c
605     DATA G80/0.,-29992.,-1956.,-1997.,3027.,1663.,1281.,-2180.,1251.,
606     *833.,938.,782.,398.,-419.,199.,-218.,357.,261.,-74.,-162.,-48.,
607     *48.,66.,42.,-192.,4.,14.,-108.,72.,-59.,2.,21.,-12.,1.,11.,-2.,
608     *18.,6.,0.,-11.,-7.,4.,3.,6.,-1.,5.,10.,1.,-12.,9.,-3.,-1.,7.,2.,
609     *-5.,-4.,-4.,2.,-5.,-2.,5.,3.,1.,2.,3.,0.,39*0./
610     DATA H80/0.,0.,5604.,0.,-2129.,-200.,0.,-336.,271.,-252.,0.,212.,
611     *-257.,53.,-297.,0.,46.,150.,-151.,-78.,92.,0.,-15.,93.,71.,-43.,
612     *-2.,17.,0.,-82.,-27.,-5.,16.,18.,-23.,-10.,0.,7.,-18.,4.,-22.,9.,
613     *16.,-13.,-15.,0.,-21.,16.,9.,-5.,-6.,9.,10.,-6.,2.,0.,1.,0.,3.,
614     *6.,-4.,0.,-1.,4.,0.,-6.,39*0./
615     c
616     DATA G85/0.,-29873.,-1905.,-2072.,3044.,1687.,1296.,-2208.,1247.,
617     *829.,936.,780.,361.,-424.,170.,-214.,355.,253.,-93.,-164.,-46.,
618     *53.,65.,51.,-185.,4.,16.,-102.,74.,-62.,3.,24.,-6.,4.,10.,0.,21.,
619     *6.,0.,-11.,-9.,4.,4.,4.,-4.,5.,10.,1.,-12.,9.,-3.,-1.,7.,1.,-5.,
620     *-4.,-4.,3.,-5.,-2.,5.,3.,1.,2.,3.,0.,39*0./
621     DATA H85/0.,0.,5500.,0.,-2197.,-306.,0.,-310.,284.,-297.,0.,232.,
622     *-249.,69.,-297.,0.,47.,150.,-154.,-75.,95.,0.,-16.,88.,69.,-48.,
623     *-1.,21.,0.,-83.,-27.,-2.,20.,17.,-23.,-7.,0.,8.,-19.,5.,-23.,11.,
624     *14.,-15.,-11.,0.,-21.,15.,9.,-6.,-6.,9.,9.,-7.,2.,0.,1.,0.,3.,
625     *6.,-4.,0.,-1.,4.,0.,-6.,39*0./
626     c
627     DATA G90/0., -29775., -1848., -2131., 3059., 1686., 1314.,
628     * -2239., 1248., 802., 939., 780., 325., -423.,
629     * 141., -214., 353., 245., -109., -165., -36.,
630     * 61., 65., 59., -178., 3., 18., -96.,
631     * 77., -64., 2., 26., -1., 5., 9.,
632     * 0., 23., 5., -1., -10., -12., 3.,
633     * 4., 2., -6., 4., 9., 1., -12.,
634     * 9., -4., -2., 7., 1., -6., -3.,
635     * -4., 2., -5., -2., 4., 3., 1.,
636     * 3., 3., 0., 39*0./
637    
638     DATA H90/0., 0., 5406., 0., -2279., -373., 0.,
639     * -284., 293., -352., 0., 247., -240., 84.,
640     * -299., 0., 46., 154., -153., -69., 97.,
641     * 0., -16., 82., 69., -52., 1., 24.,
642     * 0., -80., -26., 0., 21., 17., -23.,
643     * -4., 0., 10., -19., 6., -22., 12.,
644     * 12., -16., -10., 0., -20., 15., 11.,
645     * -7., -7., 9., 8., -7., 2., 0.,
646     * 2., 1., 3., 6., -4., 0., -2.,
647     * 3., -1., -6., 39*0./
648    
649     DATA G95/0., -29692., -1784., -2200., 3070., 1681., 1335.,
650     * -2267., 1249., 759., 940., 780., 290., -418.,
651     * 122., -214., 352., 235., -118., -166., -17.,
652     * 68., 67., 68., -170., -1., 19., -93.,
653     * 77., -72., 1., 28., 5., 4., 8.,
654     * -2., 25., 6., -6., -9., -14., 9.,
655     * 6., -5., -7., 4., 9., 3., -10.,
656     * 8., -8., -1., 10., -2., -8., -3.,
657     * -6., 2., -4., -1., 4., 2., 2.,
658     * 5., 1., 0., 39*0./
659    
660     DATA H95/0., 0., 5306., 0., -2366., -413., 0.,
661     * -262., 302., -427., 0., 262., -236., 97.,
662     * -306., 0., 46., 165., -143., -55., 107.,
663     * 0., -17., 72., 67., -58., 1., 36.,
664     * 0., -69., -25., 4., 24., 17., -24.,
665     * -6., 0., 11., -21., 8., -23., 15.,
666     * 11., -16., -4., 0., -20., 15., 12.,
667     * -6., -8., 8., 5., -8., 3., 0.,
668     * 1., 0., 4., 5., -5., -1., -2.,
669     * 1., -2., -7., 39*0./
670    
671     DATA G00/0.,-29619.4, -1728.2, -2267.7, 3068.4, 1670.9, 1339.6,
672     * -2288., 1252.1, 714.5, 932.3, 786.8, 250., -403.,
673     * 111.3, -218.8, 351.4, 222.3, -130.4, -168.6, -12.9,
674     * 72.3, 68.2, 74.2, -160.9, -5.9, 16.9, -90.4,
675     * 79.0, -74.0, 0., 33.3, 9.1, 6.9, 7.3,
676     * -1.2, 24.4, 6.6, -9.2, -7.9, -16.6, 9.1,
677     * 7.0, -7.9, -7., 5., 9.4, 3., - 8.4,
678     * 6.3, -8.9, -1.5, 9.3, -4.3, -8.2, -2.6,
679     * -6., 1.7, -3.1, -0.5, 3.7, 1., 2.,
680     * 4.2, 0.3, -1.1, 2.7, -1.7, -1.9, 1.5,
681     * -0.1, 0.1, -0.7, 0.7, 1.7, 0.1, 1.2,
682     * 4.0, -2.2, -0.3, 0.2, 0.9, -0.2, 0.9,
683     * -0.5, 0.3, -0.3, -0.4, -0.1, -0.2, -0.4,
684     * -0.2, -0.9, 0.3, 0.1, -0.4, 1.3, -0.4,
685     * 0.7, -0.4, 0.3, -0.1, 0.4, 0., 0.1/
686    
687    
688     DATA H00/0., 0., 5186.1, 0., -2481.6, -458.0, 0.,
689     * -227.6, 293.4, -491.1, 0., 272.6, -231.9, 119.8,
690     * -303.8, 0., 43.8, 171.9, -133.1, -39.3, 106.3,
691     * 0., -17.4, 63.7, 65.1, -61.2, 0.7, 43.8,
692     * 0., -64.6, -24.2, 6.2, 24., 14.8, -25.4,
693     * -5.8, 0.0, 11.9, -21.5, 8.5, -21.5, 15.5,
694     * 8.9, -14.9, -2.1, 0.0, -19.7, 13.4, 12.5,
695     * -6.2, -8.4, 8.4, 3.8, -8.2, 4.8, 0.0,
696     * 1.7, 0.0, 4.0, 4.9, -5.9, -1.2, -2.9,
697     * 0.2, -2.2, -7.4, 0.0, 0.1, 1.3, -0.9,
698     * -2.6, 0.9, -0.7, -2.8, -0.9, -1.2, -1.9,
699     * -0.9, 0.0, -0.4, 0.3, 2.5, -2.6, 0.7,
700     * 0.3, 0.0, 0.0, 0.3, -0.9, -0.4, 0.8,
701     * 0.0, -0.9, 0.2, 1.8, -0.4, -1.0, -0.1,
702     * 0.7, 0.3, 0.6, 0.3, -0.2, -0.5, -0.9/
703     *
704    
705     DATA G05/0.,-29556.8, -1671.8, -2340.5, 3047., 1656.9, 1335.7,
706     * -2305.3, 1246.8, 674.4, 919.8, 798.2, 211.5, -379.5,
707     * 100.2, -227.6, 354.4, 208.8, -136.6, -168.3, -14.1,
708     * 72.9, 69.6, 76.6, -151.1, -15.0, 14.7, -86.4,
709     * 79.8, -74.4, -1.4, 38.6, 12.3, 9.4, 5.5,
710     * 2.0, 24.8, 7.7, -11.4, -6.8, -18.0, 10.0,
711     * 9.4, -11.4, -5.0, 5.6, 9.8, 3.6, -7.0,
712     * 5.0, -10.8, -1.3, 8.7, -6.7, -9.2, -2.2,
713     * -6.3, 1.6, -2.5, -0.1, 3.0, 0.3, 2.1,
714     * 3.9, -0.1, -2.2, 2.9, -1.6, -1.7, 1.5,
715     * -0.2, 0.2, -0.7, 0.5, 1.8, 0.1, 1.0,
716     * 4.1, -2.2, -0.3, 0.3, 0.9, -0.4, 1.0,
717     * -0.4, 0.5, -0.3, -0.4, 0.0, -0.4, 0.0,
718     * -0.2, -0.9, 0.3, 0.3, -0.4, 1.2, -0.4,
719     * 0.7, -0.3, 0.4, -0.1, 0.4, -0.1, -0.3/
720    
721     DATA H05/0., 0.0, 5080.0, 0.0, -2594.9, -516.7, 0.0,
722     * -200.4, 269.3, -524.5, 0.0, 281.4, -225.8, 145.7,
723     * -304.7, 0.0, 42.7, 179.8, -123.0, -19.5, 103.6,
724     * 0.0, -20.2, 54.7, 63.7, -63.4, 0.0, 50.3,
725     * 0.0, -61.4, -22.5, 6.9, 25.4, 10.9, -26.4,
726     * -4.8, 0.0, 11.2, -21.0, 9.7, -19.8, 16.1,
727     * 7.7, -12.8, -0.1, 0.0, -20.1, 12.9, 12.7,
728     * -6.7, -8.1, 8.1, 2.9, -7.9, 5.9, 0.0,
729     * 2.4, 0.2, 4.4, 4.7, -6.5, -1.0, -3.4,
730     * -0.9, -2.3, -8.0, 0.0, 0.3, 1.4, -0.7,
731     * -2.4, 0.9, -0.6, -2.7, -1.0, -1.5, -2.0,
732     * -1.4, 0.0, -0.5, 0.3, 2.3, -2.7, 0.6,
733     * 0.4, 0.0, 0.0, 0.3, -0.8, -0.4, 1.0,
734     * 0.0, -0.7, 0.3, 1.7, -0.5, -1.0, 0.0,
735     * 0.7, 0.2, 0.6, 0.4, -0.2, -0.5, -1.0/
736    
737     DATA DG05/0.0, 8.8, 10.8, -15.0, -6.9, -1.0, -0.3,
738     * -3.1, -0.9, -6.8, -2.5, 2.8, -7.1, 5.9,
739     * -3.2, -2.6, 0.4, -3.0, -1.2, 0.2, -0.6,
740     * -0.8, 0.2, -0.2, 2.1, -2.1, -0.4, 1.3,
741     * -0.4, 0.0, -0.2, 1.1, 0.6, 0.4, -0.5,
742     * 0.9, -0.2, 0.2, -0.2, 0.2, -0.2, 0.2,
743     * 0.5, -0.7, 0.5/
744    
745     DATA DH05/0.0, 0.0, -21.3, 0.0, -23.3, -14.0, 0.0,
746     * 5.4, -6.5, -2.0, 0.0, 2.0, 1.8, 5.6,
747     * 0.0, 0.0, 0.1, 1.8, 2.0, 4.5, -1.0,
748     * 0.0, -0.4, -1.9, -0.4, -0.4, -0.2, 0.9,
749     * 0.0, 0.8, 0.4, 0.1, 0.2, -0.9, -0.3,
750     * 0.3, 0.0, -0.2, 0.2, 0.2, 0.4, 0.2,
751     * -0.3, 0.5, 0.4/
752     C
753     C
754     IY=IYEAR
755     C
756     C WE ARE RESTRICTED BY THE INTERVAL 1965-2010, FOR WHICH THE IGRF COEFFICIENTS
757     c ARE KNOWN; IF IYEAR IS OUTSIDE THIS INTERVAL, THEN THE SUBROUTINE USES THE
758     C NEAREST LIMITING VALUE AND PRINTS A WARNING:
759     C
760     IF(IY.LT.1965) THEN
761     IY=1965
762     WRITE (*,10) IYEAR,IY
763     ENDIF
764    
765     IF(IY.GT.2010) THEN
766     IY=2010
767     WRITE (*,10) IYEAR,IY
768     ENDIF
769    
770     C
771     C CALCULATE THE ARRAY REC, CONTAINING COEFFICIENTS FOR THE RECURSION RELATIONS,
772     C USED IN THE IGRF SUBROUTINE FOR CALCULATING THE ASSOCIATE LEGENDRE POLYNOMIALS
773     C AND THEIR DERIVATIVES:
774     c
775     DO 20 N=1,14
776     N2=2*N-1
777     N2=N2*(N2-2)
778     DO 20 M=1,N
779     MN=N*(N-1)/2+M
780     20 REC(MN)=FLOAT((N-M)*(N+M-2))/FLOAT(N2)
781     C
782     IF (IY.LT.1970) GOTO 50 !INTERPOLATE BETWEEN 1965 - 1970
783     IF (IY.LT.1975) GOTO 60 !INTERPOLATE BETWEEN 1970 - 1975
784     IF (IY.LT.1980) GOTO 70 !INTERPOLATE BETWEEN 1975 - 1980
785     IF (IY.LT.1985) GOTO 80 !INTERPOLATE BETWEEN 1980 - 1985
786     IF (IY.LT.1990) GOTO 90 !INTERPOLATE BETWEEN 1985 - 1990
787     IF (IY.LT.1995) GOTO 100 !INTERPOLATE BETWEEN 1990 - 1995
788     IF (IY.LT.2000) GOTO 110 !INTERPOLATE BETWEEN 1995 - 2000
789     IF (IY.LT.2005) GOTO 120 !INTERPOLATE BETWEEN 2000 - 2005
790     C
791     C EXTRAPOLATE BEYOND 2005:
792     C
793    
794     DT=FLOAT(IY)+FLOAT(IDAY-1)/365.25-2005.
795     DO 40 N=1,105
796     G(N)=G05(N)
797     H(N)=H05(N)
798     IF (N.GT.45) GOTO 40
799     G(N)=G(N)+DG05(N)*DT
800     H(N)=H(N)+DH05(N)*DT
801     40 CONTINUE
802     GOTO 300
803     C
804     C INTERPOLATE BETWEEEN 1965 - 1970:
805     C
806     50 F2=(FLOAT(IY)+FLOAT(IDAY-1)/365.25-1965)/5.
807     F1=1.-F2
808     DO 55 N=1,66
809     G(N)=G65(N)*F1+G70(N)*F2
810     55 H(N)=H65(N)*F1+H70(N)*F2
811     GOTO 300
812     C
813     C INTERPOLATE BETWEEN 1970 - 1975:
814     C
815     60 F2=(FLOAT(IY)+FLOAT(IDAY-1)/365.25-1970)/5.
816     F1=1.-F2
817     DO 65 N=1,66
818     G(N)=G70(N)*F1+G75(N)*F2
819     65 H(N)=H70(N)*F1+H75(N)*F2
820     GOTO 300
821     C
822     C INTERPOLATE BETWEEN 1975 - 1980:
823     C
824     70 F2=(FLOAT(IY)+FLOAT(IDAY-1)/365.25-1975)/5.
825     F1=1.-F2
826     DO 75 N=1,66
827     G(N)=G75(N)*F1+G80(N)*F2
828     75 H(N)=H75(N)*F1+H80(N)*F2
829     GOTO 300
830     C
831     C INTERPOLATE BETWEEN 1980 - 1985:
832     C
833     80 F2=(FLOAT(IY)+FLOAT(IDAY-1)/365.25-1980)/5.
834     F1=1.-F2
835     DO 85 N=1,66
836     G(N)=G80(N)*F1+G85(N)*F2
837     85 H(N)=H80(N)*F1+H85(N)*F2
838     GOTO 300
839     C
840     C INTERPOLATE BETWEEN 1985 - 1990:
841     C
842     90 F2=(FLOAT(IY)+FLOAT(IDAY-1)/365.25-1985)/5.
843     F1=1.-F2
844     DO 95 N=1,66
845     G(N)=G85(N)*F1+G90(N)*F2
846     95 H(N)=H85(N)*F1+H90(N)*F2
847     GOTO 300
848     C
849     C INTERPOLATE BETWEEN 1990 - 1995:
850     C
851     100 F2=(FLOAT(IY)+FLOAT(IDAY-1)/365.25-1990)/5.
852     F1=1.-F2
853     DO 105 N=1,66
854     G(N)=G90(N)*F1+G95(N)*F2
855     105 H(N)=H90(N)*F1+H95(N)*F2
856     GOTO 300
857     C
858     C INTERPOLATE BETWEEN 1995 - 2000:
859     C
860     110 F2=(FLOAT(IY)+FLOAT(IDAY-1)/365.25-1995)/5.
861     F1=1.-F2
862     DO 115 N=1,105 ! THE 2000 COEFFICIENTS (G00) GO THROUGH THE ORDER 13, NOT 10
863     G(N)=G95(N)*F1+G00(N)*F2
864     115 H(N)=H95(N)*F1+H00(N)*F2
865     GOTO 300
866     C
867     C INTERPOLATE BETWEEN 2000 - 2005:
868     C
869     120 F2=(FLOAT(IY)+FLOAT(IDAY-1)/365.25-2000)/5.
870     F1=1.-F2
871     DO 125 N=1,105
872     G(N)=G00(N)*F1+G05(N)*F2
873     125 H(N)=H00(N)*F1+H05(N)*F2
874     GOTO 300
875     C
876     C COEFFICIENTS FOR A GIVEN YEAR HAVE BEEN CALCULATED; NOW MULTIPLY
877     C THEM BY SCHMIDT NORMALIZATION FACTORS:
878     C
879     300 S=1.
880     DO 130 N=2,14
881     MN=N*(N-1)/2+1
882     S=S*FLOAT(2*N-3)/FLOAT(N-1)
883     G(MN)=G(MN)*S
884     H(MN)=H(MN)*S
885     P=S
886     DO 130 M=2,N
887     AA=1.
888     IF (M.EQ.2) AA=2.
889     P=P*SQRT(AA*FLOAT(N-M+1)/FLOAT(N+M-2))
890     MNN=MN+M-1
891     G(MNN)=G(MNN)*P
892     130 H(MNN)=H(MNN)*P
893    
894     G10=-G(2)
895     G11= G(3)
896     H11= H(3)
897     C
898     C NOW CALCULATE THE COMPONENTS OF THE UNIT VECTOR EzMAG IN GEO COORD.SYSTEM:
899     C SIN(TETA0)*COS(LAMBDA0), SIN(TETA0)*SIN(LAMBDA0), AND COS(TETA0)
900     C ST0 * CL0 ST0 * SL0 CT0
901     C
902     SQ=G11**2+H11**2
903     SQQ=SQRT(SQ)
904     SQR=SQRT(G10**2+SQ)
905     SL0=-H11/SQQ
906     CL0=-G11/SQQ
907     ST0=SQQ/SQR
908     CT0=G10/SQR
909     STCL=ST0*CL0
910     STSL=ST0*SL0
911     CTSL=CT0*SL0
912     CTCL=CT0*CL0
913     C
914     CALL SUN (IY,IDAY,IHOUR,MIN,ISEC,GST,SLONG,SRASN,SDEC)
915     C
916     C S1,S2, AND S3 ARE THE COMPONENTS OF THE UNIT VECTOR EXGSM=EXGSE IN THE
917     C SYSTEM GEI POINTING FROM THE EARTH'S CENTER TO THE SUN:
918     C
919     S1=COS(SRASN)*COS(SDEC)
920     S2=SIN(SRASN)*COS(SDEC)
921     S3=SIN(SDEC)
922     CGST=COS(GST)
923     SGST=SIN(GST)
924     C
925     C DIP1, DIP2, AND DIP3 ARE THE COMPONENTS OF THE UNIT VECTOR EZSM=EZMAG
926     C IN THE SYSTEM GEI:
927     C
928     DIP1=STCL*CGST-STSL*SGST
929     DIP2=STCL*SGST+STSL*CGST
930     DIP3=CT0
931     C
932     C NOW CALCULATE THE COMPONENTS OF THE UNIT VECTOR EYGSM IN THE SYSTEM GEI
933     C BY TAKING THE VECTOR PRODUCT D x S AND NORMALIZING IT TO UNIT LENGTH:
934     C
935     Y1=DIP2*S3-DIP3*S2
936     Y2=DIP3*S1-DIP1*S3
937     Y3=DIP1*S2-DIP2*S1
938     Y=SQRT(Y1*Y1+Y2*Y2+Y3*Y3)
939     Y1=Y1/Y
940     Y2=Y2/Y
941     Y3=Y3/Y
942     C
943     C THEN IN THE GEI SYSTEM THE UNIT VECTOR Z = EZGSM = EXGSM x EYGSM = S x Y
944     C HAS THE COMPONENTS:
945     C
946     Z1=S2*Y3-S3*Y2
947     Z2=S3*Y1-S1*Y3
948     Z3=S1*Y2-S2*Y1
949     C
950     C THE VECTOR EZGSE (HERE DZ) IN GEI HAS THE COMPONENTS (0,-SIN(DELTA),
951     C COS(DELTA)) = (0.,-0.397823,0.917462); HERE DELTA = 23.44214 DEG FOR
952     C THE EPOCH 1978 (SEE THE BOOK BY GUREVICH OR OTHER ASTRONOMICAL HANDBOOKS).
953     C HERE THE MOST ACCURATE TIME-DEPENDENT FORMULA IS USED:
954     C
955     DJ=FLOAT(365*(IY-1900)+(IY-1901)/4 +IDAY)
956     * -0.5+FLOAT(IHOUR*3600+MIN*60+ISEC)/86400.
957     T=DJ/36525.
958     OBLIQ=(23.45229-0.0130125*T)/57.2957795
959     DZ1=0.
960     DZ2=-SIN(OBLIQ)
961     DZ3=COS(OBLIQ)
962     C
963     C THEN THE UNIT VECTOR EYGSE IN GEI SYSTEM IS THE VECTOR PRODUCT DZ x S :
964     C
965     DY1=DZ2*S3-DZ3*S2
966     DY2=DZ3*S1-DZ1*S3
967     DY3=DZ1*S2-DZ2*S1
968     C
969     C THE ELEMENTS OF THE MATRIX GSE TO GSM ARE THE SCALAR PRODUCTS:
970     C CHI=EM22=(EYGSM,EYGSE), SHI=EM23=(EYGSM,EZGSE), EM32=(EZGSM,EYGSE)=-EM23,
971     C AND EM33=(EZGSM,EZGSE)=EM22
972     C
973     CHI=Y1*DY1+Y2*DY2+Y3*DY3
974     SHI=Y1*DZ1+Y2*DZ2+Y3*DZ3
975     HI=ASIN(SHI)
976     C
977     C TILT ANGLE: PSI=ARCSIN(DIP,EXGSM)
978     C
979     SPS=DIP1*S1+DIP2*S2+DIP3*S3
980     CPS=SQRT(1.-SPS**2)
981     PSI=ASIN(SPS)
982     C
983     C THE ELEMENTS OF THE MATRIX MAG TO SM ARE THE SCALAR PRODUCTS:
984     C CFI=GM22=(EYSM,EYMAG), SFI=GM23=(EYSM,EXMAG); THEY CAN BE DERIVED AS FOLLOWS:
985     C
986     C IN GEO THE VECTORS EXMAG AND EYMAG HAVE THE COMPONENTS (CT0*CL0,CT0*SL0,-ST0)
987     C AND (-SL0,CL0,0), RESPECTIVELY. HENCE, IN GEI THE COMPONENTS ARE:
988     C EXMAG: CT0*CL0*COS(GST)-CT0*SL0*SIN(GST)
989     C CT0*CL0*SIN(GST)+CT0*SL0*COS(GST)
990     C -ST0
991     C EYMAG: -SL0*COS(GST)-CL0*SIN(GST)
992     C -SL0*SIN(GST)+CL0*COS(GST)
993     C 0
994     C THE COMPONENTS OF EYSM IN GEI WERE FOUND ABOVE AS Y1, Y2, AND Y3;
995     C NOW WE ONLY HAVE TO COMBINE THE QUANTITIES INTO SCALAR PRODUCTS:
996     C
997     EXMAGX=CT0*(CL0*CGST-SL0*SGST)
998     EXMAGY=CT0*(CL0*SGST+SL0*CGST)
999     EXMAGZ=-ST0
1000     EYMAGX=-(SL0*CGST+CL0*SGST)
1001     EYMAGY=-(SL0*SGST-CL0*CGST)
1002     CFI=Y1*EYMAGX+Y2*EYMAGY
1003     SFI=Y1*EXMAGX+Y2*EXMAGY+Y3*EXMAGZ
1004     C
1005     XMUT=(ATAN2(SFI,CFI)+3.1415926536)*3.8197186342
1006     C
1007     C THE ELEMENTS OF THE MATRIX GEO TO GSM ARE THE SCALAR PRODUCTS:
1008     C
1009     C A11=(EXGEO,EXGSM), A12=(EYGEO,EXGSM), A13=(EZGEO,EXGSM),
1010     C A21=(EXGEO,EYGSM), A22=(EYGEO,EYGSM), A23=(EZGEO,EYGSM),
1011     C A31=(EXGEO,EZGSM), A32=(EYGEO,EZGSM), A33=(EZGEO,EZGSM),
1012     C
1013     C ALL THE UNIT VECTORS IN BRACKETS ARE ALREADY DEFINED IN GEI:
1014     C
1015     C EXGEO=(CGST,SGST,0), EYGEO=(-SGST,CGST,0), EZGEO=(0,0,1)
1016     C EXGSM=(S1,S2,S3), EYGSM=(Y1,Y2,Y3), EZGSM=(Z1,Z2,Z3)
1017     C AND THEREFORE:
1018     C
1019     A11=S1*CGST+S2*SGST
1020     A12=-S1*SGST+S2*CGST
1021     A13=S3
1022     A21=Y1*CGST+Y2*SGST
1023     A22=-Y1*SGST+Y2*CGST
1024     A23=Y3
1025     A31=Z1*CGST+Z2*SGST
1026     A32=-Z1*SGST+Z2*CGST
1027     A33=Z3
1028     C
1029     10 FORMAT(//1X,
1030     *'**** RECALC WARNS: YEAR IS OUT OF INTERVAL 1965-2010: IYEAR=',I4,
1031     * /,6X,'CALCULATIONS WILL BE DONE FOR IYEAR=',I4,/)
1032     RETURN
1033     END
1034     c
1035     c====================================================================
1036     C
1037     SUBROUTINE GEOMAG (XGEO,YGEO,ZGEO,XMAG,YMAG,ZMAG,J)
1038     C
1039     C CONVERTS GEOGRAPHIC (GEO) TO DIPOLE (MAG) COORDINATES OR VICA VERSA.
1040     C
1041     C J>0 J<0
1042     C-----INPUT: J,XGEO,YGEO,ZGEO J,XMAG,YMAG,ZMAG
1043     C-----OUTPUT: XMAG,YMAG,ZMAG XGEO,YGEO,ZGEO
1044     C
1045     C
1046     C ATTENTION: SUBROUTINE RECALC MUST BE INVOKED BEFORE GEOMAG IN TWO CASES:
1047     C /A/ BEFORE THE FIRST TRANSFORMATION OF COORDINATES
1048     C /B/ IF THE VALUES OF IYEAR AND/OR IDAY HAVE BEEN CHANGED
1049     C
1050     C
1051     C LAST MOFIFICATION: MARCH 30, 2003 (INVOCATION OF RECALC INSIDE THIS S/R WAS REMOVED)
1052     C
1053     C AUTHOR: N. A. TSYGANENKO
1054     C
1055     COMMON /GEOPACK1/ ST0,CT0,SL0,CL0,CTCL,STCL,CTSL,STSL,AB(19),BB(8)
1056    
1057     IF(J.GT.0) THEN
1058     XMAG=XGEO*CTCL+YGEO*CTSL-ZGEO*ST0
1059     YMAG=YGEO*CL0-XGEO*SL0
1060     ZMAG=XGEO*STCL+YGEO*STSL+ZGEO*CT0
1061     ELSE
1062     XGEO=XMAG*CTCL-YMAG*SL0+ZMAG*STCL
1063     YGEO=XMAG*CTSL+YMAG*CL0+ZMAG*STSL
1064     ZGEO=ZMAG*CT0-XMAG*ST0
1065     ENDIF
1066    
1067     RETURN
1068     END
1069     c
1070     c=========================================================================================
1071     c
1072     SUBROUTINE GEIGEO (XGEI,YGEI,ZGEI,XGEO,YGEO,ZGEO,J)
1073     C
1074     C CONVERTS EQUATORIAL INERTIAL (GEI) TO GEOGRAPHICAL (GEO) COORDS
1075     C OR VICA VERSA.
1076     C J>0 J<0
1077     C----INPUT: J,XGEI,YGEI,ZGEI J,XGEO,YGEO,ZGEO
1078     C----OUTPUT: XGEO,YGEO,ZGEO XGEI,YGEI,ZGEI
1079     C
1080     C ATTENTION: SUBROUTINE RECALC MUST BE INVOKED BEFORE GEIGEO IN TWO CASES:
1081     C /A/ BEFORE THE FIRST TRANSFORMATION OF COORDINATES
1082     C /B/ IF THE CURRENT VALUES OF IYEAR,IDAY,IHOUR,MIN,ISEC HAVE BEEN CHANGED
1083     C
1084     C LAST MODIFICATION: MARCH 31, 2003
1085    
1086     C AUTHOR: N. A. TSYGANENKO
1087     C
1088     COMMON /GEOPACK1/ A(27),CGST,SGST,B(6)
1089     C
1090     IF(J.GT.0) THEN
1091     XGEO=XGEI*CGST+YGEI*SGST
1092     YGEO=YGEI*CGST-XGEI*SGST
1093     ZGEO=ZGEI
1094     ELSE
1095     XGEI=XGEO*CGST-YGEO*SGST
1096     YGEI=YGEO*CGST+XGEO*SGST
1097     ZGEI=ZGEO
1098     ENDIF
1099    
1100     RETURN
1101     END
1102     C
1103     C=======================================================================================
1104     C
1105     SUBROUTINE MAGSM (XMAG,YMAG,ZMAG,XSM,YSM,ZSM,J)
1106     C
1107     C CONVERTS DIPOLE (MAG) TO SOLAR MAGNETIC (SM) COORDINATES OR VICA VERSA
1108     C
1109     C J>0 J<0
1110     C----INPUT: J,XMAG,YMAG,ZMAG J,XSM,YSM,ZSM
1111     C----OUTPUT: XSM,YSM,ZSM XMAG,YMAG,ZMAG
1112     C
1113     C ATTENTION: SUBROUTINE RECALC MUST BE INVOKED BEFORE MAGSM IN TWO CASES:
1114     C /A/ BEFORE THE FIRST TRANSFORMATION OF COORDINATES
1115     C /B/ IF THE VALUES OF IYEAR,IDAY,IHOUR,MIN,ISEC HAVE BEEN CHANGED
1116     C
1117     C LAST MODIFICATION: MARCH 31, 2003
1118     C
1119     C AUTHOR: N. A. TSYGANENKO
1120     C
1121     COMMON /GEOPACK1/ A(8),SFI,CFI,B(7),AB(10),BA(8)
1122     C
1123     IF (J.GT.0) THEN
1124     XSM=XMAG*CFI-YMAG*SFI
1125     YSM=XMAG*SFI+YMAG*CFI
1126     ZSM=ZMAG
1127     ELSE
1128     XMAG=XSM*CFI+YSM*SFI
1129     YMAG=YSM*CFI-XSM*SFI
1130     ZMAG=ZSM
1131     ENDIF
1132    
1133     RETURN
1134     END
1135     C
1136     C=======================================================================================
1137     C
1138     SUBROUTINE GSMGSE (XGSM,YGSM,ZGSM,XGSE,YGSE,ZGSE,J)
1139     C
1140     C CONVERTS GEOCENTRIC SOLAR MAGNETOSPHERIC (GSM) COORDS TO SOLAR ECLIPTIC (GSE) ONES
1141     C OR VICA VERSA.
1142     C J>0 J<0
1143     C-----INPUT: J,XGSM,YGSM,ZGSM J,XGSE,YGSE,ZGSE
1144     C----OUTPUT: XGSE,YGSE,ZGSE XGSM,YGSM,ZGSM
1145     C
1146     C ATTENTION: SUBROUTINE RECALC MUST BE INVOKED BEFORE GSMGSE IN TWO CASES:
1147     C /A/ BEFORE THE FIRST TRANSFORMATION OF COORDINATES
1148     C /B/ IF THE VALUES OF IYEAR,IDAY,IHOUR,MIN,ISEC HAVE BEEN CHANGED
1149     C
1150     C LAST MODIFICATION: MARCH 31, 2003
1151     C
1152     C AUTHOR: N. A. TSYGANENKO
1153     C
1154     COMMON /GEOPACK1/ A(12),SHI,CHI,AB(13),BA(8)
1155     C
1156     IF (J.GT.0) THEN
1157     XGSE=XGSM
1158     YGSE=YGSM*CHI-ZGSM*SHI
1159     ZGSE=YGSM*SHI+ZGSM*CHI
1160     ELSE
1161     XGSM=XGSE
1162     YGSM=YGSE*CHI+ZGSE*SHI
1163     ZGSM=ZGSE*CHI-YGSE*SHI
1164     ENDIF
1165    
1166     RETURN
1167     END
1168     C
1169     C=====================================================================================
1170     C
1171     SUBROUTINE SMGSM (XSM,YSM,ZSM,XGSM,YGSM,ZGSM,J)
1172     C
1173     C CONVERTS SOLAR MAGNETIC (SM) TO GEOCENTRIC SOLAR MAGNETOSPHERIC
1174     C (GSM) COORDINATES OR VICA VERSA.
1175     C J>0 J<0
1176     C-----INPUT: J,XSM,YSM,ZSM J,XGSM,YGSM,ZGSM
1177     C----OUTPUT: XGSM,YGSM,ZGSM XSM,YSM,ZSM
1178     C
1179     C ATTENTION: SUBROUTINE RECALC MUST BE INVOKED BEFORE SMGSM IN TWO CASES:
1180     C /A/ BEFORE THE FIRST TRANSFORMATION OF COORDINATES
1181     C /B/ IF THE VALUES OF IYEAR,IDAY,IHOUR,MIN,ISEC HAVE BEEN CHANGED
1182     C
1183     C LAST MODIFICATION: MARCH 31, 2003
1184     C
1185     C AUTHOR: N. A. TSYGANENKO
1186     C
1187     COMMON /GEOPACK1/ A(10),SPS,CPS,B(15),AB(8)
1188    
1189     IF (J.GT.0) THEN
1190     XGSM=XSM*CPS+ZSM*SPS
1191     YGSM=YSM
1192     ZGSM=ZSM*CPS-XSM*SPS
1193     ELSE
1194     XSM=XGSM*CPS-ZGSM*SPS
1195     YSM=YGSM
1196     ZSM=XGSM*SPS+ZGSM*CPS
1197     ENDIF
1198    
1199     RETURN
1200     END
1201     C
1202     C==========================================================================================
1203     C
1204     SUBROUTINE GEOGSM (XGEO,YGEO,ZGEO,XGSM,YGSM,ZGSM,J)
1205     C
1206     C CONVERTS GEOGRAPHIC (GEO) TO GEOCENTRIC SOLAR MAGNETOSPHERIC (GSM) COORDINATES
1207     C OR VICA VERSA.
1208     C
1209     C J>0 J<0
1210     C----- INPUT: J,XGEO,YGEO,ZGEO J,XGSM,YGSM,ZGSM
1211     C---- OUTPUT: XGSM,YGSM,ZGSM XGEO,YGEO,ZGEO
1212     C
1213     C ATTENTION: SUBROUTINE RECALC MUST BE INVOKED BEFORE GEOGSM IN TWO CASES:
1214     C /A/ BEFORE THE FIRST TRANSFORMATION OF COORDINATES
1215     C /B/ IF THE VALUES OF IYEAR,IDAY,IHOUR,MIN,ISEC HAVE BEEN CHANGED
1216     C
1217     C LAST MODIFICATION: MARCH 31, 2003
1218     C
1219     C AUTHOR: N. A. TSYGANENKO
1220     C
1221     COMMON /GEOPACK1/AA(17),A11,A21,A31,A12,A22,A32,A13,A23,A33,D,B(8)
1222     C
1223     IF (J.GT.0) THEN
1224     XGSM=A11*XGEO+A12*YGEO+A13*ZGEO
1225     YGSM=A21*XGEO+A22*YGEO+A23*ZGEO
1226     ZGSM=A31*XGEO+A32*YGEO+A33*ZGEO
1227     ELSE
1228     XGEO=A11*XGSM+A21*YGSM+A31*ZGSM
1229     YGEO=A12*XGSM+A22*YGSM+A32*ZGSM
1230     ZGEO=A13*XGSM+A23*YGSM+A33*ZGSM
1231     ENDIF
1232    
1233     RETURN
1234     END
1235     C
1236     C=====================================================================================
1237     C
1238     SUBROUTINE RHAND (X,Y,Z,R1,R2,R3,IOPT,PARMOD,EXNAME,INNAME)
1239     C
1240     C CALCULATES THE COMPONENTS OF THE RIGHT HAND SIDE VECTOR IN THE GEOMAGNETIC FIELD
1241     C LINE EQUATION (a subsidiary subroutine for the subroutine STEP)
1242     C
1243     C LAST MODIFICATION: MARCH 31, 2003
1244     C
1245     C AUTHOR: N. A. TSYGANENKO
1246     C
1247     DIMENSION PARMOD(10)
1248     C
1249     C EXNAME AND INNAME ARE NAMES OF SUBROUTINES FOR THE EXTERNAL AND INTERNAL
1250     C PARTS OF THE TOTAL FIELD
1251     C
1252     COMMON /GEOPACK1/ A(15),PSI,AA(10),DS3,BB(8)
1253    
1254     CALL EXNAME (IOPT,PARMOD,PSI,X,Y,Z,BXGSM,BYGSM,BZGSM)
1255     CALL INNAME (X,Y,Z,HXGSM,HYGSM,HZGSM)
1256    
1257     BX=BXGSM+HXGSM
1258     BY=BYGSM+HYGSM
1259     BZ=BZGSM+HZGSM
1260     B=DS3/SQRT(BX**2+BY**2+BZ**2)
1261     R1=BX*B
1262     R2=BY*B
1263     R3=BZ*B
1264     RETURN
1265     END
1266     C
1267     C===================================================================================
1268     C
1269     SUBROUTINE STEP (X,Y,Z,DS,ERRIN,IOPT,PARMOD,EXNAME,INNAME)
1270     C
1271     C RE-CALCULATES {X,Y,Z}, MAKING A STEP ALONG A FIELD LINE.
1272     C DS IS THE STEP SIZE, ERRIN IS PERMISSIBLE ERROR VALUE, IOPT SPECIFIES THE EXTERNAL
1273     C MODEL VERSION, THE ARRAY PARMOD CONTAINS INPUT PARAMETERS FOR THAT MODEL
1274     C EXNAME IS THE NAME OF THE EXTERNAL FIELD SUBROUTINE
1275     C INNAME IS THE NAME OF THE INTERNAL FIELD SUBROUTINE (EITHER DIP OR IGRF)
1276     C
1277     C ALL THE PARAMETERS ARE INPUT ONES; OUTPUT IS THE RENEWED TRIPLET X,Y,Z
1278     C
1279     C LAST MODIFICATION: MARCH 31, 2003
1280     C
1281     C AUTHOR: N. A. TSYGANENKO
1282     C
1283     DIMENSION PARMOD(10)
1284     COMMON /GEOPACK1/ A(26),DS3,B(8)
1285     EXTERNAL EXNAME,INNAME
1286    
1287     1 DS3=-DS/3.
1288     c (nico) I add this to avoid a seg fault
1289     WRITE(100,*)
1290     CALL RHAND (X,Y,Z,R11,R12,R13,IOPT,PARMOD,EXNAME,INNAME)
1291     CALL RHAND (X+R11,Y+R12,Z+R13,R21,R22,R23,IOPT,PARMOD,EXNAME,
1292     * INNAME)
1293     CALL RHAND (X+.5*(R11+R21),Y+.5*(R12+R22),Z+.5*
1294     *(R13+R23),R31,R32,R33,IOPT,PARMOD,EXNAME,INNAME)
1295     CALL RHAND (X+.375*(R11+3.*R31),Y+.375*(R12+3.*R32
1296     *),Z+.375*(R13+3.*R33),R41,R42,R43,IOPT,PARMOD,EXNAME,INNAME)
1297     CALL RHAND (X+1.5*(R11-3.*R31+4.*R41),Y+1.5*(R12-
1298     *3.*R32+4.*R42),Z+1.5*(R13-3.*R33+4.*R43),
1299     *R51,R52,R53,IOPT,PARMOD,EXNAME,INNAME)
1300     ERRCUR=ABS(R11-4.5*R31+4.*R41-.5*R51)+ABS(R12-4.5*R32+4.*R42-.5*
1301     *R52)+ABS(R13-4.5*R33+4.*R43-.5*R53)
1302     IF (ERRCUR.LT.ERRIN) GOTO 2
1303     DS=DS*.5
1304     GOTO 1
1305     2 X=X+.5*(R11+4.*R41+R51)
1306     Y=Y+.5*(R12+4.*R42+R52)
1307     Z=Z+.5*(R13+4.*R43+R53)
1308     IF(ERRCUR.LT.ERRIN*.04.AND.ABS(DS).LT.1.33) DS=DS*1.5
1309     RETURN
1310     END
1311     C
1312     C==============================================================================
1313     C
1314     SUBROUTINE TRACE (XI,YI,ZI,DIR,RLIM,R0,IOPT,PARMOD,EXNAME,INNAME,
1315     *XF,YF,ZF,XX,YY,ZZ,L)
1316     C
1317     C TRACES A FIELD LINE FROM AN ARBITRARY POINT OF SPACE TO THE EARTH'S
1318     C SURFACE OR TO A MODEL LIMITING BOUNDARY.
1319     C
1320     C THE HIGHEST ORDER OF SPHERICAL HARMONICS IN THE MAIN FIELD EXPANSION USED
1321     C IN THE MAPPING IS CALCULATED AUTOMATICALLY. IF INNAME=IGRF_GSM, THEN AN IGRF MODEL
1322     C FIELD WILL BE USED, AND IF INNAME=DIP, A PURE DIPOLE FIELD WILL BE USED.
1323    
1324     C IN ANY CASE, BEFORE CALLING TRACE, ONE SHOULD INVOKE RECALC, TO CALCULATE CORRECT
1325     C VALUES OF THE IGRF COEFFICIENTS AND ALL QUANTITIES NEEDED FOR TRANSFORMATIONS
1326     C BETWEEN COORDINATE SYSTEMS INVOLVED IN THIS CALCULATIONS.
1327     C
1328     C ALTERNATIVELY, THE SUBROUTINE RECALC CAN BE INVOKED WITH THE DESIRED VALUES OF
1329     C IYEAR AND IDAY (TO SPECIFY THE DIPOLE MOMENT), WHILE THE VALUES OF THE DIPOLE
1330     C TILT ANGLE PSI (IN RADIANS) AND ITS SINE (SPS) AND COSINE (CPS) CAN BE EXPLICITLY
1331     C SPECIFIED AND FORWARDED TO THE COMMON BLOCK GEOPACK1 (11th, 12th, AND 16th ELEMENTS, RESP.)
1332     C
1333     C------------- INPUT PARAMETERS:
1334     C
1335     C XI,YI,ZI - GSM COORDS OF INITIAL POINT (IN EARTH RADII, 1 RE = 6371.2 km),
1336     C
1337     C DIR - SIGN OF THE TRACING DIRECTION: IF DIR=1.0 THEN WE MOVE ANTIPARALLEL TO THE
1338     C FIELD VECTOR (E.G. FROM NORTHERN TO SOUTHERN CONJUGATE POINT),
1339     C AND IF DIR=-1.0 THEN THE TRACING GOES IN THE OPPOSITE DIRECTION.
1340     C
1341     C R0 - RADIUS OF A SPHERE (IN RE) FOR WHICH THE FIELD LINE ENDPOINT COORDINATES
1342     C XF,YF,ZF SHOULD BE CALCULATED.
1343     C
1344     C RLIM - UPPER LIMIT OF THE GEOCENTRIC DISTANCE, WHERE THE TRACING IS TERMINATED.
1345     C
1346     C IOPT - A MODEL INDEX; CAN BE USED FOR SPECIFYING AN OPTION OF THE EXTERNAL FIELD
1347     C MODEL (E.G., INTERVAL OF THE KP-INDEX). ALTERNATIVELY, ONE CAN USE THE ARRAY
1348     C PARMOD FOR THAT PURPOSE (SEE BELOW); IN THAT CASE IOPT IS JUST A DUMMY PARAMETER.
1349     C
1350     C PARMOD - A 10-ELEMENT ARRAY CONTAINING MODEL PARAMETERS, NEEDED FOR A UNIQUE
1351     C SPECIFICATION OF THE EXTERNAL FIELD. THE CONCRETE MEANING OF THE COMPONENTS
1352     C OF PARMOD DEPENDS ON A SPECIFIC VERSION OF THE EXTERNAL FIELD MODEL.
1353     C
1354     C EXNAME - NAME OF A SUBROUTINE PROVIDING COMPONENTS OF THE EXTERNAL MAGNETIC FIELD
1355     C (E.G., T96_01).
1356     C INNAME - NAME OF A SUBROUTINE PROVIDING COMPONENTS OF THE INTERNAL MAGNETIC FIELD
1357     C (EITHER DIP OR IGRF_GSM).
1358     C
1359     C-------------- OUTPUT PARAMETERS:
1360     C
1361     C XF,YF,ZF - GSM COORDS OF THE LAST CALCULATED POINT OF A FIELD LINE
1362     C XX,YY,ZZ - ARRAYS, CONTAINING COORDS OF FIELD LINE POINTS. HERE THEIR MAXIMAL LENGTH WAS
1363     C ASSUMED EQUAL TO 999.
1364     C L - ACTUAL NUMBER OF THE CALCULATED FIELD LINE POINTS. IF L EXCEEDS 999, TRACING
1365     C TERMINATES, AND A WARNING IS DISPLAYED.
1366     C
1367     C
1368     C LAST MODIFICATION: MARCH 31, 2003.
1369     C
1370     C AUTHOR: N. A. TSYGANENKO
1371     C
1372     DIMENSION XX(1000),YY(1000),ZZ(1000), PARMOD(10)
1373     COMMON /GEOPACK1/ AA(26),DD,BB(8)
1374     EXTERNAL EXNAME,INNAME
1375     C
1376     ERR=0.0001
1377     L=0
1378     DS=0.5*DIR
1379     X=XI
1380     Y=YI
1381     Z=ZI
1382     DD=DIR
1383     AL=0.
1384     c
1385     c here we call RHAND just to find out the sign of the radial component of the field
1386     c vector, and to determine the initial direction of the tracing (i.e., either away
1387     c or towards Earth):
1388     c
1389     WRITE(100,*)
1390     CALL RHAND (X,Y,Z,R1,R2,R3,IOPT,PARMOD,EXNAME,INNAME)
1391     AD=0.01
1392     IF (X*R1+Y*R2+Z*R3.LT.0.) AD=-0.01
1393     C
1394     c |AD|=0.01 and its sign follows the rule:
1395     c (1) if DIR=1 (tracing antiparallel to B vector) then the sign of AD is the same as of Br
1396     c (2) if DIR=-1 (tracing parallel to B vector) then the sign of AD is opposite to that of Br
1397     c AD is defined in order to initialize the value of RR (radial distance at previous step):
1398    
1399     RR=SQRT(X**2+Y**2+Z**2)+AD
1400     1 L=L+1
1401     IF(L.GT.999) GOTO 7
1402     XX(L)=X
1403     YY(L)=Y
1404     ZZ(L)=Z
1405     RYZ=Y**2+Z**2
1406     R2=X**2+RYZ
1407     R=SQRT(R2)
1408    
1409     c check if the line hit the outer tracing boundary; if yes, then terminate
1410     c the tracing (label 8):
1411    
1412     IF (R.GT.RLIM.OR.RYZ.GT.1600.D0.OR.X.GT.20.D0) GOTO 8
1413     c
1414     c check whether or not the inner tracing boundary was crossed from outside,
1415     c if yes, then calculate the footpoint position by interpolation (go to label 6):
1416     c
1417     IF (R.LT.R0.AND.RR.GT.R) GOTO 6
1418    
1419     c check if (i) we are moving outward, or (ii) we are still sufficiently
1420     c far from Earth (beyond R=5Re); if yes, proceed further:
1421     c
1422     IF (R.GE.RR.OR.R.GT.5.) GOTO 5
1423    
1424     c now we moved closer inward (between R=3 and R=5); go to 3 and begin logging
1425     c previous values of X,Y,Z, to be used in the interpolation (after having
1426     c crossed the inner tracing boundary):
1427    
1428     IF (R.GE.3.) GOTO 3
1429     c
1430     c we entered inside the sphere R=3: to avoid too large steps (and hence inaccurate
1431     c interpolated position of the footpoint), enforce the progressively smaller
1432     c stepsize values as we approach the inner boundary R=R0:
1433     c
1434     FC=0.2
1435     IF(R-R0.LT.0.05) FC=0.05
1436     AL=FC*(R-R0+0.2)
1437     DS=DIR*AL
1438     GOTO 4
1439     3 DS=DIR
1440     4 XR=X
1441     YR=Y
1442     ZR=Z
1443     5 RR=R
1444     CALL STEP (X,Y,Z,DS,ERR,IOPT,PARMOD,EXNAME,INNAME)
1445     GOTO 1
1446     c
1447     c find the footpoint position by interpolating between the current and previous
1448     c field line points:
1449     c
1450     6 R1=(R0-R)/(RR-R)
1451     X=X-(X-XR)*R1
1452     Y=Y-(Y-YR)*R1
1453     Z=Z-(Z-ZR)*R1
1454     GOTO 8
1455     7 WRITE (*,10)
1456     L=999
1457     8 XF=X
1458     YF=Y
1459     ZF=Z
1460     RETURN
1461     10 FORMAT(//,1X,'**** COMPUTATIONS IN THE SUBROUTINE TRACE ARE',
1462     *' TERMINATED: THE CURRENT NUMBER OF POINTS EXCEEDED 1000 ****'//)
1463     END
1464     c
1465     C====================================================================================
1466     C
1467     SUBROUTINE SHUETAL_MGNP(XN_PD,VEL,BZIMF,XGSM,YGSM,ZGSM,
1468     * XMGNP,YMGNP,ZMGNP,DIST,ID)
1469     C
1470     C FOR ANY POINT OF SPACE WITH COORDINATES (XGSM,YGSM,ZGSM) AND SPECIFIED CONDITIONS
1471     C IN THE INCOMING SOLAR WIND, THIS SUBROUTINE:
1472     C
1473     C (1) DETERMINES IF THE POINT (XGSM,YGSM,ZGSM) LIES INSIDE OR OUTSIDE THE
1474     C MODEL MAGNETOPAUSE OF SHUE ET AL. (JGR-A, V.103, P. 17691, 1998).
1475     C
1476     C (2) CALCULATES THE GSM POSITION OF A POINT {XMGNP,YMGNP,ZMGNP}, LYING AT THE MODEL
1477     C MAGNETOPAUSE AND ASYMPTOTICALLY TENDING TO THE NEAREST BOUNDARY POINT WITH
1478     C RESPECT TO THE OBSERVATION POINT {XGSM,YGSM,ZGSM}, AS IT APPROACHES THE MAGNETO-
1479     C PAUSE.
1480     C
1481     C INPUT: XN_PD - EITHER SOLAR WIND PROTON NUMBER DENSITY (PER C.C.) (IF VEL>0)
1482     C OR THE SOLAR WIND RAM PRESSURE IN NANOPASCALS (IF VEL<0)
1483     C BZIMF - IMF BZ IN NANOTESLAS
1484     C
1485     C VEL - EITHER SOLAR WIND VELOCITY (KM/SEC)
1486     C OR ANY NEGATIVE NUMBER, WHICH INDICATES THAT XN_PD STANDS
1487     C FOR THE SOLAR WIND PRESSURE, RATHER THAN FOR THE DENSITY
1488     C
1489     C XGSM,YGSM,ZGSM - GSM POSITION OF THE OBSERVATION POINT IN EARTH RADII
1490     C
1491     C OUTPUT: XMGNP,YMGNP,ZMGNP - GSM POSITION OF THE BOUNDARY POINT
1492     C DIST - DISTANCE (IN RE) BETWEEN THE OBSERVATION POINT (XGSM,YGSM,ZGSM)
1493     C AND THE MODEL NAGNETOPAUSE
1494     C ID - POSITION FLAG: ID=+1 (-1) MEANS THAT THE OBSERVATION POINT
1495     C LIES INSIDE (OUTSIDE) OF THE MODEL MAGNETOPAUSE, RESPECTIVELY.
1496     C
1497     C OTHER SUBROUTINES USED: T96_MGNP
1498     C
1499     c AUTHOR: N.A. TSYGANENKO,
1500     C DATE: APRIL 4, 2003.
1501     C
1502     IF (VEL.LT.0.) THEN
1503     PD=XN_PD
1504     ELSE
1505     PD=1.94E-6*XN_PD*VEL**2 ! PD IS THE SOLAR WIND DYNAMIC PRESSURE (IN nPa)
1506     ENDIF
1507    
1508     c
1509     c DEFINE THE ANGLE PHI, MEASURED DUSKWARD FROM THE NOON-MIDNIGHT MERIDIAN PLANE;
1510     C IF THE OBSERVATION POINT LIES ON THE X AXIS, THE ANGLE PHI CANNOT BE UNIQUELY
1511     C DEFINED, AND WE SET IT AT ZERO:
1512     c
1513     IF (YGSM.NE.0..OR.ZGSM.NE.0.) THEN
1514     PHI=ATAN2(YGSM,ZGSM)
1515     ELSE
1516     PHI=0.
1517     ENDIF
1518     C
1519     C FIRST, FIND OUT IF THE OBSERVATION POINT LIES INSIDE THE SHUE ET AL BDRY
1520     C AND SET THE VALUE OF THE ID FLAG:
1521     C
1522     ID=-1
1523     R0=(10.22+1.29*TANH(0.184*(BZIMF+8.14)))*PD**(-.15151515)
1524     ALPHA=(0.58-0.007*BZIMF)*(1.+0.024*ALOG(PD))
1525     R=SQRT(XGSM**2+YGSM**2+ZGSM**2)
1526     RM=R0*(2./(1.+XGSM/R))**ALPHA
1527     IF (R.LE.RM) ID=+1
1528     C
1529     C NOW, FIND THE CORRESPONDING T96 MAGNETOPAUSE POSITION, TO BE USED AS
1530     C A STARTING APPROXIMATION IN THE SEARCH OF A CORRESPONDING SHUE ET AL.
1531     C BOUNDARY POINT:
1532     C
1533     CALL T96_MGNP (PD,-1.,XGSM,YGSM,ZGSM,XMT96,YMT96,ZMT96,DIST,ID96)
1534     C
1535     RHO2=YMT96**2+ZMT96**2
1536     R=SQRT(RHO2+XMT96**2)
1537     ST=SQRT(RHO2)/R
1538     CT=XMT96/R
1539     C
1540     C NOW, USE NEWTON'S ITERATIVE METHOD TO FIND THE NEAREST POINT AT THE
1541     C SHUE ET AL.'S BOUNDARY:
1542     C
1543     NIT=0
1544    
1545     1 T=ATAN2(ST,CT)
1546     RM=R0*(2./(1.+CT))**ALPHA
1547    
1548     F=R-RM
1549     GRADF_R=1.
1550     GRADF_T=-ALPHA/R*RM*ST/(1.+CT)
1551     GRADF=SQRT(GRADF_R**2+GRADF_T**2)
1552    
1553     DR=-F/GRADF**2
1554     DT= DR/R*GRADF_T
1555    
1556     R=R+DR
1557     T=T+DT
1558     ST=SIN(T)
1559     CT=COS(T)
1560    
1561     DS=SQRT(DR**2+(R*DT)**2)
1562    
1563     NIT=NIT+1
1564    
1565     IF (NIT.GT.1000) THEN
1566     PRINT *,
1567     *' BOUNDARY POINT COULD NOT BE FOUND; ITERATIONS DO NOT CONVERGE'
1568     ENDIF
1569    
1570     IF (DS.GT.1.E-4) GOTO 1
1571    
1572     XMGNP=R*COS(T)
1573     RHO= R*SIN(T)
1574    
1575     YMGNP=RHO*SIN(PHI)
1576     ZMGNP=RHO*COS(PHI)
1577    
1578     DIST=SQRT((XGSM-XMGNP)**2+(YGSM-YMGNP)**2+(ZGSM-ZMGNP)**2)
1579    
1580     RETURN
1581     END
1582     C
1583     C=======================================================================================
1584     C
1585     SUBROUTINE T96_MGNP (XN_PD,VEL,XGSM,YGSM,ZGSM,XMGNP,YMGNP,ZMGNP,
1586     * DIST,ID)
1587     C
1588     C FOR ANY POINT OF SPACE WITH GIVEN COORDINATES (XGSM,YGSM,ZGSM), THIS SUBROUTINE DEFINES
1589     C THE POSITION OF A POINT (XMGNP,YMGNP,ZMGNP) AT THE T96 MODEL MAGNETOPAUSE, HAVING THE
1590     C SAME VALUE OF THE ELLIPSOIDAL TAU-COORDINATE, AND THE DISTANCE BETWEEN THEM. THIS IS
1591     C NOT THE SHORTEST DISTANCE D_MIN TO THE BOUNDARY, BUT DIST ASYMPTOTICALLY TENDS TO D_MIN,
1592     C AS THE OBSERVATION POINT GETS CLOSER TO THE MAGNETOPAUSE.
1593     C
1594     C INPUT: XN_PD - EITHER SOLAR WIND PROTON NUMBER DENSITY (PER C.C.) (IF VEL>0)
1595     C OR THE SOLAR WIND RAM PRESSURE IN NANOPASCALS (IF VEL<0)
1596     C VEL - EITHER SOLAR WIND VELOCITY (KM/SEC)
1597     C OR ANY NEGATIVE NUMBER, WHICH INDICATES THAT XN_PD STANDS
1598     C FOR THE SOLAR WIND PRESSURE, RATHER THAN FOR THE DENSITY
1599     C
1600     C XGSM,YGSM,ZGSM - COORDINATES OF THE OBSERVATION POINT IN EARTH RADII
1601     C
1602     C OUTPUT: XMGNP,YMGNP,ZMGNP - GSM POSITION OF THE BOUNDARY POINT, HAVING THE SAME
1603     C VALUE OF TAU-COORDINATE AS THE OBSERVATION POINT (XGSM,YGSM,ZGSM)
1604     C DIST - THE DISTANCE BETWEEN THE TWO POINTS, IN RE,
1605     C ID - POSITION FLAG; ID=+1 (-1) MEANS THAT THE POINT (XGSM,YGSM,ZGSM)
1606     C LIES INSIDE (OUTSIDE) THE MODEL MAGNETOPAUSE, RESPECTIVELY.
1607     C
1608     C THE PRESSURE-DEPENDENT MAGNETOPAUSE IS THAT USED IN THE T96_01 MODEL
1609     C (TSYGANENKO, JGR, V.100, P.5599, 1995; ESA SP-389, P.181, OCT. 1996)
1610     C
1611     c AUTHOR: N.A. TSYGANENKO
1612     C DATE: AUG.1, 1995, REVISED APRIL 3, 2003.
1613     C
1614     C
1615     C DEFINE SOLAR WIND DYNAMIC PRESSURE (NANOPASCALS, ASSUMING 4% OF ALPHA-PARTICLES),
1616     C IF NOT EXPLICITLY SPECIFIED IN THE INPUT:
1617    
1618     IF (VEL.LT.0.) THEN
1619     PD=XN_PD
1620     ELSE
1621     PD=1.94E-6*XN_PD*VEL**2
1622     C
1623     ENDIF
1624     C
1625     C RATIO OF PD TO THE AVERAGE PRESSURE, ASSUMED EQUAL TO 2 nPa:
1626    
1627     RAT=PD/2.0
1628     RAT16=RAT**0.14
1629    
1630     C (THE POWER INDEX 0.14 IN THE SCALING FACTOR IS THE BEST-FIT VALUE OBTAINED FROM DATA
1631     C AND USED IN THE T96_01 VERSION)
1632     C
1633     C VALUES OF THE MAGNETOPAUSE PARAMETERS FOR PD = 2 nPa:
1634     C
1635     A0=70.
1636     S00=1.08
1637     X00=5.48
1638     C
1639     C VALUES OF THE MAGNETOPAUSE PARAMETERS, SCALED BY THE ACTUAL PRESSURE:
1640     C
1641     A=A0/RAT16
1642     S0=S00
1643     X0=X00/RAT16
1644     XM=X0-A
1645     C
1646     C (XM IS THE X-COORDINATE OF THE "SEAM" BETWEEN THE ELLIPSOID AND THE CYLINDER)
1647     C
1648     C (FOR DETAILS ON THE ELLIPSOIDAL COORDINATES, SEE THE PAPER:
1649     C N.A.TSYGANENKO, SOLUTION OF CHAPMAN-FERRARO PROBLEM FOR AN
1650     C ELLIPSOIDAL MAGNETOPAUSE, PLANET.SPACE SCI., V.37, P.1037, 1989).
1651     C
1652     IF (YGSM.NE.0..OR.ZGSM.NE.0.) THEN
1653     PHI=ATAN2(YGSM,ZGSM)
1654     ELSE
1655     PHI=0.
1656     ENDIF
1657     C
1658     RHO=SQRT(YGSM**2+ZGSM**2)
1659     C
1660     IF (XGSM.LT.XM) THEN
1661     XMGNP=XGSM
1662     RHOMGNP=A*SQRT(S0**2-1)
1663     YMGNP=RHOMGNP*SIN(PHI)
1664     ZMGNP=RHOMGNP*COS(PHI)
1665     DIST=SQRT((XGSM-XMGNP)**2+(YGSM-YMGNP)**2+(ZGSM-ZMGNP)**2)
1666     IF (RHOMGNP.GT.RHO) ID=+1
1667     IF (RHOMGNP.LE.RHO) ID=-1
1668     RETURN
1669     ENDIF
1670     C
1671     XKSI=(XGSM-X0)/A+1.
1672     XDZT=RHO/A
1673     SQ1=SQRT((1.+XKSI)**2+XDZT**2)
1674     SQ2=SQRT((1.-XKSI)**2+XDZT**2)
1675     SIGMA=0.5*(SQ1+SQ2)
1676     TAU=0.5*(SQ1-SQ2)
1677     C
1678     C NOW CALCULATE (X,Y,Z) FOR THE CLOSEST POINT AT THE MAGNETOPAUSE
1679     C
1680     XMGNP=X0-A*(1.-S0*TAU)
1681     ARG=(S0**2-1.)*(1.-TAU**2)
1682     IF (ARG.LT.0.) ARG=0.
1683     RHOMGNP=A*SQRT(ARG)
1684     YMGNP=RHOMGNP*SIN(PHI)
1685     ZMGNP=RHOMGNP*COS(PHI)
1686     C
1687     C NOW CALCULATE THE DISTANCE BETWEEN THE POINTS {XGSM,YGSM,ZGSM} AND {XMGNP,YMGNP,ZMGNP}:
1688     C (IN GENERAL, THIS IS NOT THE SHORTEST DISTANCE D_MIN, BUT DIST ASYMPTOTICALLY TENDS
1689     C TO D_MIN, AS WE ARE GETTING CLOSER TO THE MAGNETOPAUSE):
1690     C
1691     DIST=SQRT((XGSM-XMGNP)**2+(YGSM-YMGNP)**2+(ZGSM-ZMGNP)**2)
1692     C
1693     IF (SIGMA.GT.S0) ID=-1 ! ID=-1 MEANS THAT THE POINT LIES OUTSIDE
1694     IF (SIGMA.LE.S0) ID=+1 ! ID=+1 MEANS THAT THE POINT LIES INSIDE
1695     C THE MAGNETOSPHERE
1696     RETURN
1697     END
1698     C
1699     C -----------------------------------------------------------------------------
1700     C Subroutine SETPSI added by PJ 15.12.2003, copied from geopack2003.f 20.5.2005
1701     C -----------------------------------------------------------------------------
1702     SUBROUTINE SETPSI(PS)
1703     REAL PS
1704     COMMON /GEOPACK1/ AAA(10),SPS,CPS,BBB(23)
1705     REAL AAA,SPS,CPS,BBB
1706     SPS=SIN(PS)
1707     CPS=COS(PS)
1708     RETURN
1709     END
1710     C ----------------------------------------
1711     C
1712     C===================================================================================
1713     C
1714     c</pre>

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