UM520

[ Name | Synopsis | Arguments | Description | Diagnostics | Common Blocks | Dependencies | See Also | Reported Bugs | Examples ]

Name

Subroutine UM520 - select an external magnetic field model

Synopsis

      REAL*8        amjd, param(10)
      INTEGER*4     kext, ifail, kunit
      CHARACTER*32  lbext
      
      UM520 (kext, amjd, param, lbext, kunit, ifail)

Arguments

kext: Index of the external magnetic field model (0 to 6) [in]
amjd: Modified Julian Day [in]
param: Set of parameters for the external magnetic field models [in]
lbext: Label of the external magnetic field model [out]
kunit: File unit for the summary table (see note of subroutine UT990) [in]
ifail: Error flag (see diagnostics) [out]

The subroutine UM520 initializes the selected field model as well as the position of the Sun and the GSM or SM coordinate transformation. The position of the Sun and the transformation are deduced from the geomagnetic field model (selected by subroutine UM510) and from the modified Julian Day specified by the argument amjd.

The Mead & Fairfield model (kext = 1) and most of Tsyganenko models (kext = 2, 3 and 4) depend on the planetary magnetic activity index K_p. The dynamic Olson & Pfitzer model (kext = 6) depends on the disturbance storm-time index D_st, the density of solar wind and the velocity of solar wind. The Tsyganenko 1996 model (kext = 7) depends on the solar wind pressure and the components y and z of the interplanetary magnetic field. The Ostapenko & Maltsev model (kext = 8) depends on the planetary magnetic activity index K_p, the disturbance storm-time index D_st, the dynamic pressure of the solar wind and the z component of the interplanetary magnetic field. These different parameters are specified to the subroutine UM520 by the way of the argument param. The correspondance between the different parameters and the indices of the argument param are given in the second table below. The last column of the table is used to indicated correspondances with old arguments of the subroutine (see history).

`kext`	External magnetic field model
0	None
1	Mead & Fairfield [1975]
2	Tsyganenko short [1987]
3	Tsyganenko long [1987]
4	Tsyganenko [1989c]
5	Olson & Pfitzer quiet [1977]
6	Olson & Pfitzer dynamic [1988]
7	Tsyganenko [1996]
8	Ostapenko & Maltsev [1997]

Note: Dr. Tsyganenko recommends not using the obsolete 1987 versions.

`param`	Description	Range	Default	Used by (`kext`)	Old argument
1	Planetary magnetic activity index K_p (see Note)	0 to 9	0	1, 2, 3, 4, 8	`fkp`
2	Disturbance storm-time index D_st (nT)	-600 to 50	-30	6, 7, 8	`dst`
3	Solar wind pressure (nP)	0.5 to 10	3	7, 8	-
4	Solar wind density (cm^-3)	1 to 100	25	6	`swd`
5	Solar wind velocity (km/s)	100 to 1200	300	6	`swv`
6	Interplanetary magnetic field X component (nT)	-50 to 50	6	-	-
7	Interplanetary magnetic field Y component (nT)	-50 to 50	0	7	-
8	Interplanetary magnetic field Z component (nT)	-50 to 50	0	7, 8	-
9	Standoff distance to the subsolar point (Re)	4 to 14	10	-	-
10	Reserved for future use	-	-	-	-

For each element of the argument param, when a value is set to -999, the corresponding default value is used instead (without modifying the argument param). The default value of the standoff distance is deduced from the solar wind velocity and density when they are provided. Anyway, a warning is written in the summary table when a parameter is out of range.

As result, the lbext argument contains a string with the label of the selected external magnetic field model and a summary table is written on the file specified by argument kunit. The summary table includes the values of the parameters that will be used by the external magnetic field model.

The subroutines UM522, UM523 and UM524 can be used to modify the time and date of the external magnetic field without modifying the model choice (kext) or field parameters (K_p, D_st,...), except for the Ostapenko & Maltsev [1997] model (kext=8) for which UM520 has to be called. Note that the coefficients of mext.trans (common block UC140) are expressed in the GSM coordinates with the Tsyganenko models (2, 3, 4 and 7) while the SM coordinates are used with the other models (1, 5 and 6).

Note

UM533

References

Olson, W.P., A model of the distributed magnetospheric currents, JGR 79 (1974) 3731-3738
Olson, W.P. and Pfitzer, K.A., Magnetospheric magnetic field modeling, Annual Scientific Report, AFOSR Contract No. F44620-75-C-0033 (1977)
Ostapenko, A.A., and Maltsev, Y.P., Relation of the magnetic field in the magnetosphere to the geomagnetic and solar wind activity, JGR 102 (1997) 17467-17473
Pfitzer, K.A., Olson, W.P. and Mogstad, T., A time dependent source driven magnetospheric magnetic field model, EOS 69 (1988) 426
Tsyganenko, N.A., Global quantitative models of the geomagnetic field in the cislunar magnetosphere for different disturbance levels, Planet.Space Sci. 35 (1987) 1347-1358
Tsyganenko, N.A., A magnetospheric magnetic field model with a wrapped tail current sheet, Planet.Space.Sci. 37 (1989) 5-20
Tsyganenko, N.A. and Stern, D.P., Modeling the global magnetic field the large-scale Birkeland current systems, J.Geophys.Res. 101 (1996) 27187-27198

History

kext

      UM520 (kext, amjd, dst, fkp, swd, swv, lbext, kunit, ifail)

dst

fkp

swd

swv

_st

param

In versions 1.07 to 1.12, the documentation did not include D_st as parameter of the Tsyganenko [1996] model and the subroutine UM520 did not print the value of D_st when this model was selected. Note that, nevertheless, the value of D_st was used during computations of the Tsyganenko [1996] model.

In versions 1.07 to 1.13, the value of K_p was not correctly passed to the subroutine UM533. The distance to the magnetopause was always evaluated with K_p set to zero.

In versions 2.00 and 2.01, due to an oversight, the model parameters were forced to the default values instead of the values passed in the argument param. This erroneous behaviour affects user applications using external magnetic field models: Mead & Fairfield [1975], Tsyganenko short [1987], Tsyganenko long [1987], Tsyganenko [1989a], Olson & Pfitzer dynamic [1988], Tsyganenko [1996] and Ostapenko & Maltsev [1997]. It does not affect applications that do not use an external field model (kext=0) or that use the Olson & Pfitzer quiet [1977] model (kext=5).

In version 2.02, the Tsyganenko [1989a] model (kext=4) has been replaced by the Tsyganenko [1989c] model.