UD310

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

Name

Subroutine UD310 - trace a magnetic drift shell

Synopsis

      REAL*8    fbm0, flm0, falt
      INTEGER*4 knfl, ifail, ktyplus

      CALL UD310 (fbm0, flm0, falt, knfl, ktyplus, ifail)

Arguments

fbm0

Magnetic field intensity at mirror point B_m [in]

flm0

McIlwain's parameter L_m [in]

falt

Boundary condition on the altitude [in]

knfl

number of lines to be traced [in]

ktyplus

controlling parameter [in]

ifail

error flag (passed by dependents) [out]

Description

The subroutine UD310 traces a magnetic drift shell. The drift shell is defined as a set of magnetic field line segments where all the segments are characterized by the same shell parameter and the same mirror-point magnetic field intensity. The values of the shell parameter and magnetic field intensity are fixed by the arguments flm0 and fbm0, respectively. The argument knfl defines the number of field line segments to be traced. The algorithm of subroutine UD310 and its dependents is such that the points where the magnetic field intensity is minimum on each of the knfl segments are equally spaced in longitude.

The arguments falt and ktyplus are passed to the subroutines UF410 and UD319, respectively. As a result:

• when falt is greater than -500, the foot points of each magnetic field line segment are computed for the altitude defined by the value in km of falt. Otherwise the foot points are not computed;
• for each magnetic field line segment computed, the part of the segment transferred in the common blocks UC120 and UC130 is function of the value of ktyplus (see table below).



Value of ktyplus	Description
1	All the field line segments are completely transferred. When falt >-500, it includes the foot points and also the intermediate points on the field line situated below the mirror points and above the foot prints.
2	For each field line segment, only the points comprised between the mirror points are transferred. When falt >-500, the foot points of the segment are transferred but not the intermediate points between them and the mirror points.
3	The only points transferred from each field line segment are the mirror points, the point with the lowest magnetic field intensity and the foot points when falt >-500.

The option ktyplus=3 can be used when the only sought information is related to the mirror, equatorial or foot points. It cannot be used if all the points along the drift shell are needed, e.g. to evaluate drift shell averaged atmospheric density.

References

• Heynderickx, D., Kruglanski, M. and Lemaire, J.F., A new tool for calculating drift shell averaged atmospheric density, in Radiation belts: models and standards, edited by Heynderickx, D., Lemaire, J.F. and Baker, D.N. (1996) 173-178

Note

Since version 2.00, the subroutine UD317 has been introduced as an alternative to subroutine UD310. Although the algorithms of both subroutines are similar, the subroutine UD317 seems to be more efficient. FORTRAN programs using subroutine UD310 can be adapted by the insertion of the following lines:

C     to be included in the declaration part
C
      RECORD /zlbl/ mlab0
      REAL*8        altmin
C 
C     to replace the calling sequence
C        CALL UD310 (fbm0, flm0, falt, knfl, ktyplus, ifail)
C
      mlab0.lbmp = .TRUE.
      mlab0.llmi = .TRUE.
      mlab0.linv = .FALSE.
      mlab0.fbmp = fbm0
      mlab0.flmi = flm0
      CALL UD317 (mlab0, falt, ktyplus, altmin, ifail)

One should note that the argument knfl is ignored by subroutine UD317 which traces about 70 field line segments per drift shell. The output argument altmin of subroutine UD317 returns the altitude of the lowest mirror point of the drift shell.

Diagnostics

None

Common Blocks

None

Dependencies

Called by

None

Calls

UF410, search the geographic position of a magnetic field line
UD319, transfer a field line segment from common block UC170 to UC130

See also

UC110, magnetic drift shell description
UC120, magnetic field line description
UC130, set of magnetic field line segments
UD330, evaluate the third invariant

Reported Bugs

26-Aug-97 (v1.05), Anomalous return of subroutine UD310 with error code -41108

Examples

#3, evaluation of the third invariant
#4, search the point with the lowest altitude on a magnetic drift shell
T.04 Why are Roederer's L^* and McIlwain's L parameters different ?