UF420
[ Name  Synopsis  Arguments  Description  Diagnostics  Common Blocks  Dependencies  See Also  Reported Bugs  Examples ]
Name

Subroutine UF420  trace a magnetic field line segment passing through a given
position
Synopsis
INTEGER*4 nfbm, ifail REAL*8 fbm(nfbm), falt RECORD /zgeo/ mpos CALL UF420 (mpos, fbm, nfbm, falt, ifail)
Arguments

mpos
 The geographic position (GEO) through which the searched magnetic field line is passing [in]

fbm
 Boundary conditions on the magnetic field intensity [in]

nfbm
 Number of boundary conditions on the magnetic field intensity [in]

falt
 Boundary condition on the altitude [in]

ifail
 Error flag (see diagnostics) [out]
Description

The subroutine UF420 traces a magnetic field line segment passing through
the geographic position
mpos
. The magnetic field line
segment is limited by one of the following boundary conditions :
falt
to a value
lower than 500.
The different points along the field line segment are stored in the
common block UC170. It includes the points
corresponding to the boundary conditions, as well as, the points
corresponding to the magnetic field intensities fbm(2)
,
..., fbm(nfbm)
. Note that the intensities set in the array
fbm
has to be strictely decreasing : fbm(1)
>
fbm(2)
> fbm(nfbm)
.
History

From version 1.13 to version 2.00, the algorithm has been
improved for the case where the first boundary condition on the
magnetic field intensity is close to the minimum value
of the magnetic field intensity along the field line segment.
Diagnostics

42001, incorrect boundary conditions
42002 or 42004, strange behaviour of the field line near the altitude boundary condition
42003 or 42006, strange behaviour of B along the field line
42005, problem with the boundary condition on the altitude
42007, problem with the boundary conditions on B
42008 or 42010, find the minimum of B before any one of the boundary conditions
42009, too many points along the field line segment
42011, error in UF428 detected a posteriori
Common Blocks
Dependencies
Called by

UL220,
get information on a magnetic field line segment
UF410, search the geographic position of a magnetic field line
UF417, search the geographic position of a magnetic field line (new)
UF411, search a local magnetic equator
Calls

UF421,
initialize and close a field line segment
UF422, follow a field line until a boundary condition is reached
UF424, search the lowest B value
UF429, transpose a field line segment
See also

FAQ G.05 Which are the coordinates and units used ?
Reported Bugs

None
Examples

G.06 How to start using the UNILIB library ?