European Space Agency

European Space Agency

Royal Belgian Institute for Aeronomy

Royal Belgian Institute for Aeronomy

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uf417 - search the geographic position of a magnetic field line

subroutine  uf417(fim, fbm, glon, guess, mpos, falt, ifail)
Parameters:

  • fim [real8,in] :: Value of the integral invariant I

  • fbm [real8,in] :: Magnetic field intensity at the mirror points

  • glon [real8,in] :: Equatorial longitude

  • guess [real8,in/out] :: Equatorial radius

  • mpos [zgeo,out] :: Equatorial location

  • falt [real8,in] :: Boundary condition on the altitude

  • ifail [integer4,out] :: error flag (see Diagnostics)

Description

The subroutine uf417() searches iteratively a magnetic field line segment for which the integral invariant I, the magnetic field intensity Bm at the mirror points and the longitude of the point with the lowest magnetic field intensity are fixed. The values of I, Bm and longitude are passed through the arguments fim, fbm and glon, respectively. The functionality of subroutine uf417() is very similar to the one of subroutine uf410() which depends on the shell parameter L instead of I. The subroutine uf417() seems to be better suited for equatorial field line segment (I=0).

The argument guess can be used to guess the geocentric radius of the point with the lowest magnetic field intensity. As a result, the magnetic field line segment is returned in the common block uc170, the argument guess is set to the current geocentric radius and the argument mpos contains the geographic location of the local magnetic equator. Note that the argument falt can be used such that the subroutine traces the field line till the foot points.

History

  • The subroutines uf417() and ud317() do not exist in version 1.13 and earlier.

Diagnostics

  • -41701, field line segment not found, probably the value of Bm is less than B0

  • -41702, field line segment not found

  • -41703, too many iterations

  • -41704, field line segment found, but problem with the altitude boundary

  • -41705, invalid value of flm or fbm argument

  • -41706, field line segment found, but the field line is passing below the altitude boundary

Common Blocks

Dependencies

Called by

Calls

See also

None

Reported Bugs

None

Examples

None

UNILIB/tags/v3.02