European Space Agency

European Space Agency

Royal Belgian Institute for Aeronomy

Royal Belgian Institute for Aeronomy

../_images/whiteSpace.png

ul220 - get information on a magnetic field line segment

subroutine  ul220(mpos, alpha, nfbm, fbm, flm, fkm, fsm, fbeq, fs, ifail)
Parameters:

  • mpos [zgeo,in] :: Geographic location (GEO)

  • alpha (nfbm) [real8,in] :: local pitch angles

  • nfbm [integer4,in] :: number of pitch angles

  • fbm (nfbm) [real8,out] :: Magnetic field intensity at the mirror points

  • flm (nfbm) [real8,out] :: McIlwain’s shell parameter

  • fkm (nfbm) [real8,out] :: Kaufman parameter K

  • fsm (nfbm) [real8,out] :: Arc length of the field line segment between the mirror points

  • fbeq [real8,out] :: Lowest magnetic field intensity along the field line

  • fs (nfbm) [real8,out] :: Arc length of the field line segment from the northern mirror point to mpos

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

Description

The subroutine ul220() computes magnetic coordinates such as Bm and L associated to a magnetic field line segment passing through the geographic position mpos. The subroutine accepts as input a list of local pitch angles (alpha). The values set in the argument alpha must be sorted by increasing order (from 0 to 90 degree). The magnetic field line passing through the position mpos is traced until all the mirror points are encountered. For each value of argument alpha, a pair of mirror points are determined and the corresponding arguments fbm, flm, fkm, fsm, fs are evaluated.

Note

Some errors may occur during the process for a subset of local pitch angles. As far as possible, the subroutine ul220() does not stop on these errors and continues the process for the other pitch angle values. As a trace of such an error, the corresponding value of argument flm is set to a negative value. The list of possible errors are given in the table below.

Value of flm

error diagnostic

-1

The magnetic field line reaches too high geomagnetic latitude (see diagnostic -53003)

-2

The magnetic field crosses the magnetopause (see diagnostic -53301)

-3

The reached magnetic field intensity is outside valid limits (see diagnostic -53002)

-4

Maximum number of steps along the magnetic field line has been reached (see diagnostic -42009)

-5

The magnetic field line goes too deep inside the Earth (see diagnostics -53001 and -53004)

-6

Out of allocated memory (see diagnostics -42301 and -42401)

-7

The magnetic field line pass through a local maximum

-8

An error occurred in the interpolation routine (see diagnostics -428** and -426**)

-9

An error occurred in the evaluation of I (see diagnostics -230** and -240**)

-10

Not documented

References

  • Heynderickx, D., Lemaire, J., and Daly, E.J., Historical review of the different procedures used to compute the L parameter, Aeronomica Acta A-Nb 380 (1994), J. Nuclear Tracks Radiat. Meas. (1995)

  • McIlwain, C.E., Coordinates for mapping the distribution of magnetically trapped particles, JGR 66 (1961) 3681-3691

  • Roederer, J.G., Dynamics of geomagnetically trapped radiation, Springer-Verlag (1970)

History

  • In version 2.02 in earlier, some L values are not evaluated when more than one local pitch angle is requested.

Diagnostics

  • -22001, Invalid value of alpha

  • -22002, Values of alpha are not increasing or invalid values

  • -22003, Do not find a pair of mirror points

  • -22004, Unable to trace correctly the field line segment

Common Blocks

Dependencies

Called by

None

Calls

See also

Reported Bugs

None

Examples

UNILIB/tags/v3.02