European Space Agency

Royal Belgian Institute for Aeronomy

uf424 - search the lowest B value

subroutine  uf424(mgp, pb, palt, mxnb, ifail)

Parameters:

• mgp [zpnt,out] :: Point with the lowest B value (geographic position, magnetic field vector,…)

• pb [real8,out] :: Value of the magnetic field intensity

• palt [real8,out] :: Altitude at mgp

• mxnb [zvec,out] :: Vector pointing to the binormal vector of the magnetic field line at mgp

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

Description

The subroutine uf424() searches for the point in the common block uc170 with the lowest magnetic field intensity. The index kgp of the common block is set to the point.

The point found by the subroutine uf424() corresponds generally to the location with the lowest magnetic field intensity along the field line. At this location the radius of curvature is re-evaluated by the help of two Runge-Kutta steps.

The subroutine also evaluates the vector mxnb proportional to the local drift vector of a particle bouncing between the two mirror points of the magnetic field line segment. The factor of proportionality depends mainly on the energy of the particle (…). The vector mxnb is parallel to the binormal vector of the field line, and is inversely proportional to the local magnetic field intensity and curvature radius.

Diagnostics

• -42401, need few place in the common block UC170

Common Blocks

• uc160 - general constants

• uc170 - temporary magnetic field line

Dependencies

Called by

• uf420 - trace a magnetic field line segment passing through a given position

Calls

• uf423 - Runge Kutta step

• uf425 - evaluate the curvature of the field lines

See also

• Lew, J. S. (1961), Drift rate in a dipole field, J. Geophys. Res., 66(9), 2681–2685, doi:10.1029/JZ066i009p02681.

Reported Bugs

None

Examples

None

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UNILIB/tags/v3.02