European Space Agency

Royal Belgian Institute for Aeronomy

uf411 - search a local magnetic equator

subroutine  uf411(glon, radius, rmin, rmax, gsclat, fbm, mpeq, ml, ifail)

Parameters:

• glon [real8,in] :: Equatorial longitude

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

• rmin [real8,in/out] :: Minimum radius

• rmax [real8,in/out] :: Maximum radius

• gsclat [real8,in] :: guessed equatorial co-latitude

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

• mpeq [zpnt,out] :: Equatorial location

• ml [zlbl,out] :: Magnetic field line segment descriptor

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

Description

The subroutine uf411() searches iteratively a local magnetic equator for a given longitude and a fixed range of geocentric radius. The local magnetic equator is identified as a point where a magnetic field line segment passing through the point has its minimum of the magnetic field intensity at this point. Note that this definition of a local magnetic equator depends on the value of the magnetic field intensity Bm at the mirror points chosen to trace the magnetic field line segment.

As input, the subroutine accepts the arguments glon, radius, rmin, rmax, gsclat and fbm. To find a local magnetic equator, the geocentric radius can be modified in the range [rmin, rmax] as well as that the equatorial co-latitude can be changed. Note that the solution is not unique. As output, the subroutine returns the arguments radius, rmin, rmax, mpeq and ml. The argument rmin (rmax) can be only increased (decreased, resp.) by subroutine uf411().

Diagnostics

• -41101, -41102, -41103, cannot find the minimum of B

• -41104, problem to trace a field line, too many points

• -41105, problem to evaluate the integral invariant

• -41106, problem to trace a field line

• -41107, too many iterations

• -41108, problem to trace a field line, RK integration

• -41110, problem to find the local magnetic equator

• -41111, -41112, -41113, -41114, computation aborted after 10 iterations

Common Blocks

• uc140 - magnetic field

• uc160 - general constants

• uc170 - temporary magnetic field line

• uc190 - control parameters, set 1

• uc192 - control parameters, set 2

Dependencies

Called by

• uf410 - search the geographic position of a magnetic field line

• uf417 - search the geographic position of a magnetic field line

Calls

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

• um530 - evaluate the magnetic field vector

• ul230 - evaluate the integral invariant coordinate I

• ul240 - evaluate the Hilton’s function

See also

None

Reported Bugs

• 26-Aug-97 (v1.05), Anomalously return of subroutine ud310() with error code -41108

Examples

None

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UNILIB/tags/v3.02