European Space Agency

Royal Belgian Institute for Aeronomy

um522 - position of the Sun

subroutine  um522(amjd, kunit)

Parameters:

• amjd [real8,in] :: modified julian day

• kunit [integer4,in] :: file unit for the summary table (see note of ut990()).

Description

The subroutine um522() computes the Greenwich hour angle of equinox as well as the GEO cartesian direction of the Sun. The results are stored in the argument msun of the common block uc140. When kunit is greater than zero, a summary table is written by the subroutine. Commonly the calls to the subroutine um522() are followed by a call to the subroutine um523() or um524() to update the coordinate transformation used during the evaluation of the components of the external magnetic field. Note that subroutine um539() combines the features of subroutines um522(), um523() and um524() with the features of subroutine um530().

References

• Van Flandern, T.C., and Pulkkinen, K.F., Low precision formulae for planetary positions, Astroph. J. Suppl. 41 (1979) 391-411

Diagnostics

• The program is aborted when an error occurs on the output device

Common Blocks

• uc140 - magnetic field

• uc160 - general constants

Dependencies

Called by

• um520 - select an external magnetic field model

• um539 - evaluate the magnetic field

Calls

None

See also

None

Reported Bugs

None

Examples

• Ex #2. Evaluation of the (B-L) coordinates

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UNILIB/tags/v3.02