[OpenMadrigal-developers] New web service for Madrigal - field line tracer

[William Rideout]

John Foster recently asked me for the ability from matlab to trace the field 
line from an arbitrary point in space down to a given altitude (in his case, the 
  altitude of a particular satellite.  As usual, I want all the real work to be 
done by Madrigal and exposed to matlab via a web service. However, my usual 
approach of defining a derived Madrigal parameter will not work in this case, 
since the altitude to trace to is not defined beforehand.

In order to solve this problem in as general a way as is reasonable, I planning 
to add a generic magnetic field line tracer web server.  This service will trace 
a magnetic field line from an arbitrary point in space and time to a number of 
user specified end points.

This web server will accept the following arguments:

     year, month, day, hour, min, sec (required)

     model = 'tsyganenko' or 'igrf' (required)

     xGSM, yGSM, zGSM or lat, lon, alt (starting point) (required)

     outputCoord = 'geodetic' or 'gsm' (required)

     stop = 'conjugate', 'north_alt', 'south_alt', 'apex' (required)
        Note: north_alt means move north until desired altitude reached.

     end_alt - (only required if stop = 'north_alt' or 'south_alt')

It will return either xGSM, yGSM, zGSM or lat, lon, alt depending on outputCoord 
specified, or NaN if trace failed.

More models and coordinate systems could be added if required.  Please let me 
know if you have any comments.

Bill

-- 
Bill Rideout
MIT Haystack Observatory
Email: brideout at haystack.mit.edu
Phone: 781 981-5624