[OpenMadrigal-developers] Adding Tsyganenko model to Madrigal

[William Rideout]

John F,

I'm almost done incorporating the Tsyganenko model into Madrigal.  As always 
when incorporating Fortran, the biggest challenge is to get the code to handle 
error conditions correctly.

The Tsyganenko model basically draws the field line given various conditions. 
Because of your request for adding this feature to mapping GPS mapping, I have 
added the following four parameters to Madrigal:

1 & 2:

given a point in space and time, find the point where the corresponding field 
line crosses the GSM XY plane (that is, the magnetic dipole equatorial plane). 
The two returned values are:

TSYG_EQ_XGSM
TSYG_EQ_YGSM

3 & 4:

given a point in space and time, find the point where the corresponding field 
line crosses the GSE XY plane (that is, the ecliptic plane).  The two returned 
values are:

TSYG_EQ_XGSE
TSYG_EQ_YGSE

My question is - should I expose anything else?  I haven't exposed the apex 
coordinates, although TSYG_EQ_XGSM and TSYG_EQ_YGSM are close.  And if so, 
should they be returned as GSM or GSE?  Also, do I need to convert anything back 
to Geodetic coordinates?  I can also return footprints, conjugate points, etc.

Finally, a separate method in Tsyganenko's library does the following:

FOR ANY POINT OF SPACE WITH COORDINATES (XGSM,YGSM,ZGSM) AND SPECIFIED 
CONDITIONS IN THE INCOMING SOLAR WIND, THIS SUBROUTINE:

(1) DETERMINES IF THE POINT (XGSM,YGSM,ZGSM) LIES INSIDE OR OUTSIDE THE
       MODEL MAGNETOPAUSE OF SHUE ET AL. (JGR-A, V.103, P. 17691, 1998).

(2) CALCULATES THE GSM POSITION OF A POINT {XMGNP,YMGNP,ZMGNP}, LYING AT THE 
MODEL MAGNETOPAUSE AND ASYMPTOTICALLY TENDING TO THE NEAREST BOUNDARY POINT WITH
  RESPECT TO THE OBSERVATION POINT {XGSM,YGSM,ZGSM}, AS IT APPROACHES THE 
MAGNETO-PAUSE.

Let me know if anyone thinks this would be a helpful parameter for Madrigal to 
expose.

Bill

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