IDL Routines for Gauss's Separation Method in Cartesian Coordinates, v. 2026-08-27

IDL routines in this directory can be used to apply Gauss's Separation method to decompose a 2D, Cartesian array of the 3-component vector magnetic field measured on a plane, such as that in a solar photospheric vector magnetogram in the tangent-plane approximation, into:

(1) poloidal/toroidal components (a poloidal/toroidal decomposition, or PTD), to derive the horizontal field's toroidal component (sometimes called the field's rotational component), which is due to currents through the surface:  (Btorx, Btory)

(2) a Gaussian separation of the field's poloidal (or irrotational) part into components due to currents
(i) above the surface, Bgt ("greater than") and
(ii) below the surface, Blt ("less than") 

This approach for Gauss's separation method in Cartesian geometry was used by Welsch et al. (2026) in their paper, "The Photospheric Imprints of Coronal Currents: I. Magnetic Structure Near Polarity Inversion Lines," which has been submitted to The Astrophysical Journal (ApJ) and is being revised.

Some [optional] routines for testing the decomposition and for visualizing its output vector fields are also provided, in the file extra_visualization_routines_*.tar.

While documentation here is presently minimal, all codes are commented, and the README.txt file in this release contains more detailed info about this software. 

History:
 - Brian T. Welsch: created this terse description 2026 Jun 29

 - BTW: this version fixes a bug in gauss_decomp_from_bvec.pro that affected zero-padding added to non-square arrays; posted 2026 Aug 27

Feedback: If you find bugs, inaccurate or unclear comments,
      or just want to say hello, email welschb @ uwgb.edu
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