Cactus Code Thorn IllinoisGRMHD
Author(s)    : Zachariah B. Etienne
Note         : IllinoisGRMHD is based on the GRMHD code of the
               Illinois Numerical Relativity group, written by Matt Duez, Yuk 
               Tung Liu, and Branson Stephens (original version), and then 
               developed primarily by Zachariah Etienne, Yuk Tung Liu, 
               and Vasileios Paschalidis. 
Maintainer(s): Zachariah B. Etienne
License      : GPLv2 for HARM Conservative-to-Primitive solver (src/harm_*)
               GPLv2+ for all other code
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1. Purpose

IllinoisGRMHD solves the equations of General Relativistic 
MagnetoHydroDynamics (GRMHD) using a high-resolution shock capturing scheme.
It is a rewrite of the Illinois Numerical Relativity (ILNR) group's GRMHD 
code, and generates results that agree to roundoff error with that original
code. Its feature set coincides with the features of the ILNR group's 
recent code (ca. 2009--2014), which was used in their modeling of the
following systems:
1) Magnetized circumbinary disk accretion onto binary black holes
2) Magnetized black hole--neutron star mergers
3) Magnetized Bondi flow, Bondi-Hoyle-Littleton accretion
4) White dwarf--neutron star mergers

IllinoisGRMHD is particularly good at modeling GRMHD flows into black holes
without the need for excision. Its HARM-based conservative-to-primitive solver 
has also been modified to check the physicality of conservative variables 
prior to primitive inversion, and move them into the physical range if they 
become unphysical.

Currently IllinoisGRMHD consists of
1) the Piecewise Parabolic Method (PPM) for reconstruction, 
2) the Harten, Lax, van Leer (HLL/HLLE) approximate Riemann solver, and
3) a modified HARM Conservative-to-Primitive solver. 

IllinoisGRMHD evolves the vector potential A_{\mu} (on staggered grids) 
instead of the magnetic fields (B^i) directly, to guarantee that the 
magnetic fields will remain divergenceless even at AMR boundaries. On 
uniform resolution grids, this vector potential formulation produces 
results equivalent to those generated using the standard, staggered 
flux-CT scheme. This scheme is based on that of Del Zanna (2003, see
below OPTIONAL CITATION #1).

REQUIRED CITATIONS:

1) IllinoisGRMHD code announcement paper: 
Class. Quantum Grav. 32 (2015) 175009, (http://arxiv.org/abs/1501.07276)

"MORALLY OBLIGATED" CITATIONS:
1) HARM papers: 
    [a] Gammie, C. F., McKinney, J. C., \& Toth, G.\ 2003, 
        Astrophysical Journal, 589, 444.

    [b] Noble, S. C., Gammie, C. F., McKinney, J. C., \& Del Zanna, L. \ 2006, 
        Astrophysical Journal, 641, 626.

OPTIONAL CITATIONS:
1) Del Zanna, Bucciantini & Londrillo A&A 400, 397 (2003), Eq. (44)
