DISCO: A 3D Moving-Mesh Magnetohydrodynamics Code Designed for the Study
  of Astrophysical Disks
  This work presents the publicly available moving-mesh magnetohydrodynamics
code DISCO. DISCO is efficient and accurate at evolving orbital fluid motion in
two and three dimensions, especially at high Mach number. DISCO employs a
moving-mesh approach utilizing a dynamic cylindrical mesh that can shear
azimuthally to follow the orbital motion of the gas. The moving mesh removes
diffusive advection errors and allows for longer timesteps than a static grid.
Magnetohydrodynamics is implemented in DISCO using an HLLD Riemann solver and a
novel constrained transport scheme which is compatible with the mesh motion.
DISCO is tested against a wide variety of problems, which are designed to test
its stability, accuracy and scalability. In addition, several
magnetohydrodynamics tests are performed which demonstrate the accuracy and
stability of the new constrained transport approach, including two tests of the
magneto-rotational instability (MRI); one testing the linear growth rate and
the other following the instability into the fully turbulent regime.
