Dynamics controlled by magnetic fields:
parallel astrophysical computations

I present the development history of and the obtained flexibility within the Versatile Advection Code [VAC, see http://www.phys.uu.nl/~toth], a software package for solving sets of - near - conservation laws in any dimensionality. Using a finite volume discretization on a static structured grid, the versatility resides in the choice of applications (Euler, Navier-Stokes, Magneto-Hydro-Dynamics), geometry, computer platform, shock-capturing spatial and temporal discretizations. For distributed memory execution, the VAC source code is automatically preprocessed to High Performance Fortran which results in fully scalable applications. In its most challenging configuration, the code is used for simulating magnetized plasma dynamics in astrophysically relevant, three-dimensional geometries. The magnetic field can severely complicate plasma flow behaviour both in shock-dominated and otherwise (un)steady regimes. We present examples of (i) `kinking' magnetic fluxtubes, related to emerging sunspots on the solar surface; (ii) Kelvin-Helmholtz unstable magnetized jet flows, present at all scales in our universe; and (iii) coronal mass ejections in the continuously expanding solar magnetic environment. All these simulations would benefit greatly from dynamically controlled grid adaptivity, a research topic we are currently investigating.