The interaction of a magnetohydrodynamical shock with a filament
  We present 3D magnetohydrodynamic numerical simulations of the adiabatic
interaction of a shock with a dense, filamentary cloud. We investigate the
effects of various filament lengths and orientations on the interaction using
different orientations of the magnetic field, and vary the Mach number of the
shock, the density contrast of the filament, and the plasma beta, in order to
determine their effect on the evolution and lifetime of the filament. We find
that in a parallel magnetic field filaments have longer lifetimes if they are
orientated more 'broadside' to the shock front, and that an increase in the
density contrast hastens the destruction of the cloud, in terms of the modified
cloud-crushing time-scale, tcs. The combination of a mild shock and a
perpendicular or oblique field provides the best condition for extending the
life of the filament, with some filaments able to survive almost indefinitely
since they are cocooned by the magnetic field. A high value for the density
contrast does not initiate large turbulent instabilities in either the
perpendicular or oblique field cases but rather draws the filament out into
long tendrils which may eventually fragment. In addition, flux ropes are only
formed in parallel magnetic fields. The length of the filament is, however, not
as important for the evolution and destruction of a filament.
