The interaction of a magnetohydrodynamical shock with a filament

TL;DR

This study uses 3D magnetohydrodynamic simulations to explore how shock interactions with filamentary clouds depend on magnetic field orientation, filament properties, and shock parameters, revealing conditions that prolong filament survival.

Contribution

It provides new insights into the effects of magnetic field orientation and filament properties on cloud evolution during shock interactions, including filament longevity and flux rope formation.

Findings

Filaments survive longer in parallel magnetic fields when oriented broadside to shocks.

Increased density contrast accelerates filament destruction.

Perpendicular or oblique magnetic fields can nearly indefinitely cocoon filaments.

Abstract

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.