| Title: | Effects of Strong Magnetic Fields on Photoionised Clouds
|
| Authors: | Jonathan Mackey and Andrew J. Lim, 2012 |
| Abstract: | Simulations are presented of the photoionisation of three dense gas
clouds threaded by magnetic fields, showing the dynamical effects of
different initial magnetic field orientations and strengths. For
moderate magnetic field strengths the initial radiation-driven implosion
phase is not strongly affected by the field geometry, and the
photoevaporation flows are also similar. Over longer timescales, the
simulation with an initial field parallel to the radiation propagation
direction (parallel field) remains basically axisymmetric, whereas in
the simulation with a perpendicular initial field the pillar of neutral
gas fragments in a direction aligned with the magnetic field. For
stronger initial magnetic fields, the dynamics in all gas phases are
affected at all evolutionary times. In a simulation with a strong
initially perpendicular field, photoevaporated gas forms filaments of
dense ionised gas as it flows away from the ionisation front along field
lines. These filaments are potentially a useful diagnostic of magnetic
field strengths in H II regions because they are very bright in
recombination line emission. In the strong parallel field simulation the
ionised gas is constrained to flow back towards the radiation source,
shielding the dense clouds and weakening the ionisation front,
eventually transforming it to a recombination front. |
| ICHEC Project: | Numerical Studies of the Evolution of Structures in H II Regions. |
| Publication: | High Energy Density Physics, TBD, Proceeding of 9th International Conference on High Energy Density Laboratory Astrophysics, April 30-May 4, 2012, Tallahassee, Florida. |
| URL: | http://arxiv.org/abs/1210.5385v1 |
| Keywords: | Methods, Numerical, MHD, Radiative transfer, H ii Regions, ISM, Magnetic fields |
| Status: | Submitted |
