Dynamically dominant magnetic fields in the diffuse interstellar medium
  Observations show that magnetic fields in the interstellar medium (ISM) often
do not respond to increases in gas density as would be naively expected for a
frozen-in field. This may suggest that the magnetic field in the diffuse gas
becomes detached from dense clouds as they form. We have investigated this
possibility using theoretical estimates, a simple magneto-hydrodynamic model of
a flow without mass conservation and numerical simulations of a thermally
unstable flow. Our results show that significant magnetic flux can be shed from
dense clouds as they form in the diffuse ISM, leaving behind a magnetically
dominated diffuse gas.
