Ionisation in Turbulent Magnetic Molecular Clouds I. Effect on Density
  and Mass-to-Flux Ratio Structures
  Previous studies show that the physical structures and kinematics of a region
depend significantly on the ionisation fraction. In this paper, we extend our
previous studies of the effect of ionisation fractions on star formation to
clouds that include both non-ideal magnetohydrodynamics and turbulence. We aim
to quantify the importance of a treatment of the ionisation fraction in
turbulent magnetised media and investigate the effect of turbulence on shaping
the clouds and filaments before star formation sets in. In particular, we
investigate how the structure, mass and width of filamentary structures depend
on the amount of turbulence in ionised media and the initial mass-to-flux
ratio. We compare the resulting density and mass-to-flux ratio structures both
qualitatively and quantitatively via filament and core masses and filament
fitting techniques (Gaussian and Plummer profiles.) We find that even with
almost no turbulence, filamentary structure still exists. Comparison of
simulations show that for turbulent Mach numbers above 2, there is little
structural difference between the Step-Like (SL) and Cosmic Ray only (CR-only)
ionisation models, while below this threshold the ionisation structure
significantly affects the formation of filaments. Analysis of the mass within
cores and filaments show decrease in mass as the degree of turbulence
increases. Finally, observed filaments within the Taurus L1495/B213 complex are
best reproduced by models with supercritical mass-to-flux ratios and/or at
least mildly supersonic turbulence, however, our models show that sterile
fibres observed within Taurus may occur in highly ionised, subcritical
environments. Based on this, we suggest that regions with fertile fibres likely
indicate a trans- or supercritical mass-to-flux ratio within the region while
sterile fibres are likely subcritical and transient.
